Reaction mass of 3,5,6,6-tetramethyl-4-methyleneheptan-2-one and (E)-3,4,5,6,6-pentamethylhept-3-en-2-one

Endpoint summary

Description of key 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 the substance undergoes in air rapid degradation after reaction with hydroxyl radicals or ozone. The DT50-values after reaction with hydroxyl radicals and ozone are 6.81 hours and 22.92 hours, respectively. These values are not used in the risk characterisation because these are not experimental values.

The substance will not reach the stratosphere and is therefore not considered to be a long-range transported chemical in air. The substance 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: The substance is hydrolytically stable based on its structural properties.

 

Biotic degradation:

In a biodegradation screening study (OECD TG 301D), after 28 days exposure of secondary activated sludge to 2 mg/L of the substance, 0% biodegradation was observed. Prolongation of this study to 60 days resulted in 7% degradation. Based on these findings the substance is considered to be not readily biodegradable. In a follow-up study, the biodegradation of the substance was tested using an enhanced Closed Bottle Test (OECD TG 301D) in which the inoculum was acclimatised using a semi-continuous activated sludge (SCAS) unit (according to OECD TG 302A). In this study biodegradation did not exceed 20% after 42 days exposure to adapted activated sludge. These findings confirm the non-ready biodegradability of the substance.

 

Bioaccumulation:

Aquatic bioaccumulation: The bioconcentration of the substance in common carp (Cyprinus carpio) was determined in a GLP-compliant study according to the "Method for Testing the Degree of Accumulation of Chemical Substances in Fish Body" stipulated in the Japanese national guideline "Testing Methods for New Chemical Substances". In this study, the steady-state (lipid normalised) BCF value at a nominal test concentration of 0.04 mg/L was 335 in whole fish tissue.

Terrestrial bioaccumulation: The BCF for terrestrial organisms was calculated based on log Kow of 4.44, using the QSAR of Jager (1998) incorporated in the EUSES model, and yielded a value of 331 L/kg w.w.

Transport and distribution:

The adsorption potential of the substance was determined in a study according to OECD TG 121 (HPLC method). Under the conditions of the test, the log Koc of the substance was determined at 3.1 (equivalent Koc = 1,259 L/kg). Based on this value it may be concluded that the substance has moderate potential for adsorption to solid surfaces.

A Henry's law constant of 194 Pa·m³/mol (at 12 °C) was calculated in EUSES (Vapour pressure 39.8 Pa, 182 g/mol molecular weight and 37.4 mg/L water solubility (39.8 x 0.182/0.0374). Based on this value the substance will partition from water to air.

Based on Level III environmental distribution modelling using EPISUITE (assuming equal and continuous releases to air, water and soil) using the CAS number 81786 -75 -6 and the measured physico-chemical parameters as input (water solubility and log Kow), it is estimated that the majority of the substance released to the environment will partition mainly into soil (56%) and water (41.2%) with small amounts to air (2.13%) and sediment (0.63%).

The SimpleTreat model, which is incorporated in EUSES, simulates the distribution of the substance in a Sewage Treatment Plant (STP) based on vapour pressure, water solubility, log Koc and ready biodegradability. Model calculations show that 0% of the substance will be degraded and that 67.8%, 21.5% and 10.7% will partition to air, water and sewage sludge, respectively.