C. riparius test was conducted according to OECD 218 (2004) test guideline as modified in two non-simultaneous tests. In addition to the emerging time of adults and proportion of emerged adults, also mentum deformities of the 4th in star larvae mouthparts was used as an endpoint. Mentum deformities are commonly used as toxicity indicators in field surveys (Groenendijk et al., 1998) and they have also been studied in standard laboratory tests (e.g. Janssens de Bisthoven et al., 2001).