Triclosan, sometimes called TCS, is a substance used in some consumer products like toothpaste, soaps, detergents, toys, and surgical cleaning supplies. It works similarly to another substance called triclocarban. Scientists are still studying whether Triclosan is effective as an antimicrobial, whether it might cause bacteria to become resistant to it, and whether it could affect hormone development. More research is needed to learn about its effects on living things and the environment.

Triclosan was created in 1966. A study from 2006 suggested using a 2% Triclosan solution for showering in surgical areas to remove methicillin-resistant Staphylococcus aureus (MRSA) from patients' skin.

Uses

Triclosan was used as a hospital scrub in the 1970s. Before changes in rules in the EU and US, it became widely used in products such as soaps (0.10–1.00%), shampoos, deodorants, toothpastes, mouthwashes, cleaning supplies, and pesticides. It was also found in consumer items like kitchen tools, toys, bedding, socks, and trash bags.

Triclosan was approved as a pesticide in 1969. In the US, the Environmental Protection Agency (EPA) requires registration numbers for all pesticides. By 2017, triclosan had five registrations with the EPA. Today, there are 20 antimicrobial product registrations with the EPA under the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA). Antimicrobial ingredients are added to products to slow or stop the growth of bacteria, fungi, and mildew. In commercial, institutional, and industrial equipment, triclosan is used in conveyor belts, fire hoses, dye baths, and ice-making machines. It may also be applied directly to HVAC coils to prevent microbial growth that can damage equipment.

By 2000, triclosan and triclocarban (TCC) were in 75% of liquid soaps and 29% of bar soaps in the US. By 2014, triclosan was in more than 2,000 consumer products.

In healthcare, triclosan is used in surgical scrubs and hand washes. It works best when used for about two minutes. Recently, showering with 2% triclosan has been recommended in surgical units to reduce MRSA on patients’ skin. Small studies showed triclosan use was linked to fewer MRSA infections.

Triclosan is also used in coatings for some surgical sutures. Evidence shows these sutures help reduce surgical site infections. The World Health Organization, the American College of Surgeons, and the Surgical Infection Society support the use of triclosan-coated sutures for this purpose.

Triclosan is used in molecular cloning as a tool. Bacteria with a special gene that makes them resistant to triclosan can grow in triclosan-containing media.

In surgery, triclosan-coated sutures lower the risk of infection. Some studies suggest hand soaps with triclosan remove slightly more bacteria than plain soap. By 2013, the US FDA found health benefits in some products with triclosan, but not in others, such as antibacterial soaps and body washes.

A review of 30 studies found toothpastes with triclosan reduced dental plaque and gum inflammation by 22% compared to fluoride-only toothpastes. There was weak evidence of fewer cavities and no evidence of fewer gum diseases.

A study on triclosan toothpastes found no evidence it caused serious heart problems like heart attacks. A study by Colgate-Palmolive showed reduced gum inflammation, bleeding, and plaque with triclosan toothpaste. However, a review by the Cochrane group said these effects were statistically significant but not clinically meaningful.

Triclosan is used in food storage containers, but this use is banned in the European Union since 2010.

In the EU, triclosan’s use in veterinary products is controlled by the Biocidal Products Directive.

Chemical structure and properties

This organic compound appears as a white, powdery solid with a faint, aromatic, and phenolic smell. It is classified as a polychloro phenoxy phenol, a type of chlorinated aromatic compound that contains parts of the molecule similar to both ethers and phenols. Phenols are known to have antibacterial properties. Triclosan dissolves well in ethanol, methanol, diethyl ether, and very basic solutions, such as a 1 M sodium hydroxide solution, but only slightly dissolves in water. It can be made from 2,4-dichlorophenol.

During a heating process, 2,4,4'-trichloro-2'-methoxydiphenyl ether is mixed with aluminium chloride.

The United States Pharmacopeia formulary has released a document about triclosan that outlines standards for its purity.

