The association of air pollution with congenital anomalies: An exploratory study in the northern Netherlands

Maternal PM2.5 exposure and hypospadias risk in Chinese offspring: Insights from a nationwide surveillance-based study

Research on the association between maternal PM2.5 exposure and hypospadias risk in male offspring, particularly in highly polluted areas, has been limited and inconsistent. This study leveraged data from China's National Population-based Birth Defects Surveillance System spanning the years 2013 to 2019, and employed sophisticated machine learning models to estimate daily PM2.5 levels and other pollutants for mothers at a 1-km resolution and a 6-km buffer surrounding maternal residences. Multivariate logistic regression analyses were performed to evaluate the relationship between PM2.5 exposure and hypospadias risk. For sensitivity analyses, stratification analysis was conducted, and models for one-pollutant and two-pollutants, as well as distributed lag nonlinear models, were constructed. Of the 1194,431 boys studied, 1153 cases of hypospadias were identified. A 10 μg/m3 increase in maternal PM2.5 exposure during preconception and the first trimester was associated with an elevated risk of isolated hypospadias, with Odds Ratios (ORs) of 1.102 (95% CI: 1.023-1.188) and 1.089 (95% CI: 1.007-1.177) at the 1-km grid, and 1.122 (95% CI: 1.034-1.218) and 1.143 (95% CI: 1.048-1.246) within the 6-km buffer. Higher quartiles of PM2.5 exposure were associated with increased odds ratios compared to the lowest quartile. These findings highlight a significant association between PM2.5 exposure during the critical conception period and an elevated risk of isolated hypospadias in children, emphasizing the need for targeted interventions to reduce PM2.5 exposure among expectant mothers.

Association between usage of household cooking fuel and congenital birth defects-18 months multi-centric cohort study in Nepal

BACKGROUND

- An estimated 240,000 newborns die worldwide within 28 days of birth every year due to congenital birth defect. Exposure to poor indoor environment contributes to poor health outcomes. In this research, we aim to evaluate the association between the usage of different type household cooking fuel and congenital birth defects in Nepal, as well as investigate whether air ventilation usage had a modifying effect on the possible association.

METHODS

- This is a secondary analysis of multi-centric prospective cohort study evaluating Quality Improvement Project in 12 public referral hospitals of Nepal from 2017 to 2018. The study sample was 66,713 women with a newborn, whose information was available in hospital records and exit interviews. The association between cooking fuel type usage and congenital birth defects was investigated with adjusted multivariable logistic regression. To investigate the air ventilation usage, a stratified multivariable logistic regression analysis was performed.

RESULTS

-In the study population (N = 66,713), 60.0% used polluting fuels for cooking and 89.6% did not have proper air ventilation. The prevalence rate of congenital birth defect was higher among the families who used polluting fuels for cooking than those who used cleaner fuels (5.5/1000 vs. 3.5/1000, p < 0.001). Families using polluting fuels had higher odds (aOR 1.49; 95% CI; 1.16, 1.91) of having a child with a congenital birth defect compared to mothers using cleaner fuels adjusted with all available co-variates. Families not using ventilation while cooking had even higher but statistically insignificant odds of having a child with congenital birth defects (aOR 1.34; 95% CI; 0.86, 2.07) adjusted with all other variates.

CONCLUSION

- The usage of polluted fuels for cooking has an increased odds of congenital birth defects with no significant association with ventilation. This study adds to the increasing knowledge on the adverse effect of polluting fuels for cooking and the need for action to reduce this exposure.

Maternal exposure to particulate matter early in pregnancy and congenital anomalies in offspring: Analysis of concentration-response relationships in a population-based cohort with follow-up throughout childhood

Studies have suggested an association between particulate matter (PM) air pollution and certain congenital anomalies (CAs). However, most studies assumed a linear concentration-response relation and were based on anomalies that were ascertained at birth or up to 1 year of age. We investigated associations between exposures to PM during the first trimester of pregnancy and CAs in 9 organ systems using birth and childhood follow-up data from a leading health care provider in Israel. We conducted a retrospective population-based cohort study among 396,334 births, 2004-2015. Daily PM data at a 1 × 1 km spatial grid were obtained from a satellite-derived prediction models and were linked to the mothers' residential addresses at birth. Adjusted odds ratios (ORs) were estimated with logistic regression models using exposure levels as either continuous or categorical variables. We captured 57,638 isolated CAs with estimated prevalence of 96 and 136 anomalies per 1000 births in the first year of life and by age 6 years, respectively. Analysis of continuous PM with diameter < 2.5 μm (PM_2.5) indicated a supra-linear relation with anomalies in the circulatory, respiratory, digestive, genital and integument systems (79 % of CAs). The slope of the concentration-response function was positive and steepest for PM_2.5 lower than the median concentration (21.5 μg/m³) and had a less steep or negative slope at higher levels. Similar trends were observed for PM_2.5 quartiles. For example, for cardiac anomalies, the ORs were 1.09 (95 % confidence interval: 1.02, 1.15), 1.04 (0.98, 1.10) and 1.00 (0.94, 1.07) for births in the second, third and fourth quartiles, respectively, when compared to the first quartile. In sum, this study adds new evidence for adverse effects of air pollution on neonatal health even with low-level air pollution. Information on late diagnosis of children with anomalies is important in evaluating the burden of disease.

Green space, air pollution and gestational diabetes mellitus: A retrospective cohort study in central China

Emerging evidence suggests residential surrounding green space is beneficial for human health. The association between green space and GDM showed inconsistent results, and potential effect modification of green space with air pollution is still unclear. This study aims to evaluate the association between green space and GDM, and further explore potential interaction and medication effects. Participants were recruited from a retrospective cohort study between 2015 and 2020 in Henan, China. Residential green space based on normalized difference vegetation index (NDVI) and air pollution exposure were estimated using spatial-statistical models. Multivariate logistic regression was applied to evaluate the association between per 0.1 unit increase in NDVI with 4 buffer sizes (250 m, 500 m, 1000 m, 2000 m) and GDM. We examined potential interaction of green space and air pollutants on GDM. Mediating effects of air pollution associated with green space exposure on GDM were also investigated by causal mediation analyses. A total of 46,665 eligible pregnant women were identified. There were 4092 (8.8 %) women diagnosed with GDM according to the IADPSG criteria. We found that per 0.1-unit increment in NDVI250 m, NDVI500 m, NDVI1000 m and NDVI2000 m in second trimester were associated with the decreased risk of GDM, with adjusted OR of 0.921(95 %CI: 0.890-0.953), 0.922 (95 %CI: 0.891-0.953), 0.921 (95 %CI: 0.892-0.952) and 0.921 (95 %CI: 0.892-0.951), respectively. We identified significant interactions between second trimester PM2.5 and O3 exposure and NDVI for GDM (Pinteraction < 0.001). The causal mediation analysis showed that PM2.5 mediated approximately 2.5-5.5 % of the association between green space and GDM, while the estimated mediating effect of O3 was approximately 30.1-38.5 %. In conclusion, our study indicates that residential green space was associated with a reduced risk of GDM, particularly second trimester. Green space may benefit to GDM partly mediated by a reduction in PM2.5 and O3.

