Environmental Engineering Reference
In-Depth Information
Figure 2.12
Old house with exterior lead-based paint.
housing in the U.S. is considered to have LBP and poses a potential lead
exposure risk to children.
Direct and indirect exposures to LBP are considered to be the predom-
inant contributors to elevated blood lead levels (
g/dL) in children in
the U.S. Fifty million houses are estimated to contain LBP (defined as con-
taining 1 mg/cm
2
or 0.5% by weight), with about 12 million children under
the age of seven potentially exposed.
In the early history of LBP poisoning concerns, it was widely believed
(in the public health community and regulatory agencies) that childhood
lead exposures resulting in elevated blood lead levels (BLLs), and clinical
symptoms were the result of the ingestion of LBP chips from deteriorated
paint; ingestion was felt to be the result of compulsive mouthing behavior
(described as pica) by infants and toddlers, and lack of supervision by
parents, in low-income housing. In the 1980s, scientists concluded that the
major source of pediatric lead exposure was house dust contaminated with
lead from deteriorated LBP from interior and/or exterior sources. As a result
of epidemiological studies which linked BLLs in children to house and hand
dust, a consensus has emerged among research scientists and public health
officials that the primary cause of elevated BLLs in young children is hand-
to-mouth transfer of lead-contaminated house dust and soils through
infant/toddler mouthing behaviors.
Based on studies at the University of Cincinnati, a simple exposure
model was constructed to explain childhood lead exposures. This model was
to serve as a tool for intervention efforts in reducing BLLs in children at risk.
A modification of the Cincinnati model based on subsequent research studies
is presented in
Figure 2.13
.
The model shows various relationships which have been statistically
associated with elevated BLLs in children. Based on recent epidemiological
studies, approximately 41% of the lead content of house dust can be linked
to LBP, and another 18% with soil lead (passively transported indoors by
≥
10
µ
