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 Triclosan
S.No Property 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;
? Dish-washing 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
? Hair conditioners
? Trash bags
? Apparel like socks and undershirts
? Hot tubs, plastic lawn furniture
? Impregnated sponges
? Surgical scrubs
? 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 Triclosan
2.6.1 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