Document ban39Bk6dQEe75ekwRLakOKxD

of theories do not exist, there is an ever expanding pool c experimental investigations that leads us closer to the answers s i I! i :i i1 I ADDITIONAL REFERENCES 72. Ham, A.W., Histology, 6th Ed., J.B. Lippencatt Company, Philadelphia, PA (1969). 73. Bailey J.E., and D.F. OUis, Biochemical Fundamentals, 2nd Ed., McGraw-Hill Book Company New York NY (1986). 74. Aiba S., A.E. Humphrey, N.F. Mills, Biochemical Engineering, 2nd Ed., Academic Press Inc.. New York NY (1973). 75. Watson, J.D. and F.H.C. Crick, Nature, 171, 737-964 (1953). 76. Spencer, J.H., The Physics and Chemistry of DNA and RNA, W.B. Saunders Company, Philadelphia, PA ^1972^ 77. Singer, B. and Grunberger, Molecular Biology of Mutagens and Carcinogens, Plenum Press New York NY (1983). '' 78. Simic, M.G., L. Mossman, and A.C. Upton, Editors, Mechanisms of DNA Damage and Repair, Plenum Press New York, NY (1986). * 79. Hygaard, O.F., and M.G. Simic, Editors, Radioprotectors and Anticarcinogens, Plenum Press, New York, NY (1983). Free Radicals and Cancer. I. !I i ;i `H I i I ii I i! >i I !':ii i i I!! i! T . i. !-I ii i i! ii I 'i ii !I :i ii i ii: ,li U.1. / / / C-12 - :i.|- [ T- !+* HJH* 'p- _ I ll. I ILi : i H' I -sSa- !Si-!... I -!b -I 1-1*1 I li S. : r>l l It J. -.1 ifl , it * UStHHEl ii M i'1 mfmmi::: | i f-j ! r;| I i :' & } ;LL=iV iSr -iVMi -' : s jtyJ : !KI-.:j s ' I, in" 2 ! i *3 fi-Mii? 'Hi-rr Jgi-iic- ; ? pa I faU Ii - E -S S fi Bj . lib r;!-.:s -i/b ': = i.l*. i ih -Ini Iil~.r i.;' r1 i -r.t. .* '-I, :i.L' ft; * Ml IN J-i. Ellis!-a- W -ii i >13 t Site 4 Ll- : t -ir ;i t, *t:. o. .1 ti -I illUr1 r'* V.i Is ii mi;J>ri- ".1 >'r\ !! lll'l m lit C! : ! i,: I .. i II 'i\~ I A- ' I! m . i ;! I h:j !::Mi: '1J i M>: tl! l!f ":-l II il- ^ ill1 !i=r Si tda bl- h ^!j-11`-*\ iS`? s!i'j ? i31 i't!: :r.\- *1 :? r :i k* 1tu :i in i. i.l 2L IS -&,K t: @1 icd i;11 liiiVf. !j i jJ.: i.t i ; .jf 1 L? ' it.i* `i. t 3ii|Iftf I If y\ h I- ! I. I > it l l 7, ii-ui !. i ii\\ vl .lift ! I.IL - %J.-+ li^: l!!l r- H |r . I .ii |i g ilI fi 'wi 3 I ii I It* ! !I ill I r! s iStililjLfl! -4 PI wy ri i *> i i: l 1- ! -r ] ^ II h'l :;r .N/-M. i2M' fi11 :M^|I['J1 I -- if n i rtla j.-:5 ti i fi i r ij'is i!- 'ti? f: frlb. .ii ill l '' W:\ i V. u iI Ill r; | I ! ! ;!| i: ! i:i I ! i s11 i! I p; l. I! Ii i.i !jl !' l: , i i. i . !i| ! !.ii i I. I- ! I! i:: i ;i ll i' i l1 i I. ! i! I i. I i lijiiii!! :'j isis! I'1 i = l!i :|j j I >|! Ililil i'i! !' i!; ;l :::i! : ; '! * II II I.II; I! ' l| l! *5 :!,:! <ii >i |i:'| Ml! I j! i il i i!]-|l! :s i :ii I : .i .i i:i |-i,: . iJj' M I J The Texas Institute For Advancement of Chemical Technology Inc. Mail Stop 3125 Texas A&M University College Station, Texas 77843-3125 I , (409) 845-3372 I t \ , I- L I1 r. i I; r ' .J E t / ! Am i 1: j 5i :' I! i: i i! i . 'I i, i. I. !& ,l|. ,.E i i. I.: ;I i I i :i J:: l! 'I ;j- !I i :i VAB.0001023855 ! A r A BRIEF REVIEW OF CHEMICAL CARCINOGENESIS Advancement of chemical technology is the primary mission of the Texas Institute for Advancement of Chemical Technology. The purpose of this report is to advance technology through an informed public. 4 I I i i .1 Charles D. Holland, President Texas Institute for Advancement of Chemical Technology and Professor Emeritus of Chemical Engineering Texas A&M University Mail Stop 3125 College Station, Texas 77843 The Institute is a nonprofit, charitable organization. Special Report 1, 1989 . t r < ' i it :l i ! k i i i i r i : . ' * 0 t *! T m * VAB.0001023856 # ACKNOWLEDGMENTS This report is based on a vast volume of literature describing an untold number of years of experimentation. The following reviewers were of inestimable value to me in the evaluation and interpretation of the literature, and I am most grateful for their help. OUTSIDE REVIEWERS : Dr. M. E. Andersen, Senior Staff Scientist, Toxic Hazards Division, Harry G. Armstrong Aerospace Medical Research Laboratory, Wright-Patterson Air Force Base Dr. William F. Benedict, M.D., Professor of Biotechnology, Center of Biotechnology, Woodlands, TX Dr. Patricia A. Buffler, Professor of Epidemiology and Director of the Epidemiology Research Unit, Texas School of Public Health Dr. Philip Cole, M.D., DrPH, Professor and Chairman, Department of Epidemiology, School of Public Health, The University of Alabama at Birmingham Dr. Joyce S. Davis, M.D., Professor and Head, Department of Pathology and Laboratory Medicine, College of Medicine, Texas A&M University Dr. Paul F. Deisler, Jr., Visiting Executive Professor, University of Houston, and Past President of the Society for Risk Analysis Dr. John Higginson, Senior Fellow, Georgetown University Medical Center Dr. Marcus M. Key, M.D., Professor of Occupational Medicine, The University of Texas School of Public Health and Visiting Member of Department of Industrial Engineering, Texas A&M University Mr. Ron Lang, President, American Industrial Health Council Dr. Robert L. Sielken, Jr., President of Sielken, Inc., and Adjunct Professor of Statistics, Texas A&M University REVIEWERS FROM THE MEMBERSHIP OF THE INSTITUTE : DOW : Mr. Larry F. Wright, Vice President for Texas Operations Mr. Ron C. Dipprey, Public Issues and State Government Affairs Dr. James H. Saunders, M.D., Director and Environment Health, Texas Operations DUPONT: Mr. J. V. Woodrick, Gulf Coast Regional Services Manager Mr. William B. Beck, Environmental Consultant EXXON: Mr. Keith Fulton, Plant Manager, Baytown Chemical Plant Mr. W. F. Buchholtz, Director of Medicine and Environmental Health Dr. C. F. Yarborough, M.D., Director of Medicine and Environmental Health MONSANTO: Dr. J. D. Wilson, Regulatory Management, Division of Environmental Policy Staff PHILLIPS Dr. J. V. LeBlanc, M.D., Medical Director Mr. Carroll Kirwin, Director of Toxicology ROHM & HAAS TEXAS, INC. : Mr. Joe Foster, President - Plant Manager SHELL Ross, D.O., Corporate Surveillance - Epidemiology t t i '. ; ll iMhlUWmil ai*-t*1QJ|tT|Ljl'i 11 1 i; i i. VAB.0001023858 l l h| I I hbl ISpri Rate per 100, 000 M ale P opulation 'H r: i i; f/ i. ii i ' i r' l( K i ' 5. T. t i' i ' i' c t I. ; ? i- i r |i 1: tr I; N r .. b; t A BRIEF REVIEW OF CHEMICAL CARCINOGENESIS The purpose of this review is three-fold: (1) to provide managers and engineers with an in-depth overview of the developments in the field of chemical carcinogenesis,(2) to provide useful facts and graphs that refute exaggerated claims and false beliefs held by the public, and (3) to provide the background material for the preparation of the next issue of INSIGHTS which is to be entitled "Chemical Carcinogens and Cancer in Perspective." Our inability to find cures for all of the dreaded set of diseases of cancer makes cancer an emotional issue. Out of confusion, the general public has become an easy prey for those who claim to know all of the answers. Exaggerated claims in the 1970's by a number of people, including some with scientific training, that almost all cancer was caused by industrial pollution have been discredited by the careful studies of Doll and Peto1 j, Higginson2, Higginson and Muir3, Cole4, and Wynder and Gori5 in which the major causes of cancer have been identified. The work of Doll and Peto1, published in 1981, is the most detailed analysis of the causes of cancer that has been presented up to this time, and parts of it are presented in subsequent sections. Many have heard only the exaggerated claims and have formed opinions on that basis. There are, however, real risks which must not be confused with the exaggerated claims. The purpose of this report is to "set the record straight," present facts provided by scientists, and give an assessment of just where we are. Comparison of Cancer Mortality with the Production of Chemicals A cancer epidemic has been alleged and attributed to "man-made chemicals." As shown in Figure 1, the facts do not support this allegation, as pointed out by Burack.8 A disease may be highly prevalent, but this fact alone does not make it an epidemic. If a disease is growing rapidly throughout a population at a rate clearly in excess of that normally expected, it is classified as an epidemic. Cancer is a prevalent disease but it is not an epidemic because the total mortality rate of cancer has remained essentially constant from 1930 to 1985 [To correct for yearly changes in population, it is customary to age-adjust all rates relative f The study of Doll and Peto1 is the most thorough and massive of those made to date, and it is drawn upon heavily throughout the present analysis. At the time this study was published, Sir. Richard Doll was Honorary Director, Imperial Cancer Research Fund, Cancer Epidemiology and Clinical Trials Unit and Warden of Green College, Oxford, United Kingdom, and Mr. Richard Peto was Imperial Cancer Research Fund Reader in Cancer Studies, Nuffield Department of Clinical Medicine, University of Oxford, Radcliffe Infirmary, Oxford, United Kingdom.' This study by Doll and Peto is a report commissioned by the Office of Technology Assessment, U.S. Congress, to provide background material for their assessment of "Technologies for Determining Cancer Risks From the Environment" (OTA, 1981). r 2 i Rate per 100, 000 P opulation n! ;h P \i. * i>.:. 1 :f i . . ir u LI l. i I' ii r i. / ;= . ! ` ji; '( Ir I. l: !|: l. ; .i !I ! I ! r i1 ii r ji ; : I . I I1 ir :f i- . [! te: 1= 5; ' 1 n t I' I- I \'l i '! I. VAB.0001023861 r to the population for a particular year.] Over this period of time, the production rate increased over two hundred fold. Likewise emissions from automobiles and diesel-powered vehicles (which contain some carcinogenic material) have increased enormously but total cancer mortality rate has not. Even accounting for a latency period of 15 to 25 years for cancer to develop after exposure, the data do not demonstrate any detectable cancers from the above exposure. The history of cancer deaths from 1930-1985 is displayed in Figure 2 for men and in Figure 3 for women. Observe that the decrease in stomach, colon, uterus, and ovarian cancer rates is approximately equal to the increase in the lung cancer rates. If it were not for lung cancer, the total cancer mortality rate would have declined. These figures demonstrate that there is no epidemic of cancer in the United States except possibly for lung cancer which is known to be caused primarily from the use of tobacco. The perception that there is a significantly higher cancer rate today than there was in the past results in part from the following reasons. First, because of the discovery of preventions and cures for other once fatal infectious diseases, cancer has become a more prevalent cause of deaths. Also, as illustrated by Figure 4 great strides have been made in the treatment of the major cardiovascular diseases. Since everyone must die of something, the prolonging of life allows time for tumors and cancers to develop with the result that cancer will become even more prevalent than it is today as a "disease of old age". Thus, our success in the treatment of other diseases has contributed to cancer's becoming more and more a disease of the elderly; 60% of cancer deaths occur in persons 65 or older, 34% in persons 45 to 64, and 6% in persons under 45 years of age, as shown by Schottenfeld9 in Figure 5. Second, many cancers were not diagnosed in the past, particularly in the elderly, whose deaths were frequently attributed to "natural causes" and "old age". Diagnostic methods have improved and are continuing to do so, leading to the identification and treatment of cancers which would have been missed in the past. Third, people are more open today about the diagnosis of cancer and the subsequent treatments than they were in the past. There was a tendency to keep the diagnosis a secret and in many instances it was even withheld from the patient. Leading Causes of Cancer On the basis of an analysis of data compiled on various types of cancer mortality up until 1980, Doll and Peto1 deduced the distribution of the causes of cancer mortality shown in Figure 6. According to their analysis, diet is the leading cause of cancer with 35% . Doll and Peto point out that although the figure of 35 % is a plausible total, the parts that contribute to it are uncertain in the extreme. The range of acceptable estimates is taken to be 10 to 70%, as shown in Table 1. Use of tobacco is second in the cause of cancer, and accounts for 30% of the mortality with an acceptable range of estimates from 25 to 40%. A figure of less than 1% was attributed to food additives with a range of accepted * estimates of -5 to 2%. The -5% allows for a possible protective effect of antioxidants and other preservatives which may behave as anticarcinogens. The figure of 4% allocated for occupational hazards by Doll and Peto was thought to be accurate by a factor of about two, and thus the acceptable range of estimates was given as 2 4 Table 1. Range of Best Estimate for the Cause of Cancer Shown in Figure 6. [Taken from Doll and Peto.* ] Percent of All Cancer Deaths Cause of Cancer Best Estimate Range of Acceptable Estimates Tobacco 30 Alcohol Diet 3 35 Food Additives <1 Reproductive and Sexual Behavior 7 Occupation 4 Pollution 2 Industrial Products <1 Medicines and Medical Procedures 1 26 to 40 2 to 4 10 to 70 < -5 to 2 1 to 13 2 to 8 < 1 to 5 < 1 to 2 0.5 to 3 Geophysical Factors 3 2 to 4 Infection 10 ? 1 to * Unknown 5 to 7 * * m 4c The ? used by Doll and Peto to denote their uncertainty has been replaced by 5 to 7 so that the best estimates have a sum of approximately 100. Table 2. Group I - Cancer not Known To Be Produced by Occupational Hazards. [Based on Doll and Peto/] Number of Deaths Recorded Types of Cancer in 1978 (United States) Male Lip, Tongue, Pharynx, Small intestine, Gallbladder, Other uterine cancer. Ovary, Melanoma, Breast, Cervix uteri, Other female genital 1_ * organs, Eye, Male 13, 386 genital organs, Thyroid, Myeloma (or bone marrow) TOTAL DEATHS: Male plus Female Female 67, 499 80, 885 Table 3. Group II - Cancer that Possibly May Be Produced by Occupational Hazards. [Based on Doll and Peto. ] Types of Cancer Number of Deaths Recorded in 1978 (United states) Male Mouth, Esopha gus, Stomach , Colon and Rectum, Pancreas, Kidney, 73f 084 Brain, Hodgkins disease, Non-Hodgkins lymphoma Postulated due to Occupational Hazards 731 1 Female 63, 212 316 TOTAL DEATHS: Male plus Female *= 135, 296 TOTAL DEATHS DUE TO OCCUPATIONAL HAZARDS: Male plus Female - \t 047 5 to 8%. A token figure of 2% was assigned to pollution, due chiefly to the uncertain effect of the combustion products of fossil fuels in urban air. Because of the uncertainties involved in attempting to account for the effects of pollution, the acceptable range of estimates of less than 1 to 5% was said to be rather arbitrary. Although there is no cause for alarm from trends in cancer incidence, many industrial products have been so recently introduced that their effects would not yet be apparent. Even though less than 1% was attributed to cancer mortality caused by industrial products with a range of acceptable estimates of less than 1 to 2%, Doll and Peto cautioned that there is too much ignorance for complacency to be justified. The figure of 1% for medicines and medical procedures has a range of acceptable estimates of 0.5 to 3 %. Geophysical factors such as radiations may account for about 3% which is quite reliably known, with a range of acceptable estimates of 2 to 4%. The best estimate of 10% for cancer caused by infections contains a lot of uncertainty, and only the lower number of 1% was given for the range of acceptable estimates. In the case of unknown causes, Doll and Peto give no numbers, and the figure shown in Figure 6 was obtained by difference. Doll and Peto point out that the firmest estimates in Figure 6 are those for tobacco, alcohol, and geophysical factors. Tobacco and diet are seen to be by far the largest contributors to cancer mortality. To estimate the cancer mortality attributable to occupational hazards, Doll and Peto1 divided all cancer mortality into three groups and estimated the number in each group which could have been caused by occupational exposure. In the first group shown in Table 2, no cancer mortality were attributed to occupational hazards. In the second group, presented in Table 3, the evidence that any of the cancer mortality resulted from occupational hazards is weak to inconclusive. Thus, in the absence of definite evidence, Doll and Peto allocated a token of 1% of the cancers in males and 0.5% of t hose in females for a total of 1,047 mortality. Table 4. Group III - Cancers which Can Be Caused by Occupational Hazards. [Based on Doll and Peto^ Types of Cancer Number of Deaths Recorded in 1971 CUnited States'! Male Female Mesentery and Peritoneum (membranes), Liver, Larynx, Lung, Pleura, Nasal sinuses. Bone, Skin (other than melanoma). Prostate, Bladder, Leukemia, and Others Postulated due to Occupational Hazards 14, 046 TOTAL DEATHS: Male plus Female = TOTAL DEATHS DUE TO OCCUPATIONAL HAZARDS: Male plus female 1, 976 184, 774 16, 022 r Bladder and Leukemia All Other Sites Liver, Larynx, Bone, Skin, Prostate, Mesentery * and Pleura * * 0.57%S Lung 0.5% Asbestos 1% 0.2% Lung All other! hazards 1% Jffi Lung Combustion .i ,j Products >_#_ > tj mmm-V-*J* w.m imjm#um#m#** m**r* * r :-ys Figure 7. Distribution and types of the 4% occupational cancer mortality estimated by Doll and Peto.i [Total number of cancer deaths was 401, 955, age-adjusted to the 1970 U. S. Census. Of these, 17,069 were attributed to occupational hazards.] * Membranes that attach organs to body walls. ** Membranes that facilitate movement of lungs. Table 5. Causes of Cancer as Deduced by Higginsom Muir3 and by Wynder and Gori^ Cause Birmingham Region England Cancer Mortality in %[Higginson and Muir3 i Male Female United States Cancer Mortali in % [Wynder i Gori 5 1 Male Female Tobacco Tobacco / alcohol Diet Life-style Occupation Sunlight and Ionizing radiations Iatrogenic (medical treatments) * Exogenous (external) hormones Congenital (present t at birth) and 17 unknown Table 6. Comparison of Cancer Mortality Rates in the United States with Areas of the Lowest Rates for People Under 65 Years of Age* [Selected entries taken from Doll and Peto* ] Male rates (per million) Female rates (per million) Type of Cancer Mouth Colon Bronchus Prostate Bladder Melanoma Tongue Esophagus Connecticut registry Low incidence registry and location 31.8 137.2 325.8 92.3 113.1 40.8 19.8 0.8 Japan, Miyagi 13.7 Nigeria, Ibadan Nigeria, Ibadan Japan, Miyagi 17.8 Japan, Miyagi United Kingdom Liverpool New Mexico, Spanish 34.6 Norway, rural Connecticut registry 11.8 140.7 96.9 Low incidence registry and loca ion 2.4 Japan, Miyagi 11.6 Nigeria, Ibadan Nigeria, Ibadan 32.8 38.6 18.4 Japan, Miyagi United Kingdom Liverpool Israel, Jews Norway, rural Total all Cancers 1, 590 321 1, 775 Total all cancers male and female in Connecticut = 1, 590 + 1, 775 Total all cancers male and female at locations of lowest rates = 321 Avoidable Cancers 3, 365 - 729 2, 636 408 % Avoidable Cancers 2, 636 x 100 3, 365 = 78.3 % * Cancer rates are age-standardized to the U. S. 1970 census. * 3, 365 = 729 ii i I -! !:; I t ! 