ABSTRACT
Objective @#To investigate the effects of the exposure of sludge from sewage treatment plants and microplastic extracted from sludge on the oxidative stress levels in zebrafish, so as to put insights into the research into the impact of sludge and microplastics on human health. @*Methods @#Adult wild AB zebrafish were exposed to five groups of sludge (0, 12.5, 25, 50 and 75 g/L) and four groups of microplastics extract from sludge (0, 240, 480, 960/L), with 24 zebrafish in each group. The color, activity and death of zebrafish were observed every day. The contents of superoxide dismutase (SOD), catalase (CAT), glutathione (GSH) and malondialdehyde (MDA) were detected 0 h, 24 h, 48 h, 72 h, 96 h and 7 d post-exposure. A two-factor ANOVA was used to analyze the effects of different concentrations and time of exposure on the indicators above. @*Results @#Under 75 g/L sludge exposure, zebrafish began to show mortality at 72 h and all died after 7 d. The zebrafish in the other sludge groups and all microplastic groups had normal color and activity, and no mortality was observed. Sludge concentration interacted with exposure time to affect SOD, CAT, GSH and MDA (P<0.05). With increasing sludge concentration and exposure time, SOD decreased, MDA increased, CAT increased first and then decreased, GSH decreased first and then increased, and GSH continued to decrease since 24 h in the 75 g/L group. The microplastic concentration interacted with exposure time to affect SOD and GSH (P<0.05), but not CAT or MDA (P>0.05). With increasing microplastic concentration and exposure time, SOD and MDA increased, CAT increased first and then decreased, the GSH was slightly increased at 24 h and decreased after 72 h.@*Conclusion @#Both sludge and microplastics extracted from sludge can induce oxidative stress damage in zebrafish, and exposure time and concentration can interact to affect oxidative stress levels. The microplastics extracted from sludge have less effect on oxidative stress levels in zebrafish than sludge.