Arsenic contaminated soils: human exposure and environmental toxicology

This research details a multidisciplinary assessment of arsenic contaminated soils in terms of human exposure and environmental toxicology. Two species of earthworm (Lumbricus rubellus and Dendrodrillus rubidus) along with their host soils and excreta (casts) were collected from 24 locations at Devon Great Consols (DGC), a former arsenic mine located in the Tavistock district of Devon, UK. Total arsenic in these samples was determined via ICP-MS. The bioaccumulation of arsenic in DGC earthworms was found to be comparable to the human bioaccessible fraction of arsenic in the host soils, estimated using a physiology-based extraction test (PBET), suggesting earthworms and PBETs might be used in conjunction when assessing risk at contaminated sites. Earthworms at DGC appear to be highly resistant to arsenic toxicity. The Comet Assay revealed DNA damage levels in earthworms native to DGC were comparable to background levels in earthworms from uncontaminated sites. Non-native earthworms exposed to a contaminated DGC soil incurred high levels of DNA damage, highlighting the potential toxicity of contaminated DGC soils. Arsenic biotransformation in DGC earthworms was investigated using HPLCICP- MS to investigate the mechanisms by which these earthworms mitigate arsenic toxicity. Whilst toxic inorganic arsenic was transformed to less toxic organic species, the degree of transformation was limited and not related to soil total arsenic levels, suggesting this mechanism is not involved in mitigating toxicity. Human toenail samples from DGC residents were investigated as a biomarker of exposure to elevated environmental arsenic and demonstrated significantly higher levels of arsenic than a control group. These findings highlight the potential for human exposure to arsenic at contaminated sites in the southwest UK, where mining activity has led to widespread environmental arsenic contamination.