Photochemical and ecotoxicological studies on corticosteroids

During the last years many studies of the impact of chemical pollution have focused on pharmaceuticals since most of these chemicals have been found in the environment. Prednisone, one of the most widely prescribed medical substances in the United States during the last five years, is a corticosteroid used for many conditions of human health. Pharmacokinetics studies in man have proved that about 10% of prednisone is metabolized to prednisolone. High levels of both drugs are excreted through urine and carried by sewage effluent into surface waters, where they may be subjected to modifications by sunlight. The photochemical behavior of prednisone and prednisolone in water was studied by irradiation of aqueous suspensions by a solar simulator. The several photoproducts obtained have been isolated by chromatographic techniques and identified on the basis of their physical features. All chemicals have been tested to evaluate their effects on freshwater organisms from different trophic levels. Toxicity tests have been performed on the bacterium Escherichia coli, the alga Selenastrum capricornutum, the rotifer Brachionus calyciflorus, the cladoceran Daphnia pulex and the anostracan Thamnocephalus platyurus.