Document da3xYzLGMReZaYgadE6e462NQ

Brit. J. imiustr. A/tv/., 1955, 12, 81. MORTALITY FROM LUNG CANCER IN ASBESTOS WORKERS BV RICHARD DOLL From the Sttiihmal Ratunlt I'nii, Mc.lntil Racurch Council, I oiiiIoh (XtOEIVI.D I OR PUBLICAlk.K Al'OtSf 10, 1954.) Sixty-one cases of lung cancer have been recorded in persons with asbestosis (Bocmkc. 1953 ; Hueper, 1953) since Lynch and Smith (1935) reported the first case. In view of the infrequency of asbestosts. this large number of cases suggests---but does not prove--that lung cancer is an occupational hazard of asbestos evorkets. The strongest evidence that tt may be a hazard has been produced by Merewether and by tiloyne. Merewether < 1949) found that lung cancer was reported at necropsy in 13-2.. of cases of asbestosis i.M out of 235) but in only l-.V',, of cases of silicosis <9| out of 6,884) and Gloync 11951). on personal examination, found lung cancer in 14-1 of necropsies on subjects with asbestosis (17 out of 121) against 6-9'1,, m silicones (55 out of 7%i. Neither author cave full details of the sex compo sition of the groups examined, but since women form a higher proportion of asbestos workers than . of persons employed ut occupations liable to give rise to silicosis' (coal-miners, stonemasons, pottery workers, fuundrymen, metal grinders) and ince lung cancer Is less common among women, the ditfercnces in the proportions of cancer cases cannot be accounted for by ditfercnces m sox distribution. In fact the proportions which are more properly eompaiablw with the findings in silicotic subjects arc the proportion ol lung canect found among men with ashestosis. 17-2".. in Merewether s series and 14in CiluvneN. Animal expeiintents are inconclusive. A positive result was reroried by Noidmann and .Sorge (1941! who tounu that of 10 mice which had been exposed to asbestos dust and survived for 240 days, two developed lung carcinoma. Smith (|9*2). however, considers that one ol the "carcinomas'* was. in ,lacU_an example of squamous metaplasia and tha the oilier, an adenocarcinoma, may have developed spontaneously 'rom the common mouse adenoma. A negative result has been reported bv \ orwald and K.arr (I93X), The niaioiity nf workers (cited bv Hueper. 1952) consider that a causal lelationship between asbestosis and lung cancer is either proved or is highly probable and the reality of the relation-hip was agreed at the recent International Sym posium on the Endcmiology of Lung Cancer (Council of the International Organizations of Medical Sciences. 1953). A minority, however, remains sceptical (Cartier. 1952 ; Warren, 1948). and.according to Hueper(1952). t an/a and Vnrwald. so that it was thought desirable to undertake a Ircsh investigauon. Necropsy Data Since 1435. records have been collected of all the coroners' necropsies on persons known to have been employed at a large asbestos works.* Patho logical diagnoses m 105 consecutive cases are summarized in Table I. Details of the cases in . Tahlf I i vt sts hi hi vtii ni voNcsr.i) vr mioropsy among pi know rvu'irivm at an vshi.sio.s works ijvjj-s:. 1 .MI'l' t`` r>C4fil " Hf-jit laiUnc OPi iuflbinnv'i!'r u*1^'%t.4cr,ri*e*\ MMvr <Hl*H ,.s.a*t,` V.l , iLXfX ihc rvsfitjtoty Pfi'Netn U I5 li> A'kMi'M' Ahciu i!14 } 4 Jo All Cite* 4< 18 105 which lung cancer was found arc shown in Table 2. During the first half of the period eight deaths occurred in which lung cancer was found in asso ciation with axheMosiv while in the second half of the period there weie seven such cases and a futther three in which lung cancer was ftumd without asbestosis. The nmnlvi of asbestos workers employed at the works increased steadily from 1914, * ,ixh*xV* in in hn i*i'iiin*n '.hcrv nji hi .ice 'fsHfid h\ the cfcner hen '`lien "i .vhfvim,t j coni.'i. twswww__e? WAS NX * 2 BB 0007317 | GG 1532b ^' s: BRITISH JOl RS'AL OF i\Dl STRl.