1 .* r i- I! i Vi i -F n : i ... -:! i ! I !. / i; f ii .i [ f 1 -i i .! =V i : i1 !I i l LV ! `hi. J I. ii ir if ij: n. Ii 1 Li I. ,* !* li: i iTii! I!. "; i |! 1 -i-l I \.i \ I1 ;J i] I? iJ r ii if i: i i-: IK I 'm w. i \ii i. a ,1* t- (i t r fi . r i; j;\ - y r :I :| . I- i . I:; I.. I !/ ih I I 1 :; i' I '3 I\ i-.j VAB.000102386, `i I'j i* i`. rj li S? i ! i;1 In the third group, those types of cancer, some of which may be caused by occupational hazards are listed in Table 4. For each type of cancer, the total number of deaths are given as well as the number attributed to occupational hazards. Although some of each of the types of cancer shown in Table 4 can be attributed to occupational hazards, only one, bladder cancer has been studied. Cole et al.4 attributed 18% of the bladder cancers for men and 6% for women; Davies et al.10 attributed 5% for men and 2% for women, and Hoover et al.11 in the most extensive study for the entire United States attributed 8% of the bladder cancers for both sexes combined to occupational hazards. On the basis of these investigations, Doll and Peto1 attributed 10% for men and 5% for women of the bladder cancer to occupational hazards. Cancer resulting from occupational hazards are thought to be primarily lung cancers. In particular, asbestos was thought to have caused 5% of the lung cancer mortality, combustion of fossil fuels was responsible for another 5%, and other hazards could have caused no more than 5%. On this basis, Doll and Peto attributed 15% of the male cancer cases and 5% of the female cancers to occupational hazards. A summary of the above results follows: Total Cancer Mortality in Groups I, II, III = 401,955 Total Cancer Mortality in Groups I, II, III attributed to Occupational Hazards = 17,069 or 4.25% The estimates described above which were made to deduce the 4.25% figure for cancer mortality due to occupational hazards are shown in Figure 6 and Figure 7. [The numbers shown in Figure 7 were rounded. The precise numbers were: 2.94% for all lung cancer, 0.23% for liver and prostate, 0.51% for bladder and liver, and 0.5% for all other sites.] The estimates of Doll and Peto are supported by the fact that similar studies have been carried out by others and there is general agreement, although not exact, between the various studies. Those by Higginson and Muir3 and Wynder and Gori5 are shown in Table 5. Higginson and Muir refer to "life-style" rather than diet, meaning factors such as lack of dietary fiber, caloric intake, excess fat, and possibly hormone carcinogenesis. Avoidance of Cancer Doll and Peto1 estimated that 70% of all cancers are avoidable. This estimate was deduced by identifying those countries, or areas of countries, having the lowest cancer mortality rate for each type of cancer and comparing these rates with those for the United States. As a basis for the United States, the mortality rates from the Connecticut registry were used. Selected entries from the tabulation of Doll and Peto are shown in Table 6. The difference in the cancer rates for Connecticut and those for the respective areas of lowest incidence may represent the avoidable cancers. These studies suggest that our higher cancer rate for each type of cancer can be attributed to some aspect of our lifestyle, general environment or genetic constitution which differs from those of the country having the lowest incidence. (While some of these cancers may be individually avoidable, it should not be inferred that the full 70% are avoidable because of the many conflicting factors unaccouted for by Doll and Peto's simple comparison.) An extension of this approach offers the possibility for the determination of the cancer causing foods in our diets as well as the cancer causing aspects 8 Table 7. Comparison of Cancer Mortality of the United States with Lowest and Highest Rates for 50 Countries 1982-83, Age-adjusted Rates per 100, 000 Population. Male Rates and Rankings Female Rates and Rankings Type of United Cancer States Lowest Rate and Location Highest Rate and Location United States Lowest Rate and Location Highest Rate and Location Oral 1.1(50) El Salvador 5.3(22) 1.3(49) Peru 2.1(48) Israel 18.6(1) France 16.0(2) Singapore 11.4(3) Hungary Colon 0.8(50) El Salvador and 24.6(19) 2.3(49) Kuwait Rectum 2.5(48) Martinique 36.4(1) Luxembourg 35.5(2) Czechoslovakia 33.3(3) New Zealand Lung 2.5(50) El Salvador 106.9(1) Scotland 72.7(11) 8.2(49) Malta y Gozo 104.2(2) Belgium 8.6(48) Dominican 103.5(3) Netherlands Rep 1.8(13) 17.5(20) 23.7(4) 0.0(50) Martinique 6.9(1) Singapoi 0.6(47) Chile 5.0(2) Kuwait 0.6(47) El Salvador 3.7(3) Panama 1.0(50) El Salvador 29.1(1) New Zei 3.2(49) Peru 25.3(2) Denmarl 3.5(48) Mexico 24.5(3) Hungarj 1.7(50) El Salvador 31.0(1) Scotland 2.7(49) Paraguay 28.2(2) Iceland 3.5(48) Peru 24.6(3) Singapoi Breast 26.7(16) 1.7(50) El Salvador 34.9(1) Malta & 5.8(49) Peru 6.2(48) Japan 34.5(2) England Wales Uterus 6.1(50) Dominican Rep Stomach 7.8(49) 8.1(48) El Salvador 10.4(47) Kuwait 3.3(50) El Salvador Prostate 23.1(21) 4.6(49) Japan 5.4(48) Singapore 63.2(1) Costa Rica 58.8(2) Japan 51.8(3) Chile 52.1(1) Martinique 32.0(2) Switzerland 31.3(3) Luxembourg 7.8(38) 3.7(49) 4.9(50) Israel 32.4(1) Surinam 5.2(49) Greece 27.9(2) Paragua] 5.5(48) Iceland 24.9(3) Venezuel 3.3(50) Dominican Rep 27.8(1) Costa Rti 5.0(48) El Salvador 27.5(2) Japan 6.0(47) Canada 22.3(3) Chile Leukemia 8.4(6) 1.6(50) Surinam 2.2(49) Peru 2.4(48) Dominican Rep 14.2(1) Luxembourg 9.4(2) Denmark 8.8(3) Malta & Gozo 50(17) 1.6(50) Surinam 1.3(49) Dominican Rep 1.6(48) Barbados 6.9(1) Martinlqi 6.1(2) Costa Rit 5.7(3) Hungary Source: Facts and Figures, 1988, American Cancer Society and World Health Statistics Annual 1983-1986. 120 (100) 100 ! i i1 MH i* v i. i 1984 1985 1986 Year 1987 Figure 8. Air 1974 to 1984, emissions by Dow Chemical they were reduced by 70%. U. S. A. were reduced [Taken from The Point 40% is ... from 1984 to 1987, and from , No. 117, June 30, 1988.1 :i 11 ,/ / / r: rtfn -!> 3 i: il I! IV i! n M: I'! Ii ill !J ! I I- : . 1 i.-|. ii-H I . I : !Ii l! :li : Si [r i 'ri 1..1 } ! 1 :i : I' i IN: i ! 'I : I! i!!-i ^ i`- I 4 l.-V4 I i c .! 1 --i':: `ff ii j; b h l !i i; ? Jiii MM Ii ip I'll1- ; l / .IjjS 1 ' SIN m idli r f v, !1[ i i : h! i i t -- -nI! M Mi:/' * fi iir . I ii' I';'!; J !;r rj i.: !I ;i . I [ i i I if i i- If i i! i! I l! I! : ill! ;i mil .i.i | ii i; VAB.00010238' i of our lifestyle. Obviously, knowing that 35% of the cancer may be attributed to diet is not very helpful in avoiding cancer unless we can determine the foods to be avoided. Actually, the 35% is probably not fully avoidable because trace nutrients can be both nutritionally necessary and carcinogenic, and the best diets must contain some trace nutrients. To provide an idea of how the United States cancer mortality rates compare with those of countries having the highest and lowest rates for specific types of cancer, the tabulation shown in Table 7 was prepared from a recent report of the American Cancer Society. The Environmental Movement During the 1960's an environmental movement was bom because of pollution problems, many of which were severe. The movement was strongly fueled by scientists such as Rachel Carson12, a biologist in the Fish and Wildlife Service. Her book, Silent Spring, focused mainly on pesticides of which DDT was her greatest concern. Her dramatic approach led to a needed tightening up of the regulations and use of pesticides. Rachel. Carson was followed by others who predicted a catastrophic end to our way of life by as early as the 1980's and certainly by the early 2000's. Among them were Paul Ehrlich [ an entomologist and ecologist], Barry Commoner [a biologist] and an MIT group. Their remedy was "zero growth" and a redistribution of Western wealth to Third World nations. Commoner also called for a change in our constitution and system of government. Recently he gave a full exposition of his views along these same lines in the New Yorker magazine (June 15, 1987). In 1972, an MIT computer study [conducted at the request of the Club of Rome] called the Limits of Growth appeared. In this study an "uncontrollable decline" was predicted in which industrial resources, industrial output, food supply, and the population would crash somewhere near the year 2005. Although the MIT study [published by Meadows et al.13] produced the conclusion that life on earth was on the verge of ending, there was little data available to support this conclusion as pointed out by Edith Efron.14 Obviously our way of life has not come to a catastrophic end. More people are employed today than ever before. Industry has made tremendous strides in handling of its waste problems. Typical of the reduction of emissions throughout the chemical industry is that shown in Figure 8 for air emissions by Dow Chemical Company. From 1974 to 1984, Dow's air emissions were reduced by 70%, and from 1984 to 1987 they were further reduced by 40%. There are, however, some areas in obvious need of improvement. For example, waste disposal in many cities, particularly in the northeast, has become a serious problem. Air pollution caused by automobiles continues to be a problem in our cities, regardless of whether they are located in industrial or non-industrial areas. Ranking of the Various Countries in Cancer Mortality In the middle 1970's, those who had led the environmental movement in the 1970's joined by others and with widespread publicity in the press turned to cancer, which they attributed to "man-made chemicals", as their rallying cry. The same solutions offered for their pending environmental disaster were offered as the solution to the cancer problem. Dan Rather opened his documentary entitled The American Way to Death on October 15, 1975 with this statement: "The news tonight is that the United States is number one in cancer. The National Cancer Institute estimates that if you are living in America, your chances of getting cancer are higher than anywhere else in the world."15 The truth is that the United States ranked eighth for Blacks and 25th for Whites out of a total of 36 countries, as determined by Mitsui Segi16 two years prior to the broadcast. Segi's analysis was based on the death rates of the nine most common cancers, buccal, esophagus, colon and rectum, lung, stomach, breast, uterus, and leukemia. Unfortunately, the public never learned of the actual ranking of the United States at the time of Rather's statement nor the ranking by the World Health Organization17 which ranked the United States 19th for men and 18th for women out of 44 nations in 1970-- 1971. According to the most recent study, shown in Table 8, the United States ranks 22nd for men and 21st for women, out of 50 nations. Table 8. Cancer Mortality for All Sites (oral, colon & rectum, prostate, breast, uterus, stomach, lung, leukemia) for 50 Countries 1982-83, Age-adjusted Rates per 100, 000 Population. Rates and Rankings Country Male Female Luxembourg Hungary Belgium Czechoslovakia Netherlands Scotland France Singapore Uruguay Denmark Germany, F. R. England & Wales Austria Switzerland Poland Finland New Zealand Northern Ireland Canada Ireland Australia United States Germany, D. R. Malta & Gozo Norway 310.9(1) 286.1(2) 284.3(3) 281.2(4) 270.2(5) 268.0(6) 262.9(7) 258.4(8) 255.7(9) 248.1(10) 245.5(11) 243.7(12) 241.8(13) 241.4(14) 236.5(15) 227.5(16) 226.4(17) 224.9(18) 221.2(19) 219.8(20) 218.2(21) 216.6(22) 214.7(23) 208.3(24) 198.3(25) 150.5(7) 166.3(3) 147.6(13) 150.1(10) 141.8(17) 172.7(2) 121.3(31) 141.4(18) 150.0(11) 175.2(1) 150.3(9) 157.3(9) 150.4(8) 135.5(22) 131.1(27) 124.2(29) 157.6(5) 147.4(14) 139.6(19) 158.6(4) 131.0(28) 136.5(21) 132.1(21) 143.6(16) 131.6(26) Rates and Rankings Country Male Female Iceland 195.7(26) Japan 194.3(27) Chile 192.1(28) Costa Rica 186.5(29) Yugoslavia 186.1(30) Sweden 177.0(31) Martinique 172.9(32) Cuba 172.4(33) Portugal 170.1(34) Bulgaria 166.2(35) Greece 160.7(36) Israel 157.8(37) Barbados 155.7(38) Romania 153.6(39) Kuwait 149.8(40) Surinam 148.4(41) Puerto Rico 140.3(42) Venezuela 133.5(43) Panama 115.1(44) Mauritrlus 102.4(45) Paraguay 91.8(46) Mexico 91.5(47) Peru 75.8(48) r Dominican Rep. 67.3(49) El Salvador 37.5(50) 149.4(12) 105.6(36) 144.4(15) 137.6(20) 107.8(35) 131.7(25) 92.9(44) 123.8(30) 105.2(37) 102.4(38) 100.9(39) 132.0(24) 118.4(33) 99.7(41) 109.4(34) 100.5(40) 89.6(46) 120.8(32) 93.5(43) 79.9(47) 97.1(42) 92.8(45) 76.3(48) 65.0(49) 48.7(50) Source: Facts and Figures, 1988, American Cancer Society and World Health Statistics Annual 1983-1986. % J h i i . i i, i I! I I L IP r-ij. ii I: i i i i i i i i i i i i i i r i iI iI I '! i I I 1 't i J \ j j f f ii i i i li \f l; ir !il' i. I I I I' i I i I f I \ i t Exaggerated estimates of cancer mortality caused by "man-made chemicals" began to appear in the middle 1970's prior to the publication of Doll and Peto's1 careful study in 1981 in which they attributed 4% of the cancer mortality to occupational hazards and 2% to pollution, for a total of approximately 6% or 9% if alcoholic beverages are included, recognizing that exposure to alcohol is largely a matter of lifestyle. [This estimate is based on the assumption that the net contribution of food additives and industrial products (shown in Figure 6) and medicines are zero because of the possible anticarcinogenic effect of food additives and the fact that medicines save more lives than they take.] Professor Corbett in his book, Cancer and Chemicals,18 published in 1977, said that it was man who was creating the chemical pollution that was causing 80% of the human cancer. In 1976, James Bishop Jr.19 said on CBS Face the Nation, that it was generally accepted that 60% to 90% of all cancer was caused by "man-made chemicals". In 1977, Larry Agran, placed the figure at 90% in his book, The Cancer Connection,20 Edith Efron14 called attention to the equivocation of Agran and Epstein21 in attributing 90% of all cancer to "man-made chemicals" because they give little consideration to natural occurring carcinogens such as arsenic, asbestos, nickel, and chromium. Also, Commoner, Epstein and others managed to equate environmental factors with "man-made chemicals" and industrial pollution. As pointed out by Higginson and Muir,3 the word "environment" included not only discrete chemical carcinogens but also life styles such as dietary, social habits, tobacco smoking and alcoholic beverages as well as occupational hazards. As early as 