Review of Literature
Recently, in India, there is increasing uses of personal care products which were thought to increase our personality in the society. When the usage of cosmetics is increasing, the impacts on environment are also increasing. Most of the peoples are not aware of a product that contains certain chemicals, which could affect their life and also the environment. One such chemical is the Triclosan (TCS), which is responsible for creating a negative impact on environment and human health.
TCS is said to be persistent and bioaccumulative that is responsible for its higher toxicity makes them to come under the group of emerging contaminants. Due to its excellent antimicrobial properties, there has a growing demand for their production and are widely used in personal care products which includes soap, household cleaners, cosmetics, mouthwash, toothpaste etc. It is estimated that about 15,000 tons and 2, 27,000 kg of TCS, respectively, which is produced annually worldwide (Chen et al. 2013). TCS are typically found in concentrations of 0.3% in European country products (Bedoux et al., 2012). The approximate concentration in South African products is about 0.2- 0.3% for TCS (Linington, 2011) and the detection limit was for waste water and sludge samples which was given by Danish ministry of the Environment (2003) ranging from 0.01µg/L and 0.04µg/L.
For the first time, Triclosan was patented by swiss company – Ciba-Geigy in 1964 Rolf (2014). It had registered the TCS as a Pesticide in 1969 and introduced for use in personal care products as antimicrobial agent and preservative by 1970s and it was mainly used as hospital scrub. The application of TCS was expanded commercially from the year 2000 and could be found in 75% and 25% of bar soaps and from 2014, they were used in more than 2000 consumer products up to 0.1- 1.0 % w w¹ (Halden, 2014). At present, Baden Aniline and Soda Factory (BASF), manufactures TCS under name of Igrasan DP300.
2.3. Structure of Triclosan
2.4. Physico-chemical properties of Triclosan (TCS)
Son et al. (2009) reviewed that Triclosan (TCS) or 5-chloro-2-(2, 4-dichlorophenoxy) phenol – named by IUPAC, white powdery, non-polar organic compound with slightly aromatic compound, phenolic odor and slightly soluble in water but easily soluble in fat and hence, easily moves across the cell membranes. Triclosan is a relatively small molecule, with a molecular weight of 289.54 g mol and a diameter of about 7.4 Å (Rossner et al., 2009).
TCS is a white solid at standard temperature and pressure, with a boiling point in the range of 280-290 °C and a melting point in the range of 56-58 °C. Triclosan has a low partition coefficient (log Po/w= 4.7) (Loveren et al., 2000). The partition coefficient is a ratio of solubility between two liquids, typically octanol and water. At higher concentrations, TCS acts as a biocide with varoius cytoplasmic and membrane targets, while at lower concentrations, it acts as a bacteriostat. The property of Triclosan is given in Table 2.1.
Table 2.1. Pysicochemical properties of TriclosanS.NoProperty Value
1. Molecular weight 289.6
2. Water solubility 12 mg/L
3. Dissociation constant (pKa) 8.14 at 20°C
4. Vapor pressure 7 × 10-4Pa at 25°C
5. Partition coefficient (log KOW) 4.8
6. Aerobic biodegradation in soil 17.4 – 35.2 day half-life
7. Aqueous photolysis 41 min. half-life at pH 7 and 25°C
8 Adsorption to suspended solids (KOC) 47,454 mL/g
(Reiss et al., 2002)
2.4.1. Application of Triclosan in different consumer products
Triclosan has been used since 1970s, and is now found in the following products;
Laundry detergents and softeners
Plastics (e.g., toys, cutting boards, kitchen utensils)
Toothpaste and mouth washes
Deodorants and antiperspirants
Cosmetics and shaving creams
Acne treatment products
Apparel like socks and undershirts
Hot tubs, plastic lawn furniture
Implantable medical devices and
Pesticides (APUA, 2011)
2.5. Source of Triclosan(Ginebreda et al., 2010) reported that a large amount of TCS were continually discharged into the environment through human wastes by excretion, washings, manufacturing, etc. and thus it is widely detected in aquatic ecosystems. TCS is more frequently detected compound in environment and hence, it is ubiquitous in nature. Horswell et al. (2014) detected TCS in various environmental and biological samples which includes, wastewater, sludge, surface water, sediments, breast milk, human urine, soil, vegetation and groundwater in the range of ng L?¹ in liquids and ng g?¹ to mg kg?¹ in solids.
