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PBT assessment

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PBT assessment: overall result

Reference
Name:
1,2-Benzenedicarboxylic acid, 3,4,5,6- tetrabromo-, mixed esters with diethylene glycol and propylene glycol
Type of composition:
legal entity composition of the substance
State / form:
liquid
Reference substance:
Composition 1
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Composition 1
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Composition 1
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Composition 1
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Composition 1
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Composition 1
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Composition 1
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Composition 1
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Composition 1
PBT status:
the substance is not PBT / vPvB
Justification:

Persistence:

as the substance is an UVCB with higher molecular weight components performing meaningful biodegradation tests is difficult. Therefore modelling approaches were chosen. EPWIN results were only obtained for the one ring component. Biowin1, Biowin2, Biowin 3 and Biowin 6 predict slow biodegradability with half-lives of moths, while Biowin 4 predicts primary biodegradation in weeks, which would be cosnistent with an ester bond cleavage and further rapid metabolism of the non-armatic parts of the molecule. Biowin 5 (MITI) predicts fast biodegradation and also the anaerobic model prediction is fast. This could relate to debromination and further degradation of the aromatic acid.

Hydrolysis predictions by Hydrowin give total half lives for both ester groups of 1,363 days at pH 8 and 13.7 days at pH 7. In principle ester groups of the higher molecular weight components should eqaully be hydrolysable, but the velocity will depend on the solubility and is hard to predict. The photodegradation half-life in air is predicted to be 4.2 hours (OH rate constant 3.5 E-12 cm3/molecule-sec, 12 h day, 1.5E6 OH/cm3), but volatilisation is highly unlikely given the high viscosity, and neglible vapour proessure of the substance.

In conclusion, while the substance is not likely to be readily biodegradable it is equally unlikely to be recalcitrant and will undergo degradation in the environment. However the velocity is hard to predict.

Bioaccumualtion:

Bioaccumulation of the higher moelcular weight components > 1000 is unlikely as absorption is very unlikely. The lower molecuar weight, one ring components have log Kow values between 3.8 and 4.1 and could be taken up. BCF predictions are all below the threshold of 2000 and range between 6 and 700 L/kg wet weight.

Bioaccumulation in terrestrial organisms could be of concern as the Koa is as calculated very high 17.8 (Koawin). However as the molecule as metabolisable groups, and will be rapidly metabolised to polar metabolites, it is unlikely that bioaccumualtion in terrestrial food chains occurs. Only the lower molecualr weight parts of the UVCB substance are likely to be absorbed in particular when dosed via the oral route. The lower molecula weight one ring components with predicted log Kow values between 3.8 and 4.1 can be absorbed and distributed. They are likely to undergo ester hydrolysis in the liver and potetially blood and other organs as esterases are occuring in many tissues. Primary metabolites after ester bond cleavage are propyleneglycol, diethyleneglycol and 1,2-Benzene dicarboxylic acid, 3,4,5,6-tetrabromo. Propyleneglycol and diethyeleneglycol  are likely further metabolised and rapidly excreted. The acid may undergo glucuronidation or sulfatation to more hydrophilic components that are likely to be excreted via the urine or the gut. Oxidative metabolism in the form of oxidative decarboxylation could also occur, but is less likely. In conclusion it is anticipated that the lowe molecular weight fractions of the UVCB can be taken up to a certain extend in particular via the GI-tract and are likely rapidly metabolised. The metabolites are expected to be rapidly excreted.

Therefore it can be concluded that based on the available data the substance is unlikely to be bioaccumulative or very bioaccumulative and will also not lead to accumaltive metabolites.

Toxicity: Based on the avaialable data the substance is not considered T.