Sign up to receive email updates, action alerts & health tips from EWG. [Privacy]

DuPont has known for 50 years

Canaries in the Kitchen: DuPont has known for 50 years

May 15, 2003

Environmental Working Group reviewed 16 peer-reviewed studies detailing experiments conducted over the past 50 years, showing that heated Teflon decomposes to 15 types of toxic gases and particles. Many of these studies were conducted by DuPont’s own scientists, who began studying heated Teflon (PTFE) in the 1950s when DuPont workers were developing polymer fume fever that the company found could lead to a potentially fatal condition called pulmonary edema [1]. Since DuPont's discovery of polymer fume fever, cases have been reported in the peer-reviewed literature of the same illness stemming from home kitchen exposures [2, 3].

Teflon offgasing studies show that at the design temperatures of conventional kitchen appliances, Teflon chemicals break apart to form the following particulates and gases:

  • Two chemicals linked to cancer or tumors in laboratory studies (PFOA and TFE);
  • Two chemicals that are potent global warming gases (PFB and CF4);
  • Two chemical warfare agents (PFIB and MFA) and a chemical analog of WWII nerve gas phosgene (COF2);
  • At least two chemicals that have widely contaminated the world (PFOA and TFA), one currently undergoing a rigorous safety review at the Environmental Protection Agency (PFOA);
  • Four gaseous chemicals and some components of the particulate matter that are highly persistent environmental pollutants, that likely never break down in the environment (TFA, PFOA, CF4, PFB, and the perfluorinated particulate alkanes); and
  • Four chemicals that are considered highly toxic relative to most other industrial chemicals (PFIB, MFA, COF2, HF).

Studies show that the gases that come off of non-stick pans are complex mixtures that vary in composition with temperature. At any given temperature the gas comprises one or more dominant chemicals, and other chemicals present in trace quantities. In numerous studies scientists have studied mortality in rats and birds exposed to the offgas mixtures, but potential long-term health impacts have not been studied. The government has not conducted a safety study of Teflon cookware. Accumulation of the offgas chemicals in food has not been studied. The potential effects to humans of inhalation exposures have not been studied, but several of the offgas components are considered highly toxic to humans relative to most other industrial chemicals.

DuPont scientists list the hallmark human symptoms of polymer fume fever as tightness of chest, malaise, shortness of breath, headache, cough, chills, temperatures between 100 and 104°F, and sore throat, based on a survey of complaints registered by workers who were struck by the illness [1]. Based on this suite of symptoms, cases of polymer fume fever from home exposures could easily be mistaken for the common flu.

The toxic particles and gases identified as Teflon offgas products, and the temperature at which they are first identified in the studies reviewed, are shown below, with toxicity information that is drawn primarily from high dose animal studies, the only source of information available for most of the chemicals:

1.   464°F - Ultrafine particulate matter [4]: Teflon produces very small (ultrafine) particles which are very toxic, causing extreme lung damage to rats within 10 minutes of exposure. Longer exposures cause death. At higher temperatures, Teflon also produces toxic gases. Some scientists have found that the particles and gases together are responsible for Teflon's toxicity, perhaps because the gases adsorb to the particles, which because of their small size can lodge deep in the lower respiratory tract [5].

2.   680°F - Tetrafluoroethylene (TFE) [6]: The National Toxicology Program considers tetrafluoroethylene (TFE) to be a “reasonably anticipated” human carcinogen because it is known to cause cancer in laboratory animals, but has not been adequately studied in people. In rats, inhaled TFE causes tumors of the kidney tubules, liver, blood vessels in the liver and one form of leukemia (mononuclear). Mice that breath TFE develop tumors of the liver and tumors that develop in blood vessels in the liver or white blood cells [7].

3.   680°F - Hexafluoropropene (HFP) [6]: In people, air exposure to fluorocarbons like HFP can lead to eye, nose and throat irritation; heart palpitations, irregular heart rate, headaches, light-headedness, fluid accumulation in the lung (edema) and possibly death. Long-term exposure in workers is associated with decreased motor speed, memory and learning [8].

In mice and rats, inhalation of hexafluoropropene (HFP) causes kidney lesions, decreased numbers of a type of immune cell (lymphocyte) and increased urination [9]. HFP also causes increased numbers of chromosomal abnormalities in hamster ovaries [8].

