2,2'-azobis[2-methylbutyronitrile]

Toxicity to aquatic algae and cyanobacteria

Description of key information

A static, 72-hour study in Selenastrum capricornutum with the test substance was performed according to OECD guideline 201. The 72-hour EC₅₀ in Selenastrum capricornutum was 67 mg/L (measured initial) based on growth rate. The NOEC based on growth rate was 12.5 mg/L (measured initial).

 

In order to strengthen the read across from AIBN (CAS 78 -67 -1) to AMBN (CAS 13472 -08 -7) for aquatic toxicity the two substances were tested in parallel on the growth of Pseudokirchneriella subcapitata the green algae in standard OECD test medium. Although valid invertebrate studies exist for both materials. These endpoints were conducted by different laboratories many years apart with different preparation methods and different chemical analysis measurements and potentially inoculated with algae in different stages of growth. A combination of these factors makes comparison difficult. Identical tests in parallel were therefore conducted. Similar behavior can in this way be more reliably demonstrated. The objective of these tests was to screen the toxic effects of two structurally similar test substances in parallel on the growth of Pseudokirchneriella subcapitata the green algae in standard OECD test medium. No chemical analysis for quantification of the test substance concentration was performed during the study due to the stability of the test material already being demonstrated in existing tests. A test range up to 92.2 mg/L (nominal) was used for both substances. Growth inhibition curves for both materials at the NOEC, ErC10 and ErC50 are considered to fall very close together with 95% confidence limits. Results would fall within the same classification boundaries and differ less than a factor of 2 from one another.

AIBN ErC10 =5.2 mg/L

AIBN ErC50 = 20.3 mg/L

AIBN NOEC = 1.5 mg/L

AMBN ErC10 = 3.9 mg/L

AMBN ErC50 = 24.7 mg/L

AMBN NOEC = 1.5 mg/L

Key value for chemical safety assessment

EC50 for freshwater algae:

67 mg/L

EC10 or NOEC for freshwater algae:

12.5 mg/L