New Evidence on the Effectiveness of Early Interventions for Children With Lead Poisoning

Early childhood lead poisoning has been linked to detrimental effects on cognition, academic performance, IQ, high school graduation, and even adult earnings. In many countries, laws prohibiting the use of leaded gasoline have reduced lead exposure, but many children continue to be exposed to lead from deteriorating paint in older housing units. According to the National Survey of Lead and Allergens in Housing, an estimated 40 percent of housing units in the United States contain lead-based paint. This environmental hazard is also concentrated in certain areas, disproportionately affecting already disadvantaged communities.

Given the overwhelming evidence on the negative effects of lead poisoning among children, the Center for Disease Control (CDC) recommends testing young children for high blood lead levels (BLLs). If a child is found to have high BLLs, a series of interventions is triggered that includes lead remediation for the child and the prevention of further exposure. While children would ideally have no environmental exposure to lead at all, an important policy question is whether the existing interventions are effective in reversing the detrimental effects of lead poisoning. A recent study by Stephen Billings and Kevin Schnepel used administrative data from Charlotte, North Carolina, to evaluate the long-term impacts of these early childhood interventions for lead-poisoned children. Their research considered a range of behavioral and educational outcomes and found that the interventions could largely reverse the negative outcomes associated with early life exposure to lead.

In order to determine the causal impact on recovery of these interventions, children would ideally be randomly assigned to receive the treatment. In the absence of random assignment, the authors took advantage of the lead-testing process itself to construct a valid control group for the children who had received an intervention. North Carolina’s response to lead exposure followed CDC guidelines and conducted two consecutive tests of blood lead levels. Children who exceed the unsafe exposure threshold in one test but not in the second were ineligible for the elevated BLL intervention. To identify a causal impact of the intervention, the authors compared outcomes for children who were eligible for an intervention with those of children who initially had high BLLs (above the threshold), but whose confirmatory second test fell just below the threshold. In this way, the authors approximated random assignment by matching the two groups on observable characteristics and posited that children in the control group had fallen just short of the confirmatory threshold by random chance.

In North Carolina, the interventions triggered for children with two tests in excess of the alert threshold included nutritional advice and information for caregivers on reducing exposure in the home, a home environment investigation, and a referral to lead remediation services. Higher BLLs could trigger more intensive treatment. The authors merged data on BLLs, public school records, and criminal arrest records for children born between 1990 and 1997 in Charlotte-Mecklenburg County. Further, they constructed two indices—an education index and an adolescent antisocial behavior index—that combine a series of primary outcomes such as math and reading test scores, days suspended or absent, and whether the child was ever arrested. They found a statistically significant decrease in antisocial behavior among children whose BLL tests triggered interventions, relative to the control group, and a marginally significant increase in elementary and middle school academic performance. The magnitude of the results was also large. In fact, the authors claimed that the harmful effects of lead could be reversed to such an extent that children who tested above the threshold twice, when treated, could have similar outcomes to those observed in children with much lower levels of lead exposure.

The study evaluates a critical public health intervention that may help reverse the proven detrimental effects of early childhood lead exposure. While these interventions are expensive, with an estimated cost of approximately $5,200 per child, they pass a preliminary cost-benefit test due to the associated benefits in crime reduction and educational improvement. As policymakers continue to make the necessary long-term investment to eliminate environmental lead exposure altogether, these results suggest that early childhood intervention can prove effective and critical in limiting the damage from exposure.

Article source: Billings, Stephen B., and Kevin T. Schnepel. “Life After Lead: Effects of Early Interventions for Children Exposed to Lead.” American Economic Journal: Applied Economics 10, no. 3 (2018): 315-44.

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