Mining activities can result in the transfer of harmful elements, including arsenic and lead, into the environment. In Australia, one of the potential future uses of rehabilitated mine land is to stock grazing animals. Elemental uptake is dependent on bioavailable fraction for adsorption upon exposure. Bioavailability data are generally lacking in order to provide realistic health risk assessments relating to harmful elements from mine tailings in Australian conditions. Another key component of risk assessment is the ability to estimate a realistic exposure, or dose rate, of the tailings to the grazing cattle over a set period of time. Hence, we aimed to conduct grazing trials directly on rehabilitated tailings facilities in order to provide valuable in situ information on heavy metal dose rates and associated accumulation. For the laboratory-based evaluation of comparative bioavailability, groups of cattle were fed five days a week on a normal diet spiked with mine tailings or soluble pure salts of target elements (eg sodium arsenate, sodium arsenite and lead acetate) for about eight months. For the field validation, cattle were allowed to graze directly on rehabilitated tailings facilities over a similar length of time. Blood and a biopsy of the muscle and liver were periodically collected to monitor arsenic accumulation. At necropsy, blood, muscle, liver, kidney and other saleable tissues were measured for arsenic concentrations. Although this study was focused on arsenic, lead and other metals were also measured. Predictive models for arsenic and other metals have been established to calculate the maximum grazing duration without the risk of exceeding specific food safety guidelines. The outcome of this study is a predictive model for maximum beneficial use of certain rehabilitated tailings for cattle grazing where grazing activities do not impact on the integrity of the tailings dams.

In Australia, the main future use of rehabilitated mine land is to stock grazing animals. Criteria for environmental management and rehabilitation of mine sites have become more stringent with the increasing awareness of the potential of harmful elements including arsenic in tailings. Bioavailability data are lacking to provide realistic health risk assessment of arsenic from mine tailings in Australian conditions. For the evaluation of comparative bioavailability, groups of three cattle were fed 5 days a week, a diet spiked with mine tailings or sodium arsenate or arsenite for 8 months. Blood, biopsy of the muscle and liver were periodically collected to monitor arsenic accumulation. At necropsy, blood, muscle, liver, kidney and other saleable tissues were measured for arsenic concentrations. For field validation, cattle were allowed to graze on rehabilitated tailings facilities over 6.5-8 months. The field data confirm the relative low bioavailability of arsenic from mine tailings to grazing cattle. The rehabilitated mine tailings under the test conditions appear to be suitable for grazing animals with no foreseen adverse health effects. Results obtained from this animal model should be a useful tool for rehabilitation design of mined land in order to minimise adverse health effects on animals and humans. More data of this type will help regulatory agencies to develop guideline values and policy in relationship to mine closure.