Prenatal exposure to fine particles and polycyclic aromatic hydrocarbons and birth outcomes: a two-pollutant approach

BACKGROUND: Previous epidemiologic studies have considered the effects of individual air pollutants on birth outcomes, whereas a multiple-pollutant approach is more relevant to public health policy. OBJECTIVES: The present study compared the observed effect sizes of prenatal fine particulate matter (PM(2.5)) and polycyclic aromatic hydrocarbons (PAH) (a component of PM(2.5)) exposures on birth outcome deficits, assessed by the single vs. two-pollutant approaches. METHODS: The study sample included 455 term infants born in Krakow to non-smoking mothers, among whom personal exposures to PM(2.5) and PAH were monitored in the second trimester of pregnancy. The exposure effect estimates (unstandardized and standardized regression coefficients) on birth outcomes were determined using multivariable linear regression models, accounting for relevant covariates. RESULTS: In the single-pollutant approach, each pollutant was inversely associated with all birth outcomes. The effect size of prenatal PAH exposure on birth weight and length was twice that of PM(2.5,) in terms of standardized coefficients. In the two-pollutant approach, the negative effect of PM(2.5) on birth weight and length, adjusted for PAH exposure, lost its significance. The standardized effect of PAH on birth weight was 10-fold stronger (β = −0.20, p = 0.004) than that estimated for PM(2.5) (β = −0.02, p = 0.757). CONCLUSION: The results provide evidence that PAH had a greater impact on several measures of fetal development, especially birth weight, than PM(2.5). Though in the single-pollutant models PM(2.5) had a significant impact on birth outcomes, this effect appears to be mediated by PAH. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s00420-016-1192-9) contains supplementary material, which is available to authorized users.