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Environmental fate & pathways

Biodegradation in water and sediment: simulation tests

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Description of key information

The performance of a simulation test for ultimate degradation in surface water is scientifically not justified because the substance shows no hazard to humans or the environment and is inherently, ultimate biodegradable. 
A sediment simulation test for biodegradation is not justified due to the low potential to adsorb to the sediment and the resulting negligible exposure to the sediment.

Key value for chemical safety assessment

Additional information

The performance of a simulation test for ultimate degradation in surface water is scientifically not justified:

 

This test according to Section 9.2.1.2 of the REACh Regulation No 1907/2006 Annex IX is not required (as per Column 2),

  • if the substance is highly insoluble in water, or
  • if the substance is readily biodegradable.

While trimethylolpropane was shown not to not fulfil the criterion for high insolubility, 70% degradability within 7 days was shown in an inherent test which proves that the substance is ultimately degradable. Based on this result, EUSES 2.1.1 calculates a degradation fraction in the STP of 40.8% resulting in an emission to water of 59.2 % via STP. Therefore - based on the inherent results - it can be assumed, that trimethylolpropane will be further degraded after its release into surface water. Taking this into account and the fact, that the effect data on the substance neither indicate hazards to the environment nor to humans, a low risk to the aquatic environment and humans can be assumed. Therefore, further tests on the degradation in water are not needed.

 

The performance of a sediment simulation test for biodegradation is scientifically not justified:

 

In accordance with the REACh Regulation No 1907/2006 Annex IX, Section 9.2.1.4, sediment simulation testing for biodegradation tests are only required for substances with a high adsorption potential to sediment.

 

Since trimethyololpropane has a low distribution coefficient koc = 1.5, and therefore a low potential to adsorb on the sediment, exposure to sediment is unlikely and a sediment simulation test for biodegradation is not needed.

 

Furthermore, it should be considered that trimethylolpropane is not to be classified in any respect, and that for this reason, neither an environmental nor a human health risk assessment has to be performed. Consequently, results from a simulation study on degradation in water and in sediment would be without any purpose.