Document BykoLo76RN7okG8r586G6Zmdj

FILE NAME: Kent (KNT) DATE: 1949 Jan DOC#: KNT114 DOCUMENT DESCRIPTION: Journal Article - Cancer and Environment Scientific American V SCIENTIFIC AMERICAN VOL. 180. NO. 1 CANCER AND ENVIRONMENT Scientific and technological progress have exposed man to new physical and chemical agents. Some are believed associated with the rise of cancer as a cause of death by Groff Conklin THE industrial era in its full expan sion is barely two generation- <il<l. vet during that short period literally thiMtsumls of ntirely new chemical ami t>liv-ieal Cnn-littienls have been added tn c ' Miman environment. Kew f tiu*se oi.itYintents have liven exhaustively analyzed A m their long-range toxic effect* on man. T im are now living studird. however, as p*-ihle contributors t the rise of cancer. The growth in the relative importance ot cancer as a cause o| death is one of the outstanding medical facts of the past Vi vears. The disease has moved from eighth to second place in the 1!. S. since I'WKl. and today only heart ailments *urp -- it. The reasons customarily given for this rise--improved diagnosis and the aging of the population--do not entirely explain it. They provide no satisfactory answer to the fact that approximately -.ii and a half per cent of the known cancer deaths in 191 I occurred in age groups under 40. These is evidence, more -i. that tile disease i- not an inevitable coii-e<]itetice of Inulilv degeneration dm; to ag*-. although the changes of senescence under certain conditions may lie con tributing factors, it seems certain that tl.-s- is a net increase in true cancer deaths, if only because fewer people die from other diseases limn in the past. \ m explanation of this increase and of the raitscs of the di-eae is therefore Ic-ing -ought in our environment, so much ..... complex than it a- in 1900. The in'-ligation 1* fucu-cd on carcinogenic att-nts. as the sub-lances that produce .i i t-r are called, and - n the general pie-lion .i* ;lio extent to which the in i ' -e in cam-er muv he .iti-ed liv agent* ii' In- environment tb-o have Itith'-i't** been considered comparatively harmless. It has been established that certain agents to which people are exposed in in dustrial occupations cause cancer if tltc Alpha rays Bata rays Gamma ray* 1 Ultraviolet ray. ; . X-rays - . A nanie ' Asbestos i .* Oiramatas Nickel carbonyl . Bacyll/vm # /A' |; .. i-r/.CvV-' Anthracene oil Aromatic ominas Benzol . Carbon black Creosote Mineral oils f araffin ail ' Polycyclic hydrocarbons Shale oil Soot Tor and Pilch Am'/ine Azodyes Estrogens I ,-. ,-ri Sehiftaiema hemelahium Vtrwses . . Oonorehit sinensis CARCINOGENS known to In* pres ent m human eu\ iruunient are ela*-ilied. Less certain audits are in italic-. exposure to them is sufficiently intense and prolonged. A* an example, over per emit of (lie miners in the Srluieelierg cohult.iiranium mines uf Germane die >f lung cancer: more than SO per rent of those in tile Joaeliimstiial uranium mines across the border in Czechoslovakia die of the same cause. In the 18th century it was learned that among chimnev sweeps exposed to intense concentrations of soot, deal Its from caneer were between three and (our times as high as those in the gen eral population. It is known also tlut certain common substances in concen trated (loses can produce cancer: for ex ample. mouth cancers are tnieommonlv freipient in a tribe in India which -ittoki-eigars with the lighted end in the mouth. This causes them to suffer freipient burns and to receive a concentrated dosage of tobacco tars. Although these are special cases of intense exposure, iliey naturally -iigge( speculation as * whether tile average litiitiun being's relmivelv mild hut longcontinued exposure to new -uh-ianee* in a contaminated atmo-phere. in proee-*ed food*, in cosmetics ,md in other rlentenfof our environment tnav lie a contributor'eau-e of cancer. We have as vet no con clusive evidence lor or against this pu-sj. hililv. We have no accurate estimate of how many of the artificial -abstain o. Common to our indu-lrial civilization muv he carcinogenic under special circuit1-lane..-, lo.r loov n-.aov -.-eminglv harm!' -- Mili-tunce. interacting with other- ;h;il appear to he equally iunocuou-. mav o. ilin-e carcinogenic re-nils. T h e r e arc. ol cour-e. m a m tlieori.