Air pollution and birth outcomes: A systematic review

Department of Pediatrics, Mount Sinai Hospital, Toronto, Ontario, Canada.
Environment international (Impact Factor: 5.56). 02/2011; 37(2):498-516. DOI: 10.1016/j.envint.2010.10.009
Source: PubMed


Several mechanisms are suspected to underlie adverse birth outcomes among mothers exposed to air pollutants, including inflammation, direct toxic effects on fetuses and the placenta, displacement of the oxygen-hemoglobin dissociation curve, and formation of DNA adducts.
To systematically review the association between air pollutants and birth outcomes of low birth weight (LBW), preterm (PTB) and small for gestational age (SGA) births.
Electronic databases and bibliographies of identified articles were searched for English language studies reporting on birth outcomes. Included studies were assessed for risks of bias in the selection, exposure assessment, confounder adjustment, analyses, outcomes assessment, and attrition. Unadjusted and adjusted estimates from included studies were extracted. Methodological differences between the studies were evaluated.
A total of 41 studies, mostly with a moderate risk of biases due to indirect assessment methods employed, met the eligibility criteria. Exposure to sulphur dioxide was associated with PTB, exposure to fine particulate matter (PM) of ≤2.5 μM was associated with LBW, PTB and SGA births, and exposure to coarse PM of ≤10 μM was associated with SGA births. The evidence for nitrous oxide, nitrogen dioxide, ozone and carbon monoxide was inconclusive.
Reported associations, and lack thereof, between individual air pollutants and birth outcomes have differed across published studies. This heterogeneity and/or absence of association may be due to difficulty in quantifying exposure, method of ascertainment, time of measurement and collinearity between pollutants. Important future research directions include developing improved methods to detect the duration and intensity of exposure, including entire populations, as well as performing well-designed nested studies that ascertain complete outcomes, avoiding residual confounding, and adjusting for residential mobility.

