Follow-up of the air pollution and the human male-to-female ratio analysis in Sao Paulo, Brazil: a times series study

Factors influencing sex ratio at birth in Krosno, Poland

The secondary sex ratio (SSR) is a widely used descriptor that reflects the living conditions and health status during pregnancy. The aim of study was to assess the impact of maternal factors, season of birth, and air pollution with the heating season on the sex ratio at birth in the Subcarpathian population from the Krosno district, Poland. A retrospective study involving 11,587 births was occurred at the John Paul II Podkarpackie Province Hospital in Krosno between 2016 and 2020. Sex of the newborn, the season of their birth, as well as the maternal age, birth order, the interval between births, and the season of birth were analysed. Furthermore, the relationship between the SSR and the level of air pollution during the heating season was investigated. To determine the significance of differences in sex ratios, chi-square analysis and multifactorial regression were used, with a significance level set at p < 0.05. At the chi-square level, all the studied factors indicated a statistically significant relationship with the SSR. However, the regression model used shows that maternal age and birth order were the most important factors in shaping the SSR in the study group.

Seasonal variation in air pollutant levels and its effects on the sex ratio at birth on Fukue island, Japan

BACKGROUND

In general, a slightly higher number of boys are born than girls, and the sex ratio at birth (number of male births/number of female births) is reported to be 1.03-1.07 in many countries. However, pregnant women exposed to high levels of atmospheric particulate matter have a reduced sex ratio at birth. Exposure to air pollutants can also lead to premature birth, suggesting that inflammation within the body may affect pregnancy maintenance and fetal development. On the other hand, the effects of air pollutants carried from afar by monsoons on the sex ratio at birth in downstream areas have not been evaluated. We focused on the Goto Islands, where various air pollutants flow from the Eurasian continent. The objective of this study was to clarify the effects of the atmospheric level of each pollutant on the sex ratio at birth on the Goto Islands.

METHODS

We extracted observation data of particulate matter 2.5, sulfur dioxide, oxidants, nonmethane hydrocarbons, and methane from the National Institute for Environmental Studies database. In addition, the monthly sex ratio at birth was calculated using birth data from the National Statistics Center. To evaluate the effect of substance exposure just before fertilization on the sex ratio at birth, we analyzed the relationship between the observed pollutant level and the sex ratio at birth 9 months later. A stepwise generalized linear model was used to analyze the effects of air pollutant levels on the sex ratio at birth.

RESULTS

The observed values for all pollutants were significantly different between seasons, including the particulate matter 2.5 (p < 0.0001), sulfur dioxide (p = 0.0026), oxidant (p < 0.0001), nonmethane hydrocarbon (p < 0.0001), and methane (p < 0.0001) values. In the target population in the target period, the total number of births was 1835, and the sex ratio at birth was 0.967. Univariate analysis showed that the values of particulate matter 2.5 (p = 0.0157) and oxidants (p = 0.0047) correlated negatively with the sex ratio at birth. In addition, the results of multivariate analysis using the stepwise method in the model equation indicated that every 1 ppm increase in the observed OX value resulted in a 0.311 decrease in the sex ratio at birth (p = 0.0034).

CONCLUSIONS

We evaluated the relationship between seasonal variations in air pollutant levels and the sex ratio at birth 9 months later on the Goto Islands. We found that an increase in oxidant levels just before and after conception may be a risk factor for a lower sex ratio at birth. Due to the previously reported vulnerability of male fetuses, females who become pregnant when air pollutant concentrations are high may be more likely to have a female baby. It is necessary to evaluate the effects of oxidants on various aspects of pregnancy and childbirth.

Air Pollution and Human Sperm Sex Ratio

The present study was designed to address the hypothesis that exposure to specific air pollutants may impact human sperm Y:X chromosome ratio. The study population consisted of 195 men who were attending an infertility clinic for diagnostic purposes and who had normal semen concentration of 15–300 mln/ml (WHO, 2010). Participants represented a subset of men in a multicenter parent study conducted in Poland to evaluate environmental factors and male fertility. Participants were interviewed and provided a semen sample. The Y:X ratio was assessed by fluorescent in situ hybridization (FISH). Air quality data were obtained from the AirBase database. In multivariate analysis the significant reduction was observed in the proportion of Y/X chromosome bearing sperm and exposure to particulate matter >10 μm in aerodynamic diameter PM₁₀ (p = .009) and particulate matter <10 μm in aerodynamic diameter PM_2.5 (p = .023). The observed effects of a lower Y:X sperm chromosome ratio among men exposed to air pollution support the evidence that the trend of declining sex ratio in several societies over past decades has been due to exposure to air pollution; however due to limited data on this issue, the obtained results should be confirmed in longitudinal studies.

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.

Effects of Fetal Exposure to Asian Sand Dust on Development and Reproduction in Male Offspring

In recent experimental studies, we reported the aggravating effects of Asian sand dust (ASD) on male reproduction in mice. However, the effects of fetal ASD exposure on male reproduction have not been investigated. The present study investigated the effects of fetal ASD exposure on reproduction in male offspring. Using pregnant CD-1 mice, ASD was administered intratracheally on days 7 and 14 of gestation, and the reproduction of male offspring was determined at 5, 10, and 15 weeks after birth. The secondary sex ratio was significantly lower in the fetal ASD-exposed mice than in the controls. Histologic examination showed partial vacuolation of seminiferous tubules in immature mice. Moreover, daily sperm production (DSP) was significantly less in the fetal ASD-exposed mice than in the controls. DSP in the fetal ASD-exposed mice was approximately 10% less than the controls at both 5 and 10 weeks. However, both the histologic changes and the DSP decrease were reversed as the mice matured. These findings suggest that ASD exposure affects both the fetal development and the reproduction of male offspring. In the future, it will be necessary to clarify the onset mechanisms of ASD-induced male fetus death and male reproductive disorders.

Inhalation of fine particulate matter during pregnancy increased IL-4 cytokine levels in the fetal portion of the placenta

This study aimed to verify the development of placental and systemic inflammation in rats exposed to fine particulate matter before or during pregnancy. Wistar rats were exposed to filtered air (control) or to a load of 600 μg/m(3) of fine particles in the air. The gene expression of IL-1β, IL-4, IL-6, IL-10, INF-γ, TNF-α and Toll-like receptor 4 in the placenta was evaluated. The serum and placental concentrations of IL-1β, IL-4, IL-6, IL-10, INF-γ and TNF-α were measured. The total and differential blood leukocyte and blood platelet count was assessed. Compared to control animals, IL-4 content was elevated in the fetal portion of the placenta in rats exposed to air pollution before and during pregnancy. Increased IL-4 suggests that a placental inflammatory reaction may have occurred in response to exposure to fine particulate matter and that this cytokine was responsible, among possibly others factors, for resolution of the inflammatory reaction.