-s a b o u t c a n c e r 's c.in-o: c h r o n i c i nt e r n i r r i t at i on - in (In- Imdv. c h a n g e in cell `Vf* .. ,.X*i _^>/,,Vrt^*V `if%*/.; -TS**.1** * . * , v ** i /* .'VJ 3 ^ * K . f t \ i >. ) fit, K.-.*. "- . ^ SINUS - Nickel carbonyl 4 MOUTH total nut and tobaccochawing ^ THYROID-Jodine doUaoncy ; ..'.* " i ^ BRONCHI Nick1 carbonyl Radioactive subttanco* - ^ LUNGS Asbotto* `y Chromate* '' "Nickel carbonyl ' ' 7' ' RadioactivejubitaneM- *- Tar /urn! ' t ' , V-.-7 ; ' 7 4 UVER Dietary deficiency ^ KIDNEYS' Aromatic amine* 'i"2; - ''A ' ' .vll1;'. 'X ^ BLADDER Aromatic amines ^V2i',S'ch.if^losomga he'matobium ^ URETER Aromatic amino* ^ SCROTUM Soot,tar and oil* > . -'S V- : mcijlmli'iii. iis*uc degeneration. \ ami -<* im, Most of tin--c theori-*. howi-vi-r. describe mechanism* rather than fir-t cause*. Indeed. with two or tnree o\i't'|ilions all of them seem to require the presence of a tri^jifritt" agent. Possibly the most fruitful current theorv i* the one that attribute* cancer to muta tion* in ImkIv cell*. Cancer-causing muta tion*. it ha* been demonstrated by experi ments. may he produced hv ultraviolet radiation. X-rays, radiouctive substances, and a number of chemical*. While more than 99 per cent of all cancers are still of unknown origin. nearly all of those for which a proved cause has been found arise a* the result of external agents. These seent to mutate the cells into a state which is. or ran become, cancerous. The method* by which these external agent* act upon the body vary consid erably. depending on the substance in volved. Sonie carcinogens may cause cancer directly. Examples of these are tar. the mineral oils and certain dye intermedi ate* known a* aromatic amine*. Tar* gen erally aifeet the skin. Mineral oil* may cause cancer <>f the lungs through inhala tion. The aromatic amines, strangely, con centrate on the bladder, no matter what their route of attack. Whether they enter the Imdv through the respiratory system, the mouth or the skin, they gravitate to the genilo-urinary system and there build up a concentration that eventually causes cancer. Other agents seem to cause cancer by altering organs so that the organ itself pro duces a carcinogen, resulting in a cancer. The mechanism of this transformation is little understood. It is known that some radiation* and certain metallic compounds hit-lulling the chromate-, the arsenical*, nickel carbonyl and possibly asbestos, cause cancer in this relatively roundabout i-1 i r. - ^ . SKIN I Radioactive substance* Soot, tar and oil* 7'.`^z!4Jltraviolt rayt , - . IvJ <*BONE;&\BONE MARROW A*>'&'rtn*ol '.-i-f O RIG INAL SIT E S of uiulism m t growths dm: to carcinogen* in the en vironment are scattered among almost all the organs of the body. Some agent.-, such a* the arom atic am ine dye interm ediates, regularly alTect the same organs even' though they may use any one of many route* for attack. RADIOACTIVE materials are lr*s spe cialized in their ciTcets: thev ran produce a wide variety of cancers. They may cause -kin cancer hv direct attack mi the -kin. and lung cancer in people who inhale radioactive dust. When expo sure is intensive and prolonged, a* in the case "I the women who worked in the radi um watch and dock dial industry -nine 2-i years ago. they produce bone cancer. And a slight but very prolonged exposure to penetrating radiation can result in leukemia, a cancer of the blood cells. The latter kind of cancer is often found among radiologists who*e whole professional live* have been -pent in theoretically safe and well-protected dealings with K-ravs or radioactive materials. Mo-t -ubllc of all carcino-a-ns are tlio-e believed to cause general metabolic di-turbauce* that produce cancers in a roundabout wav. Thu* the liver may pro duce carcinogens that can cause it or some oilier tis-ue to turn malignant. Among the agents thought to have this etTect are the 12 L/ <Iv-* uml certain chlorinatisl aliphatic ItyilriM'arlMHiv lint tin: mechanism in* vniwil i- mi leo-ure that live earrfnogeu- by of the* Miltaiiii - ha* not licvn com\e te ly prve!. Ik <hie a*|*cet of Mich indirect cau*atin. however. is -n-coptildc of priMif. Alunno -me Negro trilli:'* working in the gold tuiuv--of Africa, an vxv***ivv inchlemc n{ cancer of the hlutiilcr ha. licci! Iraceti to ilflicicncim* In the worker' ilict. It was found thut most of the Negroes hail Uvetl lor year