Exposure to ambient air pollution during pregnancy and preterm birth: A Spanish multicenter birth cohort study

Residential proximity to conventional and unconventional wells and exposure to indoor air volatile organic compounds in the Exposures in the Peace River Valley (EXPERIVA) study

BACKGROUND

In a previous study located in Northeastern British Columbia (Canada), we observed associations between density and proximity of oil and gas wells and indoor air concentrations of certain volatile organic compounds (VOCs). Whether conventional or unconventional well types and phases of unconventional development contribute to these associations remains unknown.

OBJECTIVE

To investigate the associations between proximity-based metrics for conventional and unconventional wells and measured indoor air VOC concentrations in the Exposures in the Peace River Valley (EXPERIVA) study samples.

METHODS

Eighty-four pregnant individuals participated in EXPERIVA. Passive indoor air samplers were analyzed for 47 VOCs. Oil and gas well legacy data were sourced from the British Columbia Energy Regulator. For each participant's home, 5 km, 10 km and no buffer distances were delineated, then density and Inverse Distance Square Weighted (ID2W) metrics were calculated to estimate exposure to conventional and unconventional wells during pregnancy and the VOC measurement period. Multiple linear regression models were used to test for associations between the well exposure metrics and indoor air VOCs. For exposure metrics with >30% participants having a value of 0, we dichotomized exposure (0 vs. >0) and performed ANOVAs to assess differences in mean VOCs concentrations.

RESULTS

Analyses indicated that: 1) conventional well density and ID2W metrics were positively associated with indoor air acetone and decanal; 2) unconventional well density and ID2W metrics were positively associated with indoor air chloroform and decamethylcyclopentasiloxane, and negatively associated with decanal; 3) drilling specific ID2W metrics for unconventional wells were positively associated with indoor air chloroform.

CONCLUSION

Our analysis revealed that the association between the exposure metrics and indoor air acetone could be attributed to conventional wells and the association between exposure metrics and indoor air chloroform and decamethylcyclopentasiloxane could be attributed to unconventional wells.

Associations between weekly gestational exposure of fine particulate matter, ozone, and nitrogen dioxide and preterm birth in a North Carolina Birth Cohort, 2003-2015

Background

Preterm birth (PTB; <37 weeks completed gestation) is associated with exposure to air pollution, though variability in association magnitude and direction across exposure windows exists. We evaluated associations between weekly gestational exposure to fine particulate matter (PM2.5), nitrogen dioxide (NO2), and ozone (O3) with PTB in a North Carolina Birth Cohort from 2003 to 2015 (N = 1,367,517).

Methods

Daily average PM2.5 and daily 8-hour maximum NO2 concentration estimates were obtained from a hybrid ensemble model with a spatial resolution of 1 km2. Daily 8-hour maximum census tract-level concentration estimates for O3 were obtained from the EPA's Fused Air Quality Surface Using Downscaling model. Air pollutant concentrations were linked by census tract to residential address at delivery and averaged across each week of pregnancy. Modified Poisson regression models with robust errors were used to estimate risk differences (RD [95% confidence intervals (CI)]) for an interquartile range increase in pollutants per 10,000 births, adjusted for potential confounders.

Results

Associations were similar in magnitude across weeks. We observed positive associations for PM2.5 and O3 exposures, but generally null associations with NO2. RDs ranged from 15 (95% CI = 11, 18) to 32 (27, 37) per 10,000 births for PM2.5; from -7 (-14, -1) to 0 (-5, 4) for NO2; and from 4 (1, 7) to 13 (10, 16) for O3.

Conclusion

Our results show that increased PM2.5 exposure is associated with an increased risk of PTB across gestational weeks, and these associations persist in multipollutant models with NO2 and/or O3.

The type of previous abortion modifies the association between air pollution and the risk of preterm birth

BACKGROUND

Air pollution and previous abortion have been reported to be related to preterm birth (PTB). But rare study examined the effect of air pollution on PTB risk among mothers with previous abortion.

OBJECTIVE

To estimate the effect of air pollution on PTB and the potential effect modification of previous abortion on such an association in rural part of Henan province (China).

METHOD

Based on National Free Preconception Health Examination Project (NFPHEP), information from the medical records of 57,337 mothers with previous abortion were obtained. An inverse distance-weighted model was used to estimate exposure levels of air pollutants. The effect of air pollution on the risk of PTB was estimated with a multiple logistic regression model. Stratified and interaction analyses were undertaken to explore the potential effect modification of previous abortion on this association.

RESULTS

The risk of PTB was positively associated with exposure to levels of nitrogen dioxide (NO₂; OR: 1.03; 95%CI: 1.02-1.04)], and sulfur dioxide (SO₂; 1.04; 1.02-1.07), and negatively associated with ozone (O₃) exposure (0.97; 0.97-0.98) during the entire pregnancy. Besides, we observed a positive effect of carbon monoxide (CO) exposure during the third trimester of pregnancy on PTB (1.14; 1.01-1.29). The type of previous abortion could modify the effect of air pollution on the PTB risk (P-_interaction < 0.05). Compared with mothers with previous induced abortion, mothers with previous spontaneous abortion carried a higher risk of PTB induced by NO₂, CO, and O₃.

CONCLUSIONS

The risk of PTB was positively associated with levels of NO₂, SO₂ and CO, and negatively associated with the O₃ level. The types of previous abortion could modify the effect of air pollution on PTB. Mothers who had an abortion previously, especially spontaneous abortion, should avoid exposure to air pollution to improve their pregnancy outcome.

Gestational exposure to NO2 aggravates placental senescence

Placental senescence is a normal physiological process of placenta, while premature placental senescence has been confirmed to be associated with some adverse pregnancy complications. Epidemiological studies indicate that NO₂ exposure can aggravate placental senescence which is represented by fibrosis and abnormal telomere homeostasis, etc. In this study, pregnant C57BL/6 mice were exposed to NO₂ (2.5 ppm, 5 h/day) daily in a dynamic exposure chamber throughout the gestation period, and were sacrificed at embryonic day 13.5 (E13.5), E15.5 and E18.5. Placenta were harvested and conducted for histopathological examination and telomere evaluation. Our results showed that gestational NO₂ exposure significantly aggravated placental fibrosis and calcification, and up-regulated the related bio-markers (connective tissue growth factor (Ctgf) and transforming growth factor-β1 (Tgf-β1)) at E18.5. In addition, gestational exposure to NO₂ also activated senescence related pathway (p53/p21) at E18.5. Furthermore, gestational NO₂ exposure significantly shortened telomere length at E18.5, and the expression of telomere homeostasis regulation genes telomeric repeat binding factor 1 (Trf1), protection of telomeres 1a (Pot1a) and Pot1b were significantly increased while telomerase reverse transcriptase (Tert) was suppressed after NO₂ exposure at E13.5 or E18.5, respectively. Importantly, DNA methylation status of the 22^nd at E13.5 and 32^nd at E18.5 site in sub-telomeric region of chromosome 1 was significantly altered. Based on the above results, our present study indicated that gestational NO₂ exposure could lead to premature placental senescence during the late trimester of pregnancy via aggravation of fibrosis and telomere length shortening regulated by telomere regulatory enzyme and DNA methylation.

