PTFE
Hundreds of Scientists Issue Warning About Chemical Dangers of
Non-Stick Cookware and Water-Repellant Items
By Dr. Mercola
Non-stick
cookware and bakeware has become enormously popular because of its convenience.
Foods slide right off, reducing the amount of elbow-grease required to clean
the pan.
Ditto
for stain- and water-repellant clothing, carpets and fabrics, and many other
treated products that have emerged over the past six decades.
But
there may be a high price to pay for this convenience, as the poly- and
perfluoroalkyl substances (PFAS) used to create these surfaces are toxic and
highly persistent, both in your body and in the environment.
As you can tell by the names, PFAS are fluorinated chemicals. It's
actually the fluorine atoms that provide that hallmark slipperiness. I first
became aware of the dangers of fluoride-impregnated
non-stick coatings back
in 2001.
I
revised my cookware recommendations back then, and many of the health concerns
I've warned about since then were recently confirmed by hundreds of
international scientists.
You Probably Have PFAS in Your Home—And in Your Body
When heated, non-stick cookware becomes a source of
perfluorooctanoic acid (PFOA),
a long-chain perfluorinated chemical linked to a range of health problems,
including thyroid disease, infertility in
women, and organ damage and developmental and reproductive problems in lab
animals.
The
US Environmental Protection Agency (EPA) has also ruled perfluorinated
compounds (PFCs) as "likely carcinogens." Despite that, these
chemicals are still used in a wide array of household products. Besides
non-stick cookware, PFCs are used to create heat-resistant and non-stick
coatings on:
·
Soil- and water-repellant carpet and furniture treatments
·
Stain- and water-repellant clothing
·
Protective sprays for leather and shoes
·
Food wraps, pizza boxes, and microwave popcorn bags
·
Paint and cleaning products
They're
also found in flame retardant chemicals (and, hence, items treated with flame
retardants). PFCs are also being released into the environment via factory
emissions, and during house fires when treated items burn.
According to the CDC's "Fourth National Report on Human
Exposure to Environmental Chemicals,"1 published
in 2009, 12 different PFCs were detected in Americans, including PFOA.
According to the Agency for Toxic Substances & Disease Registry (ATSDR):2
"Once
in your body, perfluoroalkyls tend to remain unchanged for long periods of
time. The most commonly used perfluoroalkyls (PFOA and PFOS) stay in the body
for many years. It takes approximately four years for the level in the body to
go down by half, even if no more is taken in."
While
there's a dizzying array of chemical names in the PFAS groups, if an item is
either non-stick, waterproof, or stain-resistant, it has some type of
fluoride-impregnated coating that provides the slipperiness, and you can be
virtually guaranteed it will be problematic.
Phased Out PFAS Replaced with Others of Similar Concern
In 2006, the EPA launched the 2010/15 PFOA Stewardship Program,3 and
companies agreed to voluntarily reduce the use of PFOA and related chemicals by
95 percent by 2010, with the aim to eliminate them by 2015.
Unfortunately,
it was only a voluntary program and much of the damage has already been done,
as these chemicals have been found to be extremely resistant to biodegradation.
Some polyfluorinated chemicals also break down to form perfluorinated ones.
Making matters worse, the chemicals targeted for phase out are
being replaced with anothergroup of PFAS that share many of the same problems
as the ones being eliminated.4
The
newer, short-chain PFAS are thought to be less hazardous, but scientists warn
we don't yet know enough about them to make a solid determination about their
safety. There are certainly warning signs suggesting we're just trading one
danger for another...
For example, a recent Danish study5 looking
into the health effects of PFAS, including the newer short-chain versions that
are replacing the older long-chained ones, found that women with higher blood
levels of PFAS had a 16-fold increased risk for miscarriage.
We see the same problem happening with flame
retardants, which has lead a group of scientists to propose a ban on an
entire class of chemicals (organohalogens) rather than tackling them
one-by-one, in an effort to put an end to this "toxic whack-a-mole
game" played by the chemical industry.6
As for the newer, short-chain PFAS taking over the market, Arlene
Blum, a University of California chemist, and the executive director of the
Green Science Policy Institute says:7
"We
know these substitutes are equally
persistent. They don't break down for geologic time... It's a very serious
decision to make chemicals that last that long, and putting them into consumer
products with high levels of human exposure is a worrisome thing."
Non-Stick Cookware Release Toxic Fumes
In studies of heated non-stick pans on conventional stovetops,
commissioned by the consumer watchdog organization Environmental Working Group
(EWG),8 it
only took two to five minutes of
heating to reach temperatures at which dangerous toxins were produced.
The
coating begins to break down and release toxins into the air at 464 degrees
Fahrenheit. When the pot or pan reaches 680 degrees F, they release at least
six toxic gasses, including two carcinogens (PFOA and TFE), and
monofluoroacetic acid (MFA), a chemical warfare agent that is deadly to humans
even at low doses.
According to the EWG, studies conducted by DuPont's own scientists
revealed that when its non-stick cookware is heated it breaks down into 15
types of toxic gases and particles.9 For
a list reviewing them all, please see EWG's 2003 report, "Canaries in the
Kitchen: DuPont Has Known for 50 Years,"10 which
also notes:
"DuPont
acknowledges that the fumes can also sicken people, a condition called 'polymer
fume fever.' DuPont has never studied the incidence of the fever among users of
the billions of non-stick pots and pans sold around the world. Neither has the
company studied the long-term effects from the sickness, or the extent to which
exposures lead to human illnesses believed erroneously to be the common
flu."
Hundreds of Scientists Issue Warning Over PFAS
Arlene Blum (mentioned earlier) is also the lead author of the
recently published Madrid Statement,11,12 signed
by more than 200 scientists from 40 countries,13 which
presents the scientific consensus on the harms of PFAS chemicals, old and new.
