Triclosan ? Unintended consequences from antimicrobial agent, Triclosan Jihee Park

 Dangerous Situation?

 Contents [1]K. L. Rule, V. R. Ebbett, and P. J. Vikesland, Environ. Sci. Technol. 2005, 39, [2]D. E. Latch, J. L. Packer, W. A. Arnold, K. McNeill, J. Photochem. Photobiol., A: Chem. 2003, 158, [3]A. R. Fernandez-Alba et al., Anal. Chim. Acta. 2004, 524, [4] “When chlorine + antimicrobial = unintended consequences,” Environ. Sci. Technol. Science News, April 6, 2005 [5] “Common household chemicals affect algae,” Environ. Sci. Technol. 2005, 162A- 164A  References 1.Properties and uses of triclosan 2.Experiments for the formation of THM and dioxin from triclosan 3.Conclusion & suggestion

 Fundamentals of Triclosan  Use of triclosan - Used in toothpastes, acne creams, deodorants, lotions, and hand soaps (concentration : 0.1-1%) - Incorporated into kitchen tiles, children’s toys, toothbrush handles, hot tubs, and athletic clothing  Structure of Triclosan (5-chloro-2-(2,4 dichlorophenoxy)phenol)  Properties of triclosan : antibaterial, antifungal, and antiviral  Concentration of triclosan in wastewater treatment plant (WWTP) Influent : – 21.9  g/L, Effluent : – 22.1  g/L [1] According to the survey of 139 U.S streams by the United States Geological Survey, triclosan was detected in 57.6% of the streams. Concentration : 2.3  g/L far from WWTP,  g/kg near the WWTP [1]  Concentration of triclosan in the streams

Until recently, triclosan was believed to solely act as a nonspecific biocide that disrupts bacterial membrane functionality. Since 1998, however, several studies have indicated that triclosan can act as a site-specific biocide. The site-specific activity of triclosan suggests that organisms may develop resistance, which would render the compound ineffective as a biocide.[1]  Resistance Concern Triclosan can cause significant changes in the composition of the algal genera. As species compete for light and nutrients, the addition of toxic pollutants can lead to the extinction of sensitive species while concomitantly increasing the biomass of resistant species.[5]

 Chlorination of Triclosan Figure 1. Observed pseudo-first-order rate constants (k obs ) vs pH for the electrophilic substation of triclosan by free chlorine. Reaction conditions: [free chlorine] 0 =  M; [triclosan] 0 = 27.5  M; [NaHCO 3 ] = 2 mM. [1] [FC] T =[HOCl] + [OCl - ] [triclosan] T = [triclosan] + [phenolate-triclosan] k obs = k ArO- [phenolate-triclosan].

 Chlorinated Triclosan Intermediates A: 5,6-dichloro-2-(2,4-ichlorophenoxy)phenol B: 4,5-dichloro-2-(2,4-dichlorophenoxy)phenol C: 4,5,6-trichloro-2-(2,4-dichlorophenoxy)phenol D: 2,4-dichlorophenol E: 2,4,6-trichlorophenol Figure 2. Formation and decay of chlorinated triclosan intermediates for pH 4, 7, and 10. Reaction conditions: [triclosan] 0 = 5.05  M; [free chlorine] 0 = 14.2  M; [NaHCO 3 ] = 2 mM. Note that the y-axes vary considerably.[1]

 Chloroform Formation Figure 3. Chloroform formation as a function of solution pH. Reaction conditions: [triclosan] 0 = 2.5  M; [free chlorine] 0 = 25  M; [NaHCO 3 ] = 2 mM. [1]

Figure 4. Formation of trihalomethanes when dish soap brand X reacts with chlorinated water. Reactions conditions: [free chlorine] 0 = 84.9 M; [dish soap] = 0.25 g/L; pH = 7; triclosan concentration in antibacterial soap was measured at 1.4 mg/g. At 24 h, the molar concentration of CHCl 3 is 581 nM and the CHCl 2 Br molar concentra tion is 44 nM for the triclosan dishsoap samples. [1]  Trihalomethane Formation

THM Peter Vikesland of the Virginia Polytechnic Institute and State University. has conducted follow-up research under conditions that more closely mimic those found during home dishwashing. The new experiments used EPA’s maximum allowable residual disinfectant concentration of 4 milligrams per liter in tap water and were conducted at 40 °C, which fits well with the cleaning recommendations of the Soap and Detergent Association. (The association’s website says that dishwater temperatures of less than 33 °C, even with sufficient detergent, are likely to leave a greasy film, while the hottest water most people’s hands can tolerate is about 43 °C.) Under these conditions, triclosan reacts with free chlorine to generate more than 50 parts per billion (ppb) of chloroform in the dishwater. When combined with the other trihalomethanes in the water, the additional chloroform could easily ratchet up the concentration of total trihalomethanes to 80 ppb, which is EPA’s maximum allowable amount, or higher, Vikesland says. [4] Science News of ES&T on April 6 of 2005  Dangerous Dishwashing

 Triclosan Conversion to Dioxin Figure 5. Ring closure to 2,8- DCDD was observed in aqueous solutions buffered at pH8 or above [2] Figure 6. Gas chromatogram corresponding to the analysis of a reagent water sample fortified with triclosan after 36 h of solar irradiation. Two different pH values (5 and 7) are compared and overlapped. [3]

 Dioxin Formation from Triclosan Table 1. Reaction conditions, quantum yields, and conversion yields for triclosan decay (  T ) and 2,8-dichlorodibenzo-p-dioxin (2,8-DCDD) formation (  D ) [2] Figure 7. Photochemical conversion of triclosan to 2,8-DCDD in Mississippi River water. [2]

dioxin  Dangerous Swimming under the Sun dioxin

 Conclusions  Suggestions  Photodegradation of triclosan with and without free chlorine by using TiO 2 photocatalyst  Development of consumer goods, such as sun block lotion, containing both TiO 2 and triclosan. 1.Triclosan can combine with chlorine in tap water to form chloroform gas. 2.Triclosan can produce dioxin as a byproduct of photodegradation. 3.The reaction of triclosan with chlorine could be producing highly chlorinated dioxins in the presence of sunlight.