Current English policy and practice allows, and in places encourages, site specific estimates of arsenic oral bioavailability to be used in detailed quantitative human health risk assessment. English land contamination legislation does not differentiate between natural and man made arsenic soil contamination. English planning guidance requires developers to demonstrate that new houses are fit for purpose, including ensuring that there are no unacceptable risks to human health from soil contaminants. Naturally occurring arsenic in soils at a new housing site in southwest England was demonstrated not to pose unacceptable risk to human health by site specific estimates of bioavailability and region specific estimates of soil to plant uptake factors. Independent lines of evidence were used to justify the arsenic exposure factors for oral bioavailability and soil to plant uptake. Using site specific assessment criteria based on tools and information that give a better estimate of the actual exposure avoided both unnecessary public concern and considerable local authority expenditure across the outcrop of such soils as part of their legal duties.