1969, Higginson22 had published the estimate that 90% of all cancer (exclusive of those related to skin pigmentation) were influenced by external factors and were preventable. Higginson used the word "environment" in the broad sense of all external factors (diet, tobacco, life style, natural carcinogens, and air and water pollution); whereas, the aforementioned and others appeared to equate environmental factors with "man-made chemicals." Only a negligible increase in lung cancer over that caused by tobacco was attributed to atmospheric pollution. The claims of 60% to 90% cancer mortality from "man-made chemicals" are easily refuted by simply comparing the cancer rates in industrial and non-industrial areas. For example, the incidence of cancer (exclusive of tobacco-related lung cancer) in non-indust rial Geneva, Switzerland is higher then industrial England. Also, non-industrial San Francisco has a higher cancer incidence than nearby industrial Pittsburgh (American Industrial Health Council23 ). In 1978, a widely circulated but unpublished and unsigned report by the Department of Health, Education, and Welfare asserted that as much as 38% of cancer was due to occupational exposure. This report24 called the "Estimates Paper" has never been widely accepted by the scientific community and Doll and Peto1 said that it was written "for political rather than scientific purposes." S' Higginson25 attributed the over estimates of HEW to the fact that these people found it hard to accept that general air pollution, smoking factory chimney etc. are not the major causes of cancer. They really hoped to be able to prove this. Then they would be able to say "let us regulate everything to zero exposure and then we have no more cancer." Figure 9. The metabolic processes of the body may convert a precarcinogen into a carcinogen Research Developments -- Discovery of Metabolism of Chem icals to Carcinogens, Inhibitors, Anticarcinogens, Co carcinogens, and Promoters A chemical carcinogen may be defined as any substance which causes cancer. From a practical point of view, this definition is subject to many ambiguities as indicated in the discussions which follow in subsequent sections. There are two major classes of chemicals that induce cancer, direct acting and indirect acting carcinogens. During the year 1970-74, the Millers26 demonstrated that indirect- carcinogens (or precarcinogens) are metabolized to carcinogens upon entering the body of an animal as shown in Figure 9. On the other hand, direct acting carcinogens are in their carcinogenic form prior to entering the body. The Millers' discovery led to major problems because of the difference in mammalian metabolism in different species. As a consequence, the extrapolation of the results from animal tests to humans tends to break down. Chemicals known as inhibitors and anticarcinogens were discovered in 1929 by Berenblum.27 When applied or taken simultaneously with a known animal carcinogen, anticarcinogens can delay the appearance of tumors, diminsh the number of tumors, prevent tumors from occurring, or reverse the early phases of the carcinogenic process. In particular, Berenblum discovered that dichloroethyl sulfide inhibited the formation of cancer in a mouse which had been exposed to carcinogenic tar - a known animal carcinogen. This concept is illustrated in Figure 10. Subsequently, many other anticarcinogens were discovered and their role in the cancer process amplified. Inhibitors are generally regarded as those substances which inhibit or delay cancer formation by decreasing the rate of cell division. Other chemicals called cocarcinogens were also discovered by Berenblum.28 The names "cocarcinogens" and "promoters" have somewhat overlapping meanings. The name "cocarcinogens" is usually reserved for those chemicals which enhance the action of carcinogens, particularly in the initiation phase of the cancer process as illustrated in Figure 11. On the other hand, the term "promoter" is generally used to mean any chemical which promotes the cancer process by increasing the rate of cell division of the initiated cells. In addition to substances which are carcinogenic, it is well known that radiations such as ultraviolet, X-rays, and gamma rays can cause cancer, through the formation of free radicals from chemicals in the near neighborhood of the DNA or from the DNA itself, which can react with the DNA. Research Developments -- The Two--Stage (or Initiator- Promoter) Theory of Cancer Formation <* The discovery of initiators and promoters led to the two-stage or initiator-promoter theory of cancer which is illustrated in Figure 11. It was shown by Berenblum28 that the carcinogen benzo(a)pyrene initiates a cancer when applied to the skin of a mouse. The cancer grew much faster when croton oil was applied either simultaneously or consecutively with the benzo(a)pyrene. Since the croton oil had no effect if it was applied prior to the application of benzo(a)pyrene, it was concluded that the process is two-stage with the promotion stage always following the initiation stage. Anticarcinogens Inhibitors i!;r f ! :m ' yi i : i: i ;n i; i i -j h !|: i!!:! ;! i.:!: 'I i: !Mi i ! i. I l l! !I .1 :|: ,i l| | i l! :I I! ! I Ii ill i i! L L-`l .-I t-Ef k t ]i"- r si: !!i ! I ' I is !I i -t I IN E! i ! i- V 1 I! :! :i t Iif! :iif. I'vi I , sj?: i. : Ni :L-| I)' S:-r- Jill. I II : tm ui? j L-; i I>: r M! .,'1 ir'4lli VAB.OOOlOl =.ir. '-i l-'-a I :ln :;[ Er:- -lili i v in W*# i |l Vllitf' H.-II !- im ->i; i- it ~j MW h J'i iii!J` !!:" B it E \> ! I m u= i! ii -:l|. p- j ; The initiation stage is thought to consist of a mutation of the DNA molecule by an initiator molecule (or activated metabolite) which becomes chemically bound to or reacts with the DNA or other macromolecules. Consequently an initiator is also frequently referred to as a mutagen. The concept that cancer was caused by mutations was a long held theory dating back as far as the 1920's. Support for the initiator stage was also provided by Ames et al.29 with the development of a simple biological test for the mutagenicity of chemicals, which merits some discussion. The test consists of the use of a rat or human liver homogenate (S-9Mix) for the carcinogen activation (thus supplying the mammalian metabolism) and a set of salmonella histidine mutants for mutation detection. The homogenate, bacteria, a TPNH enzyme generating system, and the compound to be tested are then incubated directly on a petri plate. Compared with animal testing, the Ames test is both more rapid and economical. In an initial testing program, Ames et al.29,3 found that 90% of the animal carcinogens were also mutagens. However, as further tests were run, it was found that for certain classes of chemical carcinogens , the test did not show them to be mutagens. converse was found; namely, not all mutagens were carcinogens, and not all noncarcinogens were nonmutagens. The final conclusion was that the Airies test could not be regarded as an absolute test for the identification of carcinogens, but that it could be useful for screening purposes The second stage, the promotion step involves the subsequent progression and cell proliferation through a series of pathological states heading eventually to a malignant tumor. Cell proliferation can be accelerated by chronic cell-killing viruses, such as the human carcinogenic virus, hepatitus B (a major cause of liver cancer), and human papilloma virus 16 (HPV16) [a contributor to cancer of the cervix]. The promotion stage can also be accelerated by hormones which may be the major factor in causing all hormonally influenced cancers such as cancer of the breast.31 Chemicals may act as accelerators of the promotion step. As an example, alcohol causes cirrhosis of the liver which leads to cancer of the liver. There is increasing evidence that small amounts of promoters are not active, but when taken in large amounts cause chronic irritation, cell killing, and cell proliferation. While the cancer mechanism has been represented by two major stages, it has been thought to consist of many stages; perhaps as many as six. The two-stage mechanism properly defined may be the most prevalent of the cancer mechanisms. Although radiations are not substances, they can be included in this mechanism by virtue of the fact that they act as mutagens by damaging the DNA directly or indirectly by damaging macromolecules such as enzymes that are involved in its formation. Molecules damaged by radiation axe highly reactive and tend to react with body chemicals in their immediate vicinity. further complicate the picture of the cancer mechanism, it is now known that initiators, cocarcinogens, promoters, inhibitors, and anticaxcinogens axe produced internsdly in the body, independent of outside influence. cancer counterbalanced by an abundance of repair mechanisms, anticaxcinogens and inhibitors provided bv nature, as illustrated t i. |; I II ih !j 'I I ' i? 'I' 'l.Mjiiu r: rfc-i ! I' 1' I- >i I--.I- /.: r Research Developments Formation The Two-Mutation Theory of Cancer If :r! 1 and Knudson32. and Wilson called a "two-stage" model. However, to avoid confusion with the two-stage model L^ described above, the Knudson-Moolgavkar model is referred to herein as the "Twofl Mutation" model as ssiuggested by Wilson33 because the two-stages shown in Figure 11 have in effect been replaced by two critical mutations. ::i These two mutations on the critical path for the transformation of a normal cell to a cancerous one are assumed to be irreversible. An important feature of the newer model !:? 4-s? which enables it to account for a greater variety of cancers is the recognition of the role of increased cell division throughout the cancer formation process. Since cocarcinogens are : iI i!.f MIL- known to increase normal cell division rates, a cocarcinogen (both external and internal) may be one of the inputs to the first mutation in the same manner as shown for Stage 1 ! :i r ,i: in Figure 11 for the two-stage model. :I damaged ! ;l ;i division before it can be repaired is increased. Thus, fixed irreversibly in all future cells. Increased rates of cell division also increase the probability of the occurrence of mutations from uncontrollabe events such as those resulting from errors in DNA gene transcription, cosmic radiation, and natural mutagens. Normally all IIL ! ! ; !f 1:2 Ii damaged However, any damaged DNA change or mutation becoming fixed in future cells. The assumption that only two mutations lie on the critical path between normal and ! !. Ki I- cancerous cells has not been generally established. However, it has been sliown to rigorously hold for some cancers such as cancer of the retina in children. In this case, some children are born with an inherited mutated gene (which constitutes the first event), and the second !ii 1I 1 11 mutation usually occurs in early childhood leading to cancer. Chemicals (and other agents) can contribute to cancer incidence in two ways. First, the agent may react directly with DNA, increasing the number of damaged DNA* molecules thereby increasing the probability that a damaged DNA molecule will escape repair before cell division. Second, the agent may react with some other component in the cell which causes an increase in cell division or the-agent may kill the cell. If it kills the cell, there follows a temporary increase in the rate of cell division such as is observed in the formation of scar tissue, which in turn contributes to cancer formation by increasing the probability of occurrence of mutations resulting from uncontrollable events such as those enumerated above. Thus, the concept of accelerated cell division provides an explanation for the causation of cancer by agents such as viruses which may not react directly with DNA but which do cause damage and chronic irritation. :;i Ml: !l! : ' !!:i 'I:! I I Yl IC | ! Mil 4- \f Not only does the feature of the rate of cell division of the two-mutation model aid in the explanation of essentially all types of cancer formation, it also provides onef possible answer to the avoidance of cancer: namely, the reduction of the rate of cell division. An increase in that class of anticarcinogens, called inhibitors, which have the capacity to inhibit or decrease the rate of cell division would consequently prevent or reduce the formation and proliferation of cancer. Slowing cell division of the initiated cells after the first event :iJ ! ij i, ); .. i I! :iI 4 17 i ! !l ! I- j. h 1 - !' i!;!i I il !:;i i ! i;:!i ! i l|!;;i : i I::!! : ! I''I ! !!|!:i!| I! li'i.i VAB. V. 3 t i 5. 'i. reduces the probability of occurrence of the second critical event. Slowing of cell division after the second event reduces the proliferation of the cancer and makes it dormant. Research Developments -- Inhibited Gap Junction Communi cations: A Nongenetic Based Model This report deals primarily with mechanisms based on genetically caused cancers because most of the work, beginning with Armitage and Doll34, has been done in this area. However, there are significant cancers which cannot be directly attributed to genetic changes in the sense that the carcinogens causing these cancers are not mutagens. For example, potent carcinogens such as polybrominated biphenols (PBB) do not exhibit mutagenic behavior according to all of the short-term tests. The Gap Junction Intercellular Communication (GJIC) model proposed by Trosko35 pro vides an explanation for carcinogens whether they are either mutagenic or nonmutagenic. This model was the first to recognize intercellular communication and its importance in inhibition of cell division of initiated or mutated cells. In this model it is supposed that the process is initiated by the mutation of a cell by any means (some mutagenic or uncon trollable event independent of the carcinogen in question). Once formed, these initiated cells are held in check by surrounding normal cells through intercellular communication. This process functions through the transfer of negative growth factors in the form of calcium ions, pH changes, free radicals, and small molecules which are transferred across a membrane-protein interface (called a Gap Junction) from one cell to another. Any substance such as a carcinogen or an event ( a cosmic ray or a cell death) can inhibit or block the intercellular communication which releases the initiated (mutated) cells from the restraining effects of surrounding normal cells. Once the gap junctions have been blocked, the cell division process of the mutated cells is no longer restricted, and uncontrolled cell division occurs with the progression to the formation of malignant cells. As recognized by Trosko, the Gap Junction Intercellular Communication model possesses the same complications associated with all models of cancinogenicity such as species, tissue and cell type specificity. Also, many chemicals (PCB, DDT, TCDD, phenobarbital) under one set of biological conditions act as carcinogens and under some other set, act as ant i carcinogens. Research Developments -- Identification of Human Carcinogens by Epidemiologists From the standpoint of the public, the definition of a carcinogen given above is taken to mean any substance which causes cancer in humans. Since substances which cause cancer in humans do not necessarily cause cancer in animals and conversely, carcinogens should be classified into two subgroups : "human carcinogens" and "animal carcinogens", and further subdivided into mouse, rat, etc. However, confusion in the general public exists because only the single designation, ''carcinogens" is used for both humans and animals. 18 1 i< i 4 N nt 1 If1 fh ; !!r !' = J i. i I' r i ' l . *i i i: i ' N' :i I .! I r !*i r-ei. ... ; Jr:;F5i.:1. 1 `i I I i.f 'ii'Vf i; : i ill Table 9. Human Carcinogens - Industrial Processes and Chemicals. [From IARC Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Humans, Supplement 4 (1982>?