Adult air pollution exposure and risk of infertility in the Nurses' Health Study II

Supplemental Folate and the Relationship Between Traffic-Related Air Pollution and Livebirth Among Women Undergoing Assisted Reproduction

Traffic-related air pollution has been linked to higher risks of infertility and miscarriage. We evaluated whether folate intake modified the relationship between air pollution and livebirth among women using assisted reproductive technology (ART). Our study included 304 women (513 cycles) presenting to a fertility center in Boston, Massachusetts (2005-2015). Diet and supplements were assessed by food frequency questionnaire. Spatiotemporal models estimated residence-based daily nitrogen dioxide (NO2), ozone, fine particulate, and black carbon concentrations in the 3 months before ART. We used generalized linear mixed models with interaction terms to evaluate whether the associations between air pollutants and livebirth were modified by folate intake, adjusting for age, body mass index, race, smoking, education, infertility diagnosis, and ART cycle year. Supplemental folate intake significantly modified the association of NO2 exposure and livebirth (P = 0.01). Among women with supplemental folate intakes of <800 μg/day, the odds of livebirth were 24% (95% confidence interval: 2, 42) lower for every 20-parts-per-billion increase in NO2 exposure. There was no association among women with intakes of ≥800 μg/day. There was no effect modification of folate on the associations between other air pollutants and livebirth. High supplemental folate intake might protect against the adverse reproductive consequences of traffic-related air pollution.

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.

Time-Varying Exposure to Air Pollution and Outcomes of in Vitro Fertilization among Couples from a Fertility Clinic

BACKGROUND

A few studies suggest that air pollution may decrease fertility, but prospective studies and examinations of windows of susceptibility remain unclear.

OBJECTIVE

We aimed to examine the association between time-varying exposure to nitrogen dioxide ([Formula: see text]), ozone ([Formula: see text]), fine particulate matter [Formula: see text] ([Formula: see text]), and black carbon (BC) on in vitro fertilization (IVF) outcomes.

METHODS

We included 345 women (522 IVF cycles) for the [Formula: see text], [Formula: see text], and [Formula: see text] analyses and 339 women (512 IVF cycles) for the BC analysis enrolled in a prospective cohort at a Boston fertility center (2004–2015). We used validated spatiotemporal models to estimate daily residential exposure to [Formula: see text], [Formula: see text], [Formula: see text], and BC. Multivariable discrete time Cox proportional hazards models with four periods [ovarian stimulation (OS), oocyte retrieval to embryo transfer (ET), ET to implantation, implantation to live birth] estimated odds ratios (OR) and 95% confidence intervals (CI) of failing at IVF. Time-dependent interactions were used to identify vulnerable periods.

RESULTS

An interquartile range (IQR) increase in [Formula: see text], [Formula: see text], and BC throughout the IVF cycle was associated with an elevated odds of failing at IVF prior to live birth ([Formula: see text], 95% CI: 0.95, 1.23 for [Formula: see text]; [Formula: see text], 95% CI: 0.88, 1.28 for [Formula: see text]; and [Formula: see text], 95% CI: 0.96, 1.41 for BC). This relationship significantly varied across the IVF cycle such that the association with higher exposure to air pollution during OS was strongest for early IVF failures. An IQR increase in [Formula: see text], [Formula: see text], and BC exposure during OS was associated with 1.42 (95% CI: 1.20, 1.69), 1.26 (95% CI: 0.96, 1.67), and 1.23 (95% CI: 0.96, 1.59) times the odds of failing prior to oocyte retrieval, and 1.32 (95% CI: 1.13, 1.54), 1.27 (95% CI: 0.98, 1.65), and 1.32 (95% CI: 1.10, 1.59) times the odds of failing prior to ET.

CONCLUSION

Increased exposure to traffic-related pollutants was associated with higher odds of early IVF failure. https://doi.org/10.1289/EHP4601.

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.

