“…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] .…”