Avermectin A1a, 25-cyclohexyl-5-O-demethyl-25-de(1-methylpropyl)-

Short-term toxicity to aquatic invertebrates

Link to relevant study record(s)

Reference

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

key study

Study period:

From 27 to 29 Sep 1989

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Study run to a method comparable with current guidelines and to GLP.

Qualifier:

according to guideline

Guideline:

other: Environmental Assessment Technical Assistance Handbook, Section 4.08 (U.S. Food and Drug Administration, March 1987).

Deviations:

no

GLP compliance:

yes

Analytical monitoring:

yes

Details on sampling:

Two replicate water samples were removed and analyzed on test days 0 (test initiation) and 2 (test termination) from combined samples of all four replicate vessels of each test concentration and the control. Each exposure solution sample was collected from the appropriate midpoint of the glass container with a volumetric pipet.

Vehicle:

yes

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: A primary stock solution at a concentration of 4.75 mg/mL was prepared by diluting 0.506 g of nonlabeled test article (0.475 g as test substance) with 100 mL of acetone in a volumetric flask. A subsequent stock solution of 4.75 μg/mL was prepared by diluting 1.0 mL of the primary stock (4.75 mg/mL) with 1000 mL of acetone. Additionally, a stock solution was prepared with the tritium radiolabeled test article by transferring the entire contents of the vial of 3H test substance to a 50-mL volumetric flask and diluting to volume with acetone. This stock solution was assayed in triplicate by HPLC analysis to be 295 μg/mL. A final stock solution with a concentration of 5.0 μg/mL was prepared by diluting 5.0 mL of the 4.75 μg/mL nonlabeled test substance stock with 90 μL of a 295 μg/mL radiolabeled 3H test substance stock solution and then diluting with acetone to a total volume of 10 mL. Nominal test concentrations of 0.50, 0.34, 0.18, 0.11 and 0.067 μg/L were prepared by adding the appropriate amount of stock solution to 3000 mL of dilution water.
- Controls: Two sets of four control beakers were established, one set containing the same dilution water and maintained under the same conditions as the exposure concentrations, but containing no test substance; the second set containing the maximum amount of solvent present in any test vessel (0.1 mL/L) and was designated the solvent control.

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM
- Common name: Daphnid
- Strain: Daphnia magna
- Source: from laboratory cultures maintained at Springborn Laboratories, Inc., Environmental Sciences Division, Wareham Massachusetts.
- Age at study initiation (mean and range, SD): ≤ 24 hours
- Method of breeding: Daphnids were fed 2.0 mL of a unicellular green algae (Ankistrodesmus falcatus) and 0.5 mL of trout food, once daily. The food solution contained approximately 4E+07 cells/mL of algae and 5.0 mg/mL trout food.

No additional data

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

48 h

Post exposure observation period:

None stated

Hardness:

160-180 mg/L CaCO3

Test temperature:

18-20 ℃

pH:

7.6-8.2

Dissolved oxygen:

7.2-8.9 mg/L

Salinity:

None stated

Nominal and measured concentrations:

Nominal concentrations: 0.50, 0.34, 0.18, 0.11, and 0.067 μg/L
Measured concentrations: 0.32, 0.21, 0.11, 0.066, and 0.025 μg/L

Details on test conditions:

TEST SYSTEM
- Test vessel: 250 mL glass beakers
- Material, size, headspace, fill volume: The exposure solution depth in each replicate beaker was 6.3 cm with a surface area of 33 cm2.
- No. of organisms per vessel: 5
- No. of vessels per concentration (replicates): 4
- No. of vessels per control (replicates): 4
- No. of vessels per vehicle control (replicates): 4

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: prepared by fortifying well water based on the formula for hard water (ASTM 1980) and filtering it through an Amberlite XAD-7 resin column to remove any potential organic contaminants.
- Alkalinity: 120 mg/L CaCO3
- Ca/mg ratio: 170 mg/L CaCO3
- Conductivity: 500 μmhos/cm

OTHER TEST CONDITIONS
- Adjustment of pH:
- Photoperiod: 16 hours of light and 8 hours of darkness
- Light intensity: The test area was illuminated with Durotest Vitalite fluorescent lights at an intensity of 50 footcandles at the solutions' surface.

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) : During the definitive exposure, the number of immobilized daphnids in each replicate test vessel was recorded at 24 and 48 hours of exposure. Biological observations and observations of the physical characteristics of each replicate test solution were also made and recorded at 0, 24 and 48 hours. The temperature, pH and dissolved oxygen concentrations were measured at 0, 24 and 48 hours in one replicate vessel of each treatment level and the control. At test initiation, total hardness, alkalinity and specific conductance were measured and recorded in one replicate vessel of the highest nominal test concentration (0.52 μg/L) and one control.

TEST CONCENTRATIONS
- Range finding study
- Test concentrations: Nominal concentrations: 94-0.094 μg/L
- Results used to determine the conditions for the definitive study: Following 48 hours of exposure, 100% immobilization was observed among daphnids exposed to the three highest nominal concentrations (94-0.94 μg/L). During this same period, no immobilization was observed among test organisms exposed to the 0.094 μg/L treatment level. Based on the results of the range finding test, nominal concentrations of 0.50, 0.34, 0.18, 0.11 and 0.067 μg/L test substance were selected for the definitive study.

Reference substance (positive control):

not specified

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

0 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

mortality

Remarks on result:

other: 95% CL: 0.00008-0.00012 mg/L

Duration:

48 h

Dose descriptor:

NOEC

Effect conc.:

0 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

mortality

Remarks on result:

other: There was no mortality at this dose.

Details on results:

Following 48 hours of exposure, 100% immobilization was observed at the highest measured concentration tested (0.32 μg/L). Immobilization in the next three measured treatment levels (0.21, 0.11 and 0.066 μg/L) ranged from 75-30% after 48-hours of exposure and followed the concentration gradient established. No significant toxicant-related immobilization (≤10%) or adverse effects were observed in the remaining measured treatment level (0.025 μ/L). The immobilization of one daphnid out of twenty after 48 hours exposure in the lowest tested concentration is not statistically significant and of uncertain origin. Observations of ≤ 10% of the surviving daphnids caught on particulate matter were also noted in the control and solvent control group and are not attributed to exposure to test substance.
Throughout the test period no visible sign of undissolved material (e.g. precipitate, film on the solution's surface) was observed in the exposure solutions.

Reported statistics and error estimates:

Three statistical methods were available in the computer program: moving average angle analysis, probit analysis, and nonlinear interpolation with 95% confidence intervals calculated by binomial probability. Moving average angle and probit analyses yield statistically sound results only if at least two concentrations produce an immobilization of between 0 and 100% in the test population. The selection of reported EC50 values and 95% confidence intervals was based upon an examination of the data base and the results of the computer analysis. Selection criteria included the establishment of a concentration-effect relationship, the number of concentrations causing partial responses, and the span of responses bracketing the EC50 value. If two or more statistical methods produced acceptable results, then the method which yielded the smallest 95% confidence interval was selected. The No Observed Effect Concentration (NOEC), defined as the highest concentration tested at and below which there were no toxicant-related immobilization or physical and behavioral abnormalities (e.g. lethargy, flared carapace), during the 48-hour exposure period was also determined.

Validity criteria fulfilled:

yes

Conclusions:

The 48-hour EC50 (based on mean concentrations) was calculated by moving average angle analