Thread carefully: your gym clothes could be leaching toxic chemicals

When we’re on the treadmill, we’re more likely to think about which SZA song to queue up or whether we’re going to get another mile in than what’s in our workout clothes.

But your favorite sports bra or worn-out leggings are probably made of synthetic fabrics like spandex, nylon, and polyester, all of which are essentially plastic. These materials are made from petrochemicals and are often formulated with harmful chemical additives such as phthalates and bisphenols.

Now, new research shows that sweat leaches chemical additives from plastics and those chemicals can then be absorbed through our skin.

What has the research yielded?

The research focused on a class of compounds called brominated flame retardants (BFR), which are used to prevent combustion in a wide range of consumer products, including fabrics, and are linked to adverse health effects such as thyroid disease, hormonal disruptions and neurological problems. Researchers from the University of Birmingham found that because sweat contains oil and oil has a lipophilic chemical nature that encourages the chemicals in plastic to dissolve and disperse, the oil in your body can leach chemicals from the plastics you touch.

In short, oily substances in our sweat “help the bad chemicals get out of the microplastic fibers and become available for human absorption,” says Dr. Mohamed Abdallah, associate professor of environmental sciences at the University of Birmingham, and lead researcher on the study.

The Birmingham team focused on flame retardants, which are added to some fabrics but not specifically associated with sportswear, and ran test cases based on how much sweat and plastic come into contact as people sit at home. Further research is needed to determine the type and amount of chemicals a sweaty gym-goer would absorb from their synthetic workout clothes and the gym environment.

But Abdallah says the research implies that other chemical plastic additives, such as bisphenols (which have been). found it at up to 40 times the safe exposure limit in items from popular sportswear brands), phthalates and PFAS, “can leach into sweat and become available for absorption through the skin.” These findings can be “logically extrapolated in terms of someone who runs and sweats intensely,” he notes. The bottom line is that the more you sweat, the more chemicals you can absorb.

Why does this matter?

Previously, researchers have tended to focus on our exposure to plastic through food, but the Birmingham study raises awareness that people can also be exposed to plastic chemicals through our skin. And because harmful chemicals in plastics bioaccumulate – or slowly build up and linger in our bodies – repeated exposure to multiple sources can leave us with high levels of chemicals in us, potentially contributing to health effects.

New research published the journal Environmental Pollution found a total of 25 flame retardants in the breast milk of 50 American mothers last month; each sample contained certain flame retardant compounds that the US began phasing out a decade ago due to known damage. Another study in August, an increasing number of cancer cases were diagnosed among Americans under 50, especially in women, with rates of gastrointestinal, endocrine (including thyroid), and breast cancer rising most rapidly. While the exact cause of this wave remains undetermined, experts speculate that exposure to a wide selection of harmful pollutants and cancer-causing chemicals is a contributing factor.

Alden Wicker’s 2023 book, To Dye For: How Toxic Fashion is Making Us Sick, delves into the many ways we are exposed to chemicals through our clothes. According to Wicker, workout clothes, especially those marketed as “sweat-wicking” or water-repellent, often contain PFAS, the notoriously carcinogenic and widespread family of “forever chemicals.” Due to industrial pollution and their widespread use in everything from frying pans to toilet paper, you can find some amount of PFAS just about anywhere, but they can appear in high concentrations in clothing treated with certain high-performance, water-resistant finishes. “Things like Gore-Tex, that’s just pizzazz,” she says. “That’s just a kind of PFAS coating.”

Wicker notes that polyester fabrics are usually colored with spreading dyes – a family of chemical dyes used on plastics that are known to be skin irritants, especially for children and those with sensitive conditions such as eczema.

And those are just the toxins we know about. “Research shows that there are many more chemicals present in everyday plastic products than ‘just’ the infamous ones, such as flame retardants,” says Martin Wagner, a biologist who studies the effects of plastic on humans at the Norwegian University of Science and Technology. , who is not involved in the Birmingham study. “The latest estimates indicate that there are more than 13,000 plastic chemicals in existence. Because most of these have not been studied for their health or environmental impacts, there is an urgent need to improve the safety of plastics,” he wrote in an email.

Opaque supply chains mean that even manufacturers are unaware of everything that goes into their plastic products. “Most fashion brands don’t know who dyes, finishes and manufactures their materials,” says Wicker. “And those suppliers will be incentivized to do things as cheaply as possible, to obtain cheaper chemicals from uncertified sources that may be contaminated with heavy metals and other hazardous substances.”

What should I do about it?

An easy way to avoid exposure to these chemicals is to wear clothing made from sustainably sourced, minimally processed natural textiles, which do not contain the toxins associated with plastic materials. Check fabric labels for items that consist primarily of organic cotton, hemp, or merino wool (some percentage of elastane or lycra in sportswear is almost unavoidable due to the stretch). Look for meaningful designations from third-party textile certifiers such as the Global Organic Textile Standard (Gots) and OEKO-TEX, and visit brand websites to see if they make an effort to list their suppliers; they know best where their products come from, down to their dyeries and factories.

California Proposition 65 requires companies to provide warnings about significant exposure to chemicals that cause cancer, birth defects or other reproductive harm. But stricter federal legislation is needed to ensure that consumer products do not contain harmful chemicals, regardless of the state in which they are sold.

One recent brand questionnaire found that 72% of respondents would buy plastic-free sportswear if it was readily available. But even with the best intentions, “getting rid of all your synthetics and revamping your wardrobe can be expensive,” says Wicker. “I would say take it a little at a time unless you have chronic health conditions, serious concerns or reactions to some of these materials.”

Abdallah says he minimizes synthetic fabrics in his home and trains wearing natural fibers like cotton. “Why would you be exposed to these chemicals, even at low levels?” he says. “Why not avoid the risks?”