Mineralogy, Trace Element Chemistry and Potential Health Implications of Dust Samples From the Nellis Dunes Recreational Area, Nevada, USA.

Field and laboratory experiments were performed in the Nellis Dunes Recreational Area (NDRA) to evaluate potential health effects associated with dust emissions from both natural conditions (wind erosion) and off-road vehicular usage.  Soil samples were collected from the upper 2-3 cm from 17 map units and 5 parking lot locations for x-ray diffraction (XRD) and chemical analyses using inductively coupled plasma mass spectroscopy (ICP-MS).  The map units are based on surficial characteristics that affect dust emissions and are grouped into four categories:  sand and sand-affected areas, silt/clay areas, rock-covered areas, and drainages.  Dust emissions were measured from each surface unit and additional samples were collected from 16 of the 17 map units for chemical analyses using a Portable In Situ Wind Erosion Laboratory (PISWERL).  The PISWERL samples were collected both on the roads and near the roads; samples could not be collected from areas of outcropping bedrock or outcropping petrocalcic horizons.  The mineralogical composition of the 20-60 µm and 60-100 µm fractions of the soil and parking lot samples consists mainly of quartz and calcite, with lesser amounts of plagioclase and alkali feldspars.  The mineralogical composition of the clay (<2 µm) and silt (2-20 µm) fractions consists mainly of smectite with lesser amounts of mica/illite, kaolinite, quartz and calcite.  Nearly all of the samples also contain chlorite, palygorskite, and plagioclase and alkali feldspars.  Elevated concentrations of arsenic (As) are present in the soil and parking lot samples (3.49 to 83.02 µg g^-1) and in the PISWERL samples (16.13 to 312 µg g^-1).  The lower concentrations in the soil samples are expected because of the larger particle size (<2 mm) of the soil samples as compared to the PISWERL samples (<10 and 10-60 µm).  Soluble As in the PISWERL samples is as high as 14.7 µg g^-1.  Concerns regarding the emissions from this site are greater than those normally associated with particulate matter because of the high As concentrations and widespread occurrence of palygorskite.  Exposure to As has been strongly linked to heart disease, hypertension, peripheral vascular disease, diabetes, immune suppression, acute respiratory infections, intellectual impairment in children, and skin, lung, prostrate, bladder, kidney and other cancers.  Additionally, As has been found to be uniquely harmful to lung tissue by inhibiting wound repair and altering genes associated with immune functions in lung tissue.  Palygorskite has a fibrous morphology similar to asbestos and has been found to induce lung cancer in rats as well as other deleterious health effects.