Environmental risk assessment of antibiotics: an intensive care unit analysis

Hospital effluents have been usually known by the microbiological pollution they cause, but only recently they have been considered a significant source of aquatic environmental pollution due to the presence of medicines in these effluents. In this context, an environmental risk assessment (ERA) is presented for the most used intravenous antibiotics in the Intensive Care Unit (ICU) of a hospital in Curitiba (Brazil). The amount of antibiotics used in the ICU was evaluated during 18months (June 2006 until November 2007), in order to calculate the Predicted Environmental Concentration (PEC1). Antibiotic excretion data (on its original form) and the removal of the selected drugs in the sewage treatment plants based on the activated sludge system were used to calculate, respectively, PEC2 and PEC2r. The Predicted No-Effect Concentration (PNEC) of pharmaceuticals was also considered to assess the environmental risk by calculating the PEC/PNEC ratios. All PECs were 1ngL(-1). The worst-case PEC estimations (PEC1 and PEC2) were observed for sodic ceftriaxone, sodic cefazolin, meropenem, ampicillin, cefepime and sodic piperacillin. PEC/PNEC ratios showed that, given the present pattern of usage, high aquatic environmental risk is expected for these antibiotics. Further studies should be carried out to elucidate their contribution to increasing antimicrobial multi-drug-resistant species.