Cooking surface: 5/5 Excellent (slippery nonstick, browning can be a challenge especially if dark surfaces make it hard to see what you’re doing)
Conductive layer: 1/5 Very Poor (note that PTFE coatings are very thin so it will not impede the performance you receive from the underlying conductive material, which is usually aluminum)
External surface: 1/5 Poor (fragile and can offgas starting at 400F, at levels of concern to humans at 450-500F+; must keep away from fire from natural gas stoves)
Example: Dupont Teflon, Whitford Xylan
Health safety: 2/5 Poor (can offgas starting at 400F, at levels of concern to humans at 450-500F+)
PTFE stands for polytetrafluoroethylene. DuPont owns the trademark for Teflon, which is a specific type of PTFE. PTFE is an artificial chemical that you can think of as extremely slippery plastic. To prevent PTFEs from flaking off or abrading easily, cookware manufacturers often construct an aluminum pan like so:
- start with a base layer of aluminum and form it into the shape of a pan
- roughen the cooking surface (e.g., spray molten metal and/or ceramic onto it, or etch ridges on the cooking surface), which helps PTFEs adhere to the cooking surface
- apply PFOAs and PTFEs on the cooking surface
- bake the pan, which cooks off almost all of the PFOAs and leaves just the super-slick PTFE surface. (PTFE is so slippery that it does not like to bond to metal, hence the use of PFOA.)
Overheated PTFE produces all sorts of nasty chemicals, but non-overheated PTFEs are inert (won’t react with most other chemicals). Therefore, even if you eat PTFE particles, they should not interact with your body and should pass through you without harm. Even EWG admits that “[i]ngesting particles that flake off scratched non-stick cookware isn’t toxic because solid PTFE flakes are inert.”1 In fact, Teflon is used in all sorts of cooler-temperature applications, including lubricants, fabrics, carpet protectors, pipe thread seals, prostheses (even vocal cords), and linings for food dehydrator sheets. (I personally own and use an Excalibur 3900B 9 Tray Deluxe Dehydrator that reaches 155F and comes with PTFE-treated sheets. I did extensive research on PTFEs before buying the unit.)
PFOA stands for perfluorooctanoic acid and is also known as “C8.” PFOA pollution harms the environment, animals, and humans, and it takes decades to break down. That said, very little PFOA remains in finished nonstick cookware. Specifically, nonstick cookware is reheated after applying PTFE/PFOAs, which releases the PFOAs, leaving only extremely dilute concentrations of PFOAs in the cookware (a few parts per billion)–so dilute that cookware manufacturers sometimes advertise their PTFE-coated products as PFOA-free. Thus all properly-made nonstick cookware is nearly or entirely PFOA-free, regardless of whether the cookware is advertised as PFOA-free or not.
The US EPA in conjunction with companies like DuPont have agreed on a program to reduce PFOA emissions by 95% by 2010 (relative to 2000 levels) and to eliminate PFOA emissions altogether by 2015. A few companies have struggled to reduce emissions on time, such as BASF and Clariant, but for the most part the companies involved are on track to meet targets. For instance, DuPont’s PFOA/PFOA salts emissions are down 97% for 2011.
The risk is that chemical companies will replace PFOA with something as bad or worse, similar to how BPA-free plastics may be more toxic than plastic that contains BPA. It will likely take years before we find out for sure.
PFOS (perfluorooctane sulfonate) is something the EPA is studying as an “emerging contaminant” as of May 2012, since PFOS is persistent in the environment and can be transported long distances by air. PFOS and PFOA are fully fluorinated, organic compounds and are the largest made perflourinated chemicals. You may sometimes hear references to PFOS, but PFOA is the one to worry about for nonstick cookware.
Some people misunderstand how PFOA and PTFE are different and seem to think that the nonstick surface of cookware is PFOA, when in fact it is PTFE.
Please read the descriptions of PTFE vs PFOA (above) before continuing. Many people get the two mixed up.
Is nonstick such as Teflon “safe”?
The short answer is “probably yes” up to 400F for birds and about 450-500F for humans depending on ventilation and the specific PTFE. That is, you can go above 400F up to the manufacturer specification for maximum temperature if you don’t have pet birds nearby, though even if you have birds you might be able to go above 400F with good enough ventilation.2
Is nonstick such as Teflon worth the risk?
Including environmental concerns, it’s hard to argue that it’s worth the risk of polluting our environment to the point where most American contain trace amounts of PFOAs, which are used during the manufacturing process to produce PTFE-coated cookware. PFOA (also known as C8) is awful for the environment. Several big chemical companies are scheduled to drop their PFOA emissions to zero by 2015 via a US EPA agreement, but time will tell whether the replacement chemicals for PFOAs are better, as bad, or worse than PFOAs.
