Time-varying cycle average and daily variation in ambient air pollution and fecundability

Maternal Exposure to Surface Ozone and Reduced Fecundity in China: Evidence from a Nationwide Survey

The influence of ground-level O3, which possesses a higher oxidative concentration than other ambient pollutants, on reproductive health has received relatively limited scrutiny. In this study, we collected information on reproductive history, sociodemographic profiles, lifestyle, and residential details of 10,153 couples at risk of pregnancy. Each participant's 1-year, 3-year, and 5-year average O3 exposure levels were estimated using a previously developed randomized trees model. We used discrete-time Cox proportional hazards models to estimate the fecundability odds ratio (FOR) for each 10 μg/m3 change in the O3, adjusting for a set of demographics, lifestyle, and environmental covariables. We observed that a 10 μg/m3 increase in the annual average level of exposure to O3 was associated with a 16% reduction in fecundity (FOR: 0.84; 95% CI: 0.82-0.85). We also observed a 40% increase in the odds of infertility (OR: 1.40; 95% CI: 1.34-1.46) for each 10 μg/m3 rise in the annual mean of O3 exposure. After adjustment for fine particulate matter, the strong association between O3 exposure of fecundity to O3 persisted. Given the increasing epidemic of infertility, we strongly advocate for heightened consideration of O3's impact on reproductive health, as it may partially counterbalance the health benefits gained from improved PM2.5 levels in a middle-income setting.

Association of ambient ozone with time to pregnancy and the modifying effect of ambient temperature: a population-based cohort study

Research on the impact of ozone (O3) on fecundability has been inconclusive, lacking evidence examining the lagged pattern of ozone exposure and temperature modification. Current studies have predominantly been conducted in North America and Europe, leaving a gap in research from the Asian population. This population-based prospective cohort study involved 594,110 couples in Yunnan Province, China, enrolled in the National Free Preconception Health Examination Project. We calculated time-varying cycle-specific O3 concentration across 1-12 menstrual cycles before conception, according to each female's menstrual cycle length and residential addresses. Time to pregnancy was used as an outcome indicator. A discrete-time Cox regression model integrated with a distributed lag model (DLM) was employed for analysis. We observed that O3 exposure was negatively associated with fecundability, with the effect diminishing over time relative to conception. The first menstrual cycle before conception appeared most sensitive to O3 exposure, showing a 6.2 % decrease (HR: 0.938; 95 % CI: 0.936 to 0.941) in fecundability per one IQR increase of O3. Combined exposure to O3 and ambient temperature may exert a synergistic effect. The modifying effect of temperature was most pronounced in the first cycle before conception, with HRs of 0.891 (95 % CI: 0.886 to 0.895), 0.859 (95 % CI: 0.853 to 0.865), and 0.833 (95 % CI: 0.826 to 0.840) under low-, median-, and high-temperature conditions, respectively. Targeted policy interventions are needed to mitigate the dual impact of air pollution and rising temperatures.

Residential Exposure to PM2.5 Constituents and Fecundability in a Danish Preconception Cohort

BACKGROUND

Epidemiologic studies have demonstrated that ambient concentrations of particulate matter < 2.5 μm (PM2.5) are associated with reduced fecundability, the per cycle probability of conception. The specific constituents driving this association are unknown.

OBJECTIVES

We examined the association between ambient concentrations of PM2.5 constituents and fecundability in a Danish preconception cohort study.

METHODS

During 2007-2018, we enrolled female pregnancy planners in an Internet-based preconception cohort study. We included the 5905 participants who had been trying to conceive for < 3 cycles at study enrollment. Participants completed a baseline questionnaire and follow-up questionnaires every 8 weeks to update pregnancy status. We geocoded time-varying residential addresses to estimate ambient concentrations of total PM2.5 and the following PM2.5 constituents: elemental carbon (EC), primary organic aerosol (POA), secondary organic aerosols (SOA), sulfate (SO4 2-), ammonium (NH4 +), nitrate (NO3 -), and sea salt. We averaged concentrations of each pollutant across each menstrual cycle at risk. We fit proportional probabilities regression models to estimate fecundability ratios (FR) and 95% confidence intervals (CI), adjusting for potential confounders and co-pollutants.

RESULTS

Total PM2.5 concentrations were associated with reduced fecundability (the FR for an IQR increase, corresponding to 3.2 μg/m3, was 0.93 [95% CI 0.87, 0.99]). The association was strongest for POA: the FR for an IQR increase, corresponding to 1.3 μg/m3, was 0.92 (95% CI 0.84, 1.01). The corresponding FRs for the remaining PM2.5 constituents were 0.96 (95% CI 0.87, 1.05) for EC (IQR = 0.5 μg/m3), 0.98 (95% CI 0.91, 1.06) for SOA (IQR = 0.5), 0.97 (95% CI 0.92, 1.02) for SO2 4- (IQR = 0.4), 0.95 (95% CI 0.91, 1.01) for NH4 + (IQR = 0.5), 0.97 (95% CI 0.93, 1.01) for NO3 - (IQR = 1.0), and 1.00 (95% CI 0.95, 1.06) for sea salt (IQR = 0.4).

CONCLUSIONS

In this Danish preconception cohort study, PM2.5 constituents derived from biomass and transportation-related combustion may drive the association between PM2.5 concentrations and fecundability.

Long term exposure to road traffic noise and air pollution and risk of infertility in men and women: nationwide Danish cohort study

OBJECTIVE

To investigate associations between long term residential exposure to road traffic noise and particulate matter with a diameter <2.5 µm (PM2.5) and infertility in men and women.

DESIGN

Nationwide prospective cohort study.

SETTING

Denmark.

PARTICIPANTS

526 056 men and 377 850 women aged 30-45 years, with fewer than two children, cohabiting or married, and residing in Denmark between 2000 and 2017.

MAIN OUTCOME MEASURE

Incident infertility in men and women during follow-up in the Danish National Patient Register.

RESULTS

Infertility was diagnosed in 16 172 men and 22 672 women during a mean follow-up of 4.3 years and 4.2 years, respectively. Mean exposure to PM2.5 over five years was strongly associated with risk of infertility in men, with hazard ratios of 1.24 (95% confidence interval 1.18 to 1.30) among men aged 30-36.9 years and 1.24 (1.15 to 1.33) among men aged 37-45 years for each interquartile (2.9 µg/m3) higher PM2.5 after adjustment for sociodemographic variables and road traffic noise. PM2.5 was not associated with infertility in women. Road traffic noise (Lden, most exposed facade of residence) was associated with a higher risk of infertility among women aged 35-45 years, with a hazard ratio of 1.14 (1.10 to 1.18) for each interquartile (10.2 dB) higher five year mean exposure. Noise was not associated with infertility among younger women (30-34.9 years). In men, road traffic noise was associated with higher risk of infertility in the 37-45 age group (1.06, 1.02 to 1.11), but not among those aged 30-36.9 years (0.93, 0.91 to 0.96).

