Combined toxicities of binary mixtures of alachlor, chlorfenvinphos, diuron and isoproturon M. Sigurnjak a ,  S. Uki  c a, * , M. Cvetni  c a , M. Marki  c a , M. Novak Stankov a , B. Rasulev b , H. Ku  si  c a , A. Lon  cari  c Bo  zi  c a , M. Rogo  si  c a , T. Bolan  ca a a University of Zagreb, Faculty of Chemical Engineering and Technology, Maruli cev Trg 19, 10000, Zagreb, Croatia b North Dakota State University, Department of Coatings and Polymeric Materials, Fargo, ND, 58102, USA highlights  Toxicities were determined toward Vibrio fischeri.  Alachlor, chlorfenvinphos, diuron, and isoproturon were examined.  Joint toxicity effects in binary pesticide-mixtures were analyzed.  Isoproturon and chlorfenvinphos indicated synergistic toxic activity.  Other binary combinations indicated additive behavior. article info Article history: Received 2 August 2019 Received in revised form 23 September 2019 Accepted 24 September 2019 Available online 25 September 2019 Handling Editor: Willie Peijnenburg Keywords: Vibrio fischeri Pesticides Binary mixtures Concentration addition Independent action abstract Pesticides are the chemicals of increased concern regarding their adverse environmental effects. In particular, the reports on their joint toxicity effects are scarce in the literature. Therefore, this paper describes the experiments on toxicities of four pesticides: alachlor, chlorfenvinphos, diuron, and iso- proturon, toward Vibrio fischeri. In particular, the joint toxicity effects for all possible binary combinations of the pesticides were analyzed. The analysis included the application of concentration addition and independent action models at two toxicity levels: EC 10 and EC 50 . The analysis revealed additive behavior between all pesticide pairs. The only exception was isoproturon and chlorfenvinphos whose combination resulted in synergistic toxic activity. The original form of the logistic function was given preference over the linearized form in describing the responseedose relationships of investigated pesticides. © 2019 Elsevier Ltd. All rights reserved. 1. Introduction Due to increasing world population and steady economic growth, the availability of clean, high-quality water will become one of the most important problems of the mankind in near future. For quite some time, numerous novel substances are commonly found in waters, especially surface ones, and their origin is mostly anthropogenic. Unfortunately, water-monitoring usually includes well-known hazardous substances only, although many of the remaining ones are suspected to be more or less harmful as well. Therefore, European Union (EU) Commission established the so- called “Watch List” (EUR-Lex, 2015, 2018), a list of emerging or little-known pollutants that have to be monitored for a while and later potentially included in the priority list of pollutants of EU’s Water Framework Directive (WFD) (EUR-Lex, 2000, 2013). Pesticides are of special concern among the priority pollutants. Although they have numerous beneficial effects, especially regarding the increase of food availability and price, pesticides are generally designed to be toxic (Kaur et al., 2019) and many of them have long environmental persistence (Damalas and Koutroubas, 2016; Lushchak et al., 2018). Their mode of action is by targeting systems or enzymes in the pests which may be identical or very similar to systems or enzymes in other living beings, including * Corresponding author. University of Zagreb, Faculty of Chemical Engineering and Technology, Department of Analytical Chemistry, Maruli cev trg 19, 10000, Zagreb, Croatia. E-mail address: sukic@fkit.hr (  S. Uki c). Contents lists available at ScienceDirect Chemosphere journal homepage: www.elsevier.com/locate/chemosphere https://doi.org/10.1016/j.chemosphere.2019.124973 0045-6535/© 2019 Elsevier Ltd. All rights reserved. Chemosphere 240 (2020) 124973