Humic acids decrease the photodegradation of the sunscreen UV filter 2-phenylbenzimidazole-5-sulfonic acid in natural waters

The sunscreen UV filter 2-phenylbenzimidazole-5-sulfonic acid (PBSA) is an emerging pollutant recently detected in surface waters. PBSA is photolabile in pure water and sunscreen cream. PBSA photoinduces DNA damages. However, the photochemical behavior and environmental persistence of PBSA are not well known. Here, we studied the photochemical transformation of PBSA in sea and continental waters. Results show that photodegradation is dependent on water constituents. Whereas low concentrations of humic acids accelerate PBSA photodegradation slightly, high concentrations of humic acids inhibit the photodegradation. Colloidal organic matters of high molecular weights are the main water constituents inhibiting photodegradation. The estimated solar photolytic half-life of PBSA at environmental concentration levels ranged from 3 days from June to August to 35 days in December. Findings show that PBSA is not persistent in waters that are low in colloidal organic matters.