Nfodzo and Choi (2011) reported that the major source of Triclosan (TCS) is particularly introduced from municipal wastewater treatment plant (WWTPs) and other sources are, discharging of waste water treatment effluents into surface water and biosolids application to land. After the usage of Triclosan or triclosan added products, it undergoes a reaction with free chlorine present in tap water and the formation of chloroform will be occur. This conversion of chloroform increases the water temperature and other chlorinated products which then lead to carcinogenic.
2.5.6. From industries
Ramaswamy et al. (2011) concluded that the industries are the major contributors of TCS into river systems and explained that the TCS is used extensively in textiles and tanneries to protect from odor by the growth of bacteria, fungi and to eliminate dust mites. TCS is also used in the manufacturing of plastics as an antimicrobial additive to protect products from deterioration, odors and discoloration. In Northern Greece, it was reported by Pothitou and Voutsa (2008) that the concentration of TCS ranged from 87 to 190 ng L-1 in influent and 82 to 25 ng L?¹ in effluent of textile and tannery industries respectively.
2.6. Characteristics of Triclosan2.6.1 In aqueous solution (Sewage/ Surface water)
Raisibe et al. (2017) had reported that TCS concentrations were high in sewage influent about, 2.05-18.6 mg L-1; effluent, 0.991-13.0 mg L-1. Singer et al. (2002), performed that the concentration in wastewater effluents were in the range of 42-213 ng L-1 and the concentrations of 11-98 ng L-1 in the receiving rivers. The removal efficiencies of TCS from the liquid–phase of a WWTP were 95% and 97 %, respectively. The majority of TCS entering the WWTP was removed from the liquid and became adsorbed to the sewage sludge. Sabaliunas et al. (2003) reported that TCS compound found at ppm or ppb levels in wastewater influents, however, over 90% is removed by activated sludge process.
The two important pathways for elimination of Triclosan in surface waters are photolysis and partitioning into particles. Ramaswamy et al. (2011) reported the mean concentration of TCS in Tamiraparani river water in India is about 945 ng L-1, was an order of magnitude greater than the other two water systems. Kaveri and Vellar reported about 3800- 5160 ng L-1 and the highest concentration of TCS detected in surface waters. TCS was detected 95 % in surface water with a concentration range of 430 – 133,000 ?g kg-1 (Bester (2003).
Rajab et al. (2009) reported the concentrations of TCS up to 133 mg kg-1 dry weight, with mean concentrations of 14 ± 18 mg kg-1 in U.S. sludge samples. Raisibe et al. (2017) had reported that TCS concentrations of raw sludge, 3.75-18.0 mg kg-1; treated sludge, 2.18-7.61 mg kg-1 respectively. Wastewater sludge treated in an anaerobic digester for 19 days contained the TCS at concentrations of 33 mg kg-1, respectively (Heidler and Halden, 2007). Due to hydrophibicity, triclosan accumulates in sewage sludge, ranged between 0.7 to 15 mg Kg-1 in Denmark (Mogensen et al., 2007). McClellan and Halden (2010) reported that, TCS level in sewage sludge is higher in the Nordic countries with average concentration of 14 mg Kg-1 in U.S (Table 2.5). Hence, the highest concentration of 150 mg Kg-1 is very extreme, that may results due to where a bottle of soap, shampoo and detergent is emptied directly into the drain (Svenningsen et al., 2011).
Butler et al. (2012) reported that, the antimicrobial substance, TCS can partition into sewage sludge during wastewater treatment and it frequently transferred to soil, when applied to land and treatment process. In WWTPs, the use of activated sludge treatment with combination of anaerobic biosolid digestion, 51 ± 18 of the influent mass of TCS will accumulate and persist in sewage sludge (Chalew and Halden, 2009). McAvoy et al. (2002), who reported that the bulk of TCS in WWTPs was devoid during aerobic sludge digestion and with anaerobic sludge digestion it accounts for a very small portion of TCS removal. TCS was examined in sewage WWTP sludge and reported at the concentration of the antimicrobial, with a median concentration of 5000 ?g kg?1 of dry weight (Reiss et al., 2009).
McClellan and Halden (2010) analysed the biosolids for TCS worldwide and suggested that the concentrations typically range between 0.6 and 58 mg kg-1. Xia et al. (2010) measured in soils for 33 years that had received biosolids annually, which was contaminated by TCS, about 48 and 67% of the extractable triclosan was located at depth (30-120 cm) indicating substantial translocation. Raisibe et al. (2017) reported that TCS concentration in biosolids is about biosolids, 2.16-13.5 mg kg-1. Pyke et al. (2014) were collected biosolid samples at 14 different sewage treatment plant and identified in every samples were ranged from 25 to 42 µg g-1. When biosolids of sewage is applied to land, the toxic metals in sewage or sludge may accumulate through the process of biodegrade or biotransform in the soil and crops and enter into food chain due to continuous land application (Garcia-Santiago et al., 2016). Lozano et al. (2012) reported the method detection limit (MDL) of TCS was 1.0 and 15.9 ng g-1 wet wt for soils and biosolids respectively and their limit of quatification (LOQ) was about 2.0 and 28.0 ng g-1 wet wt.