For example, the Statement points out that:
1. "Although some of the
long-chain PFASs are being regulated or phased out, the most common
replacements are short-chain PFASs with similar structures, or compounds with
fluorinated segments joined by ether linkages.
2. While some shorter-chain
fluorinated alternatives seem to be less bioaccumulative, they are still as
environmentally persistent as long-chain substances or have persistent
degradation products.
Thus,
a switch to short-chain and other fluorinated alternatives may not reduce the
amounts of PFASs in the environment. In addition, because some of the
shorter-chain PFASs are less effective, larger quantities may be needed to
provide the same performance.
3. While many fluorinated alternatives
are being marketed, little information is publicly available on their chemical
structures, properties, uses, and toxicological profiles.
4. Increasing use of fluorinated
alternatives will lead to increasing levels of stable perfluorinated degradation
products in the environment, and possibly also in biota and humans. This would
increase the risks of adverse effects on human health and the
environment."
An editorial14 accompanying
the Madrid Statement echoes the same warning, saying: "Given the fact that
research raised concern about the long-chain PFASs for many years before action
was taken and that global contamination and toxicity have been documented in
the general population, potential risks of the short-chain PFASs should be
taken into account when choosing replacements for the longer-chain
compounds."
In fact, 10 years ago, the EPA fined DuPont $16.5 million for withholding
decades' worth of information about health hazards associated with PFAS. As
noted in a recent report15 by
the Environmental Working Group (EWG):
"DuPont
had long known that PFOA caused cancer, had poisoned drinking water in the
mid-Ohio River Valley and polluted the blood of people and animals worldwide. But it never told its workers,
local officials and residents, state regulators, or the EPA." At
the time, that fine was the largest the EPA had ever assessed, but it was still
too small to act as a deterrent.
Documented Health Effects of PFAS
The Madrid Statement lists many of the documented health effects
associated with the older, long-chain PFASs, including the following:16
Liver toxicity
|
Disruption of lipid metabolism, and the
immune and endocrine systems
|
Adverse neurobehavioral effects
|
Neonatal toxicity and death
|
Tumors in multiple organ systems
|
Testicular and kidney cancers
|
Liver malfunction
|
|
High cholesterol
|
Ulcerative colitis
|
Reduced birth weight and size
|
Obesity
|
Decreased immune response to vaccines
|
Reduced hormone levels and delayed puberty
|
How to Avoid These Dangerous Chemicals
The Madrid Statement17 recommends
avoiding any and all products containing, or manufactured using, PFASs, noting
they include products that are stain-resistant, waterproof, or non-stick. More
helpful tips can be found in the EWG's Guide to Avoiding PFCS.18 Besides
listing a number of sportswear brands known to use PFCs in their shoes and
clothing, the Guide also notes that Apple admits the wristband of its new Apple
Watch Sport model is made with PFCs. Other suggestions that will help you avoid
these dangerous chemicals include avoiding:
Items that have been
pre-treated with stain-repellants, and opt out of such treatments when
buying new furniture and carpets
|
Water- and/or stain-repellant
clothing.
One tipoff is when an item made with artificial fibers is described as
"breathable." These are typically treated with
polytetrafluoroethylene (PTFE), a synthetic fluoropolymer
|
Items treated with flame-retardant
chemicals,19 which includes a
wide variety of baby items, padded furniture, mattresses, and pillows.
Instead, opt for naturally less flammable materials such as leather, wool,
and cotton
|
Fast food and carry out foods, as the wrappers
are typically treated with PFCs
|
Microwave popcorn. PFOA may not only
present in the inner coating of the bag, it also may migrate to the oil from
the packaging during heating. Instead, use "old-fashioned" stovetop
popcorn
|
Non-stick
cookware and other treated
kitchen utensils. Healthier options include ceramic and enameled cast iron
cookware, both of which are durable, easy to clean (even the toughest
cooked-on foods can be wiped away after soaking it in warm water), and
completely inert, which means they won't release any harmful chemicals into
your home. While some will recommend using aluminum, stainless steel, and
copper cookware, I don't for the following reasons:
Aluminum is a strongly suspected causal
factor in Alzheimer's disease, and stainless steel has alloys containing
nickel, chromium, molybdenum, carbon. For those with nickel allergies, this
may be a particularly important consideration. Copper cookware is also not
recommended because most copper pans come lined with other metals, creating
the same concerns noted above. (Copper cookware must be lined due to the
possibility of copper poisoning.)
|
Oral-B Glide floss and any
other personal care products containing PTFE or
"fluoro" or "perfluoro" ingredients. The EWG has an
excellent database called Skin Deep20 you can peruse to
find healthier options
|
How Toxic is Teflon?
If you’ve got some old pans around the house, you might have
wondered, how toxic is Teflon? In this post we’ll break it down for you, and
help you find safer cooking alternatives.
Let’s take a closer look at what Teflon is
all about and learn exactly how toxic is Teflon for humans and for our
environment.
Teflon is great for keeping burnt food off
your pots and pans while saving you time and energy spent on scrubbing or
seasoning. But is this convenience truly convenient, or is it an additional
health hazard in your home? What is Teflon?
Teflon is the trade name for a synthetic
polymer, polytetrafluoroethylene (PTFE). If you’re an organic chemistry pro,
maybe you can visualize the molecular structure just by reading the name. If
you’re like the rest of us, PTFE is a polymer that is hydrophobic, meaning it
doesn’t stick to water or water-containing substances (anything that’s wet). It
also has one of the lowest coefficients of friction against any solid, giving
it the necessary qualities for great non-stick cookware.
