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

Publisher: BioMed Central Country of Publication: England NLM ID: 100968562 Publication Model: Electronic Cited Medium: Internet ISSN: 1471-2458 (Electronic) Linking ISSN: 14712458 NLM ISO Abbreviation: BMC Public Health Subsets: MEDLINE

Original Publication: London : BioMed Central, [2001-

Air Pollutants*/adverse effects ; Air Pollutants*/analysis ; Air Pollution*/adverse effects ; Air Pollution*/analysis; Infant, Newborn ; Female ; Male ; Humans ; Pregnancy ; Seasons ; Sulfur Dioxide/analysis ; Japan/epidemiology ; Sex Ratio ; Particulate Matter/adverse effects ; Particulate Matter/analysis ; Oxidants ; Methane/analysis

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.
(© 2023. The Author(s).)

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21K21115 Japan Society for the Promotion of Science

Keywords: Air Pollutant; Island; Japan; Oxidant; Sex ratio at birth

0 (Air Pollutants)
0UZA3422Q4 (Sulfur Dioxide)
0 (Particulate Matter)
0 (Oxidants)
OP0UW79H66 (Methane)

Date Created: 20231212 Date Completed: 20231216 Latest Revision: 20240117

20250114

PMC10714618

10.1186/s12889-023-17418-5

38082405