CONCLUSIONS

PM2.5 was associated with a higher risk of an infertility diagnosis in men, whereas road traffic noise was associated with a higher risk of an infertility diagnosis in women older than 35 years, and potentially in men older than 37 years. If these results are confirmed in future studies, higher fertility could be added to the list of health benefits from regulating noise and air pollution.

Estimation of couple fecundity in the general population and the association with monthly time-varying ambient particulate matter exposure in low- and middle-income countries: A population-based multi-center epidemiological study

BACKGROUND

Declining total fertility rates have been observed in low- and middle-income countries (LMICs). However, it remains unclear if this trend is related to a reduction in fecundity of general population. Research evidence on contributing factors to fecundity reduction is also limited. We aimed to first estimate couple fecundity in LMICs and then investigate its association with ambient particulate matter (PM) exposure.

METHODS

Using the information from Demographic and Health Surveys between 2003 and 2019, we estimated median time to pregnancy (TTP) and infertility prevalence across 30 LMICs, by employing a current duration approach. Individual PM (PM1, PM2.5, and PM10) exposure during the period of 'at risk' of pregnancy was assessed by months. An accelerated failure model was used to elucidate the association between monthly time-varying PM exposure and TTP. Subsequently, we estimated the prolonged TTP attributable to PM exposures above the World Health Organization (WHO)'s recommended air quality level in 2021.

RESULTS

Within the study regions, median TTP ranged from 6.90 (95 % CI 6.02-7.87) months in Latin America & Caribbean to 10.29 (95 % CI 9.28-11.36) months in East Asia & Pacific, with corresponding infertility prevalence varying from 33 % (95 % CI 29 %-36 %) to 44 % (95 % CI 41 %-48 %). Our estimations indicated that TTP was 1.08 (95 % CI: 0.99-1.18), 1.12 (95 % CI 1.06-1.19), and 1.05 (95 % CI 1.03-1.07) times longer for every 10 μg/m3 increment in PM1, PM2.5, and PM10, respectively. The prolonged TTP attributable to PM exposures surpassing the WHO guideline ranged from 0.11 to 2.81 months across the studied regions.

DISCUSSION

Ambient particulate matter is identified as a potential contributing factor to impaired fecundity in general population of LMICs. The findings underscore the importance of coordinated efforts to control ambient air pollution to mitigate the risk of fecundity reduction among the general population.

Reduced human fecundity attributable to ambient fine particles in low- and middle-income countries

BACKGROUND

Exposure to ambient fine particulate matter (PM2.5) has been associated with reduced human fecundity. However, the attributable burden has not been estimated for low- and middle-income countries (LMICs), where the exposure-response function between PM2.5 and the infertility rate has been insufficiently studied.

OBJECTIVE

This study examined the associations between long-term exposure to PM2.5 and human fecundity indicators, namely the expected time to pregnancy (TTP) and 12-month infertility rate (IR), and then estimated PM2.5-attributable burden of infertility in LMICs.

METHODS

We analyzed 164,593 eligible women from 100 Demographic and Health Surveys conducted in 49 LMICs between 1999 and 2021. We assessed PM2.5 exposures during the 12 months before a pregnancy attempt using the global satellite-derived PM2.5 estimates produced by Atmospheric Composition Analysis Group (ACAG). First, we created a series of pseudo-populations with balanced covariates, given different levels of PM2.5 exposure, using a matching approach based on the generalized propensity score. For each pseudo-population, we used 2-stage generalized Gamma models to derive TTP or IR from the probability distribution of the questionnaire-based duration time for the pregnancy attempt before the interview. Second, we used spline regressions to generate nonlinear PM2.5 exposure-response functions for each of the two fecundity indicators. Finally, we applied the exposure-response functions to estimate number of infertile couples attributable to PM2.5 exposure in 118 LMICs.

RESULTS

Based on the Gamma models, each 10 µg/m3 increment in PM2.5 exposure was associated with a TTP increase by 1.7 % (95 % confidence interval [CI]: -2.3 %-6.0 %) and an IR increase by 2.3 % (95 %CI: 0.6 %-3.9 %). The nonlinear exposure-response function suggested a robust effect of an increased IR for high-concentration PM2.5 exposure (>75 µg/m3). Based on the PM2.5-IR function, across the 118 LMICs, the number of infertile couples attributable to PM2.5 exposure exceeding 35 µg/m3 (the first-stage interim target recommended by the World Health Organization global air quality guidelines) was 0.66 million (95 %CI: 0.061-1.43), accounting for 2.25 % (95 %CI: 0.20 %-4.84 %) of all couples affected by infertility. Among the 0.66 million, 66.5 % were within the top 10 % high-exposure infertile couples, mainly from South Asia, East Asia, and West Africa.

CONCLUSION

PM2.5 contributes significantly to human infertility in places with high levels of air pollution. PM2.5-pollution control is imperative to protect human fecundity in LMICs.

Association between fine particulate matter and fecundability in Henan, China: A prospective cohort study

OBJECTIVE

To investigate the relationship between ambient fine particulate matter (PM2.5) exposure and fecundability.

METHODS

This study included 751,270 female residents from Henan Province who participated in the National Free Pre-conception Check-up Projects during 2015-2017. Ambient cycle-specific PM2.5 exposure was assessed at the county level for each participant using satellite-based PM2.5 concentration data at 1-km resolution. Cox proportional hazards models with time-varying exposure were used to estimate the association between fecundability and PM2.5 exposure, adjusted for potential individual risk factors.

RESULTS

During the study period, 568,713 participants were pregnant, monthly mean PM2.5 concentrations varied from 25.5 to 114.0 µg/m3 across study areas. For each 10 µg/m3 increase in cycle-specific PM2.5, the hazard ratio for fecundability was 0.951 (95 % confidence interval: 0.950-0.953). The association was more pronounced in women who were older, with urban household registration, history of pregnancy, higher body mass index (BMI), hypertension, without exposure to tobacco, or whose male partners were older, with higher BMI, or hypertension.

CONCLUSION

In this population-based prospective cohort, ambient cycle-specific PM2.5 exposure was associated with reduced fecundability. These findings may support the adverse implications of severe air pollution on reproductive health.

Air pollution and fecundability in a North American preconception cohort study

BACKGROUND

Animal and epidemiologic studies indicate that air pollution may adversely affect fertility. However, the level of evidence is limited and specific pollutants driving the association are inconsistent across studies.