^ ] 1. Industrial Processes and Occupational Exposures Auramine Manufacture Boot and Shoe Manufacture and Repair (certain occupations) Furniture Manufacture Isopropyl Alcohol Manufacture (strong-acid process) Nickel Refining Rubber Industry (certain occupations) Underground Haematite Mining (with exposure to radon) 2. Chemicals and Groups of Chemicals 4-Aminobiphenyl Analgesic Mixtures Containing Phenacetin *a* Arsenic and Arsenic Compounds 'a' Asbestos Azathioprine Benzene Benzidine N, N-Bis(2-chloroethyl)-2-naphthylamine (Chlornaphazine) Bis(chloromethyl)ether and technical-grade chloromethyl methyl ether 1, 4-Butanediol dimethanesulphonate (Myleran) Certain Combined Chemotherapy for Lymphomas^' (including MOPP^b)) Chlorambucil Chromium and Certain Chromium Compounds Conjugated Oestrogens^ Cyclophosphamide Diethylstilboestrol Melphalan Methoxsalen with Ultra-violet A Therapy (PUVA) Mustard Gas 2-Naphthylamine Soots, Tars and Oils^a'' Treosulphan Vinyl Chloride This list does not include known human carcinogens such as tobacco smoke, betel quid, and alcoholic beverages. (a) The compound(s) responsible for the carcinogenic effect in humans cannot be specified. (b) Procarbazine, nitrogen mustard, vincristine and prednisone. (c) Mineral Oils may vary in composition, particularly in relation to their content of carcinogenic polycyclic aromatic hydrocarbons. fraught with difficulties because of the different responses exhibited by different animal species to chemicals. Responses may differ not only from one species to another, but from male to female of the same species, and also from animals to humans. For example,^mice get cancer from perchloroethylene, but rats, rabbits, guinea pigs and monkeys do not.38 Rats and humans develop cancer from Aflatoxin Bi, but mice and monkeys are relatively resistant39 as described in Figure 14. Man gets cancer from /?-naphthylamine, but most strains of rats40 and hamsters do not41, whereas dogs do. Thus, the extrapolation of the results of tests made on animals to humans always has uncertainties. That is, just because II II a chemical is an animal carcinogen does not prove that it is a human carcinogen. To further complicate the picture and add to the confusion is the fact that a given carcinogen can affect entirely different organs in different mammalian species. For example, benzidine is said to cause bladder tumors in man, liver tumors in the hamster, and acoustic tumors in the rat while estrogens are reported to cause breast tumors in mice, uterine and abdominal tumors in the guinea pig, and kidney tumors in the hamster.14 Also arguments have persisted in scientific circles concerning the number of animal species which are needed for a reliable extrapolation to humans. Some say three, others say two and some including OSHA say one positive test in one animal species is sufficient to label a substance as a potential human carcinogen. ;! Ii Figure 14. Aflatoxin B. , a natural carcinogen found in grains and peanuts, has a different effect on different animal species. Research Developments Problems in Extrapolation from High-Dose Animal Tests to Low-Level Human Exposure Human exposure animal t these correspondingly low levels of exposure to be meaningful, a prohibitively large number (millions) of animals would be required. The alternative of obtaining Sf significant number of tumors in a relatively small population by use of high doses has become standard in animal tests. However, this approach leads to further difficulties because many chemicals are carcinogenic at high doses but not at low doses. Thus, the extrapolation from high-dose animal tests to low-dose human exposure becomes even more difficult as summarized in Ficure 15. 21 Ii ii ,.i i| I ii I! :i i !i I i;: i '! I :i!: |ll[ ::;ii I!f ::iijj||:j;!U| ;ij 11! i j .I -Tii;! ; 'i S !!i !:i 1 :'li!1 ' :'li: i :ij!j =i;:| i Ml: !j'l ji 1' i! : . ' i ,i .lI,! -L I i! . ' I'1 I. I .1 I! iji'1 i: ! i i iii'l M ni:; i MM! High dose, Body of Animal Cancer Low dos Body of Animal No evidence of cancer HOW DO WE EXTRAPOLATE TO Low environmental exposure HUMAN ay or may not cause cancer Figure 15. How do we extrapolate from high dose rates for animal tests to low exposure rates for humans? Input of Chemical to body CAM MACROMOLECULE CAG Replicas of ADDUCTS DNA Reaction with macromolecule Replication of damaeed DNA Reaction with DNA METABOLITE Excretion Detoxification DNA Repair CE CAD DETOXIFIED METABOLITE CAD2 EXCRETED CHEMICAL REPAIRED DNA Figure 16. A Hypothetical model of the fate of a carcinogen in the body of a mammal. IFrom Gehring, P. J., and G. E. Blau, J. Environ. Pathol. Toxicol., 1, 163(1977).! Research Developments -- The Theory that Cancer is Formed by a System of Competing Chemical Reactions within the Body is Gaining Acceptance The difference in the results obtained from the animal tests at high doses and low doses can be visualized through the use of Pharmacokinetics models. "Pharmacokinetics" is derived from the Greek word "pharmakon" meaning drug or poison and the word ''kinetics" which refers to the speed of a chemical reaction. The models were proposed and utilized in a series of papers by Gehring and Blau42, and Reitz and Watanabe43, Andersen et al.44, and Clewell and Andersen.45 These models consider both the reaction of mutagens with DNA to form DNA adducts, and the repair of DNA adducts. The initial findings by Miller and Miller26 have been formalized and expanded in a more recent article46 in which they state that most chemical carcinogens. are metabolized into a chemically active form called a metabolite, upon entering the body. The metabolite is capable of reacting with many cellular macromolecules such as DNA, RNA, and proteins.46 Some carcinogens such as alkylating agents are in their ultimate form as administered, but most require metabolism to the active metabolite form.46 Of particular importance is the reaction of the carcinogen or the metabolite with the DNA, since this macromolecule contains the genetic information for the cell. The specific sites of reaction on the DNA with the given chemical are very important in determining 22 'iMIl i: I !I M !! I the mutagenetic effect. Certain substitutions are more likely to result in miscoding Furthermore than Experimental evidence that DNA repair is possible in metabolic systems was provided b; Russel et al.47'48 Ethylnitrosourea, the most potent mutagen for mice yet discovered, w administered to mice in two ways. In one test, one massive dose of 100 mg/kg (milligi l.i I-! of ethyl-nitrosourea per kilogram of mouse) was administered, and in the other test, d< g/kg were administered same u g/kg mutations as did the massive dose. Russel et al. interpreted the reduced mutageni<| effect of the small weekly doses to the repair process for the damaged process appeared to have been overwhelmed when the chemical was given as a single larg g/kg Figure 16 was used by Gehrini and Blau and by Clewell and Andersen to represent the biochemical processe when a chemical carcinogen is introduced into the body of a mammal. After th having concentration Co has entered the body, it is absorbed in the body tissue at concentration C. Next , some of it may be excreted with concentration Ce and of it bioactivated to a metabolite with concentration Ca* The bioactivated mo] reacts to form detoxified chemicals, noncritical macromolecules, or it may react w form CAG (damaged DNA or DNA adducts). The DNA adducts to give CAG form formation of CAG* is the crucial because whose DNA no longer appears to be in need of repair by the repair systems of the body. This model of the reaction system may be represented by a system of differential equation and the parameters and rate constants appearing in these equations evaluated by use < I -. Il i ,I !'i i.l in vivo and in vitro experiments as described by Clewell and Andersen.45 Research Developments il ' I j At High Doses of a Chemical !i ' Carcinogen, the Repair Mechanism for the Damaged DNA Overwhelmed and Cancer Formation may Result i: i ri ;ii ! i i |- i il Mi II V i ill! I .!' Ii jI !I II i !' i I! ;i> I if: : I' I 11 i I 'l ! |> I i !: i !' I i .i; i li ii i I II ll. : . I M' If I! !i I : I: i :I !|-.l nr i. ! I! Vi I il ! .1: !i To demonstrate that the above model describes known metabolic behavior, a series I: : plausible values for the parameters and rate constants were selected and the resulting i of differential equations solved numerically by use of a computer. Solutions were obtain for a wide variation of initial concentrations Co ranging from 10-6 to 1 in moles/kg. T * Ii results are shown in Figure 17. i! ;i These graphs of the concentrations of the postulated compounds formed in the moi !i i "i iI are useful for the elucidation of the problem of high dose-low doserextrapolations. First ! i : : iI observe that for initial doses greater than 10-4, the replicated-damaged DNA begins to II than the ability of the system to repair damaged i 5gins to decrease at 10"2, which implies that i becoming overwhelmed r|| jj ; 11 i!:! i I 'I ! I! I >1 !i ! ! ; Ml ! !! i li ; I i^ 23 i i J I il:l ;! Hi li! ! iI r. II! M .i(l " I Mi! I I [Jill I1!. .fII I: I!; I> : !' ::iii ill III! !:i Hi :; I iii; 'l;! i- !! . il' ! :jm Ml., in li :ii I =i! ! ! I *1 - '! :l! :.'! :!i i.:=i ;i . : i -i! :': |. ! : 1 il . in '^Il^li"v ' :l! H-ii: i: ! :i! iHi.li i iii 11 i -Mi; : i !. i !! l:i:i I "iMl .! |::i::!i:i!i 1 11;: Hllllli Ji i.:i il'liii li;:i !i!: li i;l l;ii; ' I!1' 111 1*1!.....wilil il: ; j;i;j!!;IVi!! !1 ! i.;;; ' i- . i; ili.i i- I' II I i s;i.. !|:M:!l! Mi l.i i'liii! !! MMlj i :!:iin hMi in: !I il-inn i !:,:i Il I .-1-. :i-h! m: '' I: '! i: i: r- f 1 Concentration of initial dose - moles / kg Figure 17. Variation of the products CAM, CAD2 and CAG* as a function of the initial concentra tion. CAM = concentration of macromolecules, CAD2 = concentration of repaired DNA, and CAG* concentration of replicated damaged DNA molecules; all concentrations are in g moles per Kg of ani mal. [From Gehring, P. J., and Blau, J. Environ. Pathol. Toxicol., 1, 163 (1977).] Initial dose of carcinogen Outlet for replicas of damaged DNA r Figure 18. Hydraulic analogy of the overwhelming of the repair system for damaged DNA. [From Gehring, P. J., and G. E. Blau, J. Environ. Pathol. Toxicol., 1, 163 (1977).] 24 i: I I! i i it can be repaired. Production of macromolecules CAM also but such molecules are not involved in the replication processes. To illustrate the overwhelming of the system at high doses, the hydraulic analogy shown Figure 18 (analogous to the one proposed by Gehring and Blau) greater than Co = 10 4, small increases in the initial concent. give much larger increases in the concentration Cag* ^he damaged adduct, which illustrated by the following numerical example. Example. Suppose the concentration fold from 10"4 to 10"2. Use Figure 17 to find the concentration of the damaged DH adduct at 10 "2. Solution : From Figure 17, it follows that at Co = 1 Cag 7x 10 and At Co Cag 7 x 10-7 x 10 7 x10-n Cag i >1 Ii! :! l .1 IL! I- I | '! I I' ! ' l1 III ! I 'I I i >i;! i! r:j jl : ii !i : i I i:: I : f I! ML1 1I Ii M::l I! i: Iji !i i iii i :! Ii i.m ;i :| i.1! |! i! ;! I: ! : i i: !i I lI M !: Ii ii i.!i >i '.l I! I I :| I and Cag 7 x 10"5 x 10 * ------------------------------------- v ------------------------------------------ * increases by a factor of 10,000; that is, i:l 7 x 10'7 of damaged DNA adcta I- ! jI. : 'if 7 x 10 -ii 10,000 ill example demonstrates the effect of overwhelming the DN A repair mechanisms by of high doses of the carcinogen. It also suggests the possibility of overestimation of the ri through the use of linear extrapolation methods. Note, however, that this multiplier*' factor does not apply at low initial concentrations near the origin of the graph in Fi vi III :t |j| r- Use of Physiologically Based Pharmacokinetics (PB-PK) Mode r.i in Risk Assessment When the transport of a chemical from its point of entry into the body to the reaction sit within the body is included in the model, the combined model is called a Physiologically Based Pharmacokinetic model. Both in vivo and in vitro data are generally needed order to evaluate the parameters of this model. Reitz et al.43 evaluated three types !Hi i 'I l 11 Ii I II I 'i I ;'l i ! ij' -u ,-h- A---- If* It .! I iii i ilt: Is - - Jl ItL iji $ i.i.i i JH* t L, $ ii- !: h I 'ii :t!', ll f. s! / / J.-. !: 1 jli iSti r1 'll- ;!i Ji -i. =i: -im I; A- hr Si A-r to f r-1 ii 4 > Sift m HI**'1> 1h ill j- tsSV +: ,,r III :.! ^ ii# Ifi IiT I" I-''" " r ' i'J ill JV' 'I'l-. L. I ! '! Kl' iJ|: !! I f:'I i'fe 1 i't! !-l IIP.- (Sf*: lili! V'-y i- ' r' i Lh .\t r ! = f d;i. j I w-itft 4 I : +* j : I i -l JI ft: .Mi i m g!T Si' ; fi: : *5*31'*, i.r;.Sfntf--tr*c1 J |ls.c HS-ii! i j- 1 if, Ijfgi .-j J'1 fi h' m* r? ;!' -I H' s-'j'-a1r- - ? i: i*m\ A^ F 'iU$1 tiyl ! jjr:i; j f IU I I\ _ tfc,: ri i . I 5 fe" -1 i.'--5 n 5 N:. i it' t *1 J- Z-m-z * Tt: i- >-'-"-M - I* : i?rfl J 1 'i Ir I n iJ' * a- I h *! r!S 31 I. Ir: i y ii-. !- si ' *- -i -M jF .-it- . 1T. r fc-p i tir' j ii' j t .f V .i-l ;i > >l- Wl I i ij I-: a 'il: r :!I ^ H IS ttlEcH fi 1. ?i 3 -:l ; I i.:' r' : r j;irIk'f.. v::: -I j-rL -<-:iJ- : t = i -i J -a;I !I;I i ->-'p 'J: !l H' h l \ - - cE I Inf. ! !' 1^? jJl i .. ---------- ;^1. ItI : II : -1- - u!;. 1 -il li'-fii- i: " V r: !F ^ w rsi 1 ryi 1 ft Jt j i: Ii- i l!ll! i :'i i !! i ;i ii. I! i! I !:' llI i i !-l ii i-l ll 'l l i-l i i(iij i I i|i! !;i 11 Iii j;M :i I ii!;:- j;: ``l !.i j: ; !:! = i! Ji] : jJ|`I ill Mi ' M i'-Iii1;- >i !:J > i| i'l: Ilfii !'!; ijil- 1i I I'!; i'il'ii Ij!;! ... inn: :'l,! i;: ill': ! Mj' I ! ii.1:.' J Ii: : ! I- l| i j I i ii;i I I i: i ' l.i . I:: i! i i>; ill ilTi: hi -I '! I:i-=i I I,! ]itil i !l !!! ii!i!|:i ill: :i ill1 ill, jj!i:!! I; Ii i;n| l' i i! M In 1 I li'iiii iI .r :|l |i lll| .... r :|;liiii!-i = !i- iS !=jii|. l il i!:lil!ilil::;l!j!!lli 1 ii; T i llliii. i:|ji I Ii!l1l1'1, 'I' I; i' Ml :mii i l!SMii ."I I I'll ill' !li' :!l! ill!: (!'!!!! iji !.; :i; : ll if f-`: il1 i i!ih, !;il !-:ii ::;i; ill' !'!' !li|l i'liln1:;! wainihi!j:;;:! ji ' .J! i,i:ijiI!! 'i|i: :.J J J ll >| illl liill I'iil I I." ii : i; i: J i:: j ' :P' hlii jii ! . -Mi L|!!! ii! 'i! I:' ill M=i; ;:i ffi :h!i i hi I !'!-i I 'l i1i-1 ..1 ii! laboratory, and in vitro laboratory studies. and literature and The model was validated by comparing mice, rats, and humans human and take es and blood, and dependent rates of metabolism. Because of the fundamentals upon models are based, they are particularly useful for high dose-low dose extrapolations as and an example and and Blancato chloride microgram inhaled Subsequently this estimated risk was lowered by Blancato in this instance by PB-PK modeling than classical methods, this is not always the case. For those chemicals which form metabolites that react with DNA, Hoel et al.51 has proposed the use of the concentration of the resulting DNA adducts to follow tumor formation. There is evidence that tumor response is linearly related to the appropriate DNA adducts in the target organ. PB-PK models whose parameters have been accurately determined may be used to help predict the concentration of DNA adducts produced over a wide range of dose concentrations. instead administered dose because its use enables the modeler to incorporate siology, and pharmacokinetics in the model. Use of the "Biologically adducts aids in more accurate extrapolations from high to low doses and from species to species. Resp the biological effective dose (BED) which took several factors into account that are of importance The first of these is the difference in individual susceptibilities to potentially hazardous chemicals. Individual responses to a particular background and variation in the susceptibility and background dynamic randomly an administered (administered summary, it is evident trom the toregomg discussion that the quantit* ; cancer process is following the same familiar course as that followed i the field of chemical kinetics, catalysis and chemical reaction engii ;re are few reaction mechanisms that we understand on an atomic rommite the kinetic rate constants and mass transfer coefficient! Although r / / / 1-1 I* T- ._. I: I( It iI ; i:\ ` f :s } .-r' J: : li j* `blf; mmli- i j rl If i-; r. h;: iis'sfL, . f i^l .J 1 1:1 : ^ a iyiH.ifP j! '- t- . : r u ? * e-'J - nfr'S'i IS 1. fcS'ik, 1 ffr:- 044'- h-j).'34rt St'-' ij m* hHt\i'fili d -!l 4': .;Vi : . : : \ \ !L- n If-B- P . f S-at i hh. Jj E) S' 4I I'J k 4 -I " - ihj;; d[ T I 31' Lii-; i17 VS. tonr -a- :ir H !: 'r!i'=^J-r* H l. 1 J; It 1 !:! ji.cn I i '* j* * m ft H' h +r ! * rf- i.1 [, i'l: !lV 11.-. -j'! 4'!! * 'Jc XI1 i s .j- ir H-S4- i.***.* ilk. - ! J! i : if^i P--i,;: i| r.*! i'.' i\fii - -ft' k &: !r t -J- "-ft f.: N; ll . -p!: fF! T - M'fImtt] A mm t.Jf :"-.'lliiS. .'It -L' V .!- H. ji:l\- !i||;:J| ii: J ..Ii'': ' e* .i 7 5- t1-V i`:r j: hr* It- B i - : : r ' * i'-7' ^ ;j* [ : . :i|:T , :l: ; H, stn-' fj ; i-fi-'j = J- 1 < : '' ;f *:l-U jj;i,i j ; a. :l . !& V: I ! |f I:'- ) r: I r-t I: I I A !j>3 lii jf-i ^F| .%rl kI- 'i ri: V -1' F f -r.fj 1! \ " ' ? r,-.i '-.-iih's-i '!. >Ii-: - '--J JV. rri t'l f. ; M- ' 'k t| ?i r m --J i -"r i-; * K .r*' J *r.t . ,:[ b f ji: f ' A;.-; ;!Un: -i'i. i4: -i 1 J.s J l ? N.ri li/i111; LbflH j- m niTM h! - .'Si | - '*i i;^ 1 r- i'i. . 'b f-; s* J.i I1 I- "J ^|l 1 ;3r ! I: [(-1 rli hi, Tr !E Jig. siidJ^ i 1-- V- 7. !- riii 1 "i .t m J5 U-jj 1 j" J .J : Tj iIif-. " - ?! hl'l.: k :i.frt K!^ JrrAi- :;'K !| 3: ii l : II : . l! J l,I- +J ;p j a r.f . . j r,f:: |.V Ii i! I! I ! piif I: l!! ;I ?! i\ .nil :: ? !|i - r '.h |U i I' I .. 