What is ‘Teflon flu’? It’s linked to a coating on some nonstick pans.

Over the last two decades, poison centers in the U.S. have received more than 3,600 reports of suspected cases of “polymer fume fever,” a flu-like illness linked to a chemical coating found on some nonstick pans.

The condition has been colloquially referred to as “Teflon flu,” after the trade name of a popular nonstick coating. But the health questions are not specific to any particular manufacturer.

Last year, there were 267 suspected cases of the little-known illness, which is believed to be one of the highest reported totals since 2000, according to America’s Poison Centers, a nonprofit organization that oversees 55 U.S. poison centers.

Teflon and many other nonstick pans are made with polytetrafluoroethylene (PTFE), which belongs to the larger class of substances known as PFAS (per- and polyfluoroalkyl substances)- or “forever chemicals,” because of their ability to persist in the environment for years.

Studies have found nonstick pans made with PTFE are safe to cook with when used as instructed. But at very high temperatures — when a nonstick pan is exposed to temperatures above 500 degrees Fahrenheit — the coating can start to degrade and burn off potentially harmful fumes.

Julie Weber, the director of the Missouri Poison Center, said questions about how to use nonstick pans are more common than reports of polymer fume fever. Weber said it’s important to use the pans as directed. “A lot of this comes down to a person really not cutting corners, following directions and using things properly,” she said.

So how should you use nonstick pans? The Washington Post spoke to several experts about polymer fume fever and the coating on nonstick pans. Here’s what they said.

What is polymer fume fever, and how common is it?

Polymer fume fever is a set of flu-like symptoms associated with breathing fumes from an overheated nonstick pan or any product that uses PTFE. Regional poison centers record suspected cases when consumers contact them, but the only way a case can be verified is by a health care provider, so it’s often not known whether the cases reported to poison control are confirmed.

Kaitlyn Brown, the clinical managing director for the nonprofit, said in an email that the number of cases remains “relatively small” when compared to other substances. But Maryann Amirshahi, the co-medical director for the National Capital Poison Center in Washington, said she believes incidents of polymer fume fever may be underreported because the symptoms — including a fever, chills and a headache — can develop hours after inhaling the fumes. People may confuse it with a cold.

“If you have a fever and you have body aches, you don’t always think that it’s something that you inhaled,” Amirshahi said.

B. Zane Horowitz, the associate medical director of the Oregon-Alaska-Guam Poison Center, said “it’s pretty rare to get calls” nowadays regarding an exposure, and any symptoms usually last a day or two.

Chemours, which owns the Teflon trademark, declined to comment about suspected cases. Chemours said in a statement that there is over a decade of scientific data confirming the safety of the materials it uses in nonstick coatings. “Multiple studies demonstrate that it does not bioaccumulate and, if incidental exposure were to occur, it’s rapidly eliminated from the body,” the statement read.

Calphalon, which sells cookware made with and without PTFE, said in a statement the PTFE coating “complies with FDA regulations that approve its use in food-contact applications, as it does not negatively interact with food or the body.”

A Food and Drug Administration spokesperson said in an email the agency is not aware of any research demonstrating the PFAS used in nonstick cookware “presents a safety concern for consumers.” The spokesperson also said all substances used in “food contact products” are subject to rigorous scientific review by FDA scientists.

What fumes come from nonstick pans?

Studies have found the coating on some nonstick pans can degrade when heated to very high temperatures. “It’ll burn and release a very complex mix of oxidized, fluorinated substances,” said Zac Hudson, an associate professor of chemistry at the University of British Columbia. “This is why they tell you: Don’t heat your Teflon pan to a high temperature.”

In a small study, researchers in Germany placed empty nonstick pans on a hot stovetop for 30 minutes and measured the emissions of different PFAS in the air. The pan that reached the highest temperature — around 698 degrees Fahrenheit — had the highest emissions. They said the emissions under “normal application temperatures” don’t pose a human health risk.

Experts said nonstick pans should never be preheated, and typical cooking methods, on medium to low heat, won’t result in such high temperatures. Case reports of polymer fume fever have involved people who leave a heating nonstick pan unattended. In a 2012 BMJ case report, a 29-year-old man in Japan reportedly fell asleep while boiling water in a PTFE-coated pan. He woke up five hours later to a room filled with white smoke, and he developed a fever, cough and difficulty breathing. He recovered within a few days.

Why should bird owners be cautious about heating nonstick pans?