Table 2.2. Triclosan concentrations (?g g-1 dry weight) in national studies of biosolids produced in municipal wastewater treatment plants.
Country WWTPs examined Mean concentration
(µg g-1) Maximum concentration (µg g-1) References
USA 94 12.6 19.7 McClellan and Halden, 2010
India 5 1.2 – Subedi et al., 2015
Canada 4 4.2 – Chu and Metcalfe, 2007
Canada 6 6.8 11.0 Guerra et al., 2014
S.Korea40 – – Subedi et al., 2014
Ireland 16 0.61 4.9 Healy et al., 2017
Although, primarily TCS is considered to be water-borne contaminant, the antimicrobial that enter into the terrestrial environment during the application of sewage sludge to agricultural and industrial land (Lozano et al., 2010; Fuchsman et al. 2010). Activated sludge concentrations of TCS are typically measured between 570 and 14,500 ?g kg?1 of dry weight, whereas concentrations in biosolids have been documented in the range of 95–32,800 ?g kg?1 (Chalew and Halden, 2009; Lozano et al., 2010). Due to lipophilic nature of TCS, the antimicrobial properties were partitioned into sediment and soil, but the transport potential from biosolids into surface runoff has been characterized as low (Al-Rajab et al., 2009).
The potential for loss via surface runoff, leaching depends on their availability in soil and their persistency in soil. It has been speculated that the persistence of TCS in the soil may be enhanced by the organic content of the soil (Fu et al., 2016). Wu et al. (2009) reported the temperature of soil (which is positively correlated to half life), the physicochemical properties of compounds, and the presence of co-contaminants, making TCS potentially more available in the soil and their surface (Walters et al., 2010). Wu et al. (2009) concluded that antibacterial agents absorbed strongly by the sandy loam and silty clay soils with and without addition of biosolids which ranged from 178- 264 Kg-1. The sorption of TCS decreased with increase in soil pH from 4 to 8. Eventhough, TCS may not be physically mobile between soil compartments but other properties that present in soil helps in transferring of TCS from soil to biota. Dann and Hontela (2008) assessed the potential for organic biosolid or manure derived soil contaminants in amended agriculture land to accumulate in biota. Hence, the wider spread of triclosan into soils through biosolids. The triclosan partitions into soil or sediment in the environment and does not degrade fast, but degrade with a half-life of week in aerobic and to month in anaerobic conditions by the process of biodegradation.
2.7. Chemistry of Triclosan degradation process
The presence of triclosan in natural water is of concern due to its potential endocrine-disrupting properties (Pothitou and Voutsa, 2008), and because it is photochemically transformed to 2, 8- dichlorodibenzo-p-dioxin (2, 8-DCDD) under natural sunlight (Aranami and Readman, 2007). Triclosan that remains in the secondary (pre-disinfection) effluent after activated sludge treatment may be chemically transformed during the final disinfection stage, generating disinfection byproducts in the final (post-disinfection) effluent. Sodium hypochlorite, which is commonly used as a source of free chlorine and as a disinfectant oxidant in sewage treatment plant of US, known to chlorinate triclosan at the ortho- and/or para-positions of its phenol ring to form chlorinated triclosan derivative (CTD) products like, 4,5-dichloro- 2-(2,4 dichlorophenoxy) phenol (4-Cl-TCS), 5,6-dichloro-2-(2,4- dichlorophenoxy) phenol (6-Cl-TCS), and 4,5,6-trichloro-2-(2,4- dichlorophenoxy) phenol (4,6-Cl-TCS) (Rule et al. 2005).
Buth et al. (2009) had explained the derivatives of 4-Cl-TCS, 6-Cl TCS, and 4,6-Cl-TCS (Fig.5.1) which undergoes photolysis process in natural waters to form the respective dioxins, such as, 2,3,7-trichlorodibenzo-p-dioxin (2,3,7-TriCDD), 1,2,8-trichlorodibenzo-p-dioxin (1,2,8-TriCDD), and 1,2,3,8-tetrachlorodibenzo-p-dioxin (1,2,3,8-TCDD). Ferrer et al. (2004) found the replacement of a chlorine atom by a hydroxyl group has been done by the degradation pathway. The chlorine atom substitution by hydrogen and the cleavage of the C–O bond have also been observed. Latch et al. (2003) investigated the reaction of pH, irradiation wavelength and its role on TCS were observed and triclosan ring closure to 2,8-DCDD in aqueous solutions buffered at pH 8 and above, suggesting that the phenolate form of triclosan (p Ka=8.1) is photoreactive, whereas triclosan and methyl ether are photostable. Tixier et al. (2002) also reported that direct phototransformation of the anionic form is the dominant photochemical degradation pathway of triclosan.