-tL Ml'.DICISF. T\<n.i 2 Mt l R\!iriN\l lllsrOKV AND M ( ROPSV DATA ul vxilt ST OS VVORKI-KS WITH I'KIM.vRV LI Nfi < *N< t-R N (ef IV-llft 4\',,* m k: M. *4 \l ft* I**1ft VI 41 \1.4*1 1**441 m I'Ul m *: W4i M. ** 194ft M *9 !`0< M.M |94K M. 4ft M ft* K_ V mM M '4 M f*) 1 PcnoJ E*pour Wcgi rf |9!9 M Mrjtcr ; 1 ibcri/er Dkirtteyrtfier Bj* tart>fr 1`jn v* tv1 pwWP|VnM>:Mop1>--1.:1I1t<25ivf741 riv* i-iv \ IV24..M |V|.V 4t . \f mIVIS; -W14 1V22-.15 Spinner (v22 4> Maintenance nun 1414 4* ftpinner 1*415 42 1 heri/cr Header 191* 4.1 \ t29 :*5l \ (gft hxpi^uii 1'' ,2-5 i IM 24 4* |YVeaprH**ttiJ*f` K*l*rt Jaot,.\\L i* s l` 14 f i; >ifrtfoi.r1n\li!l ** 1 lentft 16 26 23 :* 2S 2S 211 14 2.4 2* 19 29 -1- O 1ft I* 2ft 2b to 2ft > ! \ 2s 2i r J5 2ft 1*1 .u l M I1Ufo\*>:'*l1elo>a-r1rij*i,fbhel y \ l.rs*. itun 1 1 1 ess than 1 I 1 I 1 rw titun 1 11 Less mar. 1 Ll** tHdA 1 N << 1 I'jih.,'iock^l Report ll*l*M*vi4T*ul<r*'ML*euanl gT^Cpmevuefr Pre^iti H '* t *' ^.-Mihelul carcinoma l-:>4*tlKliPma ofplctjrj " < .irciftmtii ** ' i .ircmoma ** 1 ( '.ircinoma " - Oai^cetkd nrcitH^ma (cimnoi'U * AnepUMiC careimii'u M '* C nviiH*m ** " \ jKinonu * OjKciletl certifto ru " l jMrtomH " ,, AtletiocarctiMMiu " ( arcinonta ' f *44 M W* N^i'jter r*M M 4` 1 iftciizer ,g.2 M. Weaker pu: 44 |19 4rf i |W4| 1 i |2 u 7 U l.e tMn 1 <1 12 .1 0 It l.es5, ihaii 1 Oji-cellfsJ t,Aainon'. -VftapUlttc uranonu " t, arcinor.i* " * Mvi imoiiiirt I.,'.VfC'MitMS. and a great increase in the number of lung cancer deaths, was also recorded among the whole popu lation of 1 ngland and Wales over the same period It might, therefore, have been anticipated that a larger number of cases in wltich the two conditions were associated would have been found in the-last 10 year-. National regulations for the control of asbestos dust were, however, introduced in 1931 (Asocstos Industry Regulations. 1931) and the piis.-ii.uion* mien to prc'ent dn-u dissemination in the works had become ctfeetke by .'the end of ihe following ;car. All the subjects in whom the two diseases were found together had been employej lor at least nine years under the old conditions, and although II of the 15 men and women died within 0 years of their tirst exposure, the association of the two conditions has not yet been found in any person laken into employment doling the last 31 years tl'O.t y'i. U is. therefore, possible that the reason moie cases were not found in the second half of the period is that reduced exposure to dust has already I'egun to lessen the incidence and severity of a? bestosi; Method of (estimation of Risk Although the necropsy data shown in Tables I and 2 suggest (I) that some groups of asbestos workers have sulVered an increased risk of lung cancer, and (3) that the risk may nowhave decreased, it is not possible to be certain of either of these propositions without a more detailed knowledge of the whole mortality experience of the workers. The lir>t proposition has. therefore, been tested by comparing the mortality experienced by that section of ihe male employees ot the works referred to above, who had worked for at least 20 years in " scheduled areas '**. with the mortality recorded lor all men in f.ngland anti Wales; and the second proposition by computing the incidence of lung cancer among men employed for different periods uniler the pre-1 32 conditions. The investigation was limited to the small gioup of men who had been employed for at least 20 ye:ir-. since the labour involved in searching out the individual records of * It. UfTT whedu'rd iic.4*" ** hiig.iit! *' l \'l Acre "Jit <Jll Vt! niulyt .