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Are PTFE, Teflon, and Other "Non-Stick" Polymeric Coatings Safe?

LOCKED DISCUSSION

As the moderators have pointed out, when the subject of "non-stick" pans and their coatings comes up--as it frequently does in connection with other topics--it can lead discussion off the original topic. Therefore, it gets a thread of its own.

What say you? What are the data, the holes in the data, and the common sense of putting these coatings in contact with our foods under high heat? Should we worry even if there are no definitive, peer-reviewed scientific studies that resolve all the issues one way or another? Or, should we take what little is out there as a once-and-for-all determination that it is safe?

This is a touchy subject, as evidenced by how mention of this topic frequently results in abrupt, unexplained pulldowns. No references to politics, salty language, or name-calling. So let's all be polite, and stay on thread, and see what happens, hmmm?

  1. I'm curious about this as well. We have several non-stick pots/pans. We've thrown lots of them away after they started to wear out too. We generally aren't the type to worry too much about these types of things, it's usually more about the pan not being non-stick any longer. We have stopped micrwaving plastic (cottage cheese/sour cream tubs) in the microwave, no loss there.

    1. Kaleo

      I actually didn't read the post closely, so I didn't know it was you. Now that I notice it is you. I think it is interesting.

      Ok. There is no data shows PTFE/Teflon as dangerous in its original form. PTFE is actually a very inert/ non-reactive material. I would have no problem eating Teflon directly. There are some concerns about the fume when the cookware get heated up to >300oC, but that is probably not what you are talking about, right?

      To be honest, there are a few other posts discuss about this Teflon safety thing.

      1. My opinion, it's safe, don't heat it above 500°F, I don't know if that's high heat or not in your opinion.

        PTFE (polytetrafluoroethylene) is a fluoropolymer, one of several fluoropolymers actually. It's melting point is 327°C (620°F), when it's applied to pots and pans it is heated beyond that point to get the material to flow. During this process most if not all PFOA is flashed. The industry states that PTFE degrades at temperatures above 500°F, that is an agreed upon value among manufacturers and can readily be found in the literature. That's 50°F higher than the melting point for tin, so I know you don't cook any hotter than that ;) What happens avove 260°C, PTFE decomposes above 350°C, this is where the flu-like symptoms occur, don't get your cookware that hot. Frying meat is usually in the 200 - 230°C range and cooking oils, or at least most of them smoke before that 260°C temperature is reached, so if your oil is smoking, your pan is too hot. All this says to me is that cooking with PTFE is not childs play, you can get it too hot, however keep reading.

        PTFE (fluoropolymers) are used to make synthetic components for the human body (implants) such as vascular grafts, cardiiovascular patches, etc. granted, these should not see anything near cooking temperatures or you have other issues to contend with.

        The pyrolysis of PTFE is detectable at 200°C, and it evolves several fluorocarbon gases and a sublimate. Animal studied indicate it is unlikely that these products would be generated in amounts significant to health at temperatures blelow 250°C. Most of the health studies were concucted a long time ago, keep in mind PTFE has been around since before I was born (PTFE was developed in the late 1940's).

        So to answer the question of the OP, industry data and studies by independent laboratories would indicate that if kept below 500°F, which shouldn't be all that difficult, it's very safe, at much higher temperatures, you might want to open a window, or as a minimum keep a bird in the kitchen:

        References:

        ASM International Volume 2 Engineered Materials Handbook "Engineering Plastics", section on Thermoplastic Pluoropolymers.

        Teflon (PTFE) Thermal Decompositon Products, Fluoride Action Network Pesticide Project.

        "Toxicity of pyrolysis products of Teflon tetrafluoroethylene resin", Proceedings of the American Industrial Hygiene Association Annual Meeting.

        1959 study conducted by the Food and Drug Administration.

        1 Reply
        1. re: mikie

          "That's 50°F higher than the melting point for tin, so I know you don't cook any hotter than that ;)"

          :) That is salty language :P

        2. Actually, the Chowhound Team doesn't like ANY discussions regarding the safety of surface coatings. IIRC, they feel something along the lines of, "discussions of this nature are beyond the scope of CH's focus." They want us all to play nice & not stir the waters.

          IMO, since it's something we all use in contact with our food, it's something we should be discussing. But then again, it's not my forum..... ;-)

          44 Replies
          1. re: Eiron

            Interesting, but then we have talked about why we have to line copper cookware with tin or stainless steel because copper is known to have toxicity.

            1. re: Chemicalkinetics

              Good point, so maybe it's just the kind of back-&-forth activity that Teflon discussions generate? (& back-&-forth, & back-&-forth, & back-&-forth, & back-&-forth....)

              1. re: Eiron

                Yes. I think it is just that some of the conversations on Teflon get heated up to very "unintellect"and "unconstructive" manners, such as name calling or changing definition or ....

                I think back and forth is probably fine if the people who engaged the issues are honest about it.

            2. re: Eiron

              Eiron: That was my sense, too, but not what the mods said in their (rare) explanation that truncated the discussion that led to this dedicated thread. So let's take them at their word. If they're hosting a cookware board, it'd be extremely weird to make this topic verboten or kapu. [Second edit; Rehetotical question redacted]

              What is your persoinal experience you alluded to in the earlier thread, Eiron?

              I am struck by several aspects of this story. I believe the US Government has not visited this issue since its study in 1955. Since then, it has been determined in veterinary medicine and wildlife biology circles that birds are particularly prone to PTFE toxicity at PPB levels the earlier studies considered totally safe. My understanding is that there have been documented kills in aviaries attributable solely to boiled dry nonstick cookware. My thinking is: if it kills birds in my neighborhood, what am I breathing? Think canary in the mine. It also makes me wonder how more advanced the measurement technology is today versus 1955.

              I also wonder at the aspect of PTFE and PFOA being cut a lot of slack because of their use in nuclear fuel enrichment and refinement. My understanding is that its first industrial use was as pipe lining for radioactive gases and liquids in weapons development and processing during the Manhattan Project. Materials with "national security" implications (e.g., so-called "spent" uranium munitions) seem to get litle or no official scrutiny after getting their initial scientific blessing.

              Next, PTFE is found on a lot of cookware that goes--intentionally--to surface temperatures 500F and above--skillets, fry pans, roasters, rosting racks, burner pan liners, spiders, self-cleaning oven liners, etc. This does not count the UNintentional high heat exposures caused by accident or neglect. TWO to FIVE Minutes of unattended nonstick cookware on high heat can release very toxic products. See, http://www.avianweb.com/teflon.htm. Burned or pyrolysized PTFE in a housefire situation is 1000 times more toxic that wood or most other materials. See, http://onlinelibrary.wiley.com/doi/10.... And the more used, scarred up or worn your nonstick is, the GREATER the likelihood and lower temperature at which further degradation occurs.

