NATURALLY-OCCURRING ASBESTOS AND INCREASED URBANIZATION IN CLARK COUNTY, NEVADA

Clark County is the southernmost county in Nevada, and home to nearly 2.3 million people, the vast majority of which live in the Las Vegas Metropolitan Area. Additionally, Clark County has seen over 16% growth in population since 2010. In 2013, the findings of naturally-occurring asbestos (NOA) in and around the Las Vegas Metropolitan Area was published (Buck et al., 2013). Human exposures of NOA are primarily through inhalation, and the arid climate of the Mojave Desert increases the potential for asbestos particles to become airborne through both natural and anthropogenic disruption of soil. Additional mapping and testing for NOA has significantly increased our knowledge of the extent of NOA in Clark County. We analyzed 241 samples using scanning electron microscope (SEM) and/or field emission scanning electron microscope (FE-SEM) with energy dispersive x-ray analysis (EDS). Subsets of the samples were also analyzed using wavelength dispersive electron probe microanalysis and the Fluidized Bed Asbestos Segregator preparation method.The sources of the fibrous amphiboles are hydrothermally-altered plutonic and metamorphic rocks. Wind and water erosion, transport, and deposition through time have resulted in widespread contamination of soils and sediments. Our results indicate that over 1 million acres, which is approximately 20% of Clark County, is predicted to contain NOA. In 2013, NOA was found to be directly in the path of the Boulder City Bypass, a portion of Interstate-11 that will connect Las Vegas, Nevada to Phoenix, Arizona. Due to Federal Occupational Safety and Health Administration (OSHA) regulations, these findings caused a delay in building this interstate while a mitigation plan was devised to protect the highway workers. The Boulder City Bypass has now been completed and it significantly increases human access to desert areas containing NOA. Many of the areas containing NOA are in or around urban centers (Las Vegas Metropolitan Area, Laughlin, Searchlight), and/or areas currently utilized or proposed for many other types of development including solar energy, off-road-vehicle (ORV) recreational areas, and low-income housing. The continued urbanization of Clark County Nevada will require increased attention to NOA as part of a larger land use management plan for this region.