An inescapable fact: Toxicity increase during photo-driven degradation of emerging contaminants in water environments

Abstract

The occurrence of an enormous group of emerging contaminants (ECs) is of continuous concern for the safety and health of human beings, as well as the ecosystem. Photo-driven technologies especially photochemical and photocatalysis are considered to be promising for effective removal of various ECs from water. Although great advances in photo-driven performance have been achieved recently, the toxicity problem remains an important challenge yet. In this short review, we provided a general overview of the latest researches on the toxicity evolution during photo-driven degradation (including direct and indirect photochemistry, as well as photocatalysis) of ECs. Particularly, the increased toxicity was emphasized, and possible reasons were also analyzed in various photo-driven degradation of organic ECs from the viewpoint of essential characteristics and mechanisms. In light of these mechanisms, we discussed perspectives being performed by toxicologists and environmental chemists to completely eliminate toxicity in the application of photo-driven treatment technologies for ECs and their products in future research. • Toxicity elimination should be a goal for the photo-driven degradation of ECs. • Toxicity evolution is related to the concentration and kinds of the formed RSs. • Identification of toxic products and formation mechanisms are significant. • Several unidentified products could cause serious damage to human health. • Photocatalysis can effectively degrade ECs and their products with enough time.