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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    • "In addition, the birth height and birth weight of children from Guiyu was lower than children from the reference area, which may indicate that e-waste pollution could have adverse effects on growth, which was consistent with our previous study results (Xu et al., 2015a,b,c). Several studies demonstrated that e-waste may pose a long-term adverse effect on the growth and development of the present generation and future generations (Zhu et al., 2010; Shah and Balkhair, 2011; Kippler et al., 2012; Stieb et al., 2012; Xu et al., 2012; Dadvand et al., 2013). In addition, it is generally known that chest circumference is a predictor of lung function in the healthy population (Rosenthal et al., 1993; Whittaker et al., 2005). "
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    ABSTRACT: This study was to investigate the levels of heavy metals in PM2.5 and in blood, the prevalence of respiratory symptoms and asthma, and the related factors to them. Lead and cadmium in both PM2.5 and blood were significant higher in Guiyu (exposed area) than Haojiang (reference area) (p < 0.05), however, no significant difference was found for chromium and manganese in PM2.5 and in blood. The prevalence of cough, phlegm, dyspnea, and wheeze of children was higher in Guiyu compared to Haojiang (p < 0.05). No significant difference was found for the prevalence of asthma in children between Guiyu and Haojiang. Living in Guiyu was positively associated with blood lead (B = 0.196, p < 0.001), blood cadmium (B = 0.148, p < 0.05) and cough (OR, 2.37; 95% CI, 1.30–4.32; p < 0.01). Blood lead>5 μg/dL was significantly associated with asthma (OR, 9.50; 95% CI, 1.16–77.49). Higher blood chromium and blood manganese were associated with more cough and wheeze, respectively. Our data suggest that living in e-waste exposed area may lead to increased levels of heavy metals, and accelerated prevalence of respiratory symptoms and asthma.
    Full-text · Article · Mar 2016 · Environmental Pollution
    • "Exposure to air pollution has also been associated with a variety of similar adverse health effects in several human body systems, including human reproduction. Air pollution exposures have been found to have hormonal activity and to be negatively associated with early reproductive outcomes such as fertilization and implantation as observed in human IVF (Legro et al., 2010; Perin et al., 2010) and with birth outcomes, such as low birthweight and prematurity (Bobak, 2000; Morello-Frosch et al., 2000; Shah and Balkhair, 2011; Stieb et al., 2012; Dadvand et al., 2013). One birth-based cohort design with retrospectively assessed time to pregnancy found that each increase of 10 mg/m 3 in PM 2.5 levels was associated with reduction in fecundability (month-specific chance of conception) of 22% (95% confidence interval (CI): 6–35%) (Slama et al., 2013). "
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    ABSTRACT: Study question: Is there an association between air pollution exposures and incident infertility? Summary answer: Increased exposure to air pollution is associated with an increased incidence of infertility. What is known already: Exposures to air pollution have been associated with lower conception and fertility rates. However, the impact of pollution on infertility incidence is unknown. Study design, size, duration: Prospective cohort study using data collected from 116 430 female nurses from September 1989 to December 2003 as part of the Nurses' Health Study II cohort. Participants/materials, setting, methods: Infertility was defined by report of attempted conception for ≥12 months without success. Participants were able to report if evaluation was sought and if so, offer multiple clinical indications for infertility. After exclusion, 36 294 members were included in the analysis. Proximity to major roadways and ambient exposures to particulate matter less than 10 microns (PM10), between 2.5 and 10 microns (PM2.5-10), and less than 2.5 microns (PM2.5) were determined for residential addresses for the 36 294 members between the years of 1993 and 2003. Hazard ratios (HR) and 95% confidence intervals (CI) were calculated using multivariable adjusted Cox proportional hazard models with time-varying covariates. Main results and the role of chance: Over 213 416 person-years, there were 2508 incident reports of infertility. Results for overall infertility were inconsistent across exposure types. We observed a small increased risk for those living closer to compared to farther from a major road, multivariable adjusted HR = 1.11 (CI: 1.02-1.20). This was consistent for those reporting primary or secondary infertility. For women living closer to compared to farther from a major road, for primary infertility HR = 1.05 (CI: 0.94-1.17), while for secondary infertility HR = 1.21 (CI: 1.07-1.36). In addition, the HR for every 10 µg/m(3) increase in cumulative PM2.5-10 among women with primary infertility was 1.10 (CI: 0.96-1.27), and similarly was 1.10 (CI: 0.94-1.28) for those with secondary infertility. Limitations, reasons for caution: Within the 2 year window of infertility diagnosis, we do not have the exact date of diagnosis