Assessing metals bioaccessibility to man in human health risk assessment of contaminated site

Sébastien Denys (1) , Karine Tack (1) , Julien Caboche (1) , Patrice Delalain (1)

1 INERIS - Institut National de l'Environnement Industriel et des Risques

Soil ingestion is a significant exposure pathway to Man for sites contaminated with heavy metals. In France, risk assessments on polluted soils currently consider the total soil metal content for calculation of the dose exposure to Man. However several studies done on animals showed that this assumption was not accurate as the total soil metal content was not available for absorption though the gastro-intestinal system. The fraction that is actually entering the systemic circulation is the bioavailable fraction and was shown to be dependent on the solid metal distribution (Casteel et al., 2001; Henningsen et al., 1998). Measurement of metal bioavailability can be done using animals (pigs and monkeys) having similar digestive conditions than Humans. However these experiments are costly and can be ethically problematic. These last years, both North American and European scientists developed chemical tests to measure the bioaccessible fraction of the soil metals. These tests are based on two or three steps extraction method that simulates the extraction of the metal by the digestive fluxes (saliva, gastric and intestinal conditions). These fractions were shown to be correlated to the bioavailable fraction for some metalloids (arsenic) or metals (lead). The bioaccessible fraction of metal is then used to correct the soil metal total concentration. This data can be used to improve the estimation of the external fraction of the contaminant that is available for absorption through the digestive tract. The objectives of this paper are to give a short overview of the methods available in the literature to assess the soil metal bioaccessibility, focusing on the tests developed by the European BARGE working group. One of these tests is then used on four soils sampled on a residential area on which soils are strongly contaminated with lead. Results of bioaccessibility are then discussed regarding the soil solid phase repartition of this metal using Tessier sequential extractions. Finally, a theoretical human health risk assessment is then carried out considering both the total and the bioaccessible lead fraction. Impact of bioaccessibility in terms of management of contaminated sites is then discussed.

Domaines: Sciences de l'environnement

Sébastien Denys, Karine Tack, Julien Caboche, Patrice Delalain. Assessing metals bioaccessibility to man in human health risk assessment of contaminated site. Conférence DIFPOLMINE : Quel devenir pour les grands sites pollués par des métaux ? What does the future hold for large metal-polluted sites, Dec 2006, Montpellier, France. pp.NC. ⟨ineris-00973245v1⟩