Long-term exposure to criteria air pollutants and infant mortality: a systematic review and meta-analysis

We conducted a systematic review/meta-analysis for epidemiologic evidence of the association between long-term criteria air pollution (nitrogen dioxide (NO₂), sulfur dioxide (SO₂), coarse particulate matter (PM₁₀), fine particulate matter (PM_2.5), ozone (O₃), carbon monoxide (CO)) exposure and all-cause, respiratory, and sudden infant death syndrome (SIDS) infant mortality.

Studies were identified through PubMed/Web of Science databases using comprehensive search terms, then screened using predefined criteria. For studies eligible for inclusion in meta-analyses, we applied a systematic rubric for evaluating study quality across domains: participant selection, outcome, exposure, confounding, analysis, selective reporting, sensitivity, overall quality. When ≥3 eligible studies provided effect estimates, we performed meta-analyses to estimate pooled odds ratios (ORs) and 95% confidence intervals (95% CI) for air pollutants and infant mortality.

Of the 701 initial studies, we excluded 678 studies in the abstract screening and full text screening phases, leaving 23 studies for inclusion. Four studies included extractable effect estimates for PM₁₀ and seven for PM_2.5. We could not conduct meta-analyses for CO, O₃, NO₂, or SO₂ because each had <3 eligible studies. The pooled OR (95% CI) for a 10-μg/m³ increase in PM₁₀ concentration was 1.04 (1.02, 1.06) for all-cause, 1.11 (1.02, 1.21) for respiratory, and 1.05 (0.98, 1.13) for SIDS infant mortality. The pooled OR for a 5-μg/m³ increase in PM_2.5 concentration was 1.02 (0.98, 1.05) for all-cause, 0.83 (0.30, 2.27) for respiratory, and 0.97 (0.88, 1.08) for SIDS infant mortality.

Long-term exposure to PM₁₀ is associated with all-cause and respiratory infant mortality across studies.