Nitrapyrin

Toxicity to soil macroorganisms except arthropods

Description of key information

15-day LC50 = 209 mg/kg dw (earthworm); EPA OPPTS 850.6200, Coulson et al. (1985)

56-day NOEC = 5.75 mg/kg soil dw (earthworm); OECD 222, ISO 11268-2, Ganßmann (2013)

Key value for chemical safety assessment

Short-term EC50 or LC50 for soil macroorganisms:

209 mg/kg soil dw

Long-term EC10, LC10 or NOEC for soil macroorganisms:

5.75 mg/kg soil dw

Additional information

Short term

The toxicity of the test material to earthworms was investigated in a study which was conducted under GLP conditions and in accordance with the standardised guideline EPA OPPTS 850.6200. The study was assigned a reliability score of 1 in line with the criteria of Klimisch et al. (1997).

During the study, Eisenia fetida were exposed to a series of concentrations of test material evenly incorporated into an artificial soil substrate. Worms were assessed for mortality and behavioural effects after 14 days in the initial test and after 7 and 15 days in the definitive test. The soil was tipped onto a sheet of 'Benchkote' and worms were recorded as dead if there was no response to a mechanical stimulus of their front end. Each batch of ten earthworms was weighed at the end of the test to determine any treatment related effect.

The highest concentration with no mortality was 100 mg/kg. The lowest concentration giving 100 % mortality was 320 mg/kg.

Control mortality was zero. No significant behavioural or bodyweight changes were observed at or below 180 mg/kg level.

Under the conditions of the study the 15-day LC50 value for the test material, to earthworms, was determined to be 209 mg/kg.

Long term

The long term toxicity of the test material to earthworms was investigated in a study which was conducted under GLP conditions and in accordance with the standardised guidelines OECD 222 and ISO 11268 -2.

During the study adult Eisenia fetida andrei were exposed to artificial soil which had been spiked with test material solution or vehicle control. There were 8 replicates per control and 4 replicates per test material treatment group; each replicate contained 10 earthworms. All worms were washed with tap water, dried with dry paper towels, weighed individually and randomly assigned to batches of 10 worms. The different batches were sorted into four classes on the basis of the total weight and one batch of each weight class was assigned to each treatment group (two batches for the control) to ensure weights were homogeneous. The earthworms were placed on the surface of the artificial soil after application.

After 4 weeks, the artificial soil was transferred to a tray and adult worms were counted, removed and weighed per replicate after they had been washed under tap water and dried on a dry paper towel. Missing earthworms and earthworms that failed to respond to gentle stimulation were considered to be dead. The remaining soil (without the adult worms) was then returned to the respective test containers.The offspring were then exposed for an additional 4 weeks after which time the juveniles were removed by placing the test units in a water bath at 50 to 60°C and counting all emerging worms. In addition the soil of each container was transferred to a tray and checked visually for any remaining young worms.

Under the conditions of the study no mortality was observed in any test material group or the control. The body weight of the earthworms exposed to test material were not statistically significantly different compared to the control up to and including the highest test concentration of 5.75 mg test item/kg soil. The reproduction rates of the worms were not statistically significantly different at any concentration tested when compared to the control.

The LC50 was therefore estimated to be greater than 5.75 mg test material/kg soil. The No Observed Effect Concentration (NOEC) for mortality of the earthworm Eisenia fetida was determined to be 5.75 mg test material/kg soil. The No Observed Effect Concentration (NOEC) for weight changes was determined to be the concentration of 5.75 mg test material/kg soil. The No Observed Effect Concentration (NOEC) for reproduction was determined to be 5.75 mg test material/kg soil.