Triclosan is an antibacterial and antifungal agent that has
been used in the hospital setting since the 1970s. In the last decades,
triclosan has increasingly been added to household products including hand
soaps and wipes, body washes, and toothpastes. It is now even found in some
products that consumers may not be aware of, including toys. The safety and
efficacy of triclosan has been debated for years, but this last year saw major
milestones. In 2014, Minnesota became the first state in U.S. to ban triclosan
in soaps and several major companies, including Johnson & Johnson announced
they would phase out triclosan from their products. In a 2010 consumer report,
the FDA said that there was no evidence that triclosan was hazardous to humans,
yet a 2013 consumer report cited an FDA microbiologist, “the risks associated
with long-term, daily use of antibacterial soaps may outweigh the benefits
(1,2)”. The FDA is currently evaluating its regulations on triclosan and is set
to make a final decision in 2016.
The controversy surrounding triclosan is really on three
levels: what the compound does to bacteria, possibly creating antibiotic
resistance, what it does to humans when they ingest or absorb triclosan through
the skin, and finally, what it does to the environment. The latest research on
each front is presented here.
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1. Effect on
microbes:
The microbes that could be affected by triclosan-containing
products include the bacteria on your hands, in your household or environment,
and those inside of you, which make up the microflora.
The late 1990s, early 2000s saw a drastic increase in the
number of publications on antibiotic-resistance and triclosan. While there are
discrepancies in the literature, the field is generally in agreement that
triclosan use at the levels found in consumer products selects for and promotes
triclosan resistant bacteria in the gut or on skin, including Salmonella enterica, E. coli and the MRSA-causing
opportunistic bacteria, Staphylococcus
aureus (7).
The FDA concluded in 1997 that triclosan in toothpaste was
safe and effective at preventing gingivitis (1). However, questions have since
arisen as toothpaste accounts for the greatest amount of ingested triclosan in
humans. Many studies support the claim for reduced gingivitis and show that
dental plaque bacteria do not become resistant to the triclosan even with nearly
two decades use in toothpaste (3-6). But beyond fighting gingivitis, the FDA
has not found any other health benefits of using triclosan-containing products,
reporting that there was no “evidence that triclosan in antibacterial soaps and
body washes provides any benefit over washing with regular soap and water (1).”
Last year, Syed et al.
reported that triclosan was present in the nasal secretions of 50% of healthy
adults. Triclosan levels were positively correlated with colonization by S. aureus, which is a risk factor for
other infections. Rats given triclosan were more likely to have nasal
infections by S. aureus.
Intriguingly, the authors concluded that triclosan appears to induce changes in
the bacteria that increase binding to surfaces such as host cells (8).
2. Effect on human
physiology:
Triclosan is absorbed through the skin with topical use and
through the GI tract and oral mucosa when ingested. Triclosan is detectable in
most people, through serum, milk, and urine (9, 10). Triclosan binds the human
estrogen receptor, though weakly (11) and it is thought that triclosan may act
an endocrine disruptor, causing hormonal changes that could lead to cancer.
Several studies have linked triclosan to thyroid and liver dysfunction in mice
or rats (12, 13). However the concentrations used were several orders of
magnitude higher than to what humans are exposed. Epidemiological studies on
human populations have not provided evidence that triclosan poses a health risk
through endocrine disruption (14). However a recent study looked at the effects
of low levels of triclosan (based on those found in humans) on mammary gland
development in rats. While there was no effect on rats that have never given birth,
those that had given birth experienced changes to their mammary glands, with
decreased lactation and changes in gene expression (15). Therefore, further
testing is required to understand the real threat posed to humans by long-term
triclosan exposure.
3. Environmental
effects:
Of note, the EPA and FDA have begun working together in evaluating
the risks of triclosan. While most triclosan is removed at wastewater treatment
facilities, significant amounts still end up in water sources and have been
found in fish (16-18). Recent studies in natural water sources near urban
populations, where triclosan levels are the highest, showed a correlation
between triclosan levels and resistance of bacteria to triclosan Artificial
stream experiments, where experimental factors are more controlled, backed up
the findings and found that triclosan exposure was toxic to algae and led to a
dramatic increase in cyanobacteria, indicating large changes in the stream
ecosystem (16). Other studies found changes in the populations of phytoplankton,
a key player in water ecosystems, including decreased photosynthesis with
triclosan exposure (17, 18).