Long-term impact of ambient air pollution on preterm birth in Xuzhou, China: a time series study

Accumulating evidence witnesses the negative influence of air pollution on human health, but the relationship between air pollution and premature babies has been inconsistent. In this study, the association between weekly average concentration of air pollutants and preterm birth (PTB) was conducted in Xuzhou, a heavy industry city, in China. We constructed a distributed lag non-linear model (DLNM), an ecological study, to access the associations between ambient air pollutants and PTB in this study. Totally, 5408 premature babies were included, and the weekly average levels of PM_2.5, PM₁₀, SO₂, NO₂, O₃, and CO were 61.24, 110.21, 22.55, 40.55, 104.45, and 1.04 mg/m³, respectively. We found that PM_2.5, PM₁₀, SO₂, and NO₂ significantly increased the risk of PTB, and the susceptibility windows of these contaminants were the second trimester and third trimester (from 12 to 29 weeks). Every 10 μg/m³ increase of PM_2.5, PM₁₀, SO₂, and NO₂, the greatest relative risk (RR) values and 95% confidence interval (CI) on PTB were 1.0075 [95% CI, 1.0019-1.0131], 1.0053 [95% CI, 1.0014-1.0092], 1.0203 [95% CI, 1.0030-1.0379], and 1.0170 [95% CI, 1.0052-1.0289] in lag 16th, 18th, 19th, and 20th gestational weeks, respectively. No significant influence of O₃ and CO were found on preterm birth. Subgroup analysis showed that the risk of premature delivery was higher for younger pregnant women and in warm season. This finding shows that prenatal exposure to ambient air pollutants is associated with preterm birth, and there existed an exposure window period.

Effects of air pollution, land-use type, and maternal mental health on child development in the first two years of life in the Greater Taipei area

INTRODUCTION

Few studies have investigated the associations of child development with air pollution, land-use type, and maternal mental health simultaneously. Therefore, we evaluated the effect of exposure to air pollutants during several critical periods of life, with adjustment for land-use type and maternal mental status, on child development at 6, 12, and 24 months of age in the Greater Taipei area.

METHODS

Participants were selected from an ongoing Taiwanese birth cohort study. We analyzed the data of the participants who had been recruited from January 2011 to April 2014. Self-administered standardized questionnaires were used to collect information on sociodemographic factors, infant development and health, maternal mental status, etc. Air pollution levels in pre- and postnatal periods were estimated using a spatial interpolation technique (ordinary kriging) at children's residential addresses. Land-use types around participants' homes were evaluated using buffer analysis. We used multiple logistic regression analysis to examine the relationships between child development delay and environmental factors.

RESULTS

In total, 228, 361, and 441 families completed child development forms at 6, 12, and 24 months of age, respectively. Our results indicated that prenatal exposure to particulate matter with aerodynamic diameter ≤10 μm and O₃ and postnatal exposure to NO₂ were negatively associated with child development. Traffic-related land-use types, gas stations, and power generation areas around participants' homes were also adversely correlated with child development. Moreover, poor maternal mental health was associated with child development delay.

CONCLUSION

Prenatal exposure and postnatal exposure to air pollution were associated with development delay in children under 2 years of age, specifically those under 1 year of age, even after adjustment for land-use type and maternal mental status. Living environment is critical for the development of children under 2 years of age.

Air pollution exposure and risk of adverse obstetric and neonatal outcomes among women with type 1 diabetes

AIMS/HYPOTHESIS

Women with type 1 diabetes have increased risk for poor obstetric outcomes. Prenatal air pollution exposure is also associated with adverse outcomes for women and infants. We examined whether women with type 1 diabetes are more vulnerable than other women to pollution-associated risks during pregnancy.

METHODS

In singleton deliveries from the Consortium on Safe Labor (2002-2008), obstetric and neonatal outcomes were compared for women with type 1 diabetes (n = 507) and women without autoimmune disease (n = 204,384). Preconception, trimester, and whole pregnancy average air pollutant exposure (ozone (O₃), carbon monoxide (CO), particulate matter >10 μm (PM₁₀), PM > 2.5 μm (PM_2.5), sulfur dioxide (SO₂), nitrogen oxides (NO_x)) were estimated using modified Community Multiscale Air Quality models. Poisson regression models with diabetes*pollutant interaction terms estimated relative risks and 95% confidence intervals for adverse outcomes, adjusted for maternal characteristics and geographic region.

RESULTS

For whole pregnancy exposure to SO₂, women with type 1 diabetes had 15% increased risk (RR:1.15 95%CI:1.01,1.31) and women without autoimmune disease had 5% increased risk (RR:1.05 95%CI:1.05,1.06) for small for gestational age birth (p_interaction = 0.09). Additionally, whole pregnancy O₃ exposure was associated with 10% increased risk (RR:1.10 95%CI:1.02,1.17) among women with type 1 diabetes and 2% increased risk (RR:1.02 95%CI:1.00,1.04) among women without autoimmune disease for perinatal mortality (p_interaction = 0.08). Similar patterns were observed between PM_2.5 exposure and spontaneous preterm birth.

CONCLUSIONS

Pregnant women with type 1 diabetes may be at greater risk for adverse outcomes when exposed to air pollution than women without autoimmune disease.

Air pollution and pregnancy outcomes based on exposure evaluation using a land use regression model: A systematic review

This review systematically assessed those studies investigating the association between air pollution and birth outcomes using land use regression (LUR) models for exposure assessment. Fifty-four studies were identified which were published between 2007 and 2019. Most of these were conducted in America, Spain and Canada, while only five were conducted in China. One hundred and ninety-seven LUR models were developed for different pollutants. The main pollutants that these studies assessed were NO₂ and PM_2.5, and the main pregnancy outcomes investigated were preterm birth (PTB), small for gestational age (SGA) and birth weight. Studies consistently found that NO₂ exposure during pregnancy was associated with reduced fetal growth and development. The effect of NO₂ on other adverse pregnancy outcomes is unclear. In addition, it was found that increased PM_2.5 (aerodynamic equivalent diameter ≤ 2.5 um) exposure during pregnancy reduced birth weight. The effect of PM_2.5 on other adverse pregnancy outcomes is also unclear. The relationship between other pollutants and adverse pregnancy outcomes is uncertain based on the existing research. Exposure assessment with LUR modeling has been widely used in Europe and North America, but used less in China. Future studies are recommended to use LUR modeling for individual exposure evaluation in China to better characterize the relationship between air pollution and adverse pregnancy outcomes. In addition, further research is required given that a lot of the associations looked at in the review were inconclusive.

Density and proximity to hydraulic fracturing wells and birth outcomes in Northeastern British Columbia, Canada

BACKGROUND

Hydraulic fracturing, a method used in Northeastern British Columbia (Canada) to extract natural gas, can release contaminants with potential deleterious health effects on fetal development. To date, the association between hydraulic fracturing activity and birth outcomes has not been evaluated in this region.

OBJECTIVE

To evaluate the association between the hydraulic fracturing well density/proximity and birth outcomes (birthweight, head circumference, preterm birth and small for gestational age (SGA)).

METHODS

We used birth records from the Fort St John hospital between December 30, 2006 and December 29, 2016 (n = 6333 births). To estimate gestational exposure, we used inverse distance weighting (IDW) to calculate the density/proximity of hydraulic fracturing wells to pregnant women's postal code centroid. For each birth, we calculated three IDWs using 2.5, 5, and 10 km buffer zones around women's postal code centroid. We used linear and logistic regressions to evaluate associations between quartiles of postal code well density/proximity and birth outcomes, controlling for relevant covariates.

RESULTS

No associations were found between postal code well density/proximity and head circumference or SGA. A negative association was found between postal code well density/proximity and birthweight for infants born to women in the 2nd quartile of the 10 km buffer (β [95% confidence interval (CI)]: -47.28 g [-84.30; -10.25]), and in the 2nd (β [95% CI]: -40.87 g [-78.01; -3.73]) and 3rd (β [95% CI]: -42.01 g [-79.15; -4.87]) quartiles of the 5 km buffer. Increased odds of preterm birth were observed among women in the 2nd quartile of the 2.5 km buffer (odds ratio (OR) [95% CI]: 1.60 [1.30; 2.43]).

