2,6-xylidine

Biodegradation in water: screening tests

Description of key information

2,6-Xylidine is not readily biodegradable (according to the OECD criteria). If the inoculum is adapted to the test substance and after a prolonged contact time, biodegradation occurs.

Key value for chemical safety assessment

Biodegradation in water:

under test conditions no biodegradation observed

Additional information

 

For assessing the biodegradability of 2,6-Xylidine a weight-of-evidence approach was applied based on studies performed by BASF and a study by NITE.

The Japanese authorities performed a ready biodegradability test according to OECD Guideline 301C under GLP. The test was performed in 2001. The test lasted 28 days and a mixture of sewage, soil and natural water was used as inoculum in this study. Biodegradation was followed by oxygen consumption, TOC removal and test material analysis. After 28 days of incubation, no biodegradation was observed (0% BOD, 1% TOC removal, 0% test material removal; J-Check, 15-04-2019 (search date), study no.:21548).

Several tests according to OECD TG 301F and 302B were performed by BASF AG (1993 & 1994) using inoculum with activated sludge and effluent mixed from domestic and industrial sources. In some studies, inoculum was taken from a previous study for reasons of adaptation of the microbial biomass to the test substance.

In the ready biodegradability study with non-adapted inoculum following OECD 301F (BASF AG, 1993; report no. 92/2467/26/1), no biodegradation was observed over a period of 52 d (0% BOD). The reference substance (aniline) was shown to be readily biodegradable. The inhibition control (test substance + reference substance + inoculum) proved that 2,6-xylidine does not inhibit the degradation activity of the inoculum (49% DOC removal after 52 d).

In the following ready biodegradability experiments following OECD 301F, adapted inoculum was used which was taken from previous biodegradability tests with 2,6-xylidine. As a result the biodegradation was higher after 28 d and after prolonged incubation. The results of the available studies are summarized in the table below.

Reference	Inoculum	Biodegradation: 28 d	Biodegradation 2: prolonged incubation	Remarks
Ready biodegradability tests according to OECD 301F	-	-	-	-
BASF AG, 1993; 92/2467/26/1	mixed inoculum, not adapted	0% BOD	≤ 3% BOD after 52 d	Abiotic control: 5% BOD, 0% DOC removal
BASF AG, 1994; 92/2467/26/3	mixed inoculum, adapted	≤ 23% BOD	≤ 61% BOD after 42 d ≤ 72% BOD after 60 d	-
BASF AG, 1993; 92/2467/26/4	mixed inoculum, adapted	≤ 47% BOD	≤ 77% BOD after 52 d	-
BASF AG, 1994; 92/2467/26/5	mixed inoculum, adapted	≤ 56% BOD	≤ 67% after 35 d ≤ 74% after 42 d ≤ 75% after 49 d	-
Inherent biodegradability test according to OECD 302B	-	-	-	-
BASF AG, 1993; 92/2467/10/1	mixed inoculum, not adapted	45% DOC removal	76% DOC removal after 31 d 98% DOC removal after 36 d
BASF AG, 1993; 92/2467/10/3	activated sludge, industrial	83% DOC removal after 11 d	- 98% DOC removal after 36 d	Abiotic control: 98% DOC removal after 11 d

 

Two inherent biodegradability studies were also performed. One study was set up with the non-adapted mixed inoculum as above, the other with activated sludge from an stp treating industrial sewage. The substance is not inherently biodegradable based on the study with the mixed inoculum (BASF AG, 1993; report no. 92/2467/10/1). The second test with industrial activated sludge as inoculum showed a high elimination rate already after 11 d (83% DOC removal); however, the abiotic control showed that the removal was due to evaporation only (98% in 11 d).

It can be concluded that 2,6-xylidine is not readily and not inherently biodegradable using non-adapted inoculum. Under enhanced conditions (adapted inoculum, prolonged exposure), the substance is biodegradable.