Studies
show that in
about 5 minutes, a Teflon-coated pan heats up to around 750ºF. According to the
Environmental Working Group, thermal degradation of PTFE leads to a litany of
toxic compounds, including highly corrosive and lethal gases, and PFIB, a
chemical warfare agent that is 10 times more lethal than phosgene (a chemical
warfare agent used in WWI and WWII). These compounds persist in the environment
and are not known to break down further.
How Toxic is Teflon?
Once scratched, teflon pans begin an
inevitable march toward complete exfoliation. That is, all that teflon is going
to end up in your food, and then inside your body.
According to the Environmental Working
Group, teflon and PFOA (which is the chemical used to make teflon) are some of
the most persistent chemicals in the world. Their toxic legacy will outlive
every one of us, and the next 25 generations of our offspring. Ironically, it
may shorten each generation’s lifespan, as well. PFOA’s effects include
liver damage, immune dysfunction, thyroid dysfunction, and a decreased ability
to fight infection.
Teflon Kills Birds
PTFE is most notorious for its toxicity to
birds. This has been referred to as “Teflon toxicosis” where the lungs of
exposed birds hemorrhage, filling up with fluid and leading to
suffocation. Here are some shocking stories of bird deaths related to Teflon
(PTFE) exposure (all references
can be found in the EWG article node):
§ Four
stove top burners, underlined with Teflon-coated drip pans, were preheated in
preparation for Thanksgiving dinner; 14 birds died within 15 minutes [2] [5].
§ Nonstick
cookie sheet was placed under oven broiler to catch the drippings; 107 chicks
died [2]
§ Water
burned off a hot pan; more than 55 birds died [7].
§ Electric
skillet at 300°F and space heater were used simultaneously; pet bird died [8].
§ Toaster
oven with a non-stick coating was used to prepare food at a normal temperature;
bird survived but suffered respiratory distress [9].
§ Water
being heated for hot cocoa boiled off completely; pet bird died [10].
§ Grill
plate on gas stove used to prepare food at normal temperatures; two birds died
on two separate occasions [11].
Teflon Toxicity in Humans
In humans, Teflon toxicity causes polymer
fume fever, a temporary, intense, though
not very serious influenza-like syndrome. Only a few cases have been reported
of people going to the hospital from overheated Teflon. Since the fever mimics
the flu, it is likely doctors would not realize the origin of the illness
coming from overheated Teflon. Polymer fume fever is only caused from exposure
to PTFE breakdown products. Further alarm comes as PTFE residuals, known as
perfluorocarbons (PFC’s) were found in breast milk from all 45 nursing mothers
tested in this study.
DuPont, the original inventor and
manufacturer of Teflon-coated products have known for over 50 years the toxic
health effects of exposure to heated Teflon. When their workers were becoming
ill on the job, DuPont conducted a study
on humans with Teflon-laced cigarettes. Nine out of the ten
participants developed polymer fume fever. DuPont has exhibited questionable
behavior including sending many
letters to bird owners who have
publicly spoken or blogged about the connection of Teflon to their bird deaths.
The company claims it is a trademarked name, so perhaps the PTFE coating was
from another company.
Birds dying is enough for me to know Teflon
is not safe in my food. Polymer fume fever and all the breakdown products just
make the whole Teflon story even worse.
Safe Alternatives for Healthy Cooking
For safer, more reliable cooking
alternatives to Teflon, consider these time-tested methods:
Stainless Steel
Stainless steel is a popular choice for
healthy cookware because it is one of the most inert metals, though it has been
reported to leach a small amount of chromium and nickel, which may be
problematic for those with a sensitivity or allergy to chromium or nickel.
All-Clad cookware makes a sandwich of
copper and aluminum layers in between stainless steel, allowing for
greater and more even heat conductivity through copper and aluminum, while
keeping your feed free of copper or aluminum toxicity. Check out this guide to stainless steel cookware.
Cast Iron
Cast iron pans work just as well as
non-stick pots and pans when seasoned properly. The more oil residue built up
on the pans, the greater non-stick effect is produced. Cast iron pots and pans
have been used for centuries and are popular with campers. They take some
special maintenance, but they are inexpensive and add iron to your diet. If you
have an iron deficiency, this is a really great benefit. Learn how to cook with cast iron pans and why
it’s so awesome!
Eco-Friendly Non-Stick Pans
Over the years I’ve tried a few
eco-friendly non-stick pans like Green Pan and
Cuisinart’s eco-options, but I’ve not been super impressed with either. Both
work great initially, but tend to lose their non-stick after about a year.
Invest in the cast iron and save the cash!
What are Teflon and
PFOA? Where are they found?
Teflon® is a
brand name for a man-made chemical known as polytetrafluoroethylene (PTFE). It
has been in commercial use since the 1940s. It has a wide variety of uses
because it is extremely stable (it doesn’t react with other chemicals) and can
provide an almost frictionless surface. Most people are familiar with it as a
non-stick coating surface for pans and other cookware. It is also used in many
other products, such as fabric protectors.
Perfluorooctanoic
acid (PFOA), also known as C8, is another man-made chemical. It is used in the
process of making Teflon and similar chemicals (known as fluorotelomers),
although it is burned off during the process and is not present in significant
amounts in the final products.
PFOA has
the potential to be a health concern because it can stay in the environment and
in the human body for long periods of time. Studies have found that it is
present worldwide at very low levels in just about everyone’s blood. Higher
blood levels have been found in community residents where local water supplies
have been contaminated by PFOA. People exposed to PFOA in the workplace can
have levels many times higher.
PFOA and
some similar compounds can be found at low levels in some foods, drinking
water, and in household dust. Although PFOA levels in drinking water are
usually low, they can be higher in certain areas, such as near chemical plants
that use PFOA.
