Exposure to ozone air pollution may make Black women more likely to develop fibroids.
Compared to women exposed to the lowest levels of the pollutant, Black women exposed to the highest levels had a 35% increased risk for developing the non-cancerous growths in and around their uterus. The link was even stronger among women younger than 35 and those who had given birth.
Exactly how, or even if, exposure to ozone pollution affects fibroid development is not fully understood.
“[But] we know that air pollution causes inflammation and an immune response, which are related to fibroids,” says study author Amelia Wesselink, an assistant professor at Boston University School of Public Health.
The study — published in the May issue of the journal Human Reproduction — adds to a small, but growing body of literature that hints at a link between air pollution and fibroids. It is the first to show such a link in Black women, who are known to be disproportionately affected by fibroids, Wesselink says.
Researchers looked at three air pollutants in 56 U.S. cities between 1997 and 2011 — particulate matter smaller than 2.5 microns (PM2.5), nitrogen dioxide (NO2) and ozone.
The study included almost 22,000 premenopausal Black women in these cities who were part of an ongoing health study. Women answered questionnaires every two years and were followed until 2019.
During the 14-year study period, close to 30% reported having a diagnosis of fibroids that was confirmed by ultrasound or surgery.
The risk of such self-reported fibroids increased with rising levels of ozone in the atmosphere, but this link was not seen with PM2.5 or NO2, the study showed.
The findings held even after researchers controlled for other factors that could affect the outcome, including other air pollutants, economic status, access to or quality of health care, and lifestyle factors related to fibroid risk.
“It is unclear why we did not see an association with the two other pollutants,” Wesselink says. “It could be that there is a mechanism unique to ozone that is yet to be uncovered.”
For example, ozone is related to the presence of sunlight as is vitamin D, and vitamin D deficiency may be driving this link. The study did not measure vitamin D exposure.
More research is needed to confirm the findings, Wesselink says.
“Ideally, we would screen an entire population to measure development of fibroids over time so that we aren’t relying on self-reported diagnosis,” she says. This would also catch women who have no symptoms.
Not all fibroids cause symptoms, but those that do may result in heavy or painful periods, stomach and back pain, constipation, the frequent need to urinate, and pain or discomfort during sex, according to Dr. Jennifer Wu, an obstetrician-gynecologist at Lenox Hill Hospital in New York City.
Family history, hormone levels and pregnancy are known to increase the odds of developing the growths.
“Fibroids grow in response to hormones and tend to shrink during menopause, when hormone levels drop,” says Wu, who was not involved in the research.
“Pollution may be a contributing factor to fibroid development in some women,” she says. The good news is that there are many treatments for fibroids that cause bothersome symptoms, including medication and minimally invasive procedures.
Dr. Marianthi Kioumourtzoglou, an assistant professor of environmental health sciences at Columbia Mailman School of Public Health in New York City, called this “a very important study.”
She said there has been little research into how environmental exposures affect this aspect of women’s health.
Air pollution has been linked to lung, heart and brain disease, mood disorders, and pregnancy and birth-related outcomes, says Kioumourtzoglou, who reviewed the new findings.
Besides moving, which is not feasible for most people, it can be hard to reduce exposure to ozone and other sources of air pollution, she pointed out.
“Masks definitely help,” she adds.
Learn more about the diagnosis and treatment of fibroids at the American College of Obstetricians and Gynecologists.
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