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Environmental Health and Toxicology 2019;e2019006. doi: https://doi.org/10.5620/eht.e2019006    [Accepted]
Acute Toxicity of Copper Hydroxide and Glyphosate Mixture in Clarias gariepinus: Interaction and Prediction using Mixture Assessment Models
Kingsley Kanu
Michael Okpara University of Agriculture, Umudike, Umuahia, Nigeria
Corresponding Author: Kingsley Kanu ,Tel: +2348035238277, Fax: +2348035238277, Email: kanu.kingsley@mouau.edu.ng
Received: February 10, 2019;  Accepted: March 15, 2019.
The study aimed to assess the single and joint lethal toxicity, type of interaction and the extent to which simple mathematical model of concentration addition (CA), independent action (IA) and generalized concentration addition (GCA) could predict the joint toxicity of copper hydroxide and glyphosate mixture in Clarias gariepinus. Static bioassay were setup to determine the individual and combined (based on ratio 1:2) lethal concentrations (LCx) of the pesticides. Data from the static bioassays were then fitted into the synergistic ratio (SR), concentration-addition (relative toxicity unit) (RTU) and isobologram model to determine the type of interaction between the different classes of pesticides, while the CA, IA and GCA models were used to predicted the observed mixture effects. The estimated 24h, 48h, 72h and 96h LC50 for copper hydroxide were 198.66 mg/l, 167.51 mg/l, 138.64 mg/l, and 104.82 mg/l; glyphosate were 162.92 mg/l, 103.88 mg/l, 61.95 mg/l, and 52.6l mg/l; while the mixture were 63.18 mg/l, 59.06 mg/l, 56.42 mg/l, and 50.67 mg/l respectively. Glyphosate was 2 times more toxic than copper hydroxide to C. gariepinus when acting singly. The SR and RTU was < 1 indicate that the interaction between the pesticides was synergistic. Synergism was also corroborated by the isobologram model. The interaction of the mixture of copper hydroxide and glyphosate followed the IA model while the CA and GCA model underestimated the observed mixture effects. The study showed that copper hydroxide was practically non-toxic, while glyphosate and the mixture were slightly toxic to Clarias gariepinus.
Keywords: models; pesticides; prediction; catfish; mixture toxicity
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