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Cationic surfactants like HYEQS are difficult to test in the aquatic compartment as they are sorbing strongly to solids. Normally the analytical recovery of the cationic is good at the beginning of the test but at the end of the test recovery is often below the acceptable minimum recovery. Lowering of the recovery could be related to sorption of the substance to the test container walls but sorption occurs also to the negatively charged surface of the test organism e.g. of algae or fish. Substance sorbed to the organism means the substance is still present in the test system and if it is demonstrated that sorption to the test container walls is negligible the nominal concentrations at test begin can be used to derive the L(E)Cx values. Aquatic studies not addressing this difficult behaviour of cationics in aqueous test systems may result in effect values being unrealistically low especially when a (geometric) mean concentration from start and end concentration is calculated.

For all three trophic levels (fish, daphnia and algae) acute and chronic data are available. HYEQS is most toxic to algae. For algae five valid studies are available. Three of them have the validity score (1) ‘valid without restrictions’ and these are considered for the derivation of the PNECaquatic.

 

In Table 5.1 the different test results which are most relevant are given. Some studies were carried out with a 40% aqueous solution. The results from these studies are normalized on active ingredient.

 

Table 5.1    Test results from HYEQS - most relevant Acute and Chronic aquatic tests (results are based on active ingredient (a.i.))

Species Species type Endpoint Value Unit Guideline
Acute fish Danio rerio LC50 (96h) 4.20 mg/l OECD 203
Acute Daphnia Daphnia magna EC50 (48h) 0.19 mg/l OECD 202
Algae Chlorella vulgaris ErC50 (72h) 0.90 mg/L OECD 201
Algae Desmodesmus subspicatus ErC50 (72h) 0.14 mg/l OECD 201
Sludge respiration inh   EC50 (3h) 19 mg/l OECD 209
           
Chronic fish Danio rerio NOEC (28d) 0.16 mg/L OECD 210
Chronic daphnia Daphnia magna NOECrepro (21d) 0.10 mg/L OECD 211
Chronic Algae Chlorella vulgaris ErC10 (72h) 0.55 mg/L OECD 201
Chronic Algae Desmodesmus subspicatus ErC10 (72h) 0.04 mg/L OECD 201
Chronic Algae Periphyton NOEC (lowest, 28d) 0.02 mg/L no Guideline