Document n9zv14Q68knQyvM4jRxJ1Yb6X

.. '.vi. 1:2 \ Ci.;-,-ifl* iy ' .`JJ-I A_ --.i.'-.ia J Asbestos Exposure, . Smoking, and Neoplasia Irving j. SciikofJ, MD:.E. Cuyler Hammond, ScD; and Jacob Churg, MD Asbestos insulation workers, as a group, have a high risk of dying of bronchogenic carcinoma (about Sevan or eight times expected). We have observed 370 such work men from Jen 1, 1963 to April 30, 15S7. Our findings indicate that asbestos exposure aione is not the entire explanation. Of S7 aor.cigarette smokers, none died of bronchogenic carcinoma. Of 233 workmen with a history of regular cigarette smoking, 24 died of bronchogenic carcinoma, although only three were expected to die of this disease. Calculations suggest that asbestos workers ' who smoke have about 92 times the risk of dying of bronchogenic carcinoma as men who neither work with asbestos nor smoke cigarettes. We conclude that asbestos xposure should be minimized, that asbestos workers who uo not smoke should never start, and that those now smoking should stop immediately. Tn 1954, we reported on deaths occurring between j_ Jan 1, 1943, and Dec 31, 1952, among 632 members of the International Association of Heat and frost Insulators and Asbestos Worses.' All of these men had been occupationally exposed to asbestos dust for many years. Their death rate from lung cancer was found to be 6.S times as high as that reported for the general white male popu lation of the United States during the same years, with'age taken into consideration. Three of the men died of diffuse pleural mesothelioma and one died of a neoplasm histologically suggestive of peri toneal mesothelioma. This was of interest since mesothelioma is a very' rare disease in the general population but is reported to be associated with exposure to asbestos dust.' In addition, their death rate from cancer of the stomach, colon, and rectum \yns higher than expected; but this may have been Frorr. Ihe J>*p3rtm*nt of Cnmm'iuiiy Medicine, Mount Sinai School o* Medicine (Drs. S^Ukol: ?.nd Churij), and the D-'prfrtrr*nl of F.p.cL:rjoV*Ky and Statistics, American Cancer Society <Dr WHniC'.vnd), NV* York. Read before u joint meeting of the Section on Disftisrs of the Chest with th? Section on Preventive Medicine and the American College cf Ch?st Phy^.ciorts at the llf?h annual conveniii,.) of the Vincric-an Medical A:^*oc:vdifri, Atlantic City, NJ, June it), 1967. Reprint requests* to Mount Sinai School of Medicine, 100th Street and Fifth Avenue, New York 1CX/29 (Dr. SelikoST). due to chance, the number of such deaths, being small. During the latter part of the study, we ob tained information on the smoking habits of most of the survivors, but we could not obtain reliable information on the smoking habits of those who b id died at an earlier date. Therefore, we could ot at that time investigate death rates in rela tion to smoking habits and exposure to asbestos dust which were considered both separately and jointly. There is abundant evidence that cigarette smok ing leads to a high rate of death from lung cancer in the absence of occupational exposure to asbestos dust.'4 Our findings outlined above suggested (but did not prove) that exposure to asbestos dust may lead to a high rate of death from lung cancer in the absence of cigarette smoking. If the latter be so, then the combined effect of both types of ex posure might or might not be equal to or greater than the sum of the two effects. On the other hand, it w5 possible that exposure to asbestos du* in creases the risk of lung cancer among cigarette smokers but does not lead to lung cancer among nonsmokers. The present study was undertaken primarily to investigate these possibilities. In addition, we wished to obtain more information on the occur rence of mesothelioma and gastrointestinal cancer among asbestos workers. Material From records of New York Local 12 and Newark, NJ, Local 32 of the International Association of Heat and Frost Insulators and Asbestos Workers, a list was made of every man who was a member of either one of these locals on Dec 31, 1942, or who joined between that date and Dec 31, 1962. No one was omitted regardless of his subsequent work history. Personnel data from union records indicated that or the 632 on the union rolls on Jan 1, 1943, 339 of the men had first been occupationally exposed to asbestos dust prior to 1922, and an additional t \ JAMA. April 3. 