Pb particles from tap water: bioaccessibility and contribution to child exposure.

High particulate lead (Pb) levels can be measured in tap water, but the hazard linked to particulate Pb ingestion is unknown. An in vitro test was developed to determine the bioaccessibility of Pb particles from tap water, based on the Relative Bioaccessibility Leaching Procedure validated for soils, and applied to lab-generated particles and field particles collected behind the aerator tap. Field particles were found in 43% of the 342 taps investigated equipped with an aerator, and contained significant amounts of Pb (0.003-71%, median 4.7%). The bioaccessibility of lab-generated particles ranged from 2 to 96% depending on the particle type (Pb(II) > Brass > Pb(IV) > solder), while that of field particles was distributed between 1.5 and 100% (median 41%). The hazard of particulate Pb ingestion depends on the amount and concentration ingested, and the bioaccessibility of the particulate Pb forms involved. Using the Integrated Exposure Uptake Biokinetic model, the impact of particulate Pb on the exposure of children aged 0.5-7 for the distribution system studied was the most significant when considering a fraction of the exposure from large buildings.