** lv| hem* Jim MV wit^re Inlvs-'IS ;i | J3B 0007318 | GG 1532? LUNG CANCER IN ASBESTOS WORKERS 83 men employed for shorter periods would be dis proportionately great and. so far as was known from Table 2. would be comparatively unrewarding. The date of birth, date of completing 20 years' work in the " scheduled areas ", and. where applic able. date of ceasing employment and date and cause of dentil weie obtained, for each man. from the records of the linn's Personnel Officer. Full details were, in most instances, already available for the men w ho had ceased employment as well as for the greater number who continued to be employed, since some of those who had left were registered as having asbestosis and the attention of the firm had been drawn to the death of others, in view of the possibility of the cause of death being industrial in origin. All the remaining men were successfully traced and the relevant details obtained. This was not diHicult since, by limiting the study to men who had been employed in one place for 20 years, lew were found to have changed their job or to have moved out of the region. From the data the numbers of men alive in each live-year age group were counted separately for each of the years from 1922 (the first in which a man was recorded as having had 20 years' service) to 1953. A man who havlcompleted the 20 years before the begin ning of a year and who was alive at the end of it was counted, for that year, as one unit; a man who completed the period before the beginning of a year but w bo died during it. and a man who completed the period during a year and who survived to the end of it. were each counted, for that year, as half a unit; the one nmii who died the same year as he completed his 20 ` car period was counted as a quarter of a unit. the causes of death were recorded as they were given mi the death certificate or,' when available, as the-, were unally determined by necropsy. The causes were classified in five categories fsee Tabic 4). and the numbers in each category were then compared with those which might have been expected to occur by multiplying ihe numbers of men alive in each livevc.ir age gr -up by '.lie corresponding mortality mies toi men m I ngland and' Wales o,er the .same period. Because o' the small numbers, however, the popula tions were not considered separately foi each year, bin were added together to form live groups living in die period* 1922 33. 1934-38. 1939-43, 1944-48. and i94u sy_ and tiie mortality rates used lor each gioup were those for the years 1931. 1936, 1941. Ivan, ui\| |y>5l. The rates for 1931 were used lor the penoJ 1922-33, rather than those lor the mid-years, since disproportionately few men were under oh-erv.itiun during the early part of the period. As an example ol the method, the mortality rate for all neoplasms other than lung cancer among men in hnglund and Wales aged 55 to 59 in 1951 was 2-778 per 1,000. The numbers of years lived in this age group in the five years 1949-53 were respectively 15 years. 15 years. 17i years, 19 years, and 19 years. The number of deaths expected in the period was. therefore, estimated to be (15 -- 15 - 172 -f- 19 -- 19) < 2-778 1.000 - 0-238. The total number of deaths expected from each category of diseases was obtained by adding the numbers thus calculated for each age group for each of the five periods. The great majority of the men lived and, when they died, died in the town in which the works was situated, so that it would have been preferable to have based the calculation of the expected deaths on the death rates observed in that town rather than on the rates for all Kngland and Wales. These, however, were