Time series analysis on association between ambient air pollutants and orofacial clefts during pregnancy in Lanzhou, China

Current studies on air pollutant exposure during pregnancy and orofacial clefts (OFCs) have inconsistent results, and few studies have investigated refined susceptible windows for OFCs. We aim to estimate association between air pollution and OFCs during the first trimester of pregnancy and identify specific susceptible windows. Birth data was obtained from Birth Defects Surveillance Network in Lanzhou from 2014 to 2019. Air pollution data and temperature data were obtained from ambient air monitoring stations and China Meteorological Data Network, respectively. A distribution lag nonlinear model (DLNM) was applied to estimate weekly-exposure-lag-response association between air pollutant levels and OFCs. The study included 320,787 perinatal infants from 2014 to 2019, of which 685 (2.14‰) were OFCs. The results demonstrated that exposure of pregnant women to aerodynamic diameter ≤ 10 μm (PM₁₀) at lag 4-5 weeks was significantly associated with the risk of OFCs, with the greatest impact at the lag 4 week (RR = 1.029, 95% CI = 1.001-1.057). Exposure to sulfur dioxide (SO₂) at lag 2-4 weeks was significantly associated with the risk of OFCs, with the greatest impact at the lag 3 week (RR = 1.096, 95% CI = 1.041-1.177). This study provides further evidence that exposure to air pollution increases the risk of OFCs in the first trimester of pregnancy.

Exposure to air pollution is associated with congenital anomalies in the population born by in vitro fertilization

BACKGROUND

Congenital anomalies (CAs) are the leading causes for children's disabilities and mortalities worldwide. The associations between air pollution and CAs are not fully characterized in fetuses born by in vitro fertilization (IVF) who are at high risk of congenital anomalies.

METHODS

We conducted a cross-sectional study including 16,971 IVF cycles from three hospitals in Hebei Province, China, 2014-2019. Air quality data was obtained from 149 air monitoring stations. Individual average daily concentrations of PM_2.5, PM₁₀, NO₂, SO₂, CO, and O₃ were estimated by spatiotemporal kriging method. Exposure windows were divided into 5: preantral follicle period, antral follicle period, germinal period, embryonic period and early fetal period. Logistic generalized estimating equations were used to estimate the associations between air pollutants and overall or organ-system specific congenital anomalies. Negative control exposure method was used to detect and reduce bias of estimation.

RESULTS

We found increasing levels of PM_2.5 and PM₁₀ were associated with higher risk of overall congenital anomalies during early fetal period, equating gestation 10-12 weeks (OR: 1.05, 95% CI: 1.02-1.09, p = 0.013 for a 10 μg/m³ increase of PM_2.5; OR: 1.03, 95% CI: 1.01-1.06, p = 0.021 for a 10 μg/m³ increase of PM₁₀). Cleft lip and cleft palate were associated with PM₁₀ in germinal period and early fetal period. The CAs of eye, ear, face and neck were related to CO in preantral follicle stage. We did not find an association between chromosome abnormalities and air pollution exposure.

CONCLUSIONS

We concluded that ambient air pollution was a risk factor for congenital anomalies in the fetuses conceived through IVF, especially exposure in early fetal period.

Association between maternal exposure to PM10 and risk of anorectal atresia/stenosis in offspring: a population-based case-control study in Liaoning Province, China

The potential association between maternal exposure to PM₁₀ ranging from 3 months prior to conception to the end of the early trimester and the risk of anorectal atresia/stenosis in offspring has not been established. Thus, we determined the association between maternal exposure to PM₁₀ and risk of anorectal atresia/stenosis in offspring in this study. We recruited 713 patients including 480 male and 233 female with anorectal atresia/stenosis and 7950 randomly selected healthy offspring from the Maternal and Child Health Certificate Registry of Liaoning Province and delivered between 1 January 2010 and 31 December 2015. Monthly PM₁₀ concentrations were retrieved from the Environment Protection Bureau of each city in Liaoning Province. We established a multivariable logistic regression model to calculate the adjusted odds ratios (ORs) and 95% confidence intervals (CIs). Maternal exposure to PM₁₀ was associated with an increased risk for anorectal atresia/stenosis in offspring during the 3 months prior to conception (per 10 μg/m³ increment: OR = 1.15, 95% CI = 1.03-1.20; per SD [27 μg/m³] increment: OR = 1.33, 95% CI = 1.09-1.63) and the first trimester (per 10 μg/m³ increment: OR = 1.08, 95% CI = 1.00-1.17; per SD [28 μg/m³] increment: OR = 1.26, 95% CI = 1.01-1.57). Evaluation of the association with a shorter exposure window (1 month) revealed a positive association between anorectal atresia/stenosis and PM₁₀ from the 3rd month prior to pregnancy to each month of the 1st trimester. Maternal exposure to PM₁₀ 3 months prior to conception and during the 1st trimester was associated with an increased risk of anorectal atresia/stenosis in the offspring. Future perspective cohort studies are needed to confirm our findings.

Long-term trends in the incidence of congenital anomalies in Central China from 1997 to 2019

OBJECTIVE

The aim of the study was to investigate the incidence of, and trends in, congenital anomalies in Central China from 1997 to 2019.

STUDY DESIGN

This was a descriptive study.

METHODS

We collected data describing 4,134,098 births from 75 hospital monitoring sites in Henan Province, Central China, from 1997 to 2019. A joinpoint regression model was used to analyze the continuous changes.

