The association between fine particulate matter exposure during pregnancy and preterm birth: a meta-analysis

Maternal PM2.5 exposure triggers preterm birth: a cross-sectional study in Wuhan, China

Background

Most of the studies regarding air pollution and preterm birth (PTB) in highly polluted areas have estimated the exposure level based on fixed-site monitoring. However, exposure assessment methods relying on monitors have the potential to cause exposure misclassification due to a lack of spatial variation. In this study, we utilized a land use regression (LUR) model to assess individual exposure, and explored the association between PM_2.5 exposure during each time window and the risk of preterm birth in Wuhan city, China.

Methods

Information on 2101 singleton births, which were ≥ 20 weeks of gestation and born between November 1, 2013 and May 31, 2014; between January 1, 2015 and August 31, 2015, was obtained from the Obstetrics Department in one 3A hospital in Wuhan. Air quality index (AQI) data were accessed from the Wuhan Environmental Protection Bureau website. Individual exposure during pregnancy was assessed by LUR models and Kriging interpolation. Logistic regression analyses were conducted to determine the association between women exposure to PM_2.5 and the risk of different subtypes of PTB.

Results

During the study period, the average individual exposure concentration of PM_2.5 during the entire pregnancy was 84.54 μg/m³. A 10 μg/m³ increase of PM_2.5 exposure in the first trimester (OR: 1.169; 95% CI: 1.077, 1.262), the second trimester (OR: 1.056; 95% CI: 1.015, 1.097), the third trimester (OR: 1.052; 95% CI: 1.002, 1.101), and the entire pregnancy (OR: 1.263; 95% CI: 1.158, 1.368) was significantly associated with an increased risk of PTB. For the PTB subgroup, the hazard of PM_2.5 exposure during pregnancy was stronger for very preterm births (VPTB) than moderate preterm births (MPTB). The first trimester was the most susceptible exposure window. Moreover, women who had less than 9 years of education or who conceived during the cold season tended to be more susceptible to the PM_2.5 exposure during pregnancy.

Conclusions

Maternal exposure to PM_2.5 increased the risk of PTB, and this risk was stronger for VPTB than for MPTB, especially during the first trimester.

Time series analysis of total and direct associations between high temperatures and preterm births in Detroit, Michigan

OBJECTIVES

Preterm births (PTBs) represent significant health risks, and several studies have found associations between high outdoor temperatures and PTB. We estimated both the total and natural direct effects (independent of particulate matter, ozone and nitrogen dioxide air pollutants) of the prior 2-day mean apparent temperature (AT) on PTB. We evaluated effect modification by maternal age, race, education, smoking status and prenatal care.

DESIGN AND SETTING

We obtained birth records and meteorological data for the Detroit, Michigan, USA area, for the warm months (May to September), 1991 to 2001. We used a time series Poisson regression with splines of AT, wind speed, solar radiation and citywide average precipitation to estimate total effects. To accommodate multiple mediators and exposure-mediator interactions, AT inverse odds weights, predicted by meteorological and air pollutant covariates, were added in a subsequent model to estimate direct effects.

RESULTS

At 24.9°C relative to 18.6°C, 10.6% (95% CI: 3.8% to 17.2%) of PTBs were attributable to the total effects of AT, and 10.4% (95% CI: 2.2% to 17.5%) to direct effects. Relative excess risks of interaction indicated that the risk of PTB with increasing temperature above 18.6°C was significantly lower among black mothers and higher among mothers less than 19, older than 30, with late or no prenatal care and who smoked.

CONCLUSION

This additional evidence of a direct association between high temperature and PTB may motivate public health interventions to reduce extreme heat exposures among pregnant women, particularly among those who may have enhanced vulnerability.

Associations of ambient temperature exposure during pregnancy with the risk of miscarriage and the modification effects of greenness in Guangdong, China

Miscarriage is one of the commonest complications of pregnancy. Although previous studies suggested that environmental factors were important causes of miscarriage, evidence is still inadequate. Here, we examined the association of maternal exposure to temperature with the risk of miscarriage and further assessed the modifying effects of surrounding residential greenness. A case-control study was conducted at a large hospital in Guangzhou, China. All participants' information was extracted from hospital records. An inverse distance weighted method was used to estimate the temperature exposure at each residential address, where the greenness was measured by Normalized Difference Vegetation Index (NDVI). A logistic regression model was applied to estimate the association of temperature exposure with the risk of miscarriage. A total of 2044 cases of miscarriage and 2285 controls were included in the present study. We observed a generally non-linear positive relationship between temperature exposure and the risk of miscarriage. More pronounced effects of high temperatures vs. low temperatures were found during the two months prior to hospitalization than in other periods. The odds ratio (OR) of 29.4 °C (95th centile) compared with 15 °C during the first month prior to hospitalization was 1.480 (95% CI: 1.021-2.145). Smaller effects of temperatures were seen on the risk of miscarriage among participants with moderately great surrounding greenness compared with those with less greenness. We concluded that maternal exposure to moderately high temperature during pregnancy may increase the risk of miscarriage, but the modifying effects of greenness on these associations need to be further tested in future studies.

Effects of prenatal exposure to air particulate matter on the risk of preterm birth and roles of maternal and cord blood LINE-1 methylation: A birth cohort study in Guangzhou, China

BACKGROUND

Epidemiological studies have found that increased risk of preterm birth (PTB) is associated with higher prenatal exposure to PM₁₀ and PM_2.5, but few studies have been conducted to assess the impacts of extremely fine particulate matter (PM₁) which may have more toxic effects than other types of ambient particulate air pollution (PM). Several studies have separately investigated the associations between DNA methylation and PTB risk and PM. Maternal LINE-1 methylation level negatively correlated with prenatal exposure to PM and risk of PTB. A comprehensive picture is lacking regarding the associations between prenatal exposure to PM, LINE-1 methylation, and risk of PTB.

OBJECTIVES

This study aimed to estimate the effects of exposure to ambient PM (PM₁₀, PM_2.5, and PM₁) of different sizes during pregnancy on risk of PTB, identify susceptible exposure windows, and illustrate the roles of LINE-1 methylation in the associations between PM and PTB risk.

METHODS

The Birth Cohort Study on Prenatal Environments and Offspring Health (PEOH) has been ongoing since 2016 in Guangzhou, China. A total of 4928 pregnant women were recruited during early pregnancy, and 4278 (86.8%) were successfully followed-up. Each individual weekly exposure to PM₁₀ and PM_2.5 from 3 months before pregnancy to childbirth was assessed using a spatiotemporal land use regression model, and the weekly PM₁ exposure was estimated by employing a generalized additive model. Maternal and cord blood LINE-1 methylation levels (%5mC) were tested using bisulfite-PCR pyrosequencing. A distributed lag nonlinear model incorporated with a Cox proportional hazard model was applied to assess the effect of weekly-specific maternal PM exposure on PTB risk, and a multiple-linear regression model was employed to investigate the associations between PM exposure and LINE-1 methylation levels of maternal and cord bloods. We also assessed the associations between LINE-1 methylation levels and PTB risk by using a logistic regression model.

RESULTS

The risk of PTB was positively associated with PM_2.5 and PM₁ concentrations during the 12th to 20th gestational weeks, and the strongest association was in the fourth quartile (Q₄) versus the first quartile (Q₁) and observed during the 16th gestational week (PM_2.5: harzard ratio [HR] = 1.18, 95%CI: 1.04-1.35, IQR = 11.94 μg/m³. PM₁: HR = 1.20, 95%CI: 1.03-1.39, IQR = 11.36 μg/m³). We observed significantly negative associations of PM₁₀(β = -0.51%5mC per 10 μg/m³, P = 0.014), PM_2.5 (β = -0.66%5mC per 10 μg/m³, P = 0.032) and PM₁ (β = -0.67%5mC per 10 μg/m³, P = 0.032) concentrations with cord blood LINE-1 methylation levels, and a negative association between PM₁ concentration and maternal LINE-1 methylation level (β = -0.86%5mC per 10 μg/m³, P = 0.034).

