Nitrapyrin

Short-term toxicity to aquatic invertebrates

Description of key information

LC50 = 2.20 mg/L (Daphnia magna Straus), EPA OPP 72-2, Weinberg (1991)

LC50 = 5.78 mg/L  (Daphnia magna Straus), EPA publication method, McCarty (1977)

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Effect concentration:

2.2 mg/L

Additional information

Two studies, reporting the acute toxicity of the substance to aquatic invertebrates are available.

The key study, reported by Weinberg (1991), was conducted under GLP conditions and in accordance with the standardised guideline EPA OPP 72-2. It was assigned a reliability score of 1 in line with the criteria of Klimisch et al. (1997).

During the study, groups of 30 Daphnia magna Straus were exposed to solutions containing mean measured concentrations of active ingredient at 0.95, 1.50, 2.57, 4.00, 7.57 or 9.64 mg/L, a DMF control, or a laboratory water control, under flow-through conditions. The test vessels were observed daily for mortality and sub-lethal effects. All of the daphnia exposed to ≥ 7.57 mg/L died during the exposure period.

Under the conditions of the study, the 48 hour LC50 was determined to be 2.20 mg/L with a 95% confidence interval of 1.86 - 2.57 mg/L. Due to mortality at the lowest test concentration, the 48-hour mortality threshold concentration was less than 0.95 mg/L. Based on statistical analysis of the concentration/response data, the no-observed-effect concentration (NOEC) was calculated to be 1.50 mg/L.

 

Supporting information is available in the form of an acute toxicity study, as reported by McCarty (1977), which followed test methods described in the EPA publication "Methods for Acute Toxicity Tests with Fish, Macroinvertebrates, and Amphibians". Since the study was not conducted under GLP conditions, and since reference was not made to standardised guidelines, it was assigned a reliability score of 2 in line with the criteria of Klimisch et al. (1997).

During the study three replicate groups of 10 Daphnia magna Straus were exposed to test material concentrations of 3.70, 5.60, 7.50, 10.00 and 13.50 mg/L, a dilution water control, or a solvent (acetone) control. The daphnia were observed for mortality at 24 and 48 hours. The control daphnia exhibited 10% mortality during the test. All daphnia exposed to the two highest test material concentrations of 13.50 mg/L, or 18.00 mg/L, died. Under the conditions of the study the 48 hour LC50 was determined to be 5.78 (4.97 - 6.54) mg/L.

 

The findings from the two studies are in good agreement with each other, however; being the key study, the LC50 value of 2.20 mg/L is taken forward for risk assessment.