Birds are particularly sensitive to toxic fumes — that’s why canaries were used in coal mines — and the fumes caused by overheating a PFAS-coated pan can kill them. A warning on Teflon’s website states bird owners should keep their birds out of the kitchen while cooking.

How should I use nonstick pans?

• Avoid preheating nonstick pans. Empty nonstick pans can reach high temperatures very quickly, according to Teflon’s guidelines. Always heat with food, butter or oil already in it.

• Don’t broil or bake at high heat. Instructions for PTFE-containing nonstick pans, such as Calphalon, advise consumers the cookware is oven-safe up to 450 or 500 degrees Fahrenheit. The exact temperatures will vary depending on the pan and manufacturer. Teflon’s guidelines, for instance, state: “Do not use nonstick cookware and bakeware in ovens hotter than 260°C (500° Fahrenheit).”

• Use exhaust fans or open windows when cooking. Open windows and turn on an exhaust fan, if you have one. If there’s smoke in the kitchen, for whatever reason, “you shouldn’t be breathing that smoke,” no matter where it’s coming from, said Horowitz, of the Oregon-Alaska-Guam Poison Center.

• Don’t use stainless steel or hard utensils on nonstick pans. Use wood, silicon or nylon utensils to prevent scratches on the surface of nonstick pans.

Do experts use nonstick pans at home?

Experts say contaminated water and food supplies are probably greater sources of overall PFAS exposure than nonstick pans. But six experts interviewed said they avoid using nonstick cookware at home.

“It is undoubtedly a contributor to people’s exposures,” said Jamie DeWitt, the director of the Pacific Northwest Center for Translational Environmental Health Research at Oregon State University. “But it’s a very small slice of the pie.”

Dan Jones, a professor of biochemistry and molecular biology and the associate director of the Center for PFAS Research at Michigan State University, told The Post he uses nonstick cookware “almost every day.”

“We don’t really know how much of our exposure comes from nonstick cookware,” he said. “Most of us who work in the field would say it’s probably a very tiny fraction.”

Is it safe to use a scratched nonstick pan?

Inhaling the fumes from an overheated pan is thought to be riskier than ingesting the coating itself. PTFE is a larger molecule than other kinds of PFAS and researchers say the chemical’s size makes it difficult for the body to absorb it. Companies that make nonstick pans say the coating is inert and not toxic if ingested.

“I presume we’ve all ingested a bit of PTFE that’s flaked off our pan into our food,” said Ian Cousins, an environmental chemist and professor at Stockholm University. “I wouldn’t be concerned about that, actually. It’s just going to go straight through your body.”

But Cousins said “I wouldn’t want to breathe in those fumes,” if the pan was overheated. “It’s a real mixture of gas-phase fluorinated substances,” he said. “In general, you don’t want to breathe in a whole mixture of synthetic, organic, gaseous compounds.”

Laurel Schaider, a senior scientist at the Silent Spring Institute, a nonprofit research organization based in Massachusetts, said flaking or peeling nonstick coating is a sign to her that it’s time to stop using a nonstick pan.

“When we think about PFAS, it’s really the accumulation of day after day, month after month, year after year,” Schaider said. “If it’s something that you use every day in your house, I think that’s something to pay more attention to.”

And there’s emerging research suggesting the PTFE on nonstick pans could add to the growing collection of -microplastics in the environment.

Which nonstick pans are PFAS-free?

Shopping for nonstick cookware can get confusing. Certain nonstick pans claim to be free of PFOA — one type of PFAS. But there are thousands of different PFAS, and those promises don’t mean a product is free of all of them.

Look for brands that promise to be free of all PFAS or all fluorinated compounds, said Jennifer Hoponick Redmon, a senior environmental health scientist at RTI International.

If you’d rather avoid nonstick altogether, opt for cast iron, stainless steel or ceramic pans. Ceramic coatings are often made of silicon dioxide, or silica, and aren’t made with forever chemicals, said Gillian Miller, a senior scientist at the Ecology Center, a nonprofit advocacy group based in Ann Arbor, Mich.

Companies such as Caraway, Our Place and GreenPan sell ceramic pans that are PFAS free.

Certain companies such as Nordic Ware and HexClad say their nonstick cookware no longer uses PFAS. Groupe SEB, the maker of All-Clad and T-fal, said the company uses PTFE, and its pans are safe to use, but it is investing in the development of alternative coatings.