Amines, di-C16-18-alkyl

Endpoint summary

Additional information

Dialkyl amines 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 dialkylamines C16 -18, Kd values were observed ranging from: 2100 to 56000 L/kg for three different types of soil.

Biodegradation is considered to be the main removal mechanism of these substances. 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 dialkylamines in soil or sediment. For risk assessment purposes, these values are estimated based on the ready 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 worst-case values and are not considered to be a realistic reflection of reality.

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 ready biodegradability of dialkylamines.

(Eco)system	Method
Surface water (fresh)	TGD default value	15 days half-life
Surface water (fresh) sediment	TGD default value	30000 days half-life
Marine water	TGD default value	50 days half-life
Soils	TGD default value	30000 days half-life^a

^aHalf-life of the fraction dissolved in the water phase is expected to in the order of a few days.

 

Dialkylamines 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.

Dialkylamines do not contain hydrolysable covalent bonds. Cleavage of a carbon-nitrogen bond under environmental conditions is only possible with a carbonyl group adjacent to the nitrogen atom.

Direct photolysis of dialkylamines 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 dialkylamines was therefore assessed based on a calculated BCF. As indicated before dialkylamines are readily biodegradable and it is therefore unlikely that they will accumulate in the food chain. The log Kow value of 16.52 as calculated for dialkylamine C18 can be considered as a worst-case as low log Kow value. Based on this log Kow value a low bioaccumulation potential is predicted due to the limited bioavailability of the substance. This prediction is expressed in the calculated BCF (EPIsuite v4.0) of 3.162 L/kg.