CONCLUSIONS

This is the first epidemiological study in Northeastern British Columbia evaluating associations between hydraulic fracturing and health outcomes. Our results show inconsistent patterns of association between hydraulic fracturing, preterm birth and reduced birthweight, and effect estimates did not match expected dose-response relationships.

Adverse Birth Outcomes Related to NO2 and PM Exposure: European Systematic Review and Meta-Analysis

There is a growing number of international studies on the association between ambient air pollution and adverse pregnancy outcomes, and this systematic review and meta-analysis has been conducted focusing on European countries, to assess the crucial public health issue of this suspected association on this geographical area. A systematic literature search (based on Preferred Reporting Items for Systematic reviews and Meta-Analyses, PRISMA, guidelines) has been performed on all European epidemiological studies published up until 1 April 2020, on the association between maternal exposure during pregnancy to nitrogen dioxide (NO₂) or particular matter (PM) and the risk of adverse birth outcomes, including: low birth weight (LBW) and preterm birth (PTB). Fourteen articles were included in the systematic review and nine of them were included in the meta-analysis. Our meta-analysis was conducted for 2 combinations of NO₂ exposure related to birth weight and PTB. Our systematic review revealed that risk of LBW increases with the increase of air pollution exposure (including PM₁₀, PM_2.5 and NO₂) during the whole pregnancy. Our meta-analysis found that birth weight decreases with NO₂ increase (pooled beta = −13.63, 95% confidence interval (CI) (−28.03, 0.77)) and the risk of PTB increase for 10 µg/m3 increase in NO₂ (pooled odds ratio (OR) = 1.07, 95% CI (0.90, 1.28)). However, the results were not statistically significant. Our finding support the main international results, suggesting that increased air pollution exposure during pregnancy might contribute to adverse birth outcomes, especially LBW. This body of evidence has limitations that impede the formulation of firm conclusions. Further studies, well-focused on European countries, are called to resolve the limitations which could affect the strength of association such as: the exposure assessment, the critical windows of exposure during pregnancy, and the definition of adverse birth outcomes. This analysis of limitations of the current body of research could be used as a baseline for further studies and may serve as basis for reflection for research agenda improvements.

Differential association of air pollution exposure with neonatal and postneonatal mortality in England and Wales: A cohort study

BACKGROUND

Many but not all studies suggest an association between air pollution exposure and infant mortality. We sought to investigate whether pollution exposure is differentially associated with all-cause neonatal or postneonatal mortality, or specific causes of infant mortality.

METHODS AND FINDINGS

We separately investigated the associations of exposure to particulate matter with aerodynamic diameter ≤ 10 μm (PM10), nitrogen dioxide (NO2), and sulphur dioxide (SO2) with all-cause infant, neonatal, and postneonatal mortality, and with specific causes of infant deaths in 7,984,366 live births between 2001 and 2012 in England and Wales. Overall, 51.3% of the live births were male, and there were 36,485 infant deaths (25,110 neonatal deaths and 11,375 postneonatal deaths). We adjusted for the following major confounders: deprivation, birthweight, maternal age, sex, and multiple birth. Adjusted odds ratios (95% CI; p-value) for infant deaths were significantly increased for NO2, PM10, and SO2 (1.066 [1.027, 1.107; p = 0.001], 1.044 [1.007, 1.082; p = 0.017], and 1.190 [1.146, 1.235; p < 0.001], respectively) when highest and lowest pollutant quintiles were compared; however, neonatal mortality was significantly associated with SO2 (1.207 [1.154, 1.262; p < 0.001]) but not significantly associated with NO2 and PM10 (1.044 [0.998, 1.092; p = 0.059] and 1.008 [0.966, 1.052; p = 0.702], respectively). Postneonatal mortality was significantly associated with all pollutants: NO2, 1.108 (1.038, 1.182; p < 0.001); PM10, 1.117 (1.050, 1.188; p < 0.001); and SO2, 1.147 (1.076, 1.224; p < 0.001). Whilst all were similarly associated with endocrine causes of infant deaths (NO2, 2.167 [1.539, 3.052; p < 0.001]; PM10, 1.433 [1.066, 1.926; p = 0.017]; and SO2, 1.558 [1.147, 2.116; p = 0.005]), they were differentially associated with other specific causes: NO2 and PM10 were associated with an increase in infant deaths from congenital malformations of the nervous (NO2, 1.525 [1.179, 1.974; p = 0.001]; PM10, 1.457 [1.150, 1.846; p = 0.002]) and gastrointestinal systems (NO2, 1.214 [1.006, 1.466; p = 0.043]; PM10, 1.312 [1.096, 1.571; p = 0.003]), and NO2 was also associated with deaths from malformations of the respiratory system (1.306 [1.019, 1.675; p = 0.035]). In contrast, SO2 was associated with an increase in infant deaths from perinatal causes (1.214 [1.156, 1.275; p < 0.001]) and from malformations of the circulatory system (1.172 [1.011, 1.358; p = 0.035]). A limitation of this study was that we were not able to study associations of air pollution exposure and infant mortality during the different trimesters of pregnancy. In addition, we were not able to control for all confounding factors such as maternal smoking.

CONCLUSIONS

In this study, we found that NO2, PM10, and SO2 were differentially associated with all-cause mortality and with specific causes of infant, neonatal, and postneonatal mortality.

Interactions between Environmental Exposures and the Microbiome: Implications for Fetal Programming

Decades of population-based health outcomes data highlight the importance of understanding how environmental exposures in pregnancy affect maternal and neonatal outcomes. Animal model research and epidemiological studies have revealed that such exposures are able to alter fetal programming through stable changes in the epigenome, including altered DNA methylation patterns and histone modifications in the developing fetus and infant. It is similarly known that while microbes can biotransform environmental chemicals via conjugation and de-conjugation, specific exposures can also alter the community profile and function of the human microbiome. In this review, we consider how alterations to the maternal and or fetal/infant microbiome through environmental exposures could directly and indirectly alter fetal programming. We highlight two specific environmental exposures, cadmium (Cd) and polycyclic aromatic hydrocarbons (PAHs), and outline their effects on the developing fetus and the perinatal (maternal and fetal/infant) microbiome. We further consider how chemical exposures in the setting of natural disasters may be of particular importance to environmental health.

Source-related components of fine particulate matter and risk of adverse birth outcomes in Northern Italy

BACKGROUND/AIM

The aim of the present study was to assess the association between PM_2.5, its sources, and preterm birth (PTB), low birth weight (LBW), and small for gestational age (SGA) in a large open residential cohort (Supersito Project in the Emilia-Romagna Region - Northern Italy).

METHODS

We collected 2012-2014 pregnancy and childbirth data from Birth Assistance Certificates and selected the pregnancies of interest. PTBs (gestational age < 37 weeks), LBW (weight < 2500 g), and SGA (newborns weighing ≤ 10th age and pregnancy week-specific percentile) were considered. Three-year measurements of daily concentrations and constituents of PM_2.5 were available at four sites and were analyzed through a source apportionment approach identifying 6 sources (traffic, biomass burning, oil combustion, anthropogenic mix, and two secondary factors). Exposure to PM_2.5 and sources was calculated at address level. Using logistic regression models, associations between exposure and outcomes were derived, applying single-pollutant and two-pollutant models, to verify the independent effect of each source.

