Sustainable health-based soil standards for arsenic using epidemiological data and toxicokinetic/probabilistic modelling.

Abstract

This study presents an alternative method to the traditional reference dose approach for the determination of health risk-based soil standards for arsenic. The model combines multimedia equations for air, soil and dietary exposure, a toxicokinetic component, a probabilistic output, a reference distribution for urine arsenic in the general population and exposure parameters values traceable in US-EPA or EFSA reference studies. The model calculates a mean inorganic As urine concentration AsU (sum of inorganic arsenic Asi and its metabolites) from environmental data and exposure parameters, which is attributed to the central value of a lognormal distribution. Risk is assessed by comparing a high percentile of the modelled distribution to the target AsU attributed to the reference value of 10µg/gCREA (microgram As per gram of creatinine), the upper confidence interval of the 95th percentile from the AsU distribution in the French population. A soil standard value of 40mg/kg is determined as being the arsenic concentration in soil not giving rise to more than 5% probability of having a AsU concentration above the target value of 10µg/gCREA. Once soil As concentrations above 40mg/kg are measured, further environmental investigations should be carried, involving an assessment of As bioaccessibility to address health risks and decide of regulatory measures in residential setting.