Impact of Humic Acid on the Photo-Induced Toxicity of Triclosan

Triclosan is an antimicrobial agent which is frequently found in the aquatic environment. Photolysis is an important transformation pathway for triclosan in surface water. Though a lot of studies have been conducted on the toxicity of triclosan, few of them focused on the ecological risk of the mixture after sunlight irradiation. The aim of the present study was to investigate the potential toxicity of triclosan under light irradiation and the influence of the coexisting humic acid by bioassay. Photo-induced acute toxicity and genetic toxicity were observed in the triclosan solutions after 24 h of light irradiation. The addition of humic acid at the concentration of 1 and 5 mg/L both resulted in a significant decrease (p < 0.05) in the photo-induced toxicity of triclosan. It is suggested that the photo-transformation process and the influence of humic acid should be considered for the ecological risk assessment of triclosan in surface water since humic acid is ubiquitous in natural water.