Document rxOKYJZXVZJ4eeMB2DEba3gBr

FILE NAME: Smoking (SMOK) DATE: 1949 DOC#: SMOK031 DOCUMENT DESCRIPTION: Journal Article - Cancer and Environment 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 harely two generations <il<l. vet (lurin'; that short period literally thiMtsumls of ntiroly new' chemical anil t>liv.ieal Constituents have been aihleil to c 1 Miman environment. Kew of these eon- V intents have been exhaustively analyzed A m their long-range toxic eflcets on man. Tt-v are now being stiulietl. however, as possible contributors to the rise of cancer. The growth in the relative importance ot cancer as a cause ol death is one of the outstanding medical facts of the past Vi vears. The disease has moved from eighth to second place in the U. S. since 1900. and today only heart ailments surp -- it. The reasons customarily given for this rise--improved diagnosis and the a-jirg of the population--do not entirely explain it. They provide no satisfactory answer to the fact that approximately *-.-u 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 the disease is not an inevitable consequence of bodilv degeneration dm; to a"*-, although the changes of senescence under certain conditions may he con tributing factors, it seems certain that tl.-s- is a net increase in true cancer deaths, if only because fewer people die Iron* other diseases than in the past. \ m explanation of this increase and of the causes of the disease is therefore l**-ing sought in'uur environment, so much ..... complex than it was in 1900. The inw-tigation Is focused on carcinogenic att-nts. as tiie substance* that produce .i i t-r are called, mid -*n the general pie-lion n* die extent to which the in" e in cancer muv be .iiicd by agent* if In- environment tb" have liitlo-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* Ultraviolet rayt . X-rays - . Arsenic ' Atbatte* .* Oiramatai Nickel carbonyl . tfyllium 1 ; ' . ; Anlhroctn* oil Aromatic ominat Banzai . Carbon black Craosota Mineral oils Paraffin ail Polycyclic hydrocarbons Shala oil Soot Tor and Pilch Anilin* Azodyai Estrogant I -h " Schiftaiema hamelabium Virvias . . Oonorehit linansif C A R C IN O G E N S know n to he pres, cut m hum an c u \ ii-m uncm arc cla**i. lied. Less certain accn ts arc in italic*. exposure to them is sufficiently intense and prolonged. A* an example, over per cent of (he miners in the Srluieelierg cohultuiruniunt mines of Germane die of lung cancer: more than SO per cent *( those in the Joachimstiial uranium mines across the border in Czechoslovakia die of the same cause. In the 18th century it was learned that among chimnrv sweeps exposed to intense concentrations of soot, deal Its from cancer were between three and four times as high as those in the gen eral population. It is known also that certain common substances in concen trated doses can produce cancer: (or ex ample. mouth cancers are tineommonlv frequent in a tribe in India which smokes cigars with the lighted end in the mouth. This causes them to stiller frequent burns and to receive a concentrated dosage of tobacco tars. Ahbougb these are special cases of intense exposure, they naturally suggest speculation as *o whether the average human being's rdativdv mild hut liiugcuutiuucd exposin'., to new -uh-iaticr- in a contaminated atmosphere, in processed food*, in Cosmetic- and in other elements of our environment mav he a eonlriliiltorv can'*- n( cancer. We have as vet nn con. elusive evidence for or against this po--i. Iiililv. We have no accurate estimate of how many of the artificial 'iilistanmCommon to our indu-triul civilization mav he carcinogenic under special circuit'Stan**'--. Ilor ioov ir.nnv -o-emindv hurtuh -- uli*tances. interacting with othrr- dial appear to lie equally inunction-. mav pi. hire carcinogenic result*. T h e r e are. ol course, m a m theori.-* alioot c a n c e r 's 'm o - - * : chroni c i n t e r n - irritation- in tin- h*dv. c h a n - -* in cell . -r* 4 `Vf* .. ,.X*i .^>/,rf* iS%./; * . * , s' **** l-vr, ;. <-jV-. '.;' 1 /4 3.'VJ ^ * .ft \ K i >. ) f'v * ^ SINUS - Nickel carbonyl 4 MOUTH 8*f/nutand tobaccochawing ^ THYROID-Jodine deficiency ; ..'.* " i ^ BRONCHI Nickel carbonyl Radioactive subttance* - ^ LUNGS Asbetta* `g Chromate* '' Nickel corbonyi ' ' 7' ' RadioactivejubitaneM- *- Tar /uiiiM '* * *>\' ' , *'*'.< V-.-7 ; ' 7 4 UVER Dietary deficiency ^ KIDNEYS' Aromatic amine* & "2i -. * 'i> ' ' I'-UV. 'X ^ BLADDER Aromatic amines ^ i'Schiflosoma hematobium V , ' .yj'..,,;. ' . ^ URETER Aromatic amino* ^ SCROTUM Soot,tar and oil* *< . -'S V- : mcijlmli'iii. tissue degeneration. \ ami -<* im, Most of tin--c theories. how- i-vi-r. describe mechanism* rather than fir-t cause*. Indeed. with two or tnree o\- all of them seem to require the presence of a triggering agent. Possibly the must fruitful current theorv i* the one that attribute* cancer to muta tion* in Imdy 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 including the chromate-, the arsenical*, nickel carbonyl and possibly asbestos, cause cancer in this relatively roundabout 1-1 i r. * ^ .SKIN |Radioactive substance* Soot, tar and oil* -T'-.^-Ultraviolet rayt , .TV. a --lvj VBON.Eg&ABONE MARROW .. v`t-tsn-*irv'r-Btn--zol - - > ; . 