People
can also be exposed to PFOA from ski wax or from fabrics and carpeting that
have been treated to be stain resistant. Non-stick cookware is not a
significant source of PFOA exposure.
Do Teflon and PFOA cause
cancer?
Teflon
Teflon
itself is not suspected of causing cancer.
PFOA
Many
studies in recent years have looked at the possibility of PFOA causing cancer.
Researchers use 2 main types of studies to try to figure out if such a
substance might cause cancer.
Studies in the lab
In
studies done in the lab, animals are exposed to a substance (often in very
large doses) to see if it causes tumors or other health problems. Researchers
might also expose human cells in a lab dish to the substance to see if it
causes the types of changes that are seen in cancer cells.
Studies
in lab animals have found exposure to PFOA increases the risk of certain tumors
of the liver, testicles, mammary glands (breasts), and pancreas in these
animals. In general, well-conducted studies in animals do a good job of
predicting which exposures cause cancer in people. But it isn’t clear if the
way this chemical affects cancer risk in animals would be the same in humans.
Studies in humans
Some
types of studies look at cancer rates in different groups of people. These
studies might compare the cancer rate in a group exposed to a substance to the
cancer rate in a group not exposed to it, or compare it to the cancer rate in
the general population. But sometimes it can be hard to know what the results
of these types of studies mean, because many other factors might affect the
results.
Studies have looked at people exposed to PFOA from living near
or working in chemical plants. Some of these studies have suggested an
increased risk of testicular
cancer with increased PFOA exposure.
Studies have also suggested possible links to kidney
cancer and thyroid
cancer, but the increases in risk have been small and could have been
due to chance.
Other studies have suggested possible links to other cancers,
including prostate, bladder, and ovarian
cancer. But not all studies have found such links, and more research
is needed to clarify these findings.
What
expert agencies say
Several national and international agencies study different
substances in the environment to determine if they can cause cancer. (A substance
that causes cancer or helps cancer grow is called a carcinogen.) The
American Cancer Society looks to these organizations to evaluate the risks
based on evidence from laboratory, animal, and human research studies.
The International
Agency for Research on Cancer (IARC) is part
of the World Health Organization (WHO). One of its goals is to identify causes
of cancer. IARC has classified PFOA as “possibly carcinogenic to humans” (Group
2B), based on limited evidence in humans that it can cause testicular and
kidney cancer, and limited evidence in lab animals.
(For more information on the classification system IARC uses,
see Known
and Probable Human Carcinogens.)
The US Environmental
Protection Agency (EPA) maintains
the Integrated Risk Information System (IRIS), an electronic database that
contains information on human health effects from exposure to various
substances in the environment. The EPA has not officially classified PFOA as to
its carcinogenicity.
In a
draft (not final) report, the EPA’s Scientific Advisory Board examined the
evidence on PFOA, mainly from studies in lab animals, and stated that there is
“suggestive evidence of carcinogenicity, but not sufficient to assess human
carcinogenic potential.” The board agreed that new evidence would be considered
as it becomes available.
Other
agencies have not yet formally evaluated whether PFOA can cause cancer.
What is being done about
PFOA?
The
long-term effects of PFOA and similar chemicals are largely unknown, but there
has been enough concern to prompt an attempt to phase out industrial emissions
of them. Only a handful of companies have used these chemicals in manufacturing
in recent years.
While
the possible long-term health effects of PFOA are not known, the issue is
currently under study by the EPA and other agencies. In addition, in 2006, the
EPA and the 8 manufacturers who used PFOA at the time agreed to a “stewardship
program.” The goals were for the companies to reduce factory emissions and
product content levels of PFOA by 95% by the year 2010, and to eliminate PFOA
from emissions and product contents by the end of 2015. The companies have
submitted annual reports on their progress to the EPA, and the latest reports
indicated a large reduction in use of these chemicals. The decreasing demand
for PFOA has also led to many companies phasing out production.
The EPA
does not regulate the levels of PFOA or related chemicals (such as
perfluorooctanesulfonate, or PFOS) in drinking water at this time. However, in
2009, the EPA released provisional health advisories (PHAs) for PFOA and PFOS
in drinking water. These advisories recommend that actions should be taken to
reduce exposure when contaminants go above a certain level in the drinking
water – 0.4 µg/L (micrograms per liter) for PFOA and 0.2 µg/L for PFOS. These
advisories are not legally enforceable federal standards and are subject to
change as new information becomes available.
Should I take measures
to protect myself, such as not using my Teflon-coated pans?
Other
than the possible risk of flu-like symptoms from breathing in fumes from an
overheated Teflon-coated pan, there are no known risks to humans from using
Teflon-coated cookware. While PFOA is used in making Teflon, it is not present
(or is present in extremely small amounts) in Teflon-coated products.
Because
the routes by which people may be exposed to PFOA are not known, it is unclear
what steps people might take to reduce their exposure. According to the US
Centers for Disease Control and Prevention (CDC), people whose regular source
of drinking water is found to have higher than normal levels of PFOA or similar
chemicals might consider using bottled water or installing activated carbon
water filters.
For
people who are concerned they might have been exposed to high levels of PFOA,
blood levels can be measured, but this is not a routine test that can be done
in a doctor’s office. Even if the test is done, it’s not clear what the results
might mean in terms of possible health effects.
Additional resources
We have a lot more information that you might find helpful.
Explore www.cancer.org or
call our National Cancer Information Center toll-free number, 1-800-227-2345.
We’re here to help you any time, day or night.
Is it safe to use non-stick frying pans and cookware?
