When a reporter with the Sierra Club magazine asked Graham Peaslee, a physicist at the University of Notre Dame, to test several different samples of unused menstrual underwear for per- and polyfluoroalkyl substances (PFAS) in 2019, the results fueled concern over chemical exposure in feminine hygiene products — which ultimately ended up in a $5 million lawsuit against the period and incontinence underwear brand Thinx.

Then in 2023, the New York Times asked Peaslee to test 44 additional period and incontinence products for PFAS, a class of toxic fluorinated compounds inherently repellent to oil, water, soil and stains, and known as “forever chemicals” for their exceptionally strong chemical and thermal stability. Measurable PFAS were found in some layers of many of the products tested — some low enough to suggest the chemicals may have transferred off packaging materials, while others contained higher concentrations, suggesting the chemicals were intentionally used during the manufacturing process.

In the meantime, another group of researchers published a study that found PFAS in single-use period products, leading Peaslee and his lab to widen their investigation into all sorts of reusable feminine hygiene products — often viewed as an eco-friendly option by consumers. Now, the results of that study have been published in Environmental Science & Technology Letters.

Most of the samples tested in Peaslee’s latest study (71.2 percent) contained PFAS concentrations low enough to be characterized by Peaslee and his co-authors as “non-intentionally fluorinated.” But period underwear (33 percent) and reusable pads (25 percent) had the greatest rates of “intentional fluorination.”

“The reusable menstrual product market is a rapidly growing market, which relies heavily on the idea that these products are environmentally conscious because of the significant reduction in the use of paper and plastic products,” said Peaslee, professor emeritus in the Department of Physics and Astronomy. “To the extent that they use organic textiles, these products are also marketed to consumers who are typically health and environmentally conscious. However, we found that almost a third of them were being made with PFAS. This means these products are both a risk to the wearer as well as to the rest of us when they are eventually disposed of, since we know that these forever chemicals persist when they end up in landfills, contaminating irrigation and drinking water systems for all of us.”

PFAS have been linked to several adverse health conditions including immunosuppression, hormonal dysregulation, developmental delays in children, low birth weight and accelerated puberty, high blood pressure in pregnant women, and an increased risk of some cancers, such as kidney and testicular cancer. The chemicals are so prevalent that the Centers for Disease Control and Prevention has reported that PFAS, a class of manmade chemicals, have been found in the blood of more than 99 percent of all Americans.

Peaslee and Alyssa Wicks, lead author of the study, who conducted the research while a graduate student at Notre Dame, tested more than 70 products sourced from multiple markets in North America, South America, Europe and Asia-Pacific, including period underwear, reusable pads, menstrual cups and reusable incontinence underwear. Each product was screened using particle-induced gamma-ray emission (PIGE) spectroscopy, an ion beam analysis in which a proton beam bombards the surface of the material being tested, causing fluorine nuclei to emit gamma-rays, a type of high-energy light to measure total fluorine content when detected.

For products with multiple layers, Wicks analyzed each layer of each product for a total of 323 unique samples tested using PIGE.

PFAS can migrate off treated surfaces, raising particular concern when used in reusable products that come in direct contact with the wearer’s skin. Previous studies at other institutions suggest skin absorption could be a significant pathway to exposure to certain PFAS.

Even with this latest study, Peaslee said, “there’s still a lot we don’t know about the extent to which PFAS are being used in the manufacturing of these products, and too much we don’t know about the potential for these chemicals to be absorbed through the skin by the consumers who wear them.”

Another significant discovery of the study, according to Wicks and Peaslee, is that currently only a fraction of the brands that make reusable feminine hygiene products use PFAS intentionally.

“Only a subset of the products had high levels of PFAS present, which means that PFAS must not be essential in the manufacture of reusable feminine hygiene products,” Wicks noted. “This is good news in that it demonstrates PFAS are not required to produce these environmentally conscious products, and manufacturers should be able to make these textile products without chemicals of concern in them.”

The authors deliberately chose not to identify PFAS concentrations by brand, but they hope the peer-reviewed study will help identify the need for ingredient transparency in the industry.

“While we do know that these chemicals have been linked to serious environmental and human health issues, we do not yet know what fraction of these PFAS make it into humans by direct exposure and indirect exposure at the end of life of these products,” Peaslee said. “What this study, and others to follow, can do is help consumers ask manufacturers the right question: ‘Does this product contain any intentional use of PFAS?’ Currently, there’s no labeling requirement for these products, and only a handful of U.S. states have drafted legislation requiring consumer products to be free of intentional PFAS use. This paper and others like it will help regulators and manufacturers alike to identify product markets where PFAS are being used and to find better alternatives moving forward.”

In addition to Wicks and Peaslee, co-authors who contributed to the study while at Notre Dame include Thomas Hedman, Heather D. Whitehead and Alison Zachritz. Additional co-authors include Marta Venier and Sydney Brady at Indiana University, Bloomington.

Contact: Jessica Sieff, associate director of media relations, 574-631-3933, jsieff@nd.edu

Originally published by Jessica Sieff at news.nd.edu on July 22, 2025.