METHODS

We used data from a web-based preconception cohort study of pregnancy planners enrolled during 2013-2019 (Pregnancy Study Online; PRESTO). Eligible participants self-identified as female, were aged 21-45 years, resided in the United States (U.S.) or Canada, and were trying to conceive without fertility treatments. Participants completed a baseline questionnaire and bi-monthly follow-up questionnaires until conception or 12 months. We analyzed data from 8,747 participants (U.S.: 7,304; Canada: 1,443) who had been trying to conceive for < 12 cycles at enrollment. We estimated residential ambient concentrations of particulate matter < 2.5 µm (PM2.5), nitrogen dioxide (NO2), and ozone (O3) using validated spatiotemporal models specific to each country. We fit country-specific proportional probabilities regression models to estimate the association between annual average, menstrual cycle-specific, and preconception average pollutant concentrations with fecundability, the per-cycle probability of conception. We calculated fecundability ratios (FRs) and 95% confidence intervals (CIs) and adjusted for individual- and neighborhood-level confounders.

RESULTS

In the U.S., the FRs for a 5-µg/m3 increase in annual average, cycle-specific, and preconception average PM2.5 concentrations were 0.94 (95% CI: 0.83, 1.08), 1.00 (95% CI: 0.93, 1.07), and 1.00 (95% CI: 0.93, 1.09), respectively. In Canada, the corresponding FRs were 0.92 (95% CI: 0.74, 1.16), 0.97 (95% CI: 0.87, 1.09), and 0.94 (95% CI: 0.80, 1.09), respectively. Likewise, NO2 and O3 concentrations were not strongly associated with fecundability in either country.

CONCLUSIONS

Neither annual average, menstrual cycle-specific, nor preconception average exposure to ambient PM2.5, NO2, and O3 were appreciably associated with reduced fecundability in this cohort of pregnancy planners.

Exposure to Particulate Matter Air Pollution and Age of Menarche in a Nationwide Cohort of U.S. Girls

BACKGROUND

It remains unclear whether in utero and childhood exposure to air pollution affects pubertal development, particularly age of menarche in girls.

OBJECTIVE

The aim of this study was to determine whether residential ambient particulate matter (PM) exposure in utero and during childhood is associated with age of menarche.

METHODS

We studied 5,201 girls in the Growing Up Today Study 2 (2004-present) who were 10-17 y of age at enrollment (47.7% premenarchal; 52.3% postmenarchal). Exposure to three size fractions of PM [fine PM with aerodynamic diameter ≤ 2.5 μ m (PM 2.5 ), PM with aerodynamic diameters between  2.5 μ m  and  10 μ m (PM 2.5 - 10 ), and PM with aerodynamic diameter 10 μ m (PM 10 )] was assigned based on maternal residential address, updated every 2 y, using nationwide spatiotemporal models. We estimated average PM exposure in utero, and time-varying windows: annual average exposure in the prior 1 and 2 y and cumulative average from birth. Age of menarche was self-reported on three surveys administered in 2004, 2006, and 2008. We calculated hazard ratios (HR) for menarche for an interquartile range (IQR) increase in PM exposure using Cox proportional hazard models adjusting for potential confounders.

RESULTS

Girls attained menarche at 12.3 y of age on average. In the adjusted model, higher residential exposure to ambient PM 2.5 during all time windows was associated with earlier age of menarche. The HRs of menarche for each IQR (4   μ g / m 3 ) increase in exposure to PM 2.5 during the in utero period, 1 y prior to menarche, and throughout childhood were 1.03 [95% confidence interval (CI): 1.00, 1.06], 1.06 (95% CI: 1.02, 1.10) and 1.06 (95% CI: 1.02, 1.10), respectively. Effect estimates for PM 10 exposure were similar, albeit attenuated, for all time windows. PM 2.5 - 10 exposure was not associated with age of menarche.

DISCUSSION

Among a large, nationwide, prospective cohort of U.S. girls, higher exposure to PM 2.5 and PM 10 in utero and throughout childhood was associated with an earlier age of menarche. Our results suggest that PM 2.5 and PM 10 may have endocrine-disrupting properties that could lead to altered timing of menarche. https://doi.org/10.1289/EHP12110.

Association between traffic-related air pollution exposure and fertility-assisted births

Previous studies have suggested that traffic-related air pollution is associated with adverse fertility outcomes, such as reduced fecundability and subfertility. The purpose of this research is to investigate if PM_2.5 exposure prior to conception or traffic-related exposures (traffic density and distance to nearest major roadway) at birth address is associated with fertility-assisted births. We obtained all live and still births from the Massachusetts state birth registry with an estimated conception date between January 2002 through December 2008. All births requiring fertility drugs or assisted reproductive technology were identified as cases. We randomly selected 2000 infants conceived each year to serve as a common control group. PM_2.5 exposure was assessed using 4 km spatial satellite remote sensing, meteorological and land use spatiotemporal models at geocoded birth addresses for the year prior to conception. The mean PM_2.5 level was 9.81 µg m^-3 (standard deviation = 1.70 µg m^-3), with a maximum of 14.27 µg m^-3. We calculated crude and adjusted fertility treatment odds ratios (ORs) and 95% confidence intervals (CI) per interquartile range of 1.72 µg m^-3 increase in PM_2.5 exposure. Our final analyses included 10 748 fertility-assisted births and 12 225 controls. After adjusting for parental age, marital status, race, maternal education, insurance status, parity, and year of birth, average PM_2.5 exposure during the year prior to conception was weakly associated with fertility treatment (OR: 1.01; 95% CI: 0.97, 1.05). Fertility-assisted births were inversely associated with traffic density (highest quartile compared to lowest quartile, OR: 0.92; 95% CI: 0.83, 1.02) and positively associated with distance from major roadway (OR per 100 m: 1.01; 95% CI: 1.00, 1.02) in adjusted analyses. We did not find strong evidence to support an adverse relationship between traffic-related air pollution exposure and fertility-assisted births.

Associations between Residential Greenspace and Fecundability in a North American Preconception Cohort Study

BACKGROUND

Residential green space can have positive physiological effects on human health through various mechanisms, including reducing stress and/or depression or facilitating physical activity. Although green space has been consistently associated with improved birth outcomes in several studies, there has been limited study of its effect on other reproductive outcomes, including fertility.

OBJECTIVE

We examined associations between residential green space and fecundability, the per-cycle probability of conception.

