“The Long-Run Spillover Effects of Pollution: How Exposure to Lead Affects Everyone in the Classroom”, 2024-02-16 ():
Children exposed to pollutants like lead have lower academic achievement and are more likely to engage in risky behavior. However, little is known about whether lead-exposed children affect the long-run outcomes of their peers.
We estimate these spillover effects using unique data on preschool blood lead levels (BLLs) matched to education data for all students in North Carolina public schools. We compare siblings whose school-grade cohorts differ in the proportion of children with elevated BLLs, holding constant school and peers’ demographics.
Having more lead-exposed peers is associated with lower high school graduation and SAT-taking rates and increased suspensions and absences.
…Our data indicate that in North Carolina public schools 2000–172017, 98.9% of middle school students without known lead exposure had at least one lead-poisoned child in their school cohort, 79.9% were in a school cohort with at least 5% lead-poisoned peers, and 52.5% were in a school cohort with at least 10% lead-poisoned peers.
…We find that a 10% increase in the share of cohort peers exposed to lead is associated with a 1.7 percentage point decrease in the likelihood that a child graduates high school, a 2% decrease in the graduation rate. Having more lead-exposed cohort peers is also associated with a higher likelihood of suspension from school, chronic absenteeism, and dropping out of school and a lower likelihood of taking the SAT. A back-of-the-envelope calculation suggests that the lost earnings of classmates of lead-poisoned children not graduating high school amount to $9.2 billion per cohort. Lead-exposed peers disproportionately affect the outcomes of black students, suggesting that the spillover effects of pollution could be contributing to persistent inequality in human capital accumulation. These findings are generally robust to different specifications that account for potential selection, omitted-variable, and measurement error biases.
To explore mechanisms, we find that exposure to lead-poisoned peers in middle school, rather than elementary school, appears to drive long-run outcomes. We also show that students who attend school with a higher share of lead-poisoned peers are more likely to be suspended and more likely to be involved in behavioral incidents with these lead-poisoned peers. We interpret our results as suggestive that noncognitive skill development might drive the spillover effects of lead poisoning through peers’ influence to engage in similar disruptive behavior.