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Environmental fate & pathways

Endpoint summary

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Bioaccumulation potential has been evaluated in fish according to OECD test methods. A measured BCF of up to 2.7 suggests the potential for bioconcentration in aquatic organisms is low. However, there are some uncertainties in the experimental data mainly due to testing at concentrations above the water solubility of the substance by the use of solubilising agents which are recognised as having the potential to lead to an underestimation of the BCF. Q(S)AR modelling estimates a BCF of 1090.

Information for the potential of a substance to bioaccumulate within aquatic organisms may be obtained from toxicokinetic studies with mammals, the available information on TOTM indicating that the parent substance is poorly absorbed. Q(S)AR modelling suggests that dermal absorption is expected to be negligible (see Section 7.1.2). Studies in the rat (see Section7.1.1) indicate that, following oral administration, the substance is partially hydrolysed in the gastro-intestinal tract to 2-ethylhexanol and the corresponding di-ester and, following further hydrolysis, the mono-ester. Only 2-ethylhexanol and a single isomer of mono-(2 -ethylhexyl)trimellitate appear to be absorbed with 75% of the administered dose eliminated unchanged in the faeces. Once absorbed, elimination is relatively rapid with <0.6% of the administered dose remaining in the carcass after 6 days.

Mammalian oral toxicokinetics show hydrolysis to the di-ester and mono-ester with release of 2-ethylhexanol. Modelling to predict likely biodegradation/environmental metabolites indicates the same with complete ester hydrolysis to trimellitic acid and 2 -ethylhexanol, both of which are readily biodegradable (See Section 5.2.1 – Biodegradation in water:screening tests – Pathway modelling).

 

Q(S)AR estimates of the bioconcentration factor using Epi Suite indicate, for the substance itself:

19 L/kg wet wt at default logPow 11.59 and water solubility 4.5E-5μg/Land 1090 L/kg wet wt at defined logPow 8.00 and water solubility 3μg/L, the estimated value being influenced by partition coefficient rather than water solubility.

Extending this to the predicted metabolites indicates:

Di-ester (CAS 58978-43-1) - 56.2 L/kg wet wt at default logPow 7.93 and water solubility 0.31μg/L

Mono-ester (CAS 68735-92-2) - 3.2 L/kg wet wt at default logPow 4.61 and water solubility 1043μg/L

Trimellitic acid (CAS 528-44-9) - 3.2 L/kg wet wt at default logPow 0.95 and water solubility 5963 mg/L

2-ethylhexanol (CAS 104-76-7) - 29.5 L/kg wet wt at default logPow 2.73 and water solubility 1379 mg/L

 

These considerations suggest that the potential for bioaccumulation is low.