Ambient black carbon particles in human ovarian tissue and follicular fluid

In vivo gamete toxicology in the context of in vitro fertilization: a narrative review

IVF as a clinical method to surmount infertility has existed since the 1970s, and yet fertilization, embryo development, pregnancy, and live birth rates remain unacceptably low. Although a multitude of factors may contribute to stagnated success despite substantial advances in basic and applied IVF sciences, gamete quality is inarguably integral to IVF success rates. In this review, the authors will explore the role of environmental toxicology in impairing in vivo fertility and gamete quality prior to starting IVF that will influence downstream IVF success. In vivo contaminants of interest that may affect gamete potential in the context of IVF include heavy metals, per- and polyfluoroalkyl substances (PFAS), persistent organic pollutants (POPs), and airborne contaminants. By evaluating the current literature on reproductive toxicology and how toxic exposures may influence IVF, this review aims to provide a comprehensive reference of potential toxicological exposures for clinicians, to use in vitro and animal data to supplement correlative human studies with potential causative mechanisms, and to strengthen the case for patient assessment of toxicological risk.

Associations of long-term exposure to fine particulate matter and its components with ovarian aging: Evidence from a cross-sectional study in China

This study aimed to investigate associations between long-term exposure to PM2.5, or its constituents, and ovarian aging, assessed by age at natural menopause (ANM) and early menopause (EM) prevalence. A total of 15,345 postmenopausal women were recruited from an epidemiologic survey conducted across 12 provinces in China (2023-2024). Concentrations of air pollutants [PM2.5 mass, sulfate (SO42-), nitrate (NO3-), ammonium (NH4+), organic matter (OM), and black carbon (BC)] were obtained from the Tracking Air Pollution in China database. Multivariable regression models with random effects and quantile g-computation models were used to evaluate associations. Each interquartile range increase in 5-year average concentrations of PM2.5, SO42-, NO3-, NH4+, OM, or BC were correlated with significant changes of -0.79 (95 %CI: -0.87, -0.72), -0.98 (95 %CI: -1.06, -0.90), -0.54 (95 %CI: -0.63, -0.45), -0.90 (95 %CI: -0.98, -0.81), -0.83 (95 %CI: -0.91, -0.76), and -1.02 (95 %CI: -1.09, -0.96) in ANM, respectively. Joint exposure analysis revealed that the five combined PM2.5 constituents shared a negative association with ANM in which BC provided the largest weight. These pollutants were also significantly associated with elevated EM prevalence, wherein BC provided the strongest contribution. The associations were stronger in women with a history of smoking, other hazardous environmental exposure, and lower education level.

Fine particulate matter components and reproductive hormones in female adults: A 15-year longitudinal cohort study

BACKGROUND

Few cohort studies have evaluated the long-term impacts of ambient fine particulate matter (PM2.5) and its components on reproductive hormone levels in female adults.

METHODS

We conducted a 15-year retrospective cohort study in Taiwan between 2003 and 2017. The two-year average concentrations of PM2.5 and its components, including sulfate (SO42-), nitrate (NO3-), ammonium (NH4+), organic matter (OM), and black carbon (BC), were assessed at each participant's addresses. Linear mixed models were used to examine the associations of PM2.5 and its components with reproductive hormones, including follicle-stimulating hormone (FSH), luteinizing hormone (LH), testosterone (T), estradiol (E2), and prolactin (PRL). Stratified analyses were conducted to identify vulnerable populations.

RESULTS

17,152 female adults were included. Each interquartile range (IQR: 3.545 μg/m3) increase in PM2.5 was associated with a 0.585 mIU/mL [95% confidence interval (CI): 0.190-0.980] increase in FSH levels. Among the five components of PM2.5, BC had the strongest positive association [each IQR (0.272 μg/m3) increase was associated with a 0.863 mIU/mL (95% CI: 0.476-1.250) increase in FSH levels], followed by OM, SO42-, and NH4+. Similar associations were found for LH, with a 0.483 mIU/mL (95% CI: 0.225-0.742) and 0.684 mIU/mL (95% CI: 0.431-0.938) increase in LH levels per IQR increase in PM2.5 and BC, respectively. The pollutants were marginally associated with decreased E2 levels and increased PRL levels. Non-linear associations between PM2.5 and its components and the levels of FSH, LH, E2, and PRL were observed. These pollutants were also positively associated with T levels among young adults. Post-menopausal women were more susceptible to the chronic impacts of PM2.5 and its components.

