[Pyramus]

"While PTFE is stable and nontoxic at lower temperatures, it begins to deteriorate after the temperature of cookware reaches about 260 °C (500 °F), and decomposes above 350 °C (662 °F).[58] Over 400 °C (752 °F) pyrolysis occurs and more decomposition becomes significantly more rapid. The main decomposition products are tetrafluoroethylene (TFE) and difluorocarbene radicals (RCF2).[58] The degradation by-products can be lethal to birds,[59] and can cause flu-like symptoms[60] in humans—see polymer fume fever."

https://en.wikipedia.org/wiki/Polytetrafluoroethylene#Safety

[ben_w]

> However these cases of polymer fume fever were mostly present in people who had cooked at 390 °C (734 °F) for ≥4 hours.

My oven goes up to 250 °C, though I never use it above 220. What cooking processes go to each of these thresholds?

[sgtnoodle]

It seems like a burner left on a dry pot or pan could easily do that.

Grills with PTFE coated utensils.

Commercial kitchens using specialized ovens and PTFE lined pans could be constantly putting out fumes.

Our propane pizza oven gets up to about 400C on the stone, and hotter at the flames. I don't think there's ever any PTFE near it, though. There do exist "non-stick" pizza peels, though, so someone could do that. The thing with peels on pizza stones is that their edges tend to grind down. I probably eat a miniscule amount of aluminum each time we make pizza.

[mjmahone17]

A broiler typically goes to or above 260°C. A pizza oven can pretty easily get above 400°C.

Not sure why anyone would use nonstick cookware in a pizza oven, but people make bad decisions frequently enough.

[RL_Quine]

Frying.

[ben_w]

I thought oil boiled at 300 °C, how do you get up to 390 °C?

[nate_meurer]

You don't, at least not on purpose. At 390 C you're filling your kitchen with smoke, and if you're cooking on gas you probably already have a grease fire on your stove.

However, it is shockingly easy to get a pan this hot by accident, with no more than a few minutes of inattention. I've seen people burn the non-stick coating off their pans on a couple of occasions after getting distracted by the phone.

It's risky to use nonstick cookware the same way you use bare metal pans, by heating the pan up to searing temperature before adding oil and food. I tell people to treat nonstick as though the food is already in the pan before they turn the heat on: don't turn the heat up high enough to burn the food, and the coating will stay safe.

It's worth pointing out that there isn't really any good evidence that fumes from burning PTFE cause permanent damage. There have been very few cases of verifiable PTFE "fume fever", in spite of the fact that lots of people burn up their nonstick cookware, and lasting effects haven't been obvious as far as I know.

[ruined]

there are many pet horror stories of bird deaths from PTFE pans, typically from accidents, but occasionally from normal use. one may assume that it happens quite often without a canary in the kitchen so to speak, and thus goes unnoticed.

also, damaging the coating is known to lower the temperature at which PTFE will pyrolize. anecdotally i don’t think i’ve seen a single teflon pan in anyone’s home that didn’t have some damage unless it was nearly new.

most situations that people are exposed to PTFE fumes are certainly below the level that triggers acute illness, but i wouldn’t be surprised if it was very common to get enough exposure to contribute to cancer, but it would be very hard to verify or test for that specific cause.

[nate_meurer]

The bird thing has attained mythological status, but I'm not convinced. The story appears to have been popularized by the 2003 "Canaries in the Kitchen" article from the Environmental Working Group. It should be noted that every one of the citations in this article is an anecdotal story. Nowhere do they cite any research showing that sub-pyrolytic heating of PTFE can kill birds in realistic environments.

One problem with the anecdata here is that birds can be killed by all kinds of other fumes and smoke, including ordinary cooking fumes, which makes it impossible to isolate the variables in a non-laboratory setting. Shit, you can kill birds with just the natural gas from your stove, or with the vaporized mineral oil burned off a new toaster.

As for burning up a nonstick pan, sure, I don't think anyone doubts that's lethal to birds. But I don't believe birds are harmed by nonstick cookware under normal conditions. If anyone has evidence to the contrary, I'd like to see it.

> damaging the coating is known to lower the temperature at which PTFE will pyrolize

Overheating can definitely impair the coating's adhesion to the cooking surface, which makes it more vulnerable to flaking in the future, but the breakdown temperatures of the coating system components aren't changed. They are what they are.

I have many well-used nonstick pans, some nearly a decade old, and on the inside they're flawless like the day I bought them. Except the one I gouged with an immersion blender. I use silicone, nylon, and wood utensils, and I don't overheat them.

> it would be very hard to verify or test for that specific cause.

It's not that hard to get good retrospective data. There are many thousands of workers who have spent years working in the fluorinated chemical industry, and as far as I know there's no evidence of higher cancer rates among that population.

[ben_w]

Given what I originally quoted said it only happens after four hours of exposure, your final paragraph does not surprise me.

[xyzzyz]

Yes, it becomes toxic at high temperatures, same as many other commonly used materials, eg. wood. Should we also be concerned about widespread use of woods because it becomes toxic when burned?

[Gigachad]

If wood was sold as cookware designed to get to high temperatures. Yes.

[xyzzyz]

Cookware is not designed to go to temperatures as high as those that cause decomposition of PTFE. But, there is plenty of wood cookware in common use. Spatulas, pot handles, etc.