Lead Exposure Reduces Academic Performance: Intensity, Duration, and Nutrition Matter

Abstract

We leverage a natural experiment, where a large national automotive racing organization switched from leaded to unleaded fuel, to study how ambient lead exposure and nutrition impact learning in elementary school. This provides quasi-experimental evidence linking measured quantities of lead emissions to decreased test scores, information essential for policies addressing ambient lead and emission sources. We find increased levels and duration of exposure to lead negatively affect academic performance, shift the entire academic performance distribution, and negatively impact both younger and older children. Exposure to 10 additional kilograms of lead emissions from lead-fuel races reduces standardized test scores by 0.06 standard deviations, where the average race emitted more than 10 kilograms of lead — a quantity similar to the annual emissions of an airport or a median lead-emitting industrial facility in the United States. This corresponds to an average income reduction of $2,600--$4,000 per treated student in present value terms, an effect size similar to improving teacher value added by one-sixth of a standard deviation, reducing class size by 3 students, or increasing school spending per pupil by $500. The marginal impacts of lead are larger in impoverished, non-white counties, and among students with greater duration of exposure, even after controlling for the total quantity of exposure. Factors correlated with better nutrition — most notably consumption of calcium-rich foods like milk — are associated with smaller negative effects of lead exposure. These results suggest that improved child nutrition can help combat the negative effects of lead, addressing several prominent social issues including racial test gaps, human capital formation across income groups, and disparities in regional environmental justice. Institutional subscribers to the NBER working paper series, and residents of developing countries may download this paper without additional charge at www.nber.org.