CONCLUSION

Higher prenatal exposure to PM₁ and PM_2.5 during the 12th to 20th gestational weeks was associated with increased risk of PTB. Maternal and fetal LINE-1 methylation alternation might be an underlying mechanism of PM that increasing the risk of PTB.

Synergistic effects of prenatal exposure to fine particulate matter (PM2.5) and ozone (O3) on the risk of preterm birth: A population-based cohort study

BACKGROUND

There is some evidence that prenatal exposure to low-level air pollution increases the risk of preterm birth (PTB), but little is known about synergistic effects of different pollutants.

OBJECTIVES

We assessed the independent and joint effects of prenatal exposure to air pollution during the entire duration of pregnancy.

METHODS

The study population consisted of the 2568 members of the Espoo Cohort Study, born between 1984 and 1990, and living in the City of Espoo, Finland. We assessed individual-level prenatal exposure to ambient air pollutants of interest at all the residential addresses from conception to birth. The pollutant concentrations were estimated both by using regional-to-city-scale dispersion modelling and land-use regression-based method. We applied Poisson regression analysis to estimate the adjusted risk ratios (RRs) with their 95% confidence intervals (CI) by comparing the risk of PTB among babies with the highest quartile (Q₄) of exposure during the entire duration of pregnancy with those with the lower exposure quartiles (Q₁-Q₃). We adjusted for season of birth, maternal age, sex of the baby, family's socioeconomic status, maternal smoking during pregnancy, maternal exposure to environmental tobacco smoke during pregnancy, single parenthood, and exposure to other air pollutants (only in multi-pollutant models) in the analysis.

RESULTS

In a multi-pollutant model estimating the effects of exposure during entire pregnancy, the adjusted RR was 1.37 (95% CI: 0.85, 2.23) for PM_2.5 and 1.64 (95% CI: 1.15, 2.35) for O₃. The joint effect of PM_2.5 and O₃ was substantially higher, an adjusted RR of 3.63 (95% CI: 2.16, 6.10), than what would have been expected from their independent effects (0.99 for PM_2.5 and 1.34 for O₃). The relative risk due to interaction (RERI) was 2.30 (95% CI: 0.95, 4.57).

DISCUSSION

Our results strengthen the evidence that exposure to fairly low-level air pollution during pregnancy increases the risk of PTB. We provide novel observations indicating that individual air pollutants such as PM_2.5 and O₃ may act synergistically potentiating each other's adverse effects.

Ambient air pollution and adverse birth outcomes: a systematic review and meta-analysis

Several reviews have assessed the relationship between exposure to ambient air pollution and adverse birth outcomes during pregnancy, but the results remain controversial. The objective of this study was to assess this correlation quantitatively and to explore sources of heterogeneity. We included all published case-control or cohort studies that evaluated the correlation between ambient air pollution and low birth weight (LBW), preterm birth (PTB), and small for gestational age (SGA). Analytical methods and inclusion criteria were provided on the PROSPERO website (CRD42018085816). We evaluated pooled effects and heterogeneity. Subgroup analyses (grouped by exposure period, study settings, study design, exposure types, data source, Newcastle-Ottawa quality score (NOS), and adjustment for smoking or meteorological factors) were also conducted and publication bias was examined. The risk of bias in systematic reviews (ROBIS) tool was used to evaluate the overall risk of bias in this review. Forty studies met the inclusion criteria. We observed pooled odds ratios (ORs) of 1.03-1.21 for LBW and 0.97-1.06 for PTB when mothers were exposed to CO, NO₂, NO_x, O₃, PM_2.5, PM₁₀, or SO₂ throughout their pregnancy. For SGA, the pooled estimate was 1.02 in relation to NO₂ concentrations. Subgroup analysis and sensitivity analysis decreased the heterogeneity to some extent, such as the subgroups of continuous measures (OR=0.98 (0.97-0.99), I²=0.0%) and NOS>7 (OR=0.98 (0.97-0.99), I²=0.0%) in evaluating the association between PTB and NO₂. This review was completed with a low risk of bias. High concentrations of air pollution were significantly related to the higher risk of adverse birth outcomes. However, the sources of heterogeneity among studies should be further explored.

Developmental programming of obesity by maternal exposure to concentrated ambient PM2.5 is maternally transmitted into the third generation in a mouse model

BACKGROUND

Obesity is an uncontrolled global epidemic and one of the leading global public health challenges. Maternal exposure to ambient fine particulate matter (PM2.5) may adversely program offspring's adiposity, suggesting a specialized role of PM2.5 pollution in the global obesity epidemic. However, the vulnerable window for this adverse programming and how it is cross-generationally transmitted have not been determined. Therefore, in the present study, female C57Bl/6 J mice were exposed to filtered air (FA) or concentrated ambient PM2.5 (CAP) during different periods, and the development and adulthood adiposity of their four-generational offspring were assessed.

RESULTS

Our data show that the pre-conceptional but not gestational exposure to CAP was sufficient to cause male but not female offspring's low birth weight, accelerated postnatal weight gain, and increased adulthood adiposity. These adverse developmental traits were transmitted into the F2 offspring born by the female but not male F1 offspring of CAP-exposed dams. In contrast, no adverse development was noted in the F3 offspring.

CONCLUSIONS

The present study identified a pre-conceptional window for the adverse programming of adiposity by maternal exposure to PM2.5, and showed that it was maternally transmitted into the third generation. These data not only call special attention to the protection of women from exposure to PM2.5, but also may facilitate the development of intervention to prevent this adverse programming.

The associations of air pollution exposure during pregnancy with fetal growth and anthropometric measurements at birth: a systematic review and meta-analysis

Fetal growth has been demonstrated to be an important predictor of perinatal and postnatal health. Although the effects of maternal exposure to air pollution during pregnancy on fetal growth have been investigated using ultrasound in many previous studies, the results were inconsistent and disputable. We aimed to qualitatively and quantitatively investigate the associations of air pollution exposure during different periods of pregnancy with fetal growth and anthropometric measurements at birth. We searched for all studies investigating the associations of air pollution exposure during pregnancy with fetal growth and birth anthropometric measurements in English and Chinese databases published before July 31, 2017. A random-effects model was employed in the meta-analysis to estimate the pooled effects of each 10 μg/m³ increment in air pollutant exposure. The ACROBAT-NRSI tool was applied to assess the quality of each included study, and the GRADE tool was employed to assess the overall quality of the meta-analysis. Maternal PM_2.5 exposure (10 μg/m³) during the entire pregnancy was negatively associated with head circumference at birth (β = - 0.30 cm, 95% CI - 0.49, - 0.10), and NO₂ exposure during the entire pregnancy was significantly linked to shorter length at birth (β = - 0.03 cm, 95% CI - 0.05, - 0.02). Maternal exposure to higher NO₂ and PM_2.5 during pregnancy may impair neonatal head circumference and length development, respectively. More studies are needed to confirm the effects of NO₂ and PM_2.5 and to identify the sources and major toxic components of PMs.

Maternal fine particulate matter (PM2.5) exposure and adverse birth outcomes: an updated systematic review based on cohort studies

Exposure to ambient air pollutants during pregnancy may be associated with numerous side health effects and adverse birth outcomes. Growing numbers of studies have explored a possible linkage between prenatal exposure to PM_2.5 (particulate matter with aerodynamic diameter ≤ 2.5 μm) and impacts on fetal development. We aimed to conduct a systematic review based on published cohort studies to summarize evidence regarding the association between maternal PM_2.5 exposure and birth outcomes, including birth weight, low birth weight (LBW), preterm birth (PTB), and small for gestational age (SGA). Eligible studies meeting the following criterion were selected: PM_2.5 exposure during pregnancy and live birth singletons, certain presentation of sample sizes, and quantitative evaluation of the associations between exposure and outcomes. Among the 42 selected studies, 23 evaluated the impact of prenatal PM_2.5 exposure on birth weight of infants while 12 of them provided a significantly negative association for exposure and birth weight. Twenty-one studies aimed to identify the possible relationship between maternal exposure and LBW and 8 studies proved significant associations. Among 18 studies that explored the correlation between prenatal exposure and PTB, 9 reached a consistent conclusion that gestational exposure would add to the risk of PTB. Nine studies assessed the impact of PM_2.5 on SGA and 5 of them demonstrated a significant effect. So far, linkages between maternal PM_2.5 exposure during varied gestational stages and multiple adverse birth outcomes have been observed in many studies. A summary of them will be meaningful for further research on maternal exposure and adverse birth outcomes.