not known in sufficient detail. Little error in the expected number of deaths from lung cancer is likely to have been introduced on this account since, according to Stocks (19521. the age-adjusted death rate for lung cancer among men in the town con cerned was v6",, of the rate lor fcngland and Wales. Stocks's figure was calculated only for the period 1946-49. but the proportion is unlikely to have varied greatly over the longer period of the investi gation. The expected number of deaths from all causes is. however, likely to he somewhat under estimated since the age-adiusted death rate from all causes for ihe town is about 25",, higher than the Fngland and Wales rate (/>. the excess was 22", m 1950. 28*',. at 1951. and 22",, in 1952). Results Tlte number of men studied was 113: the numbers of man-years lived in each of the five peuods in each age group arc shown in Table 3. The total number T.vnih 3 nlmbkk of mvn-viahs iivhd by sirs wim ; or moklxfahsoi work in a s< htim. t to ari.a- ll i s' Pct<hJ W22 31 ` '* w 0* |QUJ 4 I'JU 4V 1, - Ul. -u 4< Ml !.. 70- `M -1W<N 0 42 v.5 f? i: If 1 1) 0 5* 0< 1* l' 5 * 1 1i< 0 *K 11 11 u* <l W5 M * .4 ) 1 1*4 r" 1* 44 \\ < 85 '< < 4 1< :i i* * <4 \4 m5 x 5 ** * S 5' , < Ml l*v MtKl* 44 i<'2 1.5 2* 4 iif ' <<4 - VI 1* * J tM2 :< of deaths from all causes anJ the number of deaths observed in each of the five disease categories, together with the expected number of deaths, are shown in Table 4. brorn Table 4 it appears that the men who had been exposed to aibestoMlt.st suffered C-G 15328 -- --, m I_B_0007319_7 w BRITISH JOLRS.XL OF ISDUSTRIAL MEDICISF. T\bu: 4 ( .\IM-.S or- 111-A TH AMONG malf asbksior workers tOMRAHCO WIIH MOKIvUlY 1 XPERItNLE OK ALL Mfc'N IN ENGLAND \Nt> W.\U,S < ju*c or Dimiii No oi IVutti* TcM of Significance Ftpcctcd 01 Difference on 1 >et ween Nv FngJund Observed Obwnctl 4m) and die* Fxpectcd Kjio. (Vulue ct Pi 1 itjnoef* : wih fiicniHtft tf jshoMon,, without mention of uttvsiiiM* n 0 \ vlKHXWyl 0* J Oilier disrate* (irK'lud* mg fumvnar\ uihcicutLwiw und **rdMtJ*k,ulJr di^rax* : with mention uf jshottH** without mention 0/ M'xbeMiAie Nenpta*i*s other than lung vjrtcer All uher JtN<tRpvN1+ A!: causes .. 1f4t 4 4 lu 7 f. } -. 0 001 s 4* *. .Ill J 15 4 -.tinuitittl * Including i<of ttiirt lu^fkukvtn '`t'lCiudmif two cy^ t|*rmgn *?nciutv >t <wru>v>hstiu* and *c|T|ti- tticniuo in which y^bcMoM* w^x prcMffii bui vii\ mil thought m > ave -t wonfrilMic*r\ cnu** *t Jvuih. an increased mortality from lung cancer, other respiratory diseases and cardiovascular diseases, in association with asbestosis, but that their mortality from other diseases was close to that expected. Four explanations of the findings are possible : (I) that all the men vs ho had died of lung cancer were lecorded because of interest in the condition, but that some of the records of other men dying of other diseases or still alive were omitted, with consequent underestimation of the expected number of deaths ; (21 that lung cancer was incorrectly and excessively diagnosed among the asbestos workers ; (3) that lung cancer was insufficiently diagnosed among the general population of .England and Wales : or (4) that the asbestos workers studied suffered an excess mortality front lung cancer. It certainly cannot lie claimed that the records ol the Personnel Odico were necessarily complete, but they were believed to he complete and no dclictcncy or. ibis score would account i'oi the total excess of deaths unless it were so gross that more than half the defined population had been omitted. Moreover, the number of deaths due to conditions unrelated to asbcstvvsis w;is close to the estimated number and this is unlikely to have happened