You may not realize it, but various everyday products like adhesives, food packaging, and cookware contain certain chemicals called per-and poly-fluoroalkyl substances (PFAS) to make them resistant to heat, oil, grease, or water. More than 9,000 PFAS have been identified so far, which are used in a wide range of industrial and commercial applications. 

Despite their important function in various consumer products, they have a serious downside. PFAS don’t break down easily in the environment due to their chemical structure that resists biodegradation. This explains why they’re often called “forever chemicals.”

“Their unique structure allows them to also move through surface and groundwaters and persist in soils and sediments,” says Allen Burton, a professor of environment and sustainability at the University of Michigan whose research deals with environmental toxicology. “They bioaccumulate in humans and wildlife and are so common their ingestion cannot be easily avoided.”

PFAS can leach into soil, air, and water, and they’re already found in humans’ blood and urine. Studies also report that PFAS are ubiquitous in municipal wastewater—not only in those with direct sources like textile mills or papermaking operations, but also in non-industrial wastewater like septic tanks and office buildings. Some suspect it comes from the microfibers in water-resistant clothing during laundry or from human excrement. However, new research reveals another potential source: toilet paper.

[Related: Are bidets really better for the planet than toilet paper?]

Chemicals called disubstituted poly-fluoroalkyl phosphates (diPAPs) are one of the major PFAS found in biosolids, the solid waste generated from wastewater treatment plants. With this understanding, researchers decided to look into toilet paper, a product where diPAPs are commonly used. Their findings in a recent Environmental Science & Technology Letters study suggest that toilet paper may be a major source of PFAS in wastewater treatment systems. 

“It is important to identify sources of PFAS so decision-makers can make informed choices on how to limit their environmental release,” says Jake Thompson, study author and a graduate research assistant at the Sustainable Materials Management Research Group at the University of Florida.

Thompson and his co-authors extracted PFAS from sewage sludge from eight US wastewater treatment plants and toilet paper rolls sold in four world regions, namely North America, South and Central America, Africa, and Western Europe. The most abundant PFAS in both samples was diPAPs, specifically, 6:2 fluorotelomer phosphate diester (6:2 diPAP).

The diPAPs are what you’d call precursor species of PFAS, which means they can be transformed into terminal or more stable PFAS that are known to have impacts on human and environmental health, such as perfluorooctanoic acid (PFOA) or perfluorodecanoic acid (PFDA). For example, the International Agency for Research on Cancer (IARC) classifies PFOA as “possibly carcinogenic to humans.” 

“These transformed species are often more polar and bound to soils and sediment to a greater degree, making them more persistent,” says Burton, who was not involved in the study. “In addition, as these compounds build up in soils and sediments over time, they are more available for [uptake] by soil- and sediment-dwelling invertebrates, and thus pose a food chain contamination threat.”

Based on their findings and data about PFAS levels in sewage and per capita toilet paper use in other countries, the authors estimated that toilet paper can contribute about 35 percent of the 6:2 diPAP in wastewater sludge in Sweden, 89 percent in France, but only around four percent in US and Canada. The impact of toilet paper in Sweden and France is higher because they have much lower 6:2 diPAP concentrations in wastewater sludge compared to North America. 

Furthermore, North America uses more toilet paper than other countries, suggesting that 6:2 diPAPs in US wastewater systems mostly come from other sources, like cosmetics, textiles, and food packaging, which are also worth looking into. The authors hope that by understanding potential PFAS sources, policymakers become “better equipped to address the challenge of PFAS,” says Thompson.

[Related: PFAS are toxic and they’re everywhere. Here’s how to stay away from them.]

Earlier this year, the Environmental Protection Agency (EPA) announced its new plans to develop wastewater pollution limits and restrict PFAS discharges from industrial sources, which were announced earlier this year. However, the ability of wastewater treatment plants to remove PFAS needs to be addressed as well. Currently, available wastewater treatment technologies don’t destroy PFAS. Conventional treatments can’t effectively remove them and may only pass them through to lakes, streams, and groundwater.

Burton says it’s not surprising to find PFAS in toilet paper and sewage sludge, which is “yet another documented widespread source of PFAS contamination of the environment.” But reducing PFAS in wastewater is only one strategy to minimize total exposures in the environment and the risk to humans and biota, he adds.

“Like microplastic contamination, it is most effective and efficient to prevent wastewater contamination by controlling the sources,” he adds. “Undoubtedly, they are effective substitutes for PFAS in making toilet paper and other consumer products.”

Disposable food packaging and food ware commonly use PFAS as an oil and grease barrier, but uncoated paper products, products made from bamboo and palm leaves, and reusable cutlery sets are viable alternatives. PFAS are also used in textile finishing to repel grease, stain, and water, but manufacturers can use melamine-based compounds instead. Non-essential PFAS use, like in personal care products and cosmetics, can be phased out completely.

“If society fails to dramatically reduce these multiple [PFAS] exposures,” says Burton, “we increase the likelihood of our children and wildlife facing serious risks.”