4-(2-chlorophenyl)-N-cyclohexyl-N-ethyl-5-oxo-4,5-dihydro-1H-tetrazole-1-carboxamide

Endpoint summary

Additional information

With regard to hydrolysis, the test item is considered as comparatively resistant to hydrolysis at ambient temperatures with extrapolated half-lives of 319 and 501 days under acidic and neutral conditions, respectively. Under alkaline conditions the test item is faster degradable with an extrapolated half-life of 69 days.

Direct photodegradation in aqueous solution is expected to contribute to elimination of the test substance in the environment to a low extent, only. Taking into account different models half-lives ranging from 64 days to up to > 1 year were determined.

Based on the calculated overall OH rate constant of 28.72E-12[cm³/molecules sec] a half-life of the test substance in air of 4.4 hours corresponding to a chemical lifetime in air of 6.4 hours is assessed using a 12-h day with 1.5E+06 OH radicals/cm³. A more conservative assessment of the overall OH radical rate constant would result in a maximum chemical lifetime of the test substance of about 8 hours in the air. Taking this relatively short lifetime of the test substance in air into account it is to be expected that transport and accumulation in the gaseous phase over large distances is not expected.

With respect to biodegradation the substance to be registered has to be considered as very persistent. In a screening study 0% biodegradation was observed, thus the test substance is not readily biodegradable. Further simulation studies with paddy soils resulted in a maximum half-life of 46 days. However, according to the ECHA document "Guidance on Information Requirements and Chemical Safety Assessment. Chapter R.7b: Endpoint specific guidance. Version 4.0" (2017) the preferred temperature for simulation degradation studies is 12 °C, which corresponds to average temperature of European surface waters. Where this condition is not met a temperature correction should be considered based on the Arrhenius equation and half-lives be re-calculated. For first order kinetics this was done and the half-life of 46 days (at 28 °C) was re-calculated to 199 days (at 12 °C), respectively. These available simulation data on soil biodegradation gained in studies with paddy soils systems are reflecting similar conditions as in water/sediment tests. No alternative metabolism pathway is expected in a new biodegradation simulation study in water/ sediment than in the biodegradation study in soil. Thus, based on a worst case assumption the test substance has to be regarded as being very persistent.

The potential for bioaccumulation was investigated in a study using radiolabeled test substance. The substance accumulated in bluegill sunfish with a total residue kinetic bioconcentration factor of about 275.5 to 289.8 X for whole fish (sum of radio labelled compounds, parent substances, metabolites and mineralization products). When exposure ceases, the residues were depurated with a half-life of about 0.42 to 0.55 days. After 14 days in uncontaminated water 100% of the mean plateau radioactivities were depurated from whole fish in both test levels. Accumulations of total residues in edible parts were less (116.9 – 153.6 X) than in whole fish (275.5 – 289.8 X). Taking into account that about 30% parent compound were detected in edible parts and about 16% parent compound in non-edible (viscera) parts after 15 days of exposure the steady-state-BCF for parent (based on whole fish, wet weight) is about 71, the steady-state-BCF for parent (normalised to 6% lipid content) is about 54. Thus, the substance has a low potential to bioaccumulate in aquatic organisms.

In batch equilibrium experiments with four soils, the sorption behavior of the 14C-labeled substance was investigated. The adsorption constants Kd(ads) calculated from the FREUNDLICH isotherms for the four test soils range from 11.65 mL/g to 47.35 mL/g. The respective Koc(ads)-values range from 1189 mL/g to 2380 mL/g. These values correspond to log Koc values of 3.08 and 3.38, respectively. Based on these Koc-values, the substance is to be considered as a substance with low to slight mobility.

In conclusion the substance is expected to mainly partition to the water compartment with the affinity to bind to suspended organic matter of sediments and soil.