              The principal thermal decomposition byproduct of PTFE is Perfluoroisobutene (PFIB, 1,1,1,3,3-penta fluoro-2-trifluoro methylpropene, CAS No. 3812-21-8), a fluoro-olefin. PFIB is TEN TIMES as toxic as phosgene gas, and is specifically listed under Schedule 2 of the Chemical Weapons Convention. See, http://www.asanltr.com/ASANews-98/pfi....

              [My edit: Rhetorical question redacted]

              Finally (for now), I am cynical about anything DuPont and other manufacturers who stand to profit from PTFE and PFOA have to say about its safety. DuPont is a recognized offender in suppressing unfavorable environmental studies, and has been fined tens of millions of dollars for doing so. In the 1990s, it carefully negotiated a consent decree with the US Govt. that allows it to continue to use PFOA until the YEAR 2015.

              1. re: kaleokahu

                "And the more used, scarred up or worn your nonstick is, the GREATER the likelihood and lower temperature at which further degradation occurs."

                Since you didn't site a source for this statement, I'll assume it's conjecture. However, the greater the wear, the less material there is to degrade, so intuitively, there would be less volatiles as there is a smaller source. Also thermal degredation and pyrolysis requires a threshold temperature to be met, so old worn out pots will not pyrolize at a lower temperature than a new pan and won't have as much material available to provide a source for the outgassing.

                I agree the studies are old, but that's what's available, we're just beating what many have considered to be a dead horse, no pun intended.

                Since aviries are typically closed structures, or at best limited air flow, any gases could accumulate in one spot at higher concentrations, this would not be applicable to your neighborhood bird life, unless you live in the Super Dome.

                I don't think the studies ever said there are no bad things that come off of a PTFE pan, it's just that they come off in very small amounts and only when the pan is used outside it's operating limits. I consider a house fire to be outside the operating limits. And there is more bad stuff from your burning couch than your burning frying pan in a house fire. It's not just about what, but also how much and under what conditions.

                BTW, I only have one PTFE coated 8" frying pan, it's not like I use the stuff all the time.

                1. re: mikie

                  mikie, I would suggest that used/scarred/worn non-stick would actually create MORE surface area due to the now-irregular surface. Greater surface area can result in greater reactivity, as evidenced by grain dust generated in storage silos (as an example, only; I'm sure you've sprinkled non-flammable bread flour onto a candle flame to watch it flash like gun powder).

                  I have no problem with anyone else using Teflon-coated pans. My wife & daughter love the ones we have at home. I've simply asked them not to cook anything for me in them.

                  1. re: Eiron

                    My assertion that an old pan has less potential is based on two factors: 1) If the surface is worn, from abrasion with utensiles, there is in fact less of it, i.e. less total mass of material to provide a base for thermal degredation. If for example a pan has a 2 mil. coating and is worn to 1 mil, from abrasion over time, it now has half as much mass or volume. All other things being equal, you can only get half as much out if you only have half as much to start with. And 2) There is only so much material that can come out of a given mass of overheated PTFE, once this material has been driven off by heat there is nothing left to off gas. It's not like you generate PFOAs in a Teflon pan, you can only simply drive off any excess that's there. Once it's gone, it doesn't come back.

                    As interesting as the topic is from a technical stand point, I seriously doubt that anyone is going to be swayed by anything anyone else posts. The two camps will simpley dig in and continue to support their previous convictions. For those who are chemaphobic the simple solution is don't cook in PTFE coated pans.

                    1. re: mikie

                      Thanks for your well-articulated posts, too, Mikie.

                      "As interesting as the topic is from a technical stand point, I seriously doubt that anyone is going to be swayed by anything anyone else posts. The two camps will simpley dig in and continue to support their previous convictions."

                      I honestly have found the discussion here to be much more civil than I expected, given the topic. Both sides have provided info and have linked to things that may be of concern.

                      "For those who are chemaphobic the simple solution is don't cook in PTFE coated pans."

                      I absolutely agree. As Chemicalkinetics said below, the most important thing is that you should be comfortable with your cookware. If you are suspicious about some element of it or don't like some aspect of it, it will probably sit on your shelf most of the time anyway -- so get something you like and will use.

                      1. re: athanasius

                        "I honestly have found the discussion here to be much more civil than I expected, given the topic. "

                        Yes, I am also find the discussion here to be more civil based on the topic. No, I am not surprised that the discussion here to be civil based on the posters here. The posters here are known to be respective and knowledgeable.

                        I think it is not the topic, but the people, you know :)

                  2. re: mikie

                    Mikie:

                    I actually DID have a citation for that, but lost it. It's consistent with the findings that old Nalgene bottles are actually worse leechers than new ones. [Edit: Haven't found that citation yet, but did find this one: http://www.scientificamerican.com/blo.... Good News? Nope--PFOA' s deleterious effects on human fertility

                    ]

                    You are right about threshold temperatures needing to be met, but it gets squishier when you try to pin it down exactly. If, as these sites claim, 2-5 minutes of an unattended dry pan puts ultra-hazardous PFIB and PFOA in the air, that's not a theoretical concern anymore. And IS there an allowable ppb or GRAS for PFIB? I doubt it.

                    1. re: kaleokahu

                      The article summarized by that SA blog entry concludes that PFOA and PFOS 'might be a factor'. But is PTFE cookware a significant source of PFOA? Neither the SA blog, or the original article mention cookware as a source.

                      In one study cited in the Wiki article on PFOA, cookware was at the bottom of the list of tested products which might include PFOA. Various water repellents and stain treatments were much higher. Even wax paper is (or was) treated with PFOAs.

                      1. re: paulj

                        Paul: My understanding is that PFOA is used as a surfactant with all PTFE cookware, otherwise it won't stick (rimshot, please) to the pan. So it's there. And I believe the "necessity" of using it is why the feds allowed DuPont and 3M to continue making PFOA out to 2015.

                        It would make a lot of sense that you could dose yourself with much higher levels by spritzing Scotchguard on your clothes and furniture than by cooking it out of your PTFE pan. So maybe cookware belongs further down the list. But it's still there. And we're also ignoring the nastiest PTFE thermal degradation product, PFIB.

                        One dirty little secret here is that the PTFE/PFOA duo is a big part of what makes Gore-Tex work.

                        Teflon waxed paper...THERE'S and idea, hmmm?

                  3. re: kaleokahu

                    Kaleo -

                    Thanks for starting this thread. It's interesting to hear perspectives on this.

                    Am I the only one having trouble following your links? I get "page not found" notices.

                    When it comes to any chemical safety/toxicity question, I think it's always important to keep in mind that you can *never* prove something to be completely "safe." At some level, every chemical -- even water -- is toxic to humans.

                    The questions should always be -- (1) what are the potential toxic effects, (2) what's the risk of exposure, and (3) is the exposure level high enough to warrant concern? A final question is (4) what's the risk level versus various other potential risks in your life. After all, one of the highest risks most people take is driving to work in the morning, but most people don't worry about it. But they often get on an airplane and say prayers.