RESULTS

The study included 23,708 neonates born to 23,415 women, among whom 1,311 PTB, 424 LBW, and 1,354 SGA occurred. PTB was the only outcome associated with PM_2.5 mass (OR 1.03, 95% CI 1.002-1.058 per 1 μg/m³). Traffic, oil combustion and secondary sulfates and organics showed independent effects on PTB. Exposure to secondary nitrates was associated with a lower risk of PTB. There was no association between LBW or SGA and source-specific PM_2.5 components or the residual PM_2.5 related to all other sources.

CONCLUSION

This study found an association between PTB and PM_2.5. Traffic, secondary sulfates, and organic and oil combustion were the sources with most consistent association.

Acute Effects of Exposure to Ambient Air Pollutants on Preterm Birth in Xiamen City (2015-2018), China

Backgrounds: Urban energy consumption is one of the important causes of air pollution. The epidemiological risk assessment guided by air pollution is of great significance to the promotion of urban environmental protection. Objectives: The work researched the acute impact of exposure to air pollution on preterm birth (PTB) in Xiamen city from 2015 to 2018. Furthermore, the economic losses were assessed as well. Methods: Association of air pollution and PTB with economic losses were assessed using the generalized additive model. Results: A total of 1991 PTB visits, who are inhabitant in Xiamen, have been investigated. An interquartile range (IQR) (10 μg/m³) increase of PM₁₀, NO₂, and SO₂ in the current day corresponded to the increase of 0.64% [95% CI: -1.22, 2.54%], 0.52% [95% CI: -5.21, 6.61%], and 2.33% [95% CI: -6.41, 11.58%] in daily PTB visits. Especially, PTB visits were significantly related with PM₁₀ and NO₂ in Lag 1 and NO₂ and SO₂ in Lag 2. Furthermore, for multipollutants, an IQR increase in PM_2.5, O₃, and CO, after adjustment with SO₂, was related with 5.04% [95% CI: -5.90, 17.24], 2.49% [95% CI: -6.07, 11.81], and 7.10% [95% CI: -2.79, 18.00] increase of PTB morbidity, respectively. The estimates of the number of excess PTBs attributed to typical pollutants PM₁₀ and SO₂ were ∼2400 and 1200 people, respectively, every year. The highest excess PTBs was estimated to occur as a result of PM₁₀ and SO₂ effects. Conclusions: Although Xiamen has a relatively low level of air pollution, short-term exposure to NO₂, SO₂, and PM₁₀ was linked to the increase of PTB visits.

Combined effects of traffic air pollution and home environmental factors on preterm birth in China

BACKGROUND

Although mounting evidence have linked traffic-related air pollution (TRAP) with increased risk of preterm birth (PTB), whether it can interact with indoor environmental factors remains unknown, and its window(s) susceptibility at the stage of gestation is unclear.

OBJECTIVE

To explore PTB risk for prenatal exposure to traffic-related air pollution and home environmental factors during pregnancy, so as to identify critical window(s) in the combined effect of traffic air pollution and main home environmental factor(s) on PTB development.

METHODS

A retrospective cohort study of 3,509 preschool children was performed in Changsha, China during 2011-2012. The PTB prevalence was reported by the parents based on a questionnaire. We estimated each mother's exposure to traffic-related air pollutant NO₂ in different windows of gestation, including conception month, three trimesters, birth month, and whole gestation. Maternal exposure to home environmental factors was considered by renovation (new furniture/redecoration) in pregnancy, and mold/damp stains and window condensation during perinatal period. Associations of PTB with both ambient NO₂ and home environmental factors, and their interactions on PTB were evaluated by logistic regression models using odds ratio (OR) with 95% confidence interval (CI).

RESULTS

Traffic air pollutant NO₂ exposure in utero was significantly associated with PTB, with adjusted odds ratio (OR) (95% CI) of 1.41 (1.00-1.98) for an IQR increase in NO₂ exposure during whole pregnancy, particularly in the conception month and 1^st trimester. We further found a positive relationship between perinatal exposure to mold/damp stains in the homes and PTB, OR (95% CI) = 1.73 (1.04-2.90). Especially, we detected a significant interaction between outdoor NO₂ and indoor mold/damp stains on PTB risk. Male and female foetus were respectively more susceptible to perinatal mold/dampness at home and outdoor NO₂ exposure in early gestation.

CONCLUSION

Our finding indicates that both outdoor traffic air pollutant and indoor mold/dampness play key roles in PTB development, and their interaction effect in early pregnancy significantly increases PTB risk.

Maternal exposure to benzene and toluene and preterm birth. A longitudinal study

BACKGROUND

Exposure to air pollutants has several effects on human health, including during pregnancy.

OBJECTIVE

To identify whether exposure to benzene and toluene among pregnant women contributes to preterm delivery.

DESIGN AND SETTING

Longitudinal study using data on newborns from mothers living in São José dos Campos (SP) in 2016, who had been exposed to benzene and toluene.

METHODS

A logistic regression model with three hierarchical levels was constructed using maternal variables relating to newborns, and using benzene and toluene concentrations in quartiles. Occurrences of cesarean births, twins or malformations were excluded. Maternal exposure windows of 5, 10, 15, 30, 60 and 90 days prior to delivery were considered.

RESULTS

Out of the 9,562 live births, 3,671 newborns were included and 343 newborns were born at less than 37 weeks of gestation (9.3%). The average birth weight was 3,167.2 g. Exposure to benzene and toluene was significantly associated (P = 0.04) with preterm delivery in the five-day window. There was no association in any of the other exposure windows.

CONCLUSIONS

It was possible to identify that maternal exposure to benzene and toluene has an acute effect on preterm delivery.

Ambient Fine Particulate Matter and Preterm Birth in California: Identification of Critical Exposure Windows

Exposure to ambient fine particulate matter (particulate matter ≤2.5 μm in aerodynamic diameter (PM2.5)) during pregnancy is associated with preterm birth (PTB), a leading cause of infant morbidity and mortality. Results from studies attempting to identify etiologically relevant exposure periods of vulnerability have been inconsistent, possibly because of failure to consider the time-to-event nature of the outcome and lagged exposure effects of PM2.5. In this study, we aimed to identify critical exposure windows for weekly PM2.5 exposure and PTB in California using California birth cohort data from 2005-2010. Associations were assessed using distributed-lag Cox proportional hazards models. We assessed effect-measure modification by race/ethnicity by calculating the weekly relative excess risk due to interaction. For a 10-μg/m3 increase in PM2.5 exposure over the entire period of gestation, PTB risk increased by 11% (hazard ratio = 1.11, 95% confidence interval: 1.09, 1.14). Gestational weeks 17-24 and 36 were associated with increased vulnerability to PM2.5 exposure. We find that non-Hispanic black mothers may be more susceptible to effects of PM2.5 exposure than non-Hispanic white mothers, particularly at the end of pregnancy. These findings extend our knowledge about the existence of specific exposure periods during pregnancy that have the greatest impact on preterm birth.

Associations between ambient air pollution and pregnancy rate in women who underwent in vitro fertilization in Shenyang, China

To assess the associations between air pollution and the pregnancy rate of IVF, we performed a retrospective cohort study on 1455 women who underwent the first fresh IVF cycle at a fertility center from January 2014 to April 2018 and lived in Shenyang during treatment. Binary logistic regression models were used to evaluate the effect of an interquartile range increase in each pollutant on the intrauterine pregnancy rate. Both average chronic and daily acute exposure to air pollution were considered. Increased O₃ (adjusted OR = 0.87, 95% CI: 0.81, 0.98) during the period from gonadotropins starting to oocyte retrieval was associated with decreased probability of intrauterine pregnancy, especially the day before oocyte retrieval (adjusted OR = 0.86, 95% CI: 0.78, 0.95). Our results suggest that exposure to O₃ before oocyte retrieval has an adverse effect on intrauterine pregnancy. Future studies should be performed in order to confirm our findings.