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    • "Exposure to particulate matter (PM) has been associated with cardiorespiratory diseases and adverse birth outcomes, among other endpoints (Pope and Dockery 2006; Shah and Balkhair 2011; Zanobetti et al. 2014). PM is a complex mixture of several components including carbon, metals, organic compounds, ions and biological elements (Pope and Dockery 2006). "
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    ABSTRACT: Background: Observed seasonal differences in particulate matter (PM) associations with human health may be due to composition and toxicity seasonal interactions. Objectives: Assess seasonality in PM composition and in vitro PM pro-inflammatory potential using multiple PM samples. Methods: We collected ninety weekly PM10 and PM2.5 samples during the rainy-warm and dry-cold seasons in five urban areas with different pollution sources. The elements, polycyclic aromatic hydrocarbons (PAHs) and endotoxins characterized in samples were subjected to principal component analysis (PCA). We tested the PM potential to induce TNFα and IL-6 secretion in cultured human monocytes (THP-1) and modeled pro-inflammatory responses using component scores. Results: PM composition varied by size and season. PCA identified two main components that varied by season. Component 1 (C1) grouped combustion-related constituents (e.g. V, benzo(a)pyrene, benzo(a)anthracene). Component 2 (C2) grouped soil-related constituents (e.g. endotoxins, Si, Al). PM from the rainy-warm season was high in C2. PM (especially PM2.5) from the dry-cold season was rich in C1. Higher levels of cytokine production related with PM10 and C2 (rainy-warm season), whereas PM2.5 and C1 were associated with lower levels (dry-cold season). TNFα secretion was higher following exposure to PM with high (versus low) C2 content, but TNFα secretion in response to PM was decreased following exposure to samples containing ≥0.1% of C1-related PAHs, regardless of C2 content. IL-6 results suggest more complex interactions between PM components and particle size. Conclusions: Variations in PM soil and PAHs content underlie seasonal and PM size related patterns in TNFα secretion. These results suggest that the mixture of components in PM explains some seasonal differences in associations between health outcomes and PM in epidemiologic studies.
    Environmental Health Perspectives 09/2015; DOI:10.1289/ehp.1409287 · 7.98 Impact Factor
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    • "Epidemiological studies have suggested adverse effects of outdoor air pollution during pregnancy on maternal and fetal health events such as pre-eclampsia, preterm birth, low birth weight, cardiac congenital malformations and intra-uterine growth retardation (Madsen et al., 2010; Pedersen et al., 2013, 2014; Salam et al., 2005; Shah and Balkhair, 2011; Slama et al., 2007a, 2007b; Vrijheid et al., 2011). This literature has some limitations, in particular in terms of exposure assessment. "
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    ABSTRACT: Studies of air pollution effects during pregnancy generally only consider exposure in the outdoor air at the home address. We aimed to compare exposure models differing in their ability to account for the spatial resolution of pollutants, space-time activity and indoor air pollution levels. We recruited 40 pregnant women in the Grenoble urban area, France, who carried a Global Positioning System (GPS) during up to 3weeks; in a subgroup, indoor measurements of fine particles (PM2.5) were conducted at home (n=9) and personal exposure to nitrogen dioxide (NO2) was assessed using passive air samplers (n=10). Outdoor concentrations of NO2, and PM2.5 were estimated from a dispersion model with a fine spatial resolution. Women spent on average 16h per day at home. Considering only outdoor levels, for estimates at the home address, the correlation between the estimate using the nearest background air monitoring station and the estimate from the dispersion model was high (r=0.93) for PM2.5 and moderate (r=0.67) for NO2. The model incorporating clean GPS data was less correlated with the estimate relying on raw GPS data (r=0.77) than the model ignoring space-time activity (r=0.93). PM2.5 outdoor levels were not to moderately correlated with estimates from the model incorporating indoor measurements and space-time activity (r=-0.10 to 0.47), while NO2 personal levels were not correlated with outdoor levels (r=-0.42 to 0.03). In this urban area, accounting for space-time activity little influenced exposure estimates; in a subgroup of subjects (n=9), incorporating indoor pollution levels seemed to strongly modify them. Copyright © 2015 Elsevier Ltd. All rights reserved.
    Environment international 08/2015; 84:161-173. DOI:10.1016/j.envint.2015.07.021 · 5.56 Impact Factor
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    • "Extensive evidence indicates that prenatal exposure to outdoor air pollution is associated with risk of term low birth weight (Brauer et al., 2008; Fleischer et al., 2014; Ghosh et al., 2013, 2012; Hyder et al., 2014; Padula et al., 2012; Parker et al., 2011; Ponce, 2005; Proietti et al., 2013; Ritz and Wilhelm, 2008; Shah and Balkhair, 2011; Stieb et al., 2012; Wilhelm et al., 2011; Wu et al., 2011). While TLBW contributes to racial–ethnic and socioeconomic health disparities in the United States, air pollution is thought to be an important place-based factor in the complex geography of and susceptibly to TLBW (Jerrett and Finkelstein, 2005; Morello- Frosch and Shenassa, 2006). "
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    ABSTRACT: Air pollution epidemiological studies suggest that elevated exposure to fine particulate matter (PM2.5) is associated with higher prevalence of term low birth weight (TLBW). Previous studies have generally assumed the exposure-response of PM2.5 on TLBW to be the same throughout a large geographical area. Health effects related to PM2.5 exposures, however, may not be uniformly distributed spatially, creating a need for studies that explicitly investigate the spatial distribution of the exposure-response relationship between individual-level exposure to PM2.5 and TLBW. Here, we examine the overall and spatially varying exposure-response relationship between PM2.5 and TLBW throughout urban Los Angeles (LA) County, California. We estimated PM2.5 from a combination of land use regression (LUR), aerosol optical depth from remote sensing, and atmospheric modeling techniques. Exposures were assigned to LA County individual pregnancies identified from electronic birth certificates between the years 1995-2006 (N=1,359,284) provided by the California Department of Public Health. We used a single pollutant multivariate logistic regression model, with multilevel spatially structured and unstructured random effects set in a Bayesian framework to estimate global and spatially varying pollutant effects on TLBW at the census tract level. Overall, increased PM2.5 level was associated with higher prevalence of TLBW county-wide. The spatial random effects model, however, demonstrated that the exposure-response for PM2.5 and TLBW was not uniform across urban LA County. Rather, the magnitude and certainty of the exposure-response estimates for PM2.5 on log odds of TLBW were greatest in the urban core of Central and Southern LA County census tracts. These results suggest that the effects may be spatially patterned, and that simply estimating global pollutant effects obscures disparities suggested by spatial patterns of effects. Studies that incorporate spatial multilevel modeling with random coefficients allow us to identify areas where air pollutant effects on adverse birth outcomes may be most severe and policies to further reduce air pollution might be most effective. Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.
    Environmental Research 07/2015; 142:354-364. DOI:10.1016/j.envres.2015.06.044 · 4.37 Impact Factor
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