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 ediate*, 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 ciTcct*: thev ran produce a wide variety of cancers. They may cause skin cancer hv direct attack mi the -kin. and lung cancer in people who inhale radioactive dust. When expi*sure is intensive and prolonged, as in the case "I the women who worked in the radi um watch and dock dial industry -mne 2.i years ago. they produce hone cancer. Ami 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 whose whole professional live* have been -pent in theoretically safe and well-protected dealing* with K-ravs or radioactive materials. -Mo-l subtle of ail carcino-a-ns are those believed to cause general metabolic disturbance* that produce cancers in a roundabout way. Thu* the liver may pro duce carcinogens that can cause it or some other tis-ue to turn malignant. Among the aoents thought to have this effect are the 12 L/# dv- uml certain chlorinated aliphatic hydrocarlMHi*. lint tin: mechanism in* volvcd i> * u|c*'ttrc that the earrfnogeu- Jetty of iln-w MiiMancc' ha* not been com- \e te !y proved. Ik ( hte a>|H*ct i( such indirect causation, however. is *ti*4-vpti|dc of proof. Among -me Negro trilic* working in the gold mine* <i( Africa, an executive incidence n{ cancer of iltc Itlatiilcr has liccn irucctl to deficiencies in the workers' diet. It was found tliut most nf the Negroes hatl lived litr year* on a vitamin-dclieient diet of |ia|> and sour milk. Only recently South Afri* can re^eurch worker* hate succeeded in producing cancer of tile-liver in rats fed just this diet. IN view of the relalite novelty of the con cept of environmental cancer, anti of the small amount of well-organized re search in this Held, it is not surprising that most of the known carcinogenic, agents have been found in industry. Here workers suiter exposures many times more con centrated than the average citizen en counters in a non-industrial environment. Fully VO per cent of the known carcino genic agents are industrial, ami a similar proportion of cancers of known cause aries from carcinogens of industrial im portance. These known agents are listed in the chart on page 11. The difficulties in the large-scale study .of carcinogenic agents are formidable. The modern environment is so ramified /h a t efforts to evaluate it in terms of longrange carcinogenicity may appear nearly ho|K.-less. 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 such a program is to l> successful. The two principal methods now used to uncover the more obvious occupational cancer 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 In-ing tested. Some that have been shown to he carcinogenic iit 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 urethan. ergot, sele nium. 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 p ro v e d h a r m l e s s to o t h e r s . F o r e x a m * )|de. certain tars, when correctly upplit-d. produce skin cancer in mice. rats, rabbits and dogs, hut not in monkeys. Hats and mice get skin cancer from ultraviolet rays, hut rabbits do not. The prohuhilitv is that specialized metabolism is at the bottom of this s p e c i e s -pecificitv for cancer. If su ch metuledir differences were completely un derstood. human brings might lie endowed with resistance to certain types ol cjincor by modifying the individual s metabolic processes. Such ideas are still beyond Ihi* realm of practical application in man. In experimental animals, however, cancer susceptibility or resistance to certain ex ternal carcinogens. *uch as several of the azo dyes, may he created at will by the omission or addition of certain vitamins in the diet. Without animal experimentation, scien tific proof of tlie carcinogenicity of various substances ami radiations would lie nearly impossible. On the other hand, laboratory experiments alone cannot prove definitely that such agents are dangerous to man. Ollier methtids must lie used, and the prin cipal instruments so far available huve been statistical studies and medical rec ords. In large, tinsclcctcd population groups, variations in the incidence of onu kind of tytneer are usually not sufficiently 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 discovered largely by clinical observation. Physicians practicing in ur ban or manufacturing ureas begun to notice a remarkably high incidence of cer tain types of cancer among workers in in dividual trades. Steli was the ease ill the diagnosis of cancer of the scrotum in chimney sweeps. Discoveries by direct ob servation continue to lie made, us in the ease of radium anil X-ray cancers that oc curred with alarming frequency among people working with these agents in the ml so distant past. BI T observation lias 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 tlie jolt is carcinogenic may escape notice. Characteristic of environmental ram-cr* is tlie long period between the beginning of exposure to the carcinogen anti the actual appearance of a tumor. A worker who leaves a dangerous job before the cancer appears may later develop a malignant tumor without realizing its origin. The process of tracing cancers to their source through medieut records and lu-ultli statistics has heroine a work of skilled de duction. When a given romnmnitv i* found, on careful examination of its illness and mortality statistics, to huve an unusual number of ease* of cancer in certain sites, tlie biometrieian at once suspects the pres ence of an uctivc environmental carcino gen. The chance* u-dav are very great that it will he traced to one or more factories in the urea, since so few nmi.iiiduslriul car cinogens have been lotitul. Conversely, if it is known that certain plants are pro. during or using known carcinogens, the statistician searches for evidence of an aI>normaI incidence of cancer .timing men who are'employed in these plants. Obviously 'iieli investigatiotis pr.