The negative impact of the environment on methylation/epigenetic marking in gametes and embryos: A plea for action to protect the fertility of future generations

Life expectancy has increased since World War II, and this may be attributed to several aspects of modern lifestyles. However, now we are faced with a downturn, which seems to be the result of environmental issues. This paradigm is paralleled with reduced human fertility, decreased sperm quality, increased premature ovarian failure, and diminished ovarian reserve syndromes. Endocrine disruptor chemicals and other toxic chemicals, herbicides, pesticides, plasticizers, to mention a few, are a rising concern in today's environment. Some of these are commonly used in the domestic setting: cleaning material and cosmetics and they have a known impact on epigenesis and imprinting via perturbation of methylation processes. Pollution from polyaromatic hydrocarbons, particulate matter <10 and <2.5 μm, and ozone released into the air, all affect fertility. Poor food processing management is a source of DNA adduct formation, which impairs the quality of gametes. An important concern is the nanoparticles that are present in food and are thought to induce oxidative stress. Now is the time to take a step backward. Global management of the environment and food production is required urgently to protect the fertility of future generations.

Ambient Air Pollution Exposure and Fecundability in Women Undergoing In Vitro Fertilization

BACKGROUND

Limited research suggests ambient air pollution impairs fecundity but groups most susceptible have not been identified. We studied whether long-term ambient air pollution exposure prior to an in vitro fertilization (IVF) cycle was associated with successful livebirth, and whether associations were modified by underlying infertility diagnosis.

METHODS

Data on women initiating their 1st autologous IVF cycle in 2012-13 were obtained from four U.S. clinics. Outcomes included pregnancy, pregnancy loss, and livebirth. Annual average exposure to fine particulate matter (PM2.5), PM10, and nitrogen dioxide (NO2) prior to IVF start were estimated at residential address using a validated national spatial model incorporating land-use regression and universal kriging. We also assessed residential distance to major roadway. We calculated risk ratios (RR) using modified Poisson regression and evaluated effect modification (EM) by infertility diagnosis on additive and multiplicative scales.

RESULTS

Among 7,463 eligible participants, 36% had a livebirth. There was a non-significant indication of an association between PM2.5 or NO2 and decreased livebirth and increased pregnancy loss. Near roadway residence was associated with decreased livebirth (RR: 0.96, 95% CI: 0.82, 0.99. There was evidence for EM between high exposure to air pollutants and a diagnosis of diminished ovarian reserve (DOR) or male infertility and decreased livebirth.

CONCLUSIONS

Despite suggestive but uncertain findings for the overall effect of air pollution on fecundity, we found a suggestive indication that there may be synergistic effects of air pollution and DOR or male infertility diagnosis on livebirth. This suggests two possible targets for future research and intervention.

Perimenarchal air pollution exposure and menstrual disorders

STUDY QUESTION

What is the association between perimenarchal exposure to total suspended particulate (TSP) in air, menstrual irregularity phenotypes and time to menstrual cycle regularity?

SUMMARY ANSWER

Exposures to TSP during high school are associated with slightly increased odds of menstrual irregularity and longer time to regularity in high school and early adulthood.

WHAT IS KNOWN ALREADY

The menstrual cycle is responsive to hormonal regulation. Particulate matter air pollution has demonstrated hormonal activity. However, it is not known if air pollution is associated with menstrual cycle regularity.

STUDY DESIGN, SIZE, DURATION

Cross sectional study of 34 832 of the original 116 430 women (29.91%) enrolled in 1989 from the Nurses' Health Study II (NHSII). The follow-up rate for this analytic sample was 97.76% at the 1991 survey.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Annual averages of TSP were available for each year of high school attendance. We created three case definitions including high school menstrual irregularity and androgen excess. The time to menstrual cycle regularity was reported by participants as <1 year, 1-2 years, 3-4 years, 5 years or longer, or never on the baseline questionnaire. Odds ratios and 95% confidence intervals (CI) were calculated for 45 μg/m3 increases in TSP exposure, adjusted for risk factors for menstrual irregularity.

MAIN RESULTS AND THE ROLE OF CHANCE

In multivariable adjusted models, we observed that for every 45 μg/m3 increase in average high school TSP there was an increased odds (95%CI) of 1.08 (1.03-1.14), 1.08 (1.02-1.15) and 1.10 (0.98-1.25) for moderate, persistent, and persistent with androgen excess irregularity phenotypes, respectively. TSP was also associated with a longer time to cycle regularity, with stronger results among women with older ages at menarche and those living in the Northeast or the West.

LIMITATIONS, REASONS FOR CAUTION

The outcomes of menstrual regularity and time to cycle regularity were retrospectively assessed outcomes and may be susceptible to recall bias. There is also the potential for selection bias, as women had to live until 2011 to provide addresses.

WIDER IMPLICATIONS OF THE FINDINGS

Temporal exposure to air pollution in the adolescent and early adulthood window may be especially important, given its association with phenotypes of menstrual irregularity. The data from this study agrees with existing literature regarding air pollution and reproductive tract diseases.