Mechanism of action

At high levels, triclosan acts as a substance that kills living things by targeting many parts inside and on the surface of cells. At lower levels, like those found in products sold in stores, triclosan stops bacteria from growing by mainly blocking the process of making fatty acids.

Triclosan attaches to an enzyme called enoyl-acyl carrier protein reductase (ENR), which is made by the gene fabI. This attachment helps the enzyme connect more strongly to a molecule called nicotinamide adenine dinucleotide (NAD). This creates a stable group made of ENR, NAD, and triclosan, which cannot help in making fatty acids. Fatty acids are needed to build and grow cell membranes. Animals with backbones, like humans, do not have this ENR enzyme and are not affected by this process.

Triclosan has also been found to attach to a protein called tubulin and stop it from forming structures needed for cell shape.

Triclosan is a weak substance that can interfere with hormone systems, but it is unclear how important this is for humans. It has been shown to attach weakly to both the androgen receptor and the estrogen receptor, where it can either mimic or block the effects of these hormones.

Triclosan may increase or cause bacteria to produce more efflux pumps, which help them resist many other antibiotics.

Exposure

Humans come into contact with triclosan when it is absorbed through the skin during activities like washing hands, showering, brushing teeth, using mouthwash, or doing dishes. People may also swallow triclosan accidentally. When triclosan enters the environment, it can be found in plants grown in soil treated with sewage sludge or in fish that have been exposed to it.

A study published by the American Society of Agronomy, led by Monica Mendez and others, showed that watering plants with triclosan-containing water caused the chemical to appear in all edible parts of tomato and onion plants months later. Triclosan is known to kill many types of bacteria. Researchers are also worried about its effect on the good bacteria that help maintain healthy soil.

Distribution, metabolism, and elimination

After being absorbed, triclosan is broken down by humans mainly through chemical reactions that attach other molecules, forming glucuronide and sulfate compounds. These compounds are then removed from the body through feces and urine. Studies on how the body handles triclosan show that at levels commonly found in the environment (1 to 5 microMolar), the liver produces triclosan sulfate and glucuronide at similar rates. When triclosan levels are below 1 microMolar, the primary way the body removes it is through sulfonation.

Health concerns

Because of possible health risks, such as antimicrobial resistance, endocrine disruption, and other issues, triclosan has been labeled a "contaminant of emerging concern (CEC)" by the United States Geological Survey. This means it is being studied to understand if it poses a risk to public health. "Emerging contaminants" are chemicals or microorganisms that are not commonly tracked in the environment but could enter it and harm ecosystems or human health. Triclosan may build up in wastewater and return to drinking water, leading to increasing levels that could cause more harm over time.

In the United States, after many years of studying triclosan’s health effects, the FDA made a decision on September 6, 2016. It concluded that 19 ingredients, including triclosan, are not generally recognized as safe and effective (GRAS/GRAE).

Triclosan has been linked to a higher risk of food allergies. Some research suggests that exposure to bacteria might reduce allergies, which could explain this connection, rather than triclosan’s own toxicity. This effect may also occur with other antibacterial agents, such as chlorhexidine gluconate and chloroxylenol (PCMX). Other studies have found that triclosan may cause allergic skin reactions in some people. It has also been associated with increased sensitivity to allergens like those from pollen or seasonal triggers, rather than food.

Triclosan can react with free chlorine in tap water to form other compounds, such as 2,4-dichlorophenol. Some of these compounds may turn into dioxins when exposed to sunlight or other UV sources. However, the dioxins formed from triclosan are not considered harmful to mammals, birds, or fish.

Concerns about triclosan’s health effects grew after it was found in human breast milk, blood, and urine. Studies on rats have shown that triclosan exposure affects estrogen-related processes. Many studies, both in animals and in laboratory settings, have found that triclosan can act as an anti-estrogen or anti-androgen, depending on the species, tissues, or cells involved.

Fewer human studies have examined triclosan’s effects on hormones compared to animal studies, but research is ongoing. A 2017 study of 537 pregnant women in China found that triclosan exposure during pregnancy was linked to higher testosterone levels in their infants.

