Clothing that's waterproof or stain resistant might seem like a bonus, but these words could be a tip-off that an item contains a toxic class of chemicals called per- and polyfluoroalkyl substances (PFAS). PFAS became popular in the US around the 1940s when manufacturing companies realized they could resist heat, grease, stains, and water. They're often referred to as forever chemicals since they can linger in the environment for thousands of years. Though many PFAS have been phased out of the manufacturing industry, the chemicals can still be found in leather and textiles. Labels that contain the words Gore-Tox or Teflon may signal the presence of PFAS, which are commonly found in outdoor gear and moisture-wicking workout clothes. Exposure to PFAS has been associated with kidney and testicular cancers, liver damage, and developmental issues, but humans are more likely to be exposed by ingested contaminated food or drinking water. The Centers for Disease Control (CDC) considers skin contact a minor source of exposure, though breathing in dust from PFAS-contaminated clothing can also constitutes low level exposure. Phthalates are known for making substances like plastic durable and flexible. Although Congress instituted a federal ban on phthalates in toys and children's products in 2008, the chemicals continue to be used in manufacturing. In 2012, the environmental watchdog Greenpeace sampled more than 140 clothing items and detected phthalates in 31 garments. Three t-shirts and a pair of underwear from popular clothing brands had very high concentrations of phthalates, meaning the chemical comprised up to 38% of their weight. Phthalates have also been found in jeans, raincoats, and artificial leather. The chemicals have been linked to ADHD, asthma, diabetes, and breast cancer, along with a number of reproductive issues, including decreased reproductive functions in men and endometriosis in women. For now, phthalates pose the greatest risk to children, who might put contaminated clothing in their mouths. The CDC has said that the human health effects of phthalates are unknown, but exposure is widespread in the US.Children are particularly susceptible to toxic chemicals since their bodies are still developing. They also weigh less, so their exposure can be higher. That explains the public outcry in 2006 and 2007 when the Center for Environmental Health (CEH) found lead in vinyl baby bibs sold at Walmart and Babies R Us. Five of the bibs contained lead levels above 600 parts per million — the safety threshold set by the Consumer Product Safety Commission at the time (the threshold has since been lowered to 100 parts per million). The products were quickly recalled nationwide. Children exposed to lead can suffer permanent brain damage, which often results in learning disabilities and increased violent behavior. While bibs made of vinyl (a shorthand for polyvinyl chloride, or PVC) aren't sold as often today, it's still possible to buy them. If your new clothing smells like chemicals, it's likely due to formaldehyde, a colorless gas that's frequently associated with embalming. The chemical helps to keep clothes free of wrinkles, static, or stains, even after multiple washes. That means that formaldehyde can't always be scrubbed off with detergent and water. In 2010, the US Government Accountability Office (GAO) released its findings after testing 180 pieces of clothing for formaldehyde. The office found that most of the samples were below 20 parts per million — what's considered a nondetectable level of formaldehyde. While inhaling the chemical has been linked to asthma, nausea, and even cancer, wearing clothes with formaldehyde is more commonly associated with dermatitis, which tends to affect those already allergic to the chemical. Symptoms of dermatitis include rashes, blisters, and itchy, dry skin. Read more: Toxic chemicals in your home could be linked to cancer, autism, and reproductive issues. Here are 4 of the most concerning. The blue dye that rubs off your new pair of jeans is likely azo dye, the most common form of dye used in textile production. Azo dyes can release cancer-causing chemicals called amines, though some have been found to be carcinogenic because of other chemicals. Certain forms of azo dyes have already been banned from clothing in the European Union. Some also require a warning label under California's Proposition 65 — a state law that requires businesses to alert residents about significant exposures to toxic chemicals — though there is no ban in the US. Thus far, scientists have determined that the health risk to consumers is relatively low, but the potential link to cancer warrants further study. Of the more than 140 clothing samples that Greenpeace tested in 2012, almost 90 garments showed evidence of a chemical group called nonylphenol ethoxylates (NPEs). In addition to being used during clothing production, NPEs are found in laundry detergent. EU manufacturers have been banned from producing clothing with NPEs since 2004. The chemicals have been associated with reproductive and developmental issues in rodents and have been found in human breast milk, blood, and urine. The bigger concern is what happens when they're washed off your clothing. NPEs have been known to leech into waterways, posing a severe danger to aquatic animals. Animal hide is treated by a process called tanning that turns it into leather. Since the days of the Industrial Revolution, tanning has relied on chromium, a chemical that makes leather stretchy and pliable. In 2014, a slew of products were either withdrawn or banned from entering the EU because they contained hexavalent chromium, a form of the chemical that's considered dangerous to human health. Though hexavalent chromium can cause skin irritation, a 2015 Swedish study found that the chemical becomes less potent over time when it comes into contact with skin through leather. As with other chemicals found in clothing, consumers have a lower health risk compared to leather or textile workers who work directly with toxins on a regular basis. The higher the dose and the more a person is exposed, the greater their chance of getting sick.