11; f VAB.0001023 11. Hi: considerations alone, we can nevertheless determine these parameters in the laboratory and pilot plants and use them in the design and control of chemical reactors. It should also be noted that the reaction engineering models, like the PB-PK models accurately predict the product response for a given change in the initial concentration of the chemical reactant. Measures of Potency and a Ranking of Possible Hazards of Chemical Carcinogens animal chemicals in chronic standard life span for the species (with appropriate adjustme and experimental procedures as described by Peto et al.53) animals g/kg (the NCI/NTP Program and for all long-term experiments in the published literature. The TD50's for approximately 3000 laboratory animal experiments on 770 chemicals were published by Gold et al.50 These results and the TD50's for additional tests (for a total of 900 chemicals) are listed in three installments of Environmental Health Perspectives from 1984 to 1987. and analog range of potency is more than of chemical which kills 50% of the animals). Other indices for the potency of chemical 4 -p it if . carcinogen have been proposed, and their relationship to the TD50 have been presented by Gold et al.54 animal experiments for the determination rmally swamped many metabolic processes and other defense mechanisms at i !! i: 3i : tii ! j- i which humans However, to human exposure information in the TD50 in the definition of an .man Exposure/Rodent Potency dose)(100)l. More HERP human exposure (mg/kg/day) x 100 TD50 (mg/kg/day) g/kg/day denote the milligrams of the dose of chemical per kilogram < lay. [This definition of HERP is called HERP(in %) by Ames et al.53 f the TDso's for 975 chemicals in rodents.] he nonlinearity of the functions and the other problems, enumerated he extrapolation from animals to humans, the HERP cannot be reea any measure f1- and 27 j 100 ng TCDD 0> u on o 2 -O > cn CC a XI 00 * g *. 1 MS 10 MS 100) ig Actinomycin D Aflatoxin B1 Bis-(chloromethyl) ether Sterigmatocystin DBCP Diethylstilbestrol Procarbazine. HCI >% 4) o= X5 1 mg a3n* * ^2 TeJ e- 03 4Oc> 10 mg av>> o *cE *o- .E 100 mg *3 Q oC3 Xc3 1g ea |/) - *o Q.- <J H c -o 10 g EDB 2-AAF Auramine-O Aniline. HCI DDT 2, 4, 6 -Trichlorophenol Metronidazole FD & C Red No. 1 FD & C Green No. 1 Figure 19. Range of carcinogenic potency in male rats as measured by the TD50 index . [From Gold, L. S. et al., Environ. Health Persped., 58, 9(1984).] RELATIVE RANKING OF POSSIBLE HAZARDS Relative Ranking =1 3 i Peanut butter 3 sandwiches Figure 20. Three and one-third peanut butter sandwiches have a Relative Ranking of unity. RELATIVE RANKING OF POSSIBLE HAZARDS Relative Ranking = 28 1 Beer (12 oz) Relative Ranking = 160 I Phenobarbital sleeping pill r Figure 21. One twelve ounce beer has a Relative Ranking = 28. Figure 22. One phenobarbital pill has a Relative Ranking = 160. i 1 l 1 1 1 j1 I 1 l M J \ r 1 1 j I\ i* H' \i .? I if ,* ji 1 I I I. i' 1 1 I I I I I I I I I t -U T r 11 j 1 1 1 11 \1 1 1 i11 IH I I! i I i VAB.0001023886 i i Instead of expressing the possible hazards of chemicals and other substances in terms of HERP's, they may be ranked relative to any one of the others. If, for example, the possible hazard of consuming one raw mushroom daily, or one basil leaf daily, or three and peanut butter sandwiches daily [each of which corresponds to a HERP = 0.1], is taken a basis, then the possible hazards of other substances may be ranked relative tc Figures 20 i same surroundings than is man. Although we are exposed to a a this should not be taken as a license to make significant additions to cannot, in fact, technically or otherwise all chemical carcinogens to zero. Thus the level of reduction becomes a risk management problem which has been dealt with by Deisler in a series of papers.56-60 The approach recommended by Deisler for dealing with this problem is to first select a set of very desirable but realistically achievable, quantitative risks, which broadly applied would achieve the following : "(1) cause the deploy resources cancer as soon and foundation for continuing risk reduction and control; and (3) as a desired, long-term end cancer cancer level as near to insignificance cancer ii I! I1 I '!. I C! I I;' II l I| l l i! l I:' I I!! li I' ill ii I ii H* j. N Kla i i It ;! , i L I:- i' i! I?j iii Mii! IiM !I ii ii ii ; i. ill |i - :i. !! iii i- *:i I : .1 I' i: i i .i I ' l; i ! !| j ii I !! ii '!; ! < I ! Ii i i! I![ !i ! ( i:r Ii in ! [: : ii I i !i I I- f III : , :I Cancer Mortality along the Upper Texas Gulf Coast I l:: The determination of cancer mortality resulting from environmental exposure is difficult because of the many "confounding factors" such as occupational exposure, smoking, and l'. !' ( migrating populations. I I, The "111 Winds Study" by Molinari61 attributed the higher cancer rates (than the U. S. I1 I II average) in the Texas Gulf Coast Counties of Chambers, Jefferson, Galveston, and Harris i:- - ii to the fact that each contained or was downwind of one or more petrochemical plants. While this study was faulted by its methodology and strongly criticized by epidemiologists, cancer I,: i;. i:| I'1 ii I ;i: I I; I :: white males during the Smith et al.62 cited one major epidemiological cancer However, the principal investigator smoking and occupational I!- I. I l : f li !i ! .1 l I: Ij Ii ! ! ! :I 1 !. i' ! ;i! I. adequately controlled, and if they had been Jl. I r W"i of air pollution would have dropped less than 1%. This is consistent with an EPA study, in : . I_ called "the 6 month study"63, which estimated the potential of air pollution for causing :i i I1 s.1 : :| l'* i cancer in the U.S. population at 1,700 to 2,000 cases per year or roughly 0.2%. :l i I ' I- I; I-. Because of the continued concern of the citizens over the health consequences of exposure to I ii !; ! j. ambient air contaminants, the Texas Air Control Board (TACB) commissioned the "Gulf ! III I| I! II i I; ii 29 I> : I-. .! ii I! !I .i.i - I ! 'i ! I ! |i i ' : .i !!: !I jj i : !'!! !I i; i ii !I il ll i ii !I i! I !!l; i i 11 i i i.. !iI l:! -j! I l ill I i'.i: ;|:j. ii: ri;: I" I !l li I nil I I! i: I I i i'Ttt j;: 'in :l I:--! |l I: ! I! i i! ; ! ! i ii'l ! i ir! !! i !! I ! Ini l I: I. I i i.I:: j I- i I ! ' , iKHMli Plilii!! :!! ; ;i: ! ;'i! i Mi! !vi 'iI| !ji..iMll: i.. Iii ii U. ! !"! I I Ml . I i I! 11 IL I! 1 ;! i1 .11 I Mli;: ill II; II III; = iiiii'lj llii-iiili lili^lli.. : I; i: l .:! l' :' I i! I ii jl IHi 11! .i:! ill I. Hi ! ri: i! Is:. ! i ill iii .' ii:'Iji:j j=!' :ii ooo o 1 O 1Lo fol 1o ho oi1raQn1i~o~inr~foilo on Q rcnr- 6 ro I II i:i li II 1 i li IIi Coast Community Exposure Study" (GCCES). The Final Report of this study by Rogers et al.64, released in 1988, presents the results of a quantitative study of the environmental contaminants detected at 6 Texas monitoring locations: Austin, Beaumont, West Orange, Cloverleaf (Harris County), Cloverleaf Q. A. (Harris County), and Texas City from October 9, 1985 through September 26, 1986. The air samples collected at the monitoring stations were analyzed for the chemicals shown in Table 10. The quantitative results obtained are shown in Tables 11 and 12. The conclusion of the report was that "the data showed no indication of a health risk. The levels of all substances which were detected were within the range of levels considered typical of heavily-urbanized areas across the United States."64 The highest concentration measured for any pollutant was benzene, and at the measured upper bound of 18 micrograms per cubic meter which corresponds to a Relative Ranking of 0.0839, which is 12 times smaller than the Ranking of 1 for the human exposure to the natural carcinogens in a diet containing one basil leaf or three and one-third peanut butter sandwiches, daily. This section is concluded by a brief description of the most recently published (October, 1988) epidemiological study of Harris County. In this ecological analysis, Buffler et al. 65 took several confounding factors into consideration which were not considered in earlier studies. cancer rates in Harris counties led to the initiation of this study which examined the air pollution-lung cancer mortality relation for white males in Harris County, Texas, 1979-1981. Factors taken into account were median age, two social and demographic factors (family life cycle an age-dependent smoking index, and suspended particulates. Air pollution was not demonstrated to be a strong determinant of lung cancer in that the presence of air pollution accounted for less than 5% of the total intraurban lung cancer cancer analysis. Their final conclusion cancer can cancer cannot be tested until other stronger individual risk factors The Houston Regional Monitoring Program This is a continuing program which is supported by 35 companies. Samples are collected at 6 locations and analyzed for 173 chemical compounds. The results obtained thus far mirror those reported by the Texas Air Control Board in the Gulf Coast Community Exposure Study.64 Results of a Study of Liver Cancer Rates in Brazoria County As a consequence of a study by Hoover and Fraumeni66 in which a 10% excess mortality rates above those for the U.S. average was found for chemical-industry countries, a study by Buffler et al.67 was sponsored by the National Cancer Institute. Thirty-nine cases of :l:i ,i i: I .il i: ;I I ! I:. ! I .."'I !i I i: i;: i .1 ' i! ii Mil .I !ii . I. I i l I| Ii i:|l' : I' j ; i Til I I! :::i :i i! l! ii . i. : 'i !i"ii i ti 1.1 ! -I :i I I'! I ; ;, ' .1: i: :i ! I:'! i I !! i i; i ! I :: It- ;i i J A' A ll : ! iI l! 1 i>lii 1 Irtr !i i ll %il Nil -I U. 'ff 4 ! iY-tl r it i . u: ] S: :* t *> El i i' Iz.l fitI &: ,-r Hi mJ-Hl ;i &- |M ! . -3i j is i 'h?: 11 .i -*r / ili'lIiii !' i:'i J 1i J1^F:!l a. : 1; i' I - Lit iill! ,L. * 1 *\ f-* fc, it - a Ik I - F;l it: m ! ' it. li 1 ,+ ir 1t I*p: t I I- i'\ l IF \ if I ? ;i :| !r IJ 1 i. Ai ll. i\nli<: rk- i Ih " I 'I I : :i l l1 -I t-s! I rtFi mHibiFii::ii' F- i .ll fr f I: ii\t i'IIf j' ! Hi 13 i;J|;' I li ll k Ji |!i' .! !:'il = ir V \!j ! -I fi ij au r.-T* ll r !- .* I -! Hi-fi' ill*'e : i ,. i 1.I 'i- < I* :=ani -t il-ci : i = l z'A -Tl t ?l r. U-t ! n~ 1 H$Ii. \i / i Ml . .. -'i i|' li !I ! I' I I'll! I> ij : i i I III I *:: I il i m: 'll h; i i; ii ; . HI- :| ! l| :I i'! IM !:;l, ; ;! I-; T ; i: ! !! ;! . i ,1 ; i. II.|- it I ,1 i:n iMiji ;:ii ;M i;l! liil i- Ml;j i . hi: : :i; . ii il! I ! il: M": :i ! ! liS-ii'i: i ;Mlii|: j i I. I !: .;i! Mil IM!!i! (it I I-! I LL! I[,!j Ti i i;i, f mu! I I 'I li: ;!|ll :i:i'i;| i l' :l!!l lIlliT m; a ,I ?>]' liver cancer were observed in white males, the group in which the carcinogenic effect of occupational exposure to chemicals would be expected to be observed. The actual number of cases observed was too small to establish an association with occupational chemical exposure, although the liver cancer mortality rates were slightly higher for Brazoria County than they were for the U. S. The EPA TEAM Study (The Total Exposure Assessment Monitoring Study68) \ The results of an extensive five year study by EPA (reported in 1985) in which scientists a concluded that, contrary to popular belief, people living in heavily industrialized areas containing petrochemical, paint and plastic processing plants are not subjected to greater exposures to the commonly identified toxic chemicals than are people living in less industrialized, or even rural areas. This conclusion was based on studying 355 people in the highly industrialized cities of Bayonne and Elizabeth, N.J., 25 people in the highly industrialized city of Greensboro, N.C., and another 25 in rural Devils Lake, N.D. A further significant finding was that people are exposed to far greater concentrations of toxic chemicals indoors than they are outdoors, even in those cities where plants that manufacture or use these chemicals are located. This finding has also been confirmed by European studies. By use of both indoor and outdoor monitoring systems, the EPA investigators found indoor levels to be two to five times greater than outdoor levels for the commonly identified toxic chemicals. At highest exposures, the indoor levels were up to 70 times greater than outdoor levels. Since people spend up to 95% of their time indoors where the pollution levels of toxic chemicals are far higher than they are outdoors, one comes to the obvious conclusion that our present method of basing exposure estimates on fixed-station monitors located outdoors does not accurately reflect the total human exposure. k. * Industrial Epidemiological Studies Industrial epidemiological studies are characterized by the "healthy worker effect," which \ can be attributed to several factors. The conditions for employment require that people entering the work force be in good health. The nature of the employment leads to workers I establishing a healthier life style [regular routine for work, rest, meals] than is followed by the general public. Workers also receive better medical care than does the general public. Typical of the results of industrial epidemiological studies are those published by Dow's Epidemiological Department. These extensive studies, numbering over 60, involved piany highly publicized chemicals, and except for those workers who had been exposed in the past to arsenic, asbestos, and vinyl chloride, total mortality rates as well as cancer mortality rates were less than those for the surrounding neighborhoods. Extensive studies, published by Union Carbide Department of Epidemiology found an excessive cancer mortality for only one subcohort of workers, a group which had worked in vinyl chloride plants that are no longer in existence. 32 !; : i 'll j' i' li Ii III: i:| In a series of studies conducted by the Medical Department of Phillips Petroleum Company, no job associated cancers were detected in the carbon black production workers and no job associated leukemia was found in the refinery workers. Typical of industry's efforts in the area of epidemiological studies is the following report from Exxon's Department of Medicine and Environmental Health : "Based upon 137,702 person-years of observation, the mortality experience of workers at Exxon's refineries and chemical plants in three areas of the United States was found to be generally lower than that of the U.S. population." Du Pont established an epidemiological section in its Medica time, the company has conducted more than 80 special studies and scientific papers. wide registries for mortality. cancer incidence, coronary heart disease, and cerebrovascular accidents. Shell Oil Company has performed several epidemiology studies of its work force and elevations Investigations of these mortality Shell encourages publication of studies and routin and federal authorities of all study results. Shell a industry studies involving more than one company. cancer mortality rates cannot cancer can and better medical care), General forms of cancer r I ' : ii ; i I- I ! ('; il I !; i : :| Ii l:!. 1I i I. ! I i i! ri! ii!i l! : ,1 :! i: n: i !! I M -| `I ri:i ; II ii:!! i !' lliiili I; C I : I. I ij: :l i| !l` r :! i !' I! I 'ill ii. !: !i. -r-ii i) II I II ;i:l I.. ! Ii i ill hi I! .1 .1 i :i Ti ii i' i: i ! I: iI i| f.M I ! i ri i !I !: ' ! :!;i !i " i I; :i l> I :i i ii I- i- i ii ` ! Ii In Ii1. . i : ;! ! i ;l I ll '! i! i ' !' il. :!; il " .i i . .li ii ! Ii :'l il- : .`i ! 'i Ii :.lI II.i II I l hh i in l! !!i; :!i!l cannot cancer Prioritizing our Efforts and Expenditures Our problem is one of putting the reduction of cancer mortality caused by occupational hazards (4%) and environmental pollution (2%) in perspective. Our present rate of increase in industrial environment costs is depicted in Figure 23. We are all in favor of a clean livable environment; this may not be a uniquely risk-free or unaltered environment, Where do we stop -- how much is enough? Even if we closed all chemical plants, eliminated all automobiles, alcohol, and all other possible sources of occupational hazar and environmental pollution, we would still be left with an estimated 90-+*% of the cancer mortality. Instead of spending more and more of our national resources on the impossible go; of totally eliminating environmental risks, should we not move faster on a broad fron can risks and mortality 10-fold cancer research? Ml ir ir+ ill. !i!i ! Ii 'I II .1 >i i ;i i I Ii'! ii! I*' l: II ll ill M .i i i I' ll- hi .1; li: I- II li I- I: ! i- iI !.-! I: |Mi il V1 l ii'l ! ! li i Jf i Mi: I ii i: il li I: 'i i. j . li'i il I i: than many would have us cancer caused by use of tobacco and asbestos cancer mortality can N! Ii ! ! Hi, i. i III II ! :i ! | / / 11 - :il. V : i ; In? | If P. n _r hirj .i : MMi S#j1 r!--n.- jShriVf h'r- i !j i ri. I- - ii ii fill: i;l i * It i|-T*" i It!Si >. II '-..i n- : ` ii hi |h*T '`I'r'l-Sp m'! ,.'