Effects of Exposure to Ibuprofen and Acetaminophen Mixtures in Oreochromis niloticus Juveniles

Abstract

Ibuprofen and acetaminophen are among the frequently detected pharmaceuticals in various environmental matrices. As drugs in mixtures may interact in water affecting the toxicity of single compounds, the present study examined the effects on Oreochromis niloticus exposed to mixtures of waterborne ibuprofen and acetaminophen at two selected sublethal concentrations over 14 days. Juvenile fish (size range 4.50 - 6.00 cm and 2.00 - 3.50 g weight) were maintained in 15 glass tanks filled with 11 L of aged municipal water (n=7 per tank), arranged in a completely randomized design with a control group (C), T1 (ibuprofen at 10 µg/L), T2 (acetaminophen at 10 µg/L), T3 (ibuprofen and acetaminophen at 5 µg/L each) and T4 group (two drugs at 10 µg/L each) in three replicates. Exposure levels were selected based on reported predicted no-effect concentrations and environmentally relevant levels. Temperature, conductivity, pH, total dissolved solids, and dissolved oxygen in each tank were monitored throughout the experiment. On completion of 14 days of exposure, individual fish were sampled randomly and serially to get data on three behavioral endpoints (ventilation rate, food detection time, and response to tactile stimulus), and on erythrocyte nuclear abnormalities (ENA). Exposure to mixtures of two pharmaceuticals (T3 and T4) showed lower positive responses to the tactile stimulus (p<0.05), and higher food detection times (ANOVA, p<0.05) than those of respective single drugs (T1 and T2). Moreover, T4 caused a significantly lower ventilation rate (p<0.05) in the fish compared to both single drugs as well as the mixture at the lower concentration (T3). Significantly higher ENA frequencies (p<0.05) were found in all treatment groups compared to the control including micronuclei, notched nuclei, lobed nuclei, blebbed nuclei, nuclear buds, and fragmented apoptotic nuclei. Moreover, a dose-dependent impact on nuclear morphology was observed in the groups exposed to drug mixtures. The study concludes that the mixture of ibuprofen and acetaminophen at a concentration of 10 µg/L of each exerts likely synergistic exposure effects on O. niloticus juveniles.