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Biodegradation in water: screening tests

Link to relevant study record(s)

Reference

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Reason / purpose for cross-reference:

read-across source

Preliminary study:

Pre-study solubility/dispersibility work was conducted, and confirmed that the test material was poorly soluble in water. Therefore additional solubility work was conducted to ascertain the method that would give the best testable dispersion;

A volatility check was performed on the test material by passing a steady stream of compressed air over a known weight of test material for 3 hours. This resulted in a 1% loss of test material over this time so the test material was considered not to be volatile. As such, it was concluded appropriate to adsorb the test material onto silica gel and disperse with the aid of high shear mixing as this method appeared to increase the dispersibility of the test material over the other methods.

Test performance:

No outstanding occurrences

Key result

Parameter:

% degradation (CO2 evolution)

Value:

16

Sampling time:

28 d

Details on results:

Points of degradation plot (10 carbon/l initial concentration):

1% degradation after 2 d

12 % degradation after 6 d

11 % degradation after 8 d

17 % degradation after 10 d

9 % degradation after 14 d

15 % degradation after 21 d

12 % degradation after 28 d

16 % degradation after 29 d

The test material at 10 carbon/l initial concentration attained 16% degradation calculated from the CO2 evaluation values after 28 days.

Results with reference substance:

Points of degradation plot (20 mg/L):

26 % degradation after 2 d

63 % degradation after 6 d

60 % degradation after 8 d

82 % degradation after 10 d

77 % degradation after 14 d

88 % degradation after 21 d

84 % degradation after 28 d

90 % degradation after 29 d

The reference substance at 10 carbon/l initial concentration attained 90 % degradation calculated from the CO2 evaluation values after 28 days, which exceeded 60% degradation requirement to validate the test

Validity criteria fulfilled:

yes

Interpretation of results:

other: not readily biodegradable

Conclusions:

The test material attained 16% degradation after 28 days and therefore cannot be considered to be readily biodegradable under the strict terms and conditions of OECD Guideline No 301B.

Executive summary:

In an assessment of ready biodegradability study, the substance was determined not to be readily biodegradable according to OECD guideline 301B "Ready biodegradability; CO2 Evolution Test" (referenced as Method C.4-C of Commission Directive 92/69/EEC and US EPA Fate, Transport andTransformation Test Guidelines OPPTS 835.3110 Paragraph (m).) given that substance attained 16% degradation after 28 days.

Description of key information

The test material attained 16% degradation after 28 days and therefore cannot be considered to be readily biodegradable under the strict terms and conditions of OECD Guideline No 301B.

Key value for chemical safety assessment

Biodegradation in water:

under test conditions no biodegradation observed