HFP can also be added to pesticides as an “inert” ingredient [10], which does not mean that it is non-toxic, but only that is not the pesticide active ingredient. Another example of a pesticide inert ingredient is butyl benzyl phthalate, a chemical well known to cause serious birth defects of the male reproductive system in laboratory animals.

4.   680°F - Trifluoroacetic acid (TFA) [6]: Very few studies have looked at the toxicity of trifluoroacetic acid (TFA), but those that have found decreased growth of fetal rat bone-forming cells (osteoblast) and cartilage cells (chondrocytes) [11], and neural tube defects in rat embryos at high concentrations [12]. Other studies show that HCFC-123, a hydrofluorocarbon that breaks down into TFA, causes enlarged liver and decreased levels of glucose, triglyceride and cholesterol in adult animals. But, it is unclear whether these effects are due to HCFC-123 or a metabolite [13]. A monkey study found the TFA concentration in the fetus was two to six times higher than in the mother’s blood following dosing with HCFC-123 [14].

The long-term environmental impacts of TFA are unknown, but it is extremely persistent and toxic to plants. TFA is also a breakdown product of many hydrochlorofluorocarbon (HCFCs) and hydrofluorocarbons (HFCs) used as replacement for chlorofluorocarbons (CFCs), which are potent ozone depleters used in refrigeration systems, aerosols and other products. Recently, scientists have suggested that high levels of TFA in the environment could be partly due to heated Teflon and other fluoropolymers because measured environmental levels are higher than predicted, based on breakdown of HCFCs and HFCs alone [6].

5.   680°F - Difluoroacetic acid (DFA) [6]: Very little is known about the toxicity of difluoroacetic acid (DFA), although kidney toxicity has been reported in rats [15].

6.   680°F - Monofluoroacetic acid (MFA, fluoroacetic acid or compound 1080) [6]: Monofluoroacetic acid is extremely toxic, doses as low as 0.7 to 2.1 mg/kg can kill people [16]. Initially, people report nausea, vomiting, numbness, tingling, anxiety, muscle twitching, low blood pressure and blurred vision. If exposure is high enough, people can have irregular heart rate (ventricular fibrillation), heart attacks, and severe convulsions leading to respiratory failure [17].

MFA quickly breaks down into a chemical called fluoroacetate. Sodium fluoroacetate was previously used as a powerful rodent killer (rodenticide). In the body, it breaks down into sodium and fluoroacetate, which is responsible for the toxicity. Sodium fluoroacetate kills rodents, and other animals, by inhibiting the tricarboxylic acid (TCA) cycle which transforms energy found in food to energy the body uses. Sodium fluoroacetate also causes heart and respiratory failure, central nervous system depression and damage to the testes, including decreased sperm production [18].

7.   680°F - Perfluorooctanoic acid (PFOA) [6]: Perfluorooctanoic acid (PFOA) has recently come under significant EPA scrutiny. According to Stephen L. Johnson, Assistant Administrator of EPA's Office of Prevention, Pesticides, and Toxic Substances, the EPA" will be conducting its most extensive scientific assessment ever undertaken on this type of chemical". EPA is concerned about PFOA because it never breaks down in the environment, is found in the blood of over 92 percent of Americans, and is very toxic to rats and monkeys. PFOA causes four types of tumors in rats: liver, pancreas, mammary gland (breast) and testes. PFOA also decreases thyroid hormone levels, a known risk factor for impaired brain development, and delays sexual maturation in laboratory animals. PFOA is especially toxic to the young because it kills young rats at doses that do not kill parental animals. Industry scientists estimate that it takes 4.4 years for people to eliminate just half the amount of PFOA found in their bodies. EPA is taking a close look at PFOA because levels found in the blood of people are too close to levels in rat blood that harm the animals [19, 20].