STUDY FUNDING/COMPETING INTEREST(S)

Shruthi Mahalingaiah: Reproductive Scientist Development Program HD000849, and a research grant from the Boston University Department of Obstetrics and Gynecology, Stacey Missmer: R01HD57210 from the National Institute of Child Health and Human Development and the Massachusetts Institute of Technology Center for Environmental Health Sciences Translational Pilot Project Program, R01CA50385 from the National Cancer Institute, Jaime Hart and Francine Laden: 5R01ES017017 from the National Institute for Environmental Health Sciences, Jaime Hart: P30 ES00002 from the National Institute for Environmental Health Sciences at the National Institute of Health, The Nurses' Health Study II is supported by infrastructure grant UM1CA176726 from the National Cancer Institute, NIH, U.S. Department of Health and Human Services The authors have no conflicts of interest to declare.

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

STUDY QUESTION

Does ambient air pollution affect fecundability?

SUMMARY ANSWER

While cycle-average air pollution exposure was not associated with fecundability, we observed some associations for acute exposure around ovulation and implantation with fecundability.

WHAT IS KNOWN ALREADY

Ambient air pollution exposure has been associated with adverse pregnancy outcomes and decrements in semen quality.

STUDY DESIGN, SIZE, DURATION

The LIFE study (2005-2009), a prospective time-to-pregnancy study, enrolled 501 couples who were followed for up to one year of attempting pregnancy.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Average air pollutant exposure was assessed for the menstrual cycle before and during the proliferative phase of each observed cycle (n = 500 couples; n = 2360 cycles) and daily acute exposure was assessed for sensitive windows of each observed cycle (n = 440 couples; n = 1897 cycles). Discrete-time survival analysis modeled the association between fecundability and an interquartile range increase in each pollutant, adjusting for co-pollutants, site, age, race/ethnicity, parity, body mass index, smoking, income and education.

MAIN RESULTS AND THE ROLE OF CHANCE

Cycle-average air pollutant exposure was not associated with fecundability. In acute models, fecundability was diminished with exposure to ozone the day before ovulation and nitrogen oxides 8 days post ovulation (fecundability odds ratio [FOR] 0.83, 95% confidence interval [CI]: 0.72, 0.96 and FOR 0.84, 95% CI: 0.71, 0.99, respectively). However, particulate matter ≤10 microns 6 days post ovulation was associated with greater fecundability (FOR 1.25, 95% CI: 1.01, 1.54).

LIMITATIONS, REASONS FOR CAUTION

Although our study was unlikely to be biased due to confounding, misclassification of air pollution exposure and the moderate study size may have limited our ability to detect an association between ambient air pollution and fecundability.

WIDER IMPLICATIONS OF THE FINDINGS

While no associations were observed for cycle-average ambient air pollution exposure, consistent with past research in the United States, exposure during critical windows of hormonal variability was associated with prospectively measured couple fecundability, warranting further investigation.

STUDY FUNDING/COMPETING INTEREST(S)

This work was supported by the Intramural Research Program of the Eunice Kennedy Shriver National Institute of Child Health and Human Development (Longitudinal Investigation of Fertility and the Environment study contract nos. #N01-HD-3-3355, NO1-HD-#-3356, N01-HD-3-3358 and the Air Quality and Reproductive Health Study Contract No. HHSN275200800002I, Task Order No. HHSN27500008). We declare no conflict of interest.

Air pollution and female fertility: a systematic review of literature

Air pollution is a cause of concern for human health. For instance, it is associated with an increased risk for cancer, cardiovascular and respiratory disorders. In vitro and in vivo studies suggested that air pollutants could act as endocrine disruptors, promote oxidative stress and exert genotoxic effect. Whether air pollution affects female infertility is under debate. The aim of the present study was to conduct a systematic review of studies that evaluated the impact of air pollution on female infertility. We systematically searched the MEDLINE (PubMed) and SCOPUS databases to identify all relevant studies published before October 2017. No time or language restrictions were adopted, and queries were limited to human studies. We also hand-searched the reference lists of relevant studies to ensure we did not miss pertinent studies. The risk of bias and quality assessment of the studies identified were performed using the Newcastle-Ottawa Scale. Primary outcomes were conception rate after spontaneous intercourse and live birth rate after in vitro fertilization (IVF) procedures. Secondary outcomes were first trimester miscarriage, stillbirths, infertility, number of oocytes and embryo retrieved. Eleven articles were included in the analysis. We found that in the IVF population, nitrogen dioxide and ozone were associated with a reduced live birth rate while particulate matter of 10 mm was associated with increased miscarriage. Furthermore, in the general population, particulate matter of 2.5 mm and between 2.5 and 10 mm were associated with reduced fecundability, whereas sulfur dioxide_, carbon monoxide and nitrogen dioxide might promote miscarriage and stillbirths. The main limitation of our findigns resides in the fact that the desegn of studies included are observational and retrospective. Furthermore, there was a wide heterogenity among studies. Although larger trials are required before drawing definitive conclusions, it seems that air pollution could represent a matter of concern for female infertility.

