Antarctica is often perceived to be a pristine environment largely untouched by the impacts of humans. In reality, legacy waste tip sites and human activities at research stations have resulted in localized contamination of terrestrial environments. Antarctic terrestrial micro-invertebrates (including rotifers, tardigrades, nematodes, and mites) are among the most physiologically extreme organisms on Earth, tolerating sub-freezing temperatures and desiccation. While remediation activities conducted by the Australian Antarctic Division are focused on reducing contaminant levels in soils, the actual impact of these contaminants to native biota is largely unknown. Sensitivity estimates based on toxicity tests with local biota are critical to informing remediation targets and to answering the question “how clean is clean-enough?” This project will use direct experimental exposure of selected contaminants found at legacy waste sites in Antarctica to native Antarctic micro-invertebrates. Culturing conditions will be optimized, and a battery of single-species toxicity tests developed for a range of common micro-invertebrates including several bdelloid rotifers, Acutuncus tardigrades, and Scottnema nematodes. Tests will provide sensitivity data using life history parameters including hatching success, maturity, reproductive output, and survival as end points. The hypothesis that widely distributed generalist species will have higher tolerance thresholds than specialist species will be tested. Novel toxicity tests developed for these organisms will provide essential experimental evidence for risk evaluation, risk assessments and post-remediation risk and efficacy. Results from this project will inform Antarctic contaminated site risk assessments and the development of environmental guidelines and standards for the Australian Antarctic Territory.