METHODS

We analyzed data from 8,563 female participants enrolled between 2013 and 2019 in Pregnancy Study Online (PRESTO), a prospective preconception cohort study of North American couples attempting conception. Participants completed a baseline questionnaire on sociodemographic, behavioral, and reproductive factors, and bimonthly follow-up questionnaires for up to 12 months to ascertain pregnancies. Using geocoded addresses, we calculated residential green space exposure using the Normalized Difference Vegetation Index (NDVI) within 50-, 100-, 250-, and 500 -m buffers across multiple temporal scales: annual maximum, seasonal maximum, and seasonal mean. We used proportional probabilities regression models to estimate fecundability ratios (FRs), adjusting for sociodemographic, behavioral, and neighborhood characteristics. We also evaluated the extent to which associations were mediated by reductions in perceived stress or depressive symptoms and increased physical activity.

RESULTS

When comparing the highest (≥ 0.8 ) with the lowest (< 0.2 ) NDVI exposures within 50 m , we observed positive associations in the annual maximum NDVI [FR: 1.33; 95% confidence interval (CI): 1.06, 1.67] and seasonal maximum NDVI (FR: 1.19; 95% CI: 1.00, 1.41) models, but little association in the seasonal mean NDVI models (FR: 0.98; 95% CI: 0.73, 1.30). Restricted cubic splines showed evidence of nonlinearity in this association. Results were similar across buffer distances. Perceived stress, depressive symptoms, and physical activity explained ≤ 5 : 0 % of mediation across all NDVI metrics.

DISCUSSION

In this cohort, greater residential green space was associated with a modest increase in fecundability. https://doi.org/10.1289/EHP10648.

Indoor and outdoor air pollution and couple fecundability: a systematic review

BACKGROUND

Air pollution is both a sensory blight and a threat to human health. Inhaled environmental pollutants can be naturally occurring or human-made, and include traffic-related air pollution (TRAP), ozone, particulate matter (PM) and volatile organic compounds, among other substances, including those from secondhand smoking. Studies of air pollution on reproductive and endocrine systems have reported associations of TRAP, secondhand smoke (SHS), organic solvents and biomass fueled-cooking with adverse birth outcomes. While some evidence suggests that air pollution contributes to infertility, the extant literature is mixed, and varying effects of pollutants have been reported.

OBJECTIVE AND RATIONALE

Although some reviews have studied the association between common outdoor air pollutants and time to pregnancy (TTP), there are no comprehensive reviews that also include exposure to indoor inhaled pollutants, such as airborne occupational toxicants and SHS. The current systematic review summarizes the strength of evidence for associations of outdoor air pollution, SHS and indoor inhaled air pollution with couple fecundability and identifies gaps and limitations in the literature to inform policy decisions and future research.

SEARCH METHODS

We performed an electronic search of six databases for original research articles in English published since 1990 on TTP or fecundability and a number of chemicals in the context of air pollution, inhalation and aerosolization. Standardized forms for screening, data extraction and study quality were developed using DistillerSR software and completed in duplicate. We used the Newcastle-Ottawa Scale to assess risk of bias and devised additional quality metrics based on specific methodological features of both air pollution and fecundability studies.

OUTCOMES

The search returned 5200 articles, 4994 of which were excluded at the level of title and abstract screening. After full-text screening, 35 papers remained for data extraction and synthesis. An additional 3 papers were identified independently that fit criteria, and 5 papers involving multiple routes of exposure were removed, yielding 33 articles from 28 studies for analysis. There were 8 papers that examined outdoor air quality, while 6 papers examined SHS exposure and 19 papers examined indoor air quality. The results indicated an association between outdoor air pollution and reduced fecundability, including TRAP and specifically nitrogen oxides and PM with a diameter of ≤2.5 µm, as well as exposure to SHS and formaldehyde. However, exposure windows differed greatly between studies as did the method of exposure assessment. There was little evidence that exposure to volatile solvents is associated with reduced fecundability.

WIDER IMPLICATIONS

The evidence suggests that exposure to outdoor air pollutants, SHS and some occupational inhaled pollutants may reduce fecundability. Future studies of SHS should use indoor air monitors and biomarkers to improve exposure assessment. Air monitors that capture real-time exposure can provide valuable insight about the role of indoor air pollution and are helpful in assessing the short-term acute effects of pollutants on TTP.

Association Between Neighborhood Disadvantage and Fertility Among Pregnancy Planners in the US

IMPORTANCE

Decades of inequitable policies in the US have yielded disparities in neighborhood quality, and some studies show that living in a socioeconomically disadvantaged neighborhood is associated with worse health outcomes, including reproductive health outcomes. However, no US studies to date have directly examined the association between residence in disadvantaged neighborhoods and fertility.

OBJECTIVE

To examine the association between residence in disadvantaged neighborhoods and fecundability, a sensitive marker of fertility with many health implications.

DESIGN, SETTING, AND PARTICIPANTS

This prospective preconception cohort study used the Pregnancy Study Online, for which baseline data were collected from June 19, 2013, through April 12, 2019. The study included 6356 participants who identified as female, were 21 to 45 years of age, were attempting conception without fertility treatment, and provided a valid residential address in the contiguous US at enrollment.

EXPOSURES

A standardized area deprivation index (ADI) derived at the census block group level applied to each residential address.

MAIN OUTCOMES AND MEASURES

Fecundability, the per-cycle probability of conception, via questionnaires that were completed every 8 weeks for 12 months, until conception or a censoring event. Proportional probabilities models were used to estimate fecundability ratios and 95% CIs for associations between ADI and fecundability. Restricted cubic splines were also implemented to examine nonlinearity. Models were adjusted for demographic characteristics and factors associated with fertility. The study's a priori hypothesis was that higher levels of neighborhood disadvantage would be associated with decreased fecundability.

RESULTS

Among 6356 participants, 3725 pregnancies were observed for 27 427 menstrual cycles of follow-up. The mean (SD) baseline age was 30.0 (4.1) years, and most participants were non-Hispanic White (5297 [83.3%]) and nulliparous (4179 [65.7%]). Comparing the top and bottom deciles of disadvantaged neighborhood status, adjusted fecundability ratios were 0.79 (95% CI, 0.66-0.96) for national-level ADI rankings and 0.77 (95% CI, 0.65-0.92) for within-state ADI rankings. Restricted cubic splines showed some evidence of nonlinearity in the association. Associations were slightly stronger among participants with lower annual incomes (<$50 000).

CONCLUSIONS AND RELEVANCE

In this cohort study, residence in a socioeconomically disadvantaged neighborhood was associated with moderately decreased fecundability. If confirmed in other studies, these results suggest that investments to reduce disadvantaged neighborhood status may yield positive cobenefits for fertility.

Ambient Air Pollution Exposure Assessments in Fertility Studies: a Systematic Review and Guide for Reproductive Epidemiologists

Purpose of Review

We reviewed the exposure assessments of ambient air pollution used in studies of fertility, fecundability, and pregnancy loss.

