New research that examined the impact of exposure to lead in the air and topsoil on fertility in the United States has found that exposure matters for both women and men. It is the first study to find causal evidence of the relationship between lead exposure and fertility rates in the 1980s and mid-2000s.
The researchers looked at U.S. Vital Statistics data on fertility, Environmental Protection Agency data for 1978-88 for airborne lead (covering more than a third of the U.S. population), and U.S. Geological Survey data in the 2000s on lead in topsoil (covering more than two-thirds of the U.S. population).
The study found that increased exposure to lead lowered the general fertility rate for women of childbearing age (15 to 44 years). In 1978-88, reductions in airborne lead, which were largely due to regulations such as the Clean Air Act, boosted fertility rates, and in the 2000s, higher levels of lead in topsoil decreased fertility rates.
“Until now, we have lacked causal evidence of the effects of lead exposure,” explains Karen Clay, professor of economics and public policy at Carnegie Mellon University’s Heinz College of Information Systems and Public Policy, who led the study. “Lead is an underappreciated environmental toxin, and we need to address this issue through cleanup efforts and solutions that focus on improving air quality and reducing lead in soil.”
Many Americans may not be aware that they live in counties with high lead levels because of highways, old manufacturing centers, or airborne lead that has landed on the soil. Our findings could help reduce this exposure,” said Edson Severnini, assistant professor of economics and public policy at Heinz College, who coauthored the paper, published by the National Bureau of Economic Research. “Lead may continue to impair fertility today.”