Does short-term, airborne lead exposure during pregnancy affect birth outcomes? Quasi-experimental evidence from NASCAR's deleading policy

Abstract

Background: There is evidence of a weak placental-fetal barrier to lead, suggesting that maternal lead exposure could affect the fetus. The health consequences for newborns from in utero lead exposure are not well understood. Objectives: We estimated the effects by trimester, of short-term (<1 week), airborne lead exposure during pregnancy on birth outcomes. Methods: We use quasi-experimental variation in airborne lead exposure during pregnancy, based on NASCAR's deleading of racing fuel in 2007, in a difference-in-differences model, to estimate the effect of deleading on the birth outcomes of all live births (n = 147,673) in the Charlotte-Concord-Gastonia Metropolitan Statistical Area between 2004 and 2009. Results: After deleading, children born to mothers residing <4000 m of Charlotte Motor Speedway (relative to those residing >10,000 m) experienced an average increase in birthweight (BW) of 102.50 g [P < 0.001]. The probability of low birthweight (LBW) declined by 0.045 [P = 0.001], preterm (PRE) births by 0.03 [P = 0.04], and small for gestational age (SGA) by 0.04 [P = 0.002]. We find that benefits accrue primarily in preterm LBW and SGA babies, and from decreased lead exposure in the first trimester. Conclusions: Short-term exposure to airborne lead during pregnancy adversely affects birth outcomes. Reducing even very brief exposure to airborne lead during pregnancy may improve birth outcomes.