Recent Findings

Comprehensive literature searches were performed in the PUBMED, Web of Science, and Scopus databases. Of 168 total studies, 45 met the eligibility criteria and were included in the review. We find that 69% of fertility and pregnancy loss studies have used one-dimensional proximity models or surface monitor data, while only 35% have used the improved models, such as land-use regression models (4%), dispersion/chemical transport models (11%), or fusion models (20%). No published studies have used personal air monitors.

Summary

While air pollution exposure models have vastly improved over the past decade from a simple, one-dimensional distance or air monitor data to models that incorporate physiochemical properties leading to better predictive accuracy, precision, and increased spatiotemporal variability and resolution, the fertility literature has yet to fully incorporate these new methods. We provide descriptions of each of these air pollution exposure models and assess the strengths and limitations of each model, while summarizing the findings of the literature on ambient air pollution and fertility that apply each method.

Semen quality and sperm DNA methylation in relation to long-term exposure to air pollution in fertile men: A cross-sectional study

Some studies have examined the association between air pollution and semen quality. While it is less of evidence on the sperm quality after long-term air pollution exposure, especially the co-exposure of different air pollution components. Additionally, the role of DNA methylation in it hasn't been confirmed. This study aimed to investigate whether long-term exposure to air pollution was associated with semen quality, as well as to explore the effect of sperm DNA methylation in such association. From 2014 to 2016, 1607 fertile men were enrolled to evaluate 14 parameters of semen quality. Exposure window was defined as one-year before semen sampling. Multivariable linear regression and weighted quantile sum (WQS) regression model were used to investigate the association between six air pollutants co-exposure and semen quality. Sensitivity analysis regarding at the normal semen quality group was also conducted. Semen samples were randomly selected from 200 participants to detect the genomic 5-methylcytosine (5 mC) and 5-hydroxymethylcytosine (5-hmC) levels in sperm. In the total population, PM10, PM2.5, SO2, and NO2 were negatively associated with sperm total motility (PM10: β = -2.67, P = 0.009; PM2.5: β = -2.86, P = 0.004; SO2: β = -2.32, P = 0.011; NO2: β = -2.21, P = 0.012). Results of the normal semen quality group were consistent with those from the whole population. WQS regression results indicated significant decreasing sperm total motility after the co-exposure of the six air pollutants (β = -1.64, P = 0.003) in whole participants. Wherein, PM10 accounted for largest proportion (43.4%). The 5-hmC level was positively associated with PM10 exposure (β = 0.002, P < 0.001). Long-term exposure to PM10, PM2.5, SO2, and NO2, as well as co-exposure to six air pollutants, reduced semen quality in fertile men. As the most significant contributor of air pollutant, PM10 exposure decreased sperm DNA methylation.

Assessment of the association between prenatal exposure to multiple ambient pollutants and preterm birth: A prospective cohort study in Jinan, east China

Air pollution has been documented with a series of adverse pregnancy outcomes, yet their reproductive and developmental toxicity on human beings has not been fully elucidated. Here, we analyzed the geographic distribution of Jinan and examined its contribution to air pollution. After adjusting demographic variables and environmental co-pollutants, we built statistical models based on 424 couples and checked different air pollutants on their pregnancy outcomes. We find that Jinan is tightly surrounded by mountains from 3 of 4 sides, geographically resulting in a typical basin texture that hinders the diffusion of ambient pollutants. Of 424 pregnant women enrolled in this study, 17 subjects were diagnosed with preterm birth. Using air quality index (AQI) as an integrated indicator of PM₁₀, PM_2.5, SO₂, NO₂, CO, and O₃, we found that each interquartile range (IQR) increase in AQI was associated with 11% increased odds of preterm birth. Also, elevating PM_2.5, PM₁₀, SO₂, and O₃ led to different increased risk levels of preterm birth. By running the generalized additive model analyses, the association of AQI and preterm birth was further confirmed. In conclusion, based on samples in Jinan, east China, prenatal exposure to multiple ambient pollutants is associated with reduced gestational age and increased risk of preterm birth.

Fine particulate matter and polycystic ovarian morphology

BACKGROUND

Polycystic ovary morphology (PCOM) is an ultrasonographic finding that can be present in women with ovulatory disorder and oligomenorrhea due to hypothalamic, pituitary, and ovarian dysfunction. While air pollution has emerged as a possible disrupter of hormone homeostasis, limited research has been conducted on the association between air pollution and PCOM.

METHODS

We conducted a longitudinal cohort study using electronic medical records data of 5,492 women with normal ovaries at the first ultrasound that underwent a repeated pelvic ultrasound examination during the study period (2004-2016) at Boston Medical Center. Machine learning text algorithms classified PCOM by ultrasound. We used geocoded home address to determine the ambient annual average PM2.5 exposures and categorized into tertiles of exposure. We used Cox Proportional Hazards models on complete data (n = 3,994), adjusting for covariates, and additionally stratified by race/ethnicity and body mass index (BMI).

RESULTS

Cumulative exposure to PM2.5 during the study ranged from 4.9 to 17.5 µg/m3 (mean = 10.0 μg/m3). On average, women were 31 years old and 58% were Black/African American. Hazard ratios and 95% confidence intervals (CI) comparing the second and third PM2.5 exposure tertile vs. the reference tertile were 1.12 (0.88, 1.43) and 0.89 (0.62, 1.28), respectively. No appreciable differences were observed across race/ethnicity. Among women with BMI ≥ 30 kg/m2, we observed weak inverse associations with PCOM for the second (HR: 0.93, 95% CI: 0.66, 1.33) and third tertiles (HR: 0.89, 95% CI: 0.50, 1.57).

CONCLUSIONS

In this study of reproductive-aged women, we observed little association between PM2.5 concentrations and PCOM incidence. No dose response relationships were observed nor were estimates appreciably different across race/ethnicity within this clinically sourced cohort.

Air pollution and fecundability: Results from a Danish preconception cohort study

BACKGROUND

Animal and epidemiologic studies indicate that air pollution may adversely affect fertility. Epidemiologic studies have been restricted largely to couples undergoing fertility treatment or have retrospectively ascertained time-to-pregnancy among pregnant women.

OBJECTIVES

We examined the association between residential ambient air pollution and fecundability, the per-cycle probability of conception, in a large preconception cohort of Danish pregnancy planners.