RESULTS

There were 4,134,098 births recorded from 1997 to 2019, of which 50,646 noted the presence of congenital anomalies (incidence: 122.5 per 10,000). The incidence of congenital anomalies was found to have increased over time (P-trend <0.05). Congenital anomaly incidence in urban areas was higher than that in rural areas (155.3 per 10,000 vs 100.7 per 10,000; P < 0.001). Moreover, incidence was higher in males than in females (129.1 per 10,000 vs 112.9 per 10,000; P < 0.001). The incidence of neural tube defects significantly reduced from 1997 to 2019 (39.3 per 10,000 in 1997 vs 0.92 per 10,000 in 2019, P-trend <0.001), whereas the incidence of congenital heart disease (CHD) increased (5.56 per 10,000 in 2010 to 136.46 per 10,000 in 2019), which meant that CHD was the most common congenital anomaly post-2013.

CONCLUSION

In Henan province, the incidence of congenital anomalies increased by 115% from 1997 to 2019. Notably, the incidence of CHD is rising.

Human Serum Albumin Cys34 Adducts in Newborn Dried Blood Spots: Associations With Air Pollution Exposure During Pregnancy

Background: Increasing evidence suggests that exposure to air pollution during pregnancy is associated with adverse pregnancy outcomes. However, biomarkers associated with air pollution exposure are widely lacking and often transient. In addition, ascertaining biospecimens during pregnacy to assess the prenatal environment remains largely infeasible. Objectives: To address these challenges, we investigated relationships between air pollution exposure during pregnancy and human serum albumin Cys34 (HSA-Cys34) adducts in newborn dried blood spots (DBS) samples, which captures an integration of perinatal exposures to small reactive molecules in circulating blood. Methods: Newborn DBS were obtained from a state archive for a cohort of 120 children born at one Kaiser Permanente Southern California (KPSC) hospitals in 2007. These children were selected to maximize the range of residential air pollution exposure during the entire pregnancy to PM2.5, PM10, NO2, O3, based on monthly estimates interpolated from regulatory monitoring sites. HSA-Cys34 adducts were selected based on previously reported relationships with air pollution exposure and oxidative stress. Results: Six adducts measured in newborn DBS samples were associated with air pollution exposures during pregnancy; these included direct oxidation products, adducts formed with small thiol compounds, and adducts formed with reactive aldehydes. Two general trends were identified: Exposure to air pollution late in pregnancy (i.e., in the last 30 days) was associated with increased oxidative stress, and exposure to air pollution earlier in pregnancy (i.e., not in the last 30 days) was associated with decreased oxidative stress around the time of birth. Discussion: Air pollution exposure occurring during pregnancy can alter biology and leave measurable impacts on the developing infant captured in the newborn DBS adductome, which represents a promising tool for investigating adverse birth outcomes in population-based studies.

Association between preconceptional air pollution exposure and medical purposes for selective termination of pregnancy

BACKGROUND

Exposure to air pollutants is associated with adverse pregnancy outcomes. But evidence on the effects of preconceptional air pollution exposure on the risk of termination of pregnancy (TOP) caused by pregnancy losses and congenital malformations is lacking.

METHODS

The distributed lag nonlinear model (DLNM) was used to evaluate the impact of short-term air pollutants exposure on the risk of TOP. Stratified analyses by age (<35 years old, ≥ 35 years old) and season (warm season, cold season) were further conducted. Relative risk (RR) and 95 % confidential interval (95 % CI) were calculated for per interquartile range (IQR) increment in air pollutants during the study period.

RESULTS

PM_2.5, PM₁₀, and O₃ exposure were significantly associated with elevated risk of TOP. The risk of TOP was associated with PM_2.5 exposure from lag11 to lag15 in the single-pollutant model, and the strongest association was observed at lag13 (RR = 1.021, 95%CI:1.002-1.040). PM₁₀ exposure from lag10 to lag15 was associated with increased TOP risk, with the corresponding peak association being at lag13 (RR = 1.020, 95%CI: 1.004-1.037). For O₃, the single-day lag association appeared to be statistically significant from lag26 to lag27, with the highest RR of TOP cases being at lag27 (RR = 1.044, 95%CI: 1.005-1.084). Similar results were observed for pregnancy losses (PL). However, no significantly association between air pollution exposure and the risk of congenital malformations (CM) was found in this study. Stratified analyses showed that pregnant women with more advanced ages were more susceptible to PM_2.5, PM₁₀, and O₃ exposure. The effect of PM_2.5 exposure was statistically significant in cold season subgroups.

CONCLUSION

The findings suggest that exposure to PM_2.5, PM₁₀, and O₃ before pregnancy are associated with the risk of TOP in Lu'an, China, reflecting the significance of preconceptional environmental exposure in the development of adverse pregnancy outcomes.

Associations between air pollution exposure and birth defects: a time series analysis

Air pollution is a serious environmental problem in China. Birth defects are particularly vulnerable to outdoor air pollution. Our study was to evaluate the association between short-term exposure to air pollutants and the risk of birth defects. Daily data including the air pollutants, meteorological characteristics, and birth records were obtained in Hefei, China, during January 2013 to December 2016. The findings showed that PM_2.5, PM₁₀, SO₂, NO₂, and O₃ exposures were positively correlated with the risk of birth defects. Maternal exposure to PM_2.5 and SO₂ during the 4th to 13th gestational weeks was observed to have a significant association with the risk of birth defects, with the maximum effect in the 7th or 8th week for PM_2.5 and the maximum effect in the 7th week for SO₂. The positively significant exposure windows were the 4th to 14th weeks for PM₁₀, the 4th to 12th weeks for NO₂, and the 26th to 35th weeks for O₃, respectively. The strongest associations were observed in the 8th week for PM₁₀, the 7th week for NO₂, and in the 31st or 32nd week for O_3. The findings of this study demonstrate that air pollutants increase the risk of birth defects among women during pregnancy in Hefei, China, which provide evidence for improving the health of pregnant women and neonates in developing countries, and uncovered potential opportunities to reduce or prevent birth defects by proactive measures during pregnancy.

Correlation between Exposure to Fine Particulate Matter (PM2.5) during Pregnancy and Congenital Anomalies: Its Surgical Perspectives

BACKGROUND

Fine particulate matter (PM_2.5) can easily penetrate blood vessels and tissues through the human respiratory tract and cause various health problems. Some studies reported that particular matter (PM) exposure during pregnancy is associated with low birth weight or congenital cardiovascular anomalies. This study aimed to investigate the correlation between the degree of exposure to PM ≤ 2.5 μm (PM_2.5) during pregnancy and congenital anomalies relevant to the field of pediatric surgery.