History

In 1964, the Swiss company Ciba-Geigy patented Triclosan (TCS). Safety testing for Triclosan started in 1968, and it was introduced in hospitals the following year. By the early 1970s, Triclosan was being produced and used worldwide.

In 1997, Ciba-Geigy merged with Sandoz, another Swiss company, to create Novartis. During the merger, Ciba-Geigy's chemical business became Ciba Specialty Chemicals. In 2008, the chemical company BASF purchased Ciba Specialty Chemicals. BASF currently produces Triclosan under the brand name Irgasan DP300.

Environmental concerns

People are exposed to triclosan for a short time when using personal care products. When these products are thrown away, triclosan goes to sewage treatment plants. In the United States, about 97–98% of triclosan is removed during treatment. However, studies show that large amounts of triclosan (170,000–970,000 kg per year) can still escape from treatment plants and harm algae in surface water. In one study, about 75% of triclocarban, a related chemical, was found in sewage sludge. This may harm the environment, especially aquatic ecosystems. In the United States, about 44,000 kg of triclosan per year returns to the environment through sewage sludge after initial removal. Triclosan can stick to other substances in water, which may harm marine life and cause it to build up in living things. Ozone is a tool that can help remove triclosan during treatment. Plastic and textile products do not release much triclosan, so they are not major sources of contamination.

During wastewater treatment, some triclosan is broken down, while the rest sticks to sludge or leaves the plant as treated water. A study at a sewage treatment plant in Athens, Greece (2013) found that 43% of triclosan was found in sludge, 45% was broken down, and 12% was released into the environment. In nature, triclosan may be broken down by microbes or sunlight, forming other chemicals like chlorophenols and dioxins.

Between 1999 and 2000, the U.S. Geological Survey found triclosan in 57.6% of streams and rivers tested. Studies using special devices show that triclosan does not strongly build up in living things, but methyl-triclosan is more stable and dissolves better in fats, making it more likely to accumulate. The ability of triclosan to build up depends on its chemical state in different environments.

Global warming may increase how much triclosan is absorbed by aquatic organisms. Triclosan is harmful to bacteria in water and can damage algae, especially near wastewater treatment plants. It has been found in many organisms, including algae, blackworms, fish, dolphins, earthworms, and animals higher up the food chain. In tests with marine bacteria, triclosan was toxic at a level of 0.22 mg/L. Long-term effects on algae, daphnids, and fish are not well studied, but acute effects are known.

A 2017 study in European rivers found that triclosan levels could be harmful, with the risk being highest in rivers with less dilution. Triclosan works best in environments without oxygen, like soil and sediment, and it is hard to break down in these conditions.

Resistance concerns

Concern is about the possibility that using certain cleaning products, like triclosan, might lead to resistance to other medicines. Many studies have been done, and some results show that triclosan can cause resistance to other antibiotics. One study tested many types of bacteria and different kinds of antibiotics. It found that bacteria already resistant to triclosan, such as Pseudomonas aeruginosa and Stenotrophomonas maltophilia, showed more resistance to tetracycline and norfloxacin after being exposed to triclosan. Another study in The American Journal of Infection Control found that exposure to triclosan was linked to higher chances of resistance in Staphylococcus aureus and Escherichia coli. This effect was not seen when bacteria were exposed to chlorhexidine or a hydrogen peroxide-based product under the same study conditions.

Alternatives

A study published in 2007 found that in everyday situations, regular soap works just as well as soap with triclosan to help prevent illness symptoms and lower the number of germs on hands.

Other options that can be used instead of triclosan include nonorganic antibiotics and organic biocides, such as silver and copper ions and tiny particles made from these materials.

Policy

In the United States, triclosan is controlled as a pesticide by the Environmental Protection Agency (EPA) and as a drug by the Food and Drug Administration (FDA). The EPA typically oversees uses on solid surfaces, while the FDA regulates uses in personal care products.

