Research On The Enrichment And Purification Of Hexabromocyclododecanes In Zebrafish And Its Interference Effects On Thyroid

Hexabromocyclododecanes(HBCDs)are the third most highly produced brominated flame retardants(BFRs).They are used mainly in electronic equipment,building materials and plastic products.Because of their long-distance migration,persistence and bioaccumulation,HBCDs have received an increasing concern of scientists around the world.Till now,the environment fate of HBCDs have been extensively studied.However,it is not given a clear statement on the bioaccumulation and endocrine disrupting of HBCDs in biota and humans.Based on the current research status of HBCDs,zebrafish were exposed to three dietary concentrations of HBCDs(0?10?100?400ng/g)for 56 days,and followed by clean food for 21 days.In order to research the enrichment and purification of HBCDs in zebrafish,HBCD enantiomers in zebrafish were determined using ultra performance liquid chromatography tandem mass spectrometry(UPLC-MS/MS).To investigate the effects of long-term exposure to HBCDs with different doses on thyroid dysfunction and oxidative stress in zebrafish,the concentrations of thyroid hormone(T3?T4?FT3?FT4)and the activities of malondialdehyde(MDA),superoxide dismutase(SOD),catalase(CAT)and reduced glutathione(GSH)were detected by reagent kit.The conclusions of the study are as follows:(1)Compared with control group,zebrafish in three exposed groups showed no significant difference in fatness and growth rates,which indicated HBCDs has little effect on the growth of adult zebrafish.(2)UPLC-MS/MS was used to detect the concentrations of HBCDs in zebrafish of different exposed groups at different time.The result showed that there were three main reasons for the existence of ?-HBCD as the major isomer in the organism: the enrichment rate of ?-HBCD in organism was higher than that of ?-HBCD and ?-HBCD;the transformation of ?-HBCD and ?-HBCD to ?-HBCD;the metabolic rates of?-HBCD and ?-HBCD were higher than that of ?-HBCD.(3)After exposure of 56 d,HBCDs had significant inhibitory effect on T3 and T4 in liver of adult zebrafish.Compared with the control group,the ratio of T3 and T4 in the medium and high concentration group was significantly higher.The content of FT3 and FT4 in the liver tissue of zebrafish increased first and then decreased with the increase of exposure concentration.The results showed that HBCDs had a significant interference effect on thyroid of zebrafish,which was mainly associated with the concentration of ?-HBCD in zebrafish.(4)With the increase of exposure concentration,the content of MDA in zebrafish liver decreased firstly and then increased.The activity of SOD and CAT in zebrafish liver showed the opposite trend with MDA.And the concentration of GSH in liver decreased gradually,which showed a significant dose-effect relationship.The results showed that HBCDs could cause oxidative damage to zebrafish.And it was mainly associated with the concentration of ?-HBCD in zebrafish.(5)Based on available datas and experimental datas,it is a serious threat to human health of the high concentration of HBCDs in activated sludge from urban sewage and industrial wastewater treatment plants.