Lores et al. (2005) reported the photochemical conversion of triclosan in continental waters, into dichlorodibenzo-p-dioxin (DCDD) has been confirmed in the preliminary experiments employing photo-SPME (solid-phase micro-extraction) using 18-W UV irradiation at 254-nm wavelength. Under these conditions, triclosan is rapidly photodegraded (70% of triclosan was degraded in 2 min) to DCDD directly on the polydimethylsiloxane coating of the SPME fiber. Glaser, (2003) explained that triclosan has a very low partition coefficient (log KOW) of 4.76, hence, it is lipophilic in nature and said to be higher potential of bioaccumulation.
Fig.2.2. Degradation process of Triclosan2.7.1. Chlorinated Triclosan derivatives (CTDs) in natural water
The toxicity of the chlorinated triclosan derivatives (i.e., dioxin photoproducts) has been estimated to be 10 to 20 times higher the toxicity of 2, 8-DCDD (Ontario Ministry of the Environment, 1984). Triclosan and CTDs were detected in every untreated samples in US, sewage treatment plant at levels ranging from 455 to 4540 and 5 to 98 ng L-1, respectively, though both were efficiently removed from the liquid phase during activated sludge treatment. Triclosan concentrations in the pre-disinfection effluent ranged from 38 to 217 ng L-1, while CTD concentrations were below the limit of quantification (1 ng L-1) for most samples.
The use of chlorine disinfection in treatment plant were decreased the concentration of , triclosan, while CTDs were formed during chlorination, as evidenced by CTD levels as high as 22-30 ng L-1 in the final effluent. No CTDs were detected in the final effluent of the treatment plant that used UV disinfection. The total CTD concentration in final effluent of the chlorinating treatment plant reached nearly one third of the triclosan concentration, demonstrating that the chlorine disinfection step played a substantial role in the fate of triclosan in this system (Buth et al., 2011). Latch et al. (2003) has observed the triclosan in an aqueous solutions by exposing it to irradiation, after exposing, triclosan disappeared from the first 5th minute and appearance of dioxin were occurred. Hence, he hypothesized that triclosan and the wastewater produced those CTDs which is important for the production of dioxin.
2.8. Degradation products of Triclosan2.8.1. MethyltriclosanDuring the wastewater treatment process, Triclosan is transformed by biologically from methylation into methyltriclosan MTCS; 5-chloro-2-(2, 4 dichloropheoxy) anisole (Boehmer et al., 2004; Bester, 2005), which is more lipophilic in nature, which is then released into receiving environment. Nuria et al. (2013) identified the presence of Methyltriclosan in fish which has been used as a marker of exposure to WWTP effluent. Hence, the lipophilicity of Methyltriclosan and its resistance to biodegradation and photolysis processes makes the mobilite to exhibit a higher degree of environmental persistence than its parent compound (Lindstrom et al., 2002). A large fraction of TCS loss is transformed to Methyl-TCS. Majority of TCS recovered as Methyl-TCS about 16.5 and 50.6 % respectively. For Methyl-TCS, the MDL was found to be 0.25 and 1.4 ng g-1 wet wt and for biosolids was about 0.48 and 26.6 ng g-1 respectively. Also, the half-life of TCS was determined as 104 days and the Methyl-TCS was more persistent than TCS and was estimated to be as 443 days. Balmer et al. (2004) have explained about the formation of Methyl-TCS through biological methylation in different WWTP process obviously limits the total TCS removal because the transformation products of TCS is much more resistant to photolysis. Lindstrom et al. (2002) said in aqueous region, TCS is readily degraded in the environment with relative increase of Methyl-TCS increases in summer, and nearly equal to the residual TCS concentration in the upper region of surface water. He also explained the slow reversion to the parent compound in fish liver and intestine, Methyl-TCS will bioaccumulate upon chronic exposure and posing a potential threat to humans as a result of fish consumption (James et al. 2012).
