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The test results obtained with Tetramine di-C16 -18 do not allow classification as readily biodegradable (AkzoNobel, 2015). Biodegradation in excess of 60% could also not be shown in a prolonged Closed Bottle (enhanced testing). The lack of biodegradation in the Closed Bottle test does not mean that Tetramine di-C16 -18 is persistent in nature because the test procedures could account for the recalcitrance in the Closed Bottle test. The inability to demonstrate rapid biodegradation in the Closed Bottle test is most likely caused by the toxicity of Tetramine di-C16 -18 in the mg/L range and its low bioavailability.

Tetramine di-C16 -18 is toxic to micro-organisms and consequently inhibitory in ready biodegradability tests due to the high initial test concentration used. Toxicity by Tetramine di-C16 -18 in the Closed Bottle test is best detected prior to the onset of the biodegradation of the test substance through suppression of the endogenous respiration (lower oxygen consumption in the presence of a test substance as compared to the control). In a standard Closed Bottle test, inhibition of the endogenous respiration by Tetramine di-C16 -18 was still noted after 42 days (AkzoNobel 2016). Inhibitory effects of fatty amine derivatives are known especially fatty amine derivatives with long alkyl chain lengths (Dean Raymond and Alexander 1977; van Ginkel, 1995).

Tetramine diC16 -18 is also poorly water soluble and adsorbs onto solids resulting in limited bioavailability of Tetramine di-C16 -18. The toxicity of Tetramine di-C16 -18 can be decreased by introducing for instance silica gel or humic acid (endogenous respiration is not inhibited anymore in test with these substances). However these methods further reduce the bioavailability of Tetramine di-C16 -18, thereby further lowering the biodegradation rate (AkzoNobel, 2016).

Due to the toxicity and its high potential to adsorb, it is very unlikely that justifiable results can be obtained in ready biodegradability tests with Tetramine di-C16 -18. For very toxic substances, the specified high test substance concentrations are controversial because substances are present in the environment in the sub μg/L range.

Tetramine di-C16 -18 can be removed completely from waste water in biological wastewater treatment plants as demonstrated in a semi-continuously operated activated sludge unit (SCAS). In this unit Tetrameen 2HT is removed by both biodegradation and adsorption. Analysis of the parent compound adsorbed onto the activated sludge shows that approximately 40 to 50% of the Tetramine di-C16 -18 is removed by biodegradation. The complete removal of Tetramine di-C16 -18 assessed by measuring organic carbon removal demonstrates that water soluble substances are not formed during the biodegradation of Tetramine di-C16 -18. The alkyl chains and the hydrophilic moiety, N,N’-bis(3-aminopropyl)-1,3-propanediamine of Tetramine diC16 -18 are both readily biodegradable (AkzoNobel unpublished results). The fraction of Tetramine di-C16 -18 degraded biologically in the SCAS unit is therefore most likely mineralized (ultimately biodegradable).

Although Tetramine di-C16 -18 is biodegradable, a classification as not persistent according to the REACH guidance is for the time being not possible.


AkzoNobel report (2015) Biodegradability of Tetrameen 2HT (CAS# 1623405-26-4) in the Closed Bottle test (OECD TG 301 D). F 15076 CG (GLP report).

AkzoNobel report (2016) Evaluation of the biodegradability of Tetrameen 2HT using the Closed Bottle test and the SCAS test F 15039 CG.

Dean-Raymond, D and M Alexander (1977) Bacterial metabo­lism of quaternary ammonium com­pounds Appl. Environ. Micro­biol. 33:1037-1041.

Ginkel, CG van (1995) Biodegradation of cationic surfactants In; Biodegradation of surfactants Eds M.R. Porter and R. Karsa In Blackie Academic & Professional,  pp 183-203