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Environmental fate & pathways

Biodegradation in soil

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Description of key information

No simulation tests for degradation rates under environmental conditions are available; therefore the default values suggested by the REACH guidance may be used.  For soil this would be a half life value of 300000 days. These environmental half-life's should be considered as extreme worst-case values and are not considered to be a representative reflection of reality. The hydrolysis rate is considered to be the rate determining step in the biodegradation of tall oil diethylenetriamine imidazoline. This hydrolysis will also occur when the substance is sorbed.  A half-life of 18 days is considered realistic for degradation in soil for the ester-quats which are hydrolysable brothers of the extremely strong sorbing DODMAC (HERA esterquats environmental risk assessment report). The half-life as considered realistic for water is therefore also considered to be representative for the half-life in sediment and soil. For precautionary reasons a safety factor of 2 is applied on the hydrolysis half-life of 28 days for the read-across. For soil and sediment a half-life of 56 days is used in risk assessment.

Key value for chemical safety assessment

Half-life in soil:
56 d
at the temperature of:
20 °C

Additional information

The Kpsoil for was determined to be 47249 L/kg. The suggested maximum half-life for an inherently degradable substance with a Kpsoil in the range >10000 L/kg is 300000 days for soil (at 12 ºC). These values are considered as extremely conservative but in the absence of measured data can be used in the exposure assessment as a worst-case. When however also the hydrolysis data are considered a much shorter half-life of the parent substance in soil is anticipated. The hydrolysis rate is considered to be the rate determining step in the biodegradation of tall oil diethylenetriamine imidazoline. A half-life of 18 days is considered realistic for degradation in soil for the ester-quats which are hydrolysable brothers of the extremely strong sorbing DODMAC (HERA esterquats environmental risk assessment report). The half-life as considered realistic for water is therefore also considered to be representative for the half-life in sediment and soil. For precautionary reasons a safety factor of 2 is applied on the hydrolysis half-life of 28 days for the read-across. For soil and sediment a half-life of 56 days is used in risk assessment.

 

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