| At present,there are serious heavy metal and organic pollution problems in the electronic waste dismantling sites at home and abroad.Lead and tetrabromodiphenyl ether?BDE-47?are two representative pollutants in the site of electronic waste disassembly.Currently,there are few studies on the joint toxicity of these two substances,especially the neurotoxicity.Zebrafish is considered as a model for identification of the association between early-life low-dose pollutants exposure and neurological adverse outcomes.In this study zebrafish embryos/larvae were used as research object.Based on the concentration levels of lead and BDE-47 detected in environmental media around the electronic waste dismantling site,the concentrations of lead is 0,5,10,20?g·L-1and BDE-47 is 0,100,200,400?g·L-1,and prepare Pb and BDE-47 mixed exposure solution.Normal zebrafish embryos were exposed in the glass culture dish.The maincontents and results were shown as following:1.Evaluate the developmental toxicity of pollutantsThe culture dish was placed in a light incubator to be cultured after exposed.The embryo hatching,death and deformity were observed under microscope every 24 hours.The developmental toxicity of zebrafish embryos/larvae was induced by Pb and BDE-47exposure,including the decline of hatching rates and survival rates,and the malformation of yolk-edema,pericardial edema and axial spinal curvature.When the concentration of BDE-47 was unchanged,the survival rate and incubation rate of larvae decreased with the increase of Pb concentration.Moreover,when the Pb concentration remained unchanged in the exposed solution,the survival rate and incubation rate of BDE-47 were similar.2.Evaluate the neurobehavioral toxicity of pollutantsWhen exposed to 6dpf,the zebrafish larvae with normal development were randomly selected for behavioral experiments.The test methods of the behavioral effects including locomotor activity,rotation activity and social activity were established with Zebrabox,which lasted 30 min.?1?LocomotionThe test end point is the movement trajectory and total amount of movement.The results showed that lead exposure did not significantly affect the operation behavior of zebrafish larvae under light conditions.In addition,the BDE-47 exposure of 100?g·L-11 and400?g·L-1,can induce the occurrence of significant Hypoactivity in larvae?P<0.05?.In the dark conditions,the exposure of 20?g·L-1lead exposure as well as the BDE-47 exposure of200?g·L-1and 400?g·L-1could induce significant decrease in activity of the larvae?P<0.05?.In the BDE-47+Pb joint exposure?200+5Pb,400+5Pb,100+20Pb,200+20Pb,400+20Pb?6 groups can induce the occurrence of significant activity decrease under light test conditions.And 200+5Pb,400+5Pb,200+10Pb,400+10Pb,100+20Pb,200+20Pb,400+20Pb total 7 combined exposure group can induce significant activity decrease in larvae during dark cycle?P<0.05?.It is speculated that the combined exposure of Pb and BDE-47 has synergistic effect on the activity of zebrafish larvae due to the significant decrease in the activity of larvae in the combined exposure group,so the joint exposure is more toxic.?2?Rotation and Path angleThe test end point is the number of times and the total number of turns of the fish in the range of different paths.The results showed that the larvae of all exposed groups were more inclined to the right,and the environmental pollutants Pb and BDE-47 could not change the path Angle and bias preference of zebrafish.In the light condition,either lead or BDE-47 alone did not change the steering behavior of zebrafish larvae.In the dark conditions,the exposure of 10?g·L-11 and 20?g·L-11 lead exposure and 400?g·L-11 BDE-47exposure induced a significant decrease in the number of steering times?P<0.05?.In the joint exposure of BDE-47+Pb?200+5Pb,400+5Pb,200+20Pb,400+20Pb?4 groups can induce a significant decrease in the steering frequency of larvae under dark test conditions.And 400+5Pb,100+20Pb,200+20Pb,400+20Pb total 4 combined exposure group can induce the number of redirection of larvae in the light cycle significantly decreased?P<0.05?.?3?Social behaviorThe test end point is the contact time and contact number of the larvae.The results showed that lead exposure did not significantly affect the social behavior of zebrafish larvae under dark conditions.However,under the light conditions,the exposure of the 20?g·L-1lead significantly changed the social behavior of the larvae,especially the social frequency.The low concentration of BDE-47 was not significantly affected by the social behavior of zebrafish larvae.However,the exposure of the high concentration of 400?g·L-11 BDE-47significantly changed the social time of the larvae.In the joint exposure of BDE-47+Pb?200+5Pb,400+5Pb,200+20Pb,400+20Pb?,the social time of the 4 groups of young fish in the light condition was significantly higher than that in the control group?P<0.05?.In the dark conditions,there was a significant increase in social time between 200+5Pb,200+20Pb and 400+20Pb.In addition,only 400+10Pb in the combined exposure group showed a significant increase in the social frequency of larvae.3.The detect of Pb and BDE-47 in water and 6dpf larvaeThe content of Pb and BDE-47 in water and 6dpf larvae were respectively detected by ICP-MS and GC-ECD.The results showed that there was no significant difference between Pb and BDE-47 in the combined exposure group compared with the single exposure group.The intake of Pb was significantly lower than that of Pb in the combined exposure group of6dpf?P<0.05?.It is indicated that the presence of BDE-47 will inhibit the uptake of Pb by larvae.Impaction and joint exposure of BDE-47 intake is associated with exposed liquid lead concentrations,5?g·L-11 and 20?g·L-11 Pb impaction on the uptake of BDE-47 have a significant role in promoting,and 10?g·L-1Pb for young fish intake BDE-47 has significant inhibitory effect?P<0.05?. |
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