METHODS

During 2007-2018, we used the Internet to recruit and follow women who were trying to conceive without the use of fertility treatment. Participants completed an online baseline questionnaire eliciting socio-demographic characteristics, lifestyle factors, and medical and reproductive histories and follow-up questionnaires every 8 weeks to ascertain pregnancy status. We determined concentrations of ambient nitrogen oxides (NOx ), nitrogen dioxide (NO2 ), carbon monoxide (CO), ozone (O3 ), particulate matter <2.5 µm (PM2.5 ) and <10 µm (PM10 ), and sulphur dioxide (SO2 ) at each participant's residential address. We calculated average exposure during the year before baseline, during each menstrual cycle over follow-up and during the entire pregnancy attempt time. We used proportional probabilities regression models to estimate fecundability ratios (FRs) and 95% confidence intervals (CIs), adjusting for potential confounders and co-pollutants. The analysis was restricted to the 10,183 participants who were trying to conceive for <12 cycles at study entry whose addresses could be geocoded.

RESULTS

During 12 months of follow-up, 73% of participants conceived. Higher concentrations of PM2.5 and PM10 were associated with small reductions in fecundability. For example, the FRs for a one interquartile range (IQR) increase in PM2.5 (IQR = 3.2 µg/m3 ) and PM10 (IQR = 5.3 µg/m3 ) during each menstrual cycle were 0.93 (95% CI: 0.87, 0.99) and 0.91 (95% CI: 0.84, 0.99), respectively. Other air pollutants were not appreciably associated with fecundability.

CONCLUSIONS

In this preconception cohort study of Danish women, residential exposures to PM2.5 and PM10 were associated with reduced fecundability.

Optimizing natural fertility: a committee opinion

This committee opinion provides practitioners with suggestions for optimizing the likelihood of achieving pregnancy in couples or individuals attempting conception who have no evidence of infertility. This document replaces the document of the same name previously published in 2013 (Fertil Steril 2013;100:631-7).

Environmental Factors Involved in Maternal Morbidity and Mortality

Nongenetic, environmental factors contribute to maternal morbidity and mortality through chemical exposures via air, water, soil, food, and consumer products. Pregnancy represents a particularly sensitive window of susceptibility during which physiological changes to every major organ system increase sensitivity to chemicals that can impact a woman's long-term health. Nonchemical stressors, such as low socioeconomic status, may exacerbate the effects of chemical exposures on maternal health. Racial/ethnic minorities are exposed disproportionately to both chemicals and nonchemical stressors, which likely contribute to the observed health disparities for maternal morbidities and mortality. Epidemiological studies linking exposures to adverse maternal health outcomes underscore the importance of environmental health impacts, and mechanistic studies in model systems reveal how chemicals perturb biological pathways and processes. Environmental stressors are associated with a variety of immediate maternal health impacts, including hypertensive disorders of pregnancy, fibroids, and infertility, as well as long-term maternal health impacts, such as higher risk of breast cancer and metabolic disorders. Identifying and reducing a pregnant woman's environmental exposures is not only beneficial to her offspring but also important to preserve her short- and long-term health.

Association between exposure to airborne particulate matter less than 2.5 μm and human fecundity in China

BACKGROUND

Whether exposure to airborne particulate matter less than 2.5 μm (PM_2.5) could impact human fecundity is unclear. We aimed to evaluate the potential impact of PM_2.5 exposure on time to pregnancy (TTP) and the prevalence of infertility in the general Chinese population.

METHOD

We collected reproductive information, sociodemographic characteristics, and lifestyle data of 10,211 couples at risk of pregnancy from a large-scale community-based fertility survey in China. Then, we estimated each participant's 1-year, 3-year, and 5-year average PM_2.5 exposure levels based on remote sensing information. After adjusting for demographic, lifestyle, and environmental co-variables, discrete-time Cox regression models were used to estimate the fecundability odds ratio (FOR) per 10 μg/m³ change of PM_2.5. We also estimated the odds ratio (OR) of infertility per 10 μg/m³ change of PM_2.5, using logistic regression models.

FINDINGS

Among the 10,211 couples, 6,875 (67%) had conceived spontaneously, with a median TTP of 5 months (interquartile range: 2-10 months). The median PM_2.5 exposure was 56.8 μg/m³, with a wide range of 9.2-93.5 μg/m³. In Cox regression models, each increase of 10 μg/m³ in the 1-year average PM_2.5 exposure was associated with a significant decrease in fecundity by 11% (FOR: 0.89; 95% confidence interval [CI]: 0.86-0.92). In logistic regression models, it was also associated with an 20% increased likelihood of infertility (OR: 1.20; 95% CI: 1.13-1.27).

CONCLUSION

PM_2.5 exposure was associated with reduced human fecundity, presented by a longer TTP and higher odds of infertility, which might explain the increased infertility rates in areas with heavy PM_2.5 pollution.

Residential proximity to major roads and fecundability in a preconception cohort

Supplemental Digital Content is available in the text.

Emerging evidence from animal and human studies indicates that exposure to traffic-related air pollution may adversely affect fertility.

Ambient air pollution and in vitro fertilization treatment outcomes

STUDY QUESTION

Is air pollution associated with IVF treatment outcomes in the USA?

SUMMARY ANSWER

We did not find clear evidence of a meaningful association between reproductive outcomes and average daily concentrations of particulate matter with an aerodynamic diameter ≤2.5 μm (PM2.5) and ozone (O3).

WHAT IS KNOWN ALREADY

Maternal exposure to air pollution such as PM2.5, nitrogen oxides, carbon monoxide or O3 may increase risks for adverse perinatal outcomes. Findings from the few studies using data from IVF populations to investigate associations between specific pollutants and treatment outcomes are inconclusive.

STUDY DESIGN, SIZE AND DURATION

Retrospective cohort study of 253 528 non-cancelled fresh, autologous IVF cycles including 230 243 fresh, autologous IVF cycles with a transfer of ≥1 embryo was performed between 2010 and 2012.

PARTICIPANTS/MATERIALS, SETTING, METHODS

We linked 2010-2012 National ART Surveillance System data for fresh, autologous IVF cycles with the ambient air pollution data generated using a Bayesian fusion model available through the Centers for Disease Control and Prevention's Environmental Public Health Tracking Network. We calculated county-level average daily PM2.5 and O3 concentrations for three time periods: cycle start to oocyte retrieval (T1), oocyte retrieval to embryo transfer (T2) and embryo transfer +14 days (T3). Multivariable predicted marginal proportions from logistic and log-linear regression models were used to estimate adjusted risk ratios (aRR) and 95% CI for the association between reproductive outcomes (implantation rate, pregnancy and live birth) and interquartile increases in PM2.5 and O3. The multipollutant models were also adjusted for patients and treatment characteristics and accounted for clustering by clinic and county of residence.

