Reaction mass of isopentyl salicylate and 2-methylbutyl salicylate

Bioaccumulation: aquatic / sediment

Description of key information

The bioaccumulation potential of isoamyl salicylate has been assessed using a read-across approach supported by the analogue substance for which a BCF value is available, cyclohexyl salicylate. In applying the read-across two important aspects have been considered: the similar potential for metabolism of the two substances and the slight difference in lipophilicity (as modelled by logKow). As suggested in ECHA guidance R.7.10.3.2, the BCF value for the analogue has been corrected by the same factor of difference as for Kow to give a reasonable realistic estimate for isoamyl salicylate of 1062 to 1593 L/kg.

Key value for chemical safety assessment

BCF (aquatic species):

1 593 L/kg ww

Additional information

Reliable measured aquatic bioaccumulation data is not available for isoamyl salicylate. 

According to REACH Annex IX, information on bioaccumulation in aquatic species, preferably fish, is required for substances manufactured or imported in quantities of 100 t/y or more unless the substance has a low potential for bioaccumulation (for instance a log Kow ≤ 3). However,REACH Annex XI encourages the use of alternative information before a new vertebrate test, including fish, is conducted.

Isoamyl salicylate has a measured log Kow of >3. A read-across approach has been used to assess the bioaccumulation potential of isoamyl salicylate since a valid BCF value of 600-900 L/kg is available for an analogue substance, cyclohexyl salicylate. This is an analogue approach for which the read-across hypothesis is that the target substance (isoamyl salicylate) and source substance (cyclohexyl salicylate) have similar aquatic bioaccumulation as a result of structural similarity, expected similar metabolic potential in fish and limited differences in lipophilicity (as modelled by log Kow).

The two substances are structurally closely. The target substance is a mixture of two isomers, which are expected to have similar aquatic bioaccumulation potential. The source substance is a mono-constituent. They do not contain any impurities that are expected to affect their bioaccumulation properties.

In applying the read-across two important aspects have been considered, i.e. the lipophilicity and the metabolic activity of both substances.

The BCF value of a substance is generally positively correlated with its lipophilicity (as modelled by log Kow). ECHA guidance R.7.10.3.2 advocates the application of a correction factor as long as the difference in log Kow is limited and gives the following example: “if the substance to be evaluated has one methyl group more than the compound for which a BCF value is available, the log Kow will be 0.5 higher and the estimated BCF from read-across is derived from the known BCF multiplied by a factor of 10^0.5. Isoamyl salicylate has a measured log Kow value of 4.95. Cyclohexyl salicylate has a log Kow value that is 0.25 log units slower. Therefore, an adjustment factor of 10^0.25(i.e. 1.77) has been applied to the cyclohexyl salicylate measured BCF value of 600-900 L/kg to give a reasonable realistic estimate for isoamyl salicylate of 1062 -1593 L/kg.

Based on the above information, it is concluded that there is no need for further investigation of aquatic bioaccumulation with fish. 

For classification purposes, an experimentally derived high quality log Kow value is suitable when a measured BCF on an aquatic organism is not available. Isoamyl salicylate has a measured log Kow of 4.95. This exceeds the CLP cut-off value of < 4.5. Isoamyl salicylate has an estimated BCF value of 1062 -1593 L/kg based on read-across from analogue data and corrected for slight differences in log Kow. This is close to the CLP threshold value of ≥ 2000 L/kg. Thus amyl salicylate is considered not to have the potential to bioconcentrate for classification purposes.

For the PBT and vPvB assessment a screening criterion has been established, which is log Kow greater than 4.5. Amyl salicylate has a measured log Kow of 4.95, which is just above this screening criterion. For organic substances with a log Kow below 4.5 it is assumed that the affinity for the lipids of an organism is insufficient to exceed the B criterion, i.e. a BCF value of 2000 L/kg. Since there is evidence that isoamyl salicylate is metabolised in fish, the aquatic BCF of amyl salicylate is expected to be upper than that predicted from log Kow. Indeed, the estimated BCF value for isoamyl Salicyate based on read-across from analogue data is in the range of 1062 -1593 L/kg.

This is well below the B definitive criterion of BCF > 2000 L/kg. Therefore isoamyl salicylate does not fulfil the B-criteria.

The estimated BCF value for isoamyl Salicyate based on read-across from analogue data is in the range of 1062 to 1593 L/kg. The highest value of 1593 L/kg has been chosen as a relevant and reliable conservative estimate for risk assessment purposes.