Propanol, iminobis-, N-(C16-18 and C18-unsatd. alkyl) derivs.

Endpoint summary

Additional information

Several test results for closed bottle tests from 2009 are available for di (2 -hydroxypropyl)tallow amine (PFAPO T, CAS 1309955-79-0, old CAS 68951-72-4).

In the closed bottle test from 2009 a test substance concentration of 2 mg/L was tested by using river water and 2 g/bottle silica gel (report number 2.391.360).  The biodegradation percentages reached at day 28 in closed cottle test is 63 (based on ThODNH3) and 59 (based on ThODNO3) showing that the substance is readily biodegradable based on ThODNH3, which is over the threshold value of 60%. Assuming complete nitrification, and calculating the biodegradation based on ThODNO3 the biodegradation percentage is slightly below the 60% threshold value. For biomass formation also nitrogen is needed. However, PFAPO T has a relative high C:N ratio  and due to the omission of NH4-nitrogen in the mineral salts medium of the ready biodegradation screening test it is very unlikely that part of the test substance nitrogen is incorporated into the biomass. Based on the SCAS test results and also on the result of the valid closed bottle test from 2009 (test report ECRA 2.391.558) it is considered that there is sufficient weight of evidence that it can be assumed that primary fatty amine propoxylate tallow is readily biodegradable. Within this test 67% biodegradation (based on ThODNO3) and 71% (based on ThODNH3) were reached by using unadapted river water and silica gel. The toxicity of the substance to microorganisms is hampering the  biodegradation within a specific time frame. Therefore, silica gel was used to mitigate the toxicity to microorganisms. Consequently, the biodegradation rate is slowed-down by the use of slica gel (Timmer et al., 2020). Results of the SCAS test show that the substance will be ultimate biodegradable in a wastewater treatment plant. 

By summarizing all the available test data for biodegradation it is considered acceptable to classifiy di (2 -hydroxypropyl)tallow amine as readily biodegradable and not persistent justified by a weight-of-evidence approach. 

Besides to degradation by microorganisms also degradation in other biota like fish are anticipated for primary fatty amine propoxylates. Metabolic rates in fish were measured for a the higly similar substance 1 -Hexadecanamine (n-Primary C16amine, CAS 143-27-1) using an in vitro method with carp hepatocytes (Bernhard et al, 2006). The Km was estimated to be 0.152 1/d assuming only arterial blood supply to the liver, whereas a rate of 1.024 L/d was estimated considering both arterial and a portal blood supplies. The rate of 0.152 1/d leads to a fast metabolism in fish and results in a low bioconcentration.

 

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 propoxylates.

(Eco) system	Method	Half-life
Surface water	TGD default value	15 days half-life
Surface water sediment	Determined by read across	33.8 days half-life
Marine water	TGD default value	50 days half-life
Soils	Determined by read across	33.8 days half-life^a
Degradation in sewage treatment plants	Determined by read across	>99.97% removal primarily by biodegradation

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

Timmer et al. 2020, Application of seven different clay types in sorbent-modified biodegradability studies with cationic biocides DOI: 10.1016/j.chemosphere.2019.125643