Document GzZjGV8Z8eoV11ORJG9GQ0p1N

110 ASBESTOS EXPOSURE-SELIKOFF ET AL Table 5.--Observed and Expected Bronchogenic Carcinoma Deaths by Smoking Habits* for 370 Asbestos Workers Smoking Habits Never smoked regularly History of pipe, cigar smoking only History of regular cigarette smokingt Observed Deaths 0 0 24 Expected Deaths 0.05 0.13 2.98 Total 24 3.16 "Based upon data in Table 2 and Table 4. tlncludes cigarette smokers who also smoked pipe or cigar. Table 6.--Expected and Observed Deaths Among 632 Asbes tos Workers Exposed to Asbesto Dust 20 years or Longer Total deaths: all causes Expected Observed Total cancer all sites Expected Observed Cancer of lung, trachea, pleura Expected Observed Cancer of stomach, colon, rectum Expected Observed Cancer all other sites combined Expected Observed Asbestosis Expected Observed AM other causes Expected Observed 1943-1962 203.5 255 Total 1963.1967 1943-1967 47.5 94 251 349 36.5 95 8.6 49 45.1 144 6.6 45 2.3 27 8.9 72 9.4 29 1.8 11.2 8 37 20.5 22 4.5 14 25 35 00 0 12 15 27 167 38.9 205.9 148 30 178 into consideration. The results are summarized in ~ ble 5 which shows the expected and observed jiber 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 one of the excess bronchogenic carcinoma deaths might be attributed to the fact that there appear to have 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 exposed to asbestos dust somewhat longer than the subjects of our previous study (the present 370 subjects are survivors as of Jan 1, 1963, of subjects in the previous study). Of the subjects who never smoked regularly and those who smoked only pipes or cigars, none died bronchogenic carcinoma whereas 0.18 of these .n were expected to die of lung cancer. This sug gests that exposure to asbestos dust does not in crease the risk of bronchogenic carcinoma among 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 greatly increase the risk of bronchogenic carcinoma among men who never smoked cigarettes regularly. Twenty-four of the men with a history of regular cigarette smoking died of bronchogenic carcinoma whereas only 2.98 were expected to diffTJf 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, we 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 smoked regularly and had never been occupationally exposed to asbestos dust. Since 24 of them actually died 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 plus 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 and expected number of deaths for each of two periods (the first, 1943 to 1962, 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 and 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.''10 Nor -have 108 P JAMA. April 8. 1958 Vol 204. No 2 FOS 000934-1 I