Dicyclohexylamine

Biodegradation in water: screening tests

Description of key information

Dicyclohexylamine is considered readily biodegradable. The biodegradation of dicyclohexylamine was investigated in the closed bottle test, comparable to the OECD TG 301D, with predominantly domestic sewage. After 10 days 72% biodegradation was observed and after 20 days 96 % of the test substance was degraded (Bayer AG, 1975a). In an aerobic ready test performed according to the national Japanese standard method comparable to the OECD TG 301C guideline,  biodegradation of 76.9 % was observed after a period of 14 days (Kawasaki, 1980; MITI (Ministry of International Trade and Industry, 1992)).

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable

Additional information

There are two key studies for biodegradation in water. First key study - an aerobic ready test was performed according to the national Japanese standard method comparable to the OECD TG 301C guideline. Considering the acid dissociation constant value of 10.39, reported pH ranges of 6.3 to 6.9 at the beginning and 8.4 to 8.6 at the end of the biodegradation study (OECD 301C), and water solubility of 0.8 g/l, it can be concluded that almost all of the substance is present in the protonated form. After a period of 14 days 76.9 % biodegradation was observed (Kawasaki, 1980; MITI (Ministry of International Trade and Industry, 1992)). In second key study - the closed bottle test, comparable to the OECD TG 301D with predominantly domestic sewage, the biodegradation of dicyclohexylamine was investigated. After 10 days 72% biodegradation was observed and after 20 days 96 % of the test substance was degraded (Bayer AG, 1975a). There are also some others reliable studies (data assessed as 2 according to Klimish scores) in the OECD Screening Information DataSets (SIDS) for DCHA: In the study on Biochemical Oxygen Demand (BOD) where natural surface water from the Ohio River (USA) was used as seed material, BOD5 of 20 mg/l was observed, related to 200 mg test substance/l. In Bench scale pilot plant test over the test period over 20 days the reactor lost more than 98 % of the total initial biomass in the aerator. Dicyclohexylamine might affect the ability of the biomass to flocculate. Biodegradability of 500 μg/mL dicyclohexylamine by acclimated sewage sludge enrichment cultures as measured by protein yield was 29 μg/mL. An increase in cellular protein to at least 20 μg/mL was considered positive for biodegradability.