Air pollutants and impairments of male reproductive health-an overview

Implications of Exposure to Air Pollution on Male Reproduction: The Role of Oxidative Stress

Air pollution, either from indoor (household) or outdoor (ambient) sources, occurs when there is presence of respirable particles in the form of chemical, physical, or biological agents that modify the natural features of the atmosphere or environment. Today, almost 2.4 billion people are exposed to hazardous levels of indoor pollution, while 99% of the global population breathes air pollutants that exceed the World Health Organization guideline limits. It is not surprising that air pollution is the world's leading environmental cause of diseases and contributes greatly to the global burden of diseases. Upon entry, air pollutants can cause an increase in reactive oxygen species (ROS) production by undergoing oxidation to generate quinones, which further act as oxidizing agents to yield more ROS. Excessive production of ROS can cause oxidative stress, induce lipid peroxidation, enhance the binding of polycyclic aromatic hydrocarbons (PAHs) to their receptors, or bind to PAH to cause DNA strand breaks. The continuous and prolonged exposure to air pollutants is associated with the development or exacerbation of pathologies such as acute or chronic respiratory and cardiovascular diseases, neurodegenerative and skin diseases, and even reduced fertility potential. Males and females contribute to infertility equally, and exposure to air pollutants can negatively affect reproduction. In this review, emphasis will be placed on the implications of exposure to air pollutants on male fertility potential, bringing to light its effects on semen parameters (basic and advanced) and male sexual health. This study will also touch on the clinical implications of air pollution on male reproduction while highlighting the role of oxidative stress.

Exposure to particulate matter may affect semen quality via trace metals: Evidence from a retrospective cohort study on fertile males

Particulate matter (PM) exposure may be associated with male semen quality. Besides, PM exposure induces up and down levels of trace metals in tissues or organs. The levels of trace metals in semen are critical for adverse male semen quality. This study aims to evaluate the concentrations of seminal-level trace metals in fertile men and assess its associations with PM exposure and to explore the mediation role of trace metals in seminal plasma plays in the relationship between PM exposure and semen quality. Total 1225 fertile men who participated in a cohort study from 2014 to 2016 were finally recruited. Multivariate linear regression was applied to explore associations between each two of PM exposure, trace metals and semen parameters. 1-year PM2.5 and PM10 exposure levels were positively associated with arsenic (As), mercury (Hg), lanthanum (La), praseodymium (Pr), neodymium (Nd) but negatively associated with vanadium (V), magnesium (Mg), strontium (Sr), barium (Ba) in semen. It was also found that most of the elements were associated with total sperm number, followed by sperm concentration. Redundancy analysis (RDA) also determined several strong positive correlations or negative correlations between 1-year PM exposure and trace metals. Mediation analysis found that trace metals had a potentially compensatory or synergetic indirect effect on the total effect of the association between 1-year PM exposure and semen quality. The retrospective cohort study provides long-term PM exposure that may cause abnormal semen quality by affecting seminal plasma element levels.

The impact of air pollution and endocrine disruptors on reproduction and assisted reproduction

PURPOSE OF REVIEW

Rapid increase in world population accompanied by global industrialization has led to an increase in deployment of natural resources, resulting in growing levels of pollution. Here, we review recent literature on the impact of environmental pollution on human reproductive health and assisted reproduction outcomes, focusing on two of the most common: air pollution and endocrine disruptors.

RECENT FINDINGS

Air pollution has been associated with diminished ovarian reserve, uterine leiomyoma, decreased sperm concentration and motility. Air pollution also correlates with decreased pregnancy rates in patients undergoing infertility treatment using in-vitro fertilization (IVF). Similarly, Bisphenol A (BPA), a well studied endocrine disrupting chemical, with oestrogen-like activity, is associated with diminished ovarian reserve, and abnormal semen parameters, while clinical implications for patients undergoing infertility treatment remain to be established.

SUMMARY

There is convincing evidence that environmental pollutants may have a negative impact on human health and reproductive potential. Air pollutions and endocrine disrupting chemicals found in water and food seem to affect male and female reproductive function. Large-scale studies are needed to determine the threshold values for health impact that may drive targeted policies.