Furthermore, even if PTFE cookware had no pollution problems, all PTFE coatings will eventually wear down, so you will need to replace the pan eventually. There is no way to safely incinerate PTFEs, and many recycling plants are not equipped to recycle PTFE pans. Thus many PTFE pans wind up in landfills and contaminating the environment. (DuPont claims that ceramic pans only last 1/7th as long, with no further details that I can find. I suspect that DuPont means that ceramic pans don’t remain nonstick for nearly as long as Teflon-coated pans, which is apparently true of some ceramic pans that get horrible reviews from long-time users, though I also suspect that many people do not clean their pans as much as they think they are cleaning them, and that an invisible layer of crud remains on ceramic and thus prematurely decreases its nonstick ability. Try using Bar Keepers Friend on your ceramic before you toss the ceramic pans, and see if that helps restore some of the nonstickiness.)
Excluding environmental concerns, and focusing just on cookware buyers, PTFE may be worth the risk to careful cooks who stay below 400F when cooking. Less-careful cooks may want to consider alternatives to PTFE (e.g., carbon steel, cast iron, ceramic/enamel-coated cookware, and stainless steel, which can be made reasonably nonstick with proper preheating and oiling). As far as I can tell, people still buy PTFE-coated cookware because it is a) cheap, b) convenient to clean up regarding problem foods like eggs, and c) people don’t think they will overheat nonstick cookware.
However, if you’ve ever burned dinner before, you know that accidents happen, and it’s almost inevitable that a nonstick pan gets overheated at some point, if it’s used for high-temperature cooking. (This is especially true for high-inertia cooktops like electric coil, where even if you turn off the heat, the coil’s stored heat will keep increasing the pan’s temperature for a while anyway, so you would then have to take the pan off and put it somewhere else for a while to get the temperature back down.) Even DuPont admits that “[n]ormal temperatures for frying meat range from about 400°F (204°C) to 470°F (243°C),” which is uncomfortably close to DuPont’s own 500°F recommended maximum safe temperature for Teflon in cookware, let alone lower temperatures that others recommend. [Id.] Even I can’t easily tell how exactly hot a pan is just by look and touch (hovering my hand over the pan), and I preheat a LOT of pans for testing purposes. You can use little tricks like watching oil shimmer or smoke or rolling balls of water around to some extent, but all it takes is one accidental overheating session, and you can ruin the nonstick pan. You don’t even need to overheat the entire pan, just part of it, and that part will be degraded.
Of course, the risk of overheating is minimized if you use nonstick only for lower-temperature cooking like frying eggs (less than 300F). 300F is well below the offgas temperature of Teflon, so that’s pretty safe. And pots that you use for boiling water or making soups/stews are also unlikely to overheat, because the watery food will absorb and circulate heat, keeping pot temperatures down near 212F (100C).
In any case, you should know that many restaurants use PTFE-coated products, so if you want to avoid PTFE cookware entirely, you basically have to cook everything yourself. Even then, you will still absorb some PTFEs because they are so prevalent in all sorts of household products, lubricants, and even in plumbing. PTFEs are even used in prosthetic limbs, such as replacement knee parts, due to the low friction. I wouldn’t worry about PTFEs at such low temperatures, though–it’s overheated PTFEs that you should worry about.
How hot I can heat my nonstick pan?
One of the most anti-PTFE articles is at the Environmental Working Group’s site, so we’ll probe their lowest temperature numbers to see if they are legit.
EWG relies on studies of PTFE-coated heat lamp bulbs rather than cookware to support its claim that PTFEs offgas at 396F (202C), despite its article title which makes it sound like they were talking about kitchenware (“Canaries in the Kitchen: Teflon offgas studies”). It is not clear if the heat lamp bulbs used the same technology to bond PTFE to the bulbs that cookware manufacturers use to bond PTFE to cookware. Furthermore, I’m not sure how even the heating was or even how the researchers measured the temperature–of the bulb center, casing, etc. Given that EWG reviewed many studies, how the 396F offgas temperature study was at the extreme low end, and the possibility of measurement error or other confounding factors, it is possible that the true beginning of offgas is actually higher than 396F. Nevertheless, if you want to be extra-safe, the lamp bulb study implies that you should keep your PTFE cookware below 400F.