? {+!'"i-v ; ij|i- : ;,ys rvm isgin ii Ii arj-ii i "I Tii 11 I sj H fSfS Ii .E=' ii'. J1i_=pr H feSi!' >ili ;kJi i- ,ri to I'nl i. <: : I pr.l- tl 'I i''i cli J. t.`.i Ji Ip il'-i!' ii1 1j 'll Hi ifl 'ti' .Ifil hm;; iFJ - i: 1. .1 - -i J < r' ! H- ;{js (-15;: +!* ii - il `t ri 1. ii 3. r4: C" r in M, . 3i r-- I !I T:.r .V m ;ku Mii; ill -i II im rn ll r jr'ji. vm ir._- MrN*. M'A sl?L fc!-' w6ft s il! ' i !I ll'(:. i! m .Hi = 6f A: Ii !I i'll n i I li.'.ll !!;l ' lii! !!!;!!! I! !J i:i! :: ii il ' = i i I!: f . I i'l'j- I il ijliM i ' iii::! !!! i I; : 1"-I ,* i ; l! M : li*. i:i!'i l :;ll Iji* ;n !i ;i| l:!i n-l! I .1 ! I ;!: I, l!!! ;;i ii" fill Mu' !!!! "Ml.: hI lil :i -i iiuiir:i;:Hi! i l.'1: !i;l : :i '! j!!i: !:! Ij: j;!'iiii=iii:!'!!l :I' r!i:| !m!!!|:I I!-':' ! I'l i1:!;!!' ll": Ill ii: r : 111; 111 li!?;: Hill lii'-'h;- iJMiMii .-,ii;;i ! I!.;''' h'l.iii r i ; jlj i:.V ii'ii-'i ;; !!l:l: :i! ( .il i|.: i 11 'l" ill and gvrv/vt tt ------- ---------------------------------- --- ----------------------------------- ^ there is a reason for renewed hope, and cancer research. For example, an As a. studv bv Wen-Hwa Lee, Professor WHICH suuggggecsstias ttihicawt. aa genetically e----n-og-i-n---e---e---r--e---d-- virus carr~ying~ a cancer , i i L >1 , v * to prevent the formation of malignant cells. *L ee said itihe resuilti s suggest__________ that this technique * COU1U uc UBCU w - * __ l ----- ---------- o-------- it_u__m__o__r4\ao+ crrnwincr ; t.n , Cfills . , 1. n that grow normally. He said this technique holds promise for development within five years. 1980 1985 1986 Figure 23. Environmental costs for Texas industries are 100 % above those of 1980. [Courtesy of Dow Chemical Company.] Furthermore, the quantification of the cancer process through the use of pharmacokinetics, introduced in 1973 by Teorell69, is a rapidly advancing field in which the well-known principles of chemical kinetics are applied to describe the effect of chemicals on animals and humans. Recent advances in this area by numerous authors including Gehring and Blau42, and Andersen et al.44 give renewed hope for a better understanding and quantification of the cancer process in the not too distant future. We must find a way to strike the proper balance between a clean, livable environment and an unaltered environment. The balance is between achieving and maintaining a livable, viable environment and the existence of an industry of the magnitude required to provide the necessary benefits for a populated world. Neither super safety, nor environmental carelessness is the answer. To solve these problems will require the sincere cooperation of the general public, industry, and government. 34 REFERENCES 1. Doll, R.and R. Peto, "The Causes of Cancer: Quantitative Estimates of Avoidable Risks of Cancer in the United States Today," JNCI, 66(6), 1191 (1981). 2. Higginson, J., "Perspectives and Future Developments in Research on Environmental Carcinogenesis," in Carcinogens: Identification and Mechanisms of Action, A. C. Griffin, Ed., Raven Press, New York (1979). 3. Higginson, J. and C. S. Muir, "Environmental Carcinogenesis: Misconceptions and Limitations to Cancer Control," JNCI, 63, 1291 (1979). 4. Cole, P., "Cancer and Occupation: Status and Needs for Epidemiology Research," Cancer, 39, 1788 (1977). 5. Wynder E. L. and G. B. Gori, "Contributions of the Environment to Cancer Incidence. An Epidemiologic Exercise," JNCI, 58, 825 (1977). 6. United States International Trade Commission. Synthetic Organic Chemicals U.S. Production and Sales,Washington. The Commission: Supt. of Docs., U.S.G.P.O. (1938-1985). 7. U.S. National Center for Health Statistics and U.S. Bureau of Census (1970). 8. Burack, W. "Lies, Damned Lies and Statistics," Medical News, Aug. 6 (1979). 9. Schottenfeld, D., "The Epidemiology of Cancer: An Overview," Cancer, 47(5), 1095 (1981). 10. Davies, J. M.,S. M. Somerville, D. M. Wallace, "Occupational Bladder T\imor Cases Identified During Ten Years Interviewing Patients," Br. J. Urol., 206, 1356 (1976). 11. Hoover, R., et al., "Progress Report to the Pure Food and Drug Administration from the National Cancer Institute concerning the National Bladder Cancer Study," NCI, unpublished, (1980). 12. Carson, R., Silent Spring, Houghton Mifflin Co., Boston, MA (1962). 13. Meadows, D. L., D. H. Meadows, J. Randers and W. W. Behrens III, The Limits of Growth, A Report for the Club of Rome's Project on the Predicament of Mankind, Potomac Associates, New American Library, New York (1974). 14. Efron, E., The Apocalyptic Cancer and the Big Lie, Simon and Schuster, New York, (1984). 15. Rather, D., "The American Way of Death," CBS, transcript (1975). 16. Segi, M., "Cancer Around the World," Cancer Statistics, American Cancer Society (1973). 17. Ca-A Cancer Journal for Clinicians, "Cancer Around the World 1970-71", American Cancer Society, 27(1), 38 (1977). 18. Corbett, T., Cancer and Chemicals, Nelson-Hall, Chicago, IL, (1977). 19. Bishop Jr., J., Panelist on "Face the Nation," CBS, Transcript, (1976). 4 20. Agran, L., The Cancer Connection, Haughton Mifflin Company, Boston, Massachusetts, (1977). 21. Epstein, S. S., The Politics of Cancer, San Francisco, Sierra Club Books, (1978). 22. Higginson, J., "Present Trends in Cancer Epidemiology," in Proceedings of the Eighth Canadian Cancer Conference, Honey Harbour, Ontario, pg.40 (1968,1969). 23. "Cancer, Pollution and the Workplace", Special Report by the American Industrial Health Council, 1612 K Street, Washington, D. C. (1983). r 24. "Estimates of the Fraction of Cancer in the United States Related to Occupational Factors," Report Prepared by the National Cancer Institute, the National Institute of Environmental Health Sciences, and the National Institute for Occupational Safety and Health, September 15 (1978) 25. Higginson, J., "Cancer and Environment: Higginson Speaks Out," Science, 205, 1363 (1979). 26. Miller, E. C. and J. A. Miller, "Biochemical Mechanisms of Chemical Carcinogenesis," in The Molecular 1 MJ; I:! i !l I!! Ml Ji III F il I I F t- 1 I ii I! f i K* II E l s !i M i! ! HI I i! ii i III ! II fl I 1 ii !'' I i: -i; : m-; I- |! : I'!1 i!i| ''ill Il i ! I I: il!:l i :! :i ii ii s . :s ii i.iii Hi :r i i. ill! Hii: I II'i :I !! I : i , ii: ! ! ! ii chilli .& i!i I!' MM"! i jij | - j i ! 'll MU'Nil ! i;: I i . ii; '!l j ill!: ii "ill! ii! !I ;! !'!il! ! I ;r ! * I * :!'i; is!:; il- ! i1 I ill. | -I .!' I Hi iI m! i iji'l i|!liji;i ili'i .ill!1 i i mm :! i;j!11 !!i!:! i ;'i.ii.i liil;:!!1!' Hlii I -ji ij! I:' ! .i!i!: Ii I! Ml li: ii ' 'ilii ilii ifi; ii i. Biology of Cancer, Harris Bush, Ed., Academic Press, San Diego, California, pg. 38 (1974). 27. Berenblum, I., Historical Perspective, Carcinogenesis: A Comprehensive Survey, Vol. 1, pg. 2, Raven, New York, N.Y. (1978). 28. Berenblum, I., Sequential Aspects of Chemical Carcinogenesis: Skin, Cancer: A Comprehensive Treatise, Vol. 1, pg. 323, Phenum, New York, N.Y. (1975). 29. Ames, B. N., W. E. Durston, E. Yamasaki and F. D. Lee, "Carcinogens are Mutagens: A Simple Test System Combining Liver Homogenates for Activation and Bacteria for Detection," Proceedings of the National Academy of Science, 70, 2281 (1973). 30. McCann, J., E. Choi, E. Yamasaki, and B. N. Ames, "Detection of Carcinogens as Mutagens in Salmonella/Microsome Test Assay of 300 Chemicals, in Proc. Nat. Acad. Sci., U.S.A., 79 (No. 12), 5135 (1975). 31. Ames, B. N., "Six Common Errors Relating to Environmental Pollution," Regulatory Toxicology and Pharmacology, 7, 379 (1987). 32. Moolgavkar, S. H. and A. G. Knudson, Jr., "Mutation and Cancer : A model for Human Carcinogenesis," JNCI, 66(6), 1037 (1981). 33. Wilson, J. D., An assessment of Low-Exposure Risk from Carcinogens : Implication of the KnudsonMoolgavkar Two-Critical Mutation Theory, Accepted for Publication in "Biological Based Models for Cancer Risk Assessment", Pergamon Press, (1989). 34. Armitage, P., and R. Doll, "The Age Distribution of Cancer and a Multi-Stage Theory of Carcinogenesis," Brit. J. Cancer, 8, 1 (1954). 35. Trosko, J. E., and Chia-Chong Chang, "Nongenotoxic Mechanisms in Carcinogenesis: Role of Inhibited Intercellular Communication," Carcinogenic Risk Assessment: New Directions in the Qualitative and Quantitative Aspects, Edited by R. W. Hart and F. D. Hoerger, Bambury Report 31, Cold Spring Harbor Laboratory, 139(1988). 36. International Agency for Research on Cancer (IARC), IARC Monographs on the Evaluation of the Carcino genic Risk of Chemicals to Humans, IARC: Lyons, France, Supplement 4, (1982). 37. Wilkinson, C. F., "Being More Realistic about Chemical Carcinogens," Env. Sci. Technol, 21(9), 843 (1987). 38. Environmental Protection Agency, "Potential Industrial Carcinogens and Mutagens," prepared for the Office of Toxic Substances by Lawrence Fishbein, Washington D. C., May 5 (1977) 39. Hsieh, D. P. H., J. J. Wong, Z. A. Wong, C. Michas, and B. H. Ruebner, "Hepatic Transformation of Aflatoxin and its Carcinogenicity," in Origins of Human Cancer, Hyatt, H. H., J. D. Watson and J. A. Winsten, Ed., Book B: Mechanisms of Carcinogenicity, Cold Spring Harbor Laboratory, New York (1977). 40. Weisburger, J. H., "Bioassays and Tests for Chemical Carcinogens," Chemical Carcinogens, Ed. C.E. Searle, American Chemical Society, Washington, D.C., (1976) * 41. Schneiderman, M. A., and C. C. Brown, "Estimating Cancer Risks to a Population," Environmental Health Perspectives, 22, 117 (1978). 42. Gehring, P. J. and G. E. Blau, "Mechanisms of Carcinogenesis: Dose Response," J. Environ. Pathol. Toxicol, 1, 163 (1977). 1. 43. Reitz, R. H., and P. G. Watanabe, Mechanistic Considerations in the Formulation of Carcinogenic Risk Estimations, Banbury Report 19, Risk Quantitation and Regulatory Policy, Cold Spring Harbor Laboratory, 241 (1985). r 44. Andersen, M. E., H. J. Clewell III, M. L. Gargas, F. A. Smith and R. H. Reitz, "Physiologically Based Pharmacokinetics and Risk Assessment Process for Methylene Chloride," Toxicol, and Appl. Pharmacology, 86, 341 (1987). 45. Clewell, H. J., Ill and M. E. Andersen, "Risk Assessment Extrapolations and Physiological Modeling," Toxicology and Industrial Health, 1(4), 111 (1985). w 46. Miller, E. C., and J. A. Miller, "Searches for Ultimate Chemical Carcinogens and their Reactions with Cellulai Macromolecules," Cancer, 47, 2327 (1981). 47. Russell, W. L., E. M. Kelly, P. R. Hunsicken, Bangham, S. C. Maddux, and E. L. Phipps, "Specific-Locus Test Shows Ethylnitrosourea to be the Most Potent Mutagen in the Mouse," in Proc. Nat. Acad. Sci. U.S.A., 76, 5818 ((1979)). 48. Russell, W. L., P. R. Hunsicken, D. A. Carpenter, C. V. Cornett, and G. M. Guinn, "Effect of Dose Fractionation on the Ethylnitrosourea Induction of Specific Locus Mutations in Mouse Spermatogonia," in Proc. Nat. Acad. Sci. U. S. A., 79, 3592 ((1982)). 49. Singh, D. V., H. L. Spitzer and P. D. White, Addendum to Health Assessment Document for Dichloromethane (Methylene Chloride). Updated carcinogenicity assessment of dichloromethane. EPA/600/8-82/004F (1985). 50. Blancato, J. N., J. Hopkins and L. Rhomberg, Update of the health assessment document and addendum for dichloromethane (methylene chloride): Pharmacokinetic mechanism of action, and epidemiology, External Review Draft, EPA/600/8-87/030A (1987). 51. Hoel, D. G., N. L. Kaplan, and M. W. Anderson, "Implication of Nonlinear Kinetics on Risk Estimation in Carcinogenesis," Science, 219, 1032 (1983). 52. Sielken, R. L., Jr., "Cancer Dose-Response Extrapolations," Environ. Sci. Technoi, 21(11), 1037 (1987). 53. Peto, R., M. C. Pike, L. Berstein, L. S. Gold and B. H. Ames, "The TD50: A Proposed General Convention for Numerical Description of the Carcinogenic Potency of Chemicals in Chronic-Exposure Animal Experiments," Environ. Health Perspeci., 58, 1 (1984). 54. Gold, L. S., C. B. Sawyer, R. Magaw, G. M. Backman, M. de Veciana, R. Levinson, H. K. Hooper, W. R. Havender, L. Bernstein, R. Peto, M. C. Pike, and B. N. Ames, "A Carcinogenic Potency Database of Standardized Results of Animal Bioassays," Environ. Health. Perspect., 58, 9 (1984). 55. Ames, B. N., R. Magaw and L. S. Gold, "Ranking Possible Carcinogenic Hazards," Science, 236, 271 (1987). 56. Deisler, P. F., Jr., "A Goal-Oriented Approach to Reducing Industrially Related Carcinogenic Risks," Metabolism Reviews, 13(5), 875 (1982). 57. Deisler, P. F., Jr., "Dealing with Industrial Health Risk: A Step-Wise, Goal-Oriented Concept," in American I Association for Advancement of Science Special Symposium, No. 65: Rtsfc in a Technological Society, C. Hohenemser and J. X. Kasperson, Ed., Westview Press, Boulder, CO, chap. 15 (1982). 58. Deisler, P. F., Jr., In: Reducing the Carcinogenic Risks in Industry, Ed., New York and Basel, pp 135-138 (1984). 59. Deisler, P. F., Jr., In: Risk Analysis in the Chemical Industry, Chemical Manufacturers Association J Symposium Proceedings, Government Institutes, Rockville, MD, pp 14-27 (1985). 60. Deisler, P. F., Jr., "The Risk Management - Risk Assessment Interface," Environ. Sci. Technoi., 22(1), 15 I (1988). 61. Molinari, G., "The 111 Winds," U. S. House of Representatives, District Office Publication, Fort Wadsworth Building 203, Staten Island, NY (1985). 62. Smith, V. L., J. Wiersema and J. H. Price, Jr., "A Discussion of Epidemiological Studies of Lung Mortality Rates with Special Attention to the Texas Upper Gulf Coast Area," Staff Report, Research Division, Texas Air Control Board, Austin, TX, August (1985). 63. Thompson, V. E., A. Jones, E. Haemisegger and B. Steigerwald, "The toxics Problem in the United States : An analysis of Cancer Risks Posed by Selected Air Pollutants" [Based on a draft report of the "Six Month Study"]. J. of Air Pollution Control Association, 35(51,537) (1985). 64. Rogers, B., J. Wiersema, S. Price, T. Porter, G. Dean, T. Driscoll, J. Gise, M. Jenks, K. Kilpatrick, J. Lindgren, C. McCauley, J. Panketh, V. Smith, D. Sullivan and N. Zare, "Final Report: Gulf Coast Community Exposure Study," Texas Air Control Board, Austin, TX, March (1988). 37 ;:; 1: I! > !11 I! I!: I ii-ilii I !; ! II,iill: I! In I ,1 ii ! ini III I ilii iI lliili: 1 Mi Ml i |li! ! h I! I ! i ; m : I!:j!j li- ! : 11!'! I j Mill! 1 : i;iii; I;!f; 1' 1 f - f f; | 1 piiiilli !i:i '!i ilii!;!! 'Mill !'! :|j!i;||1 !: ... I: I 1; ! 1! iii i ! : i n: II |: I Ml; 1 1 ! l. : li 1 m ;1 '!! !J I !!i:: .11 1l 1i;1 1. 1 Mi I! ! I: I II Mil II 1 li ! III, i li Mi I 11111 i iii; in!, 1 I: 1:1 ii in .1,1 1i!: !liM. ! ! iii ; !i i. iii ! Ilili I\ ;i ;i T i 1 I: !' :'i;! I; ..! !! li ;l;:i : I: 1 i11 Hi. ;|! I' !! t :I !!: \ !l M: j|i jilljliSII j!N]!:i : ! i ' !l:; M! i.ii:. &J J;;1 I: I: ! I: !1 I! ! ! III! II I I I ll! III .! 1 ;:il: 'I': !. ; 1 i ' I: i 1 i r .1: 1I ! .1! i: I Mil: 1 : 1 ii'!! :| I !i : l. = ! M: II I iI I I!l!:i : I 11 iM 1 h1ii!l ! i 'I !l! k :l "1 1t li i ill I!! !: 1 Ml 1 !i: ! III: I i li'! I l: :l> I' \. ::n : :;i ! 1I:. ; ! :l : I. 1; I I |!|i! ! i ' 1 i I = :l |!'l'i ili :; !': 1! 1 -.jlilii :ij! 1 Ml mi! 1 I I: li hi ii i 1 i!: ll:i ii 1 if 1. - $ 1 65. Buffler, P. A., S. P. Cooper, S. S. Stinnett, C. Contant, S. Shirts, R. J. Hardy, V. Agu, B. Gehan, and K. Bur&u, "Air Pollution and Lung Cancer Mortality in Harris County, Texas, 1979--1981 , 128(4), 693 (1988). i 66. Hoover, R. and J. F. Fraumeni, "Cancer Mortality in U. S. Counties with Chemical Industries," Environmental Research, 9, 196 (1975). 67. Buffler, P. A., B. J. Divine, S. S. Stinnett, S. M. Wood, T. J. Mason, T. t. Kuo, N. Snyder and J. A. Jones, "Occupational Exposure and the Risk of Primary Liver Cancer in a Chemical-Industry County," N.C.I., No.l., CP91037. I 68. Ember, L., "Toxic Chemical Levels Higher Indoors than Out [Based on the TEAM Study]," C&EN, 22, June 24 (1985). 69. Teorell, T., "Kinetics of Distribution of Substances Administered to the Body: I.The extra vascular modes i of administration," Arch. Intern. Pkerroaco/ojy, 57, 205 (1937). I I1 i i 4 9 \ H 4 * r ! i j |L, N I l i l i i I i .1 !