Exo-1,7,7-trimethylbicyclo[2.2.1]hept-2-yl propionate

Endpoint summary

Additional information

Abiotic degradation:

Air:

No experimental data on the phototransformation of the substance in air are available. Based on estimation with the QSAR model AopWin (v1.92), in air the substance undergoes rapiddegradation after reaction with hydroxyl radicals. The DT50-value after reaction with hydroxyl radicals is 15.7 (using 12 hours).This indicates that the substance is not a long-range transported chemical in air according to the UNECE criteria (http://www.unece.org/fileadmin/DAM/env/documents/2000/ece/eb/ece%20eb%20air.60.e.pdf). These half-lives will not be used for the CSA because these are calculated and not experimental values.

Water:

The hydrolysis test for this substance is not needed because of its ready biodegradability. The ester functionality presents indications for hydrolysis. For conservative reasons a half-life of 1 year is selected.

Biotic degradation:

For Isobornyl propionate the ready biodegradability is derived from the close structural analogue Isobornyl acetate (CAS 125-12-2) in which biodegradation potential of the substance in water was determined in a screening study according to OECD TG 301F (Manometric Respirometry) and in compliance with GLP criteria. In this study 100 mg/L test substance was inoculated with activated sludge from a municipal wastewater treatment plant for 28 days under aerobic conditions. During the incubation period the biological oxygen demand (BOD) was measured and biodegradation expressed as percentage of the theoretical uptake (ThOD). After the 28-day incubation period 75% of the substance was biodegraded. The 10-day window criterion was met. Based on these findings, the test substance is classified as readily biodegradable.

Bioaccumulation:

For Isobornyl propionate a BCF for aquatic species is derived from the close structural analogue Verdox (Cas no. 20298-69-5) for which the BCF was 156 L/kg (5% lipid content) in an OECD TG 305 study.

The BCF for terrestrial organisms was calculated using QSARs of Jager (1998), incorporated in the EUSES model, and yielded a value of 1200 L/kg ww.

Transport and distribution:

The adsorption / desorption (Koc) information for Isobornyl propionate is derived from the close analogue Cyclaprop (68912-13-0). Its experimental Koc was 1300 (Log Koc 3.11) when tested in an OECD TG 121.

The Henry's law constant is calculated using the equation from EUSES. Using a molecular weight of 210.32 g/mol, the experimentally determined vapour pressure of 3.1 Pa (at 24 °C) and water solubility of 19.8 mg/L (at 24 °C) the Henry's law constant at environmental temperature (12 °C) is calculated to be 16.6 Pa·m³/mol.

Based on Level III environmental distribution modelling using EPISUITE (assuming equal and continuous releases to air, water and soil) using the CAS number 2756-56-1 and the measured physicochemical parameters (water solubility = 19.8 mg/L, vapour pressure = 0.2325 mm Hg and log Kow = 5.0) as input, it is estimated that the majority of the substance released to the environment will partition mainly into soil (72.8%) and water (19.4%), with minor amounts to air (6.95%) and sediment (0.861%).

The SimpleTreat model, which is incorporated in EUSES, simulates the distribution of the substance in a Sewage Treatment Plant (STP). Model calculations show that 75.2% of the substance will be degraded and that 10.3%, 10.3% and 4.13% will partition to water, sewage sludge and air, respectively.