Toxicity assessment of caffeine, fluoxetine and their mixture on Daphnia similis

Abstract

Emerging pollutants have already become a global problem, and they have been detected in dozens of countries, including Brazil. Even at very low concentrations, most of the emerging compounds are able to induce changes into biochemical system of aquatic organisms and they have also been reported as negative products to human health. Pharmaceuticals are considered as emerging contaminants detected in estuarine environment, in wastewater treatment facilities, lakes and rivers and even in sea waters. Generally the pharmaceuticals are detected among many other compounds into the ecosystem. The interaction of mixtures of contaminants is an important issue to be considered in monitoring programs as well as the negative effect to aquatic biota. The aim of the present paper was the assessment of toxic effects of pharmaceuticals exposed to Daphnia similis crustacean, individual and combined mixture of caffeine and fluoxetine. Caffeine (CAF) is a stimulant with cardiac, cerebral, diuretic and respiratory effects while Fluoxetine (FLX) is a selective serotonin re-uptake inhibitor, widely prescribed as antidepressant, (also known as Prozac®). The juveniles of D. similis were exposed separetaly to both caffeine (100mg/L) and to fluoxetine (20mg/L), and to a mixture of both (50mg/L caffeine and 20mg/L fluoxetine). Several experimental trials of acute immobilization test were performed. EC50 values ranged from 29,7 to 31 mg/L-1 for caffeine, and from 1.0 to 1.4 mg/L-1 for fluoxetine. Antagonistic effects of binary mixtures (EC50 = 15.2%) were observed. A chronic reproduction test was performed for the mixture of pharmaceuticals. We observed effects on D.similis survival, after 5 days. The mixture led to decrease of 72% in the reproduction, in maximum concentration (2.5% of the mixture – CAF 50ppm + FLX 20ppm). Concerning the importance of assessing toxicity the elected pharmaceuticals concentration were higher than those detected in the envinroment. These results may be incorporated into risk assessments analysis in order to protect sensitive aquatic ecosystems more effectively.