MAIN RESULTS AND THE ROLE OF CHANCE

For all exposure periods, O3 was weakly positively associated with implantation (aRR 1.01, 95% CI 1.001-1.02 for T1; aRR 1.01, 95% CI 1.001-1.02 for T2 and aRR 1.01, 95% CI 1.001-1.02 for T3) and live birth (aRR 1.01, 95% CI 1.002-1.02 for T1; aRR 1.01, 95% CI 1.004-1.02 for T2 and aRR 1.02, 95% CI 1.004-1.03 for T3). PM2.5 was not associated with any of the reproductive outcomes assessed.

LIMITATIONS, REASONS FOR CAUTION

The main limitation of this study is the use of aggregated air pollution data as proxies for individual exposure. The weak positive associations found in this study might be related to confounding by factors that we were unable to assess and may not reflect clinically meaningful differences.

WIDER IMPLICATIONS OF THE FINDINGS

More research is needed to assess the impact of air pollution on reproductive function.

STUDY FUNDING/COMPETING INTEREST(S)

None.

Ambient ozone pollution is associated with decreased semen quality: longitudinal analysis of 8945 semen samples from 2015 to 2018 and during pollution-control period in Beijing, China

Previous studies suggest that air pollution has a negative effect on semen quality. However, most studies are cross-sectional and the results are controversial. This study investigated the associations between air pollutants (PM_2.5, PM₁₀, SO₂, NO₂, CO, and O₃) and semen quality among sperm donation candidates, especially when the air pollution was artificially controlled in Beijing, China. We analyzed 8945 semen samples in the human sperm bank of Peking University Third Hospital (Beijing, China) from October 2015 to May 2018. Air pollution data during the entire period (0–90 days prior) and key stages (0–9, 10–14, and 70–90 days prior) of sperm development were collected from the China National Environmental Monitoring Centre. The association between air pollutants and semen parameters (sperm concentration and progressive motility) was analyzed by a mixed model adjusted for age, abstinence duration, month, and average ambient temperature. Only O₃ during key stages of 0–9 days and 10–14 days and the entire period was negatively associated with sperm concentration between 2015 and 2018 (P < 0.01). During the period of air pollution control from November 2017 to January 2018, except for the increase in O₃ concentration, other five pollutants’ concentrations decreased compared to those in previous years. In this period, the sperm concentration decreased (P < 0.001). During the pollution-control period, O₃ exposure 10–14 days prior was negatively associated with sperm concentration (95% CI: −0.399–−0.111; P < 0.001). No significant association was found between the other five pollutants and semen quality during that period. Our study suggested that only O₃ exposure was harmful to semen quality. Therefore, O₃ should not be neglected during pollution control operation.

Association between Female Reproductive Health and Mancozeb: Systematic Review of Experimental Models

Mancozeb is a widely used fungicide approved for use in agriculture in many countries with long persistence in the environment and consequent bioaccumulation in tissues and biological fluids. Despite the large amount of studies published in recent years, the relationship between mancozeb exposure and female reproductive health is not fully elucidated. In order to summarize current evidence on mancozeb exposure and female reproductive disease, we performed a systematic review of literature. Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were used to make this review. An adapted version of the National Toxicology Program’s Office of Health and Assessment and Translation (OHAT) framework was used to evaluate the risk of bias. Electronic search on two databases (PubMed and Scopus) was used to find experimental studies (in vitro and in vivo) on mancozeb exposure. The database search identified 250 scientific articles, 20 of which met our inclusion criteria. Selected data were then reviewed and summarized in tables. Overall, mancozeb represents a hazard for female reproductive health, with different mechanisms of action. Undoubtedly more experimental and epidemiological studies are required to definitively validate mancozeb as reproductive toxicant.

Association between in vitro fertilization success rate and ambient air pollution: a possible explanation of within-year variation of in vitro fertilization success rate

Objective

To evaluate patterns in air pollution concentrations and in vitro fertilization (IVF) success rates using data from a large, long-term clinical database.

Methods

We conducted a retrospective cohort study investigating South Korean women who pursued IVF and embryo transfer (IVF-ET) between 2011 and 2017. Hourly concentrations of air pollutants measured at 318 air quality monitoring sites in South Korea between 2011 and 2017 were obtained from the National Institute of Environmental Research. Monthly trends in pregnancy rates and concentrations of air pollutants were assessed.

Results

A total of 34,427 IVF-ET cycles in 18,478 patients were analyzed. The mean age of women at the time of IVF-ET was 36.6 years. The clinical pregnancy rate in the IVF-ET cycle was 30%. Analysis of pregnancy failure rates by month showed that IVF-ET failure rates tended to be higher in March and April and lower in July and August. Concentrations of air pollutants including particulate matter (PM) less than 10 μm in diameter, PM less than 2.5 μm in diameter, sulfur dioxide, nitrogen dioxide, and carbon monoxide were highest in March and April and lowest between July and September.

Conclusion

Within-year variations were similar between IVF-ET failure rates and air pollution concentrations based on analysis of a large, long-term database. Specifically, IVF-ET success rates were highest when PM concentrations were lowest. Further studies are warranted to examine the mechanisms accounting for the association between IVF success and air pollutant exposure.

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.

Association between ambient air pollution and pregnancy rate in women who underwent IVF

STUDY QUESTION

Are the concentrations of five criteria air pollutants associated with probabilities of biochemical pregnancy loss and intrauterine pregnancy in women?

SUMMARY ANSWER

Increased concentrations of ambient particulate matter (PM10), nitrogen dioxide (NO2), carbon monoxide (CO) during controlled ovarian stimulation (COS) and after embryo transfer were associated with a decreased probability of intrauterine pregnancy.

WHAT IS KNOWN ALREADY

Exposure to high ambient air pollution was suggested to be associated with low fertility and high early pregnancy loss in women.

STUDY DESIGN, SIZE, DURATION

Using a retrospective cohort study design, we analysed 6621 cycles of 4581 patients who underwent one or more fresh IVF cycles at a fertility centre from January 2006 to December 2014, and lived in Seoul at the time of IVF treatment.

PARTICIPANTS/MATERIALS, SETTING, METHODS

To estimate patients' individual exposure to air pollution, we computed averages of hourly concentrations of five air pollutants including PM10, NO2, CO, sulphur dioxide (SO2) and ozone (O3) measured at 40 regulatory monitoring sites in Seoul for each of the four exposure periods: period 1 (start of COS to oocyte retrieval), period 2 (oocyte retrieval to embryo transfer), period 3 (embryo transfer to hCG test), and period 4 (start of COS to hCG test). Hazard ratios (HRs) from the time-varying Cox-proportional hazards model were used to estimate probabilities of biochemical pregnancy loss and intrauterine pregnancy for an interquartile range (IQR) increase in each air pollutant concentration during each period, after adjusting for individual characteristics. We tested the robustness of the result using generalised linear mixed model, accounting for within-woman correlation.