                    All the data I've seen seems to indicate that the risks are exceedingly low for non-stick coatings under normal use, and still rather low even when used improperly. So, absent epidemiological data demonstrating actual health effects caused by teflon use (very hard to prove), you need to demonstrate not only that teflon has the potential to cause harm, but that under certain common kitchen conditions it will produce toxins at a high enough concentration that we should be concerned. Simply stating that a potential byproduct is dangerous isn't enough -- it has to be shown to manifest in high enough concentrations to be of concern.

                    I should also point out that while any bird data might be interesting, it doesn't necessarily tell us anything about humans. Study after study have demonstrated that tests on animals much closer to humans genetically often react very differently to substances.

                    I'm not at all saying one shouldn't be concerned about such things. But the world is not just full of people from DuPont -- there are many, many other scientists in the world, and if teflon were a major threat, they could easily prove it. This is not proof of anything, of course, but it's not like this is a new substance or that concerns haven't been raised about its potential hazards for decades. Any research scientist who could prove danger here would be guaranteed to get his/her research plastered on the front page of most periodicals, which would probably lead to lots of grant money, tenure, maybe even a book deal if the story were interesting.

                    I find it hard to believe that DuPont's reach is powerful enough to stop *that*.

                    1. re: athanasius

                      athanasius: Thanks. I see what you mean about the links, but if you Google asanltr.com and PTFE, you will see the third article and that the link I pasted is correct.

                      Considering what we all thought we "knew" about Bisphenol A and pthalates a few years ago, I think we should be highly skeptical of what we think we "know" now about PTFE, PFOA and PFIB.

                      1. re: kaleokahu

                        "Considering what we all thought we 'knew' about Bisphenol A and pthalates a few years ago, I think we should be highly skeptical of what we think we 'know' now about PTFE, PFOA and PFIB."

                        See, to me, this is not a strong argument. We don't seem to "know" much more about BPA today that we did a few years ago. The European Food Safety Authority just ruled a couple weeks ago that recent studies do not constitute a reason to change the acceptable toxicological limits on BPA. Various watchdog groups have agreed with this decision. Scientists seem to be divided on whether it actually constitutes a significant risk.

                        Meanwhile, politicians, the media, and various lobbying groups have been pushing strong agendas leading to, for example, the recent ban in Canada.

                        And, of course, I've seen almost no discussion in all of this about the many, many similar compounds, which appear to have related effects. BPA is an endocrine disruptor, a xenoestrogen, but chemically similar phytoestrogens, which are naturally occurring in food sources from many plants and animals are also know to be endocrine disruptors or to mess with the endocrine system. (Some studies have claimed phytoestrogens have positive health effects, others claim they are problematic, leading to recent concerns about soy in baby formula, and possibie fertility effects, among other things. Since these chemicals are "natural," they haven't received as much attention.)

                        As I said for teflon, the issue is not whether a substance is toxic -- ALL substances are at some level. The question is whether exposure levels are high enough to be of concern. But we should also consider whether the effects are a significant risk factor compared to other risks -- and, so far, I haven't seen any scientific consensus emerge that makes BPA worse than any number of naturally occurring similar chemicals that we eat or are exposed to as well.

                        Of course, we don't have the whole story yet. Perhaps a consensus will emerge, and BPA will actually be banned by most countries. Given the history of chemophobia and media hype over the past few decades, however, I'd bet most manufacturers will simply give in, change their plastics, and then five years from now studies will show that BPA isn't that much of a concern after all. But no one will be paying attention by then. This might be the exception, but that's a general pattern for many chemical scares.

                        I personally wouldn't trust media hype as the primary source for scientific findings. One group of advertisers tries to sell you bottles to make money; then the media tries to sell newspapers by scaring people. The fact that scientific bodies seem to be going more slowly with this seems to indicate it's not as big a concern as many think.

                        And so, given that the scientific world doesn't much seem to care about teflon these days, I'm not going to worry too much about that stuff either until something changes. (I only have two non-stick pans anyway, and they don't get much use.)

                        1. re: kaleokahu

                          To reiterate athanasius is what many people call acceptable risk. When a prescription drug goes on market, there are always some side effects. You put a multiple of 100 (X100 fold of minimum efficacious dose), and you will see some tox effects in the subjects. You lower that to X30 and you may still see very minimum effect giving you a NOAEL (no observable adverse effect level). You take that theraptic window and the potential risk, then weight that against the benefits from the prescription drugs.

                          1. re: Chemicalkinetics

                            Yes, as CK said, acceptable risk is part of it.

                            I also think we need to see risks in perspective. The original 1959 teflon study found that the fumes from normal cooking oils were more toxic than the fumes from overheated teflon pans, for example. I don't know if a new study would conclude the same thing, but that finding isn't surprising to me. Oils can break down into all sorts of nasty things when heated, particularly past their smoke point.

                            We encounter "dangerous" things everyday, many of them from apparently "natural" sources. It's really hard to evaluate risk, but I think it's good to avoid the assumption that new/artificial/manmade chemicals with long names necessarily are more risky than anything else. Sometimes they are; sometimes not. But they do seem to get disproportionate media attention these days.

                      2. re: kaleokahu

                        It's a "personal" thing, IMO. Like avoiding bare aluminum food-contact surfaces, or choosing not to use PAM.

                        I have no conspiracy theories to offer, nor reports to cite.

                        I have my own opinions, some of which were formed from observations made while working in a variety of R&D and manufacturing environments.

                        Polymers are wonderful things. Much of my career has been fueled by the knowledge, application & use of them.

                        But I still choose to limit the amount of comestible interaction in which they participate. :-)

                        1. re: Eiron

                          Eiron buddy,

                          What is your prefer cookware? It seems to be that you are not a big fan of Teflon and you may not like aluminum either. What do you like?

                          1. re: Chemicalkinetics

                            For the past two years (almost) my favorite has been my All-Clad Copper Core 10" omelette pan. But part of that is fueled by the construction of the pan, & part by the US-made product. (I have a Calphalon Tri-Ply pan that cost 1/5 as much & works nearly identical, but I don't enjoy using it nearly as much due to its country of origin.)
                            (Yes, shallow of me, I know.)

                            Right now I'm thinking of buying a solid copper pan of some sort.

                            And, actually, I opted for polymers over aluminum when we got our KitchenAid mixer. We ended up with the "burnished" (raw aluminum) beaters rather than the epoxy-coated ones, so I decided to coat them myself.
                            But that's another story....

                        2. re: kaleokahu

                          "PTFE is found on a lot of cookware that goes--intentionally--to surface temperatures 500F and above--skillets, fry pans"

                          True, but then I feel like other manufacturers do not the same thing, not just PTFE/Teflon cookware companies.

                          I think companies just constantly try to expand the market. It really isn't the companies duty to make the best cookware for you really. It is their jobs to provide what you will buy or what you want to buy. Some people is going to have an excellent experience with Le Creuset Dutch Oven, and suddenly they want to learn to stir fry and say "I want a Le Creuset enameled cast iron wok."

                          http://www.amazon.com/Creuset-Enamele...

                          An enameled heavy cast iron wok really does not make sense to me. However, Le Creuset is not going turn these customers away as long as they are willing to pay for the goods.

