Application of the Navigation Guide systematic review methodology and meta-analysis to evaluate the association between prenatal particulate matter air pollution exposure and birth weight

Abstract

TPS 642: Environmental justice and impacts, Exhibition Hall, Ground floor, August 26, 2019, 3:00 PM - 4:30 PM Background: Case-control and cohort studies have demonstrated a positive association between prenatal exposure to particulate matter (PM) air pollution and low birth weight (LBW). Previous systematic reviews and meta-analyses report varying effect sizes and significant heterogeneity between studies. The considerable variation in study outcomes reflects methodological differences employed across studies. Objective: The objective of this study was to determine how developmental exposure to ambient particulate air pollution affects birth weight using the Navigation Guide systematic review methodology. Methods: We developed a study protocol and established a criteria to identify the relevant studies. Further, we determined the risk of bias for each study, conducted a quality of evidence and strength of evidence assessment, as well as a meta-analysis across all studies. Results: Forty-three studies met our inclusion criteria. We rated studies generally with low to probably-low risk of bias; however, several studies we judged as high or probably-high risk in the confounding and exposure characterization domains. Based on the meta-analysis, for every 10 µg/m3 increase in particulate matter, a decrease in birth weight was almost always negative. The strength of evidence assessment, for PM2.5, revealed “limited evidence of toxicity” for reducing birth weight when exposure is in the third trimester; for other exposure windows, the evidence is inadequate. For PM10, there is “limited evidence of toxicity” for reducing birth weight when exposure is in the third trimester and during the entire pregnancy; however, the evidence is “inadequate” for other exposure windows. For coarse PM (PM2.5-10), there is “inadequate evidence of toxicity” for reducing birth weight for all exposure windows. Conclusion: While sufficient evidence supports an association between prenatal exposure to ambient particulate matter and low birth weight, the estimated effect depends significantly on study design. Standardizing exposure characterization techniques could help reduce the variation in outcomes.