METHODS

Mother-infant dyads with registered addresses in the Metropolitan City were selected during 3 years. The electronic medical records of mothers and neonates were retrospectively analyzed, with a focus on maternal age at delivery, date of delivery, gestation week, presence of diabetes mellitus (DM) or hypertension, parity, the residence of the mother and infant, infant sex, birth weight, Apgar score, and presence of congenital anomaly. The monthly PM_2.5 concentration from the first month of pregnancy to the delivery was computed based on the mothers' residences.

RESULTS

PM_2.5 exposure concentration in the second trimester was higher in the congenital anomaly group than in the non-congenital anomaly group (24.82 ± 4.78 µg/m³, P = 0.023). PM_2.5 exposure concentration did not affect the incidence of nervous, cardiovascular, and gastrointestinal anomalies. While statistically insignificant, the groups with nervous, cardiovascular, gastrointestinal, musculoskeletal, and other congenital anomalies were exposed to higher PM_2.5 concentrations in the first trimester compared with their respective counterparts. The effect of PM_2.5 concentration on the incidence of congenital anomalies was significant even after adjusting for the mother's age, presence of DM, hypertension, and parity. The incidence of congenital anomalies increased by 26.0% (95% confidence interval of 4.3% and 49.2%) per 7.23 µg/m³ elevation of PM_2.5 interquartile range in the second trimester.

CONCLUSIONS

The congenital anomaly group was exposed to a higher PM_2.5 concentration in the second trimester than the non-congenital anomaly group. The PM_2.5 exposure concentration level in the first trimester tended to be higher in groups with anomalies than those without anomalies. This suggests that continuous exposure to a high PM_2.5 concentration during pregnancy influences the incidence of neonatal anomalies in surgical respects.

Meta-analyses of maternal exposure to atmospheric particulate matter and risk of congenital anomalies in offspring

Congenital anomalies are the main causes of infant death and disability. Previous studies have suggested that maternal exposure to particulate matter is related to congenital malformation. However, the conclusions of this study remain controversial. Hence, meta-analyses were performed to assess the relationship between maternal exposure to particulate matter and the risk of congenital anomalies. The Medline, Embase, and Web of Science databases were systemically searched from inception until August 2020 to find articles related to birth defects and particulate matter. The pooled risk estimated for the combination of pollution outcomes was calculated for each study by performing fixed effects or random effects models. The existence of heterogeneity and publication bias in relevant studies was also examined. Thirty studies were included in the analysis. A statistically increased summary risk valuation was found. PM₁₀ exposure was associated with an increased risk of congenital heart disease, neural tube defects, and cleft lip with or without cleft palate (OR per 10 μg/m³ = 1.05, 95% CI, 1.03-1.07; OR per 10 μg/m³ = 1.04, 95% CI, 1.01-1.06; OR per 10 μg/m³ = 1.03, 95% CI, 1.01-1.06). Maternal exposure to particulate matter might be associated with an increased risk of congenital anomalies. Our results indicate the dangers of particulate matter exposure on fetal development and the importance of protection against exposure to such particles during pregnancy. The schematic representation of the association between maternal exposure to PM_2.5/PM₁₀ and congenital anomalies in offspring, and geographic distribution of the included reports in the meta-analyses.

Endocrine-Disrupting Chemicals and Disorders of Penile Development in Humans

This paper reviews the current knowledge on the environmental effects on penile development in humans. The specific focus is on endocrine-disrupting chemicals (EDCs), a heterogeneous group of natural or manmade substances that interfere with endocrine function, and whether they can induce hypospadias and micropenis in male neonates. Epidemiological data and animal observations first raised suspicions about environmental effects, leading to the testis dysgenesis syndrome (TDS) hypothesis. More recent research has provided stronger indications that TDS may indeed be the result of the direct or indirect effects of EDCs. Drawing on epidemiological and toxicological studies, we also report on the effects of maternal diet and substances like pesticides, phthalates, bisphenol A, and polychlorinated biphenyls. Proximity to contamination hazards and occupational exposure are also suspected to contribute to the occurrence of hypospadias and micropenis. Lastly, the cumulative effects of EDCs and the possibility of transgenerational effects, with the penile development of subsequent generations being affected, raise concerns for long-term public health.

Modification of the effects of nitrogen dioxide and sulfur dioxide on congenital limb defects by meteorological conditions

STUDY QUESTION

Can meteorological conditions modify the associations between NO2 and SO2 exposure and congenital limb defects (CLDs) during the first trimester of pregnancy?

SUMMARY ANSWER

Increases in NO2 and SO2 exposure were consistently associated with higher risks of CLDs during the first trimester of pregnancy; both low- and high-temperature exposure and high air humidity act synergistically with the two air pollutants on CLDs.

WHAT IS KNOWN ALREADY

Animal studies have indicated air pollutants are associated with CLDs, but corresponding epidemiological studies are limited with equivocal conclusions. Meteorological conditions are closely connected to the generation, diffusion, distribution and even chemical toxicity of air pollutants.

STUDY DESIGN, SIZE, DURATION

This case-control study included 972 cases of CLDs and 9720 controls in Changsha, China during 2015-2018.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Cases from the hospital based monitoring system for birth defects (including polydactyly, syndactyly, limb shortening, and clubfoot) and healthy controls from the electronic medical records system were studied. Complete data on daily average NO2 and SO2 concentrations and meteorological variables were obtained from local monitoring stations to estimate monthly individual exposures during the first trimester of pregnancy, using the nearest monitoring station approach for NO2 and SO2 concentrations, and the city-wide average approach for temperature and relative humidity, respectively. The 25th and 75th percentiles of daily mean temperature, as well as the 50th percentile of daily mean relative humidity during the study period were used to classify high- and low-temperature exposure, and high humidity exposure based on existing evidence and local climate characteristics. Multivariate logistic regression models were used to estimate the independent effects per 10 μg/m3 increase in NO2 and SO2 on CLDs, and the attribute proportions of interaction (API) were used to quantify the additive joint effects of air pollutants with meteorological conditions after including a cross product interaction term in the regression models.

