Occurrence and fate of parabens and their metabolites in five sewage treatment plants in India

Parabens (p-hydroxy benzoic acid esters) are antimicrobial agents, used widely as preservatives in personal care products (PCPs), pharmaceuticals, foods, and beverages. PCPs that contain parabens are a major source of these chemicals in sewage treatment plants (STPs). Very few studies have demonstrated the occurrence of parabens in wastewater. In this study, the occurrence and fate of six parabens, methyl-(MeP), ethyl-(EtP), propyl-(PrP), butyl-(BuP), hepty-(HpP) and benzyl-(BzP) parabens, and five of their metabolites (4-HB, 3,4-DHB, OH-MeP, OH-EtP and BA) were studied in five STPs in India. The concentrations of parent parabens (∑₆parent parabens) in five STPs ranged between 131 and 920 ng/L in influent; 16 and 67 ng/L in effluent; and 104 and 1090 ng/g, dry weight, in sludge samples. The sum concentrations of five paraben metabolites (∑₅paraben metabolites) in five STPs ranged between 4110 and 34,600 ng/L in influent; 2560 and 3800 ng/L in effluent; and 1220 and 35,900 ng/g, dry weight, in sludge samples. These values were higher than those reported for many industrialized countries. We calculated the mass loadings, removal efficiencies, and environmental emissions of parabens based on the measured concentrations in influents, effluents, and sludge. The mean removal efficiencies of parent parabens and their metabolites ranged from 80% to 100% and 28% to 76%, respectively.