Photochemical conversion of triclosan to 2,8-dichlorodibenzo-p-dioxin in aqueous solution

The direct photolysis of triclosan (5-chloro-2-(2,4-dichlorophenoxy)phenol), an antimicrobial additive commonly detected in surface waters, is studied. It is found that 2,8-dichlorodibenzo-p-dioxin (2,8-DCDD) is produced in both buffered and natural (Mississippi River) water with yields ranging from 1 to 12% under a variety of conditions. This result indicates that triclosan is likely converted to 2,8-DCDD in sunlight-irradiated surface waters.