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Environmental fate & pathways

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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

Significant (65%) degradation was observed in a Closed Bottle test utilising a test concentration of 2 mg/L. A modified MITI test using a high test concentration of 100 mg/L resulted in low biodegradability.

The higher degree of biodegradation observed in tests with a lower initial test substance concentration indicates limited bioavailability. It is possible that the rate of biodegradation may be limited by the rate of hydrolysis of the test substance and/or the rate with which the substance dissolves. Modelling of possible biodegradation pathways indicate that aerobic degradation is likely, the first steps in this being hydrolysis to trimellitic acid and octanol, 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 the substance can be regarded as being readily biodegradable.

 

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 software KOCWINv2.00, 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= 0.43%; Water= 7.75%; Soil= 38.8% and Sediment= 53%.

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

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