1953 Vol 204. No 2 HER 0000727 /.ruEc ?',,s ;SU-:-SLI OFF ET AL 107 293 men had first been ex* Table 1. --Subjects Clastifieb by Are cs of jjn 1. 1S63. and by Ysars From First Occupational posed- between the be- Exposure to Asb-stcs Dust up to Jan 1. 1963 finping of "i S23 and the of 19V2. All of these men.-vere successfully traced through Dec 31, 1352, and 262 of them were found to have died up to that time. Of the 262 deaths, seven oc 35-39 40-44 45-49 50-54 55*59 60-64 65 69 70-7* ToUl No. of Subjects z 13 32 1C9 60 42 49 33 20-24 2 12 17 .. ... . No. of Years Slr*c First Eapoaur# to Asbestos 25-29 1 2 1 1 1 ... ... 30-34 .. .. . 13 80 1*5 3 1 ... * 35-39 ... ... .., 28 34 li 10 3 40-44 .. . . .. . - ... 8 19 18 12 4S-49 ... .. ... ... 1 8 18 6 50+ ... ... ... 2 17 No. of ' 52 Us' ... 1 2 18 11 IS 17 18 curred prior to the 20th 75-79 Zl ,. # . ... 1 s IS 8 anniversary- of the man's 80-84 4_ 1 1 23 first exposure to asbestos sTotal 370 31 113 86 59 39 36 94 dust and 255 occurred after the 20th anniver Table 2.--Subjects Classified by Aj-e and by Smoking Habits on o- about Jan 1, 1963 sary. Thus, of the 632 men, 370 were still living on Jan 1, 1963. These 370 men were the subjects of the pres ent investigation. Table 1 shows their age distribu tion as of Jan 1, 1963, and the lapsed time from first exposure up to that date. Ail of them have been traced, and' 94 of A9. Yr 35 39 40 44 4549 50-54 55-59 6064 6S-69 70-74 75 79 80-84 Total Total No. 2 13 32 109 60 42 49 38 21 ' .4 ` 370 Never Smoked Regularly 1 2 2 12 6 7 6 7 3 2 48 Pipe, Cigar Only . *. 1 6 5 4 8 7 7 --i-- 39 Excigarette Smokers* i 2 s 26 IS 15 17 12 6 1 101 Current Ci*reCta Smoker*- 1-9 Day ... ... 3 . 1 ... 1 ... .--. 5 10-19 . Day . .. ... ..." 5 3 ... 4 4 i .--.--. 17 20-39 a Day ... 5 12 33 20 ii 9 4 3 -- 97 40 + . O.y ..... 4 12 24 10 4 5 3 1 .--.. 63 them were found to have InciuO.s cigarette smokers who also smoked pi>es or cigars. died during the four-year and four-month interval from Jan 1, 1963, to April 101 were excigarette smokers, five currently smoked '). 1967. one to nine cigarettes a day, 17 smoked 10 to 19 leginning in October 1962, we made arrange-- cigarettes a day, 97 smoked 20 to 39 cigarettes a ,.,-nts to examine these men periodically, once day, and 63 smoked 40 or more cigarettes a day. everv six to twelve months; the interval depended The smoking habits of the 370 subjects were uuon age- and physical condition. The examinations compared with the smoking habits of a large num include chest x-ray films as well as physical ex ber of men selected from the general population.5 amination and cover past and present smoking There were proportionally more cigarette smokers habits, occupational history, medical history, and among the 370 subjects than were found in the current, physical compla,,,wS. Altogether, w. nave' genercl population sample; age was taken i:\tu examined 338 t91.4) of the men at least once consideration. and have repeatedly examined most of those who Causes of Death.--A copy of the death certificate are still living. was obtained for each of the 94 deaths. In addi Information ori smoking habits was obtained by tion, we examined hospital records, postmortem persona! interview- with the 33S men who were ex findings (41 cases), as well as the surgical and amined. Of the 32 men who were not examined, pathologic reports when surgery was performed (39 six told us their smoking habits by telephone and cases). We also reexamined histologic specimens. five gave us the information by mail. The local It was found that the death certificate was inac union secretaries (who personally knew these men curate in 14 instances. However, this did not alter welll ascertained the smoking habits of 18 men, tha picture as much as might have been expected and family members supplied the information on since there were several compensating errors. For the remaining three men. This accounts for all of example, in one instance the death certificate in the 370 men. Table 2 shows their smoking habits dicated bronchogenic carcinoma as the cause of on or about Jan 1, 1963, the men being classified death while a review of the histologic specimen by