Based in part on a study led by researchers at the University of Cincinnati (UC), the U.S. Environmental Protection Agency (EPA) has developed a Human Health Risk Assessment for a Superfund environmental cleanup site in Libby, Montana.
From the 1920s until 1990, the town of Libby was the site of mining operations for vermiculite, a mineral used in building insulation and as a soil conditioner. According to the EPA, the vermiculite from the Libby mine contained a toxic form of naturally occurring asbestos that came to be known as Libby amphibole asbestos (LAA). When inhaled, LAA can cause cancer and non-cancer lung disease.
The EPA risk assessment includes an estimate of the amount of LAA that a person can breathe every day for a lifetime that is likely to not result in adverse non-cancer health effects. According to the EPA, this is the first such estimate regarding non-cancer effects for any type of asbestos. The assessment also finds that LAA is carcinogenic to humans when inhaled and provides a quantitative estimate of cancer risk.
In a December 2014 news release, the EPA said that it has been working in Libby since 1999 and that the Libby site was placed on the Superfund National Priorities List in 2002. In 2009, EPA and the U.S. Department of Health and Human Services announced a public health emergency at the site. Removal actions have now been completed at more than 2,000 properties at the site, including the most contaminated areas, and the EPA says the cleanup has reduced cancer and non-cancer risks there.
The EPA’s final Integrated Risk Information System (IRIS) health assessment was based in part on the work of the UC researchers, including faculty and staff members from UC’s departments of environmental health and radiology and the UC College of Allied Health Sciences’ Department of Rehabilitation Sciences. The researchers, in a study published in the January 2015 issue of the Journal of Occupational and Environmental Medicine, analyzed the potential effect on human health of low-level exposure to LAA.
James Lockey, MD, corresponding author of the study and professor emeritus in the UC Department of Environmental Health, said, "By following over 30 years a worker population in Ohio that worked with Libby vermiculite, we were able to identify progressive lung changes even though exposure to Libby vermiculite ceased in 1980.
"These findings will help inform U.S. public health policy in regard to environmental exposure to certain types of naturally occurring mineral fibers such as asbestos that exist in various geologic formations within our environment, particularly in the western United States.”
Lockey and his colleagues set out to understand the health impact of LAA, starting with workers at a plant expanding Libby vermiculite in Marysville, Ohio, who were originally studied by UC investigators including Lockey in 1980. Of the original 1980 cohort of 513, 431 were living and eligible to participate in the most recent study update and 306 provided chest scans or radiographs for evaluation.
The researchers evaluated chest images for evidence of radiographic changes historically associated with commercial asbestos exposure. Spirometry, a common test that measures how much air a subject inhales and exhales, was also conducted.
The results, Lockey says, demonstrated that very low lifetime cumulative exposure to LAA was significantly associated with chest radiographic changes and corresponding declines in spirometric values.
"These changes occurred at substantially lower cumulative fiber exposure levels than those commonly associated with commercial asbestos within the work environment,” says Lockey.
Co-investigators on the study were Kari Dunning, PT, PhD; Timothy J. Hilbert, MS; Eric Borton, MS; Linda Levin, PhD; Carol H. Rice, PhD; Roy T. McKay, PhD; Ralph Shipley, MD; Christopher A. Meyer, MD; Charles Perme, MD; and Grace K. LeMasters, PhD.