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Environmental fate & pathways

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The ultimate biodegradation is the complete conversion of an organic material to carbon dioxide, water, inorganic salts and normal cellular products of bacteria. The rate and extent of C02 production by bacterial action is dependent on many variables. However, the extent of C02 production in a given time under constant conditions can be used as a measure of ultimate biodegradability of a material. Several test procedures have been developed for this purpose. Readily degradable materials such as dextrose'and linear alkylbenzene sulfonate (LAS) typically yield 80-90% and 60-80% of theory, respectively, by these procedures. Since the bacterial systems used in these procedures are relatively weak, a material showing a high degree of conversion to C02 during the test interval is not likely to persist in the environment.

Two tests were performed in order to assess the ultimate biodegradation of Sulfatan R (DTDM):

  • Thompson-Duthie-Sturm Procedure
  • Monsanto Shake Flask Procedure

Ultimate biodegradation C02 evolution measurements on the sulfatan R showed a significant C02 evolutions (>25%) that corresponds to a biodegradation 76% after 49 days. For Sulfasan R an unusually long induction or acclimation period of 21 days was found before significant C02 evolution occurred.

As a consequence, Sulfatan R (DTDM) can be considered as inherently biodegradable and will not be persistent in the aquatic environment.

In accordance with Column 2 of the Annexe IX of Reach, the "biodegradation in sediments and soils: simulation test" does not need to be conducted if the substance is characterized by a low potential of adsorption. Since log Kow of DTDM is inferior to 3, no significant adsorption on sediment is expected. Therefore, the "biodegradation in sediments and soils: simulation test" does not need to be conducted.

With regards to the biodegradation in water, according to Column 2 of Annexe IX of Reach, further biotic degradation testing shall be proposed by the registrant if the chemical safety assessment indicates the need to investigate further the degradation of the substance and its degradation products. The choice of the appropriate test(s) depends on the results of the chemical safety assessment and may include simulation testing in appropriate media (e.g. water, sediment or soil). Ultimate biodegradation C02 evolution measurements on the sulfatan R showed a biodegradation 76% after 49 days. For Sulfasan R an unusually long induction or acclimation period of 21 days was found before significant C02 evolution occurred. As a consequence, Sulfatan R (DTDM) can be considered as inherently biodegradable and will not be persistent in the aquatic environment. For this reason, no simulation biodegradation test is proposed in water.