                          Same for these Teflon/PTFE manufactureres. People want to buy these Teflon skillets, Teflon frying pans, ....or even Teflon woks. Like Caroline said, Teflon and wok seem like a bad combination.

                          1. re: Chemicalkinetics

                            Typo. When I typed "I feel like other manufacturers do not the same thing", I mean "I feel like other manufacturers do the same thing" -- minus the "not"

                          2. re: kaleokahu

                            Here's my experience (will be bo-o-oring; you've been warned!):

                            1) Several years ago I was working in the disk drive business, on the R&D side. We were using PTFE sealing gaskets on the housings. We chose PTFE due to its inherent inert-ness. That is, it didn't break down or off-gas anything that might contaminate the pristine disk surface.

                            As we pushed storage rates higher, we had to get the read/write heads closer to the surface of the disk. Once we got the disk surfaces flat enough to not strike irregularities with the r/w heads, we started having contamination issues. It turned out that the PTFE gaskets were "shedding" minute clusters of PTFE molecules. Since the PTFE was relatively soft, it was getting smeared onto the disks by the now very low r/w heads.

                            These gaskets shouldn't have been shedding anything, but Teflon soon bacame a banned substance for all of the major disk drive manufacturers.

                            2) I bought some DuPont Teflon Bicycle Grease. This was a short-lived product available in the mid-'90s. It is 100% Teflon, chained in such a manner as to become flow-able. It contains absolutely no fillers or solvents.

                            Curiously, the containers say to wash your hands before smoking. Nobody could explain this to me until.....

                            3) I went to work for a custom polymer bearing & seal manufacturer, working as a manufacturing engineer. The majorty of our products were PTFE-based. We bought our own powders, blended them, pressure-molded them, then sintered (cooked) them in giant walk-in ovens to melt the powder into a single shape (usually a tube or rod).

                            The ovens heated the PTFE alloys to 700F, turning it to a gel-like state before cooling down. They all had massive exhaust systems to vent the gases out of the building. Still, you couldn't open the ovens before they dropped below 200F. The by-products created by the sintering temps would give you "Teflon Flu." (Thus the reason for not smoking after handling Teflon grease.)

                            Obviously, "less than 200F" is well below the stated safe-use temp of 500F. But the parts would continue to generate by-products until they were completely cool. And those workers who got impatient with the cooling times (we were always under short deadlines) & opened the doors at 350F would suffer the results & be out sick for the next few days.

                            --------------

                            I readily admit that these examples are not directly applicable to our use of Teflon-coated cooking pans. I'm only presenting them as first-hand experiences that have biased my view of continued intimate contact with this particular material.

                            We've been told Teflon's food-contact-safe under lab-tested conditions. That it's inert, non-reactive. Yet, we watch it change color, "dry out" & flake off of our pans with little more than a wonder as to why. Given enough time, sun, heat & chemicals will degrade every polymer. It's not a "permanent" material by any means. It's not a "natural" material, either. It's synthesized. Not refined; built. It's the deconstruction of the material that concerns me.

                            1. re: Eiron

                              Eiron -

                              Thanks so much for your experiences here. It's very interesting. Some questions on your stories:

                              (1) Yes, but PTFE by itself is relatively inert, no? (Maybe an issue for hard drives, but for humans?)

                              (3) Is it possible that some chemical changes happened or some serious off-gassing occurred when heating to 700F that would not have happened had you simply raised the temperature to 500F *only* and then cooled it down? It strikes me that going past the "safe" point by 200 degrees could change the material in ways that would then make it less safe, even below the previously safe limit. Or do you think that unlikely?

                              I'm just curious here, since I have nowhere near this much first-hand experience with telfon products and processing.

                              1. re: athanasius

                                athanasius,

                                1) Yes, PTFE is considered to be perhaps the most inert polymer. It is used extensively in medical applications because of this (Gore Labs has an entire medical division). Many industries specify PTFE liquid transport tubing when they want to insure zero contamination to their liquids.

                                My concern in this case was that the polymer was observed migrating when it shouldn't have. As I mentioned in an earlier post in this thread, I have a Teflon mesh patch inside of me, used to repair a separated muscle wall. When operating correctly, the human body is very efficient (& relentless) at using whatever it's given. I'm not concerned about any definition of "poisoning" created by this material, but I do wonder if my body's being very successful at breaking this material down.

                                3) Possibly, yes. We had to heat the compressed PTFE powder to this temp to get it to fuse (melt) into a homogenous polymer body. (I was told by others that the PTFE would not liquify at this temp, but would become gel-like, glowing & translucent. The ovens had rotating drums inside to keep the tubes & rods continuously rolling so that they wouldn't flatten out when they turned to gel.) We never ran it at lower temps because it wouldn't fuse at that point.

                                My concern here was that this was a controlled process defined by the plastics industry to meet US & European worker safety guidelines. (We'll ignore the acceptance to vent to atmoshphere outside of the building.) If anyone should have the experience & knowledge of how a polymer will react under standard processing practices, it SHOULD be the producers of the polymer. At 300F or 350F, the polymer alloy met the temperature safety guidelines we're talking about here. But it still created problems for the people in closest contact with it.

                                I suppose it's not too surprising that when an oven was opened "early," workers would stay out of that area for several hours (if possible). Unfortunately, users of manufacturing processes tend to figure out the problems of those processes before the providers do. I've seen similar worker adaptation in machining, injection molding, electronics manufacturing, etc.

                                Again, let me say that I realize my personal experiences with PTFE have little in common with what we're discussing here. I do feel less concern about my Teflon pans now that we've been allowed to discuss it. But I think your earlier analogy to the "canary in the coal mine" is valid when it comes these types of questions. I think there may well be cumulative effects of these (& other) compounds that we have no way of detecting at this time.

                              2. re: Eiron

                                Eiron:

                                Thank you so much for this promised post. I actually was hoping that it would allay my fears and suspicions. Unfortunately, it causes even more unease. If fresh nonstick cookwear is off-gassing whatever causes "Teflon flu" at 200F, consumers are not getting the whole story, and environmental, health and safety regimes are cynical jokes.

                                And if these compounds (5-year bioactive half-life, athanasius?) are being vented to atmosphere outside all the world's PTFE manufacturing and coating plants, God Help Us All.--I'm not even religious.

                                1. re: kaleokahu

                                  Kaleo -

                                  "If fresh nonstick cookwear is off-gassing whatever causes "Teflon flu" at 200F, consumers are not getting the whole story"

                                  I'm not sure the comparison is correct here -- Eiron is talking about beginning with raw PTFE powder. Also, we have to consider that this powder is turned into a goo, which is then cooled and formed. I didn't get the sense that he was talking about cookware here. Gases may take some time to travel out of a viscous substance, so perhaps part of what's going on here is that the PTFE was heated above the 500F limit significantly, produced some bad things, but those bad things hadn't actually exited the goo completely until it had cooled to around 200F. Perhaps it if had stayed in the oven longer at, say, 400-500F, all of that stuff would have had time to migrate out, and it would be safe in the 200-500 range?