MAIN RESULTS AND THE ROLE OF CHANCE

NO2 and SO2 exposures during the first trimester of pregnancy were consistently and positively associated with overall CLDs and subtypes, with adjusted odd ratios (aORs) ranging from 1.13 to 1.27 for NO2, and from 1.37 to 2.49 for SO2. The effect estimates were generally observed to be the strongest in the first month and then attenuated in the second and third months of pregnancy. Synergistic effects of both low and high temperature in combination with NO2 (with APIs ranging from 0.07 to 0.38) and SO2 (with APIs ranging from 0.18 to 0.51) appeared in the first trimester of pregnancy. Several significant modifying effects by high humidity were also observed, especially for SO2 (with APIs ranging from 0.13 to 0.38). Neither NO2 nor SO2 showed an interactive effect with season of conception.

LIMITATIONS, REASONS FOR CAUTION

The methods used to estimate individual exposure levels of air pollutants and meteorological factors may lead to the misclassification bias because of the lack of information on maternal activity patterns and residential mobility during pregnancy. Moreover, we were unable to consider several potentially confounding factors, including socioeconomic status, maternal nutrient levels, alcohol use and smoking during early pregnancy due to unavailable data, although previous studies have suggested limited change to the results after when including these factors in the analysis.

WIDER IMPLICATIONS OF THE FINDINGS

The findings are helpful for understanding the combined effects of air pollution and meteorological conditions on birth defects. Environmental policies and practices should be formulated and implemented to decrease air pollutant emissions and improve meteorological conditions to reduce their harmful effects on pregnancy. Additionally, pregnant women should be suggested to reduce outdoor time when the air quality is poor, especially when ambient temperature is higher or lower than what is comfortable, or when it is excessively humid.

STUDY FUNDING/COMPETING INTEREST(S)

The study is funded by Major Scientific and Technological Projects for Collaborative Prevention and Control of Birth Defects in Hunan Province (2019SK1012), Major Research and Development Projects in Hunan Province (2018SK2060) and Scientific and Technological Department Projects in Hunan Province (2017SK50802). There are no competing interests.

TRIAL REGISTRATION NUMBER

N/A.

Maternal exposure to sulfur dioxide before and after conception and the risk of hypospadias in offspring

As far as we know, there have been no studies exploring the association between maternal sulfur dioxide (SO₂ ) exposure and the risk of hypospadias in offspring. We aimed to evaluate this association during the 3 months before conception and the first trimester. A population-based case-control study was conducted in male infants, consisting of 348 cases of hypospadias and 4023 controls. Maternal exposure to SO₂ , particulate matter with aerodynamic diameters ≤10 μm (PM₁₀ ), and nitrogen dioxide (NO₂ ) was assessed by averaging the concentrations recorded at all stations in the mother's city of residence. Air pollutants were tested for multicollinearity using variance inflation factor analysis. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated by multivariable logistic regression models. SO₂ exposure during the 3 months before conception was significantly associated with the risk of hypospadias (highest tertile: OR = 7.40, 95% CI: 3.54-15.62). When focusing on shorter exposure windows, similar associations were observed for SO₂ exposure in the first and second month before and the first month after conception. In conclusion, maternal exposure to SO₂ during the 3 months before and the first and second months after conception may increase the risk of hypospadias in offspring.

Acute effects of short-term exposure to ambient air pollution on reproductive hormones in young males of the MARHCS study in China

Air pollution, which is associated with male reproductive health. However, it is unknown the acute effects of ambient air pollutants exposure on male reproductive hormones. The current study, we measured serum levels of reproductive hormone in 2030 blood samples gathered from The Male Reproductive Health in Chongqing College Students (MARHCS) cohort study. We derived a full coverage of ambient air pollutant (PM₁₀, PM_2.5, SO₂, NO₂, CO and O₃) concentrations by employing machine learning algorithms, and used a mixed-effect model to estimate single-day and cumulative effects of air pollutants exposure on serum reproductive hormones. Our results showed that (1) PM₁₀ and PM_2.5 concentrations were positively associated with estradiol (E₂) in both single and cumulative lag days, but were negatively associated with the ratio of Testosterone/E₂ (the T/E₂ ratio). NO₂ was positively associated with estradiol at lag day 2 (95% CI: 0.290, 0.881; corrected P = 0.048) and lag 0-2 days (95% CI: 0.523, 1.337; corrected P = 0.003), with progesterone (P) at lag day 2 and lag day 3 (corrected P < 0.05). There was also a positive association between CO exposure and progesterone at lag day 2. (2) SO₂ was inversely associated with E₂ at lag day 3, 4 and lag 0-4 days, and progesterone at lag day 0, 1, 2 and lag 0-1, 0-2, 0-4 days, but positively associated with the T/E₂ ratio at lag day 3, 4 and lag 0-4 days (corrected P < 0.05). O₃ exposure was negatively associated with E₂ at lag day 3 (95% CI: -0.216, -0.074, corrected P = 0.03). (3) No significant associations were found between the cumulative daily average air pollutant exposure of CO, O₃ and hormone outcomes. This study suggests that short-term exposure to air pollutants may thus alter reproductive hormone levels, especially on serum estradiol, progesterone levels and the T/E₂ ratio.

Association between prenatal air pollution exposure and risk of hypospadias in offspring: a systematic review and meta-analysis of observational studies

Background: The findings of associations between prenatal air pollution exposure and hypospadias risk in offspring are inconsistent. No systematic review or meta-analysis has yet summarized the present knowledge on the aforementioned topic.

Methods: Relevant manuscripts were identified by searching PubMed and Web of Science databases through January 31, 2020. Summary odds ratios (ORs) with 95% confidence intervals (CIs) in meta-analyses were estimated based on a random effects model. Publication bias was evaluated by funnel plots, Begg’s test, and Egger’s test.

Results: The search identified 3,032 relevant studies. Sixteen studies cumulatively involving 21,701 hypospadias cases and 1,465,364 participants were included. All of these studies were classified as having a low risk of bias. We classified pollutants as nitrogen oxides, particulate matter (PM), ozone, and other exposures. The exposure window to pollutants varied from three months before conception to seven days after delivery. In the meta-analyses, only PM_2.5 exposure in the first trimester was related to increased risk of hypospadias (per 10 μg/m³ OR = 1.34; 95% CI: 1.06–1.68).

Conclusion: We found evidence for an effect of PM_2.5 exposure on hypospadias risk. Improvements in the areas of study design, exposure assessment, and specific exposure window are needed to advance this field.

