Low-Level, Early Life Lead Exposure and School Behavior.

Objectives: To measure how early childhood exposure to lead affects school behavior from third to eighth grade, measured by the number and days of total school suspensions and out-of-school suspensions (OSS).

Methods: We estimate Poisson models using a cohort of 284 701 students with school records from 2006-2008 in North Carolina. We adjust for demographic and socioeconomic variables and school-grade-year cohort effects, and use coarsened exact matching to ensure similar characteristics across children with blood lead levels (BLLs) 2-10 μg/dL and children in the reference group with BLLs ≤1 μg/dL.

Results: BLLs ≥3 µg/dL are positively and significantly associated with all school suspension measures for sixth through eighth graders. The estimated effects on OSS for sixth through eighth graders are larger than the effects on total suspensions. For example, students with BLL = 3 µg/dL receive OSS 16% (95% confidence interval 3.6%-30%) more often and for 22% (95% confidence interval 7.3%-33%) more days than students with BLL ≤1 µg/dL. For third through fifth grade students, we only find a significant effect of lead exposure on suspensions at relatively high BLLs of 8-10 µg/dL.

Conclusions: Our analysis demonstrates that BLL has significant adverse effects on third through eighth grade students' behavior, including at levels below the current Centers for Disease Control and Prevention's blood lead reference value of 3.5 μg/dL. We find that the adverse effects of lead are most strongly associated with more severe disruptive behavior in sixth through eighth graders, as measured by OSS. Our results underscore the long-term benefits of preventing early childhood exposure to lead.