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Environmental fate & pathways

Bioaccumulation: aquatic / sediment

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Description of key information

Accumulation in organisms is not to be expected. 

Key value for chemical safety assessment

Additional information

The bioaccumulation potential of Pigment Black 31 (CAS 67075-37-0) was assessed in a weight of evidence approach using logPow, Critical body burden and a measured BCF.

With a water solubility of < 0.002 mg/L and a solubility of 0.086 mg/I in n-octanol the log Pow can be estimated from the single solubilities as:

Pow= C(n-octanol) / C(water)= 86 µg/L / <2 µg/L = >43, thus log Pow= >1.63.

Since the water solubility of <2µg/L was estimated from the calibration solution with the lowest concentration therefore it can be suggested that the water solubility of 1 µg/L is possibly the lowest measurable concentration and is used as worst-case for the estimation of the log Pow value.

Pow= C(n-octanol) / C(water)= 86 µg/L / 1 µg/L = 860, thus log Pow= 1.93. Therefore, bioaccumulation in organisms is not be expected.

To assess the bioaccumulation potential of a substance with low solubility in octanol and water the critical body burden (CBB) can be calculated based on the solubility in octanol. According to “Guidance on Information Requirements and Chemical Safety Assessment Chapter R.11: PBT/vPvB assessment” v 3.0 in R. octanol is a reasonable surrogate for fish lipid, thus a low substance concentration in octanol may indicate reduced bioconcentration / bioaccumulation potential. It is proposed that where a substance shows no specific mode of action and has a

Coctanol[mg/L] < 0.002 [mMol/L] x Mol weight (g/Mol)

it can be assumed that the compound has only a limited potential to establish high body burdens and to bioaccumulate.

For Pigment Black 31 (CAS 67075-37-0) the CBB is estimated to be 1.196, based on Molecular mass of 598 g/Mol and Coctanol of 0.086 mg/L. Thus, the substance shows a Coctanol < CBB which indicates that the substance has only a limited potential to establish high body burdens and to bioaccumulate.

For Pigment Black 31 (CAS 67075-37-0) a guideline study according to OECD guideline 305 C is available. The bioconcentration test was conducted with the test substance in Cyprinus carpio over an uptake period of 56 days followed by a depuration period of 7 days. The fish were exposed in a flow-through system to the test concentrations of 0.1 and 1.0 mg/L, which is above the estimated water solubility of 0.002 mg/L. The stock solution of the test substance was prepared with a solubilizer in order to increase the water solubility of the test substance in the test media, resulting in a unrealistic bioavailability of the substance and as a consequence in a not reliable BCF-value. Because the used test concentrations are above the water solubility the result of the study, BCF of 15-55, is not reliable and can only be used as a hint in a weight of evidence approach combined with data on logPow and critical body burden.

In conclusion the substance has a low potential for bioaccumulation, thus accumulation in organisms is not to be expected.