Towards a fuller assessment of benefits to children's health of reducing air pollution and mitigating climate change due to fossil fuel combustion

BACKGROUND

Fossil fuel combustion by-products, including particulate matter (PM_2.5), polycyclic aromatic hydrocarbons (PAH), nitrogen dioxide (NO₂) and carbon dioxide (CO₂), are a significant threat to children's health and equality. Various policies to reduce emissions have been implemented to reduce air pollution and mitigate climate change, with sizeable estimated health and economic benefits. However, only a few adverse outcomes in children have been considered, resulting in an undercounting of the benefits to this vulnerable population.

OBJECTIVES

Our goal was to expand the suite of child health outcomes addressed by programs to assess health and economic benefits, such as the Environmental Protection Agency (EPA) Benefits Mapping and Analysis Program (BenMAP), by identifying concentration-response (C-R) functions for six outcomes related to PM_2.5, NO₂, PAH, and/or PM₁₀: preterm birth (PTB), low birthweight (LBW), autism, attention deficit hyperactivity disorder, IQ reduction, and the development of childhood asthma.

METHODS

We conducted a systematic review of the literature published between January 1, 2000 and April 30, 2018 to identify relevant peer-reviewed case-control and cohort studies and meta-analyses. In some cases meta-analyses were available that provided reliable C-R functions and we assessed their consistency with subsequent studies. Otherwise, we reviewed all eligible studies published between our search dates.

RESULTS

For each pollutant and health outcome, we present the characteristics of each selected study. We distinguish between C-R functions for endpoints having a causal or likely relationship (PTB, LBW, autism, asthma development) with the pollutants for incorporation into primary analyses and endpoints having a suggestive causal relationship with the pollutants (IQ reduction, ADHD) for secondary analyses.

CONCLUSION

We have identified C-R functions for a number of adverse health outcomes in children associated with air pollutants largely from fossil fuel combustion. Their incorporation into expanded assessments of health benefits of clean air and climate mitigation policies will provide an important incentive for preventive action.

Premature births in Spain: Measuring the impact of air pollution using time series analyses

BACKGROUND

Premature birth (<37 weeks of gestation) is the principal indicator of neonatal death during the first month of life and the second cause of death of children under age five. There are 15 million premature births (PTB) worldwide. Air pollution in cities, primarily the result of urban traffic, greatly impacts PTBs, though there are few studies carried out on this topic at the country level. The objective of this study is to quantify the relative risks (RR) and the population attributable risk (PAR) of concentrations of contaminants on PTBs in Spain, and to analyze the most susceptible trimesters.

METHODS

For each province average weekly PTBs were calculated (ICD-10: P07.2-P07.3) during the period 2001-2009 as well as weekly average concentrations of PM₁₀, NO₂ and O₃. Estimations were made of RR and PAR using generalized linear models with link Poisson, controlling for the trend, seasonality, the autoregressive nature of the series and the influence of temperature in periods of heat and/or cold waves. A meta-analysis was carried out to estimate RR and PAR at the global level based on the RR obtained for each of the provinces.

RESULTS

For all of Spain, the global RR of PTB due to the impact of PM₁₀ was 1.071 (1.049, 1.093) and 1.150 (1.084, 1.220) for NO₂, with no detected association for O₃. Therefore, with decreases of 10 μg/m³ in the concentrations of PM₁₀ and NO₂, around 12.5% and 4.5% of PTBs could have been avoided respectively.

CONCLUSIONS

Around 1.35% of PTBs that occurred in Spain during the study period can be attributed to air pollution. The adoption of structural measures to reduce these air pollutants should result in a decrease in the number of PTBs in Spain.

Prenatal exposure to ambient fine particulate matter induces dysregulations of lipid metabolism in adipose tissue in male offspring

Prenatal exposure to ambient fine particles (diameter < 0.25 μm, PM_2.5) has been found to be associated with abnormal growth and development in offspring. However, the effects of PM_2.5 on the lipid metabolism of adipose tissue in offspring are unclear. In the present study, we established a mouse model of prenatal exposure to PM_2.5 by intratracheal instillation to pregnant C57BL/6 female mice with PM_2.5 suspension or normal saline. We found that prenatal exposure to PM_2.5 of a mouse model reduced body weight in adult male offspring after 6 weeks old. Histological analysis showed that the adipocyte size was significantly reduced in epididymal adipose tissue (eWAT) in male offspring, but not in brown adipose tissue. The expression levels of genes related to fatty acid synthesis (ACC1, ACSL1) and oxidation (PPARα) in eWAT were also significantly decreased. In addition, downregulation of pro-inflammatory cytokines (TNFα, IL-1β, IL-6) was also observed. Lipidomics analysis of eWAT demonstrated that prenatal exposure of PM_2.5 reduced lysophosphatidylcholines (LPC), phosphatidylcholines (PC), phosphatidylethanolamines (PE), sphingomyelins (SM), and ceramides (Cer), indicating that metabolic pathways, including SM-Cer signaling and glycerophospholipids remodeling, were disrupted. In summary, prenatal exposure to PM_2.5 was associated with the dysregulations in lipid metabolism of eWAT and pro-inflammatory response in male offspring.

Preterm birth and economic benefits of reduced maternal exposure to fine particulate matter

Preterm birth (PTB) is a predictor of infant mortality and later-life morbidity. Despite recent declines, PTB rates remain high in the United States. Growing research suggests a possible relationship between a mother's exposure to common air pollutants, including fine particulate matter (PM_2.5), and PTB of her baby. Many policy actions to reduce exposure to common air pollutants require benefit-cost analysis (BCA), and it's possible that PTB will need to be included in BCA in the future. However, an estimate of the willingness to pay (WTP) to avoid PTB risk is not available, and a comprehensive alternative valuation of the health benefits of reducing pollutant-related PTB currently does not exist. This paper demonstrates an approach to assess potential economic benefits of reducing PTB resulting from environmental exposures when an estimate of WTP to avoid PTB risk is unavailable. We utilized a recent meta-analysis, county-level air quality data and county-level PTB prevalence data to estimate the potential health and economic benefits of a reduction in air pollution-related PTB, with PM_2.5 as our case study pollutant. Using this method, a simulated nationwide 10% decrease from 2008 PM_2.5 levels resulted in an estimated reduction of 5016 PTBs and benefits of at least $339 million, potentially reaching over one billion dollars when considering later-life effects of PTB.

Acute and chronic effects of ambient fine particulate matter on preterm births in Beijing, China: A time-series model

Accumulating evidence suggests that short- and long-term exposure to ambient fine particulate matter ≤ 2.5 μm (PM_2.5) during pregnancy is associated with preterm births, yet the results are inconsistent, and the shape of the exposure-response curve is unclear, partially due to the limited studies conducted in areas with high air pollution. Our study evaluated the association between ambient PM_2.5 concentration and preterm births in Beijing, China. Daily preterm birth data were collected from a hospital in Beijing during 2006 to 2013; a time-series of daily PM_2.5 concentrations during the same period is assembled with measured data at three monitoring sites in Beijing. An extension of the Poisson regression and a time-series model were applied to simultaneously estimate the acute and chronic effects of exposure to PM_2.5, with mutual adjustment for short- and long-term exposure as well as for confounders. During the study period, the PM_2.5 concentration was 70.4 ± 60.6 μg/m³ and was found to be associated with an increased risk of preterm birth. In the study cohort, a 0.52% (95% confidence interval, CI: 0.09%, 0.96%) and 3.13% (95%CI: 1.92%, 4.35%) increase in preterm births was estimated for each 10-μg/m³ increase in short- and long-term exposure, respectively. This association was significantly modified by season (p < 0.05). With mutual adjustments for short- and long-term exposure, a more robust association (3.16%, 95% CI: 1.95%, 4.39%; per 10-μg/m³ increment in PM_2.5) was observed for chronic effects. The exposure-response relationships for both short- and long-term exposure were linear, without a threshold, over the relatively low exposure range and flattened out at higher concentration levels. The maximum effect for long-term exposure to PM_2.5 (33.6%) was much greater than that for short-term exposure (19.9%). These findings indicate that air quality improvements over a long period could yield significant health benefits.