or the exact timing of the start of attempting conception. As infertility status and subtypes of infertility were prospectively collected biennially, we were unable to tightly examine the timing of exposures on incidence of infertility. In terms of exposure quantification, we used ambient air pollution exposures as a proxy for personal exposures, potentially leading to exposure misclassification. However, several studies suggest that ambient measurements are an acceptable surrogate for individual level exposures in most populations. Wider implications of the findings: We observed an association between all size fractions of PM exposure, as well as traffic-related air pollution, and incidence of infertility. Of note, the strongest association was observed between cumulative average exposures over the course of follow-up and the risk of infertility, suggesting that chronic exposures may be of greater importance than short-term exposures. Study funding/competing interests: The work for this paper was supported by the following: S.M.: Reproductive Scientist Development Program HD000849, and the Building Interdisciplinary Research Careers in Women's Health HD043444, the Boston University CTSI 1UL1TR001430, and a research grant from the Boston University Department of Obstetrics and Gynecology, S.A.M.: R01HD57210 from the National Institute of Child Health and Human Development and the Massachusetts Institute of Technology Center for Environmental Health Sciences Translational Pilot Project Program, R01CA50385 from the National Cancer Institute, J.E.H. and F.L.: 5R01ES017017 from the National Institute for Environmental Health Sciences, 5 P42 ES007381 from the National Institute of Environmental Health at the National Institute of Health. L.V.F.: T32HD060454 in reproductive, perinatal, and pediatric epidemiology from the Eunice Kennedy Shriver National Institute of Child Health and Human Development. The Nurses' Health Study II is additionally supported by infrastructure grant UM1CA176726 from the National Cancer Institute, NIH, U.S. Department of Health and Human Services. The authors have no actual or potential competing financial interests to disclose.
    No preview · Article · Jan 2016 · Human Reproduction
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    • "Among all hypothesized risk factors of adverse pregnancy outcomes, air pollution ought to be considered a weak risk factor. This difference would increase " noise " and decrease signal-to-ratio for the effect from air pollution, which could be a potential reason for the reported small associations (Shah and Balkhair, 2011). In general, null or slightly inverse associations for PTB were observed for both NO 2 and SO 2 in the current study. "
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    ABSTRACT: Importance: Although studies in western countries suggest that ambient air pollution is positively associated with adverse pregnancy outcomes, the upper levels of pollutant exposures have been relatively low, thus eroding confidence in the conclusions. Meanwhile, in Asia, where upper levels of exposure have been greater, there have been limited studies of the association between air pollution and adverse pregnancy outcomes. Objective: The primary objective was to evaluate whether high levels of pollution, including particulate matter pollution with a mass median aerodynamic diameter of less than 2.5μm (PM2.5) and 10μm (PM10), sulfur dioxide (SO2), nitrogen dioxide (NO2), ozone (O3), and carbon monoxide (CO) are related to increased occurrence of preterm birth (PTB). Methods: We conducted a population-based study in Wuhan, China in a cohort of 95,911 live births during a two-year period from 2011 to 2013. The exposure was estimated based on daily mean concentrations of pollutants estimated using the pollutants' measurements from the nine closest monitors. Logistic regressions were performed to determine the relationships between exposure to each of the pollutants during different pregnancy periods and PTB while controlling for key covariates. Results: We found 3% (OR=1.03; 95% CI: 1.02, 1.05), 2% (OR=1.02; 95% CI: 1.02, 1.03), 15% (OR=1.15; 95% CI: 1.11, 1.19), and 5% (OR=1.05; 95% CI: 1.02, 1.07) increases in risk of PTB with each 5-μg/m(3) increase in PM2.5 and PM10 concentrations, 100-μg/m(3) increase in CO concentrations, and 10-μg/m(3) increase in O3 concentrations, respectively. There was negligible evidence for associations for SO2 and NO2. The effects from two-pollutant models were similar to the estimated effects from single pollutant models. No critical exposure windows were identified consistently: the strongest effect for PTB was found in the second trimester for PM2.5, PM10, and CO, but for SO2 it was in the first trimester, second month, and third month. For NO2 it was in the first trimester and second month, and for O3, the third trimester. Conclusion: Findings reveal an association between air pollutants and PTB. However, more toxicological studies and prospective cohort studies with improved exposure assessments are needed to establish causality related to specific pollutants.
    Full-text · Article · Nov 2015 · International journal of hygiene and environmental health
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