Before I answer, let
me give a quick overview of how us toxicologists approach these kinds of
questions. When assessing safety of any chemical or component, there are two
types of information that needs to be gathered: hazard characterization and
exposure assessment. In other words, what is the toxic compound and what toxic
effects might it cause (hazard characterization)? Then, are people exposed to
the compound? If so, how does it get into the body? And how much? Is the amount
people are exposed to enough to cause harmful effects (exposure assessment)?
Toxicologists design experiments to generate these two types of information.
Integrating
these pieces of information allows us to make our best estimate of the risk of
chemicals being toxic to humans, a form of risk assessment. These are only estimates since much of this information is
sometimes difficult to obtain practically (you can’t expose humans to
potentially toxic compounds in a study!). Thus, we must rely on animal studies,
testing individual cells, and computer models. Now, lets apply this method to
non-stick pans.
Hazard
Characterization
What makes pans non-stick? What is the potentially toxic
component?
The most
common non-stick coating used to coat pots and pans is Teflon, a chemical
mixture of perfluorochemicals (chemicals with lots of fluoride atoms).
Developed by DuPont chemical company in 1938, these chemicals are extremely
non-polar, meaning they do a very good job repelling other chemicals. As such,
Teflon is used as an additive to paints, fabrics, carpets, and clothing. It is
also used to treat materials to make them resistant to oils (like the inside of
microwave popcorn bags). The primary chemical in Teflon,
polytetrafluoroethylene (PTFE), has a high melting point (327 ºC), making it
ideal for cooking applications. However, when heated to temperatures above 350
ºC (662 ºF), PTFE begins to degrade, releasing fine particles and a variety of
gaseous compounds that can cause damage to the lungs when inhaled (Waritz,
1975).
How are we exposed to PTFE? What is the route of exposure?
Inhalation
of the PTFE-fumes from overheating a non-stick pan is one method of exposure.
Since we use these pans to cook food, we might suppose that people could be
ingesting PTFE, say if some of the coating gets into the food cooked in the
pan. We want to estimate risk for the worst-case scenario so we will consider
both routes of exposure.
What is known about the harmful effects, or toxicities, of PTFE?
Via inhalation
Numerous
case studies in the 1900s have documented flu-like symptoms after inhalation of
PTFE fumes by workers in PTFE-using factories and by people overheating
non-stick pans in the kitchen. This condition is called polymer fume fever, or
“Teflon flu”, and presents with temporary, intense, but not serious symptoms
such as fever, shivering, sore throat and coughing (Harris, 1951 &Shumizu,
2012). These cases of Teflon flu are due to acute (short-term) exposures to
PTFE fumes; no studies have been done looking at the long-term effects of
brief, repeated PTFE-fume exposure, as would be the case in cooking using
non-stick pans for a lifetime.
Birds were
found to be particularly susceptible to the PTFE fumes, based on some reports
that pet birds were dying after their owners left a coated pan heating on the
stove. Indeed, parakeets and Japanese quails died after exposure for 4 hours to
PTFE fumes generated at 330 ºC (626 ºF) (Waritz, 1975 & Griffith, 1973). In
summary, inhalation toxicity becomes a concern when PTFE is heated to high
temperatures which releases toxic particles and gases that could result in
polymer fume fever. These effects are more prominent, if not lethal, in birds
than in humans.
Via ingestion
PTFE is
inert in its solid form, meaning it won’t react with other chemicals, which is
what makes it such as great non-stick coating. As such, the minimal PTFE you
would ingest will likely pass through the digestive tract without harm.
However, another fluorinated compound, PFOA (perfluorooctanoic acid), is
commonly used in the process of making PTFE and may be residual in non-stick
coating components. After repeated heating and cooling, it is possible that the
PFOA could migrate into the food. Research suggests that PFOA interferes with
hormonal balances as well as reproduction and fetal development (White, 2011
& Post, 2012).
Exposure
assessment
Do non-stick pans generate these toxic PTFE-fumes when I use
them in the kitchen?
Typical
temperatures for frying foods range from 130 ºC for fish fillets to 280 ºC for
steak (266 ºF, 536 ºF, respectively) and the maximum temperature for most
household ovens is 500 ºF (Lehman, 1962). Given that PTFE degrades above 350 ºC
(662 ºF), I would presume that the temperatures typically used to cook foods do
not generate sufficient PTFE-fumes to cause polymer fume fever. Many of the
case studies reporting polymer fume fever were results of unattended heating
and of heating empty non-stick pans. Furthermore, most kitchens have reasonable
ventilation that would protect the user. Altogether, non-stick pans could
produce PTFE-fumes if used improperly. Typical cooking practices will probably
not generate a significant amount of these fumes.
How much PFOA is there? How much PFOA comes from non-stick pans?
While PFOA
is used in the production of non-stick coatings, it is thought that there is
minimal PFOA in PTFE. DuPont removed PFOA from Teflon production in 2013 as a
part of the 2010/2015 PFOA Stewardship Program, an initiative by eight
manufacturing companies organized by EPA to reduce PFOA emissions and use in
production (EPA).
PFOA is hard
to degrade and it can remain in the environment and the human body for a long
time. Thus, repeated exposure to small amounts of PFOA could build up over time
and cause toxicity. In fact, PFOA has been detected in the blood of almost all
US residents (Post, 2012). To determine how much PFOA could come from non-stick
coatings, Begley and his team at the U.S. FDA designed an experiment to
investigate the possibility of PFOA transfer from PTFE-coated pans to food.
Using the most conservative estimates, they found that minimal amounts of PFOA
transferred from PTFE cookware, even after intensive heating of the pans
(Begley, 2005). Thus, it is more likely that humans are exposed to PFOA through
other means than by ingestion of residual PFOA from food cooked in a non-stick
pan.