CONCLUSION

Our study highlighted the adverse impacts of long-term exposure to PM2.5 components on hormonal homeostasis, revealing the biological mechanism of air pollution-reproductive health associations in females. Implementing stringent control of air pollution levels can benefit reproductive health in female adults, even in moderately polluted regions.

The effect of TiO2 nanoparticles on antral follicles is dependent on the nanoparticle internalization rate

Titanium dioxide nanoparticles (TiO2 NPs) are among the most widely produced metallic NPs due to commercial and industrial applications in products including food, cosmetics, paints, and plastics. TiO2 NPs are released into the environment posing health risks for humans and wildlife. Widespread uses have raised concerns about the potential toxicity of TiO2 NPs in reproduction. The ovary is an important endocrine organ responsible for sex steroid hormone production and folliculogenesis. NPs can reach the ovary, but limited information is available regarding NP toxicity and its effects on ovarian antral follicles. Thus, we tested the hypothesis that exposure to TiO2 NP affects sex hormone synthesis, oxidative stress, and antioxidant response in ovarian antral follicles in vitro. In addition, we characterized the NP internalization in the antral follicles over time to determine any association between NP internalization and effects on the antral follicle. Antral follicles were exposed to vehicle control or TiO2 NPs (5, 25, and 50 µg/ml) for 96 h. The lowest NP concentration (5 µg/ml) showed no internalization and no effects in antral follicles. The 25-µg/ml concentration had the highest internalization rate, leading to increased mRNA ratio of Bax to Bcl2. Interestingly, the highest concentration (50 µg/ml) showed lower internalization compared with the 25 µg/ml, with altered levels of steroidogenic involved genes and increased levels of progesterone and testosterone compared with control. In conclusion, these data suggest that TiO2 NP is internalized in antral follicles as the first step process in impairing follicle functions.

Association of specific PM2.5 chemical constituents and ozone exposure with pregnancy outcomes in women undergoing assisted reproductive technology treatment in central China

The associations of air pollutants exposure with assisted reproductive technology (ART) pregnancy outcomes are mixed, and the effects of specific components of fine particulate matter (PM2.5) and ozone (O3) are not well understood. We conducted a retrospective longitudinal study to explore the association of PM2.5 constituents and O3 exposure with three ART outcomes among women undergoing ART treatment. The exposure window was segmented into five periods corresponding to the cycle of ovarian stimulation and oocyte retrieval procedure. Generalized linear mixed model (GLMM) was applied to explore the relationships between PM2.5 constituents, O3, Normalized Vegetation Index (NDVI) exposure and three ART outcomes. The combined effect of PM2.5 constituents was evaluated by the quantile g (qg)-computation. We also explored the modifying effect of different covariate. Elevated exposure level of PM2.5 (OR = 0.915, 95% CI: 0.859, 0.974) and its constituents (BC: 0.905, 95% CI: 0.840, 0.975; OM: 0.910, 95% CI: 0.848, 0.976; NO3-: 0.909, 95% CI: 0.850, 0.972, SO42-: 0.905, 95% CI: 0.846, 0.968, and NH4+: 0.902, 95% CI: 0.842, 0.966) exposure throughout the year before oocyte retrieval (period 1) was correlated with a reduced odds ratio (OR) of live birth with statistical significance. Similarly, for each interquartile range (IQR) increase in O3 exposure during periods 2 (85 days prior to oocyte retrieval), 3 (30 days prior to oocyte retrieval), 4 (oocyte retrieval to embryo transfer) and 5 (embryo transfer to hCG test) was significantly related to a decreased OR of live birth. Especially, participants who underwent fresh embryo transfer cycles and received two cleavage-stage embryo transfer, and were younger than 30 years old, showed a higher susceptibility to particulate matter. Findings from this study suggest that PM2.5 constituents and O3 exposure may have adverse effects on the ART outcomes, highlighting the importance of identifying critical exposure periods for various air pollutants and the need for meticulous management of particulate matter.

Particulate air pollution at the time of oocyte retrieval is independently associated with reduced odds of live birth in subsequent frozen embryo transfers

STUDY QUESTION

Does exposure to particulate matter (PM) air pollution prior to oocyte retrieval or subsequent frozen embryo transfer (FET) affect the odds of live birth?