Air pollution in the week prior to delivery and preterm birth in 24 Canadian cities: a time to event analysis

BACKGROUND

Numerous studies have examined the association between air pollution and preterm birth (< 37 weeks gestation) but findings have been inconsistent. These associations may be more difficult to detect than associations with other adverse birth outcomes because of the different duration of exposure in preterm vs. term births, and the existence of seasonal cycles in incidence of preterm birth.

METHODS

We analyzed data pertaining to 1,001,700 singleton births occurring between 1999 and 2008 in 24 Canadian cities where daily air pollution data were available from government monitoring sites. In the first stage, data were analyzed in each city employing Cox proportional hazards models using gestational age in days as the time scale, obtaining city-specific hazard ratios (HRs) with their 95% confidence intervals (CIs) expressed per interquartile range (IQR) of each air pollutant. Effects were examined using distributed lag functions for lags of 0-6 days prior to delivery, as well as cumulative lags from two to six days. We accounted for the potential nonlinear effect of daily mean ambient temperature using a cubic B-spline with three internal knots. In the second stage, we pooled the estimated city-specific hazard ratios using a random effects model.

RESULTS

Pooled estimates across 24 cities indicated that an IQR increase in ozone (O3, 13.3 ppb) 0-3 days prior to delivery was associated with a hazard ratio of 1.036 (95% CI 1.005, 1.067) for preterm birth, adjusting for infant sex, maternal age, marital status and country of birth, neighbourhood socioeconomic status (SES) and visible minority, temperature, year and season of birth, and a natural spline function of day of year. There was some evidence of effect modification by gestational age and season. Associations with carbon monoxide, nitrogen dioxide, particulate matter, and sulphur dioxide were inconsistent.

CONCLUSIONS

We observed associations between daily O3 in the week before delivery and preterm birth in an analysis of approximately 1 million births in 24 Canadian cities between 1999 and 2008. Our analysis is one of a limited number which have examined these short term associations employing Cox proportional hazards models to account for the different exposure durations of preterm vs. term births.

Acute effects of air pollutants on adverse birth outcomes in Changsha, China: A population data with time-series analysis from 2015 to 2017

Evidence for the acute effects of air pollutants on adverse birth outcomes is not yet conclusive. Furthermore, there are no investigations relating to the association between air pollutants and macrosomia. The aim of this study was to determine the relationship between air pollutants and low birth weight, preterm birth, and macrosomia in Changsha. Time-series analysis, using a generalized additive model was applied. Data about the adverse birth outcomes was collected from 78 midwifery institutions. Air pollution data including SO2, NO2, particulate matter <10 μm in diameter (PM10), particulate matter <2.5 μm in diameter (PM2.5), O3, CO, and climate data were respectively collected from the Changsha Environmental Protection Agency and the Changsha Meteorological Bureau from January 2015 to December 2017. During the study period, there were 344,880 live births to be studied. In a single pollutant model, for every increase of 10 μg/m in PM10 and PM2.5, low birth weight increased by 0.12% (95% confidence interval [CI]: 0.01-0.23%) at a lag 06 and 0.44% (95% CI: 0.35-0.53%) at a lag 3, respectively. Preterm birth increased most by 1.60% (95% CI: 1.41-1.80%) at a lag 2 for every increase of 10 μg/m in SO2. The highest increases in macrosomia associated with a 10 μg/m increase in air pollutant were 3.53% (95% CI: 3.41-3.64%) for NO2 at lag 0, 3.33% (95% CI: 3.05-3.60%) for SO2 at lag03. Multi-pollutant models showed that only PM10 increased the low birth weight and preterm birth risk effect by 3.91% (95% CI: 3.67-4.12%) and 0.25% (95% CI: 0.14-0.37%). NO2 increased macrosomia risk by 4.14% (95% CI: 3.97-4.31%) with a 10 μg/m increase. There was no association observed between the air pollutants O3 and CO and adverse birth outcomes. Pregnant women should also take steps to limit their exposure to high levels of air pollutants during the final weeks of pregnancy.

Exposure to ambient PM2.5 during pregnancy and preterm birth in metropolitan areas of the state of Georgia

A number of studies has pointed to air pollution as an additional factor that could be associated with preterm birth. We assessed in this study the association between exposure to PM_2.5 in ambient air during pregnancy and preterm birth in metropolitan areas of the state of Georgia, where the rate of preterm birth has been among the highest in the nation over the years. Birth data were obtained from the National Center for Health Statistics natality dataset. The study population consisted of 53,094 singleton live births between January 1 and December 31, 2004 in nine metropolitan counties of Georgia. Preterm birth was defined as birth, which occurs before 37 weeks of gestation. County-level daily air quality index (AQI) data obtained from the US Environmental Protection Agency (EPA) was used to estimate individual exposure levels of PM_2.5 for each study participant based on the county of residence for the duration of the pregnancy. A multivariate logistic regression analysis was conducted to assess the association, adjusting for potential confounders. Of the infants whose mothers resided in the nine metropolitan counties of Georgia, 4543 (8.6%) were born preterm. A higher rate of preterm birth (9.8%) was observed in infants whose mothers were exposed to ambient PM_2.5 with AQI values > 50 than the ones with AQI ≤ 50 (EPA standard for good air quality conditions). Mothers with exposure to PM_2.5 at average AQI values greater than 50 during the entire pregnancy were at increased risk of preterm birth (odds ratio 1.15; 95% CI 1.07, 1.25), after adjusting for sex of infant, mother's age, race/ethnicity, education, marital status, prenatal care, cigarette smoking, alcohol consumption, and season of conception. The study provides more evidence on the role of PM_2.5 in preterm birth. Reducing exposure to ambient particulate matter, especially in urban areas, for pregnant women would be necessary to improve the health of infants.

Investigation of association between environmental and socioeconomic factors and preterm birth in California

BACKGROUND

Preterm birth (PTB),2 defined as birth at gestational age <37 weeks, is a major public health concern. Infants born prematurely, comprising of about 10% of the US newborns, have elevated risks of neonatal mortality and a wide array of health problems. Although numerous clinical, genetic, environmental and socioeconomic factors have been implicated in PTB, very few studies investigate the impacts of multiple pollutants and social factors on PTB using large scale datasets.

OBJECTIVES

To evaluate association between environmental and socioeconomic factors and PTB in California.

METHODS

We linked the birth cohort file maintained by the California Office of Statewide Health Planning and Development from 2009 to 2012 years across 1.8 million births and the CalEnviroScreen 3.0 dataset from California Communities Environmental Health Screening Tool at the census tract level for 56 California counties. CalEnviroScreen contains 7 exposure and 5 environmental effects variables that constitute the Pollution Burden variable, and 5 socioeconomic variables. We evaluated relationships between environmental exposures and the risk of PTB using hierarchical clustering analyses and GIS-based visualization. We also used logistic regression to evaluate the relationship between specific pollutant and exposure indicators and PTB, accounted for socio-demographic determinants such as maternal race/ethnicity, maternal age, maternal education and payment of delivery costs.

RESULTS

There exists geographic variability in PTB for groups of counties with similar environmental and social exposure profiles. We found an association between Pollution Burden, particulate matter ≤2.5 μm (PM2.5), and Drinking Water Scores and PTB (adjusted odds ratios were 1.03 (95% Confidence Interval (CI): 1.01, 1.04), 1.03 (95% CI: 1.02,1.04), and 1.04 (95% CI: 1.03,1.05), respectively). Additional findings suggest that certain drinking water contaminants such as arsenic and nitrate are associated with PTB in California.

