Dibutyl maleate

Toxicity to microorganisms

Description of key information

Activated sludge (3 hr): EC50 = 488.6 mg/; EC20 = 149.1 mg/l; EC10 = 80.2 mg/l		
Pseudomonas putida (5 hr): EC10 = 1003 mg/l
ETAD fermentation tube (1986/2009) (24 hrs): EC0 = 63 mg/l
ETAD fermentation tube (1977) (24 hrs): Toxicity Threshold (TT) = 40 mg/l

Key value for chemical safety assessment

EC50 for microorganisms:

488.6 mg/L

EC10 or NOEC for microorganisms:

80.2 mg/L

Additional information

Four studies are available where the toxicity to microorganisms has been investigated, two under aerobic and two under anaerobic conditions. In the anaerobic studies, the ETAD fermentation tube test was used as the test system. In both of them, the exposure period was 24 hours, which is far beyond the exposure period recommended in currently valid guidelines. Furthermore, as biodegradation in an STP is mainly an aerobic process, the toxicity to aerobic microorganisms is the more relevant endpoint. Therefore, the anaerobic studies serve as supporting information and were not taken into account for the identification of the key study.

In the first aerobic study, Pseudomonas putida was tested according to a modification of OECD 209 where activated sludge representing a community of microorganisms is used. The exposure period in this test was 5 hours, which is also beyond current standard. The resulting EC10 was 1003 mg/l. The second aerobic study was conducted according to OECD 209 with activated sludge from a domestic sewage treatment plant. There were no significant modifications of the test. The EC50 derived from this test was 488.6 mg/l, the EC20 was 149.1 mg/L, and the EC10 was 80.2 mg/L. As the EC50 derived from this study is lower than the one derived from the study with Pseudomonas putida, it was selected as the key study.