Ecotoxicological effects of carbofuran and oxidised multiwalled carbon nanotubes on the freshwater fish Nile tilapia: Nanotubes enhance pesticide ecotoxicity Janaína Campos-Garcia a , Diego Stéfani T. Martinez b,c , Oswaldo L. Alves b , Antônio Fernando Gervásio Leonardo d , Edison Barbieri a,e,n a Programa de Pós Graduação do Instituto de Pesca-SP- APTA-SAA/SP, Caixa Postal 157, Cananéia, SP 11990-000, Brazil b Laboratório de Química do Sólido (LQES), Instituto de Química, Universidade Estadual de Campinas-UNICAMP, Caixa Postal 6154, Campinas, SP 13081-970, Brazil c Laboratório Nacional de Nanotecnologia (LNNano), Centro Nacional de Pesquisa em Energia e Materiais – CNPEM, Caixa Postal 6192, 13083-970 Campinas, SP, Brazil d Polo Regional Vale do Ribeira. Rodovia BR 116, km 460 Caixa Postal 122-CEP 11900-000 Registro, SP, Brazil e Instituto de Pesca – APTA-SAA/SP, Caixa Postal 157, Cananéia, SP 11990-000, Brazil article info Article history: Received 18 April 2014 Received in revised form 2 October 2014 Accepted 6 October 2014 Keywords: Interaction Carbon nanotubes Aquatic ecotoxicology Nanotoxicity abstract The interactions of carbon nanotubes with pesticides, such as carbofuran, classical contaminants (e.g., pesticides, polyaromatic hydrocarbons, heavy metals, and dyes) and emerging contaminants, including endocrine disruptors, are critical components of the environmental risks of this important class of car- bon-based nanomaterials. In this work, we studied the modulation of acute carbofuran toxicity to the freshwater fish Nile tilapia (Oreochromis niloticus) by nitric acid treated multiwalled carbon nanotubes, termed HNO 3 –MWCNT. Nitric acid oxidation is a common chemical method employed for the pur- ification, functionalisation and aqueous dispersion of carbon nanotubes. HNO 3 –MWCNT were not toxic to Nile tilapia at concentrations ranging from 0.1 to 3.0 mg/L for exposure times of up to 96 h. After 24, 48, 72 and 96 h, the LC 50 values of carbofuran were 4.0, 3.2, 3.0 and 2.4 mg/mL, respectively. To evaluate the influence of carbofuran-nanotube interactions on ecotoxicity, we exposed the Nile tilapia to different concentrations of carbofuran mixed together with a non-toxic concentration of HNO 3 –MWCNT (1.0 mg/ L). After 24, 48, 72, and 96 h of exposure, the LC 50 values of carbofuran plus nanotubes were 3.7, 1.6, 0.7 and 0.5 mg/L, respectively. These results demonstrate that HNO 3 –MWCNT potentiate the acute toxicity of carbofuran, leading to a more than five-fold increase in the LC 50 values. Furthermore, the exposure of Nile tilapia to carbofuran plus nanotubes led to decreases in both oxygen consumption and swimming capacity compared to the control. These findings indicate that carbon nanotubes could act as pesticide carriers affecting fish survival, metabolism and behaviour. & 2015 Published by Elsevier Inc. 1. Introduction Fish populations are susceptible to environmental impacts, such as industrial waste, oil spillage, dyes, pesticides, herbicides, and other agents. Sites used for the cultivation of fish and other aquatic organisms are often exposed to water contaminated with agrochemicals due to their proximity to fields used for the culti- vation of vegetables treated with these substances. The freshwater fish Nile tilapia (Oreochromis niloticus) has been used as an organismal model in many studies aiming to evaluate the eco- toxicological effects of different chemicals on the survival, meta- bolism and reproduction of fish (Hernandéz-Moreno et al., 2011; Barbieri and Ferreira, 2011; Harmon, 2012). Pesticides are agrochemicals that are introduced to the en- vironment to maximise agricultural production by protecting crops from potentially harmful agents such as rodents, fungi and weeds and to protect crops from various diseases. Carbofuran [2.3- dihydro-2.2-dimethyl-7-benzofuranil methyl carbamate] is a ne- maticidal and insecticidal agent with a broad spectrum of action. This compound has been registered for problematic uses by the Environmental Protection Agency (EPA, 1976). Carbofuran is con- sidered to be highly toxic to fish (Trotter et al., 1991), and as such it Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/ecoenv Ecotoxicology and Environmental Safety http://dx.doi.org/10.1016/j.ecoenv.2014.10.005 0147-6513/& 2015 Published by Elsevier Inc. n Corresponding author at: Instituto de Pesca – APTA-SAA/SP, Caixa Postal 157, Cananéia, SP 11900-000, Brazil. E-mail address: edisonbarbieri@yahoo.com.br (E. Barbieri). Ecotoxicology and Environmental Safety 111 (2015) 131–137