CONCLUSIONS

CalEnviroScreen data combined with birth records offer great opportunity for revealing novel exposures and evaluating cumulative exposures related to PTB by providing useful environmental and social information. Certain drinking water contaminants such as arsenic and nitrate are potentially associated with PTB in California and should be investigated further. Small association signals may involve sizeable population impacts.

Ambient air pollution and pregnancy outcomes: A comprehensive review and identification of environmental public health challenges

There is a growing number of studies on the association between ambient air pollution and adverse pregnancy outcomes, but their results have been inconsistent. Consequently, a comprehensive review of this research area is needed. There was a wide variability in studied pregnancy outcomes, observed gestational windows of exposure, observed ambient air pollutants, applied exposure assessment methods and statistical analysis methods Gestational duration, preterm birth, (low) birth weight, and small for gestational age/intrauterine growth restriction were most commonly investigated pregnancy outcomes. Gestational windows of exposure typically included were whole pregnancy period, 1st, 2nd, 3rd trimester, first and last gestational months. Preterm birth was the outcome most extensively studied across various gestational windows, especially at the beginning and at the end of pregnancy. Particulate matter, nitrogen dioxide, ozone, and carbon monoxide were the most commonly used markers of ambient air pollution. Continuous monitoring data were frequently combined with spatially more precisely modelled estimates of exposure. Exposure to particulate matter and ozone over the entire pregnancy was significantly associated with higher risk for preterm birth: the pooled effect estimates were 1.09 (1.03-1.16) per 10 μg/m³ increase in particulate matter with an aerodynamic diameter of 10 µm or less (PM₁₀)_,1.24 (1.08-1.41) per 10 μg/m³ increase in particulate matter with an aerodynamic diameter of 2.5 µm or less (PM_2.5), and 1.03 (1.01-1.04) per 10 ppb increase in ozone. For pregnancy outcomes other than PTB, ranges of observed effect estimates were reported due to smaller number of studies included in each gestational window of exposure. Further research is needed to link the routine pregnancy outcome data with spatially and temporally resolved ambient air pollution data, while adjusting for commonly defined confounders. Methods for assessing exposure to mixtures of pollutants, indoor air pollution exposure, and various other environmental exposures, need to be developed.

Does residential mobility during pregnancy induce exposure misclassification for air pollution?

BACKGROUND

Prenatal exposure to outdoor air pollution has been shown to have health effects in many studies; low birth weight, preterm delivery, small for gestational age, and stillbirth are the most often cited. However, exposure of pregnant women is difficult to quantify, especially with regard to their mobility, which is rarely taken into account in epidemiological studies. This study aimed to assess the impact of mobility of pregnant women living in Paris, France, on their exposure estimates to nitrogen dioxide (NO₂).

METHODS

A total of 486 pregnant women were recruited in 5 maternity hospitals in Paris between January and April 2016. A questionnaire was used to collect mothers' characteristics (demography, education, etc.) and to assess their daily mobility during pregnancy (time spent at work, commuting time and mode used to move from residential to occupational places). Daily NO₂ concentrations were estimated based on the combination of annual average concentrations modeled at the census block scale and daily concentrations measured from fixed monitoring stations. Different models were used to compare the exposure of pregnant women in residential and occupational places, also taking into account travel time and travel mode. The socioeconomic profile of the census blocks was characterized using a multi-component index.

RESULTS

During the first trimester of pregnancy, women living in the least deprived census blocks were exposed to higher concentrations of NO₂ than those living in the most deprived ones. Occupational mobility had a small impact on exposure levels (average increase after taking account of mobility: + 0.52 μg/m³) which was not related to the socioeconomic profile of the women. The commuting mode made a greater difference (+ 1.46 μg/m³ on average), in particular among women living in the most deprived census blocks.

CONCLUSIONS

Our study illustrates that air pollution exposure can be underestimated when ignoring occupational mobility and commuting mode of pregnant women. This effect might be differential according to the neighborhood deprivation profile.

Association between birthweight and ambient PM2.5 in the United States: Individually-varied susceptibility and spatial heterogeneity

The association between maternal exposure to PM_2.5 and birthweight varies geographically, which may be caused by susceptibility. Whether this population-level association is a function of mixtures of individuals with different susceptibilities is unclear. We investigated the probability distribution of individuals with different susceptibilities to PM_2.5-related birthweight change, and evaluated spatial variation of the effect across the United States (US). We estimated the individual-level susceptibility using the effect of PM_2.5 among a homogenous subpopulation, which was defined by a specific combination of modifiers. According to frequencies for all combinations, we derived the probability distribution of differential susceptibilities across the US and by states. From birth certificates across the US (1999-2004), we analyzed a total of 18,317,707 samples of singletons. Of the samples, 54-55% were assigned valid exposures, and linked to PM_2.5. The subpopulation-specific associations of PM_2.5 on birthweight change (i.e., susceptibilities) ranged from negative to positive. For the first-trimester exposure, 61.4% of the associations were negative, and the mean was -1.01 g (95% confidence interval, CI: -1.63, -0.38) of birthweight change per 5 μg/m³ increase of PM_2.5. The state-level associations varied (from -2.04 g [-2.76, -1.31] in New Hampshire to -0.30 g [-1.01, 0.41] in Texas) with demographic compositions in the US. The between-state variations of maternal race and education level were the greatest contributors to the spatial heterogeneity. Our findings may be useful to the policymaker in planning interventions for subpopulations susceptible to ambient pollution.

Association between ambient air pollutants and preterm birth in Ningbo, China: a time-series study

BACKGROUND

Exposure to air pollutants has been related to preterm birth, but little evidence can be available for PM2.5, O3 and CO in China. This study aimed to investigate the short-term effect of exposure to air pollutants on risk preterm birth during 2014-2016 in Ningbo, China.

METHODS

We conducted a time-series study to evaluate the associations between daily preterm birth and major air pollutants (including PM2.5, PM10, SO2, NO2, O3 and CO) in Ningbo during 2014-2016. A General Additive Model extend Poisson regression was used to evaluate the relationship between preterm birth and air pollution with adjustment for time-trend, meteorological factors and day of the week (DOW). We also conducted a subgroup analysis by season and age.

RESULTS

In this study, a total of 37,389 birth occurred between 2014 and 2016 from the Electronic Medical Records System of Ningbo Women and Children's Hospital, of which 5428 were verified as preterm birth. The single pollutant model suggested that lag effect of PM2.5, PM10, NO2 reached a peak at day 3 before delivery and day 6 for SO2, and no relationships were observed for O3 and preterm birth. Excess risks (95% confidence intervals) for an increase of IQR of air pollutant concentrations were 4.84 (95% CI: 1.77, 8.00) for PM2.5, 3.56 (95% CI: 0.07, 7.17) for PM10, 3.65 (95% CI: 0.86, 6.51) for SO2, 6.49 (95% CI: 1.86, 11.34) for NO2, - 0.90 (95% CI: -4.76, 3.11) for O3, and 3.36 (95% CI: 0.50, 6.30) for CO. Sensitivity analyses by exclusion of maternal age < 18 or > 35 years did not materially alter our results.

CONCLUSIONS

This study indicates that short-term exposure to air pollutants (including PM2.5, PM10, SO2, NO2) are positively associated with risk of preterm birth in Ningbo, China.

Shale gas development and infant health: Evidence from Pennsylvania

This research exploits the introduction of shale gas wells in Pennsylvania in response to growing controversy around the drilling method of hydraulic fracturing. Using detailed location data on maternal addresses and GIS coordinates of gas wells, this study examines singleton births to mothers residing close to a shale gas well from 2003 to 2010 in Pennsylvania. The introduction of drilling increased low birth weight and decreased term birth weight on average among mothers living within 2.5 km of a well compared to mothers living within 2.5 km of a permitted well. Adverse effects were also detected using measures such as small for gestational age and APGAR scores, while no effects on gestation periods were found. In the intensive margin, an additional well is associated with a 7 percent increase in low birth weight, a 5 g reduction in term birth weight and a 3 percent increase in premature birth. These results are robust to other measures of infant health, many changes in specification and falsification tests. These findings suggest that shale gas development poses significant risks to human health.

