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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 PECaquatic,bulk/PNECaquatic,bulkapproach 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 PECaquatic,bulkis compared with the PNECaquatic,bulkderived 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 PECbulkclearly 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,C12 -14alkyl-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 (C12 -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. Therefore a read-across approach is considered justified.

An overview of the most relevant results is presented in the table.

 

 CAS number

Result

Reference

Daphnia

OECD 211

KEY Study

 

90640-43-0

 

21d-EC50 = 179 ug/L parental mortality, river water

 

Noack, 2008

Danio rerio

OECD 203

KEY Study

 

 68603-64-5

96h-LC50 = 148 ug/L, reconst lab water

Clariant, 1990

Pseudokircherniella subcapitata

OECD 201

KEY Study

 

 90640-43-0

72h-ErC50 = 65.2 ug/L, river water

72h-ErC10 = 40.6 ug/L, river water

Noack, 2009 

Daphnia

OECD 211

KEY Study

 

90640-43-0

21d-NOEC = 32 ug/L Reproduction, river water

Noack, 2008 

Microorganisms

OECD 209

Key Study

 

 90640 -43 -0

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 a 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.