While "forever chemicals" have been linked to numerous adverse health effects, from cancer to kidney disease, they can also have different effects on the bodies of men and women.
"Very often you see something in one sex and not in the other sex," says Linda Birnbaum, former head of the National Institute of Environmental Health Sciences and the National Toxicology Program.
'Forever chemicals' or PFAS can be found in many common household products and certain types of firefighting foam. Their use in manufacturing has led to their spread in the air, water and soil, and it is estimated that they are in the blood of approximately 97 percent of Americans. The federal government recently established the first national limits for some types of these substances in drinking water.
Some of the different ways in which the widespread chemicals affect men and women are clearly related to reproductive organs.
Exposure to PFAS has been linked to an increased risk of testicular cancer, for example: A panel of scientists determined in 2012 that there is a "probable link" between exposure to a type of PFAS called PFOA and testicular cancer.
A January 2022 toxicology study examined several issues related to the female reproductive system - such as birth defects, fertility and changes in the menstrual cycle - that could be linked to PFAS exposure. "The effects are numerous," the authors found, although they said it is not yet clear exactly how the compounds target the female endocrine and reproductive systems due to "a large research gap."
A study published in September sought to narrow that gap by zeroing in on sex-specific relationships between three classes of likely endocrine disruptors - including PFAS - and previous diagnoses of hormone-related cancers. The scientists observed particularly striking evidence of these differences with regard to melanoma: higher blood levels of PFAS were linked to earlier diagnoses in women, but not in men.
"Sex-specific associations between PFAS chemicals and previous melanoma diagnoses suggest that sex-mediated mechanisms may play a role," wrote the authors, from the University of Southern California and the University of Michigan.
Although the precise mechanism behind the melanoma connection is still uncertain, the scientists suspected that because these tumor cells have estrogen receptors, environmental contaminants that mimic estrogenic activity - such as PFAS, possibly - could fuel cancer growth in women.
As with melanoma, other health consequences, not as clearly linked to gender-specific characteristics, may still affect men and women differently after exposure to environmental pollutants, such as PFAS.
High blood pressure, for example, appears to be more pronounced in women than in men, according to recent studies.
Sometimes this manifests as pregnancy-induced hypertension, which can lead to a potentially fatal condition called preeclampsia - a potential effect of PFAS exposure that Erin P. Hines, a researcher in the Environmental Protection Agency's division of reproductive toxicology , says she would like to see more. research.
"Having preeclampsia or having pregnancy-induced hypertension during pregnancy can change a woman's health outcomes for the rest of her life, putting her at greater risk for adverse cardiovascular outcomes such as stroke," Hines said, adding he noted that this risk is independent of PFAS exposure.
"But if you have a pregnancy where you have preeclampsia or one of these hypertensive disorders of pregnancy, there are increased risks of morbidity and mortality throughout your life. [with] cardiovascular events," she added.
In addition to the pregnancy-induced type, additional research has also identified hypertension in the PFAS-exposed female population in general.
A 2022 study from the American Heart Association found that middle-aged women with higher blood levels of certain types of PFAS had a greater risk of hypertension. Analyzing the annual follow-up visits of 1,058 middle-aged women who were initially free of hypertension between 1999 and 2017, the scientists found that 470 individuals developed the condition. The authors found that women aged 45 to 56 with high levels of PFOS in their blood had a 42 percent higher risk of developing high blood pressure, while women with high levels of PFOA had a 47 percent higher risk. Women with high levels of all seven types of PFAS examined in the study had a 71 percent increased risk of developing high blood pressure.
Study author Ning Ding said exposure to PFAS also appears to put women at particularly high risk in a broader way.
"Women appear to be particularly vulnerable when exposed to these chemicals," Ding, a postdoctoral researcher at the University of Michigan's department of epidemiology, said in a statement. "Exposure may be an underappreciated risk factor for cardiovascular disease risk in women."
Studies are also emerging suggesting links between PFAS and other health outcomes in girls or women, such as ADHD in girls or weight gain in women. Scientists have also linked exposure to PFAS to an increased susceptibility to developing diabetes in middle-aged women. Some types of PFAS could disrupt the regulatory behavior of certain protein molecules and in turn increase the risk of diabetes within this cohort, the April 2022 study said.
Although the researchers emphasized that there is no evidence of a gender-dependent link between PFAS and diabetes in humans, they pointed to another recent study that found that female mice's metabolic responses to PFOA exposure were greater than those of male mice.
Meanwhile, another impact of PFAS has been shown to mainly affect boys. A 2022 study found that teenage boys exposed to a mixture of the substances and another type of hormone-disrupting chemicals known as phthalates may have lower bone density, making the bones weaker and more prone to fractures.
Some vulnerabilities associated with PFAS can take root in the womb. Prenatal exposure to the substances has been linked to premature birth, changes in birth weight or congenital problems that manifest later in childhood - including ADHD or IQ effects, Birnbaum said.
"We see with PFAS - as with many chemicals that actually disrupt endocrine systems - that you get a boy or girl difference," she said, noting that some effects occur in only one gender.
"For example, if you look at baby boys and baby girls together, you might not see an effect. But when you separate the sexes, suddenly you see an effect in one of them," Birnbaum added.
But she also acknowledged that not all researchers are open to that kind of separation: "What's interesting to me is that there are people who don't want to believe that. They think: if you don't see it in both men and women, it can't happen."
According to Birnbaum, the discovery of sex-dependent health consequences often depends on what exactly scientists are looking for in their research.
"It's a bit of the old story: if you don't look, you don't see. But when you start looking, you start finding."
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