4-methylpentan-2-ol

Biodegradation in water: screening tests

Description of key information

The substance is considered to be readily degradable on the basis of the results of a well reported, GLP-compliant, guideline ready biodegradability study, without deviations, which is considered to be key, and which is supported by a study reporting a BOD5/ThOD ratio of 0.84.  Both reports agree that the substance is readily biodegradable under the conditions of the tests.

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable

Additional information

The key study is a Klimisch-1, GLP-compliant, guideline study without deviation carried out in 1998 according to the Manometric Respirometry test (OECD 301 F, EC C.4-D). Nominal initial test substance concentration was 100 mg/L. The test was performed using aerobic activated sludge microorganisms from the Oakley Sewage Treatment Works, which treats predominantly domestic waste, at a concentration of 30 mg solids/L in the test mixture. The test substance achieved a mean degradation of 10% around day 3.5, 60% after 9 days, and 85% by the end of the study. The following validity criteria were met: the oxygen demand of the inoculum control was ≤60 mg O2/L; the pH of the test substance flasks were in the range 6.0 to 8.5 at the end of the test and the reference substance achieved >60% degradation within 14 days. The day-9 result clearly shows that the 10-day window criterion was met. The substance is considered to be readily biodegradable under the conditions of the test.

A supporting study reports the BOD5 and COD of the substance to be 2.37 g O2/g and 2.60 g O2/g, respectively.  The BOD test was conducted in accordance with the standard dilution method (APHA "Standard Methods" No. 219 (1971)) at 20 ± 1ºC for a period of 5 days. The only deviation from the APHA standard was the addition of 0.5 mg/l allylthiourea in each test to prevent nitrification. 500 ml test solutions were seeded with a filtered 10 ml volume of the effluent from a biological sanitary waste treatment plant. The authors reported that in some cases an adapted seed was prepared and used, although in no case was inducement of adaptation tried exhaustively. The degree of adaptation of the seed in the case of this substance, if any, is not known. Duplicate tests were run on a mixture of glucose and glutamic acid, as recommended in the APHA method, as a means of checking the activity of the inoculum. The COD test was conducted in accordance with the standard potassium dichromate method described in ASTM D 1252 -97 (reapproved 1974). The BOD5/COD ratio from these results is 0.91. As indicated in the REACH Endpoint Specific Guidance sectionR.7.9.5.1; where no other measured degradability data are available, BOD5 data can be used for classification purposes, but where the chemical structure is known, a calculated theoretical oxygen demand (ThOD) value should be used instead of the COD. According to Annex IV of OECD 301, the ThOD of this substance can be calculated to be 2.82 g O2/g, which gives a BOD5/ThOD ratio of 0.84. This value is greater than 0.5, above which a substance can be considered to be readily degradable. This outcome supports the conclusion drawn from the key study.