Posted on | July 29, 2011 | 1 Comment
As school buses drive down the gravel roads in Dunn County, North Dakota, they stir up more than dirt. New research by University of Hawaiʻi Cancer Center Director Michele Carbone and colleagues shows the clouds of dust left in their wake contain such high levels of the mineral erionite that those who breathe in the air every day are at an increased risk of developing mesothelioma, a type of cancer of the membranes around the lungs. The new study, reported in the July 25 issue of Proceedings of the National Academy of Sciences, is the first to look at the potential hazards associated with erionite exposure in the U.S.
Erionite is a natural mineral fiber that shares similar physical similarities with asbestos. When it’s disturbed by human activity, fibers can become airborne and lodge themselves in people’s lungs. Over time, the embedded fibers can make cells of the lung grow abnormally, leading to mesothelioma.
Carbone had previously linked erionite exposure in some Turkish villages to unusually high rates of mesothelioma. Recently, he and colleagues turned their attention to potential erionite exposure in the U.S., where at least 12 states have erionite-containing rock deposits.
His research team focused their efforts on Dunn County, North Dakota, when they learned that rocks containing erionite have been used to produce gravel for the past 30 years. More than 300 miles of roads are now paved with the gravel.
The scientists compared the erionite in North Dakota to erionite from the Turkish villages. They measured airborne concentrations of the mineral in various settings, studied its chemical composition and analyzed its biological activity. Overall, the researchers found no chemical differences between the North Dakota erionite and samples of the cancer-causing mineral from Turkey. The airborne levels of erionite in North Dakota were comparable to levels found in Turkish villages with 6–8 percent mortality rates from mesothelioma, the researchers reported.
“Based on the similarity between the erionite from the two sources,” says Carbone, “there is concern for increased risk of mesothelioma in North Dakota.” The long latency period of the disease—it can take 30 to 60 years of exposure to cause mesothelioma—and the fact that many erionite deposits have only been mined in the past few decades suggests that the number of cases could soon be on the rise. In addition to North Dakota, California, Oregon, Arizona, Nevada and other states have erionite deposits, but the possibility of human exposure elsewhere in the U.S. has not yet been investigated.