Chlorpyrifos

Toxicity to soil macroorganisms except arthropods

Link to relevant study record(s)

Reference

Endpoint:

toxicity to soil macroorganisms except arthropods: short-term

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 207 (Earthworm, Acute Toxicity Tests)

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method C.8 (Toxicity for Earthworms: Artificial Soil Test)

Deviations:

no

GLP compliance:

yes

Specific details on test material used for the study:

Batch Number: RM 1946
Purity: 97.4%

Analytical monitoring:

no

Vehicle:

yes

Remarks:

acetone

Details on preparation and application of test substrate:

- Method of mixing into soil: For each group, the dose was thoroughly mixed with a small pre-mix of soil and the vehicle allowed to evaporate off prior to incorporation with the main soil bulk. Water was gradually mixed with the treated soil to give a moisture content equivalent to 35% of the dry weight.
- Method of application to soil surface: The test substance was applied as solutions in acetone prepared on the day of dosing
- Controls: Negative control soil was treated with vehicle only
- Chemical name of vehicle: Acetone
- Evaporation of vehicle before use: Vehicle was allowed to evaporate before use

Test organisms (species):

Eisenia fetida

Animal group:

annelids

Details on test organisms:

TEST ORGANISM
- Common name: Earthworm
- Source: Mr. D. Saunders, Fox Road, Bourn, Cambridgeshire, England
- Weight at test initiation: 300-337 mg

ACCLIMATION
- Acclimation period: One day

Study type:

laboratory study

Substrate type:

artificial soil

Limit test:

no

Total exposure duration:

14 d

Test temperature:

25-27°C

Moisture:

34-35%

Details on test conditions:

TEST SYSTEM
- Test container (material, size): One-litre glass containers
- Amount of soil or substrate: 736 g wet weight
- No. of organisms per container (treatment): 10
- No. of replicates per treatment group: 4
- No. of replicates per vehicle control: 4

PROPERTIES OF SUBSTRATE
- Quartz sand: 70% w/w
- Kaolin clay: 20% w/w
- Sphagnum peat: 10% w/w
- Calcium carbonate was added to the soil mixture to give a pH of approximately 5.9

OTHER TEST CONDITIONS
- Photoperiod: Continuous
- Light intensity: 440 lux

EFFECT PARAMETERS MEASURED: Mortality was assessed by testing the reaction of each worm to a mechanical stimulus at either end. Any worms visible on the soil surface were observed daily for behavioural or pathological signs. Mortalities, live worms and those unaccounted for were recorded. Weights of worms were recorded in treatment replicates immediately prior to treatment and on Days 7 and 14.

VEHICLE CONTROL PERFORMED: Yes

Nominal and measured concentrations:

0, 95, 171, 309, 556, 1000 ppm

Reference substance (positive control):

yes

Remarks:

The LC50 values of chloroacetamide to the earthworm were determined in a similar study conducted in the year 1991.

Key result

Duration:

14 d

Dose descriptor:

LC50

Effect conc.:

209.9 other: ppm

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mortality

Remarks on result:

other: 95% confidence limits 191.9-232.0 ppm

Duration:

7 d

Dose descriptor:

LC50

Effect conc.:

297.6 other: ppm

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mortality

Remarks on result:

other: 95% confidence limits 274.1-311.9 ppm

Details on results:

- Mortality at end of exposure period: At 309, 556, 1000 ppm, 100% mortality was observed. At 95 and 171 ppm, 3 and 8% mortality was observed, respectively.
- Changes in body weight: Weight loss was observed in all groups. This was greater in treated groups than in the control, with some evidence of a treatment-related trend.

Results with reference substance (positive control):

The LC50 values of chloroacetamide to the earthworm were determined in a similar study and were as follows:
Day 7 LC50: 52 ppm (95% confidence limits 47-58 ppm)
Day 14 LC50: 37 ppm (confidence limits could not be reliably determined because the data consisted predominantly of 0% and 100% responses).

Validity criteria fulfilled:

yes

Conclusions:

7-day LC50 (earthworm): 297.6 ppm
14-day LC50 (earthworm): 209.9 ppm

Executive summary:

This study was designed to determine the acute toxicity (LC50) of the test substance to the earthworm in an artificial soil under laboratory conditions.

The study was conducted in compliance with OECD guideline 207 and EEC Directive 87/302/EEC, Part C.

Worms were randomly allocated to treatment, with four replicates often worms per treatment. The concentrations of the test substance were 0, 95, 171, 309, 556, 1000 ppm. On Days 7 and 14, the medium was emptied from the test containers and the worms removed for counting. The worms were observed for mortality, behavioural or pathological signs and weight.

At 309, 556, 1000 ppm, 100% mortality was observed. At 95 and 171 ppm, 3 and 8% mortality was observed, respectively. Weight loss was observed in all groups. This was greater in treated groups than in the control, with some evidence of a treatment-related trend.

Based on the distribution of mortalities the following LC50 values were calculated:

Day 7 LC50: 297.6 ppm (95% confidence limits 274.1-311.9 ppm)

Day 14 LC50 : 209.9 ppm (95% confidence limits 191.9-232.0 ppm)

Description of key information

7-day LC50 (earthworm): 297.6 ppm, 14-day LC50 (earthworm): 209.9 ppm; OECD 207, EU Method C.8; Reliability = 1