ml a vltaminilelieient ilii-t of pup anil Mitir milk. Only recently Smith Afri* can research worker have ueeeeileil in pnlucino cancer of the-Iiver in rat fed just thi diet. IN view of the relative novelty of the con cept of environmental cancer, and of the malt amount of well-tirganize! recarrh in thi Held, it i not surprising that most of the known carcinogenic agents have been found in industry. Here worker ulTer exposures many time more eoneentrated than the average citizen encounters in a non-industrial environment. Fully VO per cent of the known carcino genic agent arc industrial, ami a similar proportion of cancers of known cause arie from carcinogen of industrial im portance. These known agents are listed in the chart on page 11. The difficulties in the large-scale study .f carcinogenic agent are furmiduhle. The modern environment is so ramified /h a t efforts to evaluate it in terms of longrange carcinogenicity may appear nearly lnqicles. Nevertheless, the techniques al ready developed in the study of occupa tional carcinogens may he of some value in analyzing the environment as a whole, even though more refined methods may have to he developed if uch u program is to l> successful. The two principal methods now used to uncover the more obvious occupational eaneer hazards are animal experimenta tion and statistical analysis. Cancers have liern produced in experimental animals iiv most of the known physical and ehemicul carcinogens. Hundreds of other substances have lieen and are lieing tested. Some that have been shown to he carcinogenic itt animals have not as yet been proved dan gerous to man. or else thev do not form a part of his normal environment. Among these substances are urethun. ergot, -elcilium, and diethylene glycol. One aspect of the work on animals that is important in considering human cancer i- the phenomenon known as "species specificity." Many carcinogens that cause cancer in some animal species have thus far proved harmless to -alters, f'l.r exam* )|de. certain tars, when correctly applied, produce .-kin cancer in mice. rats, raliliits ami dogs, hut not in monkeys. Hats and mice get -kin cancer from ultraviolet rays, hut rabbit- do not. The proliahilitv is that specialized metabolism is at tile bottom of this specie- -pvcifirirv for'cancer. If such metaieilie ilifTeretiee- were completely tin* dersttM|. human bring- might lie endowed with resistance to certain types ol cjinccr by modifying the individual's metabolic proces.es. Such ideas arc still beyond the realm of practical application u man. In experimental animals, however, cancer susceptibility or reitanee to certain ex ternal carcinogens, uch as several of the azo dyes, may he created at will by the mission or addition of certain vitamins in the diet. Without animal experimentation, scien tific proof of the carcinogenicity of various substance and radiations would he nearly impossible. On the other hand, laboratory experiments along cannot prove definitely dial such agents aru dangerous to man. Ollier methods must lie used, and the prin cipal iistriimcuis so far available have been statistical studies and medical rec ords. In large, unsclvctcd population groups, variations in the incidence of onu kind of Ciineer are usually not -idlieicntly marked to lie significant. That is why environmen tal carcinogens are usually difficult to de tect. Up to half a century ago. indeed, evi dence of specific extrinsic causations of cancer was di-covercd largely by clinical observation. Physician practicing in ur ban or muiiuiuetiiring ureas began to notice a remarkably high incidence of cer tain types of eaneer among workers in in dividual trades. Stcli was the ease in the diagm>sis of eaneer of the scrotum in chimney sweeps. Discoveries by direct ob servation continue to he made, us in the ease of radium ami X-ray cancers that oc curred with alarming frequency among people working with these agents hi the ml so distant past. BI T observation has its limitations. Un less very careful medical record* are kept, or unless workers remain in a car cinogenic job for many years, the fact that llie jolt is carcinogenic may escape notice. Characteristic of environmental cancers is tile long period between the beginning of exposure to the carcinogen and the actual appearance of a tumor. A worker who leaves a dangerous job before the eaneer