In 1974, the FDA began reviewing "over-the-counter (OTC) topical antimicrobial products," including triclosan and triclocarban. An advisory panel first met on June 29, 1972, and the FDA published its proposed rule on September 13, 1974. The rule applied to OTC products containing antimicrobial ingredients for topical human use, such as soaps, surgical scrubs, skin washes, and first aid preparations. The proposed rule listed many products already on the market and the companies that made them.

In 1978, the FDA published a tentative final monograph (TFM) for topical antimicrobial products. The record was reopened in March 1979 to consider six comments, including new data from Procter & Gamble about triclocarban’s safety and from Ciba-Geigy about triclosan’s use. The document noted that "significant new data" had been submitted. The record was reopened again in October 1979 to allow more information about the safety, effectiveness, and labeling of OTC topical antimicrobial products.

In 1994, the FDA issued a proposed rule stating it would establish conditions for OTC topical antiseptic drug products to be generally recognized as safe and effective. The rule also asked for data about the safety and effectiveness of topical antimicrobials used in hand sanitizers. In the 1994 update, triclosan was removed from the drug category, allowing its use in consumer products.

In 2010, the Natural Resources Defense Council forced the FDA to review triclosan after suing the agency for not acting. Because the FDA had banned hexachlorophene, a compound similar to triclosan, scientists argued the FDA should also ban triclosan. On December 17, 2013, the FDA issued a draft rule revoking triclosan’s "generally recognized as safe" status in hand wash products, citing the need for more studies on its effects on hormones, development, bacterial resistance, and cancer risk.

On September 6, 2016, the FDA finalized a rule stating that 19 active ingredients, including triclosan and triclocarban, used in OTC consumer antiseptic washes are not safe or effective and are misbranded. Companies must reformulate products without these ingredients, remove them from the market, or submit a New Drug Application (NDA) within one year. The 19 ingredients include:
• Cloflucarban
• Fluorosalan
• Hexachlorophene
• Hexylresorcinol
• Iodine complex (ammonium ether sulfate and polyoxyethylene sorbitan monolaurate)
• Iodine complex (phosphate ester of alkylaryloxy polyethylene glycol)
• Methylbenzethonium chloride
• Nonylphenoxypoly (ethyleneoxy) ethanoliodine
• Phenol (greater than 1.5 percent)
• Phenol (less than 1.5 percent)
• Poloxamer -iodine complex
• Povidone-iodine 5 to 10 percent
• Secondary amyltricresols
• Sodium oxychlorosene
• Tribromsalan
• Triclocarban
• Triclosan
• Triple dye (an antiseptic for newborns)
• Undecoylium chloride iodine complex

In 2015 and 2016, the FDA proposed changes to the 1994 TFM regarding the safety and effectiveness of OTC antiseptics and rubs.

The state of Minnesota banned triclosan in consumer products before federal rules. In May 2014, the governor signed a law prohibiting the sale of triclosan-containing cleaning products for sanitizing or hand and body cleansing. The law took effect on January 1, 2017, with exceptions for FDA-approved products.

As evidence about triclosan’s health and environmental risks grew, some companies removed it from products before regulations: Colgate-Palmolive removed it from dish soap and Softsoap in 2011 (but kept it in Colgate Total toothpaste until 2018–2019); Johnson & Johnson removed it from baby products in 2012 and all products in 2015; Procter & Gamble removed it in 2014; Clearasil and Avon phased it out in 2014; and Unilever removed it from skin care and cleansing products in 2015, planning to remove it from oral care by 2017.

In Canada, triclosan is allowed in cosmetics, but Health Canada plans to review its safety soon. The Cosmetic Ingredient Hotlist limits triclosan to 0.3% in cosmetics and 0.03% in mouthwashes, with warnings to avoid swallowing and not use it for children under 12.

In Europe, triclosan was not approved by the European Commission for use in biocidal products in 2016. In the U.S., products with triclosan must list it on labels. In Europe, it is regulated as a cosmetic preservative and must be listed on labels. The EU restricted triclosan in cosmetics in 2014.