                                  I don't know the details of the processing, and I'm speculating, but the fact is that this PTFE was taken WAY above the suggested range for cooking materials BEFORE it apparently produced these byproducts, at least if I am hearing Eiron correctly.

                                  "5-year bioactive half-life"

                                  Just to be clear -- that was the stated approximate half-life of PFOA in the human body. That is to say, if you had a one-time exposure, after 5 years you'd expect that half of it would be excreted from your body. After 10 years, you'd have only 25% left, etc. That's not to say that PFOA degrades or becomes inactive at that time, only that it is excreted from the body. (I admittedly don't know the details here -- I'm just clarifying what the number was that I had stated earlier.)

                                  As for environmental concerns, those may very well be significant. I don't know. That hasn't been the subject of this thread. I don't think the use of cookware is something to worry about in terms of exposure, but pollution of various hazardous materials from their manufacture is a separate topic.

                                  1. re: athanasius

                                    Actually, to be completely correct, the powder is compressed into a solid (either a tube or a rod) in dimensions close to what is desired in the finished product. This compressed form is referred to as "green" material & is not structually robust. During sintering, the material turns gelatinous but does not ooze or flow because it is kept "rolling" inside the chambers of the ovens' internal turning drums.

                                    A nit to pick, to be sure, (now THAT'S an unpleasant image to create on a food board, isn't it?,) but just wanted everyone to have the correct idea of what's happening during processing.

                                    And no, I'm definitely NOT talking about cookware production. This was at a bearings & seals manufacturer.

                                    1. re: Eiron

                                      Thanks for the clarification. It's good to understand the process you were talking about.

                                      But regardless, for gases evolved in a gelatinous material during processing, it could require some time for them to out-gas, which was my primary speculation. From my perspective (correct me if I'm wrong), the situation you describe does not necessarily imply continued production of hazardous gases at 200F, since the hazards could have been produced during the high temperature processing but took some time to exit the material. The question for me is -- if you kept the material at, say, 450F for a while after the high-temp processing, instead of letting it continue to cool (hopefully allowing any hazardous gases to dissipate), would you still see bad things when it got down to 200-350F or whatever?

                                      You may not know the answer, but it seems to me that would be important to test before assuming that PTFE would still produce nasty stuff at lower temperatures.

                                      1. re: athanasius

                                        I hope I'm interpreting your question correctly:

                                        Yes, actually, the sintering process includes a lengthy "cool down" period of stepped temps held for specific lengths of time. This is precisely for the reasons you mention, of allowing gases to migrate out of the gel-state polymer alloy. If allowed to cool too quickly, the gases become trapped inside the fused plastic & create micro-bubbles & weak spots.

                                        It's been two years since I've worked with any of the sintering temperature profiles, so I'm not able to recall specific temp hold points or durations for you. I do recall that the cool down might be three or four times as long as the ramp up to fusing temp. Also, some of the sintering programs might run as long as 18 hrs. It changed depending on the alloy being processed.

                                        1. re: Eiron

                                          "cool down might be three or four times as long as the ramp up to fusing temp"

                                          That is normal, no? I presume this cool down period may also serve as an annealing process, or is it just cool down?

                                  2. re: kaleokahu

                                    I didn't reply earlier, but I wasn't sure if Eiron meant 200°F or if he actually meant 200°C and I just assumed he ment °C. 200°F wont even get you to boiling and all the studies I read through were quite clear that nothing is going to happen at that low of a temperature. From a chemistry stand point, molecules of plastic materials don't have freedom to move at temperatures below their Tg (glass transitiion temperature) and the Tg for PTFE is about 250°F. I assumed this was a typo. However rereading the post again, it's clear that it is 200°F, however, he is talking about a sealed oven that when opened releases the noxious fumes, but that oven had been up to 700°F for an extended period of time. Naturally when the oven door is opened the gasses are going to excape, there is nowhere else for them to go, they're not going back into the material at that point.

                                    I think this is an example of how carefully we need to read these technical posts to make sure we actually understand what is being posted.

                                    1. re: mikie

                                      mikie: "I think this is an example of how carefully we need to read these technical posts to make sure we actually understand what is being posted."

                                      Yep, totally agree. I generally understand the theories why PTFE SHOULDN'T be offgassing, degrading, etc., within cooking temperature ranges (and above for a safety margin). Whether or not it IS offgassing is the question, and I'm not going to err on the side of being trusting.

                                      athanasius: "As for environmental concerns, those may very well be significant. I don't know. That hasn't been the subject of this thread."

                                      Well, then, the PFOA "models" (showing <1% exposure from cookware) are wildly skewed, aren't they, if they do not account for MANUFACTURE and APPLICATION of PTFE in cookware? I mean, if Eiron's anecdotal info is not the exception (just visualize: Far East+jetstream), then PTFE cookware MAY be poisoning us all, just not directly from our own pans in our own kitchens! In this view, they would have already have done their damage before the FedEx courier drops them off. Wouldn't it be ironic if we were breathing the PFOA from our pans before we ever received them?

                                      1. re: kaleokahu

                                        "Well, then, the PFOA 'models' (showing <1% exposure from cookware) are wildly skewed, aren't they, if they do not account for MANUFACTURE and APPLICATION of PTFE in cookware?"

                                        The study was not "wildly skewed." Scientific studies have particular goals and methodologies. What you're proposing is not part of the study.

                                        You have to take the context of the study. It was trying to determine and model the *mechanisms* by which PFOA gets into the human body. It was not trying to evaluate the ultimate sources of PFOA, only the proximate sources that conveyed the PFOA to our bodies. Is industrial manufacture of PTFE cookware a significant source of PFOA in the environment? You'd have to check into the various uses of PFOA, how much leaks out from those uses during manufacture, how much leaks out in landfills after stuff is discarded, etc. Given the huge amount of applications for PFOA on carpets, textiles, sealants, etc., I would seriously doubt that non-stick cookware is responsible for more than a few percent of environmental PFOA.

                                        I don't know, but that's a whole separate question from whether you're going to get sick from using PTFE in your kitchen (or breathing in vapors produced in your neighbor's kitchen or whatever).

                                        1. re: athanasius

                                          athasius: You're right about it being a different question, although Eiron's point might well as be that my OP was too narrow a question.

                                          My point was that, if we're told that <1% of the PFOA we get comes from MIGRATION INTO FOOD from cookware, and it turns out that 20% (I'm making this number up) of the TOTAL ingested share comes from the share of PTFE made and applied that is put on the cookware, then the numbers are wildly skewed when it comes to the overall health aspects of PTFE in nonstick. Even if the latter number is 1% of all inputs, it amounts to an error greater than a factor of 2 in considering cookware.

                                          Is there a study that attempts to quantify the % of ingested PFOA that is NOT attributable to PTFE manufacture? If there are no other predominant chemical precursors, isn't a lion' s share ingested (by whatever mechanism) linked to PTFE?
                                          (I'm not going to make the Blood Diamond analogy)

                                          1. re: kaleokahu

                                            "Is there a study that attempts to quantify the % of ingested PFOA that is NOT attributable to PTFE manufacture?"