8.   878°F - Silicon tetrafluoride (SiF4) [21]: Silicon tetrafluoride is a highly toxic, corrosive gas. In the lungs, moisture causes the silicon particles to separate, releasing toxic hydrofluoric acid and also coating the lung with silicon particles. Inhaling hydrofluoric acid can cause eye and throat irritation, cough, difficult breathing, bluish skin color caused by lack of oxygen, lung damage and fluid accumulation in the lung (edema). Long term exposure can cause weight loss, decreased numbers of red and white blood cells (anemia and leukopenia), discoloration of the teeth and abnormal thickening of the bone (osteosclerosis) [22]

9.   887°F - Perfluoroisobutene (PFIB) [23]: Perfluoroisobutene (PFIB) is extremely toxic and inhalation can lead to fluid build up in the lung (edema), a condition that can lead to death. PFIB is listed in the Chemical Weapons Convention as a Schedule 2 compound [24]. PFIB is about ten times more toxic than phosgene, a highly toxic corrosive gas also listed as a chemical weapon. In water, PFIB breaks down into hydrogen fluoride which is also very toxic (see below). Short-term symptoms of PFIB exposure in people include bad taste in mouth, nausea and weakness. Lung edema occurs about one to four hours after exposure, which is life-threatening in some cases, but in most people clears up in about 3 days [25].

10.   932°F - Carbonyl fluoride (COF2) [26]: Breakdown of Teflon (PTFE) in air is the major source of carbonyl fluoride exposure [27]. Carbonyl fluoride is the fluorine version of phosgene, a chlorinated chemical warfare agent. Carbonyl fluoride fumes can irritate eyes, ears and nose. More serious symptoms of exposure include chest pains, breathing difficulty, fluid accumulation in the lungs, weakness, liver damage and increased glucose levels. Because carbonyl fluoride breaks down into hydrogen fluoride and carbon dioxide, it causes many of the same toxic effects as hydrogen fluoride (see below) [27].

11.   932°F - Hydrogen fluoride (HF) [26]: Hydrogen fluoride (HF) is a toxic corrosive gas, and can cause death to any tissue it comes into contact with, including the lungs. The toxicity of HF is due to the fluoride ion and not the hydrogen ion. Breathing HF can cause severe lung damage, such as fluid buildup in the lungs (edema) and inflammation of lung passages (pneumonia) [28].

The fluoride ion (charged particle) is extremely toxic. It is a small ion and weak acid that diffuses quickly and can pass through tissues with relative ease. Fluoride ions inhibit cell respiration, decreasing production of ATP, the major form of chemical energy used by the body. Fluoride attracts cell membranes causing cells to die. The fluoride ion is negatively charged and naturally likes to react with positively charged ions in the body like calcium and magnesium. When fluoride and calcium bind, creating a “precipitate,” a life-threatening condition of decreased calcium (hypocalcemia) can occur. Left untreated, decreases in calcium (and magnesium) can cause abnormal heart rhythm leading to heart attack, muscle spasms and death. Calcium administration is the main treatment for HF poisoning [28].

12.   1112°F - Trifluoroacetic acid fluoride (CF3COF) [21]: Trifluoroacetic acid fluoride is toxic, mostly because it breaks down into hydrogen fluoride, which is very toxic, and trifluoroacetic acid.

The few studies that have looked at the toxicity of TFA found decreased growth of fetal rat bone-forming cells (osteoblast) and cartilage cells (chondrocytes) [11], and neural tube defects in rat embryos at high concentrations [12]. Other studies show that HCFC-123, a hydrofluorocarbon that breaks down into TFA, causes enlarged liver and decreased levels of glucose, triglyceride and cholesterol in adult animals, but it is unclear whether these effects are due to HCFC-123 or a metabolite [13]. A monkey study found TFA in the fetus was two to six times higher than in the mother’s blood following dosing with HCFC-123, a hydrofluorocarbon that breaks down into TFA [14].

Fluoride ion (charged particle) is extremely toxic. It is a small ion and weak acid that diffuses quickly and can pass through tissues with relative ease. Fluoride ions inhibit cell respiration, decreasing production of ATP, the major form of chemical energy used by the body. Fluoride attracts cell membranes causing cells to die. The fluoride ion is negatively charged and naturally likes to react with positively charged ions in the body like calcium and magnesium. When fluoride and calcium bind, creating a “precipitate,” a life-threatening condition of decreased calcium (hypocalcemia) can occur. Left untreated, decreases in calcium (and magnesium) can cause abnormal heart rhythm leading to heart attack, muscle spasms and death. Calcium administration is the main treatment for HF toxicity [28].