Limitations
All research
has its limitations. We can’t measure everything, our tests aren’t perfect, and
we can’t account for all the variables when designing the experiments. Thus, every
risk assessment needs to identify and address the caveats. The biggest question
that is not answered by research is the long-term effect of exposure to small
amounts of PTFE and PFOA. This kind of exposure is more representative of how
people come into contact with Teflon and its toxic components.
And the answer is…
In
conclusion, to my dear newlywed friends and other interested readers, is it
safe to use non-stick frying pans and cookware? Assuming you use your cookware
appropriately, i.e. not heating it excessively and unattended, always heating
the pan with something in it, not scratching off the Teflon and consuming it
for dinner, using non-stick pans is relatively safe for humans. Risk of “Teflon
flu” due to inhalation of fumes during typical kitchen use is minimal.
Ingestion of PTFE is not reported to be toxic and residual PFOA in PTFE-coated
pans is minimally transferred to food. However, long-term exposure studies to
PTFE-fumes and PFOA have not been conducted so we can’t say that it is completely
safe. Regardless, you should keep Larry the bird away from the kitchen.
If you wish
to avoid the Teflon risk altogether, stainless steel and cast-iron pans are
recommended alternative, albeit not necessarily non-stick, cooking options.
Polytetrafluoroethylene (PTFE)
is a synthetic fluoropolymer of tetrafluoroethylene that
has numerous applications. The best known brand name of PTFE-based formulas is Teflon by Chemours.[2] Chemours
is a spin-off of DuPont Co.,[3] which
discovered the compound in 1938.[2]
PTFE is a fluorocarbon solid,
as it is a high-molecular-weight compound
consisting wholly of carbon and fluorine. PTFE
is hydrophobic:
neither water nor water-containing substances wet PTFE, as fluorocarbons
demonstrate mitigated London dispersion forces due to
the high electronegativity of
fluorine. PTFE has one of the lowest coefficients of friction of any
solid.
PTFE is used as a non-stick coating
for pans and other cookware. It is
very non-reactive, partly because of the strength of carbon–fluorine bonds, and so it is often used in
containers and pipework for reactive and corrosive chemicals. Where used as a lubricant, PTFE
reduces friction, wear and energy consumption of machinery. It is commonly used
as a graft material in surgical interventions. Also, it is frequently employed
as coating on catheters; this
interferes with the ability of bacteria and other infectious agents to adhere
to catheters and cause hospital-acquired infections.
PTFE was accidentally discovered in 1938 by Roy
Plunkett while
he was working in New Jersey for DuPont. As Plunkett attempted to make a new chlorofluorocarbon refrigerant,
the tetrafluoroethylene gas in
its pressure bottle stopped flowing before the bottle's weight had dropped to
the point signaling "empty." Since Plunkett was measuring the amount
of gas used by weighing the bottle, he became curious as to the source of the
weight, and finally resorted to sawing the bottle apart. He found the bottle's
interior coated with a waxy white material that was oddly slippery. Analysis
showed that it was polymerized perfluoroethylene, with the iron from the inside
of the container having acted as a catalyst at high pressure. Kinetic Chemicals
patented the new fluorinated plastic (analogous to the already known polyethylene) in
1941,[4] and
registered the Teflon trademark in 1945.[5][6]
By 1948, DuPont, which founded Kinetic Chemicals in partnership
with General
Motors, was producing over two million pounds (900 tons) of Teflon
brand PTFE per year in Parkersburg, West Virginia.[7] An
early use was in the Manhattan
Project as a
material to coat valves and seals in the pipes holding highly reactive uranium hexafluoride at the
vast K-25 uranium
enrichment plant
in Oak Ridge, Tennessee.[8]
In 1954, the wife of French engineer Marc Grégoire urged him to
try the material he had been using on fishing tackle on her cooking pans. He
subsequently created the first Teflon-coated, non-stick pans under the
brandname Tefal (combining
"Tef" from "Teflon" and "al" from aluminum).[9] In the
United States, Marion A. Trozzolo, who had been using the
substance on scientific utensils, marketed the first US-made Teflon-coated pan,
"The Happy Pan", in 1961.[10]
However, Tefal was not the only company to utilize PTFE in
nonstick cookware coatings. In subsequent years, many cookware manufacturers
developed proprietary PTFE-based formulas, including Swiss Diamond International, which
uses a diamond-reinforced PTFE formula;[11]Scanpan,
which uses a titanium-reinforced PTFE formula;[12] and
both All-Clad[13] and Newell
Rubbermaid's Calphalon, which use a non-reinforced PTFE-based nonstick.[14] Other
cookware companies, such as Meyer
Corporation's Anolon, use Teflon[15] nonstick
coatings purchased from DuPont.
In the 1990s, it was found that PTFE could be radiation cross-linked above
its melting point in an oxygen-free environment.[16] Electron beam processing is one
example of radiation processing. Cross-linked PTFE has improved
high-temperature mechanical properties and radiation stability. This was
significant because, for many years, irradiation at ambient conditions has been
used to break down PTFE for recycling.[17] This
radiation-induced chain
scission allows
it to be more easily reground and reused.
n F2C=CF2 → −(F2C−CF2)n−
Because tetrafluoroethylene can explosively decompose to
tetrafluoromethane and carbon, special apparatus is required for the
polymerization to prevent hot spots that might initiate this dangerous side
reaction. The process is typically initiated with persulfate, which homolyzes to generate
sulfate radicals:
[O3SO−OSO3]2− ⇌ 2 SO4•−
The resulting polymer is terminated with sulfate
ester groups, which can be hydrolyzed
to give OH end-groups.[18]
Because PTFE is poorly soluble in almost all solvents, the
polymerization is conducted as an emulsion in water. This process gives a
suspension of polymer particles. Alternatively, the polymerization is conducted
using a surfactant such as PFOS.