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.

Increment of ambient exposure to fine particles and the reduced human fertility rate in China, 2000-2010

Epidemiological and toxicological studies suggest that exposure to ambient fine particles (PM_2.5) can reduce human reproductive capacity. We previously reported, based on spatial epidemiology, that higher levels of PM_2.5 exposure were associated with a lower fertility rate (FR) in China. However, that study was limited by a lack of temporal variation. Using first-difference regression, we linked temporal changes in FR and PM_2.5 with adjustment for ecological covariates across 2806 counties in China during 2000-2010. Next, we performed a sensitivity analysis of the variation in the PM_2.5-FR association according to (1) geographic region, (2) indicators of the level of development, and (3) PM_2.5 concentrations. Also, we quantified the reduction in the FR attributable to ambient PM_2.5 in China for the first time. The FR decreased by 3.3% (1.2%, 5.3%) for each 10 μg/m³ increment in PM_2.5. The association varied significantly among the geographic regions, but not with the level of development. Nonlinearity analysis suggested a linear exposure-response function with an effect threshold of ~8 μg/m³. We also found that comparing to the 2000 scenario, increment of PM_2.5 in 2010 might result in a reduction of 2.50 (2.44, 2.60) infants per 1000 women aged 15-44 years per year in China. Our results confirm the statistical association between ambient particles and FR and suggest that poor air quality may contribute to childlessness in China.

PM2.5 induces male reproductive toxicity via mitochondrial dysfunction, DNA damage and RIPK1 mediated apoptotic signaling pathway

Recent years, air pollution has been a serious problem, and PM_2.5 is the main air particulate pollutant. Studies have investigated that PM_2.5 is a risky factor to the deterioration of semen quality in males. But, the related mechanism is still unclear. To explore the effect of PM_2.5, Sprague Dawley (SD) rats were exposed to PM_2.5 (0, 1.8, 5.4 and 16.2mg/kg.bw.) through intratracheal instillation. The exposure was performed once every 3days and continued for 30days. In vitro, GC-2spd cells were treated using 0, 50, 100, 200μg/mL PM_2.5 for 24h. The data showed that sperm relative motility rates and density were remarkably decreased, while sperm malformation rates were significantly increased with exposure to the PM_2.5. The expression of Fas/FasL/RIPK1/FADD/Caspase-8/Caspase-3 and the level of 8-OHdG expression in testes were significantly increased after exposure to PM_2.5. Additionally, in vitro the results showed that PM_2.5 inhibited cell viability, increased the release of lactate dehydrogenase (LDH) by increasing reactive oxygen species (ROS) level. And ROS induced-DNA damage led to cell cycle arrest at G0/G1 phases and proliferation inhibition. Similar to the vivo study, the expressions of Fas/FasL/RIPK1/FADD/Caspase-8/Caspase-3 in GC-2spd cells were significantly increased after exposure to PM_2.5 for 24-h. In addition, PM_2.5 decreased the levels of ATP by impairing mitochondria structures, which led to energy metabolism obstruction resulted in the decrease of sperm motility. The above three aspects together resulted in the decrease in sperm quantity and quality.

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.

Increase in fertility following coal and oil power plant retirements in California

BACKGROUND

Few studies have explored the relationship between air pollution and fertility. We used a natural experiment in California when coal and oil power plants retired to estimate associations with nearby fertility rates.

