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

Abstract

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. We estimated the effects by trimester, of short-term (<1 week), airborne lead exposure during pregnancy on birth outcomes. 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. After deleading, children born to mothers residing <4000m of Charlotte Motor Speedway (relative to those residing >10,000m) experienced an average increase in birthweight (BW) of 102.50g [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. 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.