Amines, N-C12-18-alkyltrimethylenedi-

Endpoint summary

Additional information

Alkyl-1,3-diaminopropanes are poorly soluble in water and also have a strong tendency to adsorb to negatively charged surfaces such as suspended matter and test vessels or organic material (including dissolved organic matter such as humic acids). Many cationic substances in general but long chain alkyl polyamines in particular rank among the most difficult substances to test in environmental toxicology. Standard guideline studies are inappropriate to test substances with such properties and the current REACH Guidance Documents do not provide sufficient guidance concerning bioavailability and exposure assessment for cationic surface-active substances like the alkyl-1,3-diaminopropanes as these were written with normal hydrophobic chemicals in mind, failing to take into account the lack of bioavailability that occurs in the environment with these substances.

 

The long-term aquatic ecotoxicity tests with alkyl-1,3-diaminopropanes were therefore performed in river water to allow a PEC_aquatic,bulk/PNEC_aquatic,bulk approach and is considered to be conservative but more environmentally realistic than the standard method. This approach is based on PEC estimations representing ‘total aquatic concentrations’. To characterize the risk to the aquatic compartment the PEC_aquatic,bulk is compared with the PNEC_aquatic,bulk derived from river water ecotoxicity studies (ECETOC, 2001).

 

In order to class standard laboratory toxicity study valid, it is of particular importance that - besides information on test substance, test method / conditions and test organism used - suitable precautions are taken to prevent the loss of test substance by adsorption and that exposure concentrations are based upon measured levels.

For ecotoxicity tests performed using the bulk approach, however, adsorption to suspended matter and DOC is acceptable and only adsorption to glassware should be accounted for. For a valid bulk approach test the concentration-effect relationship should be based on the sum of adsorbed and dissolved substance in the volume of the medium tested. One of the advantages of the bulk approach tests with these difficult substances is that in the presence of suspended matter, humic acids and/or algae, the residual sorption to glassware will be negligible. The results of these bulk approach tests are therefore much easier to interpret, more environmental realistic, and if compared to PEC_bulk clearly provide a more appropriate assessment of risks for the environment. All effect values given are therefore based on the nominal test item concentrations.

 

Data of other diamines have been used as weight of evidence in the evaluation of the aquatic toxicity of N,C_{12 -18}alkyl-1,3 -diaminopropane. All alkyl-1,3 –diamines under consideration consist of carbon, hydrogen and nitrogen only. The basic structure includes a hydrocarbon chain with a 1,3 -propanediamine group at the end of the chain. The main difference consists of differing chain lengths (C_12-18) and slight variations in the degree of saturation in the alkyl chain. The available ecotox data reveal a comparable toxicity independent of the alkyl chain length.

 

The PNEC_{aquatic bulk} should be calculated using the assessment factor proposed by the TGD. As long-term NOECs from species representing two trophic levels are available (algae and daphnia) and these results cover that level showing the lowest L(E)C50 in the short-term tests, an assessment factor of 50 may be used. However based on the observed lower toxicity to fish not only for the alkyl-1,3 -diaminopropanes but also for primary fatty amines and mono and dialkyl quats it is considered unlikely that fish toxicity will be critical for alkyl-1,3 -diaminopropanes. Hence any additional toxicity testing with fish will not add scientific value to the ecotoxicity profile of the alkyl-1,3-diaminopropanes other than for obtaining a lower assessment factor. It is therefore concluded that for scientific reasons and in accordance to REACH legislation further testing on fish has to be avoided for reasons of animal welfare and that based on the weight of evidence available on ecotoxicity data for several cationic surfactants the use of safety factor of 10 is justified for the derivation of the PNEC_aquatic,bulk.

 

The key results are summarised in the table.

 

	CAS number	Result	Reference
Daphnia OECD 211 KEY Study	90640-43-0	21d-EC50 = 96.8 µg/L Reproduction, river water   21d-EC50 = 179 µg/L Parent mortality, river water	Noack, 2008
Danio rerio OECD 203 KEY Study	68603-64-5	96h-LC50 = 148 µg/L Reconst lab water	Clariant, 1990
Pseudokirchnerella subcapitata OECD 201 KEY Study	90640-43-0	72h-ErC50 = 65.2 µg/L 72h-ErC10 = 40.6 µg/L River water	Noack, 2009
Daphnia OECD 211 KEY Study	90640-43-0	21d-NOEC = 32 µg/L Reproduction River water	Noack, 2008
Microorganisms OECD 209 Key Study		3h-EC10 = 10.1 mg/L 3h-EC50 = 20.5 mg/L	Noack, 2008

 

It should be noted that the fish studies are the only studies performed with reconstituted lab water, while the studies with Daphnia and algae were performed with river water. Studies performed in river water show in general a factor of 5 lower toxicity due to the mitigation by river water constituents. Daphnia and algae are more sensitive than fish even if the results of river water tests for Daphnia and algae are compared with test results in reconstituted lab water for fish. It was decided not to repeat the fish study in natural river water for ethical reasons. The use of an assessment factor of 10 is therefore more difficult to justify but the factor of 5 or higher difference in toxicity is considered to be sufficient to support the use of an assessment factor of 10 instead of 50 in the derivation of the PNECaquatic.

 

The difference in sensitivity between fish and daphnia/algae is supported by results from comparable substances like primary alkyl amines and quats.