METHODS

We used a difference-in-differences negative binomial model on the incident rate ratio scale to analyze the change in annual fertility rates among California mothers living within 0-5 km and 5-10 km of 8 retired power plants between 2001 and 2011. The difference-in-differences method isolates the portion of the pre- versus post-retirement contrast in the 0-5 km and 5-10 km bins, respectively, that is due to retirement rather than secular trends. We controlled for secular trends with mothers living 10-20 km away. Adjusted models included fixed effects for power plant, proportion Hispanic, Black, high school educated, and aged > 30 years mothers, and neighborhood poverty and educational attainment.

RESULTS

Analyses included 58,909 live births. In adjusted models, we estimated that after power plant retirement annual fertility rates per 1000 women aged 15-44 years increased by 8 births within 5 km and 2 births within 5-10 km of power plants, corresponding to incident rate ratios of 1.2 (95% CI: 1.1-1.4) and 1.1 (95% CI: 1.0-1.2), respectively. We implemented a negative exposure control by randomly selecting power plants that did not retire and repeating our analysis with those locations using the retirement dates from original 8 power plants. There was no association, suggesting that statewide temporal trends may not account for results.

CONCLUSIONS

Fertility rates among nearby populations appeared to increase after coal and oil power plant retirements. Our study design limited the possibility that our findings resulted from temporal trends or changes in population composition. These results require confirmation in other populations, given known methodological limitations of ecologic study designs.

Oocyte exposure to ZnO nanoparticles inhibits early embryonic development through the γ-H2AX and NF-κB signaling pathways

The impacts of zinc oxide nanoparticles on embryonic development following oocyte stage exposure are unknown and the underlying mechanisms are sparsely understood. In the current investigation, intact nanoparticles were detected in ovarian tissue in vivo and cultured cells in vitro under zinc oxide nanoparticles treatment. Zinc oxide nanoparticles exposure during the oocyte stage inhibited embryonic development. Notably, in vitro culture data closely matched in vivo embryonic data, in that the impairments caused by Zinc oxide nanoparticles treatment passed through cell generations; and both gamma-H2AX and NF-kappaB pathways were involved in zinc oxide nanoparticles caused embryo-toxicity. Copper oxide and silicon dioxide nanoparticles have been used to confirm that particles are important for the toxicity of zinc oxide nanoparticles. The toxic effects of zinc oxide nanoparticles emanate from both intact nanoparticles and Zn²⁺. Our investigation along with others suggests that zinc oxide nanoparticles are toxic to the female reproductive system [ovaries (oocytes)] and subsequently embryo-toxic and that precaution should be taken regarding human exposure to their everyday use.

Environmental Toxins and Infertility

While much of the decrease in fertility worldwide is by choice, an increasing number of couples, especially in industrialized countries, are finding conception more difficult and damaged babies more common. The research is quite clear that metals and chemicals in air, water, food, and health-and-beauty aids are damaging fertility in many ways. These toxicants are causing men to experience relentlessly decreasing sperm count and function while women are suffering progressively worse anovulation, impaired implantation, and loss of fetal viability.

Estrous cycle-dependent modulation of in vivo microvascular dysfunction after nanomaterial inhalation

Preconceptive health encompasses male and female reproductive capability. In females, this takes into account each of the stages of the estrous cycle. Microvascular reactivity varies throughout the estrous cycle in response to hormonal changes and in preparation for pregnancy. Microvascular alterations in response to engineered nanomaterial (ENM) exposure have been described within 24-h of inhalation; however, the impact upon the uterine vasculature at differing estrous stages and at late-stage pregnancy is unclear. Female Sprague Dawley (SD) rats (virgin and late stage pregnancy [GD 19]) were exposed to nano-TiO aerosols (173.2 ± 6.4 nm, 10.2 ± 0.46 mg/m³, 5 h) 24-h prior to experimentation leading to a single calculated deposition of 42.2 ± 1.9 µg nano- TiO₂ (exposed) or 0µg (control). Animals were anesthetized, estrous status verified, and prepared for in situ assessment of leukocyte trafficking and vascular function by means of intravital microscopy, Uterine basal arteriolar reactivity was stimulated using iontophoretically applied chemicals: acetylcholine (ACh, 0.025 M; 20, 40, 100, 200 nA), sodium nitroprusside (SNP, 0.05 M; 20, 40, 100 nA), phenylephrine (PE, 0.05 M; 20, 40, 100 nA). Finally, adenosine (ADO, 10⁻⁴ M) was superfused over the tissue to identify maximum diameter. In situ vessel reactivity after exposure was significantly blunted based on estrous stage, but not at late-stage pregnancy. Local uterine venular leukocyte trafficking and systemic inflammatory markers were also significantly affected during preparatory (proestrus), fertile (estrus), and infertile (diestrus) periods after ENM inhalation. Overall, these deficits in reactivity and increased inflammatory activity may impair female fertility after ENM exposure.

