Evaluating Risks to Terrestrial Wildlife from Environmental Fluoride

Information and approaches to evaluating health risks to terrestrial wildlife from fluoride contamination in the environment are few in the literature. We use environmental field data from a phosphate ore processing site, toxicity reference values (TRVs), and bioaccumulation factors relative to site conditions to develop risk-based concentrations (RBCs) for total fluoride in terrestrial biota and soil. RBCs were derived specifically for forage that are protective of terrestrial mammalian and avian ecological receptors through multiple exposure pathways, and which can be used to evaluate site remediation or as environmental monitoring action levels. Following review of the literature, we recommend fluoride TRVs for mammalian and avian wildlife, and bioavailability factors for estimating exposures related to aerial deposition of fluoride and fluoride gases. For large ungulates, information on fluoride bioavailability from feed and soil, and related effects thresholds, are summarized from studies on grazing livestock. The resultant RBCs for fluoride in forage range from 14 to 63 mg/kg dry weight, based on no-effect and low-effect concentrations, respectively. These concentrations bracket most state, provincial, and international regulatory standards of vegetation levels for protection of livestock and wildlife.