2,4,6-tri-tert-butylphenol

Endpoint summary

Additional information

Biodegradation in water: screening tests

Two studies are provided to address this endpoint, one experimental and one prediction. Both were awarded a reliability score of 2 in accordance with the criteria set forth by Klimisch et al. (1997). The experimental result has been selected as the key value.

 

In the key study the inherent biodegradability of the test material was investigated in a modified MITI (II) test conducted in accordance with the standardised guideline OECD 302C.

A mixed population of activated sewage sludge microorganisms was exposed to the test material for a period of 28 days at a concentration of 30 mg/L. The activated sewage was prepared by sampling 10 different sites around the UK in accordance with the guideline and the inoculum prepared for exposure by being fed daily with a 0.1 % synthetic sewage and maintained on a constant aeration at 25 ± 2 °C. The usage rate was equivalent to 100 mg dry weight/L.

Oxygen consumption was measured by direct manometer reading. Manometer volumes were recorded daily.

The test material attained 13 % degradation after 28 days, calculated from oxygen uptake (% of ThOD).

Under the conditions of this study the test material was determined not to be inherently biodegradable.

 

In the supporting study the ready biodegradability of the test material was estimated using the BIOWIN model v4.10 (EPI Suite v4.11).

BIOWIN, the model within EPISUITE which calculates biodegradation, estimates the probability of rapid aerobic and anaerobic biodegradation of an organic compound in the presence of mixed populations of environmental microorganisms.  BIOWIN contains seven separate models: Biowin1 (linear probability model); Biowin2 (nonlinear probability model); Biowin3 (expert survey ultimate biodegradation model); Biowin4 (expert survey primary biodegradation model); Biowin5 (MITI linear model); Biowin6 (MITI nonlinear model); and Biowin7 (anaerobic biodegradation model).

Sufficient information on the model training set is available to evaluate the applicability of the model to this substance. The molecular weight of the test material is within the training set range.

The test material was predicted to be not readily biodegradable.

 

Biodegradation in water and sediment: simulation tests and Biodegradation in soil

In accordance with Section 9.2 of Column 2 of REACH Annex IX, further biotic degradation testing shall be proposed by the registrant if the Chemical Safety Assessment indicates the need to investigate further the degradation of the substance and its degradation products.

Due to the properties of this substance, the environmental releases are strictly controlled and no emission to the environment takes place. The results of the chemical safety assessment therefore indicate that there is no need to further investigate biotic degradation.

It is therefore considered justified to omit the simulation testing on ultimate degradation in surface water, sediment simulation testing , identification of degradation products and the soil simulation testing studies required in sections 9.2.1.2, 9.2.1.4, 9.2.3 and 9.2.1.3 of Annex IX, respectively.