Toxic effects and possible mechanisms of hydrogen sulfide and/or ammonia on porcine oocyte maturation in vitro

Previous studies suggest that hydrogen sulfide (H₂S) and ammonia (NH₃) are two major air pollutants which can cause damage to porcine health. However, the mechanisms underlying toxic effects of these compounds on porcine oocyte maturation are not clear. To clarify the mechanism, we evaluated the oocyte quality by detecting some events during oocytes maturation. In our study, porcine oocytes were cultured with different concentrations of Na₂S and/or NH₄Cl in vitro and the rate of the first polar body extrusion decreased significantly. Also, actin filament was seriously disrupted to damage the cytoskeleton which resulted in reduced rate of oocyte maturation. We explored the reactive oxygen species (ROS) generation and found that the ROS level was increased significantly after Na₂S treatment but not after NH₄Cl treatment. Moreover, early stage apoptosis rate was significantly increased and autophagy protein LC3 B expression level was higher in oocytes treated with Na₂S and/or NH₄Cl, which might be caused by ROS elevation. Additionally, exposure to Na₂S and/or NH₄Cl also caused ROS generation and early apoptosis in cumulus cells, which might further affect oocyte maturation in vitro. In summary, our data suggested that exposure to H₂S and/or NH₃ decreased porcine oocyte maturation in vitro, which might be caused by actin disruption, ROS generation, early apoptosis and autophagy.

Exposure to particulate matter air pollution and risk of multiple sclerosis in two large cohorts of US nurses

BACKGROUND

Air pollution is thought to raise the risk of neurological disease by promoting neuroinflammation, oxidative stress, glial activation and cerebrovascular damage. Multiple Sclerosis is a common auto-immune disorder, primarily affecting young women. We conducted, to a large prospective study of particulate matter (PM) exposure and multiple sclerosis (MS) risk in two prospective cohorts of women: the Nurses Health Study (NHS) and the Nurses Health Study II (NHS II).

METHODS

Cumulative average exposure to different size fractions of PM up to the onset of MS was estimated using spatio-temporal models. We used multivariable Cox proportional hazards models to estimate the hazard ratios (HR) and 95% confidence intervals (CI) of MS associated with each size fraction of PM independently. Participants were followed from 1998 through 2004 in NHS and from 1988 through 2007 for NHS II. We conducted additional sensitivity analyses stratified by smoking, region of the US, and age, as well as analyses restricted to women who did not move during the study. Analyses were adjusted for age, ancestry, smoking, body mass index at age 18, region, tract level population density, latitude at age 15, and UV index.

RESULTS

We did not observe significant associations between air pollution and MS risk in our cohorts. Among women in the NHS II, the HRs comparing the top vs. bottom quintiles of PM was 1.11 (95% Confidence Intervals (CI): 0.74, 1.66), 1.04 (95% CI: 0.73, 1.50) and 1.09 (95% CI: 0.73, 1.62) for PM₁₀ (≤10μm in diameter), PM_2.5 (≤2.5μm in diameter), and PM_2.5-10 (2.5 to 10μm in diameter) respectively, and tests for linear trends were not statistically significant. No association between exposure to PM and risk of MS was observed in the NHS.

CONCLUSIONS

In this study, exposure to PM air pollution was not related to MS risk.

Effects of diesel exhaust-derived secondary organic aerosol (SOA) on oocytes: Potential risks to meiotic maturation

Particulate air pollution (PM 2.5) is a worldwide concern. Growing epidemiological evidence has shown pathophysiological effects of PM 2.5, not only on cardiovascular system but also on reproductive performance. The composition and physicochemical properties of PM 2.5 vary depending on the emission sources, climate conditions, and complex chemical reactions in the air. These factors make it difficult to understand the cause and mechanistic details of the adverse health effects of PM 2.5. Here, we show potential impacts of PM 2.5 on oocyte maturation in mice by utilizing diesel exhaust-derived secondary organic aerosol (SOA), a major component of urban PM 2.5. We found that the SOA destabilized microtubules of mouse oocytes and p-benzoquinone is one of the candidates for the microtubule-destabilizing compounds. We propose that some biologically reactive components of PM 2.5 should be prioritized for the regulation of atmospheric quality.