SUMMARY ANSWER

Live birth rates are lower when particulate matter (PM2.5 and PM10) levels are higher prior to oocyte retrieval, regardless of the conditions at the time of embryo transfer.

WHAT IS KNOWN ALREADY

Exposure to air pollution is associated with adverse reproductive outcomes, including reduced fecundity and ovarian reserve, and an increased risk of infertility and pregnancy loss. It is uncertain whether the effect on ART outcomes is due to the effects of pollution on oogenesis or on early pregnancy.

STUDY DESIGN, SIZE, DURATION

This retrospective cohort study included 3659 FETs in 1835 patients between January 2013 and December 2021, accounting for all FETs performed at a single clinic over the study period. The primary outcome was the live birth rate per FET. Outcome data were missing for two embryo transfers which were excluded. Daily levels of PM2.5, PM10, nitric oxide, nitrogen dioxide, sulphur dioxide, ozone and carbon monoxide were collected during the study period and calculated for the day of oocyte retrieval and the day of embryo transfer, and during the preceding 2-week, 4-week, and 3-month periods.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Clinical and embryological outcomes were analysed for their association with pollution over 24 hours, 2 weeks, 4 weeks, and 3 months, with adjustment for repeated cycles per participant, age at the time of oocyte retrieval, a quadratic age term, meteorological season, year, and co-exposure to air pollutants. Multi-pollutant models were constructed to adjust for co-exposures to other pollutants. Median concentrations in pollutant quartiles were modelled as continuous variables to test for overall linear trends; a Bonferroni correction was applied to maintain an overall alpha of 0.05 across the four exposure periods tested.

MAIN RESULTS AND THE ROLE OF CHANCE

Increased PM2.5 exposure in the 3 months prior to oocyte retrieval was associated with decreased odds of live birth (linear trend P = 0.011); the odds of live birth when PM2.5 concentrations were in the highest quartile were reduced by 34% (OR 0.66, 95% CI 0.47-0.92) when compared to the lowest quartile. A consistent direction of effect was seen across other exposure periods prior to oocyte retrieval, with an apparent dose-dependent relationship. Increased exposure to PM10 particulate matter in the 2 weeks prior to oocyte retrieval was associated with decreased odds of live birth (linear trend P = 0.009); the odds of live birth were decreased by 38% (OR 0.62, 95% CI 0.43-0.89, P = 0.010) when PM10 concentrations were in the highest quartile compared with the lowest quartile. Consistent trends were not seen across other exposure periods. None of the gaseous pollutants had consistent effects, prior to either oocyte retrieval or embryo transfer.

LIMITATIONS, REASONS FOR CAUTION

This was a retrospective cohort study, however, all FETs during the study period were included and data were missing for only two FETs. The results are based on city-level pollution exposures, and we were not able to adjust for all possible factors that may affect live birth rates. Results were not stratified based on specific patient populations, and it was not possible to calculate the cumulative live birth rate per commenced cycle.

WIDER IMPLICATIONS OF THE FINDINGS

This is the first study to specifically analyse FETs to separate the effects of environmental exposures prior to oocyte retrieval from those around the time of embryo transfer. Our findings suggest that increased PM exposure prior to oocyte retrieval is associated with reduced live birth rate following FET, independent of the conditions at the time of embryo transfer. Importantly, the air quality during the study period was excellent, suggesting that even 'acceptable' levels of air pollution have detrimental reproductive effects during gametogenesis. At the low pollution levels in our study, exposure to gaseous pollutants did not appear to affect live birth rates. This has important implications for our understanding of the effects of pollution on reproduction, and highlights the urgent need for effective policies limiting pollution exposure to protect human health and reproduction.

STUDY FUNDING/COMPETING INTEREST(S)

No funding was provided for this study. S.J.L. is supported by the Jean Murray Jones Scholarship from the Royal Australian and New Zealand College of Obstetricians and Gynaecologists, has received educational sponsorship from Besins, Ferring, Merck, and Organon, honoraria from Hologic and Organon, consulting fees from Merck unrelated to the current study, and is a member of the Reproductive Technology Council of Western Australia. S.J.L. and R.J.H. are board members of Menopause Alliance Australia. C.S.R., M.W., and E.N. have no conflicts of interest to declare. R.J.H. is the Medical Director of Fertility Specialists of Western Australia, the National Medical Director of City Fertility Australia, and a shareholder in CHA SMG. He chairs the Western Australian Minister's Expert Panel on ART and Surrogacy. R.J.H. has made presentations for and received honoraria from Merck, Merck-Serono, Origio, Igenomix, Gideon-Richter, and Ferring, and has received support for attending meetings from Merck, Organon, and Ferring.

