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Projects < back Asbestos Human Health Risk Assessment, Big Tex Grain Site
U.S. Environmental Protection Agency, Region 6, under contract to Weston Solutions, Inc. OVERVIEW
DESCRIPTION As a subcontractor on the EPA START Region 6 contract, Avatar Environmental took the lead in performing a human health risk assessment (HHRA) for potential exposure to amphibole asbestos at the Big Tex Grain Site in San Antonio, TX. The Site has historically been associated with industrial activity, including the operation of a vermiculite exfoliation plant, grain production, and sawdust warehousing. The Big Tex Grain Company operated the vermiculite exfoliation plant from 1961 to 1989. W.R. Grace assumed operation of the plant in 1978. During the W.R. Grace operational period of 1978 to 1989, the plant processed raw vermiculite ore, contaminated with amphibole asbestos, mined from Libby, Montana. At least 103,000 tons of contaminated raw vermiculite ore was shipped to the Big Tex Grain Site. Sampling had indicated that asbestos contamination existed in the soil, air, and dust (inside buildings) at the Site. Surface and subsurface soil samples were collected along with Microvac dust samples from within on-site buildings. Air samples using activity based sampling (ABS) techniques and stationary air samples were also collected. The goal of the HHRA was to determine whether a potential health risk existed to local residents and to make decisions on site cleanup options. Risks were estimated using the ABS data from on-site activities such as raking. Other results were also evaluated including stationary air samples as well as soil and dust (inside on-site buildings) sample results. Meteorological data were also collected and considered in the assessment. This asbestos HHRA was one of the first for Libby asbestos sites performed by any contractor under EPA's Asbestos Framework guidance, which was developed, in part, due to EPA concerns that the previous 1% in soil definition of asbestos sites might not be health protective, especially when sites contained amphibole asbestos. Avatar developed the risk assessment in consultation with EPA Region 6 risk assessors as well as EPA risk assessors from other regions who are part of the EPA Technical Review Workgroup (TRW) prior to the actual release of the Framework document. It includes all aspects of the Asbestos Framework including a new toxicological approach that incorporates age of onset and duration of exposure as well as a detailed Uncertainty Analysis considered critical by EPA on this type of project.
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