A study by University of Nevada, Las Vegas geologists has identified toxic, naturally occurring asbestos in and around Boulder City, but further studies are needed to determine its health risk to residents.
The study, published in October in the peer-reviewed Soil Science Society of America Journal, states that researchers identified geologic formations they thought might be a source of asbestos, fibrous minerals that can be found as a natural component of rocks and soils.
They collected 43 rock, soil and dust samples from the dry lake bed, King Elementary School, the backyard of a residence and other areas. Researchers even sampled dust from a boot after a day in the field.
All 43 samples contained naturally occurring asbestos particles, which, according to the study, had never been reported in Clark County.
“What we think is this is an entirely new geologic way of forming these types of minerals and this is why nobody found it before,” said UNLV researcher Brenda Buck, the study’s lead author. “We’re really surprised.”
Buck said that the minerals collected in Boulder City were similar to the type of naturally occurring asbestos found in the town of Libby, Mont., where exposure from a nearby mine resulted in asbestos-related illnesses and unusually high mortality rates.
Like many forms of naturally occurring asbestos, the Libby minerals did not fall under the classification of the six federally regulated asbestos minerals often used for industrial purposes.
The majority of the minerals found around Boulder City, however, were classified as the toxic, regulated mineral actinolite, the study says.
“What we did was compared the length and width of the shape of the minerals here in Nevada to those in Libby,” Buck said. “Unfortunately they’re very similar in size and shape, and they’re one of the six regulated minerals, and that’s not a good thing.”
The most common health issue associated with environmental asbestos exposure is mesothelioma, a cancer of the lining of the lungs that typically doesn’t occur until 20 or more years after the microscopic fibers are inhaled, said James Lockey, a University of Cincinnati researcher.
The main problem with being exposed to asbestos, even in small quantities, is that asbestos never leaves the lung, Lockey said.
“If exposed, concentrations continue to build up and it gets higher and higher and at some point you reach a threshold where you start to see your body responding to them,” he said.
The study estimates 53,000 acres in and around Boulder City may contain the fibrous particles in the rocks and soil.
Boulder City has the highest potential for exposure to airborne fibers, but Henderson and eastern Las Vegas populations also may be at risk, the study states.
However, the study does not determine the public health risk associated with the finding.
“The study we’ve done now is a first pass to understand where they are and if (the fibers) are being distributed,” UNLV researcher and study co-author Rodney Metcalf said. “The real risk assessment needs to figure out what the concentration is in the air, and we don’t know that.”
To further examine the potential health risk in Southern Nevada, UNLV has partnered with the University of Hawaii and the Centers for Disease Control and Prevention.
Hawaii researchers will be conducting an epidemiologic study using Nevada cancer data collected by the CDC, and conducting laboratory experiments to determine the toxicity of the minerals found near Boulder City.
“We are going to be testing these fibers in mice,” Buck said.
The UNLV study is part of a larger interdisciplinary effort in the scientific community to understand naturally occurring asbestos, which only became a hot topic after Libby was named an Environmental Protection Agency superfund cleanup site in 2000.
For the past two years, a consortium of researchers from the UNLV, University of Hawaii, CDC, National Institutes of Health and the U.S. Geological Survey has been studying the issue.
“We’d like to know where asbestos occurs naturally geographically, and we’d especially like to know when that occurrence happens in proximity to human populations or whether there’s an exposure pathway,” NIH researcher Christopher Weis said.
Naturally occurring asbestos is not typically found in heavily populated areas, but some states where it is found near populations, such as Virginia and California, have made efforts to raise public awareness and reduce exposure.
Nevada does not regulate naturally occurring asbestos but, according to the UNLV researchers, efforts should be taken to avoid the creation of dust near Boulder City.
“I think people should not panic,” Buck said. “I also think people should be concerned enough to think about and take steps to avoid dust right now, until we know more about it.”