Documents Finkelstein, Murray M. 8 results

Background: The health effects of asbestos are intimately related to the fate of inhaled fibers in the lungs. The kinetics of asbestos fibers have been studied primarily in rodents. The objective of this study was to explore the application of these kinetic models to human autopsy data. Methods: We analyzed the asbestos fiber content of the lungs of 72 Quebec chrysotile miners and millers and 49 control subjects using analytical transmission electron microscopy. Statistical methods included standard multivariate linear regression and locally weighted regression methods. Results: The lung burdens of asbestos bodies and chrysotile and tremolite fibers were correlated, as were the concentrations of short, medium, and long fibers of each asbestos variety. There were significant associations between the duration of occupational exposure and the burdens of chrysotile and tremolite. The concentration of chrysotile decreased with the time since last exposure but the concentration of tremolite did not. The clearance rate varied inversely with the length of chrysotile fibers. For fibers greater than 10 in length the clearance half-time was estimated to be 8 years. Conclusions: The patterns in our data are compatible with both of the hypotheses suggested from rodent experiments; the existence of a long-term sequestration compartment and overload of clearance mechanisms in this compartment.

Background To investigate exposure-response relationships for silica, silicosis, and lung cancer. Methods Quantitative review of the literature identified in a computerized literature search. Results The risk of silicosis (ILO category 1/1 or more) following a lifetime of exposure at the current OSHA standard of 0.1 mg/m3 is likely to be at least 5-10% and lung cancer risk is likely to be increased by 30% or more. The exposure-response relation for silicosis is nonlinear and reduction of dust exposures would have a greater than linear benefit in terms of risk reduction. Available data suggests that 30 years exposure at 0.1 mg/m3 might lead to a lifetime silicosis risk of about 25%, whereas reduction of the exposure to 0.05 mg/m3 might reduce the risk to under 5%. Conclusions The lifetime risk of silicosis and lung cancer at an exposure level of 0.1 mg/m3 is high. Lowering exposures to the NIOSH recommended limit if 0.05 mg/m3 may have substantial benefit.

"Background Benzene is a human leukemogen. Risk assessment, and the setting of occupational and environmental standards, has assumed that risk is constant in time after a unit of exposure. Leukemia risk is known to vary with time after exposure to ionizing radiation. Methods A matched case-control study of leukemia risk in relation to the temporal pattern of benzene exposures was performed using data from the National Institute of Occupational Safety and Health. Results Leukemia risk following exposure to benzene varied with time in a manner similar to that following exposure to ionizing radiation. More recent exposures were more strongly associated with risk than were more distant ones. There was no significant relation between leukemia death and benzene exposures incurred more than 20 years previously. Conclusions Recent analyses of specific occupational and environmental carcinogens, including benzene and radon, have indicated that cancer risk tends to decline as the time from exposure increases. This suggests that standards for the control of occupational or public risk must be selected to control exposures over a narrower time frame than the usual lifetime one. In the case of benzene, it would appear that risk is attributable primarily to exposures incurred during the previous 10 to 20 years, with exposures in the most recent 10 years being the most potent. To limit risk, exposures must be controlled during that interval. It is important that epidemiologists explore the temporal pattern of risk in their studies to facilitate the risk assessment of other carcinogens."

A prospective study of lung cancer in a cohort of asbestos cement workers was performed 20 and 25 years after their initial exposure to asbestos (1332214). Radiography was carried out on 151 workers who were employed for 9 years or more at a factory that made asbestos cement pipe and board using chrysotile (12001295) and crocidolite (12001284) asbestos in Ontario, Canada. Workers were exposed for at least 12 months to a range of exposures to asbestos from less than 50 fiber year/milliliter (f-y/ml) to greater than 200f-y/ml. At 20 years after initial exposure to asbestos, radiograms for 143 workers were examined; 20 of them had asbestosis. The lung cancer standardized mortality ratio (SMR) for those without asbestosis at 20 years latency was 5.53. At 25 years after initial exposure, radiograms for 128 subjects were examined; 14 of them had asbestosis. The lung cancer SMR for those without asbestosis at 25 years latency was 5.81. This study was consistent with other epidemiological studies of asbestos exposed populations in a variety of exposure situations. The authors conclude that the risk of cancer is increased in those who have radiographically identifiable asbestosis, but it may also be increased in its absence.

"Background: It has been a matter of controversy whether there is an increased risk of lung cancer among asbestos-exposed workers without radiographic asbestosis. A previous study of lung cancer risk among asbestos-cement workers has been updated with an additional 12 years of follow-up.
Methods: Subjects had received radiographic examination at 20 and 25 years from first exposure to asbestos. Radiographs were interpreted by a single National Institute of Safety and Health (NIOSH)-certified B-reader using the 1971 International Labor Office (ILO) Classification of the pneumoconioses as reference standard. Asbestosis was defined as an ILO coding of 1/0 or higher. Standardized Mortality Ratios (SMRs) were calculated using the general population of Ontario as reference.
Results: Among asbestos-cement workers without radiographic asbestosis at 20 years latency the lung cancer SMR was 3.84 (2.24–6.14). Among workers without asbestosis when examined at 25 years latency the SMR was 3.69 (1.59–7.26).
Conclusions: Workers from an Ontario asbestos-cement factory who did not have radiographic asbestosis at 20 or 25 years from first exposure to asbestos continued to have an increased risk of death from lung cancer during an additional 12 years of follow-up. "