1-hydroxy-4-methyl-6-(2,4,4-trimethylpentyl)pyridin-2(1H)-one, compound with 2-aminoethanol (1:1)

Endpoint summary

Description of key information

Octopirox forms chelate complex with two and three valent ions like Fe(II), Fe(III), Al(III). If the test organism is dependent from such ions during the test e.g. algae, daphnia, this will influence growth and survival. As these ions mentioned before are ubiquitous in the sewer, the sewage treatment plant and in the environment e.g. river Octopirox forms immediately these chelate complexes. In order to avoid interference with the necessary test conditions in the Guideline tests and to avoid unrealistic test test settings e.g. pronounced toxicity by interference with essential ions, the aquatic ecotoxicity tests were carried out in river water where the ions mentioned above are present. For algae the Octopirox Fe(III) complex had to be tested as otherwise the required growth rate for the test according OECD 201 could not be achieved.

For all three trophic levels (fish, daphnia and algae) are acute and for daphnia and algae are chronic data available. Octopirox is most toxic to daphnia. For daphnia one acute and one chronic study is available. The chronic 21d Daphnia reproduction study is the basis for the PNEC_aquatic, together with the E_rC10 Algae which results in an Application factor of 50. It is important to note that the daphnia study could not have been carried in reconstituted water with ElendtM4 medium as Octopirox would have chelated the essential ions in the nutirent solution. River water was the test medium to overcome the issue described before.For the risk assessment only river water tests were used to ensure comparability.

In Table 6.1-1 the different test results which are most relevant are given. All aquatic studies were carried out with active ingredient (a.i).

Table 6.1-1    Test results from Octopirox - most relevant Acute and Chronic aquatic tests (active ingredient (a.i.))

the Algae test was carried out with the Octopirox Fe(III) complex

Test type	Test medium	Species	Effect			Guideline
Acute fish	River water	Danio rerio	LC50 (96h)	1.9	mg/l	OECD 203
Acute Daphnia	River water	Daphnia magna	EC50 (48h)	1.8	mg/l	OECD 202
Algae	River water	Desmodesmus subspicatus	ErC50 (72h)	10.8	mg/l	OECD 201
Sludge respiration inh	Tap water	Non-adapted sludge	EC50 (3h)	583	mg/l	OECD 209
Chronic daphnia	River water	Daphnia magna	NOECrepro (21d)	0.13	mg/L	OECD 211
Chronic Algae	River water	Desmodesmus subspicatus	ErC10 (72h)	6.3	mg/L	OECD 201