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Environmental fate & pathways

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N-[2-(piperazin-1-yl)ethyl]C18-unsaturated-alkylamide is quickly degraded in a ready biodegradability test and N-(2-aminoethyl)piperazine (CAS no 140 -31 -8) is formed as metabolite (Ginkel 1990, Geerts 2014). The available biodegradability data show that N-[2-(piperazin-1-yl)ethyl]C18-unsaturated-alkylamide is not persistent but only it degradation product N-(2 -aminoethyl)piperazine is considered to be persistent (Dow, 2010)

 

In an STP simulation study >99.99% removal of N-[2-(piperazin-1-yl)ethyl]C18-unsaturated-alkylamide was observed from which 0.042% via adsorption to sludge using specific chemical analyses based on high recoveries of spiked sludge and effluent samples (Ginkel, 2010).

In this STP simulation study also a high DOC removal of 89 +/-1% (95% confidence interval) was observed indicating that also N-(2 -aminoethyl)piperazine is removed. Considering the low Henry's law constant of 9.3 * 10^-9 Atm/m3/mol. and high Koc of 37000 L/kg of N-(2-aminoethyl)piperazine most of this substance must have been removed via sorption.

 

Based on the uses claimed for N-[2-(piperazin-1-yl)ethyl]C18-insaturated-alkylamide soil exposure is likely. Based on the biodegradability data from N-(2 -aminoethyl)piperazine it is however unlikely that significant further degradation of N-(2-aminoethyl)piperazine will occur in soil. Further testing in soil is therefore not expected to deliver more information. For soil therefore a worst-case half-life value of 3000 days (Kd = 2000 L/kg) is used. In accordance with column 2 of REACH annex IX, further degradation testing does not need to be conducted as the chemical safety assessment does not indicate a need for further investigation.

 

The primary hydrolysis tests indicates that the substance is hydrolyzed less than 10% within 5 days at 50°C in the pH buffers 4 and 7 but at pH9, about 23% and 13% hydrolysis was observed for the components C18:1 and C18:2, respectively. In the advanced test at pH9 at temperatures of 20, 50 and 70°C, half-lives for the C18:1 were observed of 6211, 549 and 1149 hours, respectively. For the component C18:2, half-lives were observed of 9316, 589 and 2455 hours at 20, 50 and 70°C, respectively.

Using the Arrhenius relationship, a half-life at 25°C was calculated for the two components of 3616 hours (151 days) for C18:1 component and a half-life of 4893 hours (204 days) for C18:2 component. No degradation metabolites could be identified.

 

To address the bioaccumulation potential according to REACH requirements, the log Kow of N-[2-(piperazin-1-yl) ethyl] C18-insaturated-alkylamide was measured applying slow stirring method according to OECD 123. The observed log Kow value (Log Kow>3) indicates that the substance may have a bioaccumulation potential if N-[2-(piperazin-1-yl) ethyl]C18-insaturated-alkylamide would have been a narcotic substance. For polar narcotics like the N-[2-(piperazin-1-yl) ethyl]C18-insaturated-alkylamide however there is only limited information on the relationship between log Kow and BCF.

Based on the non-persistency of the parent product: N-[2-(piperazin-1-yl) ethyl]C18-insaturated-alkylamide and the negligible emission to surface water, accumulation in the food chain is considered to be unlikely and further bioaccumulation testing of N-[2-(piperazin-1-yl) ethyl]C18-insaturated-alkylamide (CAS no 1228186-18-2) can be waived according to column 2 of REACH Annex IX.

 

The metabolite formed; N-(2-aminoethyl)piperazine (CAS no 140 -31 -8) is however considered to be persistent. N-(2 -aminoethyl)piperazine has however a very low measured log Kow of -1.48 (SDS, -1.57 calculated value KOWWIN v1.68) and is based on its structure not expected to have a significant bioaccumulation potential. Bioaccumulation data on the structural analogue piperazine (CAS 110-85-0) support this conclusion: The BCF of piperazine was determined in the carp (Cyprinus carpio), where the measured BCF was < 3.9 L/kg at 0.1 mg/L exposure (CERI, 2004).

 

N-[2-(piperazin-1-yl) ethyl]C18-insaturated-alkylamide sorbs strongly to soils. Equilibrium adsorption coefficients (Kd) were found to be in the range of 2300 to 4600 (cm3/g) for the C18:1 component, 1600 to 3300 for the C18:2 component and 1000 to 1900 for the C18:3 component in the different soils tested. N-[2-(piperazin-1-yl) ethyl] C18-insaturated-alkylamide is based on these sorption results considered to be immobile in soil and will not leach to ground water.

For risk assessment the average Kd of 2000 L/kg will be used and not the organic matter normalized value (Koc) because the relation between the organic matter concentration and the sorption observed alone is not sufficient (Droge & Goss, 2013).

Despite of its low log Kow and high water solubility, N-(2-aminoethyl)piperazine is not considered to be mobile based on it high Koc of 37000 L/kg. N-(2-aminoethyl)piperazine has dissociation constants (pKa) of 9.6, 8.5 and 4.3 (Disseminated dossier) and is fully protonated at neutral pH. Sorption is expected to occur only based on a cation exchange mechanism and is not highly correlated with the organic carbon content in sorbents with a significant content of Cation Exchange sites not originating from organic carbon.

 

Because there is no principal difference between soil and sediments considering the sorption properties (EU-RAR Primary alkyl amines, 2008) and because the degree of sorption is not related to the organic carbon content for cationic surfactants, the value for soil will also be used for sediment and suspended particles. Because suspended matter consists of smaller particles the Kd for suspended matter is as a worst-case doubled.

For sludge which consists mainly of organic matter the sorption data as observed for soil is not considered to be representative. The removal in an STP via sorption to sludge has been quantified in the STP simulation test (OECD 303A).

In the table below the distribution constants used in this assessment are summarized:  

Distribution constants 

Kpsoil

2000 L.kg-1

Ksoil-water

3000 m3.m-3

Kpsusp

4000 L.kg-1

Ksusp-water

1000 m3.m-3

Kpsed

2000 L.kg-1

Ksed-water

1000 m3.m-3