Arsenic-Trials, Tribulations and Triumph in Site Remediation

摘要

For better or worse, arsenic possesses a notoriety when it comes to setting acceptablelimits for soil remediation. It is unquestionably a human carcinogen and the subject ofconsiderable continuing research regarding its mode of action. There is on-going debateas to the applicability of the cancer slope factor (determined by the US EPA, andindependently corroborated by the US National Academy of Sciences, from studies ofTaiwanese communities exposed to high drinking-water levels of arsenic) inextrapolating to low level exposures.In many parts of the world, particularly in jurisdictions that have not set their own soilclean-up guidelines, the approach adopted by the US EPA is taken as the "default".However, uncritical application of this approach can lead to difficulties, for regulatoryauthorities and the entities whom they regulate, in arriving at practicable solutions formany "real-life" remediation projects. The soil clean-up target level based on the cancerslope factor can lead to remediation targets that are lower than natural levels in thesurrounding soils.In this paper, we examine general approaches taken by Australia, Canada, UK (inaddition to the US EPA) in handling soil-remediation guideline-setting for arsenic. Welook at the cancer slope factor question, and discuss the role of bioiavailability of arsenicfrom soil matrices and of house dusts on the human exposure and realistic quantificationof exposure through such pathways as house dust and remediated soil in a suburbanresidential development.We conclude by describing a successful outcome of the approach in the cost effectiveremediation of a substantial industrial site located near Cape Town, South Africa.