WebMD Medical News
Louise Chang, MD
Jan. 21, 2010 -- A chemical compound used to make non-stick cookware, food
wrappers, and water-resistant coatings for carpets and fabrics has been linked
to an increased risk for thyroid disease in an early study.
Perfluorooctanoic acid (PFOA) has previously been shown to influence thyroid
hormone levels in animals.
But the newly reported study is among the first to suggest that exposure to
PFOA might cause thyroid disease in humans.
The study included nearly 4,000 adults who took part in the CDC’s ongoing
nationwide Health and Nutrition Examination (NHANES) study between 1999 and
Researchers found that participants who had the highest levels of PFOA in
their blood also had the highest self-reported incidence of thyroid
Specifically, women with the top 25% of PFOA concentrations were more than
twice as likely to report taking drugs for thyroid disease as the 50% of
participants with the lowest concentrations. A similar trend was seen in men,
although it didn’t reach statistical significance.
The study does not prove that PFOA exposure is a direct cause of thyroid
disease, researcher David Melzer, PhD, of Peninsula Medical School in Exeter,
England, tells WebMD.
“I personally am far from sure, but it might prove to be an important risk
factor for people who are already susceptible,” he says.
PFOA, also known as C8, and the related chemical perfluorooctane sulphonate
(PFOS) are used by companies like DuPont and 3M in the manufacture of a range
of products, including Teflon, Stainmaster, and Scotchgard.
Concerns have been raised about the man-made chemicals because they are now
found in low levels in the environment and in the blood of most people and they
remain in the blood for many years.
It is not clear how PFOA gets into the blood. Manufacturers claim their
products do not contain it or contain only trace amounts of the chemicals.
The Environmental Protection Agency (EPA) is investigating the compound, but
at present it considers the routine use of consumer products made with it to be
In 2006, the EPA and eight major companies, including DuPont and 3M, agreed
to work to eliminate global emissions of PFOA and related compounds by
A spokeswoman for DuPont tells WebMD the company has reduced PFOA emissions
at its manufacturing sites worldwide by about 98% since that time, exceeding
the interim target of 95% emission reduction by this year.
In response to the latest study, Janet Smith of DuPont points to research in
communities with high PFOA exposures that show little or no impact on the
“As the authors of the study indicated, it is not clear whether the
associations they observed are causal,” she says. “Epidemiological studies
involving workers who have had much higher levels of PFOA exposure than the
general public haven’t shown any changes that would indicate impact on the
Thyroid disease is much more common in women than in men. But the
researchers found no evidence of a statistically different effect of PFOA
exposure in women and men.
They did find a link between thyroid disease and higher concentrations of
PFOS in men, but not in women.
Previous studies examining people living in communities where PFOA and PFOS
are manufactured have shown little association between exposure to the chemical
and thyroid hormone functioning.
But findings from the largest-ever study of PFOA exposure have not yet been
In the ongoing C8 Study, researchers measured PFOA levels and health
outcomes among nearly 70,000 residents of West Virginia who drank water
contaminated with PFOA.
The study is funded by a $107 million lawsuit settlement agreed to by DuPont
Preliminary findings suggest high PFOA levels may be linked to high blood
pressure, high cholesterol, and impaired liver function.
University of Massachusetts thyroid researcher Thomas Zoeller, PhD, tells
WebMD that thyroid disease is increasing, but the reasons for this remain
“There is almost certainly an environmental component to this, but we don’t
know what that environmental component is,” he says.
He says PFOA and PFOS may be environmental triggers, but this remains to be
And because it is not clear how people become exposed, there is no easy
message for reducing exposure to these chemical compounds, he says.
“Right now, I don’t think we have the ability to know what kind of exposures
we are getting and where it is coming from,” he says.
SOURCES:Galloway, T., Environmental Health Perspectives, Jan. 21, 2010;
online edition.David Melzer, PhD, Peninsula Medical School Epidemiology and Public Health
Group, Exeter, England.Thomas Zoeller, PhD, professor of biology, University of Massachusetts at
Amherst.Janet Smith, spokeswoman, DuPont.News release, Environmental Health Perspectives.News release, The Peninsula College of Medicine and Dentistry.Environmental Protection Agency: “PFOA and Fluorinated Telomers.”
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