Registration Dossier

Environmental fate & pathways

Endpoint summary

Currently viewing:

Administrative data

Description of key information

Additional information

Abiotic degradation

Air: Based on estimation with the QSAR model Aopwin Cyclacet undergoes in air rapid degradation after reaction with hydroxyl radicals or ozone. The DT50 values after reaction with hydroxyl radicals and ozone are 1.907 hours and 1.375 hours, respectively. The half-life time of the substance is < 2 days. Cyclacet will not reach the stratosphere and is therefore not considered to be 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). Cyclacet 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, 1272/2008 and its amendments).

Water: Cyclacet is considered hydrolytically stable under environmental conditions, based on read-across to a study performed on the structurally related substance Cyclobutanate (which was experimentally tested in an OECD TG 111). The half-life time of Cyclacet at 25°C is >1 year at pH 4 and 7, whereas the half-life is expected to be 13 days at pH 9.

Biotic degradation

1) In a screening study according to OECD TG 301F, 10% biodegradation was found after 28 days. This means that Cyclacet is not readily biodegradable.

2) DT50 -water: For Cyclacet a half-life of 17 days at 12oC has been derived using read across and QSAR modelling.

Bioaccumulation

Aquatic organisms

1) The BCF of Cyclacet is 156 l/kg based on read across from Verdox which is tested in an OECD TG 305 test and has a BCF of 156 l/kg.

2) This BCF is supported with the calculated BCF of 412 l/kg in aquatic organism using the equation of Veith (1979) using a log Kow of 3.9. It can be concluded that the substance has no bioaccumulation potential (< 500 l/kg).

Terrestrial organisms

The BCF in earthworms was estimated to be 96.2 l/kg ww with the equation from Jager (1998), indicating that the potential for bioaccumulation in terrestrial organisms will also be limited.

Air-breathing organisms

Cyclacet does not bioaccumulate in air breathing organisms, despite fulfilling the first two criteria on log Kow (> 2) and log Koa (> 5) for a concern in air breathing mammals. The metabolisation of Cyclacet being an ester will be fast due to carboxyl esterases present in all (vertebrate) organisms. Using the QSAR model BCFBAF, it is estimated to be 0.34 days (DT50 < 1 day). The transformation product Cycla-alcohol as such has a log Kow around 2 (2.4 measured and 1.8 calculated). Cyclacet is a secondary alcohol and those will be conjugated in mammals e.g. with Glucuronic acid which has a low log Kow of << 2 (Glucuronic acid has a log Kow of -2.57 as presented in Pubmed). This has been derived from an EFSA publication on secondary alcohols using similar substances as Cyclacet. Based on this metabolic profile the DT50 is estimated to be < 1 day. Beside the short DT50, the kidney is the key excretion pathway because the alpha-hydrocarbon nephropathy present in the kidney after repeated exposure shows that urine is the key excretion route. The other metabolite is Acetic acid, which is a normal constituent of the body. In view of the metabolic profile of Cyclacet there is no concern for Cyclacet or its metabolites for biomagnification in air breathing organisms.

Transport and distribution

Koc: The determined Koc value of 417 (log Koc 2.62) (HPLC, OECD TG 121) indicates that the substance will have a low potential to adsorb to sediment/soil (< 500).

Henry's law constant: To assess the volatilisation potential of the substance a Henry's law constant was calculated which showed a value of 2.44 and 1.11 Pa.m3/mol at 25 and 12°C, respectively. This value is used in distribution modelling and shows that volatilisation only plays a minor role in the environmental behaviour of Cyclacet.

Based on Level III distribution modelling using EPISUITE (assuming equal and continuous releases to air, water and soil) using the CAS number 2500 -83 -6 (5 -yl isomer) and the measured physico-chemical parameters as input, it is estimated that the majority of the substance released to the environment will partition mainly into soil (79%) and water (21%) 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 based on vapour pressure, water solubility, log Kow and non-ready biodegradability. The model predicts that 93% of the substance will partition to water, 5% to sewage sludge and 2% to air at 12°C.