Effect of ambient air pollution on premature SGA in Changzhou city, 2013-2016: a retrospective study

Background

Air pollution is becoming an increased burden to the world. Previous studies have confirmed its effects on adverse birth outcomes, but few associated with premature small for gestational age (SGA). We report a retrospective cohort study conducted in Changzhou city to evaluate the association between air pollutants (PM_2.5, SO₂ and NO₂) and premature SGA during pregnancy.

Methods

A total of 46,224 births were collected from January, 2013 to December, 2016, in Changzhou Maternity and Child Health Care Hospital, finally 2709 preterm births were admitted for study. Corresponding air monitoring data were collected from Changzhou Environmental Protection Agency. Generalized estimating equations were used to examine the association between these air pollutants and premature SGA controlling for individual covariates in single- and multi-pollutant models.

Results

We found that, in the third trimester, every 10 μg/m³ increments in PM_2.5 concentration were associated with premature SGA (OR = 1.18, 95% CI: 1.03–2.83; OR = 1.37, 95% CI: 1.03–3.58) in two- and three-pollutants models. In the whole gestation, a 10 μg/m³ increment in PM_2.5 concentration in two- and three-pollutant models were related to premature SGA (OR = 1.53, 95% CI: 1.38–2.47; OR = 1.73, 95% CI: 1.18–2.57). The OR (95% CI) of premature SGA were increasing across quintiles of PM_2.5, SO₂, NO₂ concentrations during the whole gestation period adjusting for confounders (P_{for trend} < 0.001).

Conclusions

These results indicated that pregnant women exposed to PM_2.5, combined with other pollutants in the third trimester have a higher risk to deliver premature SGA babies, providing further evidence linking PM_2.5 and pregnancy outcomes.

Ambient PM2.5 and clinically recognized early pregnancy loss: A case-control study with spatiotemporal exposure predictions

BACKGROUND

Experimental research suggests that fine particulate matter (PM_2.5) exposure might affect embryonic development. However, only few population-based studies have investigated the impact of maternal exposure to PM_2.5 on the early pregnancy loss.

OBJECTIVES

To estimate associations between clinically recognized early pregnancy loss (CREPL) and exposure to ambient PM_2.5 at individual residences during peri-conception periods, with the aim to identify susceptible exposure time windows.

METHODS

CREPL cases and normal early pregnancy controls (of similar age and gravidity presenting within one week, a total of 364 pairs) were recruited between July 2017 and July 2018 among women residing in Tianjin, China. Average ambient PM_2.5 concentrations of ten exposure windows (4 weeks, 2 weeks and 1 week before conception; the first, second, third and fourth single week, the first and second 2-week periods, and the entire 4-week period after conception) at the women's residential addresses were estimated using temporally-adjusted land use regression models. Associations between PM_2.5 exposures at specific peri-conception time windows and CREPL were examined using conditional logistic regression models, adjusted for covariates.

RESULTS

Based on adjusted models, CREPL was significantly associated with a 10 μg/m³ increase in PM_2.5 exposure during the second week after conception (OR = 1.15; 95% CI: 1.04, 1.27; p = 0.005), independent of effects at other time windows. There was also an association of CREPL with PM_2.5 during the entire 4-week period after conception (OR = 1.22; 95% CI: 1.02, 1.46; p = 0.027). There was little evidence for associations with exposure during pre-conception exposure windows.

CONCLUSIONS

Maternal exposures to ambient PM_2.5 during a critical time window following conception are associated with CREPL, with the second week after conception possibly being the exposure window of most vulnerability. Future studies should focus on replicating these findings and on pathogenic mechanisms.

A comprehensive evaluation of the association between ambient air pollution and adverse health outcomes of major organ systems: a systematic review with a worldwide approach

Ambient air pollution is nowadays one of the most crucial contributors to deteriorating health status worldwide. The components of air pollution include PM_2.5 and PM₁₀, NO₂, SO₂, CO, O₃, and organic compounds. They are attributed to several health outcomes, for instance, cardiovascular diseases (CVD), respiratory diseases, birth outcomes, neurologic diseases, and psychiatric diseases. The objective of this study is to evaluate the association between different ambient air pollutants and the above-mentioned health outcomes. In this systematic review, a total of 76 articles was ultimately selected from 2653 articles, through multiple screening steps by the aid of a set of exclusion criteria as non-English articles, indoor air pollution assessment, work-related, occupational and home-attributed pollution, animal studies, tobacco smoking effects, letters to editors, commentaries, animal experiments, reviews, case reports and case series, out of 19,862 published articles through a systematic search in PubMed, Web of Science, and Scopus. Then, the associations between air pollution and different health outcomes were measured as relative risks and odds ratios. The association between air pollutants, PM_2.5 and PM₁₀, NO₂, SO₂, CO, O₃, and VOC with major organ systems health was investigated through the gathered studies. Relative risks and/or odds ratios attributed to each air pollutant/outcome were ultimately reported. In this study, a thorough and comprehensive discussion of all aspects of the contribution of ambient air pollutants in health outcomes was proposed. To our knowledge up to now, there is no such comprehensive outlook on this issue. Growing concerns in concert with air pollution-induced health risks impose a great danger on the life of billions of people worldwide. Should we propose ideas and schemes to reduce ambient air pollutant, there will be dramatic reductions in the prevalence and occurrence of health-threatening conditions.

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.

Impact of air pollution on low birth weight in Spain: An approach to a National Level Study

BACKGROUND

According to the WHO, low birth weight (<2500 gr) is a primary maternal health indicator as the cause of multiple morbi-mortality in the short and long-term. It is known that air pollution from road traffic (PM₁₀, NO₂) and O₃ have an important impact on low birth weight (LBW), but there are few studies of this topic in Spain. The objective of this study is to determine the possible exposure windows in the gestational period in which there is greater susceptibility to urban air pollution and to quantify the relative risks (RR) and population attributable risks (PAR) of low birth weight associated with pollutant concentrations in Spain.

METHODS

We calculated the weekly average births with low birth weight (ICD-10: P07.0-P07.1) for each Spanish province for the period 2001-2009, using the average weekly concentrations of PM₁₀, NO₂ and O₃, measured in the capital cities of the provinces. The estimation of RR and PAR were carried out using generalized linear models with link Poisson, controlling for the trend, seasonality and auto-regressive character of the series and for the influence of temperature during periods of heat waves and/or cold. Finally, a meta-analysis was used to estimate the global RR and PAR based on the RR obtained for each of the provinces.

RESULTS

The RR for the whole of Spain is 1.104 (CI95%: 1.072, 1.138) for the association between LBW and PM₁₀, and 1.091 (CI95%: 1.059, 1.124) for the association between NO₂ and LBW. Our results suggest that 5% of low birth weight births in the case of PM₁₀ and 8% in the case of NO₂ could have been avoided with a reduction of 10 μg/m³ in the concentrations of these pollutants.

CONCLUSIONS

The impact of the results obtained- with 6105 cases attributable to PM₁₀ and up to 9385 cases attributable to NO₂ in a period of 9 study years- suggest the need to design structural and awareness public health measures to reduce air pollution in Spain.

Environmental Contaminants Exposure and Preterm Birth: A Systematic Review

Preterm birth is an obstetric condition associated with a high risk of infant mortality and morbidities in both the neonatal period and later in life, which has also a significant public health impact because it carries an important societal economic burden. As in many cases the etiology is unknown, it is important to identify environmental factors that may be involved in the occurrence of this condition. In this review, we report all the studies published in PubMed and Scopus databases from January 1992 to January 2019, accessible as full-text articles, written in English, including clinical studies, original studies, and reviews. We excluded articles not written in English, duplicates, considering inappropriate populations and/or exposures or irrelevant outcomes and patients with known risk factors for preterm birth (PTB). The aim of this article is to identify and summarize the studies that examine environmental toxicants exposure associated with preterm birth. This knowledge will strengthen the possibility to develop strategies to reduce the exposure to these toxicants and apply clinical measures for preterm birth prevention.