Associations between weekly air pollution exposure and congenital heart disease

BACKGROUND

The topic of congenital heart diseases (CHDs) has attracted more and more attentions. Accumulating evidence suggests that exposure to air pollutants during pregnancy is associated with CHDs, yet the results are inconsistent and study about weekly exposure is few. Our study evaluated the association between weekly air pollution and CHDs in Hefei, China.

MATERIALS AND METHODS

Daily CHDs admission data were obtained from eight hospitals in Hefei from October 2015 to September 2017. Meteorological data and air quality were collected from China Meteorological Data Network. Distributed lag nonlinear model (DLNM) considering both the lag effect of exposure factors and the nonlinear relationship of exposure-reaction was used to assess the effect of weekly air pollutants exposure on CHDs admission.

RESULTS

During the study period, totally 47,046 cases of perinatal infants were recruited, and the incidence of CHDs was 9.71 per thousand. The findings showed PM_2.5, PM₁₀, SO₂ and NO₂ significantly increased the risk of CHDs. Each 10 μg/m³ increase in PM_2.5 during gestational weeks 20-26 increased the risk of CHDs. The susceptibility windows of PM₁₀ (weeks 0-2 and weeks 25-29 of pregnancy), SO₂ (weeks 8-16 and weeks 29-38) and NO₂ (week 40), while the strongest effects of these 4 pollutants on CHDs were observed in week 22 (RR = 1.034, 95% CI: 1.007-1.062), week 0 (RR = 1.081, 95% CI: 1.02-1.146), week 37 (RR = 1.528, 95% CI: 1.085-2.153) and week 40 (RR = 1.171, 95% CI: 1.006-1.364), respectively.

CONCLUSIONS

Air pollutants (SO₂, NO₂, PM₁₀, and PM_2.5) exposure could increase the risk of CHDs, while the most crucial susceptibility windows for the exposure were mainly in the second and third trimesters. Boys seemed to be more sensitive to air pollution. Our study contributes to the knowledge of the association between maternal exposure to air pollution and CHDs, but the associations need to be verified by further studies.

Association between prenatal exposure to ambient particulate matter and risk of hypospadias in offspring: A systematic review and meta-analysis

BACKGROUND

Epidemiological studies on whether prenatal exposure to PM_2.5, PM_2.5-10, and PM₁₀ increases the risk of hypospadias are limited and the results are inconsistent.

OBJECTIVES

We conducted this systematic review and meta-analysis to evaluate these associations.

METHODS

Relevant studies were identified by searching the PubMed and Embase databases up to the end of February 2020. Observational studies that investigated the relationships between prenatal exposure to PM₁₀, PM_2.5, and PM_2.5-10 and the risk of hypospadias in offspring were eligible for the review. The risk of bias was evaluated using the Newcastle-Ottawa scale. Random-effects models were used to estimate pooled relative risks (RRs) and 95% confidence intervals (CIs) for the associations.

RESULTS

Nine studies (two cohort and seven case-control studies) with a total of 2806 hypospadias cases were included. Eight studies were at low risk of bias and only one study was at high risk of bias. Five studies reported the association between per interquartile range increase in PM_2.5 exposure within the first trimester and the risk of hypospadias. The pooled RR was 1.17 (95% CI: 1.00, 1.36). Two studies reported the per interquartile range increase in PM_2.5 exposure during 1 month before pregnancy associated with the risk of hypospadias, with a pooled RR of 1.25 (95% CI: 1.03, 1.51). No association was observed between PM_2.5-10 and PM₁₀ exposure during pregnancy and the risk of hypospadias in offspring.

CONCLUSION

This study suggested a modest association between prenatal PM_2.5 exposure during 1 month before pregnancy or within the first trimester and the risk of hypospadias in offspring. Further large-scale cohort studies are required to verify this association.

Prenatal exposure to traffic-related air pollution and risk of congenital diseases in South Korea

BACKGROUND

Previous studies have suggested links between exposure to ambient air pollutants and increased risk of congenital heart defects. However, few studies have investigated the association between other congenital diseases and traffic-related air pollution. In this study, we assessed the relationship between prenatal exposure to fine particulate matter (PM_2.5) and nitrogen dioxide (NO₂) with congenital diseases in South Korea.

METHODS

Patients with one or more congenital diseases and a control group of patients with non-infective gastroenteritis and colitis with a case:control ratio of 1:3 were obtained from the National Health Insurance Service data for 2008-2013 in South Korea. We estimated the associations of PM_2.5 and NO₂ exposures with congenital diseases using generalized estimation equations after controlling for covariates.

RESULTS

Maternal PM_2.5 exposure during the first and second trimester showed positive associations with overall congenital diseases, with changes of 14.7% (95% confidence intervals (CI), 9.3%, 20.3%) and 16.2% (95% CI, 11.0%, 21.7%), respectively, per 11.1 μg/m³ and 10.2 μg/m³ increase of PM_2.5 interquartile range (IQR). Similarly, NO₂ exposure during the first and second trimester was associated with increased numbers of overall congenital anomalies, with 8.2% (95% CI, 4.2%, 12.3%) and 15.6% (95% CI, 9.3%, 22.2%) more cases, respectively, per 10.6 ppb increase of NO₂. We found that maternal PM_2.5 exposure during the first and second trimesters of pregnancy was significantly associated with increased risk of specific congenital diseases, including subtypes affecting the circulatory, genitourinary, and musculoskeletal system. However, no significant associations were observed during the third trimester. Maternal NO₂ exposure across the entire pregnancy was associated with malformations of the musculoskeletal system.

CONCLUSIONS

Our study identified significant links between in utero exposure to PM_2.5 and NO₂ and certain congenital diseases, and suggests that stricter controls on PM_2.5 and NO₂ concentrations are required.

Explore spatio-temporal PM2.5 features in northern Taiwan using machine learning techniques

The complex mixtures of local emission sources and regional transportations of air pollutants make accurate PM2.5 prediction a very challenging yet crucial task, especially under high pollution conditions. A symbolic representation of spatio-temporal PM2.5 features is the key to effective air pollution regulatory plans that notify the public to take necessary precautions against air pollution. The self-organizing map (SOM) can cluster high-dimensional datasets to form a meaningful topological map. This study implements the SOM to effectively extract and clearly distinguish the spatio-temporal features of long-term regional PM2.5 concentrations in a visible two-dimensional topological map. The spatial distribution of the configured topological map spans the long-term datasets of 25 monitoring stations in northern Taiwan using the Kriging method, and the temporal behavior of PM2.5 concentrations at various time scales (i.e., yearly, seasonal, and hourly) are explored in detail. Finally, we establish a machine learning model to predict PM2.5 concentrations for high pollution events. The analytical results indicate that: (1) high population density and heavy traffic load correspond to high PM2.5 concentrations; (2) the change of seasons brings obvious effects on PM2.5 concentration variation; and (3) the key input variables of the prediction model identified by the Gamma Test can improve model's reliability and accuracy for multi-step-ahead PM2.5 prediction. The results demonstrated that machine learning techniques can skillfully summarize and visibly present the clusted spatio-temporal PM2.5 features as well as improve air quality prediction accuracy.