--.-ot difficult problems and demand a high or der o f judgment. It has often been said tliut statistics can lie u*<-i| to prove Ih.iIi sides of a question. K.iivirniuneiiiul earcinogenesis is no exception. An example in American experience is Ustudy which was made --mu- time ago of the incidence of lung cancer among l(MXX) workers iu an industry suspected of pro ducing a carcinogenic agent. It was known from studies in other countries that lung cancers were exceptionally frequrnl iu this industry, and there was no evidence that the American manufacturing methods differed in any major respect from those abroad. ^ et this study reportixl no lung cancers at ail! In any group of -JO.IMKI adult males several cases of lung cancer are hound to occur, merely on the basis of the incidence* of the malignancy iu the population as a whole. The results of the study surely, suggest a lark of thorough ness in the collection and evaluation of data. A CI.KAK example of the intelligent tic of statistics as a tool in uncovering environmental carcinogens i* the way iit which cancers of the bladder were identi fied us an occupational hazard in plants Using the aromatic amine dye interme diates mentioned earlier. The following composite description, hosed on a unrulier of Kuropean ami American invesiigatiotis of this problem, illustrates tlie method: The people in a certain industrial re gion have a frequency of bladder cancer that is a slight fraction higher than nor mal. Tlie variation is well within tlie range of random probability, hut tile fact that several cases of this not too common ma lignancy have Itecii found in a single community leads to a further stndv of the region. It is found that the incidence of bladder cancer jump* from .02 |>er cent in the province as a whole to .1 |wr cent in thu particular community under study, an increase of -100 per cent. On further investigation it is learned that among the workers in a particular dye plant in the town. >per cent are suffering from or have died from bladder cancer-- nearly a 5.000 per cent increase. Follow, ing this clue, every operation in the plant is studied, and one particular job is found in which over 00 per cent of the worker* have bladder cancer <>r have died from it. Obviously tin- focal point of the disease ha* been established. It is from just such relatively slight statistical anomalies that much of the original evidence of carcinogenesis in in dustry arise*. O f course, a* more carcino gen* become known ami are added to tin list, the statistical techniquescliange. \\ ilia the cooperation of the industries involved, ntedieal and public health expert* go directlv into the plant* and -trnlv the ojieralion* anti llu* worker*. Often, however public medical aod death record* offer the 13 nly reliable source of information. Many . industries artualiv ilo mil know of-the ex--O-lenee of carcinogenic hazard* in their \tclrie.'The iudv i* *n new that only peeled. The inridenee of lung eaneer did not diminish: in fact soon afterward cuneers liegun to appear among workers who had lieeti exposed for iess than six vejr*. a c l o s e d : that the community l- protected by the prevention of the di-charge of car cinogenic wa.-tcs; thut factories br li censed and inspected; that worker- he /*> tyMant* in which the incidence of .-jvoilic much shorter period than had been pre provided with piutcclive clothing. e>tui]cancer* i* notoriously liijilt are aware of viously observed. Vi hat had happened was lucnt and medical supervision, including the problem. A few industries ilo know of that at the linmwhen the protective meas frequent and thorough physical examina the existence of carcinogen* in their ure* 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 drvcbqted their own method* of coping to improve production. The finer dust, the Institute, which is .t part of the U. S. with them. though present in a much lower conceit-- Public Health Service, is preparing an The reluctance of industrial manage tration than the original material, pene immediate, comprehensive campaign of ment* to publicize the existence of a car trated farther within the bronchi of the education and information, the purpose of cinogenic 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 plant* 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 ntukc factories em increased. surveys of major industrial areas in the ploying carcinogenic materials safe to nation. These studies are essential pre work in.- furthermore, sometimes retptire* 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 that Dr. Hticpcr has suggested. Manv of the control recommendations not. the competitive position of its product ming front more indefinite environmental admittedly are far-reaching in their impli- is endangered. Generally speaking, however, employ einrsfoarrmeantoiomn oarbeoruetspionndsuisbtlreiafloreathneeelructkhaonf City are the manv thousands of physicians who . Percent of total possible sunlight Skin cancers per 00.0C0 population have cancer patients in industrial areas or K` who actually are associated with factories. 