Registration Dossier

Environmental fate & pathways

Endpoint summary

Administrative data

Description of key information

Additional information

STABILITY

Phototransformation in air

Half-life for reaction with photochemically-produced hydroxyl radicals estimated to be between 4.2 and 12.5 hours.

Overall OH Radicals Rate Constant = 2.65E-06 cm3/(molecule-day).

Hydrolysis

Study technically not feasible. The substance is highly insoluble in water.

BIODEGRADATION

In reported tests of ready biodegradability in water, trioctyl benzene-1,2,4-tricarboxylate was found to have low biodegradability. However, tests with a structural analogue of the substance, a trimellitate ester with mixed C8 -C10 side chains, showed significant biodegradation and, while not readily biodegradable, this analogue can be considered to be inherently biodegradable. The differences observed in tests on the two substances may be a result of methodology, particularly important when testing “difficult” substances – in this case, substances with low water solubility. Modelling of possible biodegradation pathways indicate that aerobic degradation is likely, the first steps in this being hydrolysis to trimellitic acid and the corresponding alcohol, both of which have been shown to be readily biodegradable.

 

There are no data for sediment or soil biodegradation studies relating to the substance. Such studies are not needed due to the fact that, while microbial pathways exist for the degradation of the substance, the degradation of substance will be limited due to limited bioavailability.

 

BIOACCUMULATION

EPA BCFBAF model

The BCF of the substance was estimated to be: 251 L/kg ww

The BAF of the substance was estimated to be: 1.14 L/kg ww.

EPA T.E.S.T. model

The BCF of the substance was estimated to be: 6.03

The highest value of BCF was selected for the chemical safety assessment.

It is therefore concluded that the potential for bioaccumulation of trioctyl benzene-1,2,4-tricarboxylate (DIPLAST TM 8) is very low.

 

TRANSPORT AND DISTRIBUTION 

Adsorption / desorption

The Soil Adsorption Coefficient (Koc) of the test material, estimated using the softwareKOCWINv2.00, leads to the following results:

Log Koc= 7.93(from MCI)

Log Koc= 5.94 (from Log Kow)

Overall, the MCI methodology is somewhat more accurate than the Log Kow methodology, although both methods yield good results, then the Koc estimate value from MCI was selected for the environmental assessment.

According to the McCall classification scheme, this means that the above substance is immobile (Koc > 5000) on soil.

 

Henry's Law constant

The Henry's Law Constant (HLC) of the test material, calculated using the software HENRYWIN v3.20, leads to the following estimated results:

 

HLC= 0.056 Pa-m3/mole(bond contribution, reliability= 3)

HLC= 0.026 Pa-m3/mole(group contribution, reliability= 2)

 

The last one value, being most reliable, was selected for further assessments and indicates thatthe substance is essentially non volatile from surface water.

Distribution modelling

Distribution in environmental compartments has been calculated using a Fugacity model, under the emission scenario of 1000 kg/h into each of air, water and soil compartments, according to Mackay, Level III. Distribution in various environmental compartments is estimated as: Air= 0.62%; Water= 7.76%; Soil= 38.5% and Sediment= 53.1%.

Sediment and soil were then found to be the major target compartments.