Butanoic acid, 3a,4,5,6,7,7a-hexahydro-4,7-methano-1H-indenyl ester

Endpoint summary

Description of key information

Abiotic degradation:

Air: Based on estimation with the QSAR model Aopwin Cyclobutanate undergoes in air rapid degradation after reaction with hydroxyl radicals or ozone. The DT50 values after reaction with hydroxyl radicals and ozone are 1.9 hours and 1.4 hours, respectively. Based on these half-lives, Cyclobutanate will not reach the stratosphere and is therefore not considered to be a long-range transported chemical in air.

Cyclobutanate does not have an ozone depletion potential because it does not contain halogens and does not have the potential to reach the stratosphere EU CLP (EC no 1272/2008 and its amendments).

Water: Based on a study performed on Cyclobutanate the half-life time at 25°C is estimated to be > 1 year for pH 4 and 7 and 13 days for pH 9. It can be concluded that Cyclobutanate is hydrolytically stable at low and neutral pH, whereas hydrolysis does occur at higher pH.

Biotic degradation:

In a screening study according to OECD TG 301B 43% biodegradation was found after 28 days. Under these conditions Cyclobutanate was not readily biodegradable. In two other ready biodegradation studies (OECD TG 301C) the biodegradation % was 34 and 22%, and after 28 days no Cyclobutanate could be detected, only degradants. In the test where 34% degradation was found the degradant was identified as Cycla-alcohol and present at 66%, completing the mass balance.

Bioaccumulation:

Bioaccumulation test on aquatic species is based on the available information (log Kow and calculated BCF values). The BCF for aquatic organisms was calculated using the QSAR of Veith et al.(1979), incorporated in the EUSES model, using the log Kow of 4.48 results in a BCF of 232 l/kg wwt

The BCF in earthworms was estimated with the equation from Jager (1998) which is incorporated in the EUSES model. With the log Kow value of 4.48 for the substance the BCFearthworm results in 363 l/kg ww (earthworm).

The bioaccumulation in air-breathing organisms is considered negligible because Cyclobutanate is fully degraded in the STP after 28 days into CO2 (34%) and Cycla-alcohol (66%) showing complete de-esterification, resulting in complete primary biodegradation. This de-esterifcation is a common pathway due to the abundant presence of carboxylesterases. The Cycla-alcohol is a secondary alcohol which will be glucuronidated during Phase 2 metabolism and thereafter excreted in the kidneys as is seen in the repeated dose toxicity studies (for references see Toxico-kinetic section). In addition, the DT50 is 0.34 day calculated by BCFBAF.

Transport and distribution:

The adsorption coefficient (Koc) of Cyclobutanate has been determined to be 1510, using the HPLC screening method (OECD121). This indicates that the substance will have a moderate potential to adsorb to sediment/soil.

The Henry's Law Coefficient was estimated by EUSES, based on the measured vapour pressure (11.2 Pa at 25°C) and water solubility 11.5 mg/l at 20°C). For Cyclobutanate this results in: Henry coefficient at 25°C is 10.9 and 12°C it is 5.22 Pa-m3/mol.

Based on Level III distribution modelling using EPISUITE (assuming equal and continuous releases to air, water and soil) using SMILES formula CCCC(=O)OC3CC1CC3C2CC=CC12 (The Cas no of Cyclobutanate presents a mistake in the chemical structure) and the measured physico-chemical parameters, water solubility and log Kow as input, it is estimated that the majority of the substance released to the environment will partition mainly into soil (80%) and water (18.5%) with small amounts to sediment and air (both <1%).

The SimpleTreat model, which is incorporated in EUSES, simulates the distribution of the substance in a Sewage Treatment Plant. The results of this show that the substance will not be degraded and that 77.2% of the substance will partition to water, 15.4% to sewage sludge and 7.35% to air.