Do cats mirror their owner? Paired exposure assessment using silicone bands to measure residential PAH exposure

It has been suggested that domestic animals can serve as sentinels for human exposures. In this study our objectives were to demonstrate that i) silicone collars can be used to measure environmental exposures of (domestic) animals, and that ii) domestic animals can be used as sentinels for human residential exposure. For this, we simultaneously measured polycyclic aromatic hydrocarbons (PAHs) using silicone bands worn by 30 pet cats (collar) and their owner (wristband). Collars and wristbands were worn for 7 days and analyzed via targeted Gas Chromatography-Mass Spectrometry (GC-MS). Demographics and daily routines were collected for humans and cats. Out of 16 PAHs, 9 were frequently detected (>50% of samples) in both wristbands and collars, of which Phenanthrene and Fluorene were detected in all samples. Concentrations of wristbands and collars were moderately correlated for these 9 PAHs (Median Spearman's r = 0.51 (range 0.16-0.68)). Determinants of PAH concentrations of cats and humans showed considerable overlap, with vacuum cleaning resulting in higher exposures and frequent changing of bed sheets in lower exposures. This study adds proof-of-principle data for the use of silicone collars to measure (domestic) animal exposure and shows that cats can be used as sentinels for human residential exposure.

Exposure to ambient particulate matter affects semen quality: A case study in Wenzhou, China

BACKGROUND

Particulate matter (PM), including PM_2.5 (PM ≤ 2.5 µm in aerodynamic diameter) and PM₁₀ (PM ≤ 10 µm in aerodynamic diameter), is a component of air pollutants, which is linked to semen quality. However, the available evidence of association needs to be strengthened, and some studies have conflicting results.

OBJECTIVES

To evaluate the potential impacts of PM on semen quality during the full (0-90 days before semen examination) and three key sperm development windows (0-9, 10-14, and 70-90 days before semen examination).

METHODS

We included 1494 infertile men in the main urban area in Wenzhou, China, who had undergone semen examinations for fertility between 2014 and 2019. The impacts were assessed by multivariable linear regression models.

RESULTS

Overall, during the full sperm development window, PM_2.5 and PM₁₀ exposures were associated with declined progressive sperm motility (%) (β: -0.6; 95% confidence intervals (CIs): -1.07, -0.13 and -0.46; -0.59, -0.33) and total sperm motility (%) (-1.95; -2.67, -1.23 and -1.32; -1.82, -0.82), and associated with increased sperm concentration (10⁶ /ml) (0.02; 0.006, 0.023 and 0.007; 0.001, 0.013) and total sperm number (10⁶ ) (0.02; 0.01, 0.03 and 0.011; 0.004, 0.017). Furthermore, only PM_2.5 exposure during the 10-14 days window was significantly associated with declined progressive motility (%) (-0.207; -0.395, -0.023).

CONCLUSIONS

During the full sperm development window, PM exposure has an adverse impact on sperm motility and positive impacts on sperm concentration and total sperm number. The adverse impact was more severe in the 10-14 days window.

The Association Between Self-Reported Household Renovation and Semen Parameters Among Infertile Men: A Cross-Sectional Study

Previous studies have indicated that outdoor air pollution has a negative impact on semen quality; however, few studies have examined whether living in a recently renovated residence is one of the factors influencing semen parameters. We aimed to examine the association between household renovation and semen parameters among infertile men. Our study was conducted at the Reproductive Medicine Center, The First Hospital of Jilin University (Changchun, China) from July 2018 to April 2020. A total of 2267 participants were enrolled in the study. The participants completed the questionnaire and provided a semen sample. Univariate and multiple logistic regression models were used to estimate the association between household renovations and semen parameters. Of the participants, about one-fifth (n = 523, 23.1%) had undergone renovations in the last 24 months. The median progressive motility was 34.50%. There was a significant difference between participants whose residences had been renovated in the last 24 months and those whose residences had not been recently renovated (z = -2.114, p = .035). Compared with participants whose residences were not recently renovated, participants who moved into the residence within 3 months after renovation had a higher risk of abnormal progressive motility after adjusting for age and abstinence time (odds ratio [OR] = 1.537, 95% confidence interval [CI]: 1.088-2.172). Our findings indicated that progressive motility was significantly associated with household renovations.

