sodium 2-{N-[(3,5-difluorophenyl)carbamoyl]ethanehydrazonoyl}nicotinate

Short-term toxicity to aquatic invertebrates

Description of key information

The 48-hour EC50 concentration for daphnids exposed to the read across substance (free acid of Difluenzopyr sodium salt) was 15.0 mg a.i./L. The 95% confidence limits were 10.5 and 21.7 mg a.i./L. The 48-hour no mortality/immobilization concentration and no observed effect concentration, determined by visual examination of the effects data, was 9.7 mg a.i./L.

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Effect concentration:

15 mg/L

Additional information

The acute toxicity of the read across substance (free acid of Diflufenzopyr sodium salt) to the freshwater crustacean Daphnia magna was assessed according to Procedures outlined in Series 72 of Pesticide Assessment Guidelines. Subdivision E Hazard Evaluation: Wildlife and Aquatic Organisms (equivalent to Directive 84/449/EEC, C.2 and the OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test).

The key study was conducted over a 48 hour exposure period under static conditions with nominal concentrations of 16, 26,43, 72 and 120 (a.i.) mg/L. Daphnids were exposed to a geometric series of ten test concentrations and a negative (well water) control. Two replicate test chambers were maintained in each treatment and control group, with 10 daphnids in each test chamber. Nominal test concentrations were selected in consultation with the Sponsor, and were based upon the results of range finding toxicity tests. Nominal test concentrations were 1.21, 2.02, 3.36, 5.60, 9.33, 15.6, 25.9, 43.2, 72.0, and 120 mg active ingredient (a.i.)/L. Measured test concentrations were determined from samples of test water collected from each treatment and control group at the beginning and end of the test.

Daphnids were impartially removed from holding tanks in groups of two and released into the exposure chambers at test initiation. Observations of mortality and other clinical signs of toxicity were made at approximately 21, 24, and 48 hours after test initiation. Cumulative percent mortality in the treatment groups were used to calculate EC50 values and 95% confidence limits at 24 and 48 hours. The no mortality or immobilization concentration and the no observed effect concentration were determined by visual examination of the mortality and clinical observation data.

The 48 -hour EC50 concentration for daphnids exposed to test substance was 15.0 mg a.i./L. The 95% confidence limits were 10.5 and 21.7 mg a.i./L. The 48-hour no mortality/immobilization concentration and no observed effect concentration, determined by visual examination of the effects data, was 9.7 mg a.i./L.