Dioxin Photoproducts of Triclosan and Its Chlorinated Derivatives in Sediment Cores

Abstract

Triclosan, a widely used antimicrobial, is known to undergo phototransformation in aqueous solution to form 2,8-dichlorodibenzo-p-dioxin (2,8-DCDD). Two sediment cores from a wastewater-impacted depositional zone of the Mississippi River were analyzed for triclosan by ultra performance liquid chromatography-triple quadrupole mass spectrometry (UPLC-MS-Q(3)) and for a suite of polychlorinated dioxins and furans by high resolution gas chromatography-mass spectrometry (HRGC-MS) to provide evidence of this photoreaction in the environment. 2,8-DCDD was detected at levels that trended with the historical use of triclosan since its introduction in the 1960s. Three other dioxin congeners, 2,3,7-TCDD, 1,2,8-TriCDD, and 1,2,3,8-TCDD, which are known photoproducts of chlorinated derivatives of triclosan, were also detected with similar trend profiles. These four congeners comprised the majority of di- through tetra-chlorinated dioxins. The trend profile of these specific dioxin congeners did not correlate with the trend profile of the higher-chlorinated dioxin homologues or any chlorinated furan homologues, suggesting a unique source. These results are fully consistent with the phototransformation of triclosan and its chlorinated derivatives that form during wastewater chlorine disinfection as the source of 2,8-DCDD, 2,3,7-TriCDD, 1,2,8-TriCDD, and 1,2,3,8-TCDD in this aquatic environment. As the levels of triclosan-derived dioxins increased over time and the total level of chlorinated dioxins decreased, the contribution of triclosan-derived dioxins to the total dioxin pool increased to as high as 31% by mass in recent years, indicating that their contribution to total dioxin toxicity may need consideration.

Triclosan breakdown by Fenton-like oxidation

“…Evidences of estrogenic effects have also been observed by several authors [9,10]. Moreover, the presence of triclosan in water can lead to the formation of chloroform and related trihalomethanes as well as chlorinated dioxins from chlorine disinfection [7,11].…”

Investigation on the montmorillonite adsorption of biocidal compounds incorporating thermodynamical-based multicomponent adsorption isotherm

“…Some researchers denote that sublethal concentration of remaining biocides found in the nature, particularly in the reclaimed water, may accumulate in the microbial cells and elicit microbial resistance on the biocides itself and some antibiotics, which may impact on the human health [4][5][6]. In the other hands, some toxic organic compounds such as the trihalomethanes, dioxins, and benzenes, which are known to be carcinogenic substances have been reported to be exist as the degradation products of those biocides and poisoning many aquatic organisms [7][8][9]. As the result, supplementary treatment process on the regular wastewater treatment plant should be involved to manage a maximum elimination of those hazardous residues.…”

“…Several processes have been proposed to remove those micropollutants such as UV/TiO 2 photocatalysis [7,10], membrane bioreactor [11], chemical oxidation [12], chlorination [9,13], ozonisation [12,14], and activated carbon adsorption [14][15]. Amongst those processes, adsorption shows a promising prospect in removal efficiency and cost feasibility.…”

Use of a novel sediment exposure to determine the effects of triclosan on estuarine benthic communities

“…Concentrations of triclosan are generally higher toward core surfaces, indicating a recent increase in deposition [4,5]. In addition to its persistence in sediments, triclosan has been shown to degrade to a dioxin in sunlight [6][7][8].…”