unless the population had been estimated approximately correctly and the deaths from all causes fully reported. Ml foe 11 deaths attributed to lung cancer were confirmed by necropsy and histological examination so that the excess number cannot be attributed to incorrect diagnosis among the group of asbestos workers, Some of the excess may well be due to an underestimation of the expected deaths since part of the increase in mortality attributed to lung cancer over the past 30 years is certainly due to improve ments in diagnosis and in therapy (Doll, 1953). bven, however, if it were postulated that the whole of the recorded increase between 1931 and 1951 was spurious and that the real mortality from the disease throughout was that ascribed to it in 1951. the expected number of deaths is increased to only l-l and the observed excess is still grossly signtneant. For the actual number of lung cancer cases to be so little in excess of the expected as to be reasonably attributable to chance, it would be necessary for the expected cases to be 6-2, that is 5-0 times the number estimated on 1951 rates. In other words, it would be necessary to postulate that in iy5l (and throughout the previous 20 yearsi there was 5.f> times as much cancer of the lung as was recognized in 1931, which would mean that the condition would have to have been present and capable of detection m over 20",. of all men at vlcatli Moreover, even if this were sit. it would still not account for the fact that all the cases of lung cancer were found in association with asbextoxis. It is, therefore, concluded that the fourth explan ation is the most reasonable one anti that the asbestos workers who had worked for 20 or more years in the " scheduled ureas " sullereri a notably higher risk from lung cancer than the rest oi the population. To test il tut* risk has altered since the 1931 regulations were introduced, it is not only necessary to make allow mce for duration of employment before the end of) l>32. but aiso to allow lor the men's ages and lor tne total durations of their employment in the " scheduled ureas since the men employed m the burlier, periods can also have been employed longer and lived to' be older. On the other hand, there is no need to consider the changing incidence of lung cuitsci m the total population of F ngland and Wales siikc tile non-industrial risk has been shown to be sm.ii! us comparison with the industrial one. The data reuuiicd'forcomp.ti mg the risks among men emploved lor uiulei Hi yeais. foi Id to 14 scat'. .md for 15 years and ovei m the pre-id''.'' conditions are shown in I able 5. The ages shown are the ages at vlcatli of the men who have died and the ace- n; mul1453 lor the men who are still alive. The cvpevted numbers of men m each pre-|vi t employment gioup found to have asbestosis or ashestosis and lung cancer are estimated by multiplying the numbers in each.age. total employment, and prc-1433 cmplovinent subgroup by the proportions of men with asbcstosis oi vv>th asbestosix ,unl lung cancer in the same age au.I total employment croup for all lengths of pre* 193 ! employment combined. For example, three out oi the rune men aged 5U to 54 years who had i_BB 0007320*7 *etSWfc i'i m_i -j-- ' \ - --- LUNG CANCER IN ASBESTOS WORKERS 85 Table 5 NUMBERS OF MEN EMPLOYED FOR DIFFERENT PERIODS BEFORE 1933 AND NUMBERS KNOWN TO HAVE ASBESTOSIS AND LUNG CANCER IN ASSOCIATION WITH ASBESTOSIS DIVIDED BY TOTAL DURATION OF EMPLOYMENT IN A SCHEDULED AREA AND BY AGE Total Length of Emplo><ncnt in * Scheduled Are* " (>oan) Age ml June 30, 1*53. or at Denth _________ _____ Length of Employment before January l 1933 0-9 Yean 10-14 Year* ' 13+ Year* , All LeI ngth! of Eraptoymem before January t, 19)3 No. of Men No, of No. of N_ No. ol No. of Men with Men wilh ,* Men with Men with' Aihea* Cancer M Aabe. Cancer S loan of Lung TM ' ton! of Lung i Mcn No. of No. of I Men with Men with Aibei- Cancer tom of Lung i No. of Men I No. Men of I wuh. No. Men of with II Albaton. | Cancer 1 of Lung ' 20*24 -- J430-- 4i 4530- 7 3 53- 3 60- ... 