An evaluation of the ecological hazards associated with cadmium in the Canadian environment

Abstract

This review was conducted to evaluate the potential hazards associated with releases of cadmium (Cd) into the Canadian environment. The hazard assessment consists of three elements: a focused review of the available data on the toxicology of Cd in various environmental media, a review of the available information on the concentrations of Cd in the Canadian environment, and a comparison of these data. Based on the review of the toxicological literature, the following lowest observed effect concentrations (LOECs) of Cd were identified for the most sensitive species: 0.17 μg∙L−1 in freshwater at a hardness of 48.5 mg∙L−1, 3.5 mg∙kg dry weight (DW)−1 in freshwater sediments, 1.2 μg∙L−1 in marine waters, 4.2 mg∙kg DW−1 in marine sediments, and, 2.0 mg∙kg DW−1 in soil. The freshwater LOEC was adjusted for hardness by a regression equation, so that LOECs could be estimated for waters of varying hardnesses; these LOECs ranged from 0.004 μg∙L−1at a hardness of 1 mg∙L−1 to 0.99 μg∙L−1 at a hardness of 300 mg∙L−1. Critical tissue concentrations (CTCs) in kidneys of 100 mg∙kg fresh weight (FW)−1 for birds and 30 mg∙kg FW−1 for mammals were also identified. Comparison of the empirically derived LOECs and CTCs with concentrations of Cd in Canadian ecosystems suggested that sensitive biota in the following environments may be adversely affected in some locations: surface freshwaters, freshwater and marine sediments, and soils. Some marine mammals, ungulates, and domestic horses are also at risk because of high renal Cd concentrations. The LOECs were exceeded most seriously in the vicinity of base metal smelters, indicating that these smelters represent significant hazards to local aquatic and terrestrial biota. In parts of Ontario, catchment acidification and deposition of aeolian Cd, presumably from other industrial sources, also appear to contribute to elevated Cd concentrations in freshwater systems. The extent and severity of contamination suggest that Cd is a significant threat to the integrity of Canadian ecosystems.Key words: cadmium, Canada, toxicology, contamination, hazard evaluation.