Nitrogen dioxide air pollution and preterm birth in Shanghai, China

BACKGROUND

Nitrogen dioxide (NO₂) is a typical indicator of traffic-related air pollution, and few studies with exposure assessment of high resolution have been conducted to explore its association with preterm birth in China.

OBJECTIVES

To investigate the association between NO₂ exposure based on a land use regression (LUR) model and preterm birth in Shanghai, China.

METHODS

A retrospective cohort study was performed among 25,493 singleton pregnancies in a major maternity hospital in Shanghai, China, from 2014 to 2015. A temporally adjusted LUR model was used to predict the prenatal exposure to NO₂ based on residence address of each gravida. Logistic regression was performed to evaluate the associations of ambient NO₂ exposure with preterm birth during six exposure periods, including the entire pregnancy, the first trimester, the second trimester, the third trimester, the last month, and the last week before delivery. Sensitivity analysis with a matched case-control design was conducted to test the robustness of the association between NO₂ exposure and preterm birth.

RESULTS

The average NO₂ concentrations during the entire pregnancy was 48.23 µg/m³ among all participants. A 10 µg/m³ increase in NO₂ concentrations was associated with preterm birth, with an adjusted odds ratio of 1.03 (95% confidence interval [CI]: 0.96,1.10) for exposures during the entire pregnancy, 1.00 (95%CI: 0.95,1.06) in the first trimester, 1.01 (95%CI: 0.96,1.07) in the second trimester, 1.07 (95%CI: 1.02,1.13) in the third trimester, 1.10 (95%CI: 1.04,1.15) and 1.05 (95%CI: 1.00,1.09) in the month and week before delivery, respectively. The results of the matched case-control analysis were generally consistent with those of main analyses.

CONCLUSION

NO₂ may increase the risk of preterm birth, especially for exposures during the third trimester, the month and the week before delivery in Shanghai, China.

The association of early-life exposure to air pollution with lung function at ~17.5 years in the "Children of 1997" Hong Kong Chinese Birth Cohort

BACKGROUND

Early-life air pollution exposure is associated with lung function in children and adolescents. However, whether the association of prenatal and early postnatal exposure to air pollution with lung function continues into adulthood remains unclear.

OBJECTIVE

To investigate the associations of early exposure to air pollution with lung function at ~17.5 years in a non-western developed setting with more concentrated air pollutants.

METHODS

We examined the associations of exposure to particular matter with an aerodynamic diameter of <10 μm (PM₁₀), nitrogen dioxides (NO₂), nitric oxide (NO), sulfur dioxide (SO₂) in standard deviations (SD)) at different early life stages with lung function (indicated by forced vital capacity (FVC), forced expiratory volume in 1 s (FEV₁) and forced expiratory flow at 25%-75% of the pulmonary volume (FEF_25%-75%)) in SD at ~17.5 years, personal history of wheezing and asthma in the population-representative Hong Kong Chinese birth cohort "Children of 1997"(n = 2942).

RESULTS

Higher in utero and infancy and toddlerhood NO₂ were associated with lower FEV₁ (-0.022, 95% confidence interval (CI) -0.029 to -0.015 and - 0.026, 95% CI -0.033 to -0.019), FEV₁/FVC (-0.035, 95% CI -0.050 to -0.021 and -0.052, 95% CI -0.066 to -0.038) and FEF_25%-75% (-0.031, 95% CI -0.040 to -0.022 and -0.043, 95% CI -0.051 to -0.035). A similar association was observed for NO. Weak associations of NO₂ and NO with FVC were observed (-0.011, 95% CI -0.018 to -0.003 and -0.010, 95% CI -0.020 to -0.001). NO_x was associated with higher risk of wheezing (1.08, 95% CI 1.03 to 1.14) but not asthma (1.02, 95% CI 0.94 to 1.11). SO₂ and PM₁₀ were not clearly associated with lung function, wheezing or asthma.

CONCLUSION

Our findings suggest that early exposure to air pollution from NO₂ may have long-term effects on lung function, which could affect respiratory health throughout life.

Assessing the Impact of Vehicle Speed Limits and Fleet Composition on Air Quality Near a School

Traffic is a major source of urban air pollution that affects health, especially among children. As lower speed limits are commonly applied near schools in many cities, and different governments have different policies on vehicle fleet composition, this research estimated how different speed limits and fleet emissions affect air quality near a primary school. Based on data of traffic, weather, and background air quality records in Dublin from 2013, traffic, emission, and dispersion models were developed to assess the impact of different speed limits and fleet composition changes against current conditions. Outside the school, hypothetical speed limit changes from 30 km/h to 50 km/h could reduce the concentration of NO₂ and PM₁₀ by 3% and 2%; shifts in the fleet from diesel to petrol vehicles could reduce these pollutants by 4% and 3% but would increase the traffic-induced concentrations of CO and Benzene by 63% and 35%. These changes had significantly larger impacts on air quality on streets with higher pollutant concentrations. Findings suggest that both road safety and air quality should be considered when determining speed limits. Furthermore, fleet composition has different impacts on different pollutants and there are no clear benefits associated with incentivising either diesel or petrol engine vehicles.

Using a Clustering Approach to Investigate Socio-Environmental Inequality in Preterm Birth-A Study Conducted at Fine Spatial Scale in Paris (France)

Background & Objectives: Today, to support public policies aiming to tackle environmental and health inequality, identification and monitoring of the spatial pattern of adverse birth outcomes are crucial. Spatial identification of the more vulnerable population to air pollution may orient health interventions. In this context, the objective of this study is to investigate the geographical distribution of the risk of preterm birth (PTB, gestational age ≤36 weeks) at the census block level in in city of Paris, France. We also aimed to assess the implication of neighborhood characteristics including air pollution and socio-economic deprivation. Material & Methods: Newborn health data are available from the first birth certificate registered by the Maternal and Child Care department of Paris. All PTB from January 2008 to December 2011 were geocoded at the mother residential census block. Each census block was assigned a socioeconomic deprivation level and annual average ambient concentrations of NO₂. A spatial clustering approach was used to investigate the spatial distribution of PTB. Results: Our results highlight that PTB is non-randomly spatially distributed, with a cluster of high risk in the northeastern area of Paris (RR = 1.15; p = 0.06). After adjustment for socio-economic deprivation and NO₂ concentrations, this cluster becomes not statistically significant or shifts suggesting that these characteristics explain the spatial distribution of PTB; further, their combination shows an interaction in comparison with SES or NO₂ levels alone. Conclusions: Our results may inform the decision makers about the areas where public health efforts should be strengthened to tackle the risk of PTB and to choose the most appropriate and specific community-oriented health interventions.

Maternal air pollution exposure and preterm birth in Wuxi, China: Effect modification by maternal age

BACKGROUND

Numerous studies have investigated prenatal air pollution and shown that air pollutants have adverse effect on birth outcomes. However, which trimester was the most sensitive and whether the effect was related to maternal age is still ambiguous.

OBJECTIVES

This study aims to explore the association between maternal air pollution exposure during pregnancy and preterm birth, and if this relationship is modified by maternal age.

