OHV-GENERATED AND NATURAL DUST CONTAINING ARSENIC: PRELIMINARY HEALTH EFFECTS DUE TO ACUTE EXPOSURE, NELLIS DUNES RECREATION AREA, NEVADA USA

An increased risk of cardiovascular and respiratory morbidity, asthma, lung cancer, inflammation and increased mortality is associated with exposure to particulate matter. The largest single source of both PM10 and PM2.5 in the USA is road dust. In southern NV, the Nellis Dunes Recreation Area (NDRA) has been used for over 40 years for off-highway vehicle (OHV) recreation with an estimated 300,000+ drivers per year. We find that natural wind erosion is greatest in sandy areas, and OHV-generated dust emissions are greatest in the silty and rock-covered areas. Emissions from OHV activities increase exponentially with driving speed, and are highest for 4-wheelers. On an annual basis, OHV-generated emissions equal natural dust emissions. Extremely high concentrations of naturally occurring arsenic are present: in PM10 up to 290 ppm; in PM60 up to 312 ppm. Water-soluble arsenic is as high as 14.7 ppm for PM60. The dust also contains palygorskite, which commonly crystallizes in an asbestiform habit. Palygorskite fibers greater than 5 μm in length are believed to be possibly carcinogenic to humans. Emission rates for arsenic were calculated for 16 different surface types. Specific silt, rock-covered, and silty sand units have the highest arsenic emissions during OHV activities whereas sandy areas have the potential to emit the greatest amount of arsenic-containing dust during windy conditions. In vivo experiments were conducted in mice to examine the lung pathology, and immunotoxicological and histopathological effects following 3 daily exposures to dust samples from 3 surface types. Suppression of humoral immunity and alterations in lymphocytic cells populating the spleen were the most sensitive parameters affected. Currently, our research is measuring sub-chronic exposure to NDRA dust. Immuno- neuro- and general toxicology, lung pathology, and human exposure data are being collected to define site-specific parameters for probabilistic modeling of human health risks.