Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)The occurrence of illicit drugs in natural waters (surface, source and drinking water) is of interest due to the poor sanitation coverage and the high consumption of drugs of abuse in Brazil. In addition, little is known about the effects of these compounds on aquatic organisms and human health. This work investigates the occurrence of cocaine (COC) and its major metabolite, benzoylecgonine (BE), in surface and drinking water collected in rivers from a populated geographic area in Brazil. Surface water samples were collected in 22 locations from 16 different rivers and one dam from sao Paulo State, whereas drinking water samples were collected in 5 locations. Samples were collected during the dry and wet season. Among the 34 surface water samples analyzed, BE was detected above the LOD in 94%, while COC in 85%. BE concentrations ranged from 10 ng L-1 to 1019 ng L-1 and COC concentrations from 6 ng L-1 to 62 ng L-1. In the drinking water samples analyzed, BE and COC were found in 100% of the samples analyzed. For BE, concentrations were found in the range from 10 ng L-1 to 652 ng L-1, and COC was quantified in concentrations between 6 and 22 ng L-1. These concentrations are one of the highest found in urban surface waters and may pose some risk to aquatic species. However, no human health risk was identified using the Hazard Quotient. BE is proposed as a reliable indicator of sewage contamination in both source and drinking water. (C) 2016 Elsevier B.V. All rights reserved.576374380INCTAA (FAPESP) [2008/57808-1]CNPq [573894/2008-6]IQ-UNICAMPCAPESFundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)