| i i i I i i| i '! I i ii j i i i i i I i i .i j j j- i i i 3 i I.' r i i i; i i. i i i i Hj i i ii i l i i r i I i l l i i r VAB.0001023896 ' J 4 i J i' I. J } APPENDIX A CALCULATION OF AGE-STANDARDIZED RATES Age--standardized death rates used by Doll and Peto1 and most other authors is defined as the weighted average of the 18 separate age-specific rates. The age-specific death rate is defined as the death rate from some particular type of cancer (say, lung cancer) in a particular population (say U. S. males) in a particular narrow range of ages. The 18 fiveyear age ranges used by Doll and Peto are: 0--4, 5--9, 10--14, 15--19, ..., 75--79, 80--84, and 85 and over. The age standardized rate computed obviously depends on the weights selected. For example, if positive weights were assigned to the first 13 age-specific male stomach cancer rates (those for 0-4, 5-9, ..., 60-64) and zero weights for the last five ranges (65-69, 70--74, ..., 80--84, and 85 and over), then one would obtain the age standardized stomach cancer rates among men under 65 years of age. To demonstrate the age-standardization procedure, the male cancer rates for the year 1977 are age-standardized to the U. S. 1970 population. The U. S. male cancer deaths for each age group for 1977, the male population for 1977, and the 1970 population distribution per 1,000,000 people (all taken from the U. S. census) is shown in Table A-l. From column 3 of Table A-l, it is evident that for any age range i, the 1977 male cancer death rate is age-adjusted to the 1970 census (per 100 million people) as follows: J _ (^*,1977 ^ "*.1977 = l ------------- I ^*,1970 \rc,1977/ ^*,1977 = ^*,1977 = **1,1977 = 1970 = number of U. S. male cancer deaths in range i in 1977. number of U. S. male cancer deaths in age range i in 1977 after age-adjusting to the 1970 U. S. census (per 100 million people). number of U. S. males in age range i in 1977. weight for range * = number of people in range i per 100 million population. The total U. S. male deaths due to lung cancer in 1977 [age-adjusted to 1970 per 100 million people] is the sum of the entries of column 3 of Table A-l, or the sum of the <^,1977's. Since there are approximately 110 million males and 110 million females in the U. S. (with 10 million of each being over 65), the basis of 100 million people for the 1970 weight factorJis a convenient basis because the resulting weighted cancer deaths are approximately equal to the actual number of cancer deaths. The age-adjustment of the deaths for different years relative to one particular year, such as 1970, makes the comparison of trends more meaningful as discussed by Doll and Peto. The point on the curve in Figure 2 for cancer mortality of men for the year 1977 may 1 0-4 2 5-9 3 10-14 4 15-19 5 20-24 6 25-29 7 30-34 8 35-39 9 40-44 10 45-49 11 50-54 12 55-59 13 60-64 14 65-69 15 70-74 16 75-79 17 80-84 18 85-89 2 5 2 10 24 55 147 423 1. 119 2, 921 5, 780 8, 607 11, 495 12, 987 11, 479 7, 972 4, 241 2, 038 'll': : Ml 'll I 'M !il ' I I :!i !:! li* i i ' :M ;::i I i.' .i VAB.0001023898 APPENDIX B PHARMACOKINETICS-DEVELOPMENT OF EQUATIONS chemical kinetics and presented for the purpose and to demonstrate itc olnn "rrr----- - " tt. cul.llu,1,naUOn 0t tne Ureek word upharmakonn meaning drug and the word kinetics . Thus. it.m---e--a--n-s- iV ' -- 5 biochemical and Rates of Chemical Reactions reaction volume g moles of A disappearing rA (sec)(liter) or the rate of reaction may defined in terms of appearance (B-l) g moles of A appearing rA (.sec){liter) (B-2) define the rate of reaction for reactants earance and products in terms of appearance batch any constant volume, it is readily dCA ta dt terms of disappearance, and (B-3) defined in terms of appearance, then the material balance dCA ta dt (B-4) T Additional references are listed at the end of each appendix. B-l [ Equation (B-7) is an ordinary linear differential equation with constant coefficients which is readily solved by separation of the variables followed by integration to give : CA = CAe-kt (B-8) where C\ is the concentration of A at time t=0. At any time t = tk, Equation (B-8) is a linear function of the initial concentration C^. A plot of CA versus C\ at any time t = t* yields a straight line as shown in Figure B-l. Thus, one could extrapolate from any one point on this line to any other point by linear extrapolation, and obtain the correct answer since Ca is a linear function of C^. This is the basis for the concept of linear extrapolation commonly employed to extrapolate from high initial doses (high values of C\) to low doses (low values of C\) corresponding to human exposures. Obviously, this technique gives the correct result if and only if CA is a linear function of B-l. as in the example shown in Figure Saturable Processes : Development of the Michaelis-Menten Rate Expression Instead of the linear variation of CA with respect to C^, other reactions have mechanisms in which CA is not a linear function of the initial concentration as in the case of saturable processes described by the Michaelis-Menten rate expression. To develop this rate expression consider the case where the product B is formed from A by the reaction mechanism A+S^AS^B + S (B-9) 5 is a compound in the system which is consumed to produce AS, the active intermediate, and produced when B is formed from AS. Compound B is produced at the rate r2 = k2 Cas, and thus, dCs dt = k2 Cas (B-10) In the development which follows, expressions for Cas and Cb in terms of CA are needed. These expressions are obtained by use of the well-known "pseudo steady state assumption" from chemical kinetics. This assumption consists of the supposition that the active intermediate AS reacts to form B at approximately the same rate at which it is formed from A, which may be expressed as FVom the mechanism given by Equation (B-9), it follows that ^ 0 = hCACs - k[CAs - k2CAs (B-ll) r which is readily solved for Cas to give Cas ki CaCs k[ + k2 By material balance where C% denotes the initial concentration of S, and initially CA\ S Elimination of Cs from Equations (B-12) and (B-13) yields (B-12) (B-13) Cas (*!+*=) + Ca (B-14) Substitution of this expression for Cas into Equation (B-10) followed by rearrangement yields dCs hC%cA + fc2 ) + Ca VCA K + Ca (B-15) where V and K are the Michaelis-Menten parameters whose definitions follow immediately from Equation (B-15). Next dCs/dt is related to dCA/dt by first observing that by material balance where it has been assumed that C?AS dCA Cas 0. Explicit differentiation yields dCAS dCs (B-16) (B-17) K Then by use of the pseudo steady state assumption, Equation (B-ll), it follows that dCA dCB (B-18) and thus, the Michaelis-Menten equation is obtained by combining Equations (B-15) and (B-18) to give dCA VC K + Ca (B-19) Consequently, the rate expression for the rate of reaction of A is given by VCA K + Ca where rA is defined in terms of disappearance. (B-20) I ! i i ik :i:!. ! iif| !!:! !!!ill! : 1.:-;: r:ti iJ? m .? i . -a |.k I l =_r i i , 4-. L. L,. b-': fiif r If. |- I 'V I' 4, I) : IJ Characteristics of the Michaelis-Menten Rate Expression Unlike the rate expression given by Equation (B-6), the one given by Equation (B-20) for ta varies in its dependence on the concentration Ca- At small values of Ca < K, Equation (B-20) reduces to ~ V,, Ta = -jcA (B-21) which is seen to be of the same form as Equation (B-6), first order with respect to A. As C*a is increased, the value of Ca increases at any time tk- The rate of reaction at any time tk increases as Ca increases until it approaches its asymptotic maximum value which is shown as follows : VCA K + Ca V lim CA 1 + K C Also of interest is the fact that at Ca -- AT, ra is equal to one-half its maximum value VK _ V rA\cA=K - k + K - 2 (B-23) A graph of ra versus Ca is shown in Figure B-2. Figure B-2. The rate of reaction of A approaches its maximum value asymptotically as Ca is increased indefinitely. B-5 0 to t Thus fc7sr + Jc^Ca~ which is readily rearranged to the exponential form Ce*(c- -CA)e-j?t Of importance is the behavior of the concentration Ca as the initial concentration C\ (or dose) is increased. In this analysis, let the time be fixed at t = tk for all choices of C\. At values of C\ <C K, Equation (B-26) reduces to CA = C\eS'* (B-27) Observe that Ca is always less than CA, and if CA ^ AT, then e-k(CA-CA) g* X A plot of Ca versus CA is shown in Figure B-3. The approximately linear portion of the curve is given by Equation (B-27). As CA is increased, the relationship eic(cA~CA) > ! * always holds for intermediate values of CA because CA is always greater than Ca and thus C\ -- Ca > 0. Consequently, for all choices of finite values (7^, the value of Ca given by Equation (B-26) will always be less than C*A and the resulting curve is of the form shown in Figure B-3. However, in the limit as C\ approaches oo, CA likewise approaches infinity, and CA - Ca is of the indeterminant form oo - oo. However, the variation of Ca versus CA in this region may be found by returning to Equation (B-22). At large values of CA, rA = V. Thus, as CA becomes very large, -dCA/dt - V is readily solved to give CA = C\-Vt ' (B-28) i i i i i i < B-6 t \ I j i i I cc b L e f. f i : ii F i i i b.' I i p; f Thus, at any t -- tk-> the curve of Ca versus C\ becomes linear at exceedingly high values of C% and its slope approaches unity. Also, it can be shown that the second derivative of Ca with respect to C\ is always positive, which does not permit a point of inflection, and thus the curve of Ca versus C\ is of the form shown in Figure B-3. Approximately Linear, Equation (B-28) 4> E C a c A Very Large u< rA= V ------- Slope = 1 cs Approximately Linear, Equation (B-27) eoe C2 >K uo < <K Nonlinear, Equation (B-26) Vtk Slope * 0 0 Initial Concentration, C ? A Figure B-3. At low initial concentration (C K), the concentration Ca given by the Michaelis- Menten expression is approximately a linear function of C? , but becomes nonlinear as the initial concentration C is increased. The parameters K and V of Equation (B-19) may be determined in a number of ways. One could use the relationships displayed in Figure B-2 or one could simply rearrange Equation (B-19) to the linear form : 1 dCA/dt K1 1 (V)CA + V (B-29) The instantaneous rate dCA/dt may be approximated from experimental data by noting that dCA CA(t2) - CAi*i) ACA dt t t At where t2 > t\ and Ca{^2)CA{t\) denote the values of Ca at times 12 and ti. For small values of At, Equation (B-29) may be restated in the approximate form : 1 ACA/At (-)^-- KV}CA(t,,) + 1 V (B-30) where ta v (t2 -}- ti)/2. The straight line has the slope -y and the intercept y, from which K and V may be obtained. Linear Extrapolation Involving the Michaelis-Menten Model Since Ca is approximately a linear function of the initial concentration C\ at small values of Ca and C\ (Pa < CA <C K) at any time tk, it follows that approximately the correct value of Ca may be obtained by linear extrapolation between different initial concentrations CA in this region of concentrations as indicated by Figure B-3. However, as shown in this figure, the concentration Ca is no longer linear with C\ throughout the entire range of higher concentrations. Hence, linear extrapolation would generally fail to give the correct result at the higher concentrations or from higher concentrations to lower concentrations. In fact, the mechanism given by Equation (B-9) which leads to a linear variation of Ca versus C\, at low values of Ca > and nonlinear at relatively high values of CA should not be taken to mean that this is a general result for all mechanisms. When the mechanism is expanded to include several subsequent consecutive, simultaneous, and competing reactions, the nature of the variation of Ca versus CQA can be expected to change and most likely Ca will become nonlinear with CA for both low and high values of C Also, a slightly different mechanism than the one given by Equation (B-9) could lead to a different form of the curve of Ca versus CA. Suppose for example, that the rates given by Equation (B-9) are all second order with respect to Ca instead of first order; that is, mechanism 2A + 25 s* 2AS ^2B + 2S Instead of Equation (B-10), one obtains dCb AS (B-31) (B-101) Thus, and, dCAS dt 0 -- kxC\C% -- kiCAs ~~ ^2C\s Cas CaCs fcj + *2 *1 Since Cs = C% -- Cas> Equation (B-14) becomes (B-12') Cas C%Ca +^2 i /-* kT~ +c* (B-14') B-8 ,i I I I I Ii I I I I I I I I, ) l`l L r; r i \ i` 11 f \ > i I X ); r. li _ r i' i: S' iiiminn Ttfl Pi i and by following the same steps as before, dCA tA dt VCA\ [K + CA]2 (B-20') where V = k2(C"so \)2 k\ d" fc2 K fci Thus, for Ca VCA\ ?A K2 (B-21') and lim rA V (B-22') C Also, rA\ Ca--K VK2 (2K) V 4 (B-23') The integrated forms of Equations (B-21'), (B-20') and (B-22') are, respectively. CA. Ca 1 + ^A~^t (CA < K) (B-27') 1 K2[ C*A 1 --] + 2Kln-gCfAi- + (CA CA) Vt (intermediate values of (B-25') Ca CA-Vt (very large values of Cj^j (B-28') versus values of C\ and linear at large values of C% as shown in Figure B-4. Also, it can be sho iho first derivative of Ca with respect to CA is always positive, approaches unity less than unity for 0 < C\ < oo, and approaches unity infinity. Thus, the curve has a point of inflection, which is confirmed by showing that the second derivative has a zero in the interval 0 < C% < oo. The curves shown in Figu B-3 and B-4 have the shape of a hockey-stick which has been observed experimentally and Menzel B-9 I. ,* I; I . I i; Ii II !i ; !> I i- ! i: li !; I! II !l i !I ; hi l.j > I! l|. ,i I. 'i' Sr I-'- II i| ! I! ! ii: VAB.000 i ; Tl i. iil L iI I. |i I '' ,I i.' h' t. I : I r' I! i: ii l i; iI r; I1 I II ! : I : :i I : 'I :| I. I `I I! I I I. II r, ! ;I i, I- :! ! 11 ;; I ! il n II r i! !: I'.i I-: ! I i: I i' !| i i Mi I .!! Mi i. M.il l.-l! ; M1 l!i !I l! I' SFhoormwnulaintioPn,Vo,,fr0thie rate eExxpurenKsswioirnmsc for th+.e Cancer Mechanism Gehring and librium reactions axe a shorthandfortbe b v TM ' *he stePs ---------- v\| ui chemical is denoted by C and :a~ Michaelis-Menten mechanism The absorbed chemical by CE and its' concentrationby ^ the activated TtL r? ? 2? concentration bv n. th*. Ada,m---a--g--ejd mDNA,/ad, dfu'cts .by C_ AvGTeadndmetabolites by CA and and by CAM and their concentration hv n . * ^AD\ tbe macromoL by C,a?S`S,tS,^'rtZA-. ^ V~CA-D' "> concentration by Cag and kR are the rate constants and and repair step. meanings excretion, activation ) CAM CAG CAG CAD CAD for Lh_e stePs ^ equilibrium mechanism for the reaction of C to CE and to CA is pre^ntS^dy c+s SE + S. C + S. CA + S. ajid Sa denote the respective substrata iwkU,4 , i a manner analogous to that /deWmon.sTMtratedj in tb,, j 1 m relationship given by Equation (B-19), it is readily JSntt? respective reacdtions Similarly, vec vac K* + C + + c The rates VdC K* + C VaC _l q + ^mCa -f IcgCa AG VrCAG Vr + CAg + krCag " *gCa appearance of CE, CAD, CAM, CAD2, and CAG VeC K* + C given by B-ll ,in ;K a If i ii 4 f3|lj-f* m Ei- p W-au, " `'r ,|. .r y.-? I. ! I /Mil H ` - : .+ > . 1 H ' . .V ;l > r ii ' r.1 ` - 'J': if: : 11: :-l : , t + f'S 3 !l ]i I I .4 inr,'fr r* EJ1 l) 3"!iK * il r.i m r-ifliJ k' i sill:I! k'4> >3 ,n: II J. iH'Si.j* J. i ..`r: I Et 'jfr n - i-i 5; r1! -I w;;,-v l' j j; m -I:) ? i\ di?i IjE-;, i t.riHr = ::l! il I 1' AD vdcA Kd + CI- . AM kMCAI . ;il jl vrci; AD AG 11 Kr + CAG AG IcrCag an `he chemical C and II parameters as well as the rate constants 1 tu u * set / values for all of the V and If may be solved simultaneously as a function of SZTHLrdinary differential equation similar to those shown in Figure 17 maybe pre^d^" rCSUlts 80 obtained> graphs' additional references Menzcl n B pT 7' gleWd CIiffs- New Jersey (1989). engineering, 2nd ' ' ' 1'i'sloloK1ca! Pharmacokinetic Modeling," Environ Sri T A ,, g, environ. Sex. TechnoL, SI, (i0) (944),1987 I B-12 "Ht:-i ; ! EM J :! r r-5 ! ilfM nr ft n = h: m : I si: !: fen .s-iiU M I I! !i i! il !I ill! j!!j Ml Mi' !;l; ii'il !i:i; I !i IM i; i! i !:li . f* UMiwHmuww APPENDIX C THE BIOCHEMICAL BASIS FOR CELL i h I REPLICATION J k r i L i I This appendix consists of an abbreviated summary of some of the fundamentals and developments of biochemistry which form the basis of the present theory of cell replication within the human body. Excellent treatments of the concepts summarized in this appendix I I sire given by Ham72, Bailey and Ollis73, and Aiba et al.74 P L ' According to Ham72, a cell may be defined as the smallest unit of living material which is capable of existing independently in a non-living environment by synthesizing substances which it needs from nutrients absorbed from its environment. Most cells also have the capacity to reproduce themselves. The condition of a non-living environment rules out viruses because they can exist only in a living environment. I L t Cells have also been defined in terms of their structure; namely, as a minute body of protoplasm surrounded by a limiting membrane and containing a nucleus. Protoplasm p 1 i. r ii was defined by Huxley as the physical basis of life. It is now generally accepted that the manifestations of life are dependent upon the continuance of a vast number of chemical i reactions which occur in and also with the protoplasm. Since protoplasm is consumed by chemical reaction it must be produced by other chemical reactions from the surrounding nutrients. The sum total of all chemical reactions occurring in a cell and conferring on it the properties of life is called its metabolism. Most of the chemical reactions which occur within a cell are catalyzed by enzymes which consist of proteins that are synthesized from amino acids. Proteins also serve a number of other purposes in cells, such as membranes. There are three fundamental classes of cells; namely, (1) those which never reproduce i i fI-: themselves such as nerve cells, (2)those which constantly reproduce themselves (called i 1. stem cells) to replace those that are lost, and (3) those which do not ordinarily reproduce themselves but have the capacity to do so, such as liver cells. ii y i ? Structures of DNA and RNA A benchmark in the understanding of cell behavior was provided by the structural concept of the DNA (deoxyribonucleic acid) proposed in 1953 by Watson and Crick.75 The biopolymer DNA contains all of the cell's hereditary information. The DNA nucleotide is i composed of three components : (1) phosphoric acid, (2) deoxyribose sugar, and (3) the nitrogen bases, thymine (T), cytosine (C), adenine (A) , and guanine (G). The biopolymer RNA has a structure similar to DNA, and it assists in the replication of DNA. Instead of the deoxyribose sugar and thymine, RNA contains d-ribose sugar and the nitrogen base > i uracil. i i' i i i ' * Ti i i i i I i I i' i- -! i i i i ii i I I I ! i I: ; II l: - I :i i>i ;l '! li :|Mi ;iii:i[ i i:- r 11 i i- ill! Ml : !! : 11 li' ; | i i ! 