Early childhood lead exposure and the persistence of educational consequences into adolescence

There is consensus that early childhood lead exposure causes adverse cognitive and behavioral effects, even at blood lead levels (BLL) below 5 microg/dL. What has not been established is to what extent the effects of childhood lead exposure persist across grades.

To measure the effects of early childhood lead exposure (BLL 1-10 microg/dL) on educational performance from grades 3-8; to determine if effects in lower grades persist as a child progresses through school; and if so, to characterize the pattern of persistence.

We examine data from 560,624 children living in North Carolina between 2000 and 2012 with a BLL ≤10 microg/dL measured between age 0-5 years. Children are matched to their standardized math and reading scores for grades 3-8, creating an unbalanced panel of 2,344,358 student-year observations. We use socio-economic, demographic, and school information along with matching techniques to control for confounding effects.

We find that early childhood exposure to low lead levels caused persistent deficits in educational performance across grades. In each grade (3-8), children with higher blood lead levels had, on average, lower percentile scores in both math and reading than children with lower blood lead levels. In our primary model, we find that children with BLL = 5 microg/dL in early childhood ranked 0.90-1.20 (1.35-1.55) percentiles lower than children with BLL ≤ 1 microg/dL on math (reading) tests during grades 3-8. As children progressed through school, the average percentile deficit in their test scores remained stable.

Our study shows that the adverse effects of early childhood exposure to low lead levels persist through early adolescence, and that the magnitude of the test-score percentile deficit remains steady between grades 3-8.