Opportunities and Challenges Associated with Bioavailability-Based Remediation Strategies for Lead-Contaminated Soil with Arsenic as a Co-Contaminant—A Critical Review

Purpose of Review The ubiquity of soil contamination by lead (Pb) and arsenic (As) has prompted the development of numerous techniques for its remediation. For human health exposure assessment, oral bioavailability-based methods are the most suitable to assess the efficacy of these treatment strategies, including in vivo relative bioavailability (systemic absorption relative to a toxicity reference) and in vitro bioaccessibility (dissolution in simulated gastrointestinal solutions). This paper provides a critical review of opportunities and challenges associated with the immobilization of Pb and As in contaminated soil. Recent Findings This review identified that the major inorganic and organic amendments used to reduce Pb and As exposure include phosphate, industrial by-products, metal oxides, organic matter, biochar, and treatment with iron sulphate to promote the formation of plumbojarosite in soil. In addition to RBA and IVBA assessment, investigating changes in Pb/As speciation in untreated vs treated soil can provide additional confirmation of treatment efficacy. The results of this review showed that immobilization efficacy may vary depending on amendment type, Pb, and As speciation in soil and the approach used for its assessment. Summary Reducing childhood exposure to Pb and As is a significant challenge, given the variety of contamination sources and treatment strategies. A lines-of-evidence approach using standardized methodologies is recommended for the assessment of immobilization efficacy to ensure exposure and risk reduction Graphical Abstract Bioavailability-based remediation strategies. Popular soil amendments to reduce Pb exposure include phosphate, industrial by-products, metal oxides, organic matter, and biochar; however, these may increase As exposure. The plumbojarosite formation technique has been recently developed to mitigate Pb and As exposure simultaneously. Multiple lines-of-evidence approach is recommended to assess treatment efficacy