                                            Be careful here -- you're bringing up a separate question. This is a thread about cookware. Teflon has many applications other than non-stick cookware. Are you trying to associate ALL manufacturers of PTFE-related products with non-stick cookware?

                                            To answer your question about other studies, yes, there are dozens of studies done over the past decade on environmental levels, probable sources, degradation, etc. of PFOA and related compounds. I honestly don't have time to dig through them.

                                            "If there are no other predominant chemical precursors"

                                            PFOA is used in the manufacture of a number of fluoropolymers, as I understand it. So you can't link it all to PTFE specifically. Again, I don't have the numbers.

                                            Anyhow, even if we could narrow down the manufacturing numbers, we still have the issue of waste sources, which could be even more significant. Most of PFOA is destroyed in manufacturing plants before being released to the environment. This is particularly true of cookware, where the products are deliberately processed in such a way that as much PFOA is off-gassed as possible, collected, and processed.

                                            For other consumer products containing PFOA or teflon, however, there is not as much concern, since it has a lesser tendency to be released during use, since most of these products are not heated. That means there is a LOT more latent PFOA in other products -- including other teflon products -- than in cookware (as numerous studies have shown).

                                            When those products are dumped into landfills, the PFOA will gradually leach out over time, and will not be processed and chemically destroyed as is deliberately done in the manufacture of teflon cookware.

                                            So, again, for all these reasons, I think it's exceedingly likely that teflon cookware contributes a small fraction to environmental PFOA pollution.

                                            1. re: athanasius

                                              athanasius: All good questions beget more, I guess. If someone started a line of spent uranium cookware, 99.999% of uranium went into munitions, and there was "scant" epidemiological evidence of adverse health effects, should we just shrug it off?

                                              I did not know that "most of the PFOA is destroyed" or "collected" by cookware manufacturers. Where did you learn this?

                                              This just in (2005) : "DUPONT WORKERS UNION CALLS TOXIN REDUCTIONS TOO LITTLE, TOO LATE- Union officials for workers at DuPont are calling a plan by the company to reduce toxic chemicals in their teflon products, "too little, too late." PACE is calling for full disclosure from the company concerning dangers of working with and using products that incorporate a chemical called C8. A judge in West Virginia recently approved a $107 million settlement against DuPont on behalf of residents who had their drinking water allegedly poisoned by the chemical." http://www.laborradio.org/node/116

                                              1. re: kaleokahu

                                                "If someone started a line of spent uranium cookware, 99.999% of went into munitions, and there was "scant" epidemiological evidence of adverse health effects, should we just shrug it off?"

                                                No, we shouldn't shrug it off. You were concerned that one of the studies we discussed earlier didn't consider manufacturing emissions that might ultimately end up in humans. You then wondered if we were being "poisoned" by cookware indirectly through those emissions.

                                                What I'm saying is that if indeed PFOA is a poison, and even if, indeed PTFE manufacture is the primary source of that poison, that still doesn't mean that we should conclude that non-stick *cookware* (even in manufacture) is the primary concern or source for that poison entering our bodies, which I believe was the question you wished the study had answered, no?

                                                I'm not saying we should shrug anything off. We can discuss PTFE and PFOA and lots of other chemicals, but let's stay on topic -- this is about cookware. Even if these chemicals are a concern, *cookware* -- manufacturing, use, etc. -- is not a significant source of these chemicals compared to other things.

                                                "I did not know that 'most of the PFOA is destroyed' or 'collected' by cookware manufacturers. Where did you learn this?"

                                                Gosh, I've been skimming so many articles lately, I can't remember, and I can't find it again right now. But I'm not making it up. As Mikie mentioned, usually there are emissions limits, so companies can't just vent all this stuff into the environment. I think I read this on the EPA website, where they were discussing the reduction of emissions... I thought I recalled some number saying that only roughly 30-35% of PFOA used in manufacturing was actually released into the environment, while the rest was destroyed. I believe this was before the major EPA initiative, which is trying to cut year 2000 emissions by 95% by 2015. Now, major US companies are recycling or destroying something like 90% of PFOA used in manufacturing.

                                                I will repeat what I've said a few times already -- there are probably hundreds of other chemicals in common every day consumer products with proven health effects of greater concern that no one is paying attention to. I'm not saying that excuses any possible health concerns for non-stick cookware, but if you're actually looking to protect your health, I think there are much bigger things to worry about.

                                                1. re: athanasius

                                                  athanasius: Well, we're either on-thread or off-thread. PTFE and its manufacturing adjuncts--like PFOA and C8(?)-- have to be made before they can be put on cookware. Some share of that obviously goes where it's put. And to where it wears, decomposes and off-gasses. And to where it's wasted/recycled. Where, according to one of the studies you quoted, it (at least the PFOA) stays FOREVER.

                                                  Good thing the human body gets rid of it in 3 (or 5, or wait for the next study) years, because we have to make room for all of it that is waiting its turn.

                                                  "Only" 35% of PFOA gets into the environment? Dang, the CEs must be working in shifts at DuPont.

                                        2. re: kaleokahu

                                          By the way, just so it's clear what we're talking about, below is a section from the latest summary of epidemiological studies on PFOA, "Epidemiologic Evidence on the Health Effects of Perfluorooctanoic Acid (PFOA)," published in Environmental Health Perspectives (2010).

                                          Basically, it sounds to me like the only firm conclusions are that it increases cholesterol and uric acid production slightly, but this was only observed in occupational studies from workers at plants using the stuff in manufacturing, who were obviously at a much higher risk of exposure than the general public. The findings about tumors in rodents are made problematic because the half-life is a lot different in their bodies (for some reason) -- not to mention that the exposure level was orders of magnitude higher than observed in humans -- and there are other compatibility problems greater than seen in many animal studies.

                                          I'm not saying we should declare the stuff "safe," but serious detrimental health effects are far from proven.

                                          From the abstract:
                                          --------
                                          PFOA does not break down in the environment; the human half-life is estimated at about 3 years. PFOA is not metabolized in the body; it is not lipophilic. PFOA is not directly genotoxic; animal data indicate that it can cause several types of tumors and neonatal death and may have toxic effects on the immune, liver, and endocrine systems. Data on the human health effects of PFOA are sparse. There is relatively consistent evidence of modest positive associations with cholesterol and uric acid, although the magnitude of the cholesterol effect is inconsistent across different exposure levels. There is some but much less consistent evidence of a modest positive correlation with liver enzymes. Most findings come from cross-sectional studies, limiting conclusions. Two occupational cohort studies do not provide consistent evidence for chronic disease; both are limited by sample size and reliance on mortality data. Reproductive data have increased recently but are inconsistent, and any observed adverse effects are modest.
                                          Conclusions
                                          Epidemiologic evidence remains limited, and to date data are insufficient to draw firm conclusions regarding the role of PFOA for any of the diseases of concern.
                                          -----------------

                                          1. re: athanasius

                                            athansius: OK, I get it: "Data on the human health effects of PFOA are sparse." Maybe we'll get published, peer reviewed answers to something like my OP in the next 72 years of PTFE. Because I guarantee you: if DuPont and 3M (nevermind the rest of the world) can get away with it, this stuff will be made well past the "agreed" 2015 cutoff.

