[Pharmwaste] Can toothpaste containing triclosan harm your thyroid?
dldebiasi at deq.virginia.gov
Fri Dec 5 11:42:09 EST 2008
Can toothpaste harm your thyroid?
Dec 05, 2008
Zorrilla LM, EK Gibson, SC Jeffay, KM Crofton, WR Setzer, RL Cooper and
TE Stoker. 2008.
The effects of triclosan on puberty and thyroid hormones in male wistar
Toxicological Sciences doi:10.1093/toxsci/kfn225.
Synopsis by Heather Hamlin and Wendy Hessler
Triclosan, an antibacterial agent used in toothpastes, soaps and
cosmetics, alters thyroid function in male rats, highlighting a
potential concern for people - especially pregnant women and children.
Effects occurred at doses that people may experience, given the many
diverse sources of exposure now prevalent because of triclosan's
Triclosan is an antibacterial ingredient found in many common household
products, including toothpaste, mouthwash, soap, deodorant, shaving
cream and cleaning supplies. Triclosan is slowly increasing its resume,
as manufacturers add it to a wider range of consumer products, such as
kitchen utensils, trash bags, clothing, bedding and even children's
toys. Today it is virtually unavoidable.
Chemically, triclosan is a chlorinated, organic molecule that resembles
the synthetic plastic additive bisphenol A (BPA) and the long-lived
dioxins, which are formed during incomplete burning and can cause
cancer. In fact, heat and sunlight can transform triclosan into dioxins
(Kanetoshi et al. 1987).
Because triclosan is in soaps and other products that are continually
flushed down drains, it commonly enters the environment. It has been
found at appreciable concentrations in wastewater effluent and surface
Triclosan can also bioaccumulate in fish and amphibians. The
antimicrobial can alter how their hormones function, including the
thyroid hormone system.
Thyroid hormones play an important role regulating metabolism and during
early development in many animals, including humans. Metabolism refers
to the way cells use or store energy to maintain life. Food is broken
down to create the energy used to grow or maintain tissue.
The thyroid gland makes and stores thyroid hormones. Spaces in the gland
are filled with a substance called colloid. The colloid is rich in the
raw materials that are needed to make thyroid hormones. It also serves
as a reservoir for the hormones themselves.
Thyroid hormones contain iodine, which can be found in many foods. There
are two primary thyroid hormones, thyroxine (T4) and triiodothyronine
(T3). Generally speaking, T4 is present at higher concentrations than
In amphibians, thyroid hormones coordinate the metamorphosis of tadpoles
into frogs. Laboratory studies find that triclosan interferes with this
important transition and has other harmful effects in animals.
Metamorphosis was altered in bullfrog tadpoles that were exposed to low
concentrations of triclosan. The levels were 15 times lower than what
the US Food and Drug Administration has reported in rivers across the
United States (Hua et al. 2005).
Low concentrations of triclosan can also alter the genes responsible for
producing thyroid hormones (Veldhoen et al. 2006). Other reported
effects in fish and amphibians exposed to the antimicrobial include
changes in activity level, behavior, sex-ratios, body mass and
survivorship (Fraker and Smith 2004).
What did they do?
Newly weaned male rats were fed an oral dose of triclosan of either 0,
3, 30, 100, 200 or 300 mg/kg body weight. The rats were given the
triclosan daily for 31 days.
The purpose of the experiment was to determine what effects triclosan
would have on concentrations of thyroid hormones and the onset of
puberty. Preputial separation (PPS), a separation of the foreskin from
the glans penis, was used to measure puberty development.
Researchers measured blood concentrations of testosterone and several
other types of hormones and weighed a variety of organs that are
essential for rat development and puberty, including the pituitary
gland, the testes, the prostate gland and the liver.
Liver enzymes were measured to gauge liver function, and the colloid
region of the thyroid gland was examined.
What did they find?
There was a dramatic decrease in the thyroid hormone thyroxine (T4) in
rats exposed to increasing concentrations of triclosan. Thyroxine was
decreased by 47% at the 30 mg/kg dose and by 81% at the 300 mg/kg dose.
There was not a significant difference in thyroxine at the 3 mg/kg dose.
Significant increases in liver weights were seen from the 100 mg/kg to
the 300 mg/kg triclosan doses, although certain liver enzymes were not
significantly different among groups. The pituitary weights were heavier
at the 3 and 300 mg/kg exposure. Other measured organs were not
significantly different in weight.
The colloid area of the thyroid gland was smaller in the 300 mg/kg dose
group when compared to all other groups.
