Developmental effects and genotoxicity of 10 water disinfection by-products in zebrafish

Disinfection by-products are contaminants produced during drinking water disinfection. Several DBPs have been implicated in a variety of toxic effects, mainly carcinogenic and genotoxic effects. Moreover, DBPs exposure has also been associated with an increased risk of developmental effects. In this study, the developmental toxicity and genotoxicity of 10 DBPs (four trihalomethanes [THMs], five haloacetic acids [HAAs] and sodium bromate) in the zebrafish embryo model were evaluated. Embryos exposed for 72 hours were observed for different endpoints such as growth, hatching success, malformations and lethality. THMs exposure resulted in adverse developmental effects and a significant reduced tail length. Two HAAs, tribromoacetic acid and dichloroacetic acid, along with sodium bromate were found to cause a significant increase in malformation rate. Chloroform, chlorodibromomethane and sodium bromate produced a weak induction of DNA damage to whole embryos. However, developmental effects occurred at a range of concentrations (20–100 μg/mL) several orders of magnitude above the levels that can be attained in fetal blood in humans exposed to chlorinated water. In conclusion, the teratogenic and genotoxic activity observed by some DBPs in zebrafish reinforce the view that there is a weak capacity of disinfection products to cause developmental effects at environmentally relevant concentrations.

Total and Efficient Removal of Tribromoacetic Acid by Ultraviolet Irradiation

Tribromoacetic acid (TBAA), one of the typically recalcitrant and toxic chlorine disinfection byproducts (DBPs), is widespread in the drinking water and threating human health. The environment-friendly technology, UV irradiation, could efficiently destruct TBAA. The present study investigated the removal efficiency, photodegradation kinetics, and photodegradation mechanism of TBAA under UV irradiation. It revealed that the photodegradaton process of TBAA agreed well with the pseudo-first order kinetics, with the rate constant of 1.084 min-1and half-time of 0.64 minutes. Further study on intermediate products formation and mass balance indicated that complete debromination and detoxification were obtained with almost all the bromine atoms released as bromide ions, and suggest that the cleavage of three C-Br bonds concurrently occurred during the photolysis of one TBAA molecule. It will provide some guidance for efficient treatment of brominated contaminants in water.