their ages on that date, even though some showed that death was due to pleural mesothe changed their smoking habits between 1963 and lioma; but in another instance exactly the reverse 1967. was found. Likewise, review in one instance re Of the 370 men, 48 never smoked regularly, 39 sulted in changing the reported cause of death smoked or had smoked pipes or cigars but never from bronchogenic carcinoma to cancer of the smoked cigarettes regularly, and 283 had smoked stomach with metastasis, to the lungs while review arc-rtes regularly. Some of those with history of in another instance resulted in exactly the oposite .. ^.arette smoking also smoked pipes or cigars. Of change. The 94 deaths were ascribed to the follow the 2S3 with a history of regular cigarette smoking, JAVA. Aanl 3. 1353 Vol 204, No 2 ing causes;^ bronchogenic carcinoma, 24; pleural \ HER 0000728 1C3 ASBESTOS EXPOSURE >ELtKOFr ET AL Taijle 3.--Observe snd Exp?-ctecJ Numb" r of Ce aths Among 370 Astssfes WorXe.-s During tbe 52- f.forsth Period C of Otath JTs-fal. c.*ncer (all sites) Cancer of lung. jleura. bronchus, and trachea Sronchcgcnic carcinoma Pieurjl mesothelioma fan'ocejl me.cthel.oma Ccnihf Of SJO.TACh Cancer of coion and r actum Career of Of! Other sitas combined Asbestosis Heart and circulatory distase including strek* All other causes of death Observed Deaths 49 27 24 3 7 3 S 7 IS 22 a C ted D-*tt* a6 23 t t t 06 12 4S . .. 23.5 10.4 Total, all causes 94 47.5 *Oa&d oDcn US rrortal-ty doia divesi'ding smoking habits. fUn^ed States Ctj not ava.lobl*. but figure should be only sightly in general population. mesothelioma, three; peritoneal mesothelioma, sev en; cancer of the colon, four; cancer of the rectum, one; cancer of the stomach, three; cancer of the pancreas, two; cancer of bucca! cavity and pharynx, two; cancer of bladder, one; cancer of undeter mined primary site, two; asbestosis, 15; cor pul monale, one; cornary heart disease, 17; congestive heart failure, one; cerebral vascular lesion, two; aortic aneurysm, one; cirrhosis of the liver, three; bronchopneumonia, one; encephalopathy, one; acute pancreatitis, one; Wegener's granulomatosis, one; and accidental fall, one. Expected Deaths.--For purposes of comparison, we wished to ascertain how many of the 370 sub jects would have died during the 52-month period (Jan 1, 1963, to April 30, 1967) if their age-specific death rates had been exactly the same as for the general white male population of the United States. For this purpose, we made use of the United States \96-i life table for wh:f-' males; this prodded the most stable basis for comparison. It should be noted that for white males total death rates and death rates from respiratory cancer were slightly higher in the industrial states of New York and New Jersey than in.the United States as a whole.*'7 On the other hand, respiratory cancer death rates in white men aged 20 to 64 are reported to be a trifle lower than average among laborers, not elsewhere classified employed in construction work.* From the life table we determined for each of the 370 men the probability of his dying within a pe riod of 52 months, considering his age on Jan 1, 1963, and assuming that the life table probability applied to him. Summing these probabilities for the 370 men yielded an estimate of the "expected" number of deaths under the null hypothesis that the age-specific death rates of these asbestos work ers are the same as for United States white males in general. The computation indicated that 47.5 deaths would have been expected. Nc.:t, we wished to estimate the expected num ber o; deaths from each of several causes. For this, we made use of the percentage distribution of deaths by cause of death among United States white males of various ages during the year 1954 as reported by the National Center for Health Sta tistics. These percentages were then standardized for age according to the age distribution at time of the 47.5 expected deaths. The results are shown in Table 3. Expected us Observed Deaths.--As shown in Table 3, there were 94 observed deaths (ie, 94 of the 370 asbestos workers died) as compared with 47.5 deaths expected on the basis of the age-specific death rates of all white males in the United States in 1964. Thus, there were 94 minus 47.5 = 46.5 excess deaths. The excess deaths were due to bron chogenic carcinoma, mesothelioma of the pleura and peritoneum, asbestosis, and cancer of the stomach, colon, and rectum. Cancer of Lung, Pleura, and Trachea.