Air pollution affects sex ratio. Research has long shown that environmental pollution may contribute to an imbalanced sex ratio at birth. Pollution usually leads to an increase in the birth rate of male babies. However, a recent study by Brazilian researchers reached largely the same but slightly different conclusions about the impact of air pollution on sex ratio at birth. Does air pollution cause more female births and fewer male births? Will air pollution affect fetal development?
Scientists have long explored the various factors that influence the sex ratio of newborns. In this complex topic, studies in recent years have pointed out that environmental pollution may be a variable that cannot be ignored. 
A research team led by Professor Jorge Halac of the University of São Paulo in Brazil conducted a striking study. They analyzed air quality data and birth records in São Paulo between 2001 and 2003. Studies have found that in areas with heavy air pollution, the sex ratio of newborns tends to be female, that is, the birth rate of female babies is relatively high.
Professor Hallak explained that their findings may be due to the negative impact of contamination on male embryos more than on female embryos. This phenomenon is not uncommon in nature; for example, in some animal populations, more females appear when environmental pressure increases.
The study is not without controversy, however. Some scientists believe that although the study results are statistically significant, limitations of the sample size and scope of the study make its conclusions need to be verified by further research. In addition, changes in sex ratio may be affected by many other factors, including socioeconomic structure, cultural practices, and even climate change.
Nevertheless, Professor Hallak\’s research does provide us with a new perspective on the profound impact that environmental pollution may have on human reproductive health. Globally, accelerated urbanization and increased industrial activities have led to increased air pollution, which is not only an environmental problem but also a public health issue.
Therefore, regardless of the conclusions of the study, we should take active measures to reduce air pollution and protect our environment. This is not only for ourselves, but also for our future generations, ensuring that heWe can grow on a healthy and sustainable planet. At the same time, continued scientific research is necessary to help us better understand the possible effects of environmental changes on various aspects of human life, including sex ratios.
