Recently there have been calls to reevaluate standards governing asbestos in light of suggestions that chrysotile asbestos is relatively safe. Arguments for the relative safety of chrysotile note that while workers in a South Carolina asbestos textile plant using chrysotile experienced substantial excesses of lung cancer, Canadian chrysotile miners have not. One possible explanation for these divergent findings is that the carcinogenic effect of chrysotile exposure is determined, in part, by fiber size and morphology. The North Carolina Asbestos Textile Study addresses this hypothesis with data on a cohort of workers at four previously unstudied asbestos textile plants. In a project supported by NIOSH (R01OH007803), we have reconstructed historical exposures in these plants, applied novel techniques to characterize the morphology and size distribution of fibers and carried out epidemiological analyses revealing a significant excess of lung cancer relative to the US population (SMR 1.95 95% CI 1.73-2.20). This application is a competing continuation of that project. In contrast to the original study's emphasis on assessing exposures among North Carolina asbestos textile workers, this continuation focuses primarily on quantitative risk assessments using data from the North Carolina cohort and from a cohort of South Carolina asbestos textile workers. We propose a series of analyses that go well beyond those planned for the original project. These analyses are motivated by prior findings that strongly suggest a peak, then decline, in lung cancer risk following asbestos exposure. The analyses we propose here employ advanced modeling approaches to produce estimates of the change in the rate of lung cancer per unit of exposure that vary with time since exposure. If an exposure effect varies over time, then such methods can inform risk assessments and obtain results that are consistent between study populations. Specifically, we propose to: 1) apply flexible statistical models to describe latency effects including exposure time-windows, bilinear, sigmoid, and cubic B-spline latency models; 2) apply biomathematical cancer models as a complement to the empirical models of exposure-time-response associations; and, 3) conduct pooled analyses of exposure and epidemiologic data from North Carolina and South Carolina asbestos textile worker cohorts. The work outlined here will substantially improve the quantitative risk estimates derived from historical cohort studies of US chrysotile asbestos textile workers. The proposed work will substantially improve quantitative risk estimates derived from historical cohort studies of US chrysotile asbestos textile workers and will provide much needed information concerning fiber characteristics most strongly predictive of excess lung cancer risk. The results may help to explain some of the heterogeneity that has been observed among cohorts exposed to chrysotile. Pooled analyses of exposure and epidemiologic data from North Carolina and South Carolina asbestos textile cohorts will strengthen the precision of exposure assessment and risk estimates and improve the ability to characterize exposure-time- response associations. ? ? ?

Agency
National Institute of Health (NIH)
Institute
National Institute for Occupational Safety and Health (NIOSH)
Type
Research Project (R01)
Project #
2R01OH007803-05A1
Application #
7524199
Study Section
Safety and Occupational Health Study Section (SOH)
Program Officer
Karr, Joan
Project Start
2008-08-01
Project End
2010-01-31
Budget Start
2008-08-01
Budget End
2009-07-31
Support Year
5
Fiscal Year
2008
Total Cost
$465,548
Indirect Cost
Name
University of Nevada Reno
Department
Public Health & Prev Medicine
Type
Other Domestic Higher Education
DUNS #
146515460
City
Reno
State
NV
Country
United States
Zip Code
89557
Loomis, Dana; Dement, John M; Elliott, Leslie et al. (2012) Increased lung cancer mortality among chrysotile asbestos textile workers is more strongly associated with exposure to long thin fibres. Occup Environ Med 69:564-8
Elliott, Leslie; Loomis, Dana; Dement, John et al. (2012) Lung cancer mortality in North Carolina and South Carolina chrysotile asbestos textile workers. Occup Environ Med 69:385-90
Dement, John M; Loomis, Dana; Richardson, David et al. (2011) Estimates of historical exposures by phase contrast and transmission electron microscopy for pooled exposure--response analyses of North Carolina and South Carolina, USA asbestos textile cohorts. Occup Environ Med 68:593-8
Loomis, Dana; Dement, John; Richardson, David et al. (2010) Asbestos fibre dimensions and lung cancer mortality among workers exposed to chrysotile. Occup Environ Med 67:580-4
Dement, J M; Myers, D; Loomis, D et al. (2009) Estimates of historical exposures by phase contrast and transmission electron microscopy in North Carolina USA asbestos textile plants. Occup Environ Med 66:574-83
Loomis, D; Dement, J M; Wolf, S H et al. (2009) Lung cancer mortality and fibre exposures among North Carolina asbestos textile workers. Occup Environ Med 66:535-42
Dement, J M; Kuempel, E D; Zumwalde, R D et al. (2008) Development of a fibre size-specific job-exposure matrix for airborne asbestos fibres. Occup Environ Med 65:605-12