Reaction mass of 2,4-dimethyl-6-phenyl-3,6-dihydro-2H-pyran and 2-methyl-4-methylene-6-phenyltetrahydro-2H-pyran and 4,6-dimethyl-2-phenyl-3,6-dihydro-2H-pyran

Biodegradation in water: screening tests

Description of key information

The ready and inherent biodegradability of the test substance was assessed in a series of tests based on OECD Test Guidelines. 
In the key study, the ready biodegradability of the test substance was determined by the manometric respirometry test.  The test substance undergoes no biodegradation after 28 days (no biodegradation after 32 days) in the test conditions. The test substance did not significantly inhibit intrinsic respiration at the test concentration and was therefore considered to be non-toxic to the inoculums at the test concentration. Thus, the test substance should be regarded as not readily biodegradable according to this test. 
In the two tests to assess inherent and ultimate biodegradability, degradation levels of approximately 27% were achieved indicating partial degradation of the substance under these test condictions. 

Key value for chemical safety assessment

Biodegradation in water:

under test conditions no biodegradation observed

Additional information

The ready and inherent biodegradability of the test substance was assessed in a series of tests based on OECD Test Guidelines.

In the key study, the ready biodegradability of the test substance was determined by the manometric respirometry test according to OECD Test Guideline 301 F. The test substance undergoes no biodegradation after 28 days (no biodegradation after 32 days) under the test conditions. The test substance did not significantly inhibit intrinsic respiration at the test concentration and was therefore considered to be non-toxic to the inoculums at the test concentration and the test substance was therefore regarded as not readily biodegradable according to this test. The key study’s conclusions were supported by a ready biodegradability test performed according to OECD Test Guideline 301 B using the CO₂evolution method. During the supporting study, the test substance achieved 15 % biodegradation in 28 days. The test substance therefore cannot be classed as being readily biodegradable.

To assess the inherent and ultimate biodegradability of the test substance a study was performed using a modification of OECD Test Guideline 301 B (CO₂evolution method using sealed vessels) whereby the test duration was extended from 28 days to 56 days. During this test, 27.4 % degradation was observed over 56 days. This conclusion was supported by a further test preformed according to OECD Test Guideline 301 B using sealed vessels and a modified method in which the microorganisms were acclimatised to the test substance. Over the 4 week test period, 27.9 % degradation was observed. When assessing inherent biodegradability it is not necessary to define limits on test duration. Biodegradation above 20% may be regarded as evidence of inherent, primary biodegradation, whereas biodegradation above 70% may be regarded as evidence of inherent, ultimate biodegradability. Thus Pelargene should be regarded as inherently primarily biodegradable according to these two inherent tests.