13.   1112°F - Octafluorocyclobutane (OFCB) [21]: Octaflurocyclobutane is a fluorine-containing gas that is used in the semiconductor industry, sold as Zyron 8020 by DuPont. According to DuPont, inhaling high levels of octafluorocyclobutane can cause heart beat irregularities, unconsciousness and death. People with pre-existing heart conditions may be extra vulnerable. Only a few toxicity studies in animals are available for octafluorocyclobutane. In one study, rats exposed to a one-time-only inhaled exposure of octafluorocyclobutane lost weight and had abnormal breathing. Dogs that inhaled high concentrations (10-25% air), and were dosed with the stimulant epinephrine, had heart problems. According to DuPont, tests for genetic damage in insects are “inconclusive” [29].

14.   1112°F - Perfluorobutane (PFB, Trade Name CEA-410) [21]: As a global warming chemical, perfluorobutane has a long half-life in the upper atmosphere and has over 8,000 times the global warming potential of carbon dioxide [30]. Perfluorobutane is not as acutely toxic as other PTFE off-gases, but has not been tested for long-term effects.

15.   1202°F - Carbon tetrafluoride (CF4, perfluoromethane) [21]: In addition to being a long-lived fluorinated Teflon “off-gas,” perfloromethane is used in the semiconductor industry, is a refrigerant and propellant and a byproduct of aluminum production. The U.S. government is encouraging these industries to decrease emissions of perfluoromethane because it is a potent greenhouse gas, with a global warming potential almost 6000 times higher than carbon dioxide, and can last in the environment for 50,000 years [30, 31]. In the past, perfluoromethane has been used in pesticides as an “inert” ingredient, [32] a label that has nothing to do with toxicity but only means the ingredient is not the main active pesticide.

Inhaling fluorinated hydrocarbons like carbon tetrafluoride can cause eye, ear and nose irritation; heart palpitations; irregular heart rate; headaches; confusion; lung irritation, tremors and occasionally coma [33].

References:

[1] Clayton, JW. 1967. Fluorocarbon toxicity and biological activity. Fluorine Chemistry Reviews 1(2): 197-252.

[2] Blandford, TB., Seamon, PJ., Hughes, R., Pattison, M and Wilderspin, MP. 1975. A case of polytetrafluoroethylene poisoning in cockatiels accompanied by polymer fume fever in the owner. Vet Rec 96(8): 175-8.

[3] Zanen, AL and Rietveld, AP. 1993. Inhalation trauma due to overheating in a microwave oven. Thorax 48(3): 300-2.

[4] 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.

[5] Johnston CJ, Finkelstein JN, Mercer P, Corson N, Gelein R, Oberdorster G. 2000. Pulmonary effects induced by ultrafine PTFE particles. Toxicol Appl Pharmacol 168:208-15.

[6] Ellis DA, Mabury SA, Martin JW, Muir DC. 2001. Thermolysis of fluoropolymers as a potential source of halogenated organic acids in the environment. Nature 412:321-4.

[7] National Toxicology Program (NTP). 2002. 10th Report on Carcinogens. http://ehp.niehs.nih.gov/roc/toc10.html.

[8] Hazardous Substances Data Bank (HSDB). 2003. Full record for 1,1,2,3,3,3 - hexafluoro-1-propene (CASRN: 116-15-4). Available online at http://toxnet.nlm.nih.gov/.

[9] Environmental Protection Agency (EPA). Fluoroalkenes Test Results; Data submitted by DuPont on Hexafluoropropene (HFP). Office of Prevention, Pesticides & Toxic Substances Data Development (Testing) Policy Avialable online at http://www.epa.gov/oppt/chemtest/fluralke.htm.

[10] Environmental Protection Agency (EPA). List of other (inert) pesticide ingredients. Available online at http://www.epa.gov/opprd001/inerts/lists.html.

[11] Cornish J, Callon KE, Lin CQ, Xiao CL, Mulvey TB, Cooper GJ, Reid IR. 1999. Trifluoroacetate, a contaminant in purified proteins, inhibits proliferation of osteoblasts and chondrocytes. Am J Physiol 277:E779-83.

[12] Hunter ES, 3rd, Rogers EH, Schmid JE, Richard A. 1996. Comparative effects of haloacetic acids in whole embryo culture. Teratology 54:57-64.

[13] Buschmann J, Bartsch W, Dasenbrock C, Fuhst R, Pohlmann G, Preiss A, Berger-Preiss E. 2001. Cross-fostering inhalation toxicity study with HCFC-123 in lactating Sprague-Dawley rats. Inhal Toxicol 13:671-87.