TRIAL REGISTRATION NUMBER

N/A.

Particulate matter-induced oxidative stress - Mechanistic insights and antioxidant approaches reported in in vitro studies

Inhaled particulate matter (PM) is a key factor in millions of yearly air pollution-related deaths worldwide. The oxidative potential of PM indicates its ability to promote an oxidative environment. Excessive reactive oxygen species (ROS) can cause cell damage via oxidative stress, leading to inflammation, endoplasmic reticulum stress, airway remodeling, and various cell death modes (apoptosis, ferroptosis, pyroptosis). ROS can also interact with macromolecules, inducing DNA damage and epigenetic modifications, disrupting homeostasis. These effects have been studied extensively in vitro and confirmed in vivo. This review explores the oxidative potential of airborne particles and PM-induced ROS-mediated cellular damage observed in vitro, highlighting the link between oxidative stress, inflammation, and cell death modes described in the latest literature. The review also analyzes the effects of ROS on DNA damage, repair, carcinogenicity, and epigenetics. Additionally, the latest developments on the potential of antioxidants to prevent ROS's harmful effects are described, providing future perspectives on the topic.

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.

Association of Air Pollution with a Urinary Biomarker of Biological Aging and Effect Modification by Vitamin K in the FLEMENGHO Prospective Population Study

BACKGROUND

A recently developed urinary peptidomics biological aging clock can be used to study accelerated human aging. From 1990 to 2019, exposure to airborne particulate matter (PM) became the leading environmental risk factor worldwide.

OBJECTIVES

This study investigated whether air pollution exposure is associated with accelerated urinary peptidomic aging, independent of calendar age, and whether this association is modified by other risk factors.

METHODS

In a Flemish population, the urinary peptidomic profile (UPP) age (UPP-age) was derived from the urinary peptidomic profile measured by capillary electrophoresis coupled with mass spectrometry. UPP-age-R was calculated as the residual of the regression of UPP-age on chronological age, which reflects accelerated aging predicted by UPP-age, independent of chronological age. A high-resolution spatial-temporal interpolation method was used to assess each individual's exposure to PM 10 , PM 2.5 , black carbon (BC), and nitrogen dioxide (NO 2 ). Associations of UPP-age-R with these pollutants were investigated by mixed models, accounting for clustering by residential address and confounders. Effect modifiers of the associations between UPP-age-R and air pollutants that included 18 factors reflecting vascular function, renal function, insulin resistance, lipid metabolism, or inflammation were evaluated. Direct and indirect (via UPP-age-R) effects of air pollution on mortality were evaluated by multivariable-adjusted Cox models.

RESULTS

Among 660 participants (50.2% women; mean age: 50.7 y), higher exposure to PM 10 , PM 2.5 , BC, and NO 2 was associated with a higher UPP-age-R. Studying effect modifiers showed that higher plasma levels of desphospho-uncarboxylated matrix Gla protein (dpucMGP), signifying poorer vitamin K status, steepened the slopes of UPP-age-R on the air pollutants. In further analyses among participants with dpucMGP ≥ 4.26 μ g / L (median), an interquartile range (IQR) higher level in PM 10 , PM 2.5 , BC, and NO 2 was associated with a higher UPP-age-R of 2.03 [95% confidence interval (CI): 0.60, 3.46], 2.22 (95% CI: 0.71, 3.74), 2.00 (95% CI: 0.56, 3.43), and 2.09 (95% CI: 0.77, 3.41) y, respectively. UPP-age-R was an indirect mediator of the associations of mortality with the air pollutants [multivariable-adjusted hazard ratios from 1.094 (95% CI: 1.000, 1.196) to 1.110 (95% CI: 1.007, 1.224)] in participants with a high dpucMGP, whereas no direct associations were observed.

DISCUSSION

Ambient air pollution was associated with accelerated urinary peptidomics aging, and high vitamin K status showed a potential protective effect in this population. Current guidelines are insufficient to decrease the adverse health effects of airborne pollutants, including healthy aging trajectories. https://doi.org/10.1289/EHP13414.