EWG also cites an apocryphal tale of a pet bird being poisoned by 325F (163C) fumes, but birds can get sick in various ways, so just because you cook on nonstick near a bird and the bird gets sick does not mean the heated Teflon poisoned the bird.
EWG goes on to cite a 1991 scientific article that they claim raises issues of PTFE stability.3 You can see the abstract for free, here: http://pubs.acs.org/doi/abs/10.1021/tx00020a017 The problem with the study is that it is unlike a typical home cooking scenario. The researchers superheated PTFE at nearly 800F, well above manufacturer-recommended thresholds, caught the offgas products, let those particles cool off, and then reheated those products at a lower temperature (464F) to produce fine particles of toxic gas. This “refried Teflon” study does not reflect real-life cooking scenarios, and even the study’s authors admit that the fine-particle offgas “loses toxicity in minutes.”
The rest of EWG’s article seems correct: overheated Teflon emits fumes and particles that are toxic, and even DuPont agrees that 500F+ temperatures will start breaking down PTFE. But that does not help us determine what the maximum safe temperature of PTFE is under normal cooking conditions.
So what IS the maximum safe temperature for PTFE cookware?
The extra-safe answer is ~400F depending on factors like ventilation, the specific PTFE involved, and whether the pan was already damaged from overheating a la the “refried Teflon” experiment.
But humans aren’t as vulnerable to PTFE offgas as birds, so we could probably tolerate something more like 450-500F based on the various Teflon studies.
However, there was apparently a non-peer-reviewed presentation in 1955 that mentions 200C (392F) as the temperature at which Teflon begins pyrolysis (breakdown).4 (The same presentation figured that Teflon does not emit enough toxins to pose a threat to animals until nearly 500F.) The 200C/392F number is the lowest number I’ve ever seen so far. Most research states a higher number, such as 260C (500F).5DuPont itself claims 500F (see footnote 3).
Even for pans marketed to be metal-utensil safe, use wood, silicone, nylon/plastic, or other soft utensils instead. Avoid using nonstick sprays which may contain propellants that damage the PTFE coating. If you must use a spray, use a sprayer that dispenses 100% oil such as a Misto and remember to run hot water through the sprayer every 2 months to keep it flowing properly. And obviously never heat PTFE above the manufacturer’s claimed maximum temperature, or over 400F if you want to be extra safe.
TIPS ON PURCHASING NONSTICK COOKWARE
If you want to buy a PTFE piece:
- Purchase brands that spray nonstick on the rivets or are rivetless. It makes little sense to buy nonstick that has sticky rivets that accumulate burned food particles and can house bacteria. An example of a good design is Anolon Nouvelle Copper.
- Avoid cookware that claims to be nonstick inside AND out. There’s a higher chance of gas or hot coils to overheat externally-applied PTFEs. Even if there is a metal base plate to shield part of the pan’s bottom, gas flames on “high” can overheat the PTFE on the exterior sides.
- Avoid PTFE-treated ovenware. PTFE does not belong in the oven, in my opinion. Oven heating elements can get quite hot, so even if you set an oven to 450F or whatever the ovenware maker recommends as a maximum, it’s possible that PTFE-nonstick gets too close to a heating element and overheats. Ovens also trap air, which means trapping offgas as well. For this reason, I don’t think PTFE and ovens mix well and would recommend never using any nonstick in ovens, even though that might limit your ovenware selection somewhat. (E.g., most roasting racks are covered with PTFE, but it is possible to find non-nonstick roasting racks that are made with chrome-plated steel or stainless steel.) Food-grade silicone can be oven-safe to very high temperatures and may be a viable alternative as well.
If you want to avoid PTFE, you need to buy pans that are both PTFE and PFOA free. You can tell whether a nonstick pan has PTFE or not by the marketing claims attached to the pan:
- If a pan doesn’t say anything about PTFEs or PFOAs, then technically that could mean anything. However, in practice, most marketers trumpet perceived advantages of their products as loudly as possible. Therefore silence probably means that the pan contains PTFEs.
- If a pan specifically says that it’s PFOA free but is silent about PTFE, then it’s almost certainly a PTFE pan, because the “PFOA-free” claim shows that the marketing team was thinking about the topic of PTFEs and PFOAs–and still didn’t claim PTFE-free. The only realistic way that would happen is if the marketing team could not legally claim “PTFE free” because the pan was, in fact, a PTFE pan.
If you care a great deal about the environment, you probably want to avoid PTFEs as much as possible due to the PFOAs involved in production and how PTFE coatings wear down, and while some pans may get recycled, many will wind up in our ever-growing mountains of waste in landfills. On the other hand, production of pretty much any cookware is probably going to pollute the environment in some way. For example, making steel requires iron ore, which means mill tailings, chemicals, and energy expenditures.
