Over the past few weeks, we have analyzed the harmful effects of lead exposure on young people, explored the extent to which lead exposure still impacts us, and discussed some of the efforts underway to eliminate the troublesome element. Millions of dollars have been poured into efforts to safely remove lead from our homes, pipes, and schools, but do these expensive programs achieve results? In this final discussion, we will analyze the evidence to determine whether the proposals for removing lead to improve health are supported by the most up-to-date research.
We know that much of the lead that gets into children’s blood is from lead paint in older housing. It makes sense, then, that many of the public health interventions aimed at reducing blood lead levels would focus on the home for both primary and secondary prevention—that is preventing blood lead levels from ever rising and working to reduce the levels once they have risen, respectively.
Traditionally, home-based interventions for lead abatement have been categorized as education only, environmental abatement of soil and paint dust, or some combination of the two. The Cochrane Collaborative reviewed 14 studies that spanned these three categories and found that either education or environmental abatement alone was not sufficient to reduce blood lead levels or floor dust levels. The authors note that the studies may not have fully captured the benefits of an intervention because they did not follow the children for long enough to see the decline in lead levels in the blood. Lead remains in the blood for longer than the 12 months that the children were observed, but given the time that they studied, they did not see any statistically significant results.
At the time of the review, there was not sufficient evidence to evaluate how combining the education and environmental abatement would impact the effectiveness of an intervention. Our partners in Philadelphia—with whom we modeled the Asthma Home Remediation program—decided to evaluate an intensive intervention modeled after the city’s Lead Safe Babies program. Their intervention involved detailed education on sources of lead exposure and how to prevent it as well as evaluation and remediation of the home environment at both the time of birth and at 12 months of age for the baby. The goal was to intervene before the baby was exposed to any lead to analyze whether the intervention could prevent the accumulation of lead in the blood, thus eliminating the issues with analyzing blood that had lead remaining in it from years prior to intervention.
Ultimately, the Philadelphia study found few statistically significant results for even the most intensive intervention as compared to the control group that did not receive the education or environmental abatement. These results were largely in agreement with those of the prior studies. The average blood lead levels at 1 year of age were statistically equivalent, and there was only a slight improvement in the amount of lead dust found on windowsills and the floor. The real gains were in parental understanding of the sources of lead and methods of prevention. While this did not result in significantly lower levels of lead in the blood or in the dust, it did lead to a much greater rate of testing for the children in the intervention group. That means that even if the intervention did not prevent the lead entering the blood, it did increase the likelihood that if the child had some level of lead poisoning, that the parents and doctor would identify the issue.
The Philadelphia example is just one in a string of studies that have sought to understand how well abatement and education interventions prevent lead exposure. Generally, studies have indicated only modest results. One line of research analyzed whether combining abatement of soil with abatement of lead dust in the home would significantly reduce blood lead levels. While there was a slight improvement, it was much smaller than the researchers had anticipated, and it tended to only accrue to those individuals who did not have any lead dust inside the home.
The news is not all grim. A study from researchers at Johns Hopkins University indicates that in follow up analyses ranging from 1-3.5 years, levels of lead dust were significantly reduced after abatement protocols were implemented. Further, the Philadelphia results around increased blood testing of children should not be dismissed. These results give us hope that the interventions are achieving results, but there is clearly more to understand.
The next steps for the literature will be to explore how and why certain aspects of the interventions are or are not effective. As the national blood lead levels have decreased, research on the topic has seemed too slow. Many of the studies come from the early 1990s. Given the extent of the issue that we have explored, there is clearly an imperative to continue to explore the best methods for eliminating this risk to child development and health.