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Alkyl polyethylene amine imidazolines are for the main fraction protonated under ambient conditions. This means that they will sorb strongly to negatively charged surfaces like glassware, soil and sediment constituents. For DETA based Imidazoline, Kd values were observed ranging from: 19022 to 145295 L/kg for three different types of soil

Hydrolysis in combination with biodegradation is considered to be the main removal mechanism of these substances. A realistic worst-case half-life of 28 days at 20°C for the rate determining hydrolysis step is derived from read-across from a TEPA based hydrolysis test. Biodegradation testing showed that the DETA based amidoamine/imidazolines is completely metabolized to CO2, H2O and NO3.

The half-life in the different environmental compartments may be influenced by the bioavailability of the substances. No data is available for the determination of the half-life of alkyl amidoamines/imidazolines in soil or sediment. For risk assessment purposes, these values are estimated based on the inherent biodegradability of the available fraction and the sorption data as determined in a sorption desorption test. These environmental half-life's should be considered as extreme worst-case values and are not considered to be a representative reflection of reality. As indicated the hydrolysis rate is considered to be the rate determining step in the biodegradation of tall oil diethylenetriamine imidazoline. The 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 for the read-across. For soil and sediment a half-life of 56 days is used in risk assessment.

 

Table Summary of degradation rate constants in various (eco)systems based the inherent biodegradability of alkyl amidoamines/imidazolines.

(Eco)system

Method

half-life

Surface water (fresh)

Based on hydrolysis half-life

28 days

Surface water (fresh) sediment

Based on half-lfie surface with safety factor of 2

56 days

Marine water

Based on half-lfie surface with safety factor of 2

56 days

Marine water sediment

Based on half-lfie surface with safety factor of 2

56 days

Soils

Based on half-lfie surface with safety factor of 2

56 days

 

Alkyl amidoamines/imidazolines have a short predicted half-life in air but because there are no important releases into the atmosphere and volatilisation is expected to be negligible, this removal mechanism is thought to be of low relevance.

Alkyl amidoamines/imidazolines contain hydrolysable covalent bonds and the rate of hydrolysis was measured for a TEPA based imidazoline. Cleavage of a carbon-nitrogen bond under environmental conditions is only possible with a carbonyl group adjacent to the nitrogen atom.

Direct photolysis of Alkyl amidoamines/imidazolines in air/water/soil will most likely not occur, because it does not absorb UV radiation above 290 nm. Photo transformation in air/water/soil is therefore assumed to be negligible. Daylight might however influence the rate of hydrolysis.

Standard OECD 305 tests are technically not feasible with these strongly sorbing degradable substances. In addition is the route of exposure in a standard OECD 305 test unrealistic for these substances because the substance will either be sorbed or degraded. The bioaccumulation potential of amidoamines/imidazolines was therefore assessed based on a measured log Kow. As indicated before, imidazolines are quickly hydrolyzed and consequently biodegraded and it is therefore unlikely that they will accumulate in the food chain. The log Kow value as observed for the DETA based imidazoline can be considered as a worst-case as low log Kow values are expected for a higher number of amines in the structure. Based on this log Kow value of 2.2, the calculated log BCF is 1.24 (BCF = 17.4; EpiSuite v4.0).