Long Reach of Lead : Early Childhood Lead Exposure and Cognitive Ability Later-in-Life

Provisions of the Clean Air Act targeted the anti-knock lead additive tetraethyl-lead in automotive gasoline, specifying a phase-out schedule commencing in 1975. Because emissions from automobile gasoline were the predominant source of lead exposure in children, the phase-out caused a precipitous drop in measured child blood lead levels. Exigencies pertaining to petroleum and automobile industries caused meaningful variation in lead emissions across states between 1975 and 1990. Exploiting this temporal and spatial variation in the phase out leaded gasoline, we estimate the deleterious effects of early childhood lead exposure on standardized test performance later-in-life. Using a nationally representative sample of individuals born during the phase out, we find consistent evidence of later-in-life impairment on standardized tests from early childhood lead exposure. Paralleling observed reductions in gasoline tetraethyl-lead concentrations and child blood lead levels, we find that policy-caused reductions of childhood lead exposure improved test scores by 0.13 to 0.17 standard deviations. We find that the suppression of standardized test performance from early childhood lead exposure was likely dose-responsive and uniform through the distribution of test performance. Together, results are compatible with the nascent but growing scientific literature on the longer-term health and human capital consequences of early childhood lead exposure