Reducing children’s lead levels can lead to significant positive effects on test scores, according to a National Bureau of Economic Research working paper issued in August co-authored by Anna Aizer, associate professor of economics and public policy.
Though the United States currently has historically low lead levels, even low exposure can still negatively affect test scores. The study also found that “poor and minority children are more likely to be exposed to lead, suggesting that lead poisoning may be one of the causes of continuing gaps in test scores between disadvantaged and other children.”
“It’s pretty well established that children’s early exposure to lead affects the developing nervous system in ways that affect both cognitive performance and behavioral outcomes,” Aizer said. “Lead levels are at historic lows in the (United States), and so it wasn’t so clear … we would still expect to see the same thing.”
Aizer worked alongside Peter Simon, associate professor of the practice in epidemiology, Patrick Vivier ’85 MD’89, associate professor of community health and pediatrics, and Janet Currie, professor of economics and public affairs at Princeton. Together, they examined data from children born between the years of 1997 and 2005.
The study looked specifically at the effects of two Rhode Island policies that required landlords to mitigate hazards in their properties before renting them, lest they face prosecution from the state attorney general’s office. The policies intended to target high-risk areas with older homes more likely to contain traces of lead and more likely to house disadvantaged and minority children, according to Aizer and the study.
The policies led to decreased lead levels in children across the state, but more importantly, to disproportionately lower lead levels for children living in at-risk areas. Researchers also found a greater increase in test scores among African American and Hispanic children in comparison to white children, suggesting that the policies helped close the gap between black students’ test scores and white students’ test scores by 44 percent and the gap between Hispanic students’ test scores and white students’ test scores by 16 percent. Estimates also showed that “a one-unit decrease in average blood lead levels reduces the probability of being substantially below proficient in reading by 3.1 percentage points.”
The study mainly focused on reading test scores, since results for other subjects were more mixed and imprecisely measured, according to the study.
“We looked at math, (but) those estimates were a little noisier,” Aizer said. “We think (lead) just affects cognitive development more generally.”
In addition to demonstrating the negative effects of lead and the positive effects of lead reduction, the authors of the study suggested ways to help address lead remediation. Unlike most other states, Rhode Island mandates lead screening, providing hard data on lead levels that are necessary to understand a state’s lead burden, Aizer said.
The authors also wrote that Rhode Island’s policy for reducing lead exposure “offered more carrots than sticks in the sense that while some landlords were prosecuted, many others were offered training, loans and protection against future lawsuits.”
This strategy was “ultimately effective as opposed to … other states … where they use more sticks than carrots,” she said.
The paper addressed the possibility of other contributing factors affecting test scores and cognition beyond lead levels. The researchers were able to control the results by exploiting the lead policy changes requiring landlords to reduce hazards, Aizer said. In previous generations, there was no requirement, allowing researchers to compare two children born into the same geographical and cultural background but one born after the requirement and the other before, and see how the lead requirement affected their cognition without any other contributing factors, Aizer said.
Looking beyond the results of the study, Aizer said she hopes that educators will begin looking at more factors when addressing academic progress.
Education policy makers and educators “should think more about the importance of children’s background(s) and health as an important determinant of how they do in school,” Aizer said. “We can’t … think of these things as separate.”
Vivier, Simon, Michelle Kollett Almeida, lead program manager and program evaluator at the Rhode Island Center for Disease Control and Prevention, and Kimberly Pierson, director of data analysis at the Providence Plan, declined to comment or could not be reached for comment by press time.