Activity-Based Sampling Activities at the Libby Asbestos Superfund Site, Libby, Montana

摘要

Libby is a community in northwestern Montana located 7 miles southwest of a vermiculite mine that operated from the 1920s until 1990. The U.S. Environmental Protection Agency (EPA) determined that the vermiculite and vermiculite ore from the mine contains amphibole-type asbestos, referred to as Libby amphibole (LA). Although the mine has ceased operations, historic or continuing releases of LA from mine-related materials could be serving as a source of ongoing exposure and risk to current and future residents and workers in the area. Inhalation exposures may pose a risk of cancer and/or non-cancer effects. The Libby Asbestos Superfund Site (Site) was added to the EPA National Priorities List in October 2002. Previous EPA investigations conducted at the Site have demonstrated that LA is present in various environmental source media (e.g., dust, vermiculite insulation, soil, tree bark, forest duff) at locations in and around the Site. However, quantification of LA in source media does not provide information on whether or not disturbances of these media, such as under typical residential or occupational scenarios (e.g., raking, mowing, digging, logging), would result in unacceptable inhalation exposures. EPA has performed several investigations at the Site to evaluate potential exposures to LA released from source media by measuring the concentration of LA in breathing zone air during various disturbance activities, referred to as "activity-based sampling" (ABS). This paper discusses the field protocol used at the Site for conducting an ABS event, including field planning, script development for each ABS activity type, community involvement, Occupational Safety and Health Administration requirements, laboratory analysis methods, and quality assurance/quality control measures. The presentation will provide examples of ABS that have been performed at the Site and include a discussion of lessons learned from previous sampling efforts.