What does it mean?
Exposure to triclosan dramatically decreased thyroxine concentrations in
young male rats. The hormone is critical for normal development and to a
properly functioning metabolism. Too much or too little can cause a wide
range of health problems before and after birth.
Hypothyroidism occurs when the thyroid produces lower than normal
amounts of hormones. The condition can lead to obesity, goiter,
infertility, neurological problems and other serious concerns. This long
list is not surprising since thyroid hormones control metabolism, which
can affect nearly every cell in the body.
The results of this study with mammals support previous research that
finds the antimicrobial can affect the thyroid hormone system in
Rats and most other vertebrates, including humans, produce and use
thyroid hormones in quite similar ways. Given that triclosan is found in
such a variety of household products and has been detected in human
blood, urine and even breast milk, this study's findings raises concern
for adverse effects on humans. Although this study used rats, the
similarities in how the thyroid systems between rats and humans function
raises concerns as to whether people could share the same physiological
One thing dissimilar in rats and humans is how much of a compound is
necessary to cause a negative result. Sometimes it takes a far greater
dose of a chemical to alter a rat's biology than it would to change a
human's. Therefore, although the concentrations evaluated in this study
were higher than normal human exposure, it is still unclear the
concentrations necessary to elicit the same effects in humans. It is
possible that the low doses that humans are currently exposed to are
enough to cause similar problems.
The colloid area of the thyroid gland was smaller in rats exposed to the
300mg/kg triclosan dose. The colloid is a repository for thyroid
hormones and stores components to make more thyroid hormone. A shrunken
colloid could indicate that thyroid levels were too low, and the rats
were releasing the reserves to bring blood hormone levels back to
normal. Using these would reduce the size of the colloid area.
Triclosan exposed rats also had bigger livers. The liver clears and
removes toxins from the body. A larger liver may indicate excessive
pressure on the liver to clear triclosan. Stressed livers enlarge to
accommodate the higher production of the enzymes needed to detoxify
If the liver accelerated its detoxifying activity in the presence of
triclosan, the increased effort could account for the lower
concentrations of thyroxine measured. The liver would have been clearing
the hormone from the system faster. However, the researchers did not
find a difference in an important toxin clearing enzyme called UDPGT.
This indicates that some other mechanism caused the reduction in thyroid
hormones. One way is that triclosan may act directly on the thyroid
gland to interfere with hormone production.
There are critical times in development when exposures can permanently
alter development. For instance, hypothyroidism during early development
can change reproductive tract development, hormone concentrations and
sexual maturation, including puberty onset. In this study, triclosan
exposure did not change the onset of puberty, suggesting that exposure
after weaning to triclosan is too late to affect the timing of puberty
The effects seen in this experiment raise significant questions about
the wisdom of allowing widespread use of triclosan in multiple consumer
Fraker, SL and GR Smith. 2004. Direct and interactive effects of
ecologically relevant concentrations of organic wastewater contaminatns
on Rana pipiens tadpoles. Environmental Toxicology 19:250-256.
Hua W, ER Bennett and RJ Letcher, 2005. Triclosan in waste and surface
waters from the upper Detroit River by liquid
chromatography-electrospray-tandem quadruple mass spectrometry.
Environment International 31:621-630.
Kanetoshi, A, H Ogawa, E Katsura and H Kaneshima. 1987. Chlorination of
Irgasan DP300 and formation of dioxins from its chlorinated derivatives.
Journal of Chromatography 389:139-153.
Singer H, S Muller, C Tixier and L Pillonel. 2002. Triclosan: occurrence
and fate of a widely used biocide in the aquatic environment: field
measurements in wastewater treatment plants, surface waters, and lake
sediments. Environmental Science and Technology 36:4998-5004.
Veldhoen N, RC Skirrow, H Osachoff, H Wigmore, DJ Clapson, MP Gunderson,
G Van Aggelen and CC Helbing, 2006. The bactericidal agent triclosan
modulates thyroid hormone-associated gene expression and disrupts
postembryonic anuran development. Aquatic Toxicology 80:217-227.
Deborah L. DeBiasi
Email: dldebiasi at deq.virginia.gov
WEB site address: www.deq.virginia.gov
Virginia Department of Environmental Quality
Office of Water Permit Programs
Industrial Pretreatment/Toxics Management Program
PPCPs, EDCs, and Microconstituents
Mail: P.O. Box 1105, Richmond, VA 23218 (NEW!)
Location: 629 E. Main Street, Richmond, VA 23219
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