6. Exposure Through Soil and Dust Ingestion

The current chapter discusses soil and dust ingestion, a potentially important pathway for non-dietary oral exposure, especially for children. Starting from clear definitions on what is meant by soil and dust and how they interrelate, it explores the several approaches that have been used to derive estimates of soil and dust ingestion rates. It concludes that tracer methodology studies, with all their limitations and uncertainties, probably provide the most adequate estimates of soil ingestion rates. However, these studies are limited to short-term estimates and do not distinguish between soil and dust. Hand-loading studies can be designed so that information is collected for the micro-environments we are interested in, but the interpretation requires assumptions about transfer parameters, which may introduce substantial uncertainty. Biokinetic modelling studies only provide rough estimates or ranges of estimates, but are nevertheless useful as a complementary line of evidence. From a comparison of these approaches it is concluded that average soil and dust ingestion rates for children are below 100 mg/d and most likely around 50 mg/d, a conclusion that is confirmed by the most recent evaluations published in literature. Still, good estimates of site-specific soil and dust ingestion rates for Europe are lacking due to paucity of data on age-related time activity patterns, transfer factors and intrinsic differences in children’s behaviour.