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Environmental fate & pathways

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Primary fatty amine ethoxylates 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 three different soils soil/water distribution coefficients (Kd values) were observed ranging from: 2025 to 4639 L/kg. Biodegradation is considered to be the main removal mechanism of these substances as they are readily biodegradable. Some ready biodegradability tests may however been hampered by the biocidal activity of these substances.

The half-life in the different environmental compartments will influenced by the bioavailability of the substances. No data is available for the determination of the primary fatty amine ethoxylates in soil or sediment. In absence of half-life data in these compartments these can as a worst-case be estimated based on the readily biodegradability and the sorption data as determined in a sorption desorption test.

As an alternative also read-across from a similar substance may be applied. For 14C hexadecylamine a half-life in three soils was measured according to an OECD 307 test. Although this C16 amine is strongly sorbing to soil (median Kp soil of 3875 L/kg at lowest measured concentration), half-life’s of 8.14 to 8.98 days were observed at 20 °C. These values can be recalculated (EUSES) to 12 °C a maximum half-life in soil of 16.9 days. As both primary alkyl amines and primary alkyl amine ethoxylates (2EO) are readily biodegradable and structurally strongly related, it is considered acceptable to use a half-life of 17 days in soil and sediment for the primary fatty amine ethoxylates risk assessment as well.

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 primary fatty amine ethoxylates.

 

(Eco) system

 

Method

Half-life

Surface water (fresh)

TGD default value

15 days half-life

Surface water (fresh) sediment

Measured; read-across

17 days half-life (aerobic)

Marine water

TGD default value

50 days half-life

Marine water sediment

Read-across

57 days half-life

Soils

Measured; read-across

17 days half-lifea

Degradation in sewage treatment plants

Determined in simulation test (OECD 303A)

>99.999% total removal of parent 

99.83% removal by biodegradation

0.16% removal via sorption

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

 

Primary fatty amine ethoxylates 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.

Primary fatty amine ethoxylates 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. Degradation of primary fatty amine ethoxylates through hydrolysis is therefore not considered.

Direct photolysis of primary fatty amine ethoxylates in air/water/soil will not occur, because it does not absorb UV radiation above 290 nm. Photo transformation in air/water/soil is therefore assumed to be negligible.

No measured BCF fish is available for the primary fatty amine ethoxylates.

Standard OECD 305 tests are technically not feasible with these strongly sorbing easily 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 biodegraded. The bioaccumulation potential of primary fatty amine ethoxylates was therefore assessed based on a log Kow calculated from the measured log Kow of the constituents, resulting in a log Kow=1.5 for 2,2'-(C12 -14 (evennumbered) alkyl imino) diethanol.

As indicated before, primary fatty amine ethoxylates are readily biodegradable and it is therefore unlikely that they will accumulate in the food chain. Since there is a valid log Kow value available this value is used to assess the bioaccumulation potential.

Three valid measured log Kow values are however available as presented in the table below.

 

primary fatty amines ethoxylates

CAS number

Measured log Kow 

2,2'-(C12-18 evennumbered alkyl imino) diethanol

71786-60-2

0.7

2,2'-(C16-18 (evennumbered) alkyl imino) diethanol

1218787-30-4

3.6

2,2’(octadec-9-enylimino) -bisethanol

25307-17-9

3.4

 

The highest log Kow is observed for 2,2'-(C16-18 (evennumbered) alkyl imino) diethanol (CAS no 1218787-30-4). For this product also the lowest CMC of 3.5 mg/L was observed. The measured log Kow value of 3.6 indicates a moderate bioaccumulation potential for narcotic substances. For polar narcotics like the primary fatty amine ethoxylates however there is only limited information on the relationship between log Kow and BCF.

For hexadecyl amine rapid metabilisation in fish is anticipated based on in vitro metabolism test results with this substance (Kmet= 0.152 1/d; Bernard et al., 2006). Based on the structural similarity and ready biodegradability of the primary fatty amine ethoxylates similar metabolisation rates are expected for the primary fatty amine ethoxylates. According to the REACH PBT guidance R.11, evidence of high biotransformation/metabolisation rate in fish may be used to support for arguing for a limited bioaccumulation potential but quantitative thresholds have not been established. The use of QSAR- and mechanistically-based bioaccumulation models is also considered valuable in the overall bioaccumulation assessment process. The BCFBAF model (v3.01) as included in EPIsuite (v4.1) allows the inclusion of metabolism into the BCF calculation but the results of this model should be considered with care as the training set holds only a limited number of substances which can reliably be used to predict the fate of cationic surfactants. With a log Kow of 1.5 the BCFBAF model predicts a BCF of 4.54 L/kg wwt without metabolism and 1.59 L/kg wwt with metabolism.

The weight evidence of each of the fate points (log Kow, metabolism, biodegradability, bioavailability, BCF model) of a substance seperately is limited but when considered together it is justified to concluded that primary alkyl amine ethoxylates (2EO) will not accumulate in the food chain and have a low bioaccumulation potential.