METHODS

In this retrospective cohort study, we examine the causal relationship of prenatal exposure to air pollutants including particulate matters, which are less than 10 µm (PM₁₀), and ozone (O₃), which is one of the gaseous pollutants, on preterm birth by gestational age. A total of 6693 pregnant women were recruited from Wuxi Maternal and Child Health Care Hospital. The participants were dichotomized into child-bearing age group (< 35 years old) and advanced age group (> = 35 years old) in order to analyze the effect modification by maternal age. Logistic and linear regression models were performed to assess the risk for preterm birth (gestational age < 37 weeks) caused by prenatal air pollution exposure.

RESULTS

With adjustment for covariates, the highest level of PM₁₀ exposure significantly increased the risk of preterm birth by 1.42-fold (95% CI: 1.10, 1.85) compared those with the lowest level in the second trimester. Trimester-specific PM₁₀ exposure was positively associated with gestational age, whereas O₃ exposure was associated with gestational age in the early pregnancy. When stratified by maternal age, PM₁₀ exposure was significantly associated with an increased risk of preterm birth only in the advanced age group during pregnancy (OR:2.15, 95% CI: 1.13, 4.07). The results suggested that PM₁₀ exposure associated with preterm birth was modified by advanced maternal age (OR _interaction = 2.00, 95% CI: 1.02, 3.91, P_interaction = 0.032).

CONCLUSION

Prenatal air pollution exposure would increase risk of preterm birth and reduced gestational age. Thus, more attention should be paid to the effects of ambient air pollution exposure on preterm birth especially in pregnant women with advanced maternal age.

An epidemiological assessment of the effect of ambient temperature on the incidence of preterm births: Identifying windows of susceptibility during pregnancy

It is well known that exposure to thermal stress during pregnancy can lead to an increased incidence of premature births. However, there is little known regarding window(s) of susceptibility during the course of a pregnancy. We attempted to identify possible windows of susceptibility in a cohort study of 3604 children in Changsha with a hot-summer and cold winter climatic characteristics. We examined the association between PTB and ambient temperature during different timing windows of pregnancy: conception month, three trimesters, birth month and entire pregnancy. We found a U-shaped relation between the prevalence of PTB and mean ambient temperature during pregnancy. Both high and low temperatures were associated with PTB risk, adjusted OR (95% CI) respectively 2.57 (1.98-3.33) and 2.39 (1.93-2.95) for 0.5 °C increase in high temperature range (>18.2°C) and 0.5°C decrease in low temperature range (< 18.2°C). Specifically, PTB was significantly associated with ambient temperature and extreme heat/cold days during conception month and the third trimester. Sensitivity analysis indicated that female fetus were more susceptible to the risk of ambient temperature. Our study indicates that the risk of preterm birth due to high or low temperature may exist early during the conception month.

Effectiveness of a theory-based mobile phone text message intervention for improving protective behaviors of pregnant women against air pollution: a randomized controlled trial

Health impact of exposure to air pollution is a public health concern. The aim of this study was to investigate an extended parallel process model (EPPM)-based mobile phone text message intervention for improving protective behaviors against air pollution among pregnant women. In this randomized controlled trial (IRCT2016102810804N8), 130 pregnant women were randomly assigned into either experimental or control groups. A valid and reliable questionnaire was used to collect data. Experimental group received mobile phone intervention on a daily basis for 2 months. Control group received usual care, only. Data were analyzed using SPSS 15 applying t test, chi-square, and Wilcoxon and Mann-Whitney U test. Although before intervention, there were no significant differences between different structures of EPPM (P > 0.05), after intervention, there were statistically significant differences between perceived severity, response efficacy, self-efficacy, and protective behaviors between two groups (P < 0.05). Implementing EPPM based-mobile phone intervention could promote protective behaviors against air pollution among pregnant women. The present study might be used as a framework for evidence-based health promotion regarding air pollution risk communication and self-care behaviors.

TRIAL REGISTRATION

IRCT2016102810804N8.

Ambient air pollution the risk of stillbirth: A prospective birth cohort study in Wuhan, China

BACKGROUND

Recent studies suggest that ambient air pollution exposure during pregnancy is associated with stillbirth occurrence. However, the results on the associations between ambient air pollutants and stillbirths are inconsistent and little is known about the gestational timing of sensitive periods for the effects of ambient air pollutants exposure on stillbirth.

OBJECTIVE

This study aimed to examine whether exposure to high levels of ambient air pollutants in a Chinese population is associated with an increased risk of stillbirth, and determine the gestational period when the fetus is most susceptible.

METHODS

We conducted a population-based cohort study in Wuhan, China, involving 95,354 births between June 10, 2011 and June 9, 2013. The exposure assessments were based on the daily mean concentrations of air pollutants obtained from the exposure monitor nearest to the pregnant women's residence. Logistic regression analyses were performed to determine the associations between stillbirths and exposure to each of the air pollutants at different pregnancy periods with adjustment for confounding factors.

RESULTS

Stillbirth increased with a 10 μg/m³ increase in particulate matter 2.5 (PM_2.5) in each stage of pregnancy, and a significant association between carbon monoxide (CO) exposure and stillbirth was found during the third trimester (adjusted odds ratio (aOR): 1.01, 95% confidence interval (CI): 1.00-1.01) and in the entire pregnancy (aOR: 1.18, 95% CI: 1.04-1.34). Furthermore, an increased risk of stillbirth in the third trimester was associated with a 10 μg/m³ increase in PM₁₀ (aOR: 1.08, 95% CI: 1.04-1.11), nitrogen dioxide (NO₂) (aOR: 1.13, 95% CI: 1.07-1.21) and sulfur dioxide (SO₂) (aOR: 1.26, 95% CI: 1.16-1.35). However, no positive association was observed between ozone exposure and stillbirth. In the two-pollutant models, PM_2.5 and CO exposures were found to be consistently associated with stillbirth.

CONCLUSIONS

Our study revealed that exposure to high levels of PM_2.5, PM₁₀, SO₂, NO₂ and CO increases the risk of stillbirth and the most susceptible gestational period to ambient air pollution exposure was in the third trimester. Further toxicological and prospective cohort studies with improved exposure assessments are needed to confirm the causal link between air pollutants and stillbirth.

The association between cooking oil fume exposure during pregnancy and birth weight: A prospective mother-child cohort study

Effects of indoor air pollution on neonatal birth weight has been studied for many years. In China, cooking oil fumes are important parts of indoor air pollution. However, whether cooking oil fume exposure during pregnancy affects birth weight in China remains poorly understood. The objective of this study was to examine the association between pregnancy exposure to cooking oil fumes and birth weight in a newly established prospective mother-child cohort in China. We finally included 1420 pregnant women from 2013 to 2015 and follow up for one year until the offspring was born. According to self-reported exposure status, we categorized mothers into non-exposure group and exposed group or three exposure time subgroups, including 0h/day, 0-1h/day and >1h/day respectively. By using multinomial logistics regression models, we found that pregnancy exposure to cooking oil fumes significantly increased the risk of large for gestational age (LGA, OR=1.58, 95% CI=1.15-2.18, P=4.88×10^-3). Additionally, compared to pregnant women who were in non-exposure group, 0-1h/day exposure elevated the risk of LGA (OR=1.69, 95% CI=1.22-2.33, P=1.63×10^-3), while >1h/day exposure elevated the risk of small for gestational age, but were not significant (SGA, OR=2.15, 95% CI=0.61-7.66, P=0.24). In the stratification analysis, women aged 25-29years and ≥30years were predisposed to the influence of cooking oil fumes and have LGA newborns (OR=1.73, 95% CI=1.09-2.75, P=0.02; OR=1.72, 95% CI=1.07-2.77, P=0.02, respectively). In conclusion, the present study suggests inverse U-shape dose response association between maternal exposure to cooking oil fumes during pregnancy and birth weight, and further studies are needed to verify the effect of cooking oil fumes on the birth weight.