PTFE is a thermoplastic polymer, which
is a white solid at room temperature, with a density of about 2200 kg/m3.
According to DuPont, its melting point is 600 K (327 °C;
620 °F).[19] It
maintains high strength, toughness and self-lubrication at low temperatures
down to 5 K (−268.15 °C; −450.67 °F), and good flexibility at
temperatures above 194 K (−79 °C; −110 °F).[20]PTFE
gains its properties from the aggregate effect of carbon-fluorine bonds, as do all fluorocarbons. The
only chemicals known to affect these carbon-fluorine bonds are highly reactive
metals like the alkali
metals, and at higher temperatures also such metals as aluminium and
magnesium, and fluorinating agents such as xenon
difluoride and cobalt(III) fluoride.[21]
Property
|
Value
|
Density
|
2200 kg/m3
|
600 K
|
|
0.5 GPa
|
|
23 MPa
|
|
Bulk resistivity
|
|
Coefficient of friction
|
0.05–0.10
|
ε = 2.1, tan(δ) < 5(-4)
|
|
Dielectric constant (60 Hz)
|
ε = 2.1, tan(δ) < 2(-4)
|
60 MV/m
|
The coefficient of friction of
plastics is usually measured against polished steel.[26] PTFE's
coefficient of friction is 0.05 to 0.10,[19] which
is the third-lowest of any known solid material (BAM being
the first, with a coefficient of friction of 0.02; diamond-like carbon being
second-lowest at 0.05). PTFE's resistance to van der Waals forces means
that it is the only known surface to which a gecko cannot stick.[27] In
fact, PTFE can be used to prevent insects climbing up surfaces painted with the
material. PTFE is so slippery that insects cannot get a grip and tend to fall
off. For example, PTFE is used to prevent ants climbing out of formicaria.
Because of its chemical inertness, PTFE cannot be cross-linked like an elastomer.
Therefore, it has no "memory" and is subject to creep. Because of its superior chemical and thermal properties, PTFE
is often used as a gasket material. However, because of the propensity to
creep, the long-term performance of such seals is worse than for elastomers
which exhibit zero, or near-zero, levels of creep. In critical applications, Belleville
washers are
often used to apply continuous force to PTFE gaskets, ensuring a minimal loss
of performance over the lifetime of the gasket.
The major application of PTFE, consuming about 50% of
production, is for wiring in aerospace and computer applications (e.g. hookup
wire, coaxial cables). This application exploits the fact that PTFE has
excellent dielectric properties.
This is especially true at high radio
frequencies, making it suitable for use as an insulator in cables and connector assemblies
and as a material for printed circuit boards used at microwave frequencies.
Combined with its high melting temperature, this makes it the material of
choice as a high-performance substitute for the weaker and lower-melting-point polyethylene commonly
used in low-cost applications.
In industrial applications, owing to its low friction, PTFE is
used for applications where sliding action of parts is needed: plain
bearings, gears, slide
plates, etc. In these applications, it performs significantly better
than nylon and acetal; it is comparable to ultra-high-molecular-weight
polyethylene (UHMWPE).
Although UHMWPE is more resistant to wear than PTFE, for these applications,
versions of PTFE with mineral oil or molybdenum disulfide embedded
as additional lubricants in its
matrix are being manufactured. Its extremely high bulk resistivity makes it
an ideal material for fabricating long-life electrets, useful
devices that are the electrostatic analogues
of magnets.
PTFE film is also widely used in the production of carbon fiber
composites as well as fiberglass composites, notably in the aerospace industry.
PTFE film is used as a barrier between the carbon or fiberglass part being
built, and breather and bagging materials used to incapsulate the bondment when
debulking (vacuum removal of air from between layers of laid-up plies of
material) and when curing the composite, usually in an autoclave. The PTFE,
used here as a film, prevents the non-production materials from sticking to the
part being built, which is sticky due to the carbon-graphite or fiberglass
plies being pre-pregnated with bismaleimide resin. Non-production materials
such as Teflon, Airweave Breather and the bag itself would be considered F.O.D.
(foreign object debris/damage) if left in layup.
Because of its extreme non-reactivity and high temperature
rating, PTFE is often used as the liner in hose assemblies, expansion joints, and in industrial pipe lines,
particularly in applications using acids, alkalis, or other chemicals. Its
frictionless qualities allow improved flow of highly viscous liquids, and for
uses in applications such as brake hoses.
Gore-Tex is a
material incorporating a fluoropolymer membrane with micropores. The roof of
the Hubert H. Humphrey Metrodome in Minneapolis, US,
was one of the largest applications of PTFE coatings. 20 acres (81,000 m2) of the
material was used in the creation of the white double-layered PTFE-coated
fiberglass dome.
Other[edit]
PTFE (Teflon) is best known for its use in coating non-stick frying
pans and other cookware, as it is hydrophobic and
possesses fairly high heat resistance.
PTFE
tapes with pressure-sensitive adhesive backing
Niche[edit]
PTFE is a versatile material that is found in many niche
applications:
·
It can be stretched to contain small pores of varying sizes and
is then placed between fabric layers to make a waterproof, breathable fabric in
outdoor apparel.[30]
·
It is used widely as a fabric protector to repel stains on
formal school-wear, like uniform blazers.[31]
·
It is used as a film interface patch for sports and medical
applications, featuring a pressure-sensitive adhesive backing, which is
installed in strategic high friction areas of footwear, insoles, ankle-foot orthosis, and other medical devices to
prevent and relieve friction-induced blisters, calluses and foot ulceration.[32]
·
Expanded PTFE membranes have been used in trials to assist trabeculectomy surgery to treat glaucoma.[33]
·
Powdered PTFE is used in pyrotechnic compositions as an oxidizer with powdered metals such as aluminium and magnesium. Upon
ignition, these mixtures form carbonaceous soot and the corresponding metal fluoride, and
release large amounts of heat. They are used in infrared decoy flares and as igniters for solid-fuel
rocket propellants.[34] Aluminium and PTFE is also used in some thermobaric fuel
compositions.