appears may later develop a malignant tumor without realizing its origin. The prove- of tracing eaneer to their source through medicut record anil lu-ultli statistics bus heroine a work of -killed de duction. When a given romniunitv i- found, on careful examination of its illne-s ami mortality statistics, hi have an uuu-iuil number of ease of cancer in certain sites, tlie bionietrician at once suspect* the pres ence of an uctivc environmental carcino gen. The chance- tdav are very great that it will be traced to one or more factories in the urea, since - few non-iiuliistriul car cinogen* have been louiid. Conversely, if it is known that certain plants are pro. during or using known carcinogens, the statistician searches for evidence f an abnormal incidence of eaneer among men who are'employed in the- plant-. Obviously iii'li investigation* pn-..-.u d'dlirull problem- ami demand a high or- iler of judgment. It has often been -aid that statistics can lie u*el to prove Iii|i sides of a question. K.iiviroiimeiilal earcinogenesi* is no exception. An example in American experience is a study which va inaile -oine time ag of the incidence of lung eaneer among K).(XX) workers in ail industry suspected of pro ducing a carcinogenic agent. It was known from stmlies in other countries that lung cancers were exceptionally frequrnl in this industry, and there wa* itevidence that the American manufacturing mcth<l differed in any major respect from t!u*e abroad. ^ et this study reported m lung cancers at ail! In any group of -lO.tMKi adult males several case* of lung cancer are limimi to occur, merely on the basis of the incidence of the malignancy in the population as a whole. The results of the study surely, suggest a lark of thorough ness in tbe collection and evaluation of data. A CI.KAK example of the intelligent u-e of slutislies a* a tool in uncovering environmental carcinogen* i* the way in which cancers of the bladder were identi fied us an occupational hazard in plants using the aromatic amine lye uterinediate* mentioned earlier. The following composite description, hosed on a uumia-r of European ami American investigation* of litis problem, illustrates the method: The people in a certain industrial re gion have a frequency of bladder cancer that is a slight fraction higher than nor mal. The variation is well within the range of random proliahilitv. hut tile fact that several cases f thi* not too common ma lignancy have lieen found in a single community leads to a further studv of tile region. It is found that the incidence of bladder cancer jumps from .02 jrr cent in the province as a whole In .1 |wr cent in the particular community under study, an increase of -100 per cent. On further investigation it is learned that among the worker- in a particular dye plant in the town. 5 per cent are suffering from or have died from bladder eanci-r-- nearly a 5.000 per cent increase. K<>IIw. ing this clue, every operation in the plant i- studied, and one particular job i- found in which over 00 per cent of the worker* have bladder cancer <>r have died from it. Obviously the focal point of the di-ca-e ha- been established. It i* from jii-t -uch relatively light statistical anomalies that much of the originai evidence of carcinogenesis in in dustry arises. Of cour-e. a* more carcino gen- become known ami are added to tin list, the statistical tec!iiihpirchange. \\ ith the c.Miperation of the indu-tric* involvl. nicdii'al and public In-allh 'Xpert* g liriM-tlv into the plant- and -tuilv the o|eratiil ami tile wi ker-. Ofti'ii. Uwev-r public liielical and death rvet.nl- .lf*r the 13 nfy reliable source of information. Many . i.diilfies actually tin mil knw of-the ex--O-Ii.-wm* of carcinogenic hazard* in their \iclorie. The -tmlv - new that only peeled. Tile inridenee of lung cancer did not diminish: in fact soon afterward can cers liegun to appear among workers who had Im-cii exposed for iess than ix yejr*. a elo'cil; that tile eimuniinity In- protected hv tile prevention of the di-charge careinogenic wastes: that factories br li censed and inspected; that worker- lie /*> giants in which the incidence of .