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Environmental fate & pathways

Bioaccumulation: aquatic / sediment

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Description of key information

Key study: The estimated bioaccumulation factor for these two metabolites using the software BCFWIN v2.17 is as follows:
M1 = BCF = 3.162 (based on estimated log Kow 3.22)
M2 = BCF = 106.09 (based on estimated log Kow 3.54)

Key value for chemical safety assessment

Additional information

The results obtained in the study “Identification of Degradation Products in Test Samples of a Ready Biodegradability DOC Die Away Test” revealed the two major metabolites to be acids of the parent compound; 2-(2-bornyloxy)-propionic acid (M1) and 2-[2-(2-bornyloxy)-1/2-methyloxy]-propionic acid (M2).

These more exhaustive analyses show that the parent chemical was completely degraded during the OECD 301A guideline test. The slower rate of complete mineralization (i.e., to achieve the threshold for “Ready Biodegradable”) is explained by the fact that the test substance can be totally degraded without the loss of DOC in the biodegradability test, and it is only in subsequent steps in the metabolism that loss of DOC would be expected to be observed in the standard test that measures bulk DOC loss. The presence of two methoxypropionic acids and no other polar metabolites is consistent with the assessment that metabolism of the test substance to the corresponding acid is rapid, that metabolism of propionic metabolites is a slower process, and that metabolism of the isobornyl moiety is rapid. Since less than 20% of the DOC within the test substance is associated with the oxidation and hydrolysis of the propionic acids, the loss of over 50% of the DOC in the original test suggests that complete mineralization of the propionic acid metabolites was occurring after the rate-controlling step. This degradation pattern, with only non-bioaccumulative and non-toxic polar intermediates of these isobornyl ethers is similar to biodegradation of natural plant materials and humic acids, which are vital components of our natural waters.

The estimated bioaccumulation factor for these two metabolites using the software BCFWIN v2.17 is as follows:

M1 = BCF = 3.162 (based on estimated log Kow 3.22)

M2 = BCF = 106.09 (based on estimated log Kow 3.54)