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Environmental fate & pathways

Biodegradation in water: screening tests

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Description of key information

The test material is considered to be not readily biodegradable.

Key value for chemical safety assessment

Biodegradation in water:
under test conditions no biodegradation observed

Additional information

According to the Ecological and Toxicological Association of Dyes and Organic Pigments Manufacturers, with some exceptions, dyes are considered essentially non-biodegradable under aerobic conditions (ETAD 1995). Repeated evaluation of ready biodegradability using accepted screening tests have confirmed this assumption (Pagga and Brown 1986; ETAD 1992). Based on the chemical structure of the test material, there is no reason to suspect that biodegradation will be other than that described for dyes (ETAD 1995). As described below, available data support this assumption of the substance not being readily degradability.

This endpoint is addressed on a weight of evidence basis using four studies.

In the first, the potential of the test material to undergo biodegradation was estimated using a validated QSAR model. The study was awarded a reliability score of 2 in accordance with the criteria of Klimish et al. (1997).

BIOWIN estimates the probability of rapid aerobic and anaerobic biodegradation of an organic compound in the presence of mixed populations of environmental microorganisms. BIOWIN contains seven separate models. The test material fell within the training set of the model.

The BIOWIN model v.4.10 (EPISuite v.4.10) estimated that the test material is not readily biodegradable.

In the second, the potential of the test material to undergo biodegradation was investigated in a 28 day test. Only a summary is available and as such the data was awarded a reliability score of 4.

The parameter assessed in order to estimate the extent of the biodegradation was the dissolved oxygen, and BOD readings were taken after 5, 10, 15, 20 and 28 days.

Under the conditions of this study, the BOD did not meet the required dissolved oxygen depletion specified by the method and as such is considered not to be readily biodegradable.

In the third, the potential of the read across material EXP-Blue to undergo biodegradation was investigated in a 28 day test. The original report is in Japanese and a full translation was not available. Therefore the study was awarded a reliability score of 4.

The parameter measured was dissolved organic carbon. In the water and test material system, the residual DOC % was 105 and 101 %, and the percentage of test material that remained was 102 and 101 %. In the HPLC analysis, no peak attributable to degradants could be observed. It was therefore concluded that the test material did not change in the test material and water system and it remained stable.

In the sludge and test material system, the residual DOC % was 100 % in both replicates; however the test material residual percentage decreased to 92 %. Furthermore, two additional peaks were observed in the HPLC chromatogram. These two peaks were detected after the test material peak and were attributed to the degradants.

Under the conditions of this study, the test material is considered not to be readily biodegradable.

In the fourth, the potential of the read across material Sanolin Blue to undergo biodegradation was investigated in a study conducted with adapted sludge from a sewage treatment works. The study was awarded a reliability score of 2.

The inoculum was exposed to the test material over a period of 14 days at concentrations of 120 and 400 mg TOC/L and biodegradation assessed by the determination of total organic carbon.

Under the conditions of this study, the results are unclear but it is expected that the test material cannot be classed as readily biodegradable.

References:

1) ETAD (Ecological and Toxicological Association of Dyes and Organic Pigments Manufacturers). 1992. Draft Guidelines for the Assessment of Environmental Exposure to Dyestuffs.

2) ETAD (Ecological and Toxicological Association of Dyes and Organic Pigments Manufacturers). 1995. Health & Environmental Information on Dyes Used in Canada. An overview to assist in the implementation of the New Substances Notification Regulation under the Canadian Environmental Protection Act. Prepared by the ETAD Canadian Affiliates. July 1995. Report 7/21/95.

3) Pagga U and Brown D. 1986. The degradation of dyestuffs: Part II behaviour of dyestuffs in aerobic biodegradation tests. Chemosphere. 15(4): 478-491.