65- 5 2 . 70- 0 73-9 1 I 2 3 0 0 _ I 01 i1 0 -- w-w _- 33 2 1 0 0 --_ 0-- _0 AW 0 1 03 3 0 _ I 1 0-- .2 1 1; 38 2 !9 0 i7 0 I5 1 -- 1 31 !1 1 y1 t 1I --_ 11 i3 40 3 i i i _01 i !-- 23-29 4045- 3 10 50- 6 55- 6 60- 3 6750-- 01 S7O5---4 0 0 2* --I _. _. --. -- a-- 0 _ 2 WW1W -- 0 81 40 -- -- 1 0 0 ---l --W " 0-- | 0 0 0 0 _ _ _ 01 l 03 3 t00 10 --l l --10 i3 1 12 3 . i ww 1 0 0 1 -- 6 i 15 j7 I: 2i t 1 :1 ! 2 6 4 0o1 i ! ! i 0 >1 0i 30-34 33-r ,, All lengths of employment uf a "scheduled* area '* (20 >n.-) 455035- 22 T 60- i 65- 0 70-4 0 55- 0 60- 0 65-9 0 3540- 1 7 45- 19 30- ii 3560- 172 65-- 70- .5l 8705--4 * 0 -w. _ --w -w-- --a-- 05 1 0 _ ---A. -- 0 _ -- -w 0 2t -- .2 _0 -- -- 0-- -- I _ -- -- 0 0 -- u-- _ -- -- I N1 _ _M J 4 4 l __ 1 | 0 PW --1 -- l A, 8 ; !1 ii 2 1 3i ! 3 2 . i i 0 0 0 1 5 5 7 0 0. . *1 -- -- -- -- ' 0L 03 * --1 -- -- _l ; -- 3 3 1 1` _T 0 1 _ \-- ;i -- ;2 ,i 9 5 03 : I! 1 0 o 21 0 !-- 1 _1 _ -A. _ 11 0 0 Ww | W*. -- -- 21 0 -- ,, A. 1 3 3 5 1 2 .w . 2 ! 1 | _ 21 7i 0i 8 22 ' . 24 1 ,' 216* : ,' 7 3 . 3 10 u 8 2 ] 2 4 1 1 2 0 01 i2 --1 2 .i o 1-- AH ages 61 13 1 26 14 3 26 16 7 113 4) 11 been employed for 20 to 24 years in the areas in which they might be exposed to asbestos dust were found to have asbestosis and lung cancer. Since three men had worked for under 10 years in the pre1933 conditions, three had worked for 10 to 14 years, and three had worked for 15 or more years, the expected number of cases in each of the pre-1933 employment groups would have been the same, i.e., 3 x 3.9, or 1. In fact, the numbers of cases found were 0, 1. and 2. The total numbers expected in each pre-1933 employment group are obtained by adding the numbers calculated for each of the age and total employment groups within it. The results are as follows: The differences between the numbers of men observed and the numbers expected in each employ ment group, had the incidence of the conditions remained steady throughout, are statistically signi ficant (total asbestosis. (} = 7-52, n -- 2, P = 0*025; asbestosis and lung cancer, x* = 8*74, n = 2. P = 0*01*). They are highly so if the trend, that is. Length of Employment before January 1, 1933 Under ( 10-14 : 15 Yean 10 V can ' Yean end Over Total numberof men \ observed . with asbestosis Jr.xpertctl 13 my 14 103 16 7<M Number ot men with 1 observed \ 3 7 abeiosift ^nd lung / r xpentJ ss .1 *;; cancer " The expected number* of lung caneer are small and the probability that the differences could ante bv chance hat consequently been somewhat, but not usly, underestimated. If all men wuh more than |0 veers pre-|9JJ employment are grouped together and Yates' correction nude for small numbers, x* -- 582, n -- i, p -- 0 02, l_BB 0007321 j -f : i 86 BRITISH JOURNAL OF INDUSTRIAL MEDICINE the biologically important reduction in the propor tion between observed and expected numbers as the length of pre-1933 employment is reduced, is also taken into consideration. It is dear, therefore, that the incidences both of asbestosis and of lung cancer associated with asbestosis have become progressively less as the number of years during which men were exposed to the pre-1933 conditions has decreased. The extent of the risk of lung cancer over the whole period among the men studied appears to have been of the order of 10 times that experienced by other