MAIN RESULTS AND THE ROLE OF CHANCE

Mean age of the women was 35 years. Average BMI was 20.9 kg/m2 and the study population underwent 1.4 IVF cycles on average. Cumulative pregnancy rate in multiple IVF cycles was 51.3% per person. Survival analysis showed that air pollution during periods 1 and 3 was generally associated with IVF outcomes. Increased NO2 (adjusted HR = 0.93, 95% CI: 0.87, 0.99) and CO (0.94, 95% CI: 0.89, 1.00) during period 1 were associated with decreased probability of intrauterine pregnancy. PM10 (0.92, 95% CI: 0.85, 0.99), NO2 (0.93, 95% CI = 0.86, 1.00) and CO (0.93, 95% CI: 0.87, 1.00) levels during period 3 were also inversely associated with intrauterine pregnancy. Both PM10 (1.17, 95% CI: 1.04 1.33) and NO2 (1.18, 95% CI: 1.03, 1.34) during period 3 showed positive associations with biochemical pregnancy loss.

LIMITATIONS, REASONS FOR CAUTION

The district-specific ambient air pollution treated as an individual exposure may not represent the actual level of each woman's exposure to air pollution. Smoking, working status, parity or gravidity of women, and semen analysis data were not included in the analysis.

WIDER IMPLICATIONS OF THE FINDINGS

This study provided evidence of an association between increased ambient concentrations of PM10, NO2 and CO and reduced probabilities for achieving intrauterine pregnancy using multiple IVF cycle data. Specifically, our results indicated that lower intrauterine pregnancy rates in IVF cycles may be linked to ambient air pollution during COS and the post-transfer period.

STUDY FUNDING/COMPETING INTEREST(S)

This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (2013 R1A6A3A04059017, 2016 R1D1A1B03933410 and 2018 R1A2B6004608) and the National Cancer Center of Korea (NCC-1810220-01). The authors report no conflicts of interest.

TRIAL REGISTRATION NUMBER

N/A.

Association between fertility rate reduction and pre-gestational exposure to ambient fine particles in the United States, 2003-2011

Ambient pollutants are associated with clinical and sub-clinical indicators of infertility, such as poor sperm quality. However, the link between the ambient fine particle (PM_2.5) concentration and the fertility rate (FR) is unclear. In this epidemiological study, we examined the association between PM_2.5 concentration and childlessness in the United States (US). We conducted a nationwide spatiotemporal study of ~29 million births in 520 US counties from 2003 to 2011. We obtained monthly numbers and demographic data of newborns from the Centers for Disease Control and Prevention, and PM_2.5 estimates from a downscaling model of in situ observations and outputs from the Community Multiscale Air Quality Model. We evaluated the association between the mean PM_2.5 concentration and the FR during the gestational (0-8 months before birth) and pre-gestational (9-11 months before birth) periods using a Poisson model with demographic and socioeconomic covariates. We found a significant association between the FR and PM_2.5 exposure during pre-gestation but not gestation. Each 5 μg/m³ increase in pre-gestational PM_2.5 exposure was associated with a 0.7% (0.0%, 1.4%) reduction in the FR. Nonlinear analysis suggested a sublinear association between the reduction in the FR and PM_2.5 concentration without a safety threshold. Additionally, an annual mean reduction of 1.16 (1.15, 1.17) births per 1000 females aged 15-44 years was attributable to PM_2.5. This study established, for the first time, an association in the US between the FR and PM_2.5 concentration, a finding that adds to the extant epidemiological evidence of the effects of ambient pollutants on fertility, and extends the scope of the impact of low air quality on health.

Residential proximity to major roadways and traffic in relation to outcomes of in vitro fertilization

BACKGROUND

Emerging data from animal and human studies suggest that traffic-related air pollution adversely affects early pregnancy outcomes; however evidence is limited.

OBJECTIVE

We examined whether residential proximity to major roadways and traffic, as proxies for traffic-related air pollution, are associated with in vitro fertilization (IVF) outcomes.

METHODS

This analysis included 423 women enrolled in the Environment and Reproductive Health (EARTH) Study, a prospective cohort study, who underwent 726 IVF cycles (2004-2017). Using geocoded residential addresses collected at study entry, we calculated the distance to nearest major roadway and the traffic density within a 100 m radius. IVF outcomes were abstracted from electronic medical records. We used multivariable generalized linear mixed models to evaluate the associations between residential proximity to major roadways and traffic density and IVF outcomes adjusting for maternal age, body mass index, race, education level, smoking status, and census tract median income.

RESULTS

Closer residential proximity to major roadways was statistically significantly associated with lower probability of implantation and live birth following IVF. The adjusted percentage of IVF cycles resulting in live birth for women living ≥400 m from a major roadway was 46% (95% CI 36, 56%) compared to 33% (95% CI 26, 40%) for women living <50 m (p-for-comparison, 0.04). Of the intermediate outcomes, there were suggestive associations between living closer to major roadways and slightly higher estradiol trigger concentrations (p-trend = 0.16) and lower endometrial thickness (p-trend = 0.06). Near-residence traffic density was not associated with outcomes of IVF.

CONCLUSION

Closer residential proximity to major roadways was related to reduced likelihood of live birth following IVF.

Ambient air pollution and semen quality

BACKGROUND

Ambient air pollution is associated with systemic increases in oxidative stress, to which sperm are particularly sensitive. Although decrements in semen quality represent a key mechanism for impaired fecundability, prior research has not established a clear association between air pollution and semen quality. To address this, we evaluated the association between ambient air pollution and semen quality among men with moderate air pollution exposure.

METHODS

Of 501 couples in the LIFE study, 467 male partners provided one or more semen samples. Average residential exposure to criteria air pollutants and fine particle constituents in the 72 days before ejaculation was estimated using modified Community Multiscale Air Quality models. Generalized estimating equation models estimated the association between air pollutants and semen quality parameters (volume, count, percent hypo-osmotic swollen, motility, sperm head, morphology and sperm chromatin parameters). Models adjusted for age, body mass index, smoking and season.

RESULTS

Most associations between air pollutants and semen parameters were small. However, associations were observed for an interquartile increase in fine particulates ≤2.5 µm and decreased sperm head size, including -0.22 (95% CI -0.34, -0.11) µm2 for area, -0.06 (95% CI -0.09, -0.03) µm for length and -0.09 (95% CI -0.19, -0.06) µm for perimeter. Fine particulates were also associated with 1.03 (95% CI 0.40, 1.66) greater percent sperm head with acrosome.

CONCLUSIONS

Air pollution exposure was not associated with semen quality, except for sperm head parameters. Moderate levels of ambient air pollution may not be a major contributor to semen quality.