1/ It is an unquestionable fact that an appre \ ciable number of occupational cancers -lip through the hands o f doctors uniden > DALLAS 60-- 80 percent 140 . ( tified. This is due in a great degree to a * ` -v ` " " X general ignorance o f the occupational as- I- : '/ : ^/iVieeecnts aodfeqcuaantceelry. iPnhfoyrsmiceiadnsofhatvhee nbeavseicr t \ NEW ORLEANS : 62-- 64 percent T29 symptomatic ami sociological factors in fJ \ * [ volved in identifying occupational carcino genesis. i/ PITTSBURGH: l' t HE medical profession should he bet t . 50-- 57 percent 37 T ( ter educated about tile need for ex haustive ease histories which carry the individual's job record in detail hack as far as 23 years, about the urgency of check ihnagzamrdesdicaaglasiunsspticcioarnesfoufl inepdiudsetmriaiol leoagniecealr DETROIT '.i 25-- 40 percent 24 studies of all the workers in a plant, and about the paramount importance of im pressing plant management with the seri CARCINOGEN IN N A T U R E is sunlight. Such natural carcinogens, however, ousness of the problem. are few. An abnorm ally high concentration of arsenic in drinking water The standard protective and hygienic lias been shown to cause cancer of the skin and internal organs. Infer-- measures currently used in industry to lion* of certain parasites have also been found to lead to inaiianant growths. emuhut industrial poisons and other health hazards are not always adequate for the agents, if and when they are discovered-- cations, 'tears of work will be require,! to control ni occupational cancer. The fol is a public health problem of considerable pul them into practice with maximal e:!ec- lowing ease history is a compelling illus magnitude.' This is made even mure ap tivencss. This is particularly true of the tration: Some 30 years ago workers in one parent by the scope of a control program recommendations tor social controls. On id the newer metal industries began to develop lung cancers. At that time the cancers were found to remain latent front Id to 15 vears. The incidence was iiuusit.t11v high in certain operations where the carcinogenic substance was present in par ticularly Idgii concern ration as an air borne dust. An ellort was made to safe guard lhco operations. I'p-to-date equip ment lor removing dust ami fu m es was installed, and a standard industrial hy giene program was inaugurated, ineluding protective clothing. I'ut the oiileome was exactly tin* opposite `ni what, had been ex- that has been proposed by Dr. Wilhelm C. If neper, bead of the new Environmental Caueer Section ol the National Cancer Institute. Dr. Ilueper. one of the world's leading experts no occupational cancer, lias studied the problem in the t '. ri, and elsewhere for many years. Several of the elements of hi* program have already been put into effect in European countries. The program proposes that carcinogenic agents lie eliminated trout industrial, inilitarv and civilian tt-c a- far a- i- possible and practical: that inuiiu tact tiring process, e* which must u-,. .ueh materials be en* tile technical -ide. sonic ol the elements can he instituted at once and without areal expen-e. it management and labor can he per-uaded to agree to them. for example, elb-ctive medical and sani tary 'upervi-ioii ol exposed workers can he undertaken immediulciv. This -upervi'inn should un hide \ -ra y examination- at Irequetii intervals; earelol clinical -inov "I suspicions lesions; preparation ol e\. Iiniisitvc and ,letatled' job anaiv-e- and eusi' liisioi ii's; regular ,|iiar;crlv ,r semi annual physical i iminutmii- ..I all , . . u s ers who might pos-ddv -oife;- expo-uie to A i t e carcinogenic agent!*: a constant review ' o{ dangerous plant operation* to enforce . constant go*>d housekeeping and to"check "v> the level of carcinogenic dusts, fumes, id mists. Protective 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 penditure* for management. In some in stances, entire factories would have In be rebuilt. Others would require costly waste-control equipment, sucit 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 tuber plants in the same industry were required to make the same improvements at the same time. r TN some instance*, such changes might possibly lie undertaken as a result of m 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, tile 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 by the successful control n( 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 hazards of still undiscov ered environmental carcinogens is a question that only time can answer. Mean while. tiie known causes of occupational cancers would be placed under technical and social restraint, and putterns would be established for the future control of new carcinogens as thev are found in our -3environment. Grofj Conklin is ft ictnice writer anti a fanner consultant with the .Votionttl Cnnrer Institute. E X T R E M E CASE of environm ental emteer is represented liv rceoril of aro m atic uinitic plant in G erm any. <K workers direel ly in eontaet with cltcuiieul. 90 to 100 per rent developed etmeer of the bladder. Running from top to bottom is illustration of statistical analysis u.*eil to locate such hazards.