Associations between birth outcomes and maternal PM2.5 exposure in Shanghai: A comparison of three exposure assessment approaches

BACKGROUND

Few studies have estimated effects of maternal PM_2.5 exposure on birth outcomes in China due to the lack of historical air pollution data.

OBJECTIVES

We estimated the associations between maternal PM_2.5 exposure and birth outcomes using gap-filled satellite estimates in Shanghai, China.

METHODS

We obtained birth registration records of 132,783 singleton live births during 2011-2014 in Shanghai. PM_2.5 exposures were assessed from satellite-derived estimates or central-site measurements. Linear and logistic regressions were used to estimate associations with term birth weight and term low birth weight (LBW), respectively. Logistic and discrete-time survival models were used to estimate associations with preterm birth. Effect modification by maternal age and parental education levels was investigated.

RESULTS

A 10 μg/m³ increase in gap-filled satellite-based whole-pregnancy PM_2.5 exposure was associated with a -12.85 g (95% CI: -18.44, -7.27) change in term birth weight, increased risk of preterm birth (OR 1.27, 95% CI: 1.20, 1.36), and increased risk of term LBW (OR 1.22, 95% CI: 1.06, 1.41). Sensitivity analyses during 2013-2014, when ground PM_2.5 measurements were available, showed that the health associations using gap-filled satellite PM_2.5 concentrations were higher than those obtained using satellite PM_2.5 concentrations without accounting for missingness. The health associations using gap-filled satellite PM_2.5 had similar magnitudes to those using central-site measurements, but with narrower confidence intervals.

CONCLUSIONS

The magnitude of associations between maternal PM_2.5 exposure and adverse birth outcomes in Shanghai was higher than previous findings. One reason could be reduced exposure error of the gap-filled high-resolution satellite PM_2.5 estimates.

Prenatal exposure to diesel exhaust PM2.5 causes offspring β cell dysfunction in adulthood

Environmental stressors that encounter in early-life and cause abnormal fetal and/or neonatal development may increase susceptibility to non-communicable diseases such as diabetes. Maternal exposure to ambient fine particulate matter (PM_2.5) is associated with various fetal abnormalities, suggesting that it may program offspring's susceptibility to diabetes. In the present study, we therefore examined whether maternal exposure to diesel exhaust PM_2.5 (DEP), one of the major sources of ambient PM_2.5 in urban areas, programs adult offspring's glucose metabolism. Female C57Bl/6J mice were intratracheally instilled with DEP or vehicle throughout a 7-wk preconceptional period, gestation, and lactation, and the glucose homeostasis of their adult male offspring was assessed. Intraperitoneal glucose tolerance test (IPGTT) revealed that the maternal exposure to DEP significantly impaired adult male offspring's glucose tolerance. Unexpectedly, it did not influence their insulin sensitivity, whereas it significantly decreased their glucose-induced insulin secretion (GIIS). This deficit in insulin secretion was corroborated by their significant decrease in arginine-induced insulin secretion. Histological analysis demonstrated that the deficit in insulin secretion was accompanied by the decrease in pancreatic islet and β cell sizes. To differentiate the effects of maternal exposure to DEP before birth and during lactation, some offspring were cross-fostered once born. We did not observe any significant effect of cross-fostering on the glucose homeostasis of adult male offspring and the function and morphology of their β cells. Prenatal exposure to DEP programs the morphology and function of β cells and thus homeostatic regulation of glucose metabolism in adult male offspring.

Diesel exhaust exposure, its multi-system effects, and the effect of new technology diesel exhaust

Exposure to diesel exhaust (DE) from vehicles and industry is hazardous and affects proper function of organ systems. DE can interfere with normal physiology after acute and chronic exposure to particulate matter (PM). Exposure leads to potential systemic disease processes in the central nervous, visual, hematopoietic, respiratory, cardiovascular, and renal systems. In this review, we give an overview of the epidemiological evidence supporting the harmful effects of diesel exhaust, and the numerous animal studies conducted to investigate the specific pathophysiological mechanisms behind DE exposure. Additionally, this review includes a summary of studies that used biomarkers as an indication of biological plausibility, and also studies evaluating new technology diesel exhaust (NTDE) and its systemic effects. Lastly, this review includes new approaches to improving DE emissions, and emphasizes the importance of ongoing study in this field of environmental health.

Modeling the potential health benefits of lower household air pollution after a hypothetical liquified petroleum gas (LPG) cookstove intervention

INTRODUCTION

Improved biomass and advanced fuel cookstoves can lower household air pollution (HAP), but levels of fine particulate matter (PM_2.5) often remain above the World Health Organization (WHO) recommended interim target of 35μg/m³.

METHODS

Based on existing literature, we first estimate a range of likely levels of personal PM_2.5 before and after a liquefied petroleum gas (LPG) intervention. Using simulations reflecting uncertainty in both the exposure estimates and exposure-response coefficients, we estimate corresponding expected health benefits for systolic blood pressure (SBP) in adults, birthweight, and pneumonia incidence among children <2years old. We also estimate potential avoided premature mortality among those exposed.

RESULTS

Our best estimate is that an LPG stove intervention would decrease personal PM_2.5 exposure from approximately 270μg/m³ to approximately 70μg/m³, due to likely continued use of traditional open-fire stoves. We estimate that this decrease would lead to a 5.5mmHg lower SBP among women over age 50, a 338g higher birthweight, and a 37% lower incidence of severe childhood pneumonia. We estimate that decreased SBP, if sustained, would result in a 5%-10% decrease in mortality for women over age 50. We estimate that higher birthweight would reduce infant mortality by 4 to 11 deaths per 1000 births; for comparison, the current global infant mortality rate is 32/1000 live births. Reduced exposure is estimated to prevent approximately 29 cases of severe pneumonia per year per 1000 children under 2, avoiding approximately 2-3 deaths/1000 per year. However, there are large uncertainties around all these estimates due to uncertainty in both exposure estimates and in exposure-response coefficients; all health effect estimates include the null value of no benefit.

CONCLUSIONS

An LPG stove intervention, while not likely to lower exposure to the WHO interim target level, is still likely to offer important health benefits.

A Global Perspective of Fine Particulate Matter Pollution and Its Health Effects

Fine particulate matter (PM) in the ambient air is implicated in a variety of human health issues throughout the globe. Regulation of fine PM in the atmosphere requires information on the dimension of the problem with respect to variations in concentrations and sources. To understand the current status of fine particles in the atmosphere and their potential harmful health effects in different regions of the world this review article was prepared based on peer-reviewed scientific papers, scientific reports, and database from government organizations published after the year 2000 to evaluate the global scenario of the PM_2.5 (particles <2.5 μm in aerodynamic diameter), its exceedance of national and international standards, sources, mechanism of toxicity, and harmful health effects of PM_2.5 and its components. PM_2.5 levels and exceedances of national and international standards were several times higher in Asian countries, while levels in Europe and USA were mostly well below the respective standards. Vehicular traffic has a significant influence on PM_2.5 levels in urban areas; followed by combustion activities (biomass, industrial, and waste burning) and road dust. In urban atmosphere, fine particles are mostly associated with different health effects with old aged people, pregnant women, and more so children being the most susceptible ones. Fine PM chemical constituents severely effect health due to their carcinogenic or mutagenic nature. Most of the research indicated an exceedance of fine PM level of the standards with a diverse array of health effects based on PM_2.5 chemical constituents. Emission reduction policies with epidemiological studies are needed to understand the benefits of sustainable control measures for fine PM mitigation.

Exposure to fine particulate matter during pregnancy and risk of term low birth weight in Jinan, China, 2014-2016

BACKGROUND

Existing studies exploring the association between low birth weight (LBW) and maternal fine particulate matter (aerodynamic diameter<2.5μm, PM_2.5) exposure have presented equivocal results, and one of the possible reasons for this finding might be due to relatively low maternal exposures. In addition, relatively narrow maternal exposure windows to PM_2.5 have not been well established for LBW.

