An Evaluation of Potential Asbestos Pathways from Vermiculite Attic Insulation and/or other Asbestos Containing Materials in Western Montana Homes

It is estimated that Zonolite brand attic insulation which was produced from a vermiculite mine near Libby, Montana, was installed in about 35 million homes in the United States, including thousands of homes in Montana. Unfortunately, the vermiculite was contaminated with amphibole asbestos. In addition, it is estimated that commercial products containing asbestos materials are present in millions of homes in the United States. Of the Montana residents that qualify for weatherization assistance, at least 200 applicants are denied annually due to the presence of asbestos in the home.;The Montana Department of Health and Human Services, Intergovernmental Human Services Bureau was awarded funding to explore the impact of weatherizing homes containing asbestos and to develop asbestos-safe weatherization protocols. The objectives of this initial Phase I research were to (1) confirm the presence of asbestos in selected homes via bulk sampling and (2) evaluate potential pathways into living spaces from bulk asbestos sources.;Bulk samples of vermiculite attic insulation and other ACM were collected in 46 western Montana homes and analyzed by an independent laboratory. If asbestos was confirmed in any of the bulk samples, baseline sampling was then performed in the home to determine if the presence of bulk asbestos sources resulted in asbestos contamination within living spaces. Baseline sampling included high volume air sampling, surface wipe sampling, and surface micro-vacuum sampling.;The majority (87%) of homes selected for this project contained vermiculite attic insulation (VAI) and all homes containing VAI revealed the presence of amphibole asbestos in bulk samples. In addition, asbestos (primarily chrysotile) was confirmed in bulk samples ACM collected from 18 homes. High volume air sampling revealed a mean living space air concentration of 0.016 f/cc (SD = 0.014) when analyzed by phase contrast microscopy (PCM). Nine percent of the air samples revealed detectable asbestos concentrations when analyzed by transmission electron microscopy (TEM). Fifty-five percent of the surface wipe samples and 17 percent of the micro-vacuum samples revealed detectable asbestos concentrations via TEM analyses.;The results demonstrate that VAI frequently contains amphibole asbestos. In addition, the results suggest that the presence of VAI and/or other ACM may contribute to living space contamination.