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=Triclosan=

Treatment of Triclosan in Waste
The duration of triclosan in personal product use is relatively short. Upon disposal, triclosan is washed down the drain to municipal wastewater treatment plants, where about 97-98% of triclosan is removed from the water. Studies show that substantial quantities of triclosan (170,000 – 970,000 kg/yr) can break through wastewater treatment plants and damage algae on surface waters. Discharge of effluent from these treatment plants and disposal of sludge on land is the primary route of environmental exposure to triclosan. Research shows that triclosan has been detected in sewage effluents and sludge (biosolids) due to its incomplete removal during wastewater treatment. Because of their hydrophobic nature, significant amounts of them in wastewater streams partition into sludge, with concentrations at mg/kg levels. The volume of triclosan reentering the environment in sewage sludge after initial successful capture from wastewater is 44,000 ± 60,000 kg/yr.

Incomplete removal of triclosan during wastewater treatment results in effluent and biosolids with trace amounts of triclosan. This poses a potential environmental and ecological hazard, particularly for aquatic systems. In a study on effluent from wastewater treatment facilities, approximately 75% of triclocarban was present in sludge. Triclosan can attach to other substances suspended in aquatic environments, which potentially endangers marine organisms and may lead to further bioaccumulation. Ozone is considered to be a a tool for removing triclosan during sewage treatment. Because little triclosan is released through plastic and textile household consumer products, these are not considered to be major sources of triclosan contamination.

Bioaccumulation
While studies using semi-permeable membrane devices have found that triclosan does not strongly bioaccumulate, methyl-triclosan is comparatively more stable and lipophilic and thus poses a higher risk of bioaccumulation in organisms. The ability of triclosan to bioaccumulate is affected by its ionization state in different environmental conditions. At higher pHs, triclosan is expected to bioaccumulate more. At a lower pH, methyl-triclosan is much more likely to bioaccumulate. Analysis of human autopsies have shown that triclosan can bioaccumulate in the liver and adipose tissues, but not in brain tissues.

Ecotoxicity
Triclosan and triclocarban (TCC) could have adverse repercussions on agriculture. Studies have indicated that TCC and TCS are absorbed through shoot systems in vegetables, at higher levels in roots than in tubers. While the levels of TCC and TCS in the vegetables are largely insufficient to cause major health damage, the levels of these chemicals is higher than in the drinking water supply. Crops shown to take up antimicrobials from soil include barley, meadow fescue, carrots and pinto beans. Triclosan may also affect animal wildlife behavior. For example, TCS and TCC are 100-1,000 times more effective in inhibiting and killing algae, crustaceans and fish than they are in killing microbes. TCS have been observed in multiple organisms, including algae aquatic blackworms, fish and dolphins. Earth dwelling species include earth worms, and higher species up the food chain

Endocrine Health Concerns
Triclosan has been associated with lower levels of thyroid hormone and testosterone. Specifically, triclosan decreases circulating levels of thyroxine hormone (T4) by increasing glucuronidase enzyme activity, which catabolizes T4 and other thyroid hormones. This may lead to altered behavior, learning disabilities, and/or infertility. Very low doses of triclosan have been shown to act as an estrogen mimic and increase proliferation rates of breast cancer tumors.

Breakdown of Triclosan
TCS is structurally related to highly toxic and carcinogenic dioxins. In 1993, it was labeled by the EPA as a pre-dioxin, and TCS contains traces of the most toxic member of the dioxin family, 2,3,7,8-tetrachlorodibenzo-p-dioxin. The rising concern of TCS toxicity has pushed producers of antimicrobial products to acquire TCS from European chemical supplies because the production is very tightly regulated. TCS can mix with chlorinated drinking to form of carcinogenic chloroform and, upon release into surface water and irradiation with sunlight, release additional toxic polychlorinated dioxinsand less toxic dichlorinated dioxins, e.g., 2,8-dichlorodibenzo-p-dioxin.

Policy
In light of the difficulties of finding antimicrobial alternatives, the Food and Drug Administration began in the 1970s to review the safety of triclocarban and triclosan, but no enacted policy, or "drug monograph" is available to date. Legal recourse by the Natural Resources Defense Council in 2010 forced the FDA to review triclosan. However, the United States Environmental Protection Agency maintains regulatory control over triclosan to date.

Similar in its use and its adverse health impacts as triclosan, hexachlorophene became prohibited by the FDA.

Current and Future Research
The future of TCC is unknown, but scientists are searching for more sustainable antimicrobials that maintain its antibacterial properties while being minimally toxic to the envrionment, humans, and wildlife. This entails low degrees of bioaccumulation and rapid, clean biodegredation in existing wastewater treatment facilities.A lowered potential or no potential for resistance is also preferable. These next generation chemicals should aim to act on a broad spectrum of microbes and pathogens while also being minimally toxic and bioaccumulating in non-target species.

Synthesis of these compounds could be improved upon by finding renewable sources for their production that lacks occupational hazards. Research regarding the sustainability of chemical production is currently being used to help formulate green pharmaceuticals. These same principles may be applied to the development of improved antimicrobials. Development in this area would benefit both people and the environment.