METHODS

We employed a nested matched case-control design among 43,855 term births in a large maternity and child care hospital in Jinan, China. A total of 369 cases were identified, and four controls per case matched by maternal age were randomly selected among those with normal birth weight (n=1,476) from 2014 to 2016. Ambient air monitoring data on continuous measures of PM_2.5, nitrogen dioxide (NO₂), and sulfur dioxide (SO₂) (24-h average concentrations) from 2013 to 2016 were collected from thirteen local monitoring stations. An inverse distance weighting method based on both home and work addresses was adopted to estimate the individual daily exposures to these air pollutants during pregnancy by weighting the average of the twelve nearest monitoring stations within 30km of each 100m×100m grid cell by an inverse squared distance, and then the average exposure concentrations for gestational months, trimesters and the entire pregnancy were calculated. Adjusted conditional logistic regression models were used to estimate the odds ratios (ORs) per 10μg/m³ increment in PM_2.5 and by PM_2.5 quartiles during different gestational periods.

RESULTS

In this study, the estimated mean values of PM_2.5, NO₂, and SO₂ exposure during the entire pregnancy were 88.0, 54.6, and 63.1μg/m³, respectively. Term low birth weight (TLBW) increased in association with per 10μg/m³ increment in PM_2.5 for the 8th month [OR=1.13, 95% confidence interval (CI): 1.04, 1.22], the 9th month (OR=1.06, 95% CI: 0.99, 1.15), the third trimester (OR=1.17, 95% CI: 1.05, 1.29), and the entire pregnancy (OR=1.38, 95% CI: 1.07, 1.77) in models adjusted for one pollutant (PM_2.5). In models categorizing the PM_2.5 exposure by quartiles, comparing the second, third, and highest with the lowest PM_2.5 exposure quartile, the PM_2.5 was positively associated with TLBW during the 8th month (OR: 1.77, 95% CI: 1.09, 2.88; OR: 1.77, 95% CI: 1.03, 3.04; OR: 1.92, 95% CI: 1.04, 3.55, respectively) and for the 9th month, only association for exposure in the third versus the lowest quartile was significant (OR: 1.91, 95% CI: 1.02, 3.58).

CONCLUSIONS

The study provides evidence that exposure to PM_2.5 during pregnancy might be associated with the risk of TLBW in the context of very high pollution level of PM_2.5, and the 8th and 9th months were identified as potentially relevant exposure windows.

Association between ambient fine particulate matter and preterm birth or term low birth weight: An updated systematic review and meta-analysis

An increasing number of studies have been conducted to determine a possible linkage between maternal exposure to ambient fine particulate matter and effects on the developing human fetus that can lead to adverse birth outcomes, but, the present results are not consistent. A total of 23 studies published before July 2016 were collected and analyzed and the mean value of reported exposure to fine particulate matter (PM_2.5) ranged from 1.82 to 22.11 We found a significantly increased risk of preterm birth with interquartile range increase in PM_2.5 exposure throughout pregnancy (odds ratio (OR) = 1.03; 95% conditional independence (CI): 1.01-1.05). The pooled OR for the association between PM_2.5 exposure, per interquartile range increment, and term low birth weight throughout pregnancy was 1.03 (95% CI: 1.02-1.03). The pooled ORs for the association between PM_2.5 exposure per 10 increment, and term low birth weight and preterm birth were 1.05 (95% CI: 0.98-1.12) and 1.02 (95% CI: 0.93-1.12), respectively throughout pregnancy. There is a significant heterogeneity in most meta-analyses, except for pooled OR per interquartile range increase for term low birth weight throughout pregnancy. We here show that maternal exposure to fine particulate air pollution increases the risk of preterm birth and term low birth weight. However, the effect of exposure time needs to be further explored. In the future, prospective cohort studies and personal exposure measurements needs to be more widely utilized to better characterize the relationship between ambient fine particulate exposure and adverse birth outcomes.

Different exposure levels of fine particulate matter and preterm birth: a meta-analysis based on cohort studies

The previous studies estimated the association between PM_2.5 (particulate matter with aerodynamic diameter less than or equal to 2.5 μm) exposure during pregnancy and preterm birth, only considered and highlighted the hazard effects of high levels of air pollutant exposure, and underestimated that low levels of pollutant exposure might also affect pregnancy outcome. We conducted a meta-analysis of 11 cohort studies, a total of more than 1,500,000 subjects. The results of these studies were pooled by exposure levels and study periods. PM_2.5 exposure during pregnancy was positively associated with preterm birth (OR = 1.15, 95% CI = 1.07-1.23), and during the first trimester of pregnancy, low levels of PM_2.5 exposure were also positively associated with preterm birth (OR = 1.17, 95% CI = 1.04-1.30). It is important to protect pregnant women from PM_2.5 exposures, especially during their first trimester of pregnancy even when the ambient PM_2.5 concentration is relatively low. More relevant health policy should be carried out to prevent hazard effect of air pollutants.

Programming of mouse obesity by maternal exposure to concentrated ambient fine particles

BACKGROUND

Many diseases including obesity may originate through alterations in the early-life environment that interrupts fetal development. Increasing evidence has shown that exposure to ambient fine particles (PM2.5) is associated with abnormal fetal development. However, its long-term metabolic effects on offspring have not been systematically investigated.

RESULTS

To determine if maternal exposure to PM2.5 programs offspring obesity, female C57Bl/6j mice were exposed to filtered air (FA) or concentrated ambient PM2.5 (CAP) during pre-conception, pregnancy, and lactation, and the developmental and metabolic responses of offspring were assessed. The growth trajectory of offspring revealed that maternal exposure to CAP significantly decreased offspring birth weight but increased body weight of adult male but not female offspring, and the latter was expressed as increased adiposity. These adult male offspring had increased food intake, but were sensitive to exogenous leptin. Their hypothalamic expression of Socs3 and Pomc, two target genes of leptin, was not changed, and the hypothalamic expression of NPY, an orexigenic peptide that is inhibited by leptin, was significantly increased. These decreases in central anorexigenic signaling were accompanied by reduced plasma leptin and its expression in adipose tissues, the primary source of circulating leptin. In contrast, maternal exposure did not significantly change any of these indexes in adult female offspring. Pyrosequencing demonstrated that the leptin promoter methylation of adipocytes was significantly increased in CAP-exposed male but not female offspring.

CONCLUSIONS

Our data indicate that maternal exposure to ambient PM2.5 programs obesity in male offspring probably through alterations in the methylation of the promoter region of the leptin gene.

Preterm birth associated with maternal fine particulate matter exposure: A global, regional and national assessment

Reduction of preterm births (<37 completed weeks of gestation) would substantially reduce neonatal and infant mortality, and deleterious health effects in survivors. Maternal fine particulate matter (PM_2.5) exposure has been identified as a possible risk factor contributing to preterm birth. The aim of this study was to produce the first estimates of ambient PM_2.5-associated preterm births for 183 individual countries and globally. To do this, national, population-weighted, annual average ambient PM_2.5 concentration, preterm birth rate and number of livebirths were combined to calculate the number of PM_2.5-associated preterm births in 2010 for 183 countries. Uncertainty was quantified using Monte-Carlo simulations, and analyses were undertaken to investigate the sensitivity of PM_2.5-associated preterm birth estimates to assumptions about the shape of the concentration-response function at low and high PM_2.5 exposures, inclusion of provider-initiated preterm births, and exposure to indoor air pollution. Globally, in 2010, the number of PM_2.5-associated preterm births was estimated as 2.7 million (1.8-3.5 million, 18% (12-24%) of total preterm births globally) with a low concentration cut-off (LCC) set at 10μgm^-3, and 3.4 million (2.4-4.2 million, 23% (16-28%)) with a LCC of 4.3μgm^-3. South and East Asia, North Africa/Middle East and West sub-Saharan Africa had the largest contribution to the global total, and the largest percentage of preterm births associated with PM_2.5. Sensitivity analyses showed that PM_2.5-associated preterm birth estimates were 24% lower when provider-initiated preterm births were excluded, 38-51% lower when risk was confined to the PM_2.5 exposure range in the studies used to derive the effect estimate, and 56% lower when mothers who live in households that cook with solid fuels (and whose personal PM_2.5 exposure is likely dominated by indoor air pollution) were excluded. The concentration-response function applied here derives from a meta-analysis of studies, most of which were conducted in the US and Europe, and its application to the areas of the world where we estimate the greatest effects on preterm births remains uncertain. Nevertheless, the substantial percentage of preterm births estimated to be associated with anthropogenic PM_2.5 (18% (13%-24%) of total preterm births globally) indicates that reduction of maternal PM_2.5 exposure through emission reduction strategies should be considered alongside mitigation of other risk factors associated with preterm births.

