EPA's answers to questions about air quality in Libby
Guest Commentary:
EPA announced some long-awaited health studies in December (Toxicological Review of Libby Amphibole Asbestos and Draft Site-wide Human Health Risk Assessment). These documents can be accessed on EPA Region 8’s web site at www2.epa.gov/region8/libby-asbestos. Copies are also available at the Lincoln County libraries in Libby and Troy and DVDs are available at EPA’s Libby Information Center. EPA made a commitment at the public meetings to answer questions related to our studies and we’d like to take this opportunity to address some questions we’ve received about air quality improvements in Libby since the mining and processing operations ended.
We have said that the outdoor (ambient) air concentrations of amphibole asbestos have decreased about 100,000 times. That statement is based on measurements of asbestos. The Clean Air Act does not require communities to monitor asbestos in the air, however, as part of the risk assessment, it was necessary for EPA to do our own sampling of outdoor air. At the request of local officials in Libby and Troy, we also sampled outdoor air in Helena and Eureka.
Information for historical outdoor air asbestos concentration was based on data collected by W. R Grace in 1975, which indicated that samples collected in downtown Libby ranged from about 100,000 to 1,500,000 asbestos fibers per cubic meter (f/m3). (A cubic meter is about the size of a washing machine.) These data were collected at a time when, each day, the mine emitted thousands of pounds of particulate matter including amphibole asbestos. The current outdoor air data EPA reported is based on data that we have collected. Over the past 10 years, EPA has collected more than 1,500 outdoor air samples. Today, in downtown Libby, we typically find about one fiber of Amphibole asbestos in a cubic meter of outdoor air. However, these are not the only data used in the risk assessment – and not the only data we are using in decision-making for the site.
EPA and other research groups have learned that when amphibole-contaminated materials such as soil are disturbed, the amphibole fibers are released into the air, are suspended, and become a potential source for inhalation exposure. As part of the risk assessment, EPA collected air samples (activity-based samples) to understand inhalation exposures for a wide variety of activities conducted in and around Libby and Troy. Over the past several years we have collected more than 3,000 activity-based samples. These samples have allowed us to understand the potential total exposure associated with the disturbance of soil and other materials as one lives, works and recreates in the Libby area. That total exposure, which also includes exposure for the inhalation of outdoor air, is based upon the summary of exposures from many activities that people who live here may experience throughout their lifetime.
The risk assessment demonstrates that soils, homes, businesses and other areas contaminated with higher levels of asbestos can contribute to higher exposures and higher risks. The risk assessment also shows that when a cleanup has been completed on a property, the exposures are reduced to a level consistent with EPA targets for protectiveness. This is why it is so important that all property owners in Libby and Troy participate in EPA’s cleanup.
As stated above, we will continue to answer questions, to the best of our ability, about the toxicity assessment, risk assessment and other site-related matters. EPA is accepting comment on the draft risk assessment and will do so until completion of a proposed plan public comment period which is expected this spring. EPA wants to ensure that the risk assessment represents the best science and the best outcome for the people of Libby and Troy.
— Dr. Deborah McKean is a Senior Toxicologist with the United States Environmental Protection Agency.