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

BIODEGRADATION IN WATER: SCREENING TESTS

AEROBIC TESTS - Table 1

Guideline	Test substance	Duration	Endpoint	Biodegradation	Result
OECD 301B	Octopriox	28d	CO2 Evolution	6 %	not readily biodegradable under the test conditions
OECD 301B	2 -Pyridinol-N-oxid	28d	CO2 Evolution	77%	readily biodegradable
OECD 301B	Octopirox Fe(III)	28d	CO2 Evolution	6 %	not readily biodegradable under the test conditions
OECD 301D	Octopirox	28d	O2 Consumption	14%	not readily biodegradable under the test conditions
OECD 302B	Octopirox	28d	DOC removal	n.a.	sorption and biodegradation cannot be distinguished

ANAEROBIC TEST - Table 2

Guideline	Test substance	Duration	Endpoint	Biodegradation	Result
OECD 311	Octopirox	58d	Biogas Evolution	0 -10 %	not biodegradable under the anaerobic test conditions

BIODEGRADATION IN WATER: SIMULATION TEST IN SEWAGE TREATMENT PLANT

In the followingTable 3a Mass balance is given for the Simulation test system based on daily sampling over 24d

	Effluent	Sludge	Total	Sorption to Glass& Tubing (estimated)	Remark
95% CI	3.5 - 4.1 %	85 - 95 %	87 - 99 %	n.a.	analytical recovery forOctopirox was excellent
arithm. mean	3.8 %	90 %	93 %	< 5%	Biodegradation is minor

For the Sewage treatment modelling the mass balance was set to 4% release to effluent and 96% to sewage sludge.

BIODEGRADATION IN SEDIMENT

No data are available. Based on the aquatic Biodegradation data listed above rapid biotic degradation is not expected. As Octopirox is rapidly degraded by Direct photolysis in water this is the rate determining step for the fate and not biodegradation. Therefore a Sediment Simulation Test is not warranted.

BIODEGRATION IN SOIL

No data are available. Based on the aquatic Biodegradation data listed above rapid biotic degradation is not expected. As Octopirox is rapidly degraded by Direct photolysis in water this is the rate determining step for the fate in the aquatic compartment and not biodegradation. As Direct Photolysis on soil surfaces may also occur a Soil Simulation test is not warranted.

SUMMARY ON BIODEGRADATION

AQUATIC BIODEGRADATION

Whereas 2 -Pyridinol-N-oxid which is the unsubstitueted moeity of Octopirox is readily biodegradable Octopirox is not. The reason is most likely the branched alkyl side chain. This means the rate for ultimate biodegradation of Octopirox compared to 2 -Pyridinol-N-oxide is much lower due to the slow degradation of the alkyl side chain. But Octopirox is not recalcitrant especially due to the rapid Direct photolysis in water (see IUCLID Section 5.1.3).

SEDIMENT & SOIL BIODEGRADATION

Based on the data from the biodegradation tests in water rapid biodegradation is not expected in sediment and soil. As Direct photolysis in water is rapid this is the rate determining step in the fate of Octopirox in water a Sediment Simulation test is not warranted. Direct photolysis can also occur on soil surfaces and therefore a Soil Simulation test is not warranted.