The toxicity potential of pharmaceuticals found in the Douro River estuary (Portugal): Assessing impacts on gonadal maturation with a histopathological and stereological study of zebrafish ovary and testis after sub-acute exposures

► The effects of non-steroidal pharmaceuticals were assessed in the gonadal maturation of zebrafish. ► Carbamazepine, fenofibric acid, propranolol, trimethoprim and sulfamethoxazole were tested individually and in mixtures (low and high levels). ► Histological and stereological analyses showed a decreasing trend of the late mature stages and an increase in immature gametes, in both sexes. ► The females seemed to be more sensitive to mixtures and males to single compounds. ► Reproductive toxicological effects caused by these pharmaceuticals, even at low environmental levels, should not be overlooked.