‘Forever chemicals’ are known for lingering in the body. Menstruation helps expel them

April 22, 2024

This story is part of a series, “Fighting ‘Forever Chemicals’: Women face pervasive PFAS risks.”

Cancer-linked “forever chemicals” got their moniker because of how long they linger without breaking down — in the environment and the human body. Women appear to have a way of shedding at least some of the compounds, however.

“Some PFAS bind strongly to proteins in blood, and when women menstruate, they lose those blood proteins linked to PFAS,” Suzanne Fenton, who at the time was a group leader in the Mechanistic Toxicology Branch of the National Toxicology Program at the National Institutes of Health, told The Hill. 

“Therefore, this is a unique route of elimination,” added Fenton, who is now the director of North Carolina State University’s Center for Human Health and the Environment.

Forever chemicals or PFAS, which stands for per- and polyfluoroalkyl substances, are a group of toxic compounds that have been connected to numerous cancers and other illnesses. They are found in many common household items — including waterproof apparel, nonstick pans and cosmetics — and have become pervasive in the air, soil and water due to their use in manufacturing and in certain firefighting foams.

The vast majority of Americans have at least some PFAS in their bloodstream. A widely cited study published in 2015 from the Centers for Disease Control and Prevention found that 97 percent of Americans have these substances in their blood. 

PFAS tend to bind to proteins like albumin in the blood, according to Erin P. Hines, a researcher in the Environmental Protection Agency’s reproductive toxicology division. But with menstruation and childbirth, she explained, come blood loss. Thanks to their monthly cycle, menstruating adults “typically have a lower body burden” or lower blood concentration of PFAS than non-menstruating peers who live in the same type of community and have a similar socioeconomic status, Hines noted. 

A 2022 epidemiological review of studies on the issue also said that “associations have been observed between heavy menstrual bleeding and lower PFAS concentrations.” 

Marianthi-Anna ​Kioumourtzoglou, one of the review authors, said the findings show that, at least in theory, some people should be able to “reduce their total body PFAS burden once a month just by menstruating.”

A January 2022 Toxicology review published by Fenton’s research team, notes that “menstruation appears to be a crucial route of elimination for many PFAS” and potentially explains up to 30 percent of the discrepancy between male and female PFAS blood levels. 

“Since 90–99 percent of PFAS in the blood are bound to serum albumin, menstrual bleeding may prove an important elimination pathway for these persistent substances,” the authors stated. 

The authors also cited previous research indicating that PFAS blood concentrations decreased in women who had recently menstruated, relative to individuals who did not experience any such bleeding. Yet another study showed how women who had already undergone menopause — the life stage when menstrual periods cease — had heightened blood levels of four different types of PFAS, in comparison to those who had not yet entered this phase. 

Nonetheless, Fenton stressed that “because some PFAS accumulate in tissues, this route is unlikely to rid the body of PFAS.”

The impacts of this potential elimination route may also be limited because people are “consistently and constantly exposed” to PFAS, according to ​Kioumourtzoglou, an assistant professor in environmental health sciences at Columbia University.

Menstruation’s effectiveness in shedding PFAS is also restricted when periods stop, perhaps as a result of menopause or taking certain hormonal contraceptives.

“I think it would be safe to say that a woman who is on an oral contraceptive or an IUD where they’re not menstruating would potentially have a higher concentration of the PFAS because they’re not menstruating and getting rid of that volume of blood and protein each month,” Hines said. 

“Similarly, if you regularly donate blood you can get rid of some of your body burden of the environmental chemicals like the PFAS,” she added.

​Kioumourtzoglou noted that it is important to get a greater understanding of this issue because it could inform health care decisions made by doctors and patients. 

“Once we understand this dynamic, if this is an important excretion route then maybe … for some people, we could recommend to go off birth control,” she said. “That could potentially be a recommendation for a certain subset of the population that’s heavily exposed to PFAS and at the same time not in absolute need for birth control, or maybe they can look at different ways of birth control that don’t necessarily reduce blood flow.”

But the ability to shed some PFAS through menstruation may be a curse in addition to a blessing — at least when it comes to scientists’ efforts to understand the dangers of PFAS. Kioumourtzoglou’s review notes that because of the substances being excreted in this way, scientists could end up underestimating just how much PFAS people with heavy menstrual bleeding are actually exposed to.

“Information on menstrual bleeding may be critical for addressing measurement error to prevent the underestimation of the health impact of PFAS,” the review states.