[14] Cappon GD, Keller DA, Brock WJ, Slauter RW, Hurtt ME. 2002. Effects of HCFC-123 exposure to maternal and infant rhesus monkeys on hepatic biochemistry, lactational parameters and postnatal growth. Drug Chem Toxicol 25:481-96.

[15] Lantum HB, Baggs RB, Krenitsky DM, Anders MW. 2002. Nephrotoxicity of chlorofluoroacetic acid in rats. Toxicol Sci 70:261-8.

[16] Key BD, Howell RD, Criddle CS. 1997. Fluorinated organics in the biosphere. Environmental Science & Technology 31:2445-2454.

[17] Hazardous Substances Data Bank (HSDB). 2003. Full record for fluoroacetic acid (CASRN: 144-49-0). Available online at http://toxnet.nlm.nih.gov/.

[18] Integrated Risk Information System (IRIS). 1991. Sodium Fluoroacetate (CASRN: 62-74-8). Available online at http://www.epa.gov/iris/subst/0469.htm.

[19] Environmental Protection Agency (EPA). 2003. Preliminary risk assessment of the developmental toxicity associated with exposure to perfluorooctanoic acid and its salts. March 17, 2003.

[20] Environmental Protection Agency (EPA). 2002. Revised draft hazard assessment of perfluorooctanoic acid and its salts, November 4, 2002. U.S. EPA Administrative Record AR226-1136.

[21] Arito, H and Soda, R. 1977. Pyrolysis products of polytetrafluoroethylene and polyfluoroethylenepropylene with reference to inhalation toxicity. Ann Occup Hyg 20(3): 247-55.

[22] Hazardous Substances Data Bank (HSDB). 2003. Full record for silicon tetrafluoride (CASRN: 7783-61-1). Available online at http://toxnet.nlm.nih.gov/.

[23] Waritz, RS. 1975. An industrial approach to evaluation of pyrolysis and combustion hazards. Environ Health Perspect 11: 197-202.

[24] United States Department of State and Department of Commerce. 2003. U.S. Chemical Weapons Convention Web Site. Site sponsored by the United States Department of State (DOS), Bureau of Arms Control and the United States Department of Commerce, Bureau of Industry and Security (BIS) Available online at http://www.cwc.gov/.

[25] Patocka J, Bajgar J. 1998. Toxicology of perfluroisobutene. The Applied Science and Analysis (ASA) newsletter ISSN 1057-9419 Available online at http://www.asanltr.com/ASANews-98/pfib.html.

[26] Scheel, LD., Lane, WC and Coleman, WE. 1968. The toxicity of polytetrafluoroethylene pyrolysis products including carbonyl fluoride and a reaction product, silicon tetrafluoride. Am Ind Hyg Assoc J 29(1): 41-8.

[27] Hazardous Substances Data Bank (HSDB). 2003. Full record for carbon difluoride (CASRN: 353-50-4). Available online at http://toxnet.nlm.nih.gov/.

[28] International Programme on Chemical Safety (IPCS). 1995. Hydrogen Fluoride (CASRN: 7664-39-3). Available online at http://www.inchem.org/documents/pims/chemical/ hydfluor.htm#PartTitle:1.%20%20%20%20NAME.

[29] DuPont. 2002. Material Safety Data Sheet (MSDS) for Zyron (octafluorocyclobutane CASRN 115-25-3). Available online at msds.dupont.com/msds/pdfs/EN/PEN_09004a2f800a5e88.pdf.

[30] Environmental Protection Agency (EPA). Global Warming Potentials of ODS (Ozone Depleting Substances) Substitutes. Available online at http://www.epa.gov/ozone/geninfo/gwps.html.

[31] State Department. Mitigating climate change: methane and other greenhouse gas programs. Available online at http://www.state.gov/www/global/oes/97climate_report/part4b.html.

[32] Environmental Protection Agency (EPA). 1998. Inert ingredients no longer used in pesticide products. Federal Register (Volume 63, Number 121):Page 34384-34390 Available online at http://www.epa.gov/fedrgstr/EPA-PEST/1998/June/Day-24/p16571.htm.

[33] Hazardous Substances Data Bank (HSDB). 2003. Full record for tetrafluoromethane (CASRN: 75-73-0). Available online at http://toxnet.nlm.nih.gov/.