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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 both DETA and PEPA based Imidazoline, Kd values were observed ranging from: 19022 to 165846 L/kg for three different types of soil

Hydrolysis in combination with biodegradation is considered to be the main removal mechanism of these substances. The hydrolysis test results of the TEPA based imidazoline (CAS no1226892-45-0) showed that the half-life of the first hydrolysis step (hydrolysis of the first imidazoline) was 371, 16.3 and 19.5 hours at 20℃ at respectively pH 4, 7 and 9. The half-lifes for the second step (hydrolysis of the amide) was 3744, 158 and 141 hours at 20 °C at respectively pH 4, 7 and 9. The half-lifes for the third step (hydrolysis of the second imidazoline) was 1896, 672 and 1.8 * 10^5 hours at 20 °C at respectively pH 4, 7 and 9. Under environmental conditions the detachtment of the alkylchain and hydrolysis of the imidazoline is considered to reduce the activity of the parent substance. A half-life of 672 hours is therefore considered to be representative for the hydrolysis of TEPA based imidazoline. A similar half-life in water is considered to be applicable for the hydrolysis of the other imidazolines in the category.

This indicates that imidazolines are quickly hydrolyzed to the amidoamine which is then biodegraded. The DETA based amidoamine/imidazolines is completely metabolized to CO2, H2O and NO3, for the amidoamine/imidazolines based on longer ethyleneamines no degradation of the polyethyleneamines has been observed so these are degraded to CO2, H2O and the polyethyleneamine which is used as starting material in the production.

The half-life based on biodegradation in the different environmental compartments may be influenced by the bioavailability of the substances. But hydrolysis will not be limited by the bioavailability of the substance. The half-life of the parent substance will be short due to the fast hydrolysis in dependent of the compartment as long as water is available. The half-life of the product of the hydrolysis reaction i.e the amidoamine, can probably best be evaluated based on its biodegradation half-life. Based on the biodegradation curves obtained for the DETA and PEPA based imidazoline, half-life’s of <30 days (at 20°C) are observed if the remaining polyethylene amine is excluded from the equiation. Therefore the half-life of 672 hours (or 28 days) is used for risk assessment purposes. For read-across to other compartments than water a safety factor of 2 is applied for precautionary reasons.

The Table below summarizes half-lives derived through default values and a simulation study.

 

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 data

28 days

Surface water (fresh) sediment

Based on hydrolysis data and an assessment factor of 2

56 days

Marine water

Based on hydrolysis data

28 days

Soils

Based on hydrolysis data and an assessment 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 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 lower log Kow values are calculated for substances with 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).