2-chloropropane

Biodegradation in water: screening tests

Description of key information

The substance exhibited little or no degradation when tested for ready biodegradability according to OECD 301 D, and exerted an inhibitory effect in the toxicity control.  Further studies may be needed to evaluate its biodegradability.

Key value for chemical safety assessment

Biodegradation in water:

under test conditions no biodegradation observed

Additional information

Ready biodegradability was tested according to the Closed Bottle test (OECD 301 D, EC C.4-E) and in compliance with GLP (IBR Forschungs GmbH for RWE-DEA Ag.). The test was performed with a nominal initial test substance concentration of 2 mg/L and inoculum from the domestic sewage treatment plant at Kläranlage Gümmerwald (Hannover, Germany), which was collected freshly on day 0 of the test and filtered through a paper filter. The test substance exhibited little or no degradation during the study, and exerted an inhibitory effect in the toxicity control. The reported results for the biodegradation of the sodium benzoate reference substance fell short of the OECD 301 D validation criterion of at least 60% in 14 days. However, a review of the author’s calculations showed that the value of m₀used for all of them was the mean day 0 value from the un-inoculated controls (10.0 mg/L). In comparison, the mean day 0 values for the inoculated blank, the reference substance and the test substance were 9.2, 9.8 and 8.8 mg/L, respectively. OECD 301 D directs that the day 0 value used should be that of the inoculated blank, except where this is different from the day 0 values of the test substance, when each calculation should use its own day 0 value. Recalculation of the biodegradation values in this way makes a marked difference to the results as follows:

	Isopropyl chloride		Sodium benzoate
	Reported	Recalculated	Reported	Recalculated
5 days	-5.5%	-16%	54%	72%
15 days	2.7%	-8.2%	57%	75%
28 days	14%	2.7%	75%	93%

 

The recalculated % biodegradation of the reference substance meets the validation criterion of at least 60% in 14 days. The overall outcome of the study remains unchanged in that, under the conditions of the test, the substance was not readily biodegradable and exerted an inhibitory effect on the inoculum. It remains possible that a repeat test using a lower initial test substance concentration and/or a higher concentration of inoculum might show biodegradability.