In Marquette County, Michigan, Cliffs Natural Resources operates two proximal large open pit iron mines and processing facilities that extract magnetite and hematite for steel production (Cliffs Natural Resources 2012). These mining operations have introduced selenium (Se) into the local watershed through processing outflows and surface water runoff. In 2008 the Environmental Protection Agency (EPA) promulgated more stringent standards for Se emissions in water basins. This required Cliffs Natural Resources (Cliffs), to reduce the amount of Se released to the environment. The Michigan State University Wildlife Toxicology Laboratory was tasked as a third party to determine the Se and Hg exposure to select avian species and if there were any negative effects associated with the presently bioavailable Se to birds residing in the Cliffs Mining Operations (CMO)-associated watersheds.A multiple lines of evidence approach was used to assess the exposure and potential for effects from mine-associated Se exposure. These multiple lines of evidence included measuring reproductive effectiveness through hatching and fledging success rates, measuring concentrations of Se and Hg in avian eggs and prey items, and assessing avian embryos for teratogenic effects associated with Se toxicity. Results indicated that nest abandonment rates were greater than expected in waterfowl. Selenium exposure as measured by egg tissue concentrations exceeded concentrations expected to cause adverse effects in eight of 287 eggs collected and teratogenic effects were observed in two of 287 reproductive attempts observed.
Read
