In-utero personal exposure to PM(2.5) impacted by indoor and outdoor sources and birthweight in the MADRES cohort

BACKGROUND: In-utero exposure to outdoor particulate matter with aerodynamic diameter less than 2.5 μm (PM(2.5)) is linked with low birthweight. However, previous results are mixed, likely due to measurement error introduced by estimating personal exposure from ambient data. This study investigated the effect of total personal PM(2.5) exposure on birthweight and whether it differed when it was more heavily impacted by sources of indoor vs outdoor origin in the MADRES cohort study. METHODS: Personal PM(2.5) exposure was measured in 205 pregnant women in the 3rd trimester using 48 h integrated, filter-based sampling. Linear regression was used to test the association between personal PM(2.5) exposure and birthweight, adjusting for key covariates. Interactions of PM(2.5) with variables representing indoor sources of PM(2.5), home ventilation, or time spent indoors tested whether the effect of total PM(2.5) on birthweight varied when it was more impacted by sources of indoor vs outdoor origin. RESULTS: In a sample of largely Hispanic (81%) pregnant women, total personal PM(2.5) was not significantly associated with birthweight (β = 38.6 per 1SD increase in PM(2.5); 95% CI:−21.1, 98.2). This association however, differed by home type (single family home: 156.9 (26.9, 287.0), 2–4 attached units:−16.6 (−111.9, 78.7), 5+ units:−62.6 (−184.9, 59.6), missing: 145.4 (−4.1, 294.9), interaction p = 0.028) and by household air conditioner use (none of the time: −27.6 (−101.5, 46.3) vs. some of the time: 139.9 (42.9, 237.0), interaction p = 0.008) Additionally, the effect of personal PM(2.5) on birthweight varied by time spent indoors (none or little of the time: − 45.1 (−208.3, 118.1) vs. most or all of the time: 57.1 (−7.3, 121.6), interaction p = 0.255). CONCLUSIONS: While no significant association between total personal PM(2.5) exposure and birthweight was found, there was evidence that multi-unit housing (vs. single-family homes), candle and/or incense smoke, and greater outdoor source contributions to personal PM(2.5) were more strongly associated with lower birthweight.