Eco-toxicity and human estrogenic exposure risks from ^·OH-initiated photochemical transformation of four phthalates in water: A computational study

Transformation products (TPs) of emerging organic contaminates (EOCs) in water are still rarely considered in environmental risk assessment, although some have been found to be concern. ^·OH is believed as an important reactive species both in indirect phototransformation and advanced oxidation technology. Thus, eco-toxicity and human estrogenic exposure risks of four phthalates and TPs during the ^·OH-initiated photochemical process were investigated using computational approach. Four phthalates can be degraded through ^·OH-addition and H-transfer pathways. The ^·OH-addition TPs were predominant for dimethyl phthalates, while H-transfer TPs were predominant for other three phthalates. Compared with phthalates, ^·OH-addition TPs (o-OH-phthalates) were one level more toxic to aquatic organisms, and m-OH-phthalates exhibit higher estrogenic activity. Although H-transfer TPs were less harmful than ^·OH-addition TPs, some of them still have aquatic toxicity and estrogenic activity. Therefore, more attentions should be paid to photochemical TPs and original EOCs, particularly those exhibiting high estrogenic activity to humans. - Highlights: • Phthalates can be degraded with ^·OH-addition and H-transfer pathways. • ^·OH-addition products are mainly formed during DMP transformation. • H-transfer products were predominant for the transformation of DEP, DPP and DBP. • o-^·OH-addition products have greater eco-toxicity than corresponding phthalates. • m-^·OH-addition products have higher estrogenic activity than corresponding phthalates. - Computational approach could provide valuable information on the mechanisms, kinetics, eco-toxicity as well as human estrogenic exposure risks of EOCs and their transformation products.