Policy ForumENVIRONMENTAL HEALTH

# The Paradox of Lead Poisoning Prevention

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Science  11 Sep 1998:
Vol. 281, Issue 5383, pp. 1617-1618
DOI: 10.1126/science.281.5383.1617

Subclinical lead toxicity, defined as a blood lead level of 10 μg/dl or higher, is estimated to affect 1 in every 20 children in the United States (1). The preponderance of studies demonstrate that low-level lead exposure has serious deleterious and irreversible effects on brain function, such as lowered intelligence and diminished school performance, especially from exposures that occur in early life; hearing deficits and growth retardation have also been observed (2). Collectively, the results of these studies argue that efforts to prevent neurocognitive impairment associated with lead exposure should emphasize primary prevention—the elimination of residential lead hazards before a child is unduly exposed. This contrasts, paradoxically, with current practices and policies that rely almost exclusively on secondary prevention efforts—attempts to reduce a child's exposure to residential lead hazards only after a child has been unduly exposed. Furthermore, despite an abundance of recommendations about how to prevent lead exposure from residential hazards, there is a paucity of data demonstrating the safety or benefits of these recommended controls for children with blood lead levels below 25 μg/dl (3).

## From Screening Children to Housing

Universal screening of children for elevated blood lead levels in the United States is controversial. Blood lead levels in U.S. children vary greatly by age, poverty level, race, and condition and age of housing (1, 6). Because lead exposure is so variable, few children are identified as having an elevated blood lead level in some communities. As a result, many pediatricians and public health officials are hesitant to support universal screening or vigorously oppose it. In addition, because lead exposure is cumulative and its detrimental effects are irreversible (7), any strategy that is limited to screening children after an exposure has occurred is flawed. Although there continues to be a need to refine screening strategies to target and identify children with undue lead exposure (8), it is more critical to expand our efforts to identify and eliminate residential lead hazards before children are unduly exposed.

## Residential Sources and Standards

Paint appears to be the major source of childhood lead poisoning in the United States. Children with blood lead levels above 55 μg/dl are more likely to have paint chips that are observable in abdominal radiographs, and most preschool children with blood lead levels greater than 25 μg/dl are reported to have put paint chips in their mouths (9). In contrast, house dust contaminated with lead from deteriorated paint and from soil tracked in from outdoors is the major source of lead ingestion for children with blood lead levels between 10 and 25 μg/dl (10, 11). More than 95% of U.S. children who have elevations in blood lead fall within this range (1).

Under section 403 of Title X, the U.S. Congress mandated that the Environmental Protection Agency (EPA) promulgate health-based lead standards and post-abatement clearance testing for house dust and residential soil. There are at least three reasons to develop residential lead standards. First, standards are necessary for screening high-risk housing to identify lead hazards before occupancy and before a child is unduly exposed. Our current strategy of identifying children only after they have been unduly exposed to lead rather than to screen high-risk housing before occupancy is analogous to the practice of sending a canary down a mineshaft to determine whether toxic gases have been released (see figures). Second, residential standards are critical to identify and eliminate lead hazards for children who already have elevated blood lead levels; major sources of lead will be neglected if dust and soil testing are not routinely done. Finally, standards serve as a benchmark and are necessary to compare the effectiveness and duration of various lead hazard controls.

## Prevention of Lead Poisoning

The costs of eliminating childhood lead poisoning from residential hazards are substantial. It has been estimated, for example, that the first-year cost of reducing residential lead hazards in federally owned or federally assisted housing would be $458 million. The overall estimated benefit, defined as increase in lifetime earnings of children who are protected from the detrimental effects of lead exposure, was$1.538 billion—a net benefit of \$1.08 billion (18). This estimate does not include other anticipated advantages, such as reduction in cardiovascular disease, behavioral problems, and delinquent behaviors.