Research

Abstract. NASCAR-sanctioned races used leaded gasoline through 2006, generating concentrated bursts of airborne lead emissions around active racetracks. I study how these exposures affected infant health using detailed Texas birth records linked to race events at Texas Motor Speedway (TMS) in Fort Worth. Identification relies on within-TMS variation in distance, wind direction, race timing, and race-specific emissions among mothers living within 25 km of the same track. Pre-ban trimester-specific log emissions reduce birthweight, shorten gestation, and increase the probability of low birthweight. A post-ban placebo yields coefficients near zero, suggesting that the estimated effects are not driven by factors correlated with race activity. To translate intermittent race-day exposures into pregnancy-relevant blood lead burdens, I develop a pregnancy-specific physiologically based pharmacokinetic (PBPK) model that simulates daily maternal and fetal blood lead trajectories using each mother's race-event history. A one-standard-deviation increase in second-trimester PBPK blood lead reduces birthweight by approximately 73 grams. A significant post-2007 birthweight decline near a former Houston racetrack, unrelated to lead exposure, suggests the limitations of cross-track comparisons and highlights the importance of exploiting within-track variation. I then examine potential mechanisms and find that lead exposure increases gestational hypertension and shortens gestation, with both effects disappearing after the transition to unleaded fuel. These findings suggest that even relatively small and intermittent sources of airborne lead can have meaningful effects on infant health.