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Sediment toxicity

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Description of key information

Bacterial lipases in the sewage treatment plant and in the environment are expected to hydrolyze TS-ED 532 to a very large extend into acetic acid, glycerol and 12-acetoxy- and/or 12-hydroxystearic acid. These degradation products are all readily biodegradable. Neither acetic acid nor glycerol (both have a logKow <0) will partition to sediment in any significant degree. 12-acetoxy- and/or 12-hydroxystearic acid have a calculated logKow (EpiSuite) of 6.41 respectively 7.41 (EpiSuite). These degradation products have very similar fate properties to the mother chemical. 
In the sewage treatment plant (STP), TS-ED 532 and the degradation products (12-acetoxy- and/or 12-hydroxystearic acid) will behave in a very similar manner to oil also entering the STP. Measurements have shown a removal of the oil of >99% (“Miljøfremmede stoffer i spildevand og slam”. Miljøprojekt nr. 325, 1996. Danish EPA). The same removal is assumed for TS-ED 532 and the degradation products (12-acetoxy- and/or 12-hydroxystearic acid).  
The concentration in the inlet to the STPs during the formulation/end-use and service life stages is not expected to exceed the water solubility of TS-ED 532 (and its degradation products). As the removal in the STP is assessed to >99%, the RCR for sediment is calculated at 0.4, which is below 1 for the formulation, end-use and service-life cycle phases.
Overall, it is concluded that there is no need to investigate further the effects of TS-ED 532 and/or relevant degradation products on sediment organisms.

Key value for chemical safety assessment

Additional information

Bacterial lipases in the sewage treatment plant and in the environment are expected to hydrolyze TS-ED 532 to a very large extend into acetic acid, glycerol and 12-acetoxy- and/or 12-hydroxystearic acid. These degradation products are all readily biodegradable. Neither acetic acid nor glycerol (both have a logKow <0) will partition to sediment to any significant degree. 12-acetoxy- and/or 12-hydroxystearic acid have a calculated logKow(EpiSuite) of 6.41 respectively 7.41 (EpiSuite). These degradation products have

fate properties

very similar to TS-ED 532.

 

In the sewage treatment plant (STP), TS-ED 532 and the degradation products (12-acetoxy- and/or 12-hydroxystearic acid) will behave in a very similar manner to oil also entering the STP. Measurements have shown a removal of the oil of >99% (“Miljøfremmede stoffer i spildevand og slam”. Miljøprojekt nr. 325, 1996. Danish EPA). The same removal is assumed for TS-ED 532 and the degradation products (12-acetoxy- and/or 12-hydroxystearic acid).  

 

The release factor from manufacture of the substance to waste water is assessed to be 0.00008. Only emission during repair and maintenance may place. The emission to air is assessed to be very low due to the low vapour pressure of the substance. With a tonnage of 6000 tonnes/yr and number of emission days set to 300 days/yr, assigning 10% of the whole tonnage to the region, assuming a maximum release to waste water during all life cycle stages of 10%, a RCR in sediment is calculated at 1.6, which is very close to 1. An extra safety factor of 10 was applied for the derivation of the RCR, as the TS-ED 532 and the degradation products (12-acetoxy- and/or 12-hydroxystearic acid) are very hydrophobic so uptake via ingestion of sediment can be important. The approach of using an extra factor of 10 is considered only as a screen for assessing the level of risk to sediment dwelling organisms, and as the RCR is very close to 1, it is assessed that there is no risk to the sediment dwelling organism from the manufacture.   

 

The concentration in the inlet to the STPs during the formulation/end-use and service life stages is not expected to exceed the water solubility of TS-ED 532 (and its degradation products). As the removal in the STP is assessed to >99%, the RCR for sediment is calculated at 0.4, which is below 1 for the formulation, end-use and service-life cycle phases.

 

Overall, it is concluded that there is no need to investigate further the effects of TS-ED 532 and/or relevant degradation products on sediment organisms.

 

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