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Biodegradation screening tests are available for various structurally related alkyl-1,3-diaminopropanes. All alkyl-1,3-diaminopropanes under consideration consist of carbon, hydrogen and nitrogen only. The basic structure of all alkyl-1,3-diaminopropanes consists of a hydrocarbon chain with a 1,3-propanediamine group at the end of the chain. The only difference consists of differing chain lengths and slight variations in the degree of saturation in the alkyl chain. Since the majority of the alkyl chains consist of C12to C18units, and the unsaturated part is mainly located in the more central part of the alkyl chain, significant changes in chemical behavior and/or reactivity is not to be expected. Therefore the experimental data available for this group of alkyl-1,3 -diamines are used for the evaluation of the biodegradability of  N-C12 -14–propane-1,3-diamine.

Based on the available studies on biodegradation, all alkyl 1,3 -diaminopropanes (C10 - C18) are considered to be readily biodegradable. The 10-days-window criterion does not need to be evaluated as the alkyl 1,3 -diaminopropanes are UVCB substances. No simulation tests for degradation rates under environmental conditions are available, therefore the default values suggested in the REACH guidance may be used. Because of the observed ready biodegradability there is no requirement for performing a soil biodegradation test (Annex IX. 9.2.1.3).However a soil biodegradation test is performed with the structurally related14C hexadecyl amine. The observed half-life of 14C hexadecylamine of 8.98 days at 20 °C as determined according to an OECD 307 test is used for read-across to the diamines as both the primary alkyl amines and diamines are structurally related, readily biodegradable and have a similar sorption to soil. This means that for the risk assessment a half-life for soil and sediment of 17 d at 12°C are considered realistic for diamines.

A waste water treatment simulation test was performed with amines, N-C16-18-alkyl (even-numbered) propane-1,3-diamine (133779-11-0). 99.4% removal was observed using specific chemical analyses (LCMS/MS) of the effluent during day 56 to 60 (n=5). In addition, sorption to sludge was measured and this accounted for 4.1% of the total removal which means that 95.3% was removed by biodegradation.

Summary table of degradation rate constants in various (eco) systems based on the ready biodegradability of alkyl-1,3-diaminopropanes:

 

(Eco)system

Method

Half-life

Surface water (fresh)

TGD default value for readily biodegradable substances

15 days

Surface water (fresh) sediment

Read across from half-life hexadecylamine

17 days

Marine water

TGD default value for readily biodegradabl substances

50 days

Soils

Read across from half-life hexadecylamine

17 daysa

Degradation in sewage treatment plants

Determined in STP simulation test

99.4% removal primarily by biodegradation

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