--In pub lished mortality data for the United States show ing deaths each year from various causes by age, sax, and race, the following diseases are combined: cancer of the lung (including sarcoma of the lung), cancer of the bronchus, cancer of the pleura, and cancer of the trachea. For this group of diseases, there were 27 observed deaths and only 213 ex pected deaths, a ratio of nearly 12 to 1. It is well known that, for the United States as a whole, all except a very few of the deaths re ported in the combined category are due to bron chogenic carcinoma. Thus, it may be assumed that there were close to 2.3 expected deaths from this causa as compared with 24 observed deaths, a ratio of over 10 to 1. Mesothelioma.--'Ten of the 94 observed deaths were due to mesothelioma, three were due to pleural mesothelioma, and seven were due to peri toneal mesotheliomas. This is such a rare disease that if the 370 subjects had been selected as a rar<Vm sample from the general population, one would not have expected any of them to die of mesothelioma within a period of 52 months. All three of the men who died of pleural meso thelioma had a history of regular cigarette smoking. Of the seven who died of peritoneal mesothelioma, one never smoked regularly, one smoked only pipes and cigars, and five had a history of regular .ciga rette smoking. Cancer of Stomach, Coton, and Rectum.--In our earlier study of asbestos workers,' there were more < deaths than expected from cancer of the stomach, ( colon, and rectum (9.4 expected, 29 observed). As compared with a total of 1.8 expected deaths from these causes, there were eight observed deaths in this study, due to cancer of the following sites: stomach, three; colon, four; and rectum, one. Al though this bears out our earlier findings, the num ber of deaths from these causes was so small that we still refrain from drawing any conclusion at this time. Asbestosis.--Asbestosis accounted for 15 of the ... 94 deaths. While it is not surprising that deaths from this disease occur among men exposed to 3sbestos\du3t, attention must be called to the fact HER 0000729 JAMA, April 8. 19S3 Vol 204. No 2 iTCS EXPCyj.'E - Sip.!-'.OFF ST AL ' GO that th::-= subjects w-s:a primarily insulation work T*--- 4.-estimated Number Lung Cancar Deaths EJjpectod to Occur During a Psriod of 52 Months per 10,000 Men Living at the Start of Period; by Age and by SmoXing Habits* ers. While ell of them were occupationally ex posed to asbestos dust, "tfieir decree of exposure was light as compared with the degree of ex posure of asbestos miners, processors, and weavers in earlier times. 3ror.choger.ic Carci noma.--Bronchogenic car cinoma accounted for 24 deaths while only about 2.3 were expected on the Afe, Yr (Jan 1. 2953) 35-39 ts-t* 45-49 50-5* 55*59 60-5* 65-69 70*74 75-79 60-94 Neer Snr.cked P.e'uUrfy 0 2 2 7 6 16 14 12 . 28 25 Pi?e. Cigar Only ......t 2 12 25 31 32 52 53 32 riclftxrett* Smokers^ 5. 75 10 22 53 71 97 100 ICO US 1*9 t Day ... ... 23 ... 80 103 ... ... Current Cigarette Smskersf 10-19 a Day 20-39 a Day ... . IS 39 44 69 91 ... 117 190 157 3CS 206 223 185 ... 3*1 ... 404* a Day IS 46 90 135 25 S 350* 450* 329 ... E'ssed upon data from a study with adjustment for US mortality experience. tEHipses indicate rates omitted for calories with no subjects in this study. See Table 2. ^Includes cigarcTte smokers who also srncked pipe or ciar. Wen with a history of only cigarette jmoking have higher lung cancer rates than shown here. Spates obtained by smoothing the data. basis of general United States mortality data for divided into many five-year age groups, some of the white males. However, as previously mentioned, subgroups contained only a small number of rnen. evidence at hand suggests that there were propor In consequence, the lung cancer death rate was tionally somewhat more cigarette smokers among statistically unstable in some of the very small sub the 370 subjects than among white males in the groups. In three instances where the observed rate United States as a whole, age being taken into in a small subgroup appeared