Inverse Association between Ambient Sulfur Dioxide Exposure and Semen Quality in Wuhan, China

Evidence concerning the association between ambient gaseous air pollutant exposures and semen quality is sparse, and findings in previous studies remain largely inconsistent. We enrolled 1759 men and performed 2184 semen examinations at a large reproductive medical center in Wuhan, China, between 2013 and 2015. Inverse distance weighting interpolation was performed to estimate individual exposures to SO₂, NO₂, CO, and O₃ during the entire period (lag 0-90 days) and key periods (lag 0-9, 10-14, 70-90 days) of sperm development. Linear mixed models were used to analyze exposure-response relationships. SO₂ exposure with 0-90 days lag was significantly associated with monotonically decreased sperm concentration (β for each interquartile range increase of exposure: -0.14; 95% CI: -0.23, -0.05), sperm count (-0.21; -0.30, -0.12) and total motile sperm count (-0.16; -0.25, -0.08). Significant associations were observed for total and progressive motility only when SO₂ exposure was at the highest quintile (all P_trend < 0.05). Similar trends were observed for SO₂ exposure with 70-90 days lag. NO₂, CO, or O₃ exposure was not significantly associated with semen quality. Our results suggest that ambient SO₂ exposure adversely affects semen quality and highlight the potential to improve semen quality by reducing ambient SO₂ exposure during early stages of sperm development.

Does air pollution play a role in infertility?: a systematic review

BACKGROUND

Air pollution is involved in many pathologies. These pollutants act through several mechanisms that can affect numerous physiological functions, including reproduction: as endocrine disruptors or reactive oxygen species inducers, and through the formation of DNA adducts and/or epigenetic modifications. We conducted a systematic review of the published literature on the impact of air pollution on reproductive function. Eligible studies were selected from an electronic literature search from the PUBMED database from January 2000 to February 2016 and associated references in published studies. Search terms included (1) ovary or follicle or oocyte or testis or testicular or sperm or spermatozoa or fertility or infertility and (2) air quality or O3 or NO2 or PM2.5 or diesel or SO2 or traffic or PM10 or air pollution or air pollutants. The literature search was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. We have included the human and animal studies corresponding to the search terms and published in English. We have excluded articles whose results did not concern fertility or gamete function and those focused on cancer or allergy. We have also excluded genetic, auto-immune or iatrogenic causes of reduced reproduction function from our analysis. Finally, we have excluded animal data that does not concern mammals and studies based on results from in vitro culture. Data have been grouped according to the studied pollutants in order to synthetize their impact on fertility and the molecular pathways involved.

CONCLUSION

Both animal and human epidemiological studies support the idea that air pollutants cause defects during gametogenesis leading to a drop in reproductive capacities in exposed populations. Air quality has an impact on overall health as well as on the reproductive function, so increased awareness of environmental protection issues is needed among the general public and the authorities.

Airway exposure to multi-walled carbon nanotubes disrupts the female reproductive cycle without affecting pregnancy outcomes in mice

BACKGROUND

The use of multiwalled carbon nanotubes (MWCNT) is increasing due to a growing use in a variety of products across several industries. Thus, occupational exposure is also of increasing concern, particularly since airway exposure to MWCNTs can induce sustained pulmonary acute phase response and inflammation in experimental animals, which may affect female reproduction. This proof-of-principle study therefore aimed to investigate if lung exposure by intratracheal instillation of the MWCNT NM-400 would affect the estrous cycle and reproductive function in female mice.

RESULTS

Estrous cycle regularity was investigated by comparing vaginal smears before and after exposure to 67 μg of NM-400, whereas reproductive function was analyzed by measuring time to delivery of litters after instillation of 2, 18 or 67 μg of NM-400. Compared to normal estrous cycling determined prior to exposure, exposure to MWCNT significantly prolonged the estrous cycle during which exposure took place, but significantly shortened the estrous cycle immediately after the exposed cycle. No consistent effects were seen on time to delivery of litter or other gestational or litter parameters, such as litter size, sex ratio, implantations and implantation loss.

CONCLUSION

Lung exposure to MWCNT interfered with estrous cycling. Effects caused by MWCNTs depended on the time of exposure: the estrous stage was particularly sensitive to exposure, as animals exposed during this stage showed a higher incidence of irregular cycling after exposure. Our data indicates that MWCNT exposure may interfere with events leading to ovulation.