The Influence of Meteorological Factors and Atmospheric Pollutants on the Risk of Preterm Birth

Atmospheric pollutants and meteorological conditions are suspected to be causes of preterm birth. We aimed to characterize their possible association with the risk of preterm birth (defined as birth occurring before 37 completed gestational weeks). We pooled individual data from 13 birth cohorts in 11 European countries (71,493 births from the period 1994-2011, European Study of Cohorts for Air Pollution Effects (ESCAPE)). City-specific meteorological data from routine monitors were averaged over time windows spanning from 1 week to the whole pregnancy. Atmospheric pollution measurements (nitrogen oxides and particulate matter) were combined with data from permanent monitors and land-use data into seasonally adjusted land-use regression models. Preterm birth risks associated with air pollution and meteorological factors were estimated using adjusted discrete-time Cox models. The frequency of preterm birth was 5.0%. Preterm birth risk tended to increase with first-trimester average atmospheric pressure (odds ratio per 5-mbar increase = 1.06, 95% confidence interval: 1.01, 1.11), which could not be distinguished from altitude. There was also some evidence of an increase in preterm birth risk with first-trimester average temperature in the -5°C to 15°C range, with a plateau afterwards (spline coding, P = 0.08). No evidence of adverse association with atmospheric pollutants was observed. Our study lends support for an increase in preterm birth risk with atmospheric pressure.

Prenatal and postnatal mothering by diesel exhaust PM2.5-exposed dams differentially program mouse energy metabolism

BACKGROUND

Obesity is one of the leading threats to global public health. It is consequent to abnormal energy metabolism. Currently, it has been well established that maternal exposure to environmental stressors that cause inappropriate fetal development may have long-term adverse effects on offspring energy metabolism in an exposure timing-dependent manner, known as developmental programming of health and diseases paradigm. Rapidly increasing evidence has indicated that maternal exposure to ambient fine particles (PM2.5) correlates to abnormal fetal development. In the present study, we therefore assessed whether maternal exposure to diesel exhaust PM2.5 (DEP), the major component of ambient PM2.5 in urban areas, programs offspring energy metabolism, and further examined how the timing of exposure impacts this programming.

RESULTS

The growth trajectory of offspring shows that although prenatal maternal exposure to DEP did not impact the birth weight of offspring, it significantly decreased offspring body weight from postnatal week 2 until the end of observation. This weight loss effect of prenatal maternal exposure to DEP coincided with decreased food intake but not alteration in brown adipose tissue (BAT) morphology. The hypophagic effect of prenatal maternal exposure to DEP was in concord with decreased hypothalamic expression of an orexigenic peptide NPY, suggesting that the prenatal maternal exposure to DEP impacts offspring energy balance primarily through programming of food intake. Paradoxically, the reduced body weight resulted from prenatal maternal exposure to DEP was accompanied by increased mass of epididymal adipose tissue, which was due to hyperplasia as morphological analysis did not observe any hypertrophy. In direct contrast, the postnatal mothering by DEP-exposed dams increased offspring body weight during lactation and adulthood, paralleled by markedly increased fat accumulation and decreased UCP1 expression in BAT but not alteration in food intake. The weight gain induced by postnatal mothering by DEP-exposed dams was also expressed as an increased adiposity. But it concurred with a marked hypertrophy of adipocytes.

CONCLUSION

Prenatal and postnatal mothering by DEP-exposed dams differentially program offspring energy metabolism, underscoring consideration of the exposure timing when examining the adverse effects of maternal exposure to ambient PM2.5.

Associations of Short-Term and Long-Term Exposure to Ambient Air Pollutants With Hypertension

Hypertension is a major disease of burden worldwide. Previous studies have indicated that air pollution might be a risk factor for hypertension, but the results were controversial. To fill this gap, we performed a meta-analysis of epidemiological studies to investigate the associations of short-term and long-term exposure to ambient air pollutants with hypertension. We searched all of the studies published before September 1, 2015, on the associations of ozone (O 3 ), carbon monoxide (CO), nitrogen oxide (NO 2 and NO X ), sulfur dioxide (SO 2 ), and particulate matter (PM 10 and PM 2.5 ) with hypertension in the English electronic databases. A pooled odds ratio (OR) for hypertension in association with each 10 μg/m 3 increase in air pollutant was calculated by a random-effects model (for studies with significant heterogeneity) or a fixed-effect model (for studies without significant heterogeneity). A total of 17 studies examining the effects of short-term (n=6) and long-term exposure (n=11) to air pollutants were identified. Short-term exposure to SO 2 (OR=1.046, 95% confidence interval [CI]: 1.012–1.081), PM 2.5 (OR=1.069, 95% CI: 1.003–1.141), and PM 10 (OR=1.024, 95% CI: 1.016–1.032) were significantly associated with hypertension. Long-term exposure (a 10 μg/m 3 increase) to NO 2 (OR=1.034, 95% CI: 1.005–1.063) and PM 10 (OR=1.054, 95% CI: 1.036–1.072) had significant associations with hypertension. Exposure to other ambient air pollutants (short-term exposure to NO 2 , O 3 , and CO and long-term exposure to NO x , PM 2.5 , and SO 2 ) also had positive relationships with hypertension, but lacked statistical significance. Our results suggest that short-term or long-term exposure to some air pollutants may increase the risk of hypertension.

Ambient air pollution and adverse birth outcomes: Differences by maternal comorbidities

BACKGROUND

Prenatal exposure to ambient air pollution has been associated with adverse birth outcomes, but the potential modifying effect of maternal comorbidities remains understudied. Our objective was to investigate whether associations between prenatal air pollution exposures and birth outcomes differ by maternal comorbidities.

METHODS

A total of 818,400 singleton live births were identified in the province of Ontario, Canada from 2005 to 2012. We assigned exposures to fine particulate matter (PM2.5), nitrogen dioxide (NO2) and ozone (O3) to maternal residences during pregnancy. We evaluated potential effect modification by maternal comorbidities (i.e. asthma, hypertension, pre-existing diabetes mellitus, heart disease, gestational diabetes and preeclampsia) on the associations between prenatal air pollution and preterm birth, term low birth weight and small for gestational age.

RESULTS

Interquartile range (IQR) increases in PM2.5 (2μg/m(3)), NO2 (9ppb) and O3 (5ppb) over the entire pregnancy were associated with a 4% (95% CI: 2.4-5.6%), 8.4% (95% CI: 5.5-10.3%) and 2% (95% CI: 0.5-4.1%) increase in the odds of preterm birth, respectively. Increases of 10.6% (95% CI: 0.2-2.1%) and 23.8% (95% CI: 5.5-44.8%) in the odds of preterm birth were observed among women with pre-existing diabetes while the increases were of 3.8% (95% CI: 2.2-5.4%) and 6.5% (95% CI: 3.7-8.4%) among women without this condition for pregnancy exposure to PM2.5 and NO2, respectively (Pint<0.01). The increase in the odds of preterm birth for exposure to PM2.5 during pregnancy was higher among women with preeclampsia (8.3%, 95% CI: 0.8-16.4%) than among women without (3.6%, 95% CI: 1.8-5.3%) (Pint=0.04). A stronger increase in the odds of preterm birth was found for exposure to O3 during pregnancy among asthmatic women (12.0%, 95% CI: 3.5-21.1%) compared to non-asthmatic women (2.0%, 95% CI: 0.1-3.5%) (Pint<0.01). We did not find statistically significant effect modification for the other outcomes investigated.

CONCLUSIONS

Findings of this study suggest that associations of ambient air pollution with preterm birth are stronger among women with pre-existing diabetes, asthma, and preeclampsia.