to be badly out of consideration. This might have partially accounted line, we arbitrarily made an adjustment to bring it for the high bronchogenic carcinoma death rate of more into line with adjacent figures in the table. the subjects. For this and other reasons, we made These adjusted figures which are indicated with estimates of the expected number of bronchogenic symbols in Table 4 carry very little weight in the carcinoma deaths, the smoking habits of the men final calculation. All of the rates were than ad being taken into consideration. This was done as justed as follows: follows: Lung cancer death rates in the United States Data are available on lung cancer deaths in re have risen steadily year by year and were higher lation to the smoking habics of 4 40,000 men en in 1964 than during the period 1960 to 1964 as a rolled by American Cancer Society volunteers in whole. Furthermore, in the study described above, a prospective epidemiological study between Oc we avoided enrolling seriously ill people and, as of tober 1S5S and March 1960 and traced through the cut-off date for preparing the computer tape, Sept 30,1964. Causes of death were ascertained from we had not yet received death certificates for all death certificates, but whenever cancer was men- of the men now known to have died during the tioned on a death certificate inquiry was made of specified period of time. For these reasons, lung the physician who signed the certificate. In case cancer death rates in the study population were of ^agreement bet"--i the two source of infor aporfv'iablv lower than those reported for white mation, the physician's statement was accepted. males in the United States in 1964. To compensate For the purpose at hand, we only made use of data for this, we raised the rate of each indi%'idual smok covering the 52-month period beginning on June 1, ing category so that the total lung cancer death 1960, and ending on Sept 30, 1964. The number of rate (disregarding smoking habits) in each five- lung cancer deaths occurring during the 52-month year age group would be the same as that of all period was divided by the number of men alive at United States white males (based upon the 1964 the beginning of the period. This was done by five- life table and the 1964 distribution of deaths by year age groups for men in each of the following causes of death). The results of these computations smoking categories: (1) never smoked regularly are shown in Table 4. (It should be noted that (nonsmokers and occasional smokers being com Table 4 shows only such rates as were required for bined); (2) history of regular pipe or cigar smok further calculations.) ing, past or present, but never smoked cigarettes The rates shown in Table 4 were then applied to regularly; (3) excigarette smokers (including those the number of asbestos workers shown in each of who had smoked or currently smoked pipes or the corresponding internal cells of Table 2. This cigars); and (4) current regular cigarette smokers yielded an estimate of the number of lung cancer (including those who also had smoked or currently deaths expected to occur during a 52-month period smoked pipes or cigars). The last of these cate among the 370 asbestos workers classified by their gories was further divided by current number of smoking habits. By "expected" number, we here cigarettes smoked per day: (4a) one to nine ciga mean an estimate of the number of lung cancer rettes a day; (4b) 10 to 19 cigarettes a day; (4c) deaths which would have occurred under the null 20 to 39 cigarettes a day; and (4d) 40 or more hypothesis that asbestos workers do not aider from cigarettes a day. Since the men were divided into other men in respect to their lung cancer death seven groups by smoking habits and further sub rates/, both ego and smoking habits being taken JAMA. April 8. 19S3 VoI 20<1, No 2 HER 0000730 110 execs Tit'* 5.--Observed and Exp'ictod Gronchorsnic Carcinoma Coaths by 3,-noVi.*3 Habits* for 370 Asbastos Workers Smoking Habits Kew>r smsVsd regularly 'History of pipe, cigar smoking only History of regular cigarette smokir.gt Observed Deaths 0 0 2* ejected 0 05 0.13 2.38 Total 24 2.1S Sased upon dita in Table 2 and Tsble 4. f Includes cigarette smokirs who )Uo smoked pipe or cigar. Table S.