Though more studies are needed to understand the full risks
posed by low level exposure to triclosan, it is likely that public opinion will
go the way of bisphenol A. As for now the safest bet is to use regular soap for
hand washing and triclosan-containing toothpastes only if recommended by your
dentist.
References:
1. FDA Consumer Health Information (2010). Triclosan: What Consumers Should Know
<http://www.fda.gov/forconsumers/consumerupdates/ucm205999.htm>.
Accessed Jan 1, 2015.
2. FDA For Consumers. (2013). FDA Taking Closer Look at 'Antibacterial' Soap. < http://www.fda.gov/forconsumers/consumerupdates/ucm378393.htm>.
Accessed Jan 1 2015.
3. Haraszthy, VI., et
al. (2014). Community-level assessment of dental plaque bacteria
susceptibility to triclosan over 19 years. BMC Oral Health. 14:6.
4. Cullinan, M.P., et
al. (2013). No evidence of triclosan-resistant bacteria following long-term
use of triclosan-containing toothpaste. J Periodontal Res.
doi:10.1111/jre.12098.
5. Niederman, R. (2005). Triclosan-containing toothpastes
reduce plaque and gingivitis. Evid Based Dent. 6:33.
6. Davies, R.M., et
al. (2004). The effectiveness of a toothpaste containing triclosan and
polyvinyl-methyl ether maleic acid copolymer in improving plaque control and
gingival health: a systematic review. J Clin Periodontol. 31:1029–1033.
7. Yazdankhah, S.P., et
al. (2005). Triclosan and Antimicrobial Resistance in Bacteria:
An Overview. Microb Drug Resis. 12: 83-91.
8. Syed, A.K. et al.
(2014). Triclosan Promotes Staphylococcus aureus Nasal Colonization. mBio. 15: e01015-13.
9. Calafat, A.M., et
al. (2008). Urinary concentrations of triclosan in the U.S. population:
2003–2004. Environ. Health Perspect. 116:303–307.
10 – Allmyr, M. et al..
(2006). Triclosan in plasma and milk from Swedish nursing mothers and their
exposure via personal care products. Sci. Total Environ. 372:87–93.
11. Ahn, K.C., et al.
(2008). In vitro biologic activities of the antimicrobials triclocarban, its
analogs, and triclosan in bioassay screens: receptor-based bioassay screens.
Environ. Health Perspect. 116:1203–1210.
12. Yueh, M.F., et al.
(2014). The commonly used antimicrobial additive triclosan is a liver tumor
promoter. PNAS. 111: 17200–17205.
13. Halden, R. (2014). On the Need and Speed of Regulating Triclosan and Triclocarban in the United States. Environ. Sci. Technol. 48: 3603-3611.
14. Witorsch, R. (2014). Critical analysis of endocrine
disruptive activity of triclosan and its relevance to human exposure through
the use of personal care products. Crit Rev Toxicol. 44: 535–555.
15. Manservisi F., et al. (2014). Effect of maternal exposure to endocrine disrupting chemicals on reproduction
and mammary gland development in female sprague-dawley rats. Reprod Tox.
http://dx.doi.org/10.1016/j.reprotox.2014.12.013.
16. Drury, B., et al.
(2013). Triclosan exposure increases triclosan resistance and influences
taxonomic composition of benthic bacterial communities. Environ. Sci. Technol.
47:8923–8930.
17. Ricarta, M., et
al. (2010). Triclosan
persistence through wastewater treatment plants and its potential toxic effects
on river biofilms. Aquatic Tox. http://dx.doi.org/10.1016/j.aquatox.2010.08.010.
18. Pomati, F. and L. Nizzetto. (2013). Assessing
triclosan-induced ecological and trans-generational effects in natural
phytoplankton communities: a trait-based field method. Ecotoxicology. 22:
779-94.