Methyl-TCS is typically found in much lower concentrations than those of TCS with ratios (Methyl-TCS/TCS) between 0.01 and 0.05 for effluent, surface water, sludge, and sediment (Bester, 2005). McAvoy et al. (2002) have documented that the Methyl-TCS/TCS ratio can largely exceed in effluent, surface water, sludge, and sediment. Benny et al. (2014) showed that the Methyl-TCS fraction can become substantially higher in environment where TCS is readily degraded relative to Methyl-TCS (such as at the air?liquid interface of lakes) as well as in high microbial activity (such as aerobic composters). This transformation of TCS into Methyl-TCS will ultimately increase the environmental persistency of triclosan, because the methylation increases the bioaccumulation potential and limits the biodegradation of total TCS congeners (i.e., the sum of Methyl-TCS and TCS).
There has been increasing concern regarding the degradation and the transformation of TCS during manufacturing, incineration and in the aquatic environment which leads to dioxin toxicity. The photolysis is the major pathway of the antimicrobial in the aquatic environment, which documented the formation of 2,8-dichlorodibenzodioxin (DCDD) and other dioxin derivatives during the photo degradation of TCS in aqueous solutions (Aranami and Readman, 2007). The pH of aqueous solutions spiked with TCS influences the formation of dioxin by-products and Latch et al. (2003) reported that 1–12% of TCS is converted to DCDD in aqueous solutions buffered at a pH 8 or above and concluded that, in sunlight-irradiated waters, the conversion of TCS into dioxin by-products is dependent on both the pH and irradiation wavelength.
Mezcua et al. (2004) investigated the photo degradation of TCS to dioxins in wastewater samples and the study indicated that 2, 7/2, 8-dibenzodichloro-p-dioxin is a by-product of the TCS, with 8 ?g ml-1 of antimicrobial were spiked in both water and wastewater samples. These results were consistent with phototransformation of triclosan and the degree of photolytic conversion was dependent upon pH and the organic matter content in the sample. Sanchez-Prado et al. (2006) were the first to use a solar simulator photoreactor, in combination with actual contaminated wastewater samples, identified the formation of 2, 8-DCDD and a possible DCDD isomer or dichlorohydroxydibenzofuran independently in the sample. The photochemical reaction of triclosan accounts 80% loss of epilimnion region of Lake Greifensee during summer season.
Aranami and Readman (2007) irradiated the freshwater and seawater samples with a low-intensity using artificial white light source for a 12 day period. The photodegradation of TCS produced DCDD, in the 3rd day of irradiation that occured in both freshwater and seawater samples, after 3 days of irradiation. The photochemical conversion of TCS in natural water samples of Mississippi River and Lake Josephine waters was investigated by Buth et al. (2009). This conversion of chlorinated triclosan derivatives into dioxins was substantiated in natural and buffered pure water, with yields of 0.5–2.5%, respectively. The majority of TCS is photolytically transformation products, along with the environmental factors influencing their degradation (Aranami and Readman, 2007) and quantifying the level of risk to both aquatic environments and humans is determining to what extent and under which environmental conditions the conversion of TCS into toxic by-products occurs.
2.8.3. ChlorophenolsThe photochemical transformation of TCS also produce 2, 4-dichlorophenol and 2, 4, 6-trichlorophenol, which the US EPA has pointed as priority pollutants. The formation of chlorophenols from TCS was demonstrated by Kanetoshi et al. (1987) however; the higher concentrations of chlorine and TCS are relevant to environment. Later (Greyshock and Vikesland, 2006) validated that chlorophenols are transformation products of TCS, in the low levels of chlorine or chloramines. TCS reacted with free chlorine under drinking water conditions and 2,4-dichlorophenol was formed through the ether cleavage of TCS, which then undergoes electrophilic substitution to form 2,4,6-trichlorophenol.
The effect of pH on the formation of TCS byproducts were demonstrated by Rule et al. (2005) that it was primarily ionized the phenolate form of TCS that reacts with hypochloric acid. Canosa et al. (2005) tested at low concentrations of TCS (ng mL?1) and chlorine (mg L?1) with this test, 2, 4-dichlorophenol and 2, 4, 6-trichlorophenol were detected in all of the samples. Even though, the molar yields of TCS conversion were less than 10% and it has demonstrated that these two phenolic by-products are relatively stable over time and potentially toxic Fiss et al. (2007).
The presence of TCS in various consumer products will react with free chlorine or chloramine to produce chloroform and other chlorinated triclosan products with different pH by Greyshock and Vikesland (2006). Fiss et al. (2007) also assessed the propensity of a dish soap containing TCS to form chloroform when added to chlorinated water and assessed after 5 min and 120 min, the concentration of chloroform was produced from 15 to 50 ?g l?1. and the significant amounts of chloroform may be formed during the daily use of household products containing the antimicrobial properties. The conversion of TCS to chlorinated derivatives is also dependent on temperature, chloroform yields higher in increased temperatures. An exposure model completed by Fiss et al. (2007) indicated that, under certain conditions, the amount of chloroform produced could be significant, which may place consumers at an increased risk for adverse health effects.
