PM_2.5 metal constituent exposure and stillbirth risk in Harris County, Texas

There is limited evidence on the role of exposure to chemical constituents of fine particulate matter (PM_2.5) in risk for stillbirth. Thus, we conducted a case-control study in Harris County, Texas between 2008 and 2013, utilizing a 6:1 ratio of controls to individually matched cases. We linked birth and fetal death records with PM_2.5 data from a single air monitoring station and estimated maternal exposures to metal constituents of PM_2.5 over the risk period (defined by the gestational length of each case). We applied conditional logistic regression and modeled air pollutant exposures as continuous variables. We observed null associations for most metal constituents (Al, Cr, Cu, Fe, Pb, Mn, Ni, Se and Ti). However, we observed a modest increase in risk for stillbirth (adjusted odds ratio (OR) = 1.11, 95% confidence interval (CI): 1.02, 1.20) associated with a 0.007 μg/m³ interquartile range (IQR) increase in exposure to zinc (Zn) PM_2.5. This study adds to the scarce literature evaluating associations between PM_2.5 metal constituents and stillbirth and points to the need for further research in this area.