--Expected and Observed Deaths Among 632 Asbes-' tos Workers Exposed to Asbesto Dust 20 years or Longer Total deaths: all causes Expected Observed Total canr.*r all site* Expected Observed Cancer of lung, trachea, pf-rjra Expected"' Observed Cancer cf Mcmach. coJon, rectum E *d Observed Cancer alt other sits* combined Cxpected Observed Asbestoses Expected Observed All other causes expected Observed 1S43-1962 203.5 255 Total 1S&3-1567 1543-1SS7 47.5 94 2SI 349 35.5 95 36 49 <5.1 144 6.6 45 2.3 27 S.9 72 9.4 29 1.8 11.2 8 37 20.5 21 4.5 14 25 3S 000 12 IS 27 167 39.9 2053 143 30 173 into consideration. The results are summarized in Table 5 which shows the expected and observed number of lung cancer deaths in each of three smoking categories. Taking smoking habits as well as age into con sideration (Table 5) a total of 3.2 bronchogenic carcinoma deaths were expected whereas taking only age into consideration 2.3 deaths were ex pected from this cause (Table 3). Thus, perhaps ;..c of the excess bronchogenic care:--' na deaths might be attributed to the fact that there appear to ! ave been proportionally somewhat more ciga rette smokers among the 370 subjects than among men of the same ages in the general population. The following statements are based upon the data shown in Table 5. Twenty-four deaths from bronchogenic carcinoma occurred among the 370 subjects compared with only 3.16 expected, a ratio of about 7.6 to 1. This is slightly higher than found in our earlier study which indicated a ratio of 6.8 to 1 (not taking smoking habits into considera tion). It should be noted in this connection that the 370 subjects in this study had been expose-d to asbestos dust somewhat longer than the subjects of our previous study (the present 370 subjects are survivors as of Jan 1, 1953, of subjects in the previous study). Of the subjects who never smoked regularly and those who smoked only pipes or cigars, none died of bronchogenic carcinoma whereas 0.1S of these men were expected to die of lung cancer. Thi3 sug gests that exposure to asbestos dust dees not in crease the risk of bronchogenic carcinoma among --SELIXOFX ET AL men who never smoked cigarettes regularly. How ever, considering the small number of such subjects in this study, we only conclude that exposure to asbestos dust does not greedy increase the risk of bronchogenic carcinoma among men who never smoked cigarettes regularly. Twenty-four of the man with a history of regular cigarette smoking died of bronchogenic carcinoma whereas only 2.93 were expected to die of it, a ratio of 8.05 to 1. From this it appears that exposure to asbestos dust greatly increases the risk of lung cancer among cigarette smokers. Now we may ask how greatly is the risk of bron chogenic carcinoma increased by the combined ef fects of cigarette smoking and exposure to asbestos dust To answer this question, wre applied rates shown in Table 4 for nonasbestos workers who never smoked regularly to the number of subjects with a history of regular cigarette smoking as shown in Table 2. This indicated that only 0.26 of the subjects with a history of regular cigarette smoking would have been expected to die of bronchogenic carcinoma if they had never smnked regularly and had never been occupationally posed to asbestos dust. Since 24 of them actual.' ied of this cause, the ratio of observed to expected deaths is 92 to 1 (ie, 24 divided by 0.26 = 92). This appears to in dicate that cigarette smoking plu3 occupational exposure to asbestos dust increases the risk of bronchogenic carcinoma by a factor in the order of magnitude of 92 to 1. It should be noted that this estimate does not take current amount of cigarette smoking into consideration. Comparison With Earlier Findings.