·
In optical radiometry, sheets
of PTFE are used as measuring heads in spectroradiometers and broadband
radiometers (e.g., illuminance meters
and UV radiometers) due to
PTFE's capability to diffuse a transmitting light nearly perfectly. Moreover,
optical properties of PTFE stay constant over a wide range of wavelengths, from
UV down to near infrared. In
this region, the relation of its regular transmittance to diffuse transmittance
is negligibly small, so light transmitted through a diffuser (PTFE sheet) radiates like Lambert's cosine law. Thus PTFE enables
cosinusoidal angular response for a detector measuring the power of optical
radiation at a surface, e.g. in solar irradiance measurements.
·
Certain types of bullets are coated with PTFE to reduce wear on
firearms's rifling that harder projectiles would cause. PTFE itself does not
give a projectile an armor-piercing property.[35]
·
Its high corrosion resistance makes PTFE useful in laboratory
environments, where it is used for lining containers, as a coating for magnetic
stirrers, and as tubing for highly corrosive chemicals such as hydrofluoric
acid, which will dissolve glass containers. It is used in containers
for storing fluoroantimonic acid,
a superacid.[36]
·
PTFE tubes are used in gas-gas heat exchangers in gas cleaning
of waste incinerators. Unit power capacity is typically several megawatts.
·
PTFE is widely used as a thread
seal tape in
plumbing applications, largely replacing paste thread dope.
·
PTFE membrane filters are among the most efficient industrial
air filters. PTFE-coated filters are often used in dust collection systems to collect particulate
matter from air
streams in applications involving high temperatures and high particulate loads
such as coal-fired power plants, cement production and steel foundries.[37]
·
PTFE grafts can be used to bypass stenotic arteries in peripheral vascular disease if a
suitable autologous vein graft is not available.
·
Many bicycle lubricants contain PTFE and are used on chains and
other moving parts.
·
PTFE can also be used for dental
fillings, to isolate the contacts of the anterior tooth so the filling
materials will not stick to the adjacent tooth.[38][39]
·
PTFE sheets are used in the production of butane
hash oil due to
its non-stick properties and resistance to non-polar solvents.
SAFETY
Pyrolysis of PTFE
is detectable at 200 °C (392 °F), and it evolves several fluorocarbon gases
and a sublimate. An
animal study conducted in 1955 concluded that it is unlikely that these
products would be generated in amounts significant to health at temperatures
below 250 °C (482 °F).[41]
While PTFE is stable and nontoxic at lower temperatures, it
begins to deteriorate after the temperature of cookware reaches about
260 °C (500 °F), and decomposes above 350 °C (662 °F).[42] The
degradation by-products can be lethal to birds,[43] and can
cause flu-like
symptoms[44] in
humans—see polymer fume fever.
Meat is usually fried between 204 and 232 °C (399 and
450 °F), and most oils start to smoke before
a temperature of 260 °C (500 °F) is reached, but there are at least
two cooking oils (refined safflower
oil at 265 °C (510 °F) and avocado
oil at 271 °C (520 °F)) that
have a higher smoke
point.
The Environmental Working Group recommends
against using dental floss made with PTFE. [45] They
state that "Exposure to PFCs has
been associated with kidney and testicular cancer, high cholesterol, abnormal
thyroid hormone levels, pregnancy-induced hypertension and preeclampsia,
obesity and low birth weight . . . . PFCs pollute water, are persistent in the
environment and remain in the body for years. Leading manufacturers of PFCs
have agreed to phase out some of these chemicals by the end of 2015, including
PFOA, the most notorious, which used to be a key ingredient in making Teflon.
Unfortunately, there’s no evidence that the chemicals that have replaced PFOA
are much safer."
PFOA
Perfluorooctanoic acid (PFOA, or C8) has been used as a surfactant in the emulsion polymerization of
PTFE, although several manufacturers have entirely discontinued its use. PFOA
persists indefinitely in the environment. It is a toxicant and carcinogen in animals.
PFOA has been detected in the blood of more than 98% of the general US
population in the low and sub-parts
per billion range,
and levels are higher in chemical plant employees and surrounding
subpopulations. The general population has been exposed to PFOA through massive
dumping of C8 waste into the ocean and near the Ohio River Valley.[46][47] PFOA
has been detected in industrial waste, stain resistant carpets, carpet cleaning
liquids, house
dust, microwave
popcorn bags, water, food and Teflon cookware.
As a result of a class-action lawsuit and community settlement
with DuPont, three epidemiologists conducted
studies on the population surrounding a chemical plant that was exposed to PFOA
at levels greater than in the general population. The studies concluded that
there was probably an association between PFOA exposure and six health
outcomes: kidney cancer, testicular cancer, ulcerative colitis, thyroid disease,
hypercholesterolemia (high cholesterol), and pregnancy-induced hypertension.[48]
Similar Polymer
The Teflon trade name is also used for other polymers with
similar compositions:
These retain the useful PTFE properties of low friction and
nonreactivity, but are more easily formable. For example, FEP is softer than
PTFE and melts at 533 K (260 °C; 500 °F); it is also highly
transparent and resistant to sunlight
No comments:
Post a Comment
Note: only a member of this blog may post a comment.