Comprehensive Toxicity Study Of Dechlorane Plus On Zebrafish

Dechlorane Plus (DP), also known as a chlorinated flame retardant, is recently identified in the environment, with a high production volume. Recent studies have showed that DP can be disseminated by air and water, bioaccumulate in organisms and thus exist persistently. DP was introduced as a substitute for Mirex and Mirex has been banned because of its impact on the environment. However, toxicity data for DP are scarce and essentially all from a USEPA HPV Test Challenge report and a manual from its manufacturer, OxyChem. There is an urgent need for more researches on DP toxicity and biological mechanism to give more objective toxicological evaluations on this fast-growing flame retardant.In this paper, acute toxicity and sub-acute toxicity of DP on zebrafish embryos and adults were investigated, and the toxic risk of DP in current environment was evaluated.In acute toxicity study, zebrafish embryos were exposed to different doses of DP for up to 7 days, using acetone, ethanol and DMSO as carrier solvents, respectively. Obvious dose-dependent effect and time-dependent effect were showed on rate of spine side curve, rate of cardiac edema and malformation rate in DP exposed zebrafish using acetone as solvent. No significant change was found on mortality rate in DP exposed zebrafish using all three solvents. Compared with ethanol and DMSO, acetone showed the least toxixity to zebrafish embryos.In sub-acute toxicity study, six-month adult zebrafish were treated with DP at doses of 0.25,0.5,2.5,7.5 and 10 mg DP/g bw (body weight) by gavage for 7 days. DP accumulation and fsyn value in exposed zebrafish were measured by GC-MS subsequently. Results demonstrated DP could be bioaccumulated and led to a decrease in fsyn value in zebrafish, suggesting syn-and anti-DP may have different metabolic pathways in zebrafish.Additionally, six-month adult zebrafish were treated with DP at doses of 0.25,2.5 and 7.5 mg DP/g bw by gavage for 1,7,14 and 28 days, respectively. The effects of DP on superoxide dismutase (SOD) activity, cell apoptosis in intestine and gene expression in zebrafish were investigated, subsequently. Results showed siginificant increases of SOD activity in DP exposed groups, compared with the controls. This obvious dose-dependent effect on SOD activity illustrated DP might induce the accumulation of superoxide radicals and thus result in the increasing of SOD activity to scavenge these extra superoxide radicals. Obvious apoptosis were illustrated in zebrafish intestine after 7,14 and 28-day exposure in DP at the dose of 7.5 mg DP/g bw. Different gene expression pattern of sod, p53 and bcl2 were presented in different doses of DP exposed zebrafish, as well as after different time exposure.Since the effective biological concentration of DP obtained in this thesis is far more than the real DP concentration in current environments or some animals, the evaluation of toxic risk of DP in current environments is low or nil.To sum up, results obtained in this thesis revealed the biological effectiveness and toxicity of DP to aquatic animals and was undoubtedly of great significance in toxicity evaluation of DP in environment.