Some air pollutants can disrupt hormone levels during the menopause transition, possibly exacerbating symptoms, according to a paper published earlier this year in the journal Science of Total Environment. 

University of Michigan researchers analyzed the sex hormones of 1,365 middle-aged women and the air quality around their homes to understand how certain air pollutants affected their hormones. They found that exposure to two types of air pollutants, nitrogen dioxide and the fine particulate matter known as PM2.5, was associated with an additional decrease in estrogen levels and a more accelerated estrogen decline during menopause transition.

“Menopause is an important predictor of future chronic disease,” said Sung Kyun Park, an associate professor of epidemiology at the University of Michigan and an author of the study. “The management of menopause is really important to the woman’s health later in life. If air pollution plays a role, we need to take care of that.”

While there is a “growing understanding” of air pollution’s importance for reproductive health, most air pollution research has been done on women of reproductive age, said Amelia Wesselink, a research assistant professor of epidemiology at Boston University who was not involved in the study. 

“What’s really unique about this study is that they have repeated measures of reproductive hormones before, during and after the menopausal transition,” Wesselink said. “All of the symptoms that we associate with menopause are really resulting from these dramatic changes in hormone levels.”

During menopause, a person’s menstrual cycle starts to change until it eventually stops. When ovulation stops, ovaries also stop making estrogen, the sex hormone responsible for regulating the female reproductive system. This estrogen decrease has health implications that go beyond a woman’s reproductive life; it has been linked to an increase in the risk of cardiovascular disease, bone health problems and Alzheimer’s disease. 

While this particular field of research is relatively new, the findings aren’t as surprising, said Audrey Gaskins, an associate professor of epidemiology and environmental health at Emory University’s Rollins School of Public Health. Since 2022, researchers have known that, in mice, air pollution causes inflammation in the ovaries and also causes ovarian follicles—little fluid-filled sacs that contain an egg—to die early. In a study released in September 2023, researchers found black carbon particles in the ovarian tissue and the follicular fluid—the liquid that surrounds eggs—of all the women in their sample. 

If air pollution affects women’s ovaries for many years, it would make sense that they may experience menopause at an earlier age or have lower levels of certain hormones, Gaskins said. 

Researchers only looked at hormone levels of individuals going through menopause, and still have to figure out how these hormonal changes will affect menopause symptoms. Scientists already know, though, that low estrogen is linked to menopause symptoms such as hot flashes and sleep disorders. 

“The question just becomes the magnitude of the effect that we are seeing,” said Gaskins. 

That will be the next step of the research, Park said.