men. This agrees well with the data reported by Merewether (1949). but it is somewhat greater than that suggested by Gloyne's data (1951). The great reduction in the amount of dust produced in asbestos works during the period has been accom panied by a reduction in the incidence of lung cancer among the workmen so that the risk before 1933 is likely to have been considerably greater--perhaps 20 times the general risk. Whether the specific industrial risk of lung cancer has yet been completely eliminated cannot be determined with certainty ; the number of men at risk, who have been exposed to the new conditions only and who have been employed for % sufficient length of time, is at present too small for confidence to be placed in their experience. It is clear, however, that the risk has for some time been greatly reduced. The extent of the reduction is particularly striking when it is recalled that between 1933 and 1953 the incidence of the disease among men in the country at large has increased sixfold. Summary *. The cause of death, as determined at necropsy,, is. feported for 105 persons who had been employed at one asbestos works. Lung cancer was found in 18 instances, 15 times in association with asbestosis. All the subjects in whom both conditions were found had started employment in the industry before-1923 . and had worked in the industry at least nine years before the regulations for the control of dust had become effective. One hundred and thirteen men who had worked for at least 20 years in places where they were liable to be exposed to asbestos dust were followed up and the mortality among them compared with that which would have been expected on the basis of the mortality experience of the whole male population. Thirty-nine deaths occurred in the group whereas 15-4 were expected. The excess was entirely due to excess deaths from lung cancer (U against 0*8 expected) and from other respiratory and cardiovascular diseases (22 against 7-6 expected). All the cases of lung cancer were confirmed histo logically and all were associated with the presence of asbestosis. From the data it can be concluded that lung cancer was a specific industrial hazard of certain asbestos workers and that the average risk among men employed for 20 or more years has been of the order of 10 times that experienced by the general popula tion. The risk has become progressively less as the duration of employment under the old dusty con ditions has decreased. I would like to offer my thanks to the management of the firm concerned for permission to carry out this work and to the Medical Officer and members of the staff of the works where the men were employed, who earned out the greater part of the work on which this report is based. References Asbcftos Industry Keguiahofls *1931). Statutory Rule* and Order*, 1911, No 1140, H.M.S.0. London. Roemkc. F. < |9*1L Msrhr., 7. 77, Canter, P. (1952). Arch. inJustf. Hyg., 5, 262 (contribution to* discussiont. CourtQl ol` itfe International Orfinirjttions of Medical Sciehces * (19331. Actu 4jm. uft. I anrr , 9, 44J, l>oll. R, (1953). Brit. med. J.. 2, 521. Cioyne, S. R. (19311. Lumet. I* Aid. * Mueper. W, C\ (IV*2). f*r<'feeding* uj ike Seventh Sohimrc uum. To be published' l,inch, K. M.. and Smith. W. A, f 1935). Amt*. J. ( oncer. 24, 36, Merewether. h. R. A- [ 194*41. Annual Her*wi of the Chief Inspector* * of Factories for the Yeur H-M.S-O., London, Nofdmanrf, M.. and Some, A. UV4I). Z. KrebxtoeteH , SI, IM. Smith, W F. HvS?)' Art k. mdustr. Hyg.t 5, 209. Stock), P. Brtt. J Concer, 6, 99- Vorwald. A. J.. and Karr, J. W (19361. Amtr. J.Patk.. 14, 49. Warren, S. OV4*>. Oecup. Med., 5, 249. NOTE: kC : \\T) -i'S ..., * w l BB 0007322 |