                                            Also nice to know it does NOT break down in the environment. Perfect. We should look for it on Mars!

                                            If you're posting trying to help me feel better, please stop. LOL

                                            1. re: kaleokahu

                                              "Also nice to know it does NOT break down in the environment. Perfect. We should look for it on Mars!"

                                              Actually, contrary to this study (which was primarily about medical effects, so I wouldn't count on its claims about environmental science), the environmental studies I briefly looked at suggested that PFOA does degrade into other things over time... whether those things are significantly better, I don't know.

                                        3. re: mikie

                                          OK, now I'm confused!

                                          In my first report I stated, "They [the ovens] all had massive exhaust systems to vent the gases out of the building."

                                          In my second report I stated, "We'll ignore the acceptance to vent [the ovens] to atmoshphere outside of the building."

                                          I thought I was being relatively clear that the fumes were not collected & contained inside the sintering ovens. Sorry for the confusion. (I think?)

                                          1. re: Eiron

                                            Hey, it's your post, it's got to be me that's confused. I do remember reading "We'll ignore the acceptance to vent to the atmosphere outside the building" but I guess I didn't tie that to the ovens. I even went back and reread and still didn't make the connection. I suppose the oven could have cooled but the polymer is still hot, or it's some kind of residual effect. Or maybe the vent is pluged with PFOA, not sure why there would be that much gas at that temperature if it were being vented during the process.

                                            I use PTFE in one of my products, but we process at about 280°C so we're below the melting point and not much is happening below about 380°C, so I don't have to deal with these issues.

                                            How this applies to cookware, I'm not sure. But it certianly applies to the environment both inside the building and outside. Manufacturing plants that vent to atmosphere have to get permits from the state, or at least our plants do. What state was this in? I'm not going back to find the numbers, but there are restrictions on how much of a chemical can be vented safely.

                                            kaleokahu, whether it's PFOA or not, we're already breathing whatever comes out of smoke stacks in China regardless of whether or not you buy something, you don't even need FedEx.

                                2. Well.....

                                  I know what the Plastics Books say, & what the medical community says (mikie has recapped the info very well, & I even have a Teflon mesh patch inside me).

                                  What I have NOT seen is any kind of long-term "practical use" study that subjects the material to accelerated aging via repetitive heating, abrasion & oil/acid/base immersion, then analyzes the material's reaction & resulting composition.

                                  I also know what sort of precautions we had to take into account when working with PTFE in a manufacturing environment. And I've seen the problems created when those precautions were circumvented.

                                  How many of us were absolutely positive that Nalgene Scientific Labware polycarbonate drinking bottles were 100% safe? Up until 4 or 5 yrs ago, I think all of us were.

                                  PTFE is relatively soft. It gets damaged easily. It degrades. It changes color. It comes off. We've all seen it occur in our own kitchens.

                                  PTFE is, perhaps, the most inert plastic compound commonly used in a cooking environment. Does that make it safe to use?

                                  That's a decision we each have to make, based on our level of comfort using the product.

                                  13 Replies
                                  1. re: Eiron

                                    "What I have NOT seen is any kind of long-term "practical use" study that subjects the material to accelerated aging via repetitive heating, abrasion & oil/acid/base immersion, then analyzes the material's reaction & resulting composition."

                                    That is a very tough study because (1) it is difficult to have control group, and (2) it will be a very expensive study.

                                    1. re: Chemicalkinetics

                                      I'm not looking for a control group type of study. I'm looking for an accelerated life test.

                                      Heat, abrasion, chemicals (oil/acid/base). The parameters are known & can be recreated/applied in a repeatable manner. The variables can be changed one-at-a-time & the results recorded.

                                      It's a tedious process (I've had to do it many times myself), but it's not all that complicated.

                                      1. re: Eiron

                                        Hi Eiron,

                                        You want a 'long-term "practical use" study ' that sound to me that you are looking for chronic problems than acute problems, right? Now, if you are looking for the effect of Teflon on human subjects, say over 10 years, it will be difficult to do without a control group. You will need to select two groups of people and the two groups will be selected based on age, sex, weight, health history.. etc.. you cannot have one group comprised of overweight people, and one group comprised of thin people, or one group has diabetic history in the family and the other group does not. The two groups have to be similar. Then you need one group to promise to only use Teflon in this 10 years peroid and the other group promise to never use Teflon in this 10 years.

                                        I think a clinical life study is very complicated and expensive.

                                        1. re: Chemicalkinetics

                                          CK: Eiron can speak for himself, but I don't think he even means ANY epidemiology. I think he means physical tests of the cookware itself. Scratch, test. Abrade, test. Acid, test. Base, test. Heat, test. If you're getting degradation products, identify and quantify. That sort of thing.

                                            1. re: Chemicalkinetics

                                              CK: I just clued myself in on LOL and winks, so excuse a silly question: Was ist das ":P"?

                                              1. re: kaleokahu

                                                Hi Kaleo,

                                                Smiley face :)
                                                Laughing :D
                                                Sticking my tongue at you :P

                                                Heh hehe.

                                            2. re: kaleokahu

                                              Yes. Unless I'm very much mistaken, the original "safe-to-use" tests were physical tests of the coating, not clinical tests of any users/subjects.

                                              I'm suggesting aging/degradation/decomposition testing of the coating. Accelerated life tests are pretty standard across multiple industries. Of course, the results can always be skewed to favor a particular outcome, so a disinterested third party reviewer is sometimes included in the process.

                                              The difficult part would be developing a set of application procedures for the known parameters that would provide meaningful results to the end-users. There would have to be a fairly complex matrix of parameters, IMO.

                                              Testing after each single parameter is only the starting point. You then have to combine parameters in different ways & measure THOSE results. And don't forget that it's an AGING test. So the test combinations need to be repeated several times over the course of the accelerated aging process.

                                              Like I said, it's a tedious process.

                                          1. re: Eiron

                                            You mean something like this?

                                            http://www.consumerreports.org/cro/ho...

                                            It doesn't sound like a very detailed study, but it seems to imply that the small levels of PFOA observed tend to become almost undetectable after a few months of use.

                                            Of course, it's not a substitute for a proper scientific study. I'll look around for one....

                                            1. re: athanasius

                                              Thanks, athanasius. This sounds promising. When was this done and can we access the actual reports and data? It's odd there're no citations and that the lab isn't identified.

                                              1. re: kaleokahu

                                                This is typical for Consumer Reports -- it's a magazine, not a scientific journal. But it usually does have the public's best interest in mind.

