Nowadays, due to the rapid growth of the population, there is an increasing human demand for numerous organic and inorganic substances. Large-scale production of pharmaceuticals, pesticides, personal care products and the like requires the disposal of a large amount of waste. Although there are successful ways of disposing the waste, as a result of the metabolism of living beings, as well as the uncontrolled human activity, numerous synthetic substances in very low concentrations reach the environment every day. Since they reach the environment anthropogenically, these substances are called xenobiotics. Unfortunately, due to the fact that they are found in the environment in very small concentrations, they often remain in the environment for a long time, and can have a strong ecotoxic effect on individual members of the ecosystem. This study examines their negative effect on individual microorganisms, in order to determine their true harmfulness and to potentially find a way of their disposal. The xenobiotics tested in this work are pharmaceuticals diclofenac and pantoprazole, with working concentrations of 0.125 mg L^-1, 0.5 mg L^-1, 2 mg L^-1, 8 mg L^-1 and 16 mg L^-1. Their mixtures were also tested in diclofenac and pantoprazole ratios of 1:1, 1:2 and 2:1 to determine their interaction. The microorganisms on which the tests were carried out were marine bacteria Vibrio fischeri, bacteria Pseudomonas putida, microalgae Chlorella sp. and yeast Saccharomyces cerevisiae. The results showed that pure xenobiotics, as well as their mixtures, have a strong ecotoxicological impact on Vibrio fischeri and Saccharomyces cerevisiae, while pure diclofenac has a fatal effect on only 5% of the population of Pseudomonas putida with an effective concentration of 9.3 mg L^-1 and on 5% of the population Chlorella sp. with an effective concentration of 0.8 mg L^-1.