It appears that my cooking recommendations of suggesting that non-stick cookware is acceptable may need to be modified. This research makes it quite clear that one should not heat non-stick cookware to high temperatures.

My guess is that at lower temperatures it is not as serious an issue. I have used non-stick cookware prior to this study, but I will clearly revise my use based on this research.

Dr. Paul Connett was gracious to provide a commentary on this study and it is being posted below.

Comments from Paul Connett, PhD:

Polymer polytetrafluoroethylene (PTFE) is used in electrical insulating tape; combustion engines; chemical apparatus and tubing designed to resist attack from most chemicals, and in non-stick frying pans and other cookware.

Prior to this article there have been stories about caged birds dying in kitchens after fires involving non-stick cookware, suggesting the emissions of toxic gases when this polymer is burned.

This article is more serious because the researchers did not burn the non-stick coating but simply heated it. Presumably, typical cooking procedures would also heat the non-stick coating to the temperature range investigated by these researchers. Thus, this material that is perceived by most as being benign, could be a source of both significant indoor and outdoor air pollution.

This is another nasty indication that the world of organofluorine compounds could be going the same way as their more famous cousins: the organochlorine compounds. In the latter case most of these products, such as organochlorine pesticides, solvents and PVC plastic (despite the toxic generating manufacturing processes that produce them) were perceived as benign.

However, they had several problems:

• They tended to be very persistent in the environment
  

• They are fat soluble and resistent to normal detoxification processes in the liver
  

• They accumulate and concentrate in animal and human body fat,
  

• They get passed on by the mother to the fetus through the placental membrane and then to the infant via breastmilk,
  

• A number of them are endocrine disrupting chemicals (i.e. they interfere with the production or performance of hormones, which are the messengers produced in special glands to regulate body chemisty) To top it all, when these substances are burned in any facility ranging from a back yard burner to a trash incinerator, they produce highly toxic byproducts including dioxins and furans ( PCDDs and PCDFs).

Twelve of these compounds (or families of compounds) were the subject of the POPs (persistent organic pollutants) treaty signed in Stockholm last May by many countries around the world, including the US.

The bottom line is that nature doesn't make persistent things. Both in our bodies and in the environment, natural processes are constantly building up and breaking down all the chemical components used.

Nature attempts to protect itself from persistent fat soluble substances by converting them to water soluble substances, which can then be excreted through the kidney. If this strategy fails then they are stored in our fat. In the case of persistent (or permanent) water soluble substances like fluoride or lead, the body will excrete as much as it can through the kidney and what it can't ends up largely in our bones.

However, in the case of both fluoride and lead other more sensitive organs like the brain and pineal gland may also have mechanisms which allow their accumulation.

Returning to organofluorine compounds, it is also interesting to note that there are two forms of fluoride found in human plasma: free (or inorganic) fluoride and bound fluoride. According to Gary Whitford in his book, "The Metabolism and Toxicity of Fluoride" (Karger,1996), "perfluorooctanoic acid (PFOA, octanoic acid fully saturated with 15 fluorine atoms)...(constitutes) about 20-30% of the nonionic fluoride in human plasma.

This surface-active agent, which is a component of plasticizers, lubricants, wetting agents, emulsifiers and other products, appear to enter the body through contact with or ingestion of commercial products. It has a very long half-life (approx. 1.5 years) in human males (Ubel et al., 1980)". Thus the question raised by this new report in Nature is how many of the byproducts from heating PTFE are accumulating insidiously in our bodies like PFOA? Are any being passed onto the fetus? Will any of them turn out to be endocrine disrupters?

Paul Connett, PhD, is a Professor of Chemistry at St. Lawrence University, Canton, New York. He is also Director of the Fluoride Action Network, an international coalition dedicated to ending water fluoridation and alerting people to fluoride's health and environmental risks. Visit their website at www.fluoridealert.org.

Follow-Up Comment from Dr C. Vyvyan Howard, MB, ChB, PhD, FRCPath:

It seems that it may be even worse than Paul Connett has portrayed. When you heat PTFE up to the sort of temperatures that you get in "state of the art" municipal waste incinerators (eg, 800°C) you get the formation of CFCs, the major greenhouse gas that has been banned as a refrigerant. When one considers the amount of clothing and fabric that is coated with PTFE (most artificial fibres described as 'breathable') this could have major implications for waste incineration.

Another aspect of heating PTFE in cooking utensils is the following: A standard method of producing an aerosol of ultrafine particles is to heat PTFE up to 480°C. This produces some gas-phase products, mainly HF (hydrogen fluoride). If PTFE is further heated up to 500°C other gas-phase products are produced, including perfluoroisobutylene and others, which are highly toxic.

This is described in a paper by Obersdorster G, 'Toxicology of ultrafine particles: in vivo studies'. Trans. Phil. R. Soc. Lond. A (2000) 358: 2719-2740. The rest of that issue of Trans Phil is dedicated to ultrafine particles.

Ultrafine particles are defined as those below 0.1 microns (100nm) and it is being demostrated that these have a toxicity all of their own, which seems to be associated with their high chemical reactivity (that, after all, is how we make heterogeneous catalysts!). I have recently edited a book on this (Particulate Matter: properties and effects upon health. Eds R L Maynard and C V Howard. Bios, Oxford (1999). ISBN 185996172X (Sorry about the self advertising)).

However, it is appearing that the majority of the toxicity of particulate aerosols may be attributable to the ultra-fine fraction. This could have major implications for the use of non-stick cookware in the home and industry. I am not aware that the tie up between the routine use of these materials, ultrafine particle production and possible health effects has yet been made.

Dr C. Vyvyan Howard, MB, ChB, PhD, FRCPath,
Developmental Toxico-Pathology Group,
Mulberry Street,
University of Liverpool,
Liverpool L69 7ZA

How To Reduce Your Exposure

Needless to say, your best bet is to carefully choose the products you use, particularly when it comes to your cookware.

Below is a short table depicting hazardous cookware and why it should be avoided.

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