2-nitropropane

Toxicity to aquatic algae and cyanobacteria

Description of key information

One GLP study and one non-GLP study conducted according to OECD guidelines 203 are available for the 2-nitropropane.
The key study determined a 72-hour ErC50 (based on growth rate) for 2-nitropropane of >887 mg 2-nitropropane/L in the freshwater green alga, Pseudokirchneriella subcapitata.  The supporting study determined a 72-hour EC50 for 2 nitropropane of 1088 mg 2-nitropropane in the freshwater green alga, Scenedesmus subspicatus (new name: Desmodesmus subspicatus).

Key value for chemical safety assessment

EC50 for freshwater algae:

887 mg/L

EC10 or NOEC for freshwater algae:

90 mg/L

Additional information

The key study was conducted recently, had analytical confirmation of test solution concentrations and was conducted under good laboratory practice (GLP) principles. Because of this it is determined to be high quality. The exposure (96-hour) was conducted using sealed test vessels to minimize volatilization of the test material from the test solutions during the exposure period in an sodium bicarbonate enriched medium. Analytical confirmation of test solution concentrations during the test confirmed that target concentrations were achieved. The test material was determined to be stable under the test conditions in the absence of algae. However, the presence of algae affected the stability of the test material. As concentration decreased, percent recoveries (of nominal) at these levels also decreased as well. This indicates that the most likely loss is due either to utilization of the test material as a carbon source or binding to the algae at concentrations below toxic levels. The ErC50, based on inhibition of growth rate, daphnid immobility was determined to be >887 mg/L, the highest concentration tested.  A NOEC of 90 mg/L was determined for growth rate inhibition. The supporting study was not conducted under GLP principles. The study report lacked detail but provided enough that it could be considered acceptable to provide supporting evidence with reservations. The exposure period in this study was also 96 hours but the pertinent 72-hour endpoints were reported. The study was conducted in sealed vessels with a CO2 enriched atmosphere This study determined an EC50 of 1088 mg/L. It was not specifically stated that growth rate was the endpoint but it is assumed based on some of the report verbiage.

 

Based on this information, the more recentfreshwater green algagrowth inhibition test is considered the key study for the toxicity to algae and cyanobacteria endpoint. The EC50 of >887 mg/L would result in a classification of Not Dangerous for this material based on daphnid toxicity.