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Ecotoxicological information

Short-term toxicity to fish

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Description of key information

In the acute fish study with AIBN according to OECD guideline 203 it was found that the 96h-LC50 for 2,2'-azobis[2-methylbutyronitrile] is greater than the maximum water solubility.


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 lethal and sub-lethal effects on newly fertilized zebra fish eggs and hatchlings in Dutch Standard Water (DSW) dilution water.

An acute fish study according to OECD 203 is available for AIBN. To show similar behavior of the two substances identical tests in parallel were conducted. The objective of this study was to compare the effects of the tested chemicals on newly fertilized zebra fish eggs and hatchlings over an exposure period of 96 hours according to an approach based on the OECD 236 guideline. Additional non-lethal observations were also conducted. The OECD 236 has been shown to correlate well with adult acute fish data for acute toxicity purposes. 

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 100 mg/L (nominal) was used for both substances. Based on lethality both materials can be considered to have an acute LC50 of >100 mg/L for fish species.

Key value for chemical safety assessment

Additional information

No short-term toxicity to fish study with the test substance is available. A short-term fish study with 2,2’-azobis(isobutyronitrile) was used as a read across to fulfill the data gap for the test substance. The underlying hypothesis for the read-across is that based on the structural and functional group similarity, the presence of the nitrile group in both substances is likely driving aquatic toxicity. Additional documentation, provided within the IUCLID Assessment Reports section, supports the read-across approach.

A semi-static, 96-hour test was conducted in Danio rerio with 2,2‘-azobis(isobutyronitrile). The 96-hour LC50 in Danio rerio was reported as 580 mg/L in the original study report. The reported 96-hour NOEC was 250 mg/L. Since the reported LC50 of 580 mg/L is above the substance water solubility of ~318 mg/L the 96h-LC50 for 2,2'-azobis[2-methylbutyronitrile] is also greater than the maximum water solubility.