Calcium di(octanoate)

Biodegradation in water: screening tests

Description of key information

In water calcium dioctanoate is expected to dissociate to calcium ions and fatty acids. As an inorganic metal, the calcium ion will not undergo biodegradation, however, the fatty acid component may be biodegraded. Adipic acid is readily biodegradable based on publicly available data from five ready biodegradation tests. It is also inherently biodegradable. This supports the conclusions of a report that includes the dioctanoic acid (CoCAM 2014). The data for adipic acid is read across to calcium dioctanoate with the overall conclusion that calcium dioctanoate is readily biodegradable. 

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable

Additional information

In water calcium dioctanoate is expected to dissociate to calcium ions and fatty acids. As an inorganic metal, the calcium ion will not undergo biodegradation, however, the fatty acid component may be biodegraded. Adipic acid is readily biodegradable based on publicly available data from five ready biodegradation tests. It is also inherently biodegradable. This supports the conclusions of a report that includes dioctanoic acid (CoCAM 2014). The data for adipic acid is read across to calcium dioctanoate with the overall conclusion that calcium dioctanoate is readily biodegradable.

The source and target substances are structurally similar, with the source substance and fatty acid component of the target substance differing by chain length, with the source substance being C6 and the target substance being C8. As the source substance is C6 and therefore has a lower molecular weight compared to the target it may be more bioavailable and therefore demonstrate greater biodegradation potential. However, QSAR predictions for octanoic acid predict the fatty acid to readily biodegrade, and this is supported by the findings of the SIAP, which included octanoic acid (COCAM, 2014), therefore the target substance is considered to be equally likely to degrade in the environment.

The rate of degradation is expected to be dependent on the bioavailability of the substances to microorganisms which will be influenced by the water solubility and partition coefficient. The target and source substances are predicted to have similar solubilities and partition coefficients and therefore the bioavailability and rate of degradation are expected to be similar. This conclusion is supported by the available experimental data on the source substance and QSAR data for the target substance.

Adipic acid was found to be ready biodegradable in five ready biodegradation studies (Gerike and Fischer, 1978; Kim et al. 2001) and inherently biodegradable in a Zahn-Wellens test (Gerike and Fischer 1978). All the biodegradation studies conducted by Gerike and Fischer (1978) are based on standard methods but pre-date current OECD guideline methods. There is therefore no reporting of the criteria based on the 10 day window. There is also only limited reporting of the specific methods for these tests. The results for adipic acid in the ready biodegradation tests (based on OECD 301B, C, D and E) and in the Zahn-Wellens test (based on OECD 302B) all showed similar results to the OECD recommended reference substance Aniline with at least 83% biodegradation within 30 days (Gerike and Fischer 1978). In a Modified Sturm test following ASTM D5209 -91 adipic acid showed > 70% biodegradation in 10 days and >80% biodegradation in 30 days based on CO2 evolution (Kim et al. 2001). In this study adipic acid would fulfil the criteria for ready biodegradation within the 10 day window. Overall the consistent results for biodegradation in a number of different tests confirms that adipic acid is readily biodegradable.