Using alternative asbestos exposure metrics to model the risk of worker mortality from asbestosis
Methods: The main analysis was based on 880 Libby workers hired when higher quality exposure data were available. Cox models were used to assess the effects of LAA on asbestosis mortality. Sensitivity analyses included four lags for asbestosis latency and multiple exposure metrics including cumulative exposure, residence-time weighted exposure, and metrics allowing for fiber clearance. Results were compared using AIC weights which assign probabilities of each model being the best fit.
Results: Models that contained 15-year lags and allowed for simulated fiber clearance over time were the best fitting for asbestosis mortality (p<0.01). Compared to cumulative exposure, this class of models had better fit: AIC weights showed a higher probability (1.5−1.8 times) of being the best fitting model, while the residence-time weighted exposure models did not fit well. In the full cohort, where early exposure measurement was of lower quality, there was a substantial attenuation of effects (2.9- and 4.2-fold lower) from the main estimates for cumulative exposure and fiber clearance metrics.
Conclusions:The effect of exposure misclassification in the early data results in a clear bias of the effect toward the null. The adverse effects of LAA exposure on asbestosis mortality in this cohort are clear. Models that mathematically allow for fiber clearance over time provide superior fit to these asbestosis mortality data.
Disclaimer: The views expressed in this abstract are those of the authors and do not represent USEPA opinions and/or policy.
Learning Areas:Environmental health sciences
Occupational health and safety
Public health or related research
Compare the effect of using alternative exposure metrics for asbestos on the risk of asbestosis mortality. Assess the effect of exposure misclassification on the risk of asbestosis mortality.
Keyword(s): Epidemiology, Air Pollution & Respiratory Health
Qualified on the content I am responsible for because: I have a background in epidemiology and statistical methods. I am currently a fellow at the USEPA working with the group that produced the Libby Amphibole Asbestos Toxicological Review.
Any relevant financial relationships? No
I agree to comply with the American Public Health Association Conflict of Interest and Commercial Support Guidelines, and to disclose to the participants any off-label or experimental uses of a commercial product or service discussed in my presentation.