Reaction mass of 1-(2,6,6-trimethylcyclohex-2-en-1-yl)hepta-1,6-dien-3-one and 1-(2,6,6-trimethylcyclohex-1-en-1-yl)hepta-1,6-dien-3-one

Endpoint summary

Additional information

General discussion of environmental fate and pathways:

Abiotic degradation:

Air: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 2.2 hours and 0.61 hours respectively. This indicates that 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.

Water: The substance is expected to be hydrolytically stable because it does not contain hydrolysable groups such as ester, carbamates, epoxides, halomethanes, acylhalides (see Hydrowin, EpiSuite for all hydrolysable groups). The half-life at 25oC is > 1 year.

Biotic degradation:

In a biodegradation screening study (OECD TG 301F), after 28 days exposure of secondary activated sludge to 35 mg/L, 66% biodegradation was observed. In view of the substance being a multi-constituent and the 10 -day window does not need to be met, the substance is considered to be readily biodegradable.

Bioaccumulation:

Bioaccumulation on aquatic species is assessed using log Kow and calculated BCF values, which is sufficient for the risk assessment. The BCFs for aquatic and terrestrial organisms were calculated using QSARs of Veith et al. (1979) and Jager (1998), both incorporated in the EUSES model, and yielded values of 9440 and 3800 L/kg ww, respectively. Information is available that the substance has a kinetic BCF of 502 using in vitro fish hepatocytes.

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 is 4.33 (equivalent Koc = 21380 L/kg). Based on this value it may be concluded that the substance has a potential for adsorption to solid surfaces.

A Henry's law constant of 0.12 Pa·m³/mol (at 12 °C) was calculated in EUSES (Vap pressure 0.08 Pa, 232 molecular weight and 79 mg/l water solubility). Based on this value the substance will limitedly 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 79 -78 -7, the measured water solubility of 79 mg/l, the vapour pressure of 0.08 Pa (converted to 0.0006 mmHg) and log Kow of 5.5, the majority of the substance released to the environment will partition mainly into soil (86%) and water (11%) with small amounts to sediment (3%) and air (0.02%) .

The SimpleTreat model, which is incorporated in EUSES, simulates the distribution of the substance in a Sewage Treatment Plant (STP). Model calculations show that 38.7% of the substance will be degraded and that 54%, 7.2% and 0.02% will partition to sewage sludge, water and air, respectively.