2.9. Effects of Triclosan on aquatic organisms
Triclosan is a ubiquitous because of continuous discharge of chemicals into waste water streams. Hence, the incomplete removal of Triclosan results in contamination of water, soil and other organisms. Orvos et al. (2002) reported on most drugs that targets humans, in which exhibits higher toxicity to many lower trophic organisms, such as microalgae. Wilson et al. (2003) reported the significant changes in phytoplankton community that exposed to TCS concentration as low as 15 ng L-1 and approximately 33% reduction in algal genus richness at 150 ng L-1.
Hence, the peak levels of 3800 and 5160 ng L-1 at two sites of Tamiraparani River indicate the high risk on algal communities. Buser et al. (2006) reported the higher concentrations of Methyl-TCS were found in fish as high as 2100 ng g-1 (Veldhoen et al. 2006). Veldhoen et al. (2006) reported the effects of TCS on thyroxin-induced metamorphosis in frog tadpoles and some algae at a concentration ranges from 100 – 150 ng L-1.
2.9.1. Algae and invertebrates
Algae were determined to be the most susceptible organisms. It is primary food source for many aquatic species, constitute a specific pathway for the accumulation of lipophilic water-borne contaminants, such as TCS (Capdevielle et al., 2008). Due to continual exposure of TCS, leads to incomplete removal during the wastewater treatment process in receiving waters, and increasing their accumulation of the antimicrobial properties and its degradation products in the tissues of aquatic organisms. From these measurements, bioaccumulation factors of 1100 and 1600 ?g kg?1 were estimated for parent compound and its methylated by-product. Coogan et al. (2007) sampled the filamentous algae (Cladophora spp.) in a receiving stream from the city of Denton (Texas) for measuring of TCS and MTCS and were ranged between 100–150 and 50–89 ?g kg?1, respectively. Also, the bioaccumulation potential of TCS and MTCS was also determined in freshwater snails (Helisoma trivolvis) and in algae (Cladophora spp.), using GC-MS (Coogan and La Point, 2008). Bioaccumulation concentrations of TCS and MTCS for snail tissue were 500 and 1200 ?g kg?1, respectively. The algal bioaccumulation of TCS were also high, 1400 and 1200 ?g kg?1, respectively. Tatarazako et al. (2004) showed the result the microalgae (0.15 mg L-1) are very sensitive to triclosan than bacteria and fish. In a study by DeLorenzo et al. (2008), adult grass shrimp (Palaemonetes pugio) were exposed to 100 ?g l?1 of TCS and they were found to accumulate as MTCS after a 14-day exposure period. This finding provides evidence for both the conversion of TCS to MTCS in seawater, and their bioaccumulation potential. Though MTCS is resistant to the processes of biodegradation and has the ability to persist in the environment for longer periods of time than the parent compound. Many aquatic invertebrates depend on algae as a source of nutrients, by which it leads increase of TCS concentration in many aquatic organisms.
Miyazaki et al. (1984) was the first to report the presence of MTCS in aquatic biota. In fish, TCS and its byproducts have been detected in higher level of concentration. From Tama River and Tokyo Bay, fish and shellfish were collected, then TCS and MTCS was identified by GC-MS in all the fish samples (1–38 ?g kg?1 whole body) and shellfish samples (3–20 ?g kg?1). A study by Adolfsson-Erici et al. (2002) who measured TCS levels in rainbow trout (Oncorhynchus mykiss) in the waters of a WWTP in Sweden. Bile fluid of fish contained TCS at concentrations ranging from <0.01–0.10 mg kg?1 in controls and 0.44–120 mg kg?1 in fish exposed to sewage water. Houtman et al. (2004) also used GC-MS to identify a magnitude of xenobiotic compounds, including TCS, in the bile of male bream (Abramis brama) living in Dutch surface waters. TCS was detected in samples of bile, at relatively high concentrations of 14 and 80 ?g ml?1. The results indicate that accumulation of TCS takes place in the process of biomagnifications.
Concentrations of MTCS in fish were reported between 150 and 2500 ng g?1 of lipid weight. Balmer et al. (2004) detected MTCS in fish in the range 4–370 ng g?1 and lower level of concentration were compared with previously measured in fish samples from different rivers. This difference is to be expected as concentrations of MTCS should typically be higher in river systems that receive inputs from WWTPs. A large monitoring study on TCS and MTCS was conducted by Boehmer et al. (2004) using fish tissues. Samples of tissues from breams (Abramis brama) from the period 1994–2003 were analyzed for TCS and MTCS. While TCS was only detected in a less number of samples, MTCS was present in all samples that were analyzed.