Dynamic linkages among economic development, environmental pollution and human health in Chinese

Background

Research on the relationships between economic development, energy consumption, environmental pollution, and human health has tended to focus on the relationships between economic growth and air pollution, energy and air pollution, or the impact of air pollution on human health. However, there has been little past research focused on all the above associations.

Methods

The few studies that have examined the interconnections between the economy, energy consumption, environmental pollution and health have tended to employ regression analyses, DEA (Data Envelopment Analysis), or DEA efficiency analyses; however, as these are static analysis tools, the analyses did not fully reveal the sustainable economic, energy, environmental or health developments over time, did not consider the regional differences, and most often ignored community health factors. To go some way to filling this gap, this paper developed a modified two stage Undesirable Meta Dynamic Network model to jointly analyze energy consumption, economic growth, air pollution and health treatment data in 31 Chinese high-income and upper-middle income cities from 2013-2016, for which the overall efficiency, production efficiency, healthcare resource utilization efficiency and technology gap ratio (TGR) for all input and output variables were calculated.

Results

It was found that: (1) the annual average overall efficiency in China's eastern region was the highest; (2) the production stage efficiencies were higher than the healthcare resource utilization stage efficiencies in most cities; (3) the high-income cities had lower TGRs than the upper-middle income cities; (4) the high-income cities had higher average energy consumption efficiencies than the upper-middle income cities; (5) the health expenditure efficiencies were the lowest of all inputs; (6) the high-income cities' respiratory disease and mortality rate efficiencies were higher than in the upper-middle income cities, which had improving mortality rate efficiencies; and (7) there were significant regional differences in the annual average input and output indicator efficiencies.

Conclusions

First, the high-income cities had higher average efficiencies than the upper-middle income cities. Of the ten eastern region high-income cities, Guangzhou and Shanghai had average efficiencies of 1, with the least efficient being Shijiazhuang. In the other regions, the upper-middle income cities required greater technology and health treatment investments. Second, Guangzhou, Lhasa, Nanning, and Shanghai had production efficiencies of 1, and Guangzhou, Lhasa, Nanning, Shanghai and Fuzhou had healthcare resource utilization efficiencies of 1. As the average production stage efficiencies in most cities were higher than the healthcare resource utilization stage efficiencies, greater efforts are needed to improve the healthcare resource utilization. Third, the technology gap ratios (TGRs) in the high-income cities were slightly higher than in the upper-middle income cities. Therefore, the upper-middle income cities need to learn from the high-income cities to improve their general health treatment TGRs. Fourth, while the high-income cities had higher energy consumption efficiencies than the upper-middle income cities, these were decreasing in most cities. There were few respiratory disease efficiency differences between the high-income and upper-middle income cities, the high-income cities had falling mortality rate efficiencies, and the upper-middle income cities had increasing mortality rate efficiencies. Overall, therefore, most cities needed to strengthen their health governance to balance economic growth and urban expansion. Fifth, the average AQI efficiencies in both the high-income and upper-middle income cities were higher than the average CO₂ efficiencies. However, the high-income cities had lower average CO₂ emissions and AQI efficiencies than the upper-middle income cities, with the AQI efficiency differences between the two city groups expanding. As most cities were focusing more on air pollution controls than carbon dioxide emissions, greater efforts were needed in coordinating the air pollution and carbon dioxide emissions treatments. Therefore, the following suggestions are given. (1) The government should reform the hospital and medical systems. (2) Local governments need to strengthen their air pollution and disease education. (3) High-income cities need to improve their healthcare governance to reduce the incidence of respiratory diseases and the associated mortality. (4) Healthcare governance efficiency needs to be prioritized in 17 upper-middle income cities, such as Hangzhou, Changchun, Harbin, Chengdu, Guiyang, Kunming and Xi'an, by establishing sound medical management systems and emergency environmental pollution treatments, and by increasing capital asset medical investments. (5) Upper-middle income cities need to adapt their treatment controls to local conditions and design medium to long-term development strategies. (6) Upper-middle income cities need to actively learn from the technological and governance experiences in the more efficient higher-income cities.

Maternal exposure to ambient particulate matter 10 μm or less in diameter before and after pregnancy, and anencephaly risk: A population-based case-control study in China

BACKGROUND

There is no epidemiological evidence on the effects of maternal exposure to ambient particulate matter 10 μm or less in diameter (PM₁₀) and anencephaly risk in offspring.

METHODS

We conducted a population-based case-control study in Liaoning Province, China. The case group consisted of 663 cases with anencephaly and the control group consisted of 7950 healthy infants from the Maternal and Child Health Certificate Registry of Liaoning Province that were born between 2010 and 2015. Daily PM₁₀ concentrations were obtained from 77 monitoring stations located within the study area. A multivariable logistic regression model was established to calculate the adjusted odds ratios (ORs) and 95% confidence intervals (CIs).

RESULTS

Maternal PM₁₀ exposure was significantly associated with an increased risk of anencephaly at three months before conception (highest versus lowest tertile: OR = 1.74, 95% CI: 1.29-2.34; per 10 μg/m³ increment: OR = 1.13, 95% CI: 1.06-1.20) and three months after conception (highest versus lowest tertile: OR = 1.93, 95% CI: 1.44-2.60; per 10 μg/m³ increment: OR = 1.01, 95% CI: 0.95-1.08). The evaluation of shorter exposure windows revealed similar associations for PM₁₀ exposure from the third month before pregnancy to the third month after pregnancy.

CONCLUSIONS

Maternal PM₁₀ exposure is positively associated with anencephaly risk during the critical period of neural system development.

