How Your Sofa Can Harm Your Health
A common household chemical found in everything from sofas and carpets
to pots and pans has been linked to an increased risk of thyroid
disease, in the first major study carried out on its effect upon
The substance, used to make nonstick cookware, stain-resistant
furnishings and greaseproof wrappers, is believed to get into
the body through contaminated food or household dust. Once in
the body it accumulates in organs and other tissues.
People with high levels of the chemical in their blood were found
to be twice as likely to have thyroid problems as those with the
lowest levels, according to a survey of medical records of nearly
4,000 otherwise healthy US adults. The
study is published in the journal, Environmental Health Perspectives.
Scientists said they cannot be certain the chemical is directly
responsible for the rise in thyroid disease but called for a full
investigation to assess its safety.
acid (PFOA) is a manmade chemical known for its heat resistance
and water, grease and stain repelling properties. Manufacturers
use PFOA to make fluoropolymers, used in thousands of products.
It is turned into non-stick coatings for cookware, flame retardants
in furnishings, stain protection treatments for carpets, wire
coatings and waterproof clothing such as Gore-Tex.
Studies in animals have found that PFOA,
and a sister substance called PFOS
(perfluorooctane sulfonate), can cause thyroid problems and
a variety of other medical conditions, including hormone imbalances,
liver disease and cancer.
"It's been thought that because they're inert they don't
cause any health problems, but we're starting to see some evidence
that is suggesting that's not true," said Tamara
Galloway, professor of ecotoxicology at Exeter University.
"Because these chemicals are inert they are persistent and
they build up in the environment and also in human and animal
We all have trace levels of PFOA in our bodies that we pick up
from the environment. The substance is so stable that it persists
for years. It has been detected in people around the world and
in wildlife as diverse as birds, fish and polar bears.
The thyroid gland produces hormones that control the body's metabolism
and are vital for regulating heart rate and temperature. Thyroid
disease can make the gland produce too much or too little hormone.
An underactive thyroid can cause exhaustion, depression and weight
gain. If the gland is overactive, it can cause weight loss and
a rapid heartbeat. Women are 10 times more likely to have thyroid
problems than men.
The Exeter researchers trawled medical records on the US
National Health and Nutrition Examination Survey, a database
representative of the country's adult population. They found 3,966
people aged 20 and older whose blood had been tested for PFOA
and PFOS between 1999 and 2006.
The scientists put the patients into four groups depending on
the concentration of PFOA in their blood. The records showed that
16% of women in the top group had thyroid problems, compared with
8% in the lowest group. A similar trend was seen in men, though
the number who had thyroid disease was small.
Co-author David Melzer, professor of epidemiology and public
health at the Peninsula Medical School in Exeter, said: "There
have long been suspicions that PFOA concentrations might be linked
to changes in thyroid hormone levels. Our analysis shows that
in the ordinary adult population there is a solid statistical
link between higher concentrations of PFOA in blood and thyroid
The scientists concede that their study does not confirm PFOA
is causing thyroid disease. One alternative explanation is that
thyroid disease makes PFOA accumulate more quickly in the body.
An investigation into the health effects of PFOA is underway
in West Virginia, where thousands of people have been exposed
over decades after the chemical was released from an industrial
plant owned by the US manufacturer, DuPont. Tony Fletcher, a scientist
working on the investigation and an environmental epidemiologist
at the London School of Hygiene and Tropical Medicine, said a
full report is due next year.
The US Food and Drug Administration has a voluntary agreement
with several companies to phase out PFOA production over the next
few years. Ashley Grossman, professor of neuroendocrinology at
Queen Mary, University of London, said: "We also don't know
whether this chemical is directly affecting the thyroid. Thyroid
disease is often caused by the body's own immune system attacking
the thyroid gland, so perhaps this chemical is having some effect
on the immune system, rather than directly on the thyroid.
"We'd need to do a lot more research to verify this link
and to understand how the two are linked. In the meantime, it's
important to remember that thyroid disease can be successfully
A spokesman for the Health
Protection Agency said: "A study like this cannot establish
cause and effect. An independent scientific advisory committee
has looked at the published evidence and found no reason to suspect
the chemical causes thyroid problems."
Much used chemical.
January 22, 2010