An assessment of the potential hazards of environmental selenium for Canadian water birds

Elevated dietary intake of selenium (Se) causes dramatic teratogenic and other reproductive effects in water birds at dietary levels only a few times greater than those that are generally regarded as nutritionally essential. Possible risks to the health of Canadian water birds and other wildlife from Se may be posed by seleniferous habitats in western Canadian provinces, and over-wintering by migratory water birds in some National Wildlife Refuges in the western U.S.A. where Se-related deaths and embryonic deformities in birds have occurred. These Refuges have in common an arid climate, closed drainage basins, seleniferous Cretaceous geology, and they receive irrigation drainage water from nearby agricultural areas. Similar conditions occur in SW Saskatchewan and SE Alberta, and these areas overlap parts of the critical water bird habitat of the region. Selenium concentrations in wetland ponds, agricultural tile drainage water and bird tissues in the western provinces are, with a few exceptions, generally lower than threshold concentrations for reproductive toxicity. However, some surface waters and aquifers contain dissolved Se concentrations that exceed guidelines for the protection of aquatic life, irrigation uses, and human and livestock drinking water. Use of this aquifer water for irrigation or replacement of freshwater flows into wetlands would greatly increase the risk of Se bioaccumulation to hazardous levels in water bird food chains.