Effects of Ambient Air Pollution on Precocious Puberty: A Case-Crossover Analysis in Nanjing, China

BACKGROUND

Ambient air pollution is closely related to a variety of health outcomes. Few studies have focused on the correlations between air pollution exposure and children's sexual development. In this study, we investigated the potential effects of exposure to air pollution on precocious puberty among children using real-world evidence.

METHODS

We conducted a case-crossover study (n = 2201) to investigate the effect of ambient air pollution exposure on precocious puberty from January 2016 to December 2021. Average exposure levels of PM2.5, PM10, SO2, NO2, CO, and O3 before diagnosis were calculated by using the inverse distance weighting (IDW) method. Distributed lag nonlinear model (DLNM) was used to assess the effect of air pollutants exposure on precocious puberty.

RESULTS

The mean age of the children who were diagnosed with precocious puberty was 7.47 ± 1.24 years. The average concentration of PM2.5 and PM10 were 38.81 ± 26.36 μg/m3 and 69.77 ± 41.07 μg/m3, respectively. We found that exposure to high concentrations of PM2.5 and PM10 might increase the risk of precocious puberty using the DLNM model adjusted for the age, SO2, NO2, CO, and O3 levels. The strongest effects of the PM2.5 and PM10 on precocious puberty were observed in lag 27 (OR = 1.72, 95% CI: 1.01-2.92) and lag 16 (OR = 1.95, 95% CI: 1.33-2.85), respectively.

CONCLUSION

Our findings supported that short-term exposure to air pollution was the risk factor for precocious puberty. Every effort should be made to protect children from air pollution.

Monocyte exposure to fine particulate matter results in miRNA release: A link between air pollution and potential clinical complication

Chronic exposure to PM_2.5 contributes to the pathogenesis of numerous disorders, although the underlying mechanisms remain unknown. The study investigated whether exposure of human monocytes to PM_2.5 is associated with alterations in miRNAs. Monocytes were exposed in vitro to PM_2.5 collected during winter and summer, followed by miRNA isolation from monocytes. Additionally, in 140 persons chronically exposed to air pollution, some miRNA patterns were isolated from serum seasonally. Between-season differences in chemical PM_2.5 composition were observed. Some miRNAs were expressed both in monocytes and in human serum. MiR-34c-5p and miR-223-5p expression was more pronounced in winter. Bioinformatics analyses showed that selected miRNAs were involved in the regulation of several pathways. The expression of the same miRNA species in monocytes and serum suggests that these cells are involved in the production of miRNAs implicated in the development of disorders mediated by inflammation, oxidative stress, proliferation, and apoptosis after exposure to PM_2.5.

Short total sleep duration and poor sleep quality might be associated with asthenozoospermia risk: A case-control study

Sleep has been related to a variety of health outcomes. However, no association between sleep and asthenozoospermia has been reported. The aim of this study is to first investigate the relationship between sleep status and asthenozoospermia risk. A case-control study, including 540 asthenozoospermia cases and 579 controls, was performed from June 2020 to December 2020 in the infertility clinic from Shengjing Hospital of China Medical University. Data on sleep status were collected by Pittsburgh sleep quality index questionnaires and asthenozoospermia was diagnosed based on the World Health Organization guidelines. Odds ratio (OR) with 95% confidence interval (95% CI) was calculated by logistic regression analysis to assess the aforementioned association. Results of this study demonstrated that compared with total sleep duration of 8–9 h/day, < 8 h/day was related to asthenozoospermia risk (OR: 1.44, 95% CI: 1.05–1.99); compared to good sleep quality, poor sleep quality was associated with asthenozoospermia risk (OR: 1.35; 95% CI: 1.04–1.77). There were multiplicative model interaction effects between sleep quality and tea drinking (p = 0.04), rotating night shift work (p < 0.01) on asthenozoospermia risk. However, we failed to detect any associations between night sleep duration, daytime napping duration, night bedtime, wake-up time, sleep pattern and asthenozoospermia risk. In conclusion, short total sleep duration and poor sleep quality might be related to asthenozoospermia risk. Further well-designed prospective studies are warranted to confirm our findings.