If we limit the scope of analysis to personal health and safety, PTFE-treated cookware is probably safe up to ~400F for birds, or 450-500F if you don’t have birds, depending on ventilation and the exact PTFE in question. That may not give much of a safety cushion for high-temperature cooking like frying chicken, but it’s plenty of room for error for lower-temperature cooking like boiling water or frying an egg.
Also, we should put risks into perspective. For instance, if you cook using less oil/fat because of nonstick surfaces, that may lower your risk of heart disease all else equal. Another example: cooking for yourself is one of the easiest ways to get a healthier diet, but if you would not cook for yourself at all if not for nonstick, then perhaps a case can be made for PTFE nonstick cookware.
For me personally, I tolerate PTFEs for my food dehydrator (most or all food dehydrators use PTFE sheets and only go up to about 160F). I also bought several nonstick pans for testing purposes, including a pair of Anolon Nouvelle Copper nonstick pans that I like. I gingerly use the pans for soft foods like eggs, so they ought to last me decades or longer. However, if I didn’t have to test so many pans, I could easily see myself using no PTFE cookware at all, for personal and environmental reasons.
- http://www.ewg.org/research/healthy-home-tips/tip-6-skip-non-stick-avoid-dangers-teflon ↩
- PTFEs may offgas at different temperatures. One common statement you may find online is that Teflon offgases at 446F according to DuPont’s own studies. However, I have not been able to find any such study, and I suspect that someone saw the 464F “refried Teflon” study and transposed the last two digits. DuPont does say that their nonstick coatings do not begin to deteriorate “in appearance or performance” until 500F: http://www2.dupont.com/Teflon/en_US/products/safety/key_questions.html#q5 However, offgas may begin at lower temperatures. ↩
- Seidel, WC., Scherer, KV, Jr.., Cline, D, Jr.., Olson, AH., Bonesteel, JK., Church, DF., Nuggehalli, S and Pryor, WA. 1991. Chemical, physical, and toxicological characterization of fumes produced by heating tetrafluoroethene homopolymer and its copolymers with hexafluoropropene and perfluoro(propyl vinyl ether). Chem Res Toxicol 4(2): 229-36. ↩
- Toxicity of Pyrolysis Products of “Teflon” Tetrafluoroethylene Resin by Zapp JA Jr, Limperos G, Brinker KC. Proceedings of the American Industrial Hygiene Association Annual Meeting, Cincinnati, Ohio, April 26, 1955. The text of the abstract is as follows:
Abstract: Teflon (9002-84-0), a physically inert tetrafluoroethylene (116-14-3) resin, is discussed in a paper presented at the American Industrial Hygiene Association Annual Meeting in Cincinnati, Ohio on April 26, 1955, and it is noted that its pyrolytic products are toxic, and exposure to various mixtures of them will induce polymer fume fever in humans. The latter influenza like syndrome has not been reproduced in animals. Sufficiently intense exposure of animals to Teflon’s thermal products, however, is generally lethal. The associated evidence of pulmonary edema, together with other early test results, originally suggested that hydrogen fluoride (7664-39-3) (HF) was the responsible toxic agent. The pyrolysis of Teflon starts at 200 degrees-C and proceeds slowly up to 420 degrees-C; at 500 to 550 degrees-C, the degradational weight loss reaches 10% to 5% per hour, respectively, depending on conditions. In the temperature range 300 to 360 degrees-C, hexafluoroethane (C2F6) and octafluorocyclobutane (C4F8) were identified as decomposition products. In the range 380 to 400 degrees-C, octafluoroisobutylene (also C4F8) could be detected and, at 500 to 550 degrees-C, the chief pyrolysis products other than tetrafluoroethylene (116-14-3) (C2F4) were hexafluoropropylene (116154), (C3F6) octafluorocyclobutane, and octafluoroisobutylene plus a complex residue of perfluoroolefins. Inhalation toxicity tests indicated that the octafluoroisobutylene gas, the most potent product, was approximately ten times as toxic as phosgene (75-44-5). The rat mortality factor seemed to be proportional to the product of exposure time and Teflon surface area as a function of pyrolysis temperature. Teflon 6, a lower molecular weight polymer than Teflon 1, produced more toxic pyrolysis products. Other kinds of industrial polymers were observed to produce lethal atmospheres under less drastic conditions than either form of Teflon. ↩
- http://www.sciencedirect.com/science/article/pii/S0141391097000979 ↩