Immunotoxicological and neurotoxicological profile of health effects following subacute exposure to geogenic dust from sand dunes at the Nellis Dunes Recreation Area, Las Vegas, NV

Abstract

Exposure to geogenic particulate matter (PM) comprised of mineral particles has been linked to human health effects. However, very little data exist on health effects associated with geogenic dust exposure in natural settings. Therefore, we characterized particulate matter size, metal chemistry, and health effects of dust collected from the Nellis Dunes Recreation Area (NDRA), a popular off-road vehicle area located near Las Vegas, NV. Adult female B6C3F1 mice were exposed to several concentrations of mineral dust collected from active and vegetated sand dunes in NDRA. Dust samples (median diameter: 4.4 μm) were suspended in phosphate-buffered saline and delivered at concentrations ranging from 0.01 to 100 mg dust/kg body weight by oropharyngeal aspiration. ICP-MS analyses of total dissolution of the dust resulted in aluminum (55,090 μg/g), vanadium (70 μg/g), chromium (33 μg/g), manganese (511 μg/g), iron (21,600 μg/g), cobalt (9.4 μg/g), copper (69 μg/g), zinc (79 μg/g), arsenic (62 μg/g), strontium (620 μg/g), cesium (13 μg/g), lead 25 μg/g) and uranium (4.7 μg/g). Arsenic was present only as As(V). Mice received four exposures, once/week over 28-days to mimic a month of weekend exposures. Descriptive and functional assays to assess immunotoxicity and neurotoxicity were performed 24 h after the final exposure. The primary observation was that 0.1 to 100 mg/kg of this sand dune derived dust dose-responsively reduced antigen-specific IgM antibody responses, suggesting that dust from this area of NDRA may present a potential health risk.

Health effects following subacute exposure to geogenic dust collected from active drainage surfaces (Nellis Dunes Recreation Area, Las Vegas, NV)

“…No significant changes in organ weights or in spleen or thymus cellularity were observed for any replicate. No significant changes were observed in mice exposed to TiO 2 [18] .…”

“…As mentioned previously, the drainage areas of CBN 4 contain sediments that have the highest concentrations of heavy metals of all seven of the CBN regions in the NDRA and are heavily used for ORV activities. Our previous publications evaluating other types of sediments, including sand dunes with and without vegetation [18] , arsenic-rick silty sediment [10] , and desert pavements [17] , however, suggest that geogenic dusts from CBN 4 do not suppress the humoral immunity as severely as dusts from these other three sites. Sediments from sand dunes produced the lowest LOAEL, at 0.01 mg/kg [18] .…”

“…Toxicity testing was evaluated in the TiO 2 -exposed mice in parallel with CBN 2-exposed mice. Data, although relevant to this study too, have been reported in a previous publication with a different geogenic dust [18] .…”

“…Briefly, as described in [18] , sera, spleens, thymuses, and brain were prepared and evaluated in the following assays.…”

“…As described in Keil et al [18] , separate groups of mice (N = 6/dose) were exposed to titanium dioxide (TiO 2 ), a particle with no associated metals (21 nm in size), to help us to discern potential particle-only effects from the effects of metals and particles together. Mice were given matching concentrations (0.01–100 mg of TiO 2 /kg of body weight) and were exposed via the same paradigm, as the geogenic dusts.…”