Copyright © 2019 The Korean Society of Environmental Analysis Health and Toxicology This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/ licenses/by-nc/4.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. Page 1 of 16 http://eaht.org EAHT Introduction Accelerated urbanization and industrial developments are the major cause of unprecedented increase in worldwide chemical discharge into the environment. In most developing nations, generated chemicals are poorly managed by habitual illegal disposal on available spaces in the environment. More- over, poor enforcement of laws and regulations prohibiting improper discharge of hazardous substances further encour- ages culprits. Most of the discharged chemical and physical agents cause great alterations in the biogeochemical circles of both aquatic and terrestrial ecosystems and in turn compro- mising human and ecosystem health [1]. Metals are the most commonly released chemicals into the environment via mul- tiple direct and indirect sources [2]. A seemingly neglected di- rect source of toxic metal discharge is through chromated copper arsenate (CCA) wood treatment preservative [3-8]. Te individual metals in CCA preservatives exist in varying com- positions, hence they are classifed into Types A, B and C. Te metal compositions range from 2100 - 2300 mg/L chromium trioxide (CrO3), 1200 - 1400 mg/L copper oxide (CuO) and 1800 - 2200 mg/L arsenic trioxide (As2O3). Tis is equivalent to 65.5% (Cr), 18.1% (As) and 16.4% (Cu) in Type A, 35.3% (Cr), 19.6% (As) and 45.1% (Cu) in Type B, and 47.5% (Cr), 18.5% (As) and 34.0% (Cu) in Type C [9]. Irrespective of the variations Experimental modeling of the acute toxicity and cytogenotoxic fate of composite mixtures of chromate, copper and arsenate oxides associated with CCA preservative using Clarias gariepinus (Burchell 1822) Olukunle S. Fagbenro 1 , Chibuisi G. Alimba 1,2 *, Adekunle A. Bakare 1 1Cell Biology and Genetics Unit, Department of Zoology, University of Ibadan, Ibadan, Nigeria; 2Leibniz Research Centre for Working Environment and Human Factors (IfADo), Technical University of Dortmund, 44139 Dortmund, Germany • Original Article Open Access eISSN: 2671-9525 Concurrent occurrence of chromium (Cr), copper (Cu) and arsenic (As) from chromated copper arsenate (CCA) wood preservative in aquatic ecosystems demands that their joint-actions in eliciting toxic effects be assessed for adequate understanding of the health risk they may pose to biota. Clarias gariepinus was exposed to As2O3 , CrO3 and CuO and their composite mixtures (1:1 and 1:1:1) at various concentrations (0 – 600 mg/L) for 96-h to determine the acute toxicity using OECD (1992) protocol. C. gariepinus was then exposed to sub-lethal concentrations corresponding to 6.25, 12.5, 25.0, 50.0 and 100% of the 96-h LC50 for 7 days to assess the cytogenotoxic effects using piscine micronucleus (MN) test. The 96-h LC50 showed that the metals/metalloid demonstrated differential interactions in a concentration dependent pattern. The 96-h LC50 showed that Cr was the most toxic while Cu and As:Cu were indeterminate (Cr > Cr:Cu > As:Cr > As > As:Cr:Cu > Cu = As:Cu indeterminate). Isobologram and synergistic ratio (SR) models predicted antagonistic interaction between Cu:Cr and As:Cr and synergism between As:Cu in the causation of morbidity and mortality of C. gariepinus . Interaction factor model predicted antagonism as common interactive mechanism among the metal/ metalloid mixtures in the induction of MN and abnormal nuclear erythrocytes in C. garipienus. Predicted interactions among the three metals/metalloid were largely antagonism and synergism towards the induction of acute toxicity and cytogenotoxicity. The models employed herein may be useful in establishing environmental safe limits for mixtures of metals/metalloids against the induction of acute toxicity and DNA damage in lower aquatic vertebrates. Keywords: Acute toxicity, antagonistic and synergistic interactions, Clarias gariepinus , joint-action toxicity models, metal mixtures, micronucleus test Received: May 14, 2019 Accepted: September 19, 2019 Corresponding author: Chibuisi G. Alimba ## E-mail: cg.alimba@ui.edu.ng , chivoptera@yahoo.com This article is available from: http://eaht.org Volume: 34(3), Article ID: e2019010, 16 pages https://doi.org/10.5620/eht.e2019010 EAHT Environmental Analysis Health and Toxicology