Estimating the Contribution of Lead-Based Paint to Soil Lead, Dust Lead, and Childhood Blood Lead

Young children are particularly susceptible to lead carried in fine particles of surface soil (exterior dust) and in household dust. Multi-media environmental and biological samples may allow causal inferences about the relative importance of different sources and pathways in childhood lead exposure, and about the effectiveness of intervention strategies. Methods include: (1) statistical inferences about pathways using structural equation modeling; (2) inferences about pathways using physical tracers of sources; (3) inferences based on mass balance estimates. Structural equation modeling allows estimation of both direct and indirect exposures to lead-based paint. For example, chips of exterior lead-based paint may be ingested directly, may contribute to surface soil lead which is ingested, and may also be transported into household dust which is ingested. It is often possible to identify soil and dust exposure from elevated lead levels on the child's hands. We use structural equation models in cross-sectional field studies in some Western communities, to demonstrate the role of lead paint as a source of lead exposure. Stronger causal inferences about sources and pathways can be made when there are physical identifiers of the source, such as an unusual ratio of some stable lead isotopes. Another approach is to carry out an intervention, such as removal or encapsulation of the lead-based paint, or removal of the contaminated soil and dust associated with the paint. If lead-based paint is not removed and there is some recontamination of these media over time after the intervention, then we can attribute the exposure to lead paint.