--As explained, we started with a cohort of 632 asbestos insulation workers, the entire membership of the union locals on Jan 1, 1943. We have now traced each man through April 30, 1967. Table 6 shows the observed r.nd expected number of deaths for each of two periods (the first, 1943 to 1952, being previously reported') and for the entire period. In respect to respiratory cancer (lung, trachea, and pleura) and in respect to cancer of the stomach, colon, and rectum, the findings in the two periods are in close agreement. Comment The increased risk of neoplasia (mainly broncho genic carcinoma arid mesothelioma) among insula tion workers reported here should be evaluated in the knowledge that these men have comparatively light exposure as asbestos trades go. Primarily em ployed in construction work, many of the materials they use contain little or no asbestos and others have only 5% to 15%. Conditions of work vary; these men often work outdoors unlike asbestos operators in factory work. Comparatively few dustexposure surveys have been made in this trade but their results have generally been within the 5 mil lion particles per cubic foot permissible limits cur rently accepted by the American Conference of Governmental Industrial Hygienists.*19 Nor have JAMA. April S. 1562 Vo! 2Ci. .\o 2 HER 0000731 /.SS'STCS F-X?OSlJf\E- - ~'L*\C.rr cT AL 111 additional potentially carcinogenic sub.-te:-.cc3 boon identific-d among the other materials used.10 " Heavier or even lighter exposure may result in different degrees of risk of neoplasia. Heavy factory exposure in the past has in some instances resulted in considerable lung cancer risk.11 In others, para doxically, little lung cancer was seen because asbestesis was so common and so severe as to cause death of the exposed workers before they could live long enough to develop lung cancer. Once exposure was rc-duced by improved industrial hygiene prac tices, early death from asbestosis sharply dimin ished and lung cancer became common.'1 Tn any case, heavy exposure is not likely to be the mast important problem in the future, unless there be sheer carelessness or unconcern. Rather, light exposure, similar to that in insulation work, will he much more common, both in direct asbestos working trades and as the result of indirect occupa tional exposure, as in the construction and ship building industries. There is another type of "light exposure'' which may affect many more people -.n those industrial ly exposed. In the past seve years, it has been demonstrated that asbestos ' tes can be found in the lungs of 25% to 50% of adults examined at autopsy in large cities, such as Belfast, Northern Ireland, Capetown, Republic of South Africa, Miami, Fla, Pittsburgh, and Montreal. This is presumably due to "asbestos air pollution" by fibers derived from industrial "spillover'' (as dust from construction sites or factory wastes) or from end-product use. Such community asbestos air pollution may be important since there is already evidence that in certain circumstances, as living within half mile of an asbestos plant or in the household of an asbestos worker, intimate environ mental contamination can be associated with some risk M mesothelioma." *Vnat is not now :cwn is whether the minimal amounts inhaled by the gen eral public carry a similar risk.'* Nor do we know whether inhalation of the very small amounts of asbestos present in the air of some communities is associated with a special lung cancer risk in cigarette smokers (or, conversely, whether cigarette smoking makes the inhalation of very small amounts of asbestos particularly hazard ous). Ii will be important to ascertain whether such cocarci.nogenic or potentiating or precipitating rela tionships exist because, with the rapid growth of asbestos use (500,000 tons per year world produc tion in 1930 has risen to over 4,000,000 tons par year now), it may be difficult for cigarette smokers to avoid inhaling air contaminated with asbestos. It may not be easy to unravel the interrelation ships which might exist between community as bestos air pollution and cigarette smoking. Both asbestos exposure and cigarette smoking have a long-lapsed period between onset of exposure and occurrence of neoplasia, yet for current smokers these two exposures may not have begun simulta neously; there was much lass asbestos used 20 to JAVA. April 8. '563 Vcl 2C4. No 2 10 years ago. Youngsters who start smoking now have a much greater chance of having both ex posures simultaneously. Significance of Findings for Asbestos Workers.