Prenatal Fine Particulate Matter (PM2.5) Exposure and Pregnancy Outcomes-Analysis of Term Pregnancies in Poland

Air pollution is currently one of the greatest threats to global health. Polish cities are among the most heavily polluted in Europe. Due to air pollution 43,100 people die prematurely in Poland every year. However, these data do not take into account the health consequences of air pollution for unborn children. Thus, the aim of this study was to evaluate the effects of the fine particulate matter air pollution (less than 2.5 μm in diameter) on pregnancy outcomes. An analysis of pregnant women and their children was made using a questionnaire survey from a nationwide study conducted in 2017. Questionnaires from 1095 pregnant women and data from their medical records were collected. An analysis of air pollution in Poland was conducted using the air quality database maintained by the Chief Inspectorate for Environmental Protection in Poland. A higher concentration of PM_2.5 was associated with a decrease in birth weight and a higher risk of low birthweight (i.e., <2500 g). We also observed lower APGAR scores. Thus, all possible efforts to reduce air pollution are critically needed.

Maternal air pollution exposure and congenital heart defects in offspring: A systematic review and meta-analysis

BACKGROUND

Congenital heart defects (CHDs) has a multifactorial causation with a strong genetic component and many environmental triggers. Emerging body of empirical studies suggest that air pollution is an important contributor to the development of CHDs, however, there still remains some controversy over the current evidence, and to the authors' knowledge, no studies have reviewed the most recent evidence.

OBJECTIVES

We performed a systematic review and meta-analysis of epidemiological literature to investigate the relationship between maternal air pollution exposure and CHDs risk in offspring. The presence of heterogeneity and publication bias across available studies were also examined.

METHODS

An extensive literature search of epidemiological studies pertaining to air pollution and CHDs, published in English language, until August 1, 2019 was conducted. Summary risk estimates of pollution-outcome combinations were calculated for i) risk per specific increment of concentration and ii) risk at high versus low exposure level in each study using fixed-effect model or random-effects model.

RESULTS

A total of 26 studies were finally included. In the meta-analyses, high versus low carbon monoxide (CO) exposure was associated with an increased risk of tetralogy of Fallot [odds ratio (OR) = 1.21, 95% confidence interval (CI): 1.04-1.41], yet particulate matter ≤ 5 μm (PM_2.5) exposure was marginally associated with it. Increased risk of atrial septal defects (ASDs) was found for each 10 μg/m³ and 10 ppb increment in particulate matter ≤ 10 μm (PM₁₀) and ozone (O₃) exposure, respectively (OR = 1.04, 95% CI: 1.00-1.09; OR = 1.09, 95% CI: 1.02-1.17). Categorical nitrogen dioxide (NO₂) exposure was associated with an increased risk of coarctation of the aorta (OR for high versus low = 1.14, 95% CI: 1.02-1.26). Analyses for other combinations yielded none statistically significant associations. Sensitive analyses showed similar findings.

CONCLUSIONS

The summary effect estimates from this study suggest statistically significant associations between increased risk of specific CHDs subtypes and PM_2.5, PM₁₀, NO₂, CO, and O₃ exposures. Further studies, especially conducted in developing countries, with improvements in exposure assessing, outcome harmonizing, and mechanistic understanding are needed to elaborate the suggestive associations.

Maternal preconception and first trimester exposure to PM10 and the risk of oral clefts in offspring: a population-based, case-control study

BACKGROUND

Current literature describes limited and controversial evidence on the associations between maternal preconception and first trimester exposure to particulate matter with a diameter ≤10 µm (PM₁₀) and the risk of oral cleft (OC).

METHODS

We conducted a case-control study involving 3086 OC cases and 7950 controls, registered in the Maternal and Child Health Certificate Registry in Liaoning Province between 2010 and 2015. PM₁₀ concentrations were obtained from the Environment Protection Bureau. The exposure windows included the 3 months before pregnancy, the first trimester and the individual months. Unconditional logistic regression model was performed to estimate the OR and 95% CI for the association between PM₁₀ exposure and the risk of OC, cleft lip only (CLO), cleft palate only (CPO), and cleft lip and palate (CLP).

RESULTS

Maternal PM₁₀ exposure was positively associated with an increased risk for OC during the 3 months preconception (per 10 µg/m³ increment: OR=1.04, 95% CI 1.01 to 1.07; highest vs lowest quartile: OR=1.23, 95% CI 1.04 to 1.45) and the first trimester (per 10 µg/m³ increment: OR=1.05, 95% CI 1.02 to 1.08; highest vs lowest quartile: OR=1.37, 95% CI 1.15 to 1.64). Analyses based on individual months presented similar positive associations, particularly in the second month of pregnancy (OR=1.77, 95% CI 1.51 to 2.09) for highest versus lowest quartile. In the subtype analysis, stronger associations were observed for CLO, whereas there was negligible evidence for CPO and CLP. Sensitivity analyses using propensity score matching generated similar findings.

CONCLUSIONS

Our study provides evidence that PM₁₀ exposure during the 3 months preconception and the first trimester increases the risk of OC.

Periconceptional exposure to air pollution and congenital hypospadias among full-term infants

BACKGROUND

Evidence regarding whether prenatal exposure to air pollution increases the risk of hypospadias remains limited. The aim of the study is to evaluate the association between exposure to ambient air pollution during early pregnancy and the incidence of hypospadias.

METHODS

We conducted a 1:10 case-control study using the Taiwanese Birth Registry database. Male full-term infants reported to have hypospadias were defined as cases, and controls were randomly selected from male full-term infants without any congenital anomaly. The monthly average of ambient air pollutants, including PM₁₀, PM_2.5, PM_2.5-10, NO₂, NOx, O₃, and O₃ 8-h maximum, from 3 months before conception to 6 months post conception was retrieved from air quality monitoring stations and interpolated to the level of township using the kriging method. Multivariable logistic regression models were utilized to evaluate the associations.

RESULTS

A total of 200 hypospadias cases, with 2000 healthy controls sampled, were reported during 2007-2014. The results revealed that PM_2.5 exposure during the first 3 months after conception (odds ratio [OR] = 1.29, 95% confidence interval [CI]: 1.01-1.65, per interquartile range [IQR] = 15.6 μg/m³) and O₃ exposure during the first month after conception (OR = 1.40, 95% CI: 1.08-1.82, per IQR = 8.0 ppb) were associated with a higher incidence of hypospadias.

CONCLUSIONS

The results of the study suggest that early gestational exposure to ambient air pollution increases the risk of hypospadias among full-term infants.