Registration Dossier

Environmental fate & pathways

Endpoint summary

Administrative data

Description of key information

Additional information

Two biodegradation tests are available: a 28-day ready biodegradability study and a simulation study. The first study is considered to be the key study for the risk characterisation because in the simulation study a distinction between primary and ultimate degradation was difficult.

The first study was performed to assess the ready biodegradability of Salicynalva. The study was conducted in accordance with the OECD Guideline for Testing of Chemicals No. 301D "Ready Biodegradability: Closed Bottle Test". Sealed bottles containing the test substance (adsorbed onto glass filter paper) and inorganic nutrient medium were inoculated with activated sewage sludge bacteria and incubated for up to 28 days at 20 ± 1 °C. On Days 0, 4, 7, 11, 14, 18, 21, 25 and 28 duplicate bottles were taken and dissolved oxygen measurements were performed electrochemically. Percentage biodegradation values were determined by comparing the extent of oxygen depletion with the Theoretical Oxygen Demand (2.77 mg 02/mg). Additional bottles, containing both the test substance and a readily biodegradable standard substance were prepared in order to provide additional information on the inhibitory effect of the test substance. Salicynalva attained no biodegradation after 28 days and may not be termed as readily biodegradable. Salicynalva was not found to be inhibitory to activated sewage sludge bacteria under the conditions of this test.

In a second test the biodegradation and/or removal of Salicynalva within sewage treatment processes was investigated using the OECD Test Guideline 303A with appropriate modifications to ensure compliance with EPA "Public Draft" Guideline OPPTS 835.3220. The activated sludge is retained in a porous polythene cylinder into which the test substance is dosed together with a mixture of domestic and synthetic sewage.Treated effluent percolates through the porous liner (pore size 50-70 um) and overflows to a collection vessel. The use of a porous reactor wall eliminates the need for a sludge settlement chamber. The methods of analysis used to determine biodegradability and removal of the test substance were Dissolved Non-Purgeable Organic Carbon (DNPOC) analysis and specific test substance analysis using gas chromatography. The test substance attained a level of primary biodegradation/removal in this study of 88% and 89%, as shown by the parent compound analytical data. The level of ultimate biodegradation/removal achieved, provided by an assessment of the level of dissolved organic carbon removed, was 87%. Whilst this figure was shown to be statistically different to the levels of DOC removal observed in the control and reference substance pots, the statistical analyses also showed significant differences between duplicate control and reference substance pots.Therefore including the small data-set, undue emphasis should not be placed on the statistical results obtained. The overall difference, in terms of percentage carbon removal, between the test pots and the control and reference substance pots, during the definitive period, was only 3%. A final reasoning considering primary degradation and ultimate degradation is therefore not possible. In view of the similar removal between the reference substance, sodium benzoate, and the test substance it can be expected that a significant level of ultimate biodegradation/removal was obtained but no final conclusion on ultimate biodegradation can be made based on this study.

For the risk characterisation the results of the first test will be used because the non-ready biodegradability of Salicynalva is based on its mineralisation, while in the simulation test it is difficult to distinguish between primary degradation and ultimate degradation.