Document 2RkQX1Ljb8GznE5Nneqj8ye5b

Figure 5 Dust Control Study: Dr. John Knox Distribution of Deaths with Exposure Before 1933 Standardized for Time since Completing 20 years' Employment and Age Exposure Before 1933 (yrs) Distribution of Lung Cancer Deaths Observed Expected Distribution of Other Deaths With Asbestosis Observed Expected Distribution of Other Deaths Without Asbestosis Observed Expected Over 10 (Group 1) Up to 10 (Group 2) None (Group 3} 15 9.8 17 11.38 16 16.91 6 8.41 5 8.07 12 12.98 2 4.78 0 2.55 13 11.12 All Groups Test of Significance of Trend 23 23.00 x*= 6.70 n =1 P =0.01 22 22.00 x* = 9.63 n =1 P = 0.002 41 41.01 X* = 0.52 n =1 p = 0.47 among asbestos workers who also smoked cigarettes. Those asbestos workers who did not smoke cigarettes had no greater rate of bronchogenic cancer than the normal, non-smoking population. Based on these hard facts about the co-carcinogenic effect of smoking and asbestos dust in halation, Johns-Manville and other asbestos companies strive to discourage smoking among em ployees who work with asbestos. (Figure 6). LOCKED-IN AND NON-LOCKED-IN While it is evident that excessive asbestos dust inhalation can be harmful, this risk is confined almost exclusively to the occupational setting. Asbestos products in general use may or may not pose a dust problem, depending on their composition and handling. Basically, asbestos products fall into two groups - the "locked-in" products and the "nonlocked-in" products. In the non-locked-in products, one must be concerned with the generation of dust. However, in those products in which the asbestos is locked-in by chemical, physical or thermal means, there is little cause for concern since the normal use of these products will not release significant amounts of asbestos fiber into the air. While we know today that asbestos can cause health problems if proper steps are not taken _10_ PRODUCED JM-83