The increasing MTCS concentrations was observed in bream tissue from the mid 1990s until 2000, with levels of MTCS increasing from 10 to 26 ng g?1 of wet weight and ranged from below the limit of quantification up to 3.5 ng g?1. MTCS is a persistent pollutant with the potential to accumulate in the tissues of fish. Valters et al. (2005) detected TCS in the plasma samples of 13 fish species from the Detroit River, in the range of 750 to >10,000 pg g?1 of wet weight. Leiker et al. (2009) identified the MTCS in male carp (Cyprinus carpio) from the Las Vegas Bay and in the Las Vegas Wash, Nevada; MTCS was detected in all carp samples, with a mean concentration of 520–596 ?g kg?1 per wet weight basis. The concentrations of MTCS detected much higher, indicating that this might be due to the sediment foraging behavior of carp, which exposes them to higher levels of water-borne chemicals due to lipophilic nature. TCS and its metabolites have been detected in sediments, both freshwater and marine (Miller et al., 2008; Chalew and Halden, 2009). Lozano et al. (2010) in USA surveyed the presence of personal care products, in fish sampled from five effluent dominated rivers receiving discharge from WWTPs in large urban centers and rivers.
2.9.3 Marine mammals
Fair et al. (2009) characterized the presence of TCS in the plasma of bottlenose dolphins (Tursiops truncates), a top level predator, and then correlated biological levels with environmental concentrations and the bioaccumulation of TCS in a marine mammal with concentration of 5.5 to 20 ng l?1. TCS measured in estuarine water samples ranged from 4.9 to 13.7 ng l?1, averaging 7.5 ng l?1 and their plasma concentrations were 0.12–0.27 and 0.025–0.11 ng g?1 wet weight, at the two estuaries, respectively. Apparently, TCS has also been detected at a concentration of 9.0 ng g?1 of wet weight in the plasma of a captive killer whale (Orcinus orca) (Bennett et al., 2009) (Table 2.3). These studies further needed to monitor TCS and assess its effects in wild species.
Table.2.3. Concentration of Triclosan (TCS) in aquatic organisms
Organisms Type of Sample TCS (µg kg-1) References
Algae and invertebrates
(Cladophora spp.) Whole organism 100–150 Coogan et al., 2007
(Helisoma trivolvis) Muscle 50–300 Coogan and La Point,
Vertebrates Rainbow trout
(Oncorhynchus mykiss) Bile 710- 17000 Adolfsson-Erici et al., 2002
(Abramis brama) Bile 14 000–80 000 Houtman et al., 2004
Pelagic fish Plasma 0.75–10 Valters et al., 2005
Atlantic bottlenose dolphins
(Tursiops truncates) Plasma 0.12–0.27 Fair et al., 2009
(Orcinus orca) Plasma 9.0 Bennett et al., 2009
Table.2.4. Acute toxicity of Triclosan on aquatic organisms
Compound Category Species Trophic group Duration LC 50 (mg L-1) References
TriclosanAntimicrobial Daphnia magna Invertebrate 48h 0.39 Balmer et al., 2004
Ceriodaphnia dubiaInvertebrate 24, 48h 0.2, 125 Balmer et al., 2004
Pimephales promelasFish 24,48, 72, 96h 0.36, 0.27, 0.27, 0.26 Balmer et al., 2004
Lepomis macrochirusFish 24, 48, 96 h 0.44, 0.41, 0.37 Balmer et al., 2004
Oryzias latipesFish 96 h 0.602 (larvae), 0.399
(embryos) Batscher, 2006a
Xenopus laevisAmphibian 96 h 0.259 Batscher, 2006b
Acris blanchardiiAmphibian 96 h 0.367 Batscher, 2006b
Bufo woodhousiiAmphibian 96 h 0.152 Batscher, 2006b
Rana sphenocephalaAmphibian 96 h 0.562 Batscher, 2006b
Pseudokirch-neriella subcapitataAlgae 72h growth 0.53
(l g L-1) Bazin et al., 2010
2.9.4. On microbial community
Svenningsen et al. (2011) observed that effects of triclosan on microbial communities and observed that their degradation in simulated sewage-drain-field soil were decreased the microbial population about 22-fold in the presence of 4 mg kg-1 of triclosan. McLeod et al. (2001) reported that the broad range of TCS encompasses many types of Gram-positive and Gram-negative non-sporulating bacteria, some fungi, Plasmodium falciparum and Toxoplasma gondii. It is bacteriostatic (it stops the growth of microorganisms) at low concentrations, but at higher concentrations they are bactericidal (it kills microorganisms).
