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Overview
Triclosan is an antimicrobial agent present in consumer products such as antibacterial soaps and detergents. The United States uses roughly 1500 kg of Triclosan per day or 547,500 kg year round. Although about 90-98% Triclosan is removed from water supply through waste water treatment plants it is estimated only about 50% of Triclosan is degraded during treatment. Wastewater treatment plants are not specifically designed for removal of organic compounds such as detergents and personal care products. Triclosan was found in 57.6% of US streams out of 139 surveyed and it is one of the most frequently detected pollutants. Currently Triclosan is not classified as being toxic to humans; however, the EPA and FDA have come together in their research of Triclosan in attempts to better understand the toxic impact it may have on both the environment and humans. Certain byproducts of Triclosan such as chloroform and 2,8-dichlorooxanthane (dioxin) are already known to have a considerable toxic effect.

Chloroform Production
About 70% of all US drinking water uses free chlorine as a disinfectant residual. Free chlorine is the driving force behind chloroform production when introduced to Triclosan :

Triclosan + Free Chlorine and HOCl →4,5-dichloro-2-(2,4-dichlorophenoxy)Phenol (Triclosan Ring Cleavage + Chlorine substitution) → chloroform

High enough chlorine concentrations cause chlorine substitutions to take place in the Triclosan molecule, eventually leading to a ring cleavage of Triclosan, and the production of chloroform. Chloroform is classified as a probable human carcinogen, cancer-causing agent. Tap water not introduced to Triclosan contamination has been found to contain 0.65 mg of chloroform per year; tap water that has been contaminated contains anywhere from 6.8-28 mg per year.

Dioxin Production
Triclosan has the ability to produce several types of polychlorinated dibenzo-p-dioxins (2,8 DCDD) from exposure to sunlight:

Triclosan + H+ and sunlight → 2,8 DCDD

Triclosan converts to 2,8-DCDD (2,8-dichlorooxanthane) when irradiated under UV light in aqueous alkaline solutions. The resulting byproduct, 2,8-DCDD, is a known carcinogen. Cetrimonium bromide (CTAB) is a surfactant that can be present in the water supply and when present along with Triclosan it promotes dioxin synthesis. When CTAB is present there is a 3.89% yield of dioxin; when it is not present there is a 0.54% yield of dioxin.

Environmental Impact
Up to 50% of Triclosan remains unchanged by aerobic and anaerobic digestion in a typical wastewater facility. A large percent of it will then get trapped in sludge at the bottom of the treatment tanks and sludge is widely used to fertilize pastures, forests, and human food crops. It is estimated more than 100,000 pounds of Triclosan are spread on the ground through sludge every year in the United States. Degradation of Triclosan is typically done through photolysis instead of hydrolysis, which it is stable against, and it accounts for most of Triclosan's loss in soil and surface water. The typical half life of Triclosan is aerobic soil is 18 days and in anaerobic soils there is not a significant loss of it in 70. The difference in aerobic and anaerobic soil half life can be attributed to biodegradation since this is a major process in aerobic conditions and not anaerobic. Triclosan also has a detrimental effect in sandy soil to nitrification at concentrations at or exceeding 5 mg/kg. Triclosan is very toxic to algae and has an impact on algae growth at that current level of pollution. Algae's lowest no-observed-effect-concentration is less than 1 microgram per liter and the estimated concentration of Triclosan in United States wastewater effluents is between 0.2-2.7 microgram/Liter.

Presence in Humans
Effects of Triclosan ingestion by humans is not fully understood however there has been indications of its presence impacting allergies, disrupting the endocrine system, and the possible production of antibiotic-resistant bacteria. In 2004 the CDC measured the presence of Triclosan in urine and nearly 75% of urine samples surveyed contained Triclosan. In 2003-2004 the Triclosan concentration in urine was 12.7 ppm, and in 2005-2006 the concentration rose to 18.5 ppm, marking an increase of 45%. In a study in Sweden 3 out of the 5 women surveyed contained what is considered high levels of Triclosan in their breast milk with one being as high as 300 microgram per kilogram of lipid weight.