-H-cilic much shorter period than had been pre provided with ptoicclivc clothing. e>t:iip- cancer* i- notoriously high arc aware of viously observed. Vi hat had happened was iiicnt and medical supervision, including the problem. A few industries <lo know **f llial at the timewhen the protective meas frequent and thorough phy-icui examina tlic existence of carcinogens in their ures were adopted the factory had also tions. plant*, and probably some of them have begun to use a more finely ground materia! The Environmental Cancer Section of drvi.-hqml their tiwn method* of coping to improve production. The liner dust, the Institute, which is t part of the U. S. witli them. though present in a much lower conceit-- Public Health Service, is preparing an Tite reluctance of industrial manage tration than the original materiul. pene immediate, comprehensive campaign of ments to publicize the existence of a ear* trated farther within the bronchi of the education and information, the purpi--c oi oinngenic hazard is understandable, for it lungs. Thus despite the installation of the which is to bring physicians to a realiza Could easily become difficult for plants so latest in protective devices and pro tion of the existence of the problem. Plans labeled to recruit workers, or even to sell cedures. the cancer hazard was actually are also under wav to make exhaustive their commodities. To ntuke factories em* increased. surveys of major industrial areas in the ploying carcinogenic materials safe to nation. These studies are essential pre work itu furthermore, sometimes retptires extensive and costly alterations. If one firm makes such alterations and others do IT is obvious., there fore, that the control of occupational carcinogenesis--and even to a great extent of cancers stem liminaries to the institution of the controls tiiat Dr. Htieper lias suggested. Manv of the control recommendations not. the competitive position of its product ming from more indefinite environmental admittedly are far-reaching in their impli- is endangered. Generally speaking, however, employ einrsfoarrmeantoionnoiarbeoruetspionndsuisbtlreiaflorcathnecelructkhaonf City . Percent of total possible sunlight Skin cancers per '.OO.OCO population are the manv thousands of physicians who have cancer patients in industrial areas or r - *; ., .; ^ \ who actually are associated with factories. It is an unquestionable fact that an appre K` 1/ 'j \ -^DALLAS / 60-- 80 percent 140 ciable number of occupational cancers lip through the hands of doctors uniden > tified. This is tine in a great degree to a ""X general ignorance of the occupational as- I- * ` : -V-v ` : ( Vccts of cancer. Physicians have never t \ NEW ORLEANS : 62-- 64 percent ^/iieett adequately informed of the basic symptomatic and sociological factors in f \ ,*-< . ' [ volved in identifying occupational carcino J * . 29 T I geneHsiEs. medical profession should lie bet l!It' / PITTSBUR. GH : 50-- 57 percent 37 ter educated about the need for ex haustive ease histories which carry the individual's job record in detail buck as far as 25 years, about the urgency of cheek ing medical suspicions of industrial cancer DETROIT ' 25-- 40 percent 24 hazards against careful epidemiological .1 studies of all the workers in a plant, and about the paramount importance of im pressing plant management with the scri- CARCINOGEN IN N A T U R E is sunlight. Such naturnl carcinogens. however, onsness of the problem. are few. An uhnormully high concentration of arsenic in drinking water The standard protective and hygienic has been shown to eause cancer of the .-kin and internal organs, Infer-- measures currently used in industry to lion s of certain parasites have also been found to lead to inaiianant growths. eoiuliat industrial poisons and other health hazards are not always adequate for the agents, if and when they arc discovered-- cation-, 'tears of work will be require,! to control of occupational cancer. The fol is a public health problem of considerable pul them into practice with maximal o.dec- lowing ease history is a compelling illus magnitude. This is made even more ap tivene--. This i.- particularly true of the tration: Some 30 years ago workers in one parent by the scope of a control program recommendation- tor social controls. On it the newer metal industries began to develop lung cancers. At that time the earn ers were found to remain latent front II) to 15 years. The incidence was uiiusttullv Idglt in certain operations where the eareitiogenie substance was present in par ticularly high concent ration as an air borne dust. An ollort was made to safe guard lhce operations. l 'p-to-dute equip ment lor removing dust ami fumes was installed, and a standard industrial hy giene program was inaugurated, ineluding protective clothing. I'ut the outcome was that lias been pn.pi.