Environmental issues have become a growing concern in the last few years. One of these issues is the production and accumulation of large-tonnage waste, which includes waste oils. Scientists conduct intensive research on a way of their disposal. In order to develop a safe and efficient way of disposing of waste oils, it is necessary to know their toxicological characteristics, which are the focus of this paper. We conducted a toxicological assessment beforehand by calculating the hazard level of the waste to the environment and subsequently verified by bio testing. We used the species Ceriodaphnia affinis, which belong to the lower crustacean subclass, as a test subject. Based on the results of the bio testing, we determined the concentration at which 10% mortality occurs, the dilution rate of the aqueous extract at which no harmful effects on hydrobionts occur, and, as a result, the class of waste hazard. With knowledge of the class of hazard, it is possible to establish and select the safe process and working conditions, develop the necessary technical and environmental documentation, and ensure that the chosen technology is environmentally friendly.