'L :l ill: -I 'i "li. '!! =1 r i i i i i i i r; I *1 I I I I I. I I' I. i |Si !i:i Ijl i|!. ill' !| :|| ij:: ! i bMi: .i: ' I!! ..in : i 11 .li! ii! i|M 'll:! nil ': 11 1 il : VAB.000102391 ! ! mi; ij Ml! i! i I. I I. r i i; c. K t I- A k t t N 1 ir iI r : k L i. h r k r r y V p' l y i i i. i. i' I '? i' I' I I i I J i 1 i i mmmmmmmrmmmfrnmm >Wwrmtl|iLHHHwJIN(HWIIIIIIIiPPIIIPIHIIIIIIIIIMHHIIWWWWIPWIfWfWril Sugar Strands Nitrogenous Bases Strand 1 sugar sugar suaar suear - sugar - sugar - DNA Double-helical sugar - = phosphatediester bonds = two hydrogen bonds connecting A and T = three hydrogen bonds connecting G and C = adenine, T * thymine, G = guanine, C = cytosine T - sugar G - sugar G - sugar SrsaS 3TM * ----wassaaaa - diagram of deoxyribose and d-ribose which make C-2 1 ' ir /' : ii illi f [ ^ 5-f VH I r? - Si. tl * r.!' '."I !=]? ft 'r-N: K I' *5 srfi > U, it i|S tfliJ != ihi:Blsi I1 . / ! pru; &l!?.|I I M! !'? Wl1 id h: r w-, ! E i. rg !d' |i?l 11 "iii- i-'-S l.> F* I1 I1 i : i . ;--i K ' :'M!!.lIW F"? S|t ' !!i l -* I.: :l- l iI, .lafc! *; : :::a7. A ?: Hr"- :| si'F;r^ a i >I . I* d! r r,-5 h s i fiigtafc!|- 1 [: K.-tSsJ!. 5 a I "l.i| jf' j' ;f fl- l.r ii -i:l: i .! I- I - * u 1 I'i : l-jj ]i| : = &r*\: i: Li.;| lx! - - ;.-|p] j Sir ^ !. Esn K i 1 ;l .1 I i. I: I; fhH -:ilm\j 11: \i $ 1? -j'-jr K- : : i! . i r- tI Iu pj : ifiii.i iB.TI f IjK j`f If I i^ I%m.-hT l-v Hi ;i-` IWIMI:iii i = *V l i 1 l I, I, ,r : ! .i l* ! r. I I of the DNA and the d-ribose of the RNA axe usually derived from either purine or pyrimidine. Purine Pyrimidine The nitrogenous bases shown in Figure C-3 are attached to each other in the crosslinks of the DNA by hydrogen bonds. Adenine and thymine are connected by two hydrogen bonds, while guanine and cytosine are thought to be connected by three hydrogen bonds as shown by Spencer.76 The adenine-thymine hydrogen bonding is shown in Figure C-4. Also as indicated in Figure C-l, thymine is always paired with adenine, and cytosine is always paired with guanine. These strands may be as long as 40 million molecules, and the molecular weights of some DNA molecules range up to 2.8 billion.73 H- N "H H H Guanine (in both DNA and RNA) H Adenine (in both DNA and RNA) H -N H I \C H H- C N H N" H H Thymine (in DNA only) N I H Cytosine (in both DNA and RNA) H CO l H Uracil (in RNA only) Figure C-3. The nitrogen bases in DNA and RNA. C-4 1 Adenine Thymine Figure C-4. Hydrogen bonding of the Adenine-Thymine in the DNA crosslinks Duplication of DNA Molecules by the breaking of the weak hydrogen bonds connecting the nitrogenous Figure C-5. After the two strands have been separated, a new strand is i each of the original strands, and the two new molecules of DNA formed of the original DNA molecule as shown in Figure C-5. strands Biological Implication of the DNA Duplication Process The duplication process illustrated in Figure C-5 corresponds to cell division which in turn corresponds to the division of the nucleus of the cell. Prior to cell division, the nucleus appears as a well defined mass in the cell. During the division process, known as mitosis, the nucleus membrane dissolves and the chromosomes of the nucleus become rodlike in form. The chromosomes consist of DNA molecules and proteins, which had been identified uscope long before the structure of DNA was proposed by Watson and Crick75 in 1953. The chromosomes carry all the hereditary information in the form of genes. Although much effort had gone into the visual identification of the genes prior to the proposed structure of DNA, it met with no success because it has now been established that genes are not physical entities but consist merely of the ordering of the nitrogenous strands This sequencing of the bases controls the synthesis of proteins. In particular, the genes consist of the sequences of "three letter C-5 I f!a :1p ;*fcv-: ; J. M ii- / / - >." i j "i '.i Iii i'!= :'i. j;- iri ui !-l ! L' L1 !; n '!-] e:'fM V 'il i- .-I- i: j- -y mi i ! , :!( : !! tfiir..: if;,!;!.; i.\.' i Hi-;; 'I i 1! mINIII r S [;-.[ l . : I-. V*> i -j mI- i li' `L !- : 4: i: 3 .i}!'.] '.t . 3 J; ::: r. i . \MI- J' ;i!jMi.-i.L . !: i P !hr- -I ,-i: i' ii!:- - i-l :;! E ; M i:; b\ ; v: ii-ivir I ' iiirl ; hi: ; !' - Ul-: i o i : ^^rij? ! . r . ij. !: 31- : V r ; : #[: -:| S :-i !*. .jf : 11 f^ ^ -it- i i *: t i: = :r,-^ = !^ J ; [' :'b :! fJI- ; . ii I: 1 L:i-. r| l-.f | m : :7 U ==| J 0.- ^ . f-tv- (si a -p ; li/ -i-j .[! r :L ::-.#kl:::1I 1 pl.,-'.tj ^ r. ia ! i 'i'lj !:] i. i. = j:rjP s. i-i 'll 1 i! T 'i'' h-w t; j i ;i ' ' -i -l - ' '' iffi \i.i. 'i t !:! ! i'i .- r i - | i 1 I -J :l !. I ]L 't I Ii r: ii i:1 H 11:1 j- i!;3 : !;iJ ! l.il \: !ji Jli i= il Is. : ! I; M:i i !, ! ! =1^1 ; ii!i rI i -li!' : \m n 'I i: : !: :ili''!il i iii !'H . ;:ij! l:- il I. i;.. VAB.00010239 I TABLE C-l. THE AMINO ACIDS INVOLVED IN THE SYNTHESIS OF PROTEIN ENZYMES. Name Abbreviation Name Abbreviation Alanine Arginine Asparagine Aspartic Acid Cysteine Glutamic acid Glutamine Glycine Histidine Isoleucine Ala Arg Asn Asp Cys Glu Gin Gly His lie Leucine Lysine Methionine Phenylalanine Proline Serine Threonine Tryptophan Tyrosine Valine Leu Lys Met Phe Pro Ser Thr Trp Tyr Val C-l are those which are involved in the formation of protein enzymes by condensation. As an example, consider the formation of a simple protein polymer by condensation of two amino acids (containing the R\ and R2) as follows : I I > I I I I J I JII : !J 1111 j 11 j i 1 J ? ;i i i 1 j i i 1 \ 1 i j i i j * y 1 1 1 1 1 1 1 1 1 1 1 1 1 1 \ 1 1 1 VAB.0001023916 j a peptide bond. Li Roles of RNA least three types of RNA and all three whereby information stored iI transfer RNA, which are denoted by mRNA, rRNA, anRdNtAR,N(A2)ribosomal RNA, and s same r! ------ --, jr, lRUNlrAt has the base uracil instead of thymine and the ribose, instead of deoxyribose. may be double-stranded single- stranded strands of DNA begin to separate, the first step "dS "iaWby the synthesis of messenger RNA (mRNA) from below. an order specified by the template (the 3' to 5' strand of DNA) DNA TT Each three letter word is an anticodon TA Transcription (RNA polymerase) mRNA 5* Moves toward ribosome RNA ACG Each three letter word is a codon A,,iS Ci4le,d ^ription because the mRNA carries inscription of the 3 letter words formed from A, C <3 and U ranges from 25,000 to 1,000,000 according to Bailey and Ollis amazing aspect of the protein production (codons) has Bailey and Ollis ammo taken from specify thatthefiT ^ T* * a^no Jds^S se^d to GAA specifies that the second aammminoo aacciidd iiss ttoo bbee gdlnuttaamm.iVc a^cid A(G,1..i A ?, 00(1011 C-8 lllbi H -p. 'Si!:-! i}i^!ji&i: *ffv' i}!:j a' i .i..i ? Sifbsl Mm*i gisia i 11 4J i $ft I I : ;l IK-:!? If?1 ti r>.^.|.-i if!| -i': II Ij I i1-1:1:!!I !. :li ..ii ' : I' I i ! !:l; i :i i` I :l:i ;;i:: |. I |;j; jj ;ii= ii ! I !! I 11* ii !' ":':f I: 'hi! i! '!: Ii il I! M.il!! i: i j !; II ;j :i i;i: ........... I! I i:;- :i ! Ii I i! III'! !I ii i .i !l; Ii' i ' !ii i'i! :ii Ml I::!!:! i - i' i ii! ii i;!i I i i ihi :i :i . ;m Mil! . i ;'l .! i, i: i i ! :l: l: :;i i i'i: ::|!i !:i! i: I:!' 11 i i :i= I i i*!ii ji;j ! i. i: i. ;!! i!j! !! i. :ili- :i! i i ri i ii'i- hill lA : 11!;; li ;|;i! Mi :|i. !I I; i'! III lil I'' III i, illii i I' i:ij !i ! il .Mil i;! I il !>! i! :i! 'll I!:!;iil !;!!; ii:! il illi; :1j-:|: I ;!! I II : i, * i I V. K V1 K: it-' k-r i` * TABLE C-2. CODE OF THE CODONS OF mRNA. [Taken from Biochemical Fundamentals, 2nd Ed. by Bailey, J.E., and D.F.Ollit, McGraw-Hill Book Company (1986).} second first u Phe Phe Leu Leu Leu Leu Leu Leu He lie lie Met Val Val Val Val C T Ser Ser Ser Ser Pro Pro Pro Pro Thr Thr Thr Thr Ala Ala Ala Ala A Tyr Tyr Stop Stop Hit Hit Gin Gin Atn Atn Lyt Lyt Atp Atp Glu Glu G Cyt Cyt Stop Trp Arg Arg Arg Arg Ser Ser Arg Arg Gly Gly Gly Gly third U C A G U C A G U C A G U c A G codon UAA has the single function of stopping the process. As the mRNA is formed it begins to move away from the DNA strand in the direction of the ribosome RNA (rRNA). The ribosome RNA and transfer RNA are synthesized in a manner similar to that shown for mRNA, by using a portion of a DNA strand as a template. Bailey and Ollis73 state that the molecular weights of rRNA and tRNA range from 35,000 to 1,000,000 and 23,000 to 30,000, respectively. The sequencing of the bases attached to tRNA is the same as that of the bases attached to the 3' to 5' DNA strand where, of course, uracil replaces thymine. Each 3 letter word of tRNA attaches itself to one specific amino acid from among the 20 different types of amino acids in the neighborhood of the messenger mRNA and rRNA. The rRNA acts as a site for the mRNA as it participates in the formation of the protein enzymes. This process may be visualized as shown in the following diagram. * C-9 I. Ti i ii 'I * ' :i !I 1i I I: i ;l , 'I Met Glu T A A TAT uu Start GA Ul /AU A 0 ribosome RNA Stop 3' Messenger DNA Some Mechanisms of DNA Damage and Repair From the foregoing discussion of the roles of DNA and RNA in cell replication, it is eviden that the most critical step in the utilization of the information carried by the DNA (th chromosomes and the associated genes) is the formation of protein enzymes from th amino acids. Since these enzymes catalyze the chemical reactions required to produce th the importance of producing the of primary importance In view of the complexity of this process, spontaneous errors m the replication of DNA, called mutations, do occur. The \* rate is relatively low, however, of the order of 1 error for every 106 gene duplications. As an example, the alteration of a codon for one amino acid can lead to the substitution of a different amino acid in the protein chain, thereby forming an abnormal protein. Sickle-cell anemia in humans is caused by an abnormal protein which contains valine (Val) instead of glutamic acid (Glu). This substitution is caused by replacing the codon GAA or GAG for Glu by the codon GUA or GUG for Val. t Another postulated mechanism for spontaneous mutation is based on the fact that the nucleotide bases of DNA have several structural forms known as tautomers. Although the equilibrium is believed to favor the forms shown in Figure C-3, shifts to other tautomeric forms could cause errors in the base pairings. Errors in transcription can also result from the incorporation of analogs of the correct bases in the DNA crosslinks. Damage to the DNA bases can be induced by a host of classical reactions such as alkylation. These mechanisms can lead to a number of different. C-10 i: i 11 i : il Il !I Il ii I: ! I ! :l I :I II i' !I Ii I :! i i !i I| i! I! Ill !: i '.'i I / / MI'I r. wf-pl-it J-1 LI t-. ii'i mi,1 i r 15 :-fr' r ?: -i- ft II* . I t L.ii .1 11' t:li i i fiLE-iMi -4.J i ar:*:\\ At. ;.-r J. .F'l ; j'L i -i:F t tL'.c Sfl -j. -V tb w?n * = -'Vh ili?r I*. J 11 ; -j. . j i G-i- i: i * i i* i * "H-: i\ ii 4 -i. Lijc j 1 Li - ir sc::-j: j- m 4!n 5 "*SlL| P? tiiTM' rr: ^i:: t hi rv.w u ' TT'-Ma ^It! - ri. :,l;f 1 VJ4 b 1 ! I. M' :^i ii mrS . $*K[|: Kt M J. J v: I'qJ is] fcif i; t: * k-U Fii' JI 1 ,'l\< Jri! a1 * S??3h=Ill FL.i:i -| !*|j i-- h i lit ii-! i I r 'iEj -j:] Hi *.te ii ll; I L- : 'f -H-ll m :jij -!i: iHl I:r\i ;|il: i:. V- ij ri-i.li! ti' 4l- L l M 5)'! M iM ro Nt. r.A- Ih ! I: ;! i: ! '! !l : i 'I I. m :i ! !l il I: i i : i M I'l i ! i: ! !!.' ;:!m>| i .' i! I: ;i !i :i :i '.i- il > !! I'll! I ! I in II I!l'I H ii- . ,1 Ii! I !| ! il ..i; il ! ;! ii i I !! i; I j ; I I ! Il :.:'r ' il '! : ii .; i ii 1 i; .1 I1 i i: ' iil: iI ii! .Si I I : M ! i' i ; i; Ii i' I IS! i: i |l . :i. i i i ! '. i :! !i hi '! i:i I -I in i !i ;li i! ! I ul :I ii ! 1 !' .Ii ,i i! :| ! i :!;! r- il' Ii ! ; l I 'i.1. :| !i . .I : -I n|i II :I i i 'I III Hi .i .:i '.Ii I! II! I. ! II is. i i! ::l ! .1': i l! i il I'l'l i . i I :|i; 'i i i i !! 11: Ml . i. .; -1 i: !i ! i!!; 1 i: l! ii!; i ;H *i ** !I l; ! :: i! iI ! Ml: I:! II : i':!i i i :.i ! ! 1:1 Ill ii| | : :.,l. Ml; i i. i ;i l ii T: Ii '! 'I '! iMi! Nil .i -.i Mii! ill .I il- jl * ; | . II- :l>: i:i . i i Min i i: .i ii Ini ii-. :> ! 11 'Il :;ii I i MiMjii 1 I : I s' | ;i --'i i M ; 'i!l liij i:i! 1i1l1l11!1: I' :! iiiM: ill I I 1 : ! .1 Mill !:! : i; Im; ||!! : ! 1! :! l-::i! i!J!n:i : :!l:'=! sii:r i:S||:i :!;i:.i-i;ii|- ,i ii! i !M=!!iij=: iMi: >!l' .i III : i :i . ji- i:::I.i iiii-hii ! in i Ii- types of damage to the DNA such as : (1) single and double breaks of the DNA strands, (2) base alterations and strand alterations by chemical reactions, (3) intra-strand crosslinks of DNA, (4) crosslinks of the proteins, (5) crosslinks between proteins and a DNA strand, and (6) base substitution by analogs. A tremendous research effort has been made in the identification of these mechanisms of damage, and the literature is voluminous. The major references used in the preparation of this report are listed in the books given by references 77 through 80. Although these books constitute a small percentage of the total publications in this area, each of them contains hundreds of references. Of all the possible mechanisms for DNA damage, the free radical mechanism is generally conceded as contributing the greatest variety of DNA damage. Many biological reactions occur by the free radical mechanism in a manner analogous to that seen in petrochemical polymerization reactions. Free radicals may be formed in a number of ways. Ionizing radiations such as x-rays and 7-rays , generate ions which generally lead to free radical for mation. Also, many compounds including some beneficial drugs are capable of generating free radicals. In view of all the possible mechanisms for damaging the DNA, the situation might appear hopeless, but that the bio-systems have a remarkable capacity for the repair of damage. Wilson (see pg. 1, Ref. 78) attributes the survival of the species to the inhibitory, scavenging and biochemical repair systems. Free radical formation from sources other than radiation are prevented by the cell compartmentalized structure, the presence of catalase and glutathione peroxidase which Eire able to decompose hydrogen peroxide, and to the presence of the macromolecules transferrin and ferritin which are able to bind iron. In the event that free radicals are formed, they are generally scavenged immediately by nearby organic material. If however, some do reach vital molecules and oxidize them, there is still the opportunity for free radical repair. The concept of free radical repair by reduction or hydrogen transfer arose in the early 1950's in an attempt to partly explain the protective actions of diphenyl picryl hydrazl and octyl mercaptan on radiation-induced decomposition of some polystyrene polymers. Free Radicals Produced from Chemical Carcinogens and Their Significance in Carcinogenesis Almost all classes of chemical carcinogens are able to generate free radicals by enzymatic reactions. On the other hand, noncarcinogenic compounds are relatively stable and difficult to convert to free radicsils under the same conditions. As pointed out by Nagata (see pg. 58, Ref. 80), these results suggest a role of free radicals in chemical carcinogenesis. In fact, one of the general theories of cancer asserts that it is caused by uncontrolled free radical reactions. An extension of this theory is that the active forms of most chemical carcinogens are free radicals. Most of the studies support these concepts but do not constitute a proof that free radicals initiate the reactions which causes malignant transformation.80 Also, the experimental evidence points to a role of free radicals in the rate of cell division. Although the story of cancer formation and growth is not complete and direct proofs r C-ll *