7a-ethyldihydro-1H,3H,5H-oxazolo[3,4-c]oxazole

Short-term toxicity to aquatic invertebrates

Description of key information

Four acute invertebrate toxicity tests were conducted with EDHO according the standard guidelines in effect at the time the tests were conducted.   Two Daphnia magna acute toxicity tests, one Eastern oyster acute shell deposition test, and one pink shrimp (Pinaeus duorarum) acute toxicity test were conducted.
The most recent study was an acute toxicity test with Daphnia magna, conducted according to the OECD 202 daphnia toxicity guideline.  This test was conducted in 2007 under GLP with flow-through conditions and with analytical verification of exposure concentrations. As a result, this study was chosen as the key study for this endpoint.  Recoveries from test solutions were low, averaging about 30% of nominal (except for the lowest test concentration at around 18% of nominal) yet were consistent over the duration of the exposure.  Results were based on the mean measured concentrations of the recoveries at 0 and 48 hours.  The 48-hour EC50 was determined to be 16.9 mg EDHO/L.  
The older test Daphnia magna test was conducted under GLP according to the USEPA-660 guideline, which was similar to the OECD 202 guideline.  Results were expressed based on nominal concentrations.  The 48-hour EC50, based on immobilisiation, was 42 mg EDHO/L.
  
The final two invertebrate acute tests were conducted on marine species: the Easter oyster (Crassostrea virginica) and the pink shrimp (Pinaeus duorarum) and were non-GLP, non-analytical.  The endpoint for the oyster test was new shell growth and the EC50, determined based on this endpoint, was35 mg EDHO/L nominal.  The acute test with the pink shrimp determined a 96-hour LC50, based on mortality, of 138 mg EDHO/L nominal.

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Effect concentration:

16.9 mg/L

Additional information

Four aquatic invertebrate acute toxicity tests were conducted, two freshwater exposures with the Daphnia magna and two marine exposures, one with the Eastern oyster and one with the pink shrimp. The organisms were exposed to EDHO via static or flow-through exposures. The most recent Daphnia magna test was conducted according to GLP under the OECD202 daphnid acute toxicity testing guideline and included analytical verification of exposure concentrations. Thus, this study was chosen as the key study for this endpoint. The 48-hour EC50, based on immobilization, was 16.9 mg EDHO/L measured. This test indicated that the Daphnia magna was the most sensitive invertebrate species. The remaining acute values were 42 mg EDHO/L nominal (LC50 based on immobilization) for Daphnia magna based on the older static test, 35 mg EDHO/L nominal (EC50 based on new shell growth) for the Eastern oyster, and 138 mg EDHO/L nominal (LC50 based on mortality). 

 

The key study for aquatic invertebrate acute toxicity is the most recent test. This test was conducted under GLP according to most recent OECD 202 guideline, exposure was flow-through to continually replace test chemical, and included analytical verification of the exposure concentrations.  While recoveries were low according to analytical results, they were consistent throughout the exposure and provide a valid exposure to determine the toxicity of EDHO to the Daphnia magna.