The Associations Between Air Pollution and Adverse Pregnancy Outcomes in China

Research on the potential impact of air pollution on the human's health has increased rapidly in recent years. Several studies have suggested that exposure to air pollutants during period of pregnancy which is a crucial time point of mother-fetus development may have long-term and serious impact on adverse pregnancy outcomes. There is lack of review to evaluate the existed epidemiologic evidence on the associations between air pollutants and adverse pregnancy outcomes in China, so we conducted a review to explore the current epidemiological evidence on the effects of air pollutants to pregnancy outcomes and possible mechanisms during the pregnancy process. We used keywords to systematically search all the English and Chinese literatures on studies that were conducted in China. Exposure to air pollutants during pregnancy had shown there were harmful effects for different birth outcomes: preterm birth, low birth weight, stillbirth, birth defects, infertility, and macrosomia fetus. Results on the effects of air pollutants on adverse pregnancy outcomes are small and inconsistent because they vary in their design and methodology. The existed available evidence is compatible with either a small negative effect of air pollutants on pregnancy outcomes or with no effect; therefore, further studies are needed to confirm and quantify the possible associations and potential biologic mechanisms between air pollutants and pregnancy outcomes.

Influence of air quality on the results of in vitro fertilization attempts: A retrospective study

OBJECTIVE

To assess the influence of air quality on the results of IVF.

STUDY DESIGN

We performed a retrospective study on 292 patients who have undergone an IVF attempt from April 2012 to December 2015 in our French university hospital. Patients were included in the study if data on the air quality at home and at work were available and if they haven't been gone for more than 4days in a month. Data were recorded during the 3 months before oocyte collection and 1 month after embryo transfer. Air quality measurements were obtained from the Observatoire Régional de l'Air en Midi-Pyrénées (ORAMIP) and concerned the levels of nitrogen dioxide (NO₂), ozone (O₃), particulate matter PM10 and SO₂ measured every day.

RESULTS

Acute exposures to high levels NO₂ or PM10 were associated with lower results of IVF (ovarian response to stimulation, number of top embryos) while these parameters were enhanced when patients were exposed to high levels of O₃ during the first 2 months of folliculogenesis. These effects were found even for a short exposure (1day).

CONCLUSIONS

Air quality has an impact on global health and also on the reproductive function and public and authorities must be aware of environmental protection.

Outdoor air pollution and human infertility: a systematic review

Air pollution is a current research priority because of its adverse effects on human health, including on fertility. However, the mechanisms through which air pollution impairs fertility remain unclear. In this article, we perform a systematic review to evaluate currently available evidence on the impact of air pollution on fertility in humans. Several studies have assessed the impact of air pollutants on the general population, and have found reduced fertility rates and increased risk of miscarriage. In subfertile patients, women exposed to higher concentrations of air pollutants while undergoing IVF showed lower live birth rates and higher rates of miscarriage. After exposure to similar levels of air pollutants, comparable results have been found regardless of the mode of conception (IVF versus spontaneous conception), suggesting that infertile women are not more susceptible to the effects of pollutants than the general population. In addition, previous studies have not observed impaired embryo quality after exposure to air pollution, although evidence for this question is sparse.

Contributions of the Nurses' Health Studies to Reproductive Health Research

OBJECTIVES

To review the Nurses' Health Study's (NHS's) contribution to identifying risk factors and long-term health consequences of reproductive events.

METHODS

We performed a narrative review of the NHS I, NHS II, NHS3, and Growing Up Today Study (GUTS) publications between 1976 and 2016.

RESULTS

Collection of detailed reproductive history to identify breast cancer risk factors allowed the NHS to document an association between menstrual irregularities, a proxy for polycystic ovary syndrome (PCOS), and increased risk of diabetes and cardiovascular disease. The NHS II found that infertility associated with ovulation problems and gestational diabetes are largely preventable through diet and lifestyle modification. It also identified developmental and nutritional risk factors for pregnancy loss, endometriosis, and uterine leiomyomata. As women in NHS II age, it has become possible to address questions regarding long-term health consequences of pregnancy complications and benign gynecologic conditions on chronic disease risk. Furthermore, the NHS3 and GUTS are allowing new lines of research into human fertility, PCOS, and transgenerational effects of environmental exposures.

CONCLUSIONS

The multigenerational resources of the NHSs and GUTS, including linkages of related individuals across cohorts, can improve women's health from preconception through late adulthood and onto the next generation.