Fiber size-specific exposure estimates and updated mortality analysis of chrysotile asbestos textile workers.
Kuempel-ED; Stayner-LT; Dement-JD; Gilbert-SJ; Hein-MJ
Toxicologist 2006 Mar; 90(1):71
Previous epidemiological studies of asbestos exposure and lung disease have estimated airborne exposures using the number of fibers >5 um/cm3 (length/width ratio of at least 3). However, evidence from toxicological studies suggests that the longer fibers may be more biologically significant than the shorter fibers. To formally assess this question, NIOSH has re-analyzed the original asbestos samples for a South Carolina textile worker cohort (Dement et al. 1983; Am J Ind Med 4:399- 433) using transmission electron microscopy to obtain the bivariate (diameter and length) fiber size distributions. These data were used to develop a new bivariate jobexposure matrix for the textile workers, in which the previous phase contrast microscopy- based exposure estimates, by department and job, were adjusted to account for fiber dimension. These fiber size-specific exposure estimates include diameters from <0.3 um to >3 um and lengths from <1.5 um to >40 um. The differences in these fiber dimensions across departments were as much as five-fold. In addition, NIOSH has updated the mortality follow-up for this cohort, which includes an additional 701 deaths and a total of 118,474 person-years at risk. This analysis confirmed the findings of a previous analysis (Stayner et al. 1997; Occup Environ Med 54(9):646 52), which showed statistically significant exposure-response relationships between cumulative exposure to chrysotile fibers >5 um/cm3 and lung cancer or asbestosis. Analyses are underway to determine the influence of fiber dimension on lung disease risk. These findings will be useful in quantitative risk assessment, as well as in determining the concordance of epidemiological and toxicological studies and in evaluating the scientific evidence for a fiber size-specific risk assessment paradigm.
Mortality-rates; Mortality-data; Textiles-industry; Textile-workers; Asbestosis; Epidemiology; Lung-disease; Airborne-particles; Airborne-fibers; Statistical-analysis; Exposure-levels; Exposure-assessment; Quantitative-analysis
Research Tools and Approaches: Risk Assessment Methods
The Toxicologist. Society of Toxicology 45th Annual Meeting and ToxExpo, March 5-9, 2006, San Diego, California