                                                You might not buy it, but here's a study done by DuPont scientists published in the peer-reviewed journal The Analyst (the journal of the Royal Society for Chemistry):

                                                http://www.rsc.org/delivery/_ArticleL...

                                                The abstract:

                                                -----------
                                                Salts of pentadecafluorooctanoic acid (PFOA) are polymerization aids used in the manufacture of fluoropolymers; one of the applications of fluoropolymers is the coating of metal cookware products. A method was developed to determine if PFOA might be present in and extracted from the surface of commercial frying pans coated with a DuPont fluoropolymer under simulated cooking conditions. Commercial grade cookware was obtained, then extracted with water and ethanol/water mixtures at 100 and 125 °C, and the resulting extracts were analyzed by liquid chromatography tandem mass spectrometry (LC/MS/MS). Detection and quantification limits as low as 100 pg cm−2 were demonstrated. None of the fluoropolymer treated cookware samples analyzed showed detectable levels of PFOA when extracted under simulated cooking conditions.
                                                ---------------

                                                In other words, they followed the advice of a previous study and used water and ethanol/water mixtures as recommended to try to extract as much PFOA as they could. They basically got so little that they couldn't differentiate their findings from background noise.

                                                Basically, they boiled teflon in good solvents for a while, and no PFOA leached out. Admittedly, the study doesn't cover high temperature issues.

                                                Another study from the journal Food Additives & Contaminants (2007):
                                                http://www.ncbi.nlm.nih.gov/pubmed/17...

                                                Abstract:
                                                -----------
                                                Twenty-six non-stick-coated cookware samples were purchased, covering a variety of products, coating/metal types and food contact applications. The polymer coatings were identified to be polyethersulphone, polytetrafluoroethylene (PTFE), bisphenol A/epichlorohydrin and one coating for which no good match was obtained with infra-red library spectra. All of the products intended for stove-top use had a polymer coating containing PTFE. The coatings were analysed as purchased and after heating at 250°C for 30 min to simulate actual conditions of use. Total solvent extractables were measured and the overall migration was determined into simulants. None of the products exceeded an overall migration limit of 10 mg dm-2. Coating materials were analysed by headspace gas chromatography-mass spectrometry (GC-MS), by liquid extraction followed by GC-MS and by liquid extraction followed by liquid chromatography-mass spectroscopy with a particle-beam interface. Benzene was detected in two samples, at 1.4 and 2.4 µg dm-2. These levels in the coatings are too low to give any detectable migration into foods. There was no detectable release of perfluorochemicals. Several other substances were identified and the worst-case migration was calculated. The origin of many of the substances detected was considered to be by pick-up from the printed packaging materials in which the cookware was sold. Potential consumer exposure was calculated. None of the substances identified had the potential to exceed their tolerable daily intake (TDI) value. To confirm these worst-case calculations, the migration of certain phthalates and of bisphenol A was measured into food simulants. Migration levels were very low.
                                                -------------------

                                                The researchers here had no connection to DuPont, or any other business -- they appear to be part of an environmental group in the UK, as far as I can tell.

                                                Among studies that found something, here's one from the same journal in 2005:

                                                http://www.ncbi.nlm.nih.gov/pubmed/16...

                                                From the abstract:
                                                ------------------
                                                Results from migration tests show mg kg-1 amounts of perfluoro paper additives/coatings transfer to food oil. Analysis of PTFE cookware shows residual amounts of PFOA in the low µg kg-1 range. PFOA is present in microwave popcorn bag paper at amounts as high as 300 µg kg-1.
                                                ----------------

                                                (The microwave popcorn thing is on-going in some of these articles... as you probably know, it's a much more significant source for these chemicals.

                                                )

                                                This study explicitly studied off-gassing from the journal Environmental Science Technology (2007):
                                                http://www.ncbi.nlm.nih.gov/pubmed/17...

                                                From the abstract:
                                                ----------
                                                In this study, we identified and measured perfluoroalkyl carboxylates (PFCAs), particularly PFOA, and fluorotelomer alcohols (FTOHs; 6:2 FTOH and 8:2 FTOH), released from nonstick cookware into the gas phase under normal cooking temperatures (179 to 233 °C surface temperature). PFOA was released into the gas phase at 7−337 ng (11−503 pg/cm2) per pan from four brands of nonstick frying pans. 6:2 FTOH and 8:2 FTOH were found in the gas phase of four brands of frying pans, and the sources of FTOHs released from nonstick cookware are under investigation. We observed a significant decrease in gas-phase PFOA following repeated use of one brand of pan, whereas the other brand did not show a significant reduction in PFOA release following multiple uses. PFOA was found at >5 ng during the fourth use of both brands of pans. FTOHs were not found after the second use of either brand of pans.
                                                --------------

                                                From the conclusion:
                                                -------------
                                                Our results provide evidence that residual PFOA is not completely vaporized during the fabrication process of nonstick coatings. Although in one sample the mass of off-gassed PFOA released was observed to decrease following multiple uses, PFOA was measurable in the gas phase on the fourth use of both brands of frying pans. Further analysis is needed to determine whether cookware represents a continuous source of exposure to PFOA.
                                                -----------------

                                                Basically, to sum up, *some* studies are finding *something*. The study with the worst evidence just says that there is PFOA released in gas, but we don't know whether it's a major consumer exposure risk or how long the stuff will come out of pans.

                                                I don't know... this is what I expected. A bunch of scientific journals with contradictory results. None of them seem to indicate a cause for great concern, though some warrant further investigation.

                                                1. re: athanasius

                                                  athanasius: Wow! Thanks for all the effort. I wish I could read the studies in full.

                                                  I'm sure reasonable minds will differ, but I'm concluding the most honest answer to my OP is "We don't know." Depending on our predilictions and philosophies about our health and environment, maybe that's enough to make a good decision. It is for me. For now.

                                                  1. re: kaleokahu

                                                    No prob, kaleokahu.

                                                    Your inquiring mind made me want to go searching. There are probably more recent relevant studies out there, but I think this is at least a good sample.

                                                    I think the conclusion I'd draw from this is that I agree with you that "we don't know" for sure that there's no significant health risk. But the data seem to indicate that if there is a risk, it's probably relatively low, and if we are really concerned about these chemicals, there are probably much more significant sources to worry about.

                                                    But the thing is -- I would still encourage you to keep this in perspective. There are probably thousands of chemicals in all sorts of consumer goods that could potentially leach some toxic chemical into your skin or off-gas something potentially nasty at room temperature. And not all "artificial" or recently man-made manufactured stuff -- very traditional cleaning solvents used in the wrong way can produce pretty nasty things.

                                                    Teflon has been of concern because it comes in contact with food, and people are generally more worried about chemicals they might be eating/drinking. But I think if we're going to go down this road, we'd have to read up on every study on, say, all cleaning chemicals we use in our houses, all chemicals used to dye our clothes, etc.

                                                    I could very well be wrong about PFOA from teflon in particular, but I'd bet that there's a lot of other stuff out there (including supposedly "natural" stuff) that poses much greater risks, and we either haven't studied it in detail, or no one cares.