-- The import of the data reported here seems clear. There is an extraordinary risk of developing and dying from lung cancer for asbestos workers who smoke cigarettes regularly. In the group studied, the combination of asbestos exposure and cigarette smoking increased the risk approximately 90 times compared with men who neither work with asbestos nor smoke! Of 283 asbestos workers who had a history of cigarette smoking, 78 died within a period of 52 months whereas only 32.4 would have been ex pected to die within that length of time if their age specific death rates h2d been the same as for the general white male population of the United States. Of the 7S deaths, 24 (31%) were due to broncho genic carcinoma. It is estimated that if these men had smoked cigarettes but had not been exposed to asbestos dust, only 2.98 would have died of bron chogenic carcinoma within the same length of time. If they had neither smoked nor been exposed to asbestos dust, only 0.26 would have been expected to die of the disease within a period of 52 months. Of 87 asbestos workers who never smoked ciga rettes regularly, none died of lung cancer within the 52-month period (although three died of asbestosis and one died of peritoneal mesothelioma). This finding, being based upon the experience of only S7 men, does not prove that exposure to asbestos dust has no influence on the risk of lung cancer among nonsinokers. However, it suggests that ex posure to asbestos dust does not lead to an ex tremely high risk of lung cancer among nonsmokers. The conclusions are evident; 1. Occupational exposure to asbestos dust should be reduced to as low a level as possible; but- there may be an irreducible minimum level if asbestos, a very useiul material, is to be used at all. Such reduction in exposure will benefit asbestos workers of the future. However, we are also concerned with workers who have already been exposed at signifi cant levels for many years. Asbestos fibers will re main in iheir tissues for the remainder of their lives. 2. All people incur a great increase in risk of lung cancer if they smoke cigarettes; for asbestos work ers the increase in risk is tremendous. Asbestos workers who do not now smoke cigarettes should never begin. Those who do smoke, should stop immediately. We may hope that the decrease in risk which results from cessation of smoking among the general public3 will be the good fortune of the asbestos workers as well. This investisMiun was supported by the Health Research Coun cil o' the City of New York. References 1. SfcllroEf. I.J".: Chuip. J.. nnd Hammond, EC.: Ashe-ilos Ex posure ar.ri Nccp'r.^a. .MAM \S$:22-2G (April C> X9W. 2. Setikotf. IChury. J.: and Hammond. E.C.: Relation Helw*en Exposure to Asbestos and Mcoolhelioma, fc'eiu Eng J Med 272:550 ooo iM^rch 18) 1965. * HER 0000732 J13 ASBESTOS EXPOSURE--SEUKCFF cT AL df. Ha.-n.-.-..uod. F. C.: "Smo'vir.g in Relation to the Death Rates of l.OCfj.OlO M,.n hrd Women." in EpidernioLc^iral Study of Cancer cud Other Chronic Diseases. Bethc-rda, Md: National C?ncer Institute, 1035, monograph 19, pp 127-204. 4. Synching end Health. Report of the Advisory Committee to the Surjwn General of the Public Kedth Service, publication 1103. US Dv-pt of Health, Education. or.d Welfare, 1S44. 5. Hammond. E.C., and G.vrhr.liel, L.: Chemrea in Cigarette Smoking 1959-125*7, Amer J Public Health f-3:3C-fo (Jan) 1S68. 6. Vifof Statistics of the United Sides. 1350, port A. US Dept of Health, Education, and Welfare, 1S63, vol 2. 7. Dcdh F.atee From Malignant Neoplasms, I?'SO, Public Health Service, publication 1113. US Dept of Health. Education, and Welfare, 1963. 8. Mortality by Occupation and Cause of Death. Public Health Service. US Dept of Health. Education, end Welfare, Vital Sta- tlstlea Division. Vit.il Stalls Sea--Special P-cpcria, 53:323 (Soft) 1033. 9. F!e:.cber, W.E., ct al: A Keolth Survey of Pipe-Covering Opera tiona in Cn.-j:r-jctinj Naval Vessel a, J Indus* Hyg Toxic 23:9-16 (Jan) 19-tA. 10. Keane, W.end Zevon. M.R.: OocupHtic-c.il Hazards of Pipe Insulator*. Arch. Environ Health 13:171-173 (Ac?) 1966. 11. Dot!. R.: Mortality From Lur.g Cancer in Asbestos Workers. Brit J lnduxlr .'.fed 12-.31-S6 (April) 1955. 12. Jacob, G.. and Anspach. M.: Pulmonary Neoplasia Among Dresden Athreaten Workers. Ann NY Acad Sc 132:536-543 (Dec 31) U-55. 13. Newhouse, M L., and Thompson. H.: Mesothelioma of Pleura and Peritoneum Following Exposure to Asbestoa in the London Area, Brit J Ir.dustr hied 22:261 -2S9 (Oct) 1965. 14. SelikoR. I-T., et el: Asbestoses end Neoplasia, Amer J Med -2:<37-436 (April) 1967. HER 0000733