Doori et al. (2003) reported that the most sensitive organisms to triclosan are staphylococci, streptococci, mycobacteria, Escherichia coli and Proteus spp. In that sp, TCS is effective at concentrations that range from 0.01 mg L-1 to 0.1 mg L-1. Methicillin-resistant Staphylococcus aureus (MRSA) strains are also sensitive to triclosan in the range of 0.1–2 mg L-1. Russell (2003) reported that showering or bathing with 2% triclosan has been shown to be effective in decolonization of patients whose skin is carrying MRSA and also reported that Enterococci are much less susceptible than staphylococci and Pseudomonas aeruginosa is highly resistant.
Heath et al. (1999) had identified that triclosan blocks the active site of enoyl acyl carrier protein reductase enzyme which is essential for fatty acid synthesis in bacteria and it affects the cell membrane and reproduction by preventing bacteria from fatty acid synthesis. When leads to lower concentration, it acts as a bacteriostatic and works against to type II fatty acid synthase enoyl reductase (champlin et al., 2005). While at higher concentrations, it targets the cell membrane.
2.9.5. Triclosan toxicity in Animals
Miller et al. (1983) concerned TCS interfering with the body’s thyroid hormone metabolism led to hypothermic effect, lowering the body temperature, and overall causing a non-specific depressant effect on the central nervous system of mice. The exposure to low levels (0.03 mg L-1) of triclosan with disrupted thyroid hormone associated gene expression in tadpoles, which cause them to prematurely change into frogs (Veldhoen et al., 2006).
Kumar et al. (2009) reported that triclosan exposure leads to decreased sperm production in male rats and also it blocks the metabolism of thyroid hormone, because it chemically mimics thyroid hormone, and binds to the hormone receptor sites, blocking them, so that endogenous hormones cannot be used. James et al. (2010) showed that triclosan can hinder estrogen sulfotransferase in sheep placenta, an enzyme which helps metabolize the hormone and transport it to the developing fetus. The presence of TCS would be dangerous in pregnancy, if it gets through to the placenta to affect the enzyme.
The TCS enhances the production of chloroform in amounts up to 40% higher than levels in chlorine-treated tap water (Fiss et al., 2007). But Hao et al. (2007) reported that no formation of detectable chloroform levels over a range of expected tooth-brushing durations among subjects using toothpaste with triclosan and normal chlorinated tap water. U.S. EPA classifies chloroform as a probable human carcinogen. As a result, triclosan was the target of a UK cancer alert, even though the amount of chloroform generated was less than normally present in treated, chlorinated water and required brushing your teeth or washing your hands for times on the order of two hours or more.
2.10. Techniques to remove TriclosanThe phototransformation of the widely used biocide triclosan (5-chloro-2-(2, 4-dichlorophenoxy) phenol) was quantified (Tixier et al., 2002) for surface waters using artificial UV light and sunlight irradiation. Here, the pH of surface waters, commonly ranging from 7 to 9, determines the speciation of triclosan (pKa 8.1) and therefore its absorption of sunlight. Direct phototransformation of the anionic form with a quantum yield of 0.31 (laboratory conditions at 313 nm) was identified as the dominant photochemical degradation pathway of triclosan in swiss lake (Lake Greifensee). Hence, the direct phototransformation accounted for 80% of the observed total elimination of triclosan from the lake. Based on absorption spectra and quantum yield data, the phototransformation half-lives of triclosan were calculated under various environmental conditions typical for surface waters. Daily averaged half-lives were found to vary from about 2 to 2000 days, depending on latitude and time of year. The removal of TCS in municipal biosolid processing systems was determined (Ogunyoku and Young, 2014) from the measured concentration change after correcting for reductions in soild mass during sludge treatment. Removal of TCS in the digester systems ranged from 20 – 75% respectively. Increased solid retention times during sludge treatment operations were correlated with higher removals of TCS.
Singer et al. (2002) has identified an effective mechanism to remove triclosan from waste water by biodegradation and the biodegradability of triclosan is high under aerobic conditions rather than anaerobic conditions (McAvoy et al., 2002). Wu et al. (2012) found that the removal of triclosan is higher when treated with ozone during municipal sewage treatment and the adsorbing onto zeolites is the most vialble method to remove triclosan. Triclosan also removed through the process of phototransformation on surface water (Tixier et al., 2002).