Temperature exposure during pregnancy and birth outcomes: An updated systematic review of epidemiological evidence

Seasonal patterns of birth outcomes have been observed worldwide, and there was increasing evidence that ambient temperature played as a trigger of adverse birth outcomes, such as preterm birth (PTB), low birth weight (LBW), and stillbirth. To systematically review updated epidemiological evidence about the relationship between temperature exposure during pregnancy and PTB, LBW, and stillbirth, we searched for related studies published in English from electronic databases and references of identified papers. We only included original articles that directly reported the effects of prenatal temperature exposure on birth outcomes. The characteristics and main findings of included studies were examined. A total of 36 epidemiological studies were finally included in this review. Most of these studies focused on PTB and LBW, while less attention has been paid to stillbirth that was relatively rare in the occurrence. Several designs including ecological (e.g., descriptive and time-series) and retrospective cohort studies (e.g., case-crossover and time-to-event) were applied to assess temperature effects on birth outcomes. Temperature metrics and exposure windows varied greatly in these investigations. Exposure to high temperature was generally found to be associated with PTB, LBW, and stillbirth, while several studies also reported the adverse impact of low temperature on birth outcomes of PTB and LBW. Despite no conclusive causality demonstrated, the current evidence for adverse effect on birth outcomes was stronger for heat than for cold. In summary, the evidence linking birth outcomes with ambient temperature was still very limited. Consequently, more related studies are needed worldwide and should be conducted in diversified climate zones, so as to further ascertain the association between temperature and birth outcomes. Future studies should focus on more sophisticated study designs, more accurate estimation of temperature exposure during pregnancy, and more efficient methods to find out the exposure windows, as well as cold-related effects on birth outcomes.

Environmental chemicals and preterm birth: Biological mechanisms and the state of the science

PURPOSE OF REVIEW

Preterm birth is a significant worldwide health problem of uncertain origins. The extant body of literature examining environmental contaminant exposures in relation to preterm birth is extensive but results remain ambiguous for most organic pollutants, metals and metalloids, and air pollutants. In the present review we examine recent epidemiologic studies investigating these associations, and identify recent advances and the state of the science. Additionally, we highlight biological mechanisms of action in the pathway between chemical exposures and preterm birth, including inflammation, oxidative stress, and endocrine disruption, that deserve more attention in this context.

RECENT FINDINGS

Important advances have been made in the study of the environment and preterm birth, particularly in regard to exposure assessment methods, exploration of effect modification by co-morbidities and exposures, and in identification of windows of vulnerability during gestation. There is strong evidence for an association between maternal exposure to some persistent pesticides, lead, and fine particulate matter, but data on other contaminants is sparse and only suggestive trends can be noted with the current data.

SUMMARY

Beyond replicating current findings, further work must be done to improve understanding of mechanisms underlying the associations observed between environmental chemical exposures and preterm birth. By examining windows of vulnerability, disaggregating preterm birth by phenotypes, and measuring biomarkers of mechanistic pathways in these epidemiologic studies we can improve our ability to detect associations with exposure, provide additional evidence for causality in an observational setting, and identify opportunities for intervention.

Early-life exposure to air pollution and greater use of academic support services in childhood: a population-based cohort study of urban children

BACKGROUND

There is a growing literature showing associations between prenatal and early-life exposure to air pollution and children's neurodevelopment. However, it is unclear if decrements in neurodevelopment observed in epidemiologic research translate into observable functional outcomes in the broader pediatric population. The objective of this study was to examine the association between early-life exposures to common urban air toxics and the use of academic support services, such as early intervention and special education within a population-based cohort of urban children.

METHODS

Data for 201,559 children born between 1994 and 1998 in New York City were obtained through administrative data linkages between birth, early intervention and educational records. Use of academic support services was ascertained from birth through attendance in 3rd grade. Census tract at birth was used to assign estimates of annual average ambient concentrations of benzene, toluene, ethylbenzene and xylenes (BTEX) using the 1996 National Air Toxics Assessment. Discrete-time hazard models were fit to the data and adjusted for confounders including maternal, childhood and neighborhood factors.

RESULTS

Children with higher exposures to BTEX compounds were more likely to receive academic support services later in childhood. For example, the adjusted hazard ratio comparing children exposed to the highest decile of benzene to those with lower exposure was 1.09 (95% confidence interval 1.05, 1.13). Results were consistent across individual BTEX compounds, for exposure metrics which summarized exposure to all four BTEX pollutants and for multiple sensitivity analyses.

CONCLUSIONS

These findings suggest urban air pollution may affect children's neurodevelopment and educational trajectories. They also demonstrate the use of public health data systems to advance children's environmental health research.

Air pollution during pregnancy and lung development in the child

Air pollution exposure has increased extensively in recent years and there is considerable evidence that exposure to particulate matter can lead to adverse respiratory outcomes. The health impacts of exposure to air pollution during the prenatal period is especially concerning as it can impair organogenesis and organ development, which can lead to long-term complications. Exposure to air pollution during pregnancy affects respiratory health in different ways. Lung development might be impaired by air pollution indirectly by causing lower birth weight, premature birth or disturbed development of the immune system. Exposure to air pollution during pregnancy has also been linked to decreased lung function in infancy and childhood, increased respiratory symptoms, and the development of childhood asthma. In addition, impaired lung development contributes to infant mortality. The mechanisms of how prenatal air pollution affects the lungs are not fully understood, but likely involve interplay of environmental and epigenetic effects. The current epidemiological evidence on the effect of air pollution during pregnancy on lung function and children's respiratory health is summarized in this review. While evidence for the adverse effects of prenatal air pollution on lung development and health continue to mount, rigorous actions must be taken to reduce air pollution exposure and thus long-term respiratory morbidity and mortality.

Effect of Environmental Factors on Low Weight in Non-Premature Births: A Time Series Analysis

OBJECTIVE

Exposure to pollutants during pregnancy has been related to adverse birth outcomes. LBW can give rise to lifelong impairments. Prematurity is the leading cause of LBW, yet few studies have attempted to analyse how environmental factors can influence LBW in infants who are not premature. This study therefore sought to analyse the influence of air pollution, noise levels and temperature on LBW in non-premature births in Madrid during the period 2001-2009.

METHODS

Ecological time-series study to assess the impact of PM2.5, NO2 and O3 concentrations, noise levels, and temperatures on LBW among non-premature infants across the period 2001-2009. Our analysis extended to infants having birth weights of 1,500 g to 2,500 g (VLBW) and less than 1,500 g (ELBW). Environmental variables were lagged until 37 weeks with respect to the date of birth, and cross-correlation functions were used to identify explaining lags. Results were quantified using Poisson regression models.

RESULTS

Across the study period 298,705 births were registered in Madrid, 3,290 of which had LBW; of this latter total, 1,492 were non-premature. PM2.5 was the only pollutant to show an association with the three variables of LBW in non-premature births. This association occurred at around the third month of gestation for LBW and VLBW (LBW: lag 23 and VLBW: lag 25), and at around the eighth month of gestation for ELBW (lag 6). Leqd was linked to LBW at lag zero. The RR of PM2.5 on LBW was 1.01 (1.00 1.03). The RR of Leqd on LBW was 1.09 (0.99 1.19)(p<0.1).

CONCLUSIONS

The results obtained indicate that PM2.5 had influence on LBW. The adoption of measures aimed at reducing the number of vehicles would serve to lower pregnant women's exposure. In the case of noise should be limited the exposure to high levels during the final weeks of pregnancy.