Selenium-Accumulating Wildflowers in South Dakota; Evaluating Health Risks from Naturally-Occurring Uranium at the Former Badlands Bombing Range by Dr. Mike Lambert TOSNAC Presentation to Restoration Advisory Board August 27, 1998

Selenium l Selenium is an essential nutrient for all animals in trace quantities, but is toxic in large amounts. l Selenosis (“alkali disease”) happens when livestock drink water or eat plants with excessive selenium. l Selenium is not used in bombs or bomb casings; the selenium found at the BBR is from natural sources.

Selenium (continued) l Selenium in local bedrock formations can be as high as 23.1 ppm. l EPA RBC’s for selenium in soil are 390 ppm for residential sites, and 10,000 ppm for industrial (and agricultural) sites. l The highest concentration of selenium in groundwater at the nearby Former Black Hills Army Depot is 0.34 ppm. The EPA maximum level for drinking water is 0.05 ppm.

Selenium (continued) l Selenium can commonly be as high as 1 ppm in some plants, and can be as high as 1,000 to 15,000 ppm in a few plants. l Selenium over 2 to 5 ppm in forage is potentially hazardous to domestic animals. l Some plants in South Dakota have plants that can accumulate over 50 ppm selenium.

Uranium at the BBR l Maximum uranium concentration in soil in southern South Dakota is 11 ppm. l [U in Soil (ppm)] X X [Dust Action Level (mg/m 3 )] = U concen. as dust in air (mg/m 3 ). l If BBR soil created enough dust to create a health nuisance, uranium in that dust would still be 1,000 times below the level at which breathing the metal would be a health hazard. l However, inhalation as dust may not be as important for uranium as for other metals.

Uranium at the BBR (Con’t.) l Another way to look at the possible health risk posed by natural uranium is by comparing the level of uranium in BBR soil to the limits set by the EPA in their Region III RBC Table for residential and industrial sites. l That table sets a limit for uranium in soil at residential sites of 230 ppm, and at industrial (or agricultural sites) of 6,100 ppm. The highest level of uranium in soil found in southern South Dakota is 11 ppm.

Uranium at the BBR (Con’t.) l Even natural uranium is radioactive, and given enough time, will break down into other chemical elements, including radon. l Radon is a heavy gas that can cause cancer if it accumulates in closed areas, and if people are exposed to it over a long time. l The United States Geological Survey ranks southwestern South Dakota as having a moderate risk for radon.

Summary l Natural selenium in southwestern South Dakota can pose a health problem for livestock because of high concentrations in some aquifers, and because some local plants (loco weed, goldenweed, and prince’s plume) accumulate high levels of selenium. l Natural uranium does not seem to pose a health risk at the Former BBR.