Pyridine, alkyl derivs.

Biodegradation in water: screening tests

Description of key information

Pyridine, alkyl derivs. was shown to be inherently biodegradable, while the model constituent MEP was ready biodegradable, but failing the 10-day window. In the key study Pyridine, alkyl derivs. was tested according to OECD Guideline 302 C (Inherent Biodegradability: Modified MITI Test (II). After 28 days of exposure, the rate of degradation amounted to 56.6 % when estimated using the ratio BOD/COD and the test item was determined inherently biodegradable. In a supporting study according to EU Method C.4-C and OECD Guideline 301 B (CO2 Evolution Test) Pyridine, alkyl derivs. showed limited biodegradation, most likely due to cytotoxicity effects. 
In addition to biodegradation studies with Pyridine, alkyl derivs., a ready biodegradation study and a study on inherent biodegradation were carried out using the model constituent MEP. In a study according to OECD Guideline 301 E (Ready biodegradability: Modified OECD Screening Test) MEP was determined ready biodegradable, but failing the 10-day window. In a study according to OECD 302 B (Zahn-Wellens test) MEP showed inherent biodegradation, with 98.7 % degradation in 21 days.

Key value for chemical safety assessment

Biodegradation in water:

inherently biodegradable

Additional information

Key study 1 - Inherent biodegradation

A study was carried out according to OECD Guideline 302 C (Inherent Biodegradability: Modified MITI Test (II). The test item was investigated for its biodegradability during 28 days. The test article showed to be degradable to a certain extent. After 28 days of exposure, the rate of degradation amounted to 56.6 % when estimated using the ratio BOD/COD, whereas no degradation was observed when using the TOC-values. The standard compound, Aniline, was readily degraded after 7 and 14 days by 72.2 % and 79.0 % (BOD/ThOD), respectively.

Key study 2 – Ready biodegradation

The biodegradability of the test item was determined according to OECD Guideline 301 C (Ready Biodegradability: Modified MITI Test (I)). The inoculum activity and inhibition control tests with sodium acetate showed that the activity of the inoculum was sufficient, and that the test item partly inhibited the biodegradation of the reference substance. Based on the carbon content given by the sponsor, the results demonstrated that almost no biodegradation of the test item took place, with less than 4 % degradation after 28 days. Pyridine, alkyl derivs. is therefore assessed to be not readily biodegradable in this test. Notably, the low degradation may have been caused by inhibiting effects of the test item.

Support 2 - Ready biodegradation

Experimental determination of ready biodegradation was carried out with 5-ethyl-2-methylpyridine (MEP, CAS no.: 104-90-5, EC no.: 203-250-0). The read-across between the UVCB substance and the model constituent is justified. Ready biodegradation was tested according to OECD Guideline 301 E (Ready biodegradability: Modified OECD Screening Test). The test item was determined ready biodegradable, but failing the 10-day window.

Support 3 - Inherent biodegradation

Experimental determination of ready biodegradation was carried out with 5-ethyl-2-methylpyridine (MEP, CAS no.: 104-90-5, EC no.: 203-250-0). The read-across between the UVCB substance and the model constituent is justified. A test on inherent biodegradation was carried out according to OECD Guideline 302 B (Zahn-Wellens test). The test item biodegraded 98.7 % within 21 days and determined inherently biodegradable under the conditions of this test.