Study of the toxicity of 1-Bromo-3-chloro-5,5-dimethylhydantoin to zebrafish.

Objective: 1-Bromo-3-chloro-5,5-dimethylhydantoin (BCDMH) is a solid oxidizing biocide for water disinfection. The objective of this study was to investigate the toxic effect of BCDMH on zebrafish.

Methods: The developmental toxicity of BCDMH on zebrafish embryos and the dose-effect relationship was determined. The effect of BCDMH exposure on histopathology and tissue antioxidant activity of adult zebrafish were observed over time.

Results: Exposure to 4 mg/L BCDMH post-fertilization was sufficient to induce a number of developmental malformations, such as edema, axial malformations, and reductions in heart rate and hatching rate. The no observable effects concentration of BCDMH on zebrafish embryo was 0.5 mg/L. After 96 h exposure, the 50% lethal concentration (95% confidence interval (CI)) of BCDMH on zebrafish embryo was 8.10 mg/L (6.15-11.16 mg/L). The 50% inhibitory concentration (95% CI) of BCDMH on hatching rate was 7.37 mg/L (6.33-8.35 mg/L). Histopathology showed two types of responses induced by BCDMH, defensive and compensatory. The extreme responses were marked hyperplasia of the gill epithelium with lamellar fusion and epidermal peeling. The histopathologic changes in the gills after 10 days exposure were accompanied by significantly higher catalase activity and lipid peroxidation.

Conclusion: These results have important implications for studies on the toxicity and use of BCDMH and its analogs.