New cases of lead contamination around the United States are reintroducing Americans to the negative health effects associated with living near toxic soil, air, or water. A group of Northwestern researchers recently discovered that such contamination also has unwanted cognitive effects, some of which begin before birth.
“People tend to think that environmental factors start playing a role in children’s lives once they’re born, but more commonly we’re finding that the air mom breathes and the water she drinks are also affecting her child in utero,” says economist David Figlio, education and social policy, who directs Northwestern’s Institute for Policy Research.
His research, in collaboration with recent Northwestern PhD graduate Claudia Persico (now a professor of education at the University of Wisconsin-Madison), examined Florida siblings living within two miles of Superfund sites — locations polluted with hazardous materials that require long-term cleanup. One sibling was conceived prior to or during the cleanup, while the other was conceived after cleanup was completed.
By comparing siblings, the team eliminated external factors that could have affected results, such as parenting quality, home environment, or relocation away from the toxic site. This approach allowed the team to assume that the only variable between the siblings’ conceptions was the cleanup of the Superfund site.
“We threw all of our ammunition at this problem to be sure that toxic waste is the thing affecting cognitive development, not any other variable,” Figlio says. “And we are able to point to a critical period in a child’s life when this is happening.”
The team found that siblings conceived before or during the cleanup were more likely to repeat a grade, have lower test scores, or be suspended from school. They also discovered that children conceived by mothers living within one mile of a Superfund site before it was cleaned were 10 percent more likely to be diagnosed with a cognitive disability. Once the site was cleaned, test scores dramatically improved and rates of new disability were cut in half.
Since 1980, the Environmental Protection Agency has identified more than 15,000 Superfund sites, and census data show that low-income families are more likely to live near these polluted locations. Understanding the link between proximity to Superfund sites and cognitive development, Figlio says, is important to drive momentum toward prioritizing site cleanup, but it also makes a good financial and policy argument.
“Even if we don’t consider the human capital of these kids,” Figlio says, “a typical Superfund cleanup will pay for itself in 38 years in terms of reduced special education costs alone.”