Aquatic hazard and risk assessment of two selected substances produced in high volumes in the Slovak Republic

In the EU, the work on the development of a standardised guidance for risk assessment of chemical substances has been going on for the latest few years. The principles in this guidance were used for assessing the aquatic risk of two substances: caprolactamte [105-60-2] and diphenylamine [122-39-4], which are produced and used in large quantities in the Slovak Republic. Standard laboratory tests on toxicity to the algae Kirchneria subcapitata and to Daphnia magna were conducted for both substances, and for diphenylamine also tests on sludge respiration activity and ready (Closed Bottle test) and inherent (Modified MITI II test) biodegradability. Based on the generic European scenario for release and environmental distribution defined in the EU risk assessment guidance, predicted aquatic concentrations for a local environment (PEClocal) were estimated and compared with the predicted no-effect-concentration for the aquatic environment (PNECaquatic). The ratio, defined as the risk quotient, showed that both substances should be considered of high risk for the aquatic environment (risk quotient of 290 and 1300 for caprolactame and diphenylamine, respectively). However, modifying the calculation of PEClocal to local Slovak conditions reduced the risk quotients to 0.1 and 5.3 for the two substances, respectively. Thus, the generic scenario defined in the EU risk assessment guidance may be considered conservative compared to the realistic local aquatic environments in the Slovak Republic.