Inverse association between ambient particulate matter and semen quality in Central China: Evidence from a prospective cohort study of 15,112 participants

Emerging evidence indicates that ambient particulate matter (PM) is harmful to male fertility, but the associations between ambient PM exposure and semen quality were inconsistent. This study aimed to quantitatively evaluate the association between ambient PM exposure and semen quality based on a large prospective cohort. Using data from the prospective assisted reproduction cohort in Anhui province, China, we included 15,112 males with 28,267 semen tests, whose partner has undergone assisted reproductive technology from September 1, 2015 to September, 22 2020. Individual ambient PM, gaseous air pollutants, and temperature exposures of the participants during 0-90, 0-9, 10-14, and 70-90 days before semen quality tests were evaluated using inverse distance weighting interpolation. Linear mixed-effects models were conducted to evaluate the relationship between PM_2.5 and PM₁₀ exposures and standardized semen quality parameters. Models were adjusted for age, body mass index, smoking, drinking, education attainment, occupation type, sampling month, temperature and the principal component of gaseous air pollutants. PM_2.5 and PM₁₀ were inversely associated with sperm concentration, total sperm count, total motility, progressive motility, total motile sperm count, and progressively motile sperm count during 0-90, 0-9, and 70-90 days period (all p < 0.05), but not 10-14 days period. The regression coefficients of PM_2.5 exposure on semen quality parameters during 0-90 days period were larger than 0-9 and 70-90 days periods, and the effects of PM_2.5 on semen quality parameters were stronger than PM₁₀. Our results showed that ambient PM_2.5 and PM₁₀ exposures were associated with semen quality, during 70-90 days and 0-9 days before sampling, and the entire spermatogenesis process. The effects of PM_2.5 on semen quality parameters were stronger than PM₁₀, and the long-term effects of PM_2.5 and PM₁₀, throughout spermatogenesis, were stronger than the short-term effects.

Climate change and global health: A call to more research and more action

There is increasing understanding, globally, that climate change and increased pollution will have a profound and mostly harmful effect on human health. This review brings together international experts to describe both the direct (such as heat waves) and indirect (such as vector-borne disease incidence) health impacts of climate change. These impacts vary depending on vulnerability (i.e., existing diseases) and the international, economic, political, and environmental context. This unique review also expands on these issues to address a third category of potential longer-term impacts on global health: famine, population dislocation, and environmental justice and education. This scholarly resource explores these issues fully, linking them to global health in urban and rural settings in developed and developing countries. The review finishes with a practical discussion of action that health professionals around the world in our field can yet take.

Mediterranean Diet as a Shield against Male Infertility and Cancer Risk Induced by Environmental Pollutants: A Focus on Flavonoids

The role of environmental factors in influencing health status is well documented. Heavy metals, polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls, dioxins, pesticides, ultrafine particles, produced by human activities put a strain on the body’s entire defense system. Therefore, together with public health measures, evidence-based individual resilience measures are necessary to mitigate cancer risk under environmental stress and to prevent reproductive dysfunction and non-communicable diseases; this is especially relevant for workers occupationally exposed to pollutants and/or populations residing in highly polluted areas. The Mediterranean diet is characterized by a high intake of fruits and vegetables rich in flavonoids, that can promote the elimination of pollutants in tissues and fluids and/or mitigate their effects through different mechanisms. In this review, we collected evidence from pre-clinical and clinical studies showing that the impairment of male fertility and gonadal development, as well as cancers of reproductive system, due to the exposure of organic and inorganic pollutants, may be counteracted by flavonoids.