Research Radiographic Evidence of Nonoccupational Asbestos Exposure from Processing Libby Vermiculite in Minneapolis, Minnesota Bruce H. Alexander,1 Katherine K. Raleigh,1 Jean Johnson,2 Jeffrey H. Mandel,1 John L. Adgate,1,3 Gurumurthy Ramachandran,1 Rita B. Messing,2 Tannie Eshenaur,2 and Allan Williams 2 1Division of Environmental Health Sciences, School of Public Health, University of Minnesota, Minneapolis, Minnesota, USA; 2Minnesota Department of Health, St. Paul, Minnesota, USA; 3Department of Environmental and Occupational Health, Colorado School of Public Health, Aurora, Colorado, USA Background : Community exposure to asbestos from contaminated vermiculite ore from Libby, Montana, occurred in many processing sites in the United States, including a densely populated urban residential neighborhood of Minneapolis, Minnesota. o Bvitcej : We examined exposed community residents who never worked at the plant or never lived with a plant worker for radiographic evidence of lung changes consistent with asbestos exposure. Methods : We obtained posteroanterior chest radiographs to identify the prevalence of pleural abnormalities consistent with pneumoconiosis, as determined by consensus of two National Institute for Occupational Safety and Health–certified B-reader radiologists. We estimated cumula- tive asbestos exposure (fibers per cubic centimeters × months) with air dispersion model data and activity-based modeled exposure estimates for vermiculite processing waste contact. We modeled associations between pleural abnormalities and asbestos exposure using multiple logistic regression to adjust for year of birth, sex, and potential occupational asbestos exposure. r sulte : Radiographs were obtained for 461 participants. hTe prevalence of pleural abnormalities by B-reader consensus was 10.8%. A history of direct contact with the waste and ever playing in the waste piles was associated with pleural abnormalities {odds ratio [OR] 2.78 [95% confidence inter- val (CI): 1.26, 6.10] and 2.17 (95% CI: 0.99, 4.78), respectively, when adjusted for background exposure}. hTe regression coefficients for log-transformed measures ( fibers per cubic centimeters × months) of background exposure and activity-based exposure were 0.322 (95% CI: 0.078, 0.567) and 0.063 (95% CI: –0.013, 0.139), respectively, when adjusted for each other, and 0.283 (95% CI: 0.104, 0.463) for cumulative exposure from all sources. c onclusi : hTese results support the hypothesis that community exposure to asbestos-contami- nated vermiculite originating from Libby, Montana, is associated with measurable effects based on radiographic evidence. k ey w ords : amphibole, asbestos, community exposure, Libby vermiculite, lung diseases, pleural abnormalities. Environ Health Perspect 120:44–49 (2012). http://dx.doi.org/10.1289/ehp.1103529 [Online 12 October 2011] rock created a scenario for substantial non- occupational exposure to asbestos. Responding to residential concern in 2000 (Gordon 2000), the MDH and ATSDR initi- ated the Northeast Minneapolis Community Vermiculite Investigation (NMCVI). The NMCVI staff surveyed > 1,600 properties and worked with the U.S. Environmental Protection Agency (EPA) to document contamination on > 260 properties, which subsequently were cleaned by the U.S. EPA in a time-critical removal under the federal Superfund program. The MDH/ATSDR investigation assessed past and present Libby asbestos exposure pathways for workers and community members, including relative fiber levels and exposure duration (MDH 2005) in addition to estimating ambient air expo- sures during the years the plant was operating (Kelly et al. 2006; MDH 2003). Interviews were conducted with > 6,400 community members to establish baseline information. As a follow-up to the exposure characterization in this community, we evaluated the impact of nonoccupational exposure to asbestos from contaminated vermiculite on lung health as evidenced by radiographic changes in the lungs of community members. Materials and Methods Approval for the study protocol was obtained from the human subjects committees of the University of Minnesota and the MDH. All participants were guided through an informed consent process, and written consent was obtained before their participation. Study population. The focus of this study was nonoccupational exposure to asbestos from contaminated vermiculite in the popu- lation surrounding the WM/WRG site in Address correspondence to B.H. Alexander, Division of Environmental Health Sciences, University of Minnesota, School of Public Health, Room 1260, Mayo Building, 420 Delaware St. SE, Minneapolis, MN 55455 USA. Telephone: (612) 625-7924. Fax: (612) 625-4936. E-mail: balex@umn.edu We thank J. Korinek, N. Pengra, D. Kampa, and R. Hoffbeck for assistance with this research. This work was supported by Agency for Toxic Substances and Disease Registry grant 1 R01 TS000014. The authors declare they have no actual or potential competing financial interests. Received 6 February 2011; accepted 12 October 2011. ovlume 120 | number 1 | January 2012 • Environmental Health Perspectives Vermiculite ore from a mine near Libby, Montana, is known to be contaminated with amphibole asbestos (primarily winchite, rich- terite, and tremolite), which is liberated in the mining and processing of the ore [Agency for Toxic Substances and Disease Registry (ATSDR) 2008; Meeker et al. 2003]. The mining and processing of vermiculite in Libby have been associated with elevated mortal- ity from lung cancer, nonmalignant respira- tory disease, and mesothelioma (Amandus and Wheeler 1987; McDonald et al. 1986a; Sullivan 2007) in exposed workers, members of the community, and workers employed at distant vermiculite processing sites (Amandus et al. 1987; McDonald et al. 1986b; Peipins et al. 2003; Rohs et al. 2008). Environmental contamination from this source is not limited to Libby, as hundreds of thousands of tons of the ore were shipped throughout the country for processing. One of the destinations for the Libby vermiculite ore was the Western Minerals/W.R. Grace (WM/WRG) facility in Minneapolis, Minnesota. The WM/WRG facility processed ver- miculite ore mined in Libby, Montana, 44 from 1938 to 1989. This facility was one of approximately 250 such processing facilities in the United States that received Libby ore. At the WM/WRG facility, the vermiculite ore was heated in two furnaces and expanded in a process known as exfoliation to make Zonolite® insulation, Monokote® fireproof- ing, and other building materials. In addition to the vermiculite product, the exfoliation produced a waste material that contained up to 10% amphibole asbestos [Minnesota Department of Health (MDH) 2005]. The waste rock was piled on the WM/WRG property and offered freely to the commu- nity. A unique aspect of the WM/WRG exfo- liation site in Minneapolis is its location in a residential neighborhood: a mix of single- family homes, multifamily homes, schools, and churches. Neighborhood residents hauled the rock from the piles and used it for gar- dening and as fill material for driveways and yards. Neighborhood children also played on the piles of vermiculite processing waste, as access to the site was not restricted. The prox- imity of the neighborhood to the plant and the opportunities for contact with the waste