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

Abstract

Aim: 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.

Methods: 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.

Results: 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.

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

Keywords: Air pollution; Infant mortality; Long-term exposure; Meta-analysis; Systematic review.