New Methods for Assessing Exposure to Asbestos and Other Fibrous Minerals to Inform Risk Assessment

摘要

Exposure to asbestos and related mineral fibers released from soil is a growing public health hazard. Known public health risks exist in Turkey, Korea, Israel, Italy, and the United States. Soil contamination may be naturally occurring, asbestos containing material production, or demolition of buildings containing asbestos. This presentation compares three new methods to evaluate human health risks due to exposure to asbestos-contaminated soil: activity-based sampling (ABS), the Releasable Asbestos Field Sampler (RAFS), and Fluidized Bed Asbestos Segregator (FBAS). ABS measures exposure to asbestos in the breathing zone of a person performing a specified task, while the RAFS measures the release of asbestos from soil and is coupled with a breathing zone model to predict exposure. The FBAS measures the presence or absence of asbestos in soils by separating asbestos structures and other small particles from other soil. Collocated comparison of the three methods was conducted at 15 asbestos-contaminated sites across the U.S. to determine the representativeness, sensitivity, and precision of the methods. Asbestos levels measured by all three methods are highly correlated. Air concentrations generated by the RAFS over-predict exposure compared to ABS (slope = 12.5, R2 = 0.68) because the RAFS measures asbestos emissions at the soil surface and is not affected by factors that disperse fibers during transport to the breathing zone. RAFS measured emissions are correlated with the FBAS determined soil loading (slope = 1.48, R2 = 0.75). All three methods detect asbestos at soil loadings less than 0.1%, the limit for the standard polarized light microscopy method. The precision of the methods ranges from ＜ 5% to more than 80% because of the asbestos heterogeneity in the soil. These new methods are useful for assessing asbestos exposure. Each is complimentary to the other. Therefore, a new paradigm for evaluating exposure concentrations to inform cancer risk assessment is being developed.