-od by Dr. Wilhelm Cl If neper, head of the new Environmental Cancer Section ui the National Cancer Institute. Dr. Ilueper. one of the world's leading experts on occupational cancer, lots -imbed the problem in die l'. ci, and cl-cvvilcre for many years. Several ol the elements 'o f hi* program have already been put into effect in European countries. The program proposes that carcinogenic agents lie eliminated Iroui iinlu-irial. mili tary and civilian u-c a- far a- i- po--hie and practical: that uiuiiulaeturing process tile technical -ide. sonic ol the elements can he in-lituted at once and vvitliout great expense, it management and labor can he per-oaded to agree to them. for example, elh-etive medical and -anitary -upervi-ion ol exposed worker- can lie undertaken imtucdiulclv. This -upervi-ion should un hide \-ra y examination- at Iroquetii interval-; cardili elinical -inde "I -u-pieiou- le--ion-: preparation ot e\. ban-live .old Uetatled' j.*b aualv-e- and ''a-,- Id-loi ie-: regular >|iui:.'rlvor -endannual phy-ieal i x.iminatioo- -< all-work exactly the opposite ..I what, hail been ex- es which must u-e -ueh material- be en- er- who might pos-iblv -iilicr espusine to A it carcinogenic agents: a constant review ' o{ dangerous plant operations to enforce . constant go*! housekeeping and to"check "vi the level of carcinogenic dusts. fume*, id mist*. ^ P rotective measures for the workmen themselves are also simple and relatively inexpensive, although the enforcement of their use is sometimes made difficult by the discomfort they cause. They include the regular wearing of respirators and sealed clothing whenever exposure to a carcino genic hazard is likely, daily showers for all persons working in or near the hazard ous operations, use of separate lockers for street and work clothes, and adoption of work techniques that will minimize the dangers of exposure. Other, and more important, technical measures are likely to involve heavy ex penditures for management. In some in stances, entire factories would have lo be rebuilt. Others would require costly waste-control equipment, such os elec tronic dust precipitators, and extensive remodeling to enclose carcinogenic opera tions and keep the workers from any con tact with dangerous agents. Few plants could afford the necessary changes unless all other plants in tiie same industry were required to make the same improvements at the same time. r TN some instances, such changes might possibly he undertaken as a result of l i industry-wide agreement. In others, leg isla tiv e and administrative enforcement might he essential. Such action would in clude factory licensing and inspection by government, improved compensation laws recognizing occupationally acquired can cers as compensable, and revision of the health codes to make occupational cancers notifiable just as are many other diseases. These measures would require coordinated and carefully planned action on the part of management, labor, the medical profes sion. state public health and labor depart ments. and state and Federal legislatures. A precedent for such a program has al ready been set hv the successful control of communicable diseases through public health laws and through the organized cooperation in their enforcement of both private and public agencies. How effective these controls would be in diminishing the hazard# of still undiscov ered environmental carcinogens is a ques tion that only time can answer. Mean while. tiie known causes of occupational cancers would be placed under technical and social restraint, and putterns would -3be *-stablisited for the future control of new carcinogens as thev are found in our environment. Grofj Conklin is ft sci ence icriter and a farmer consultant uitli the .Vtiontil Cttnrrr Institute. E X T R E M E CASE of environm ental emteer is represented liv record of aro m atic uinitic plant in G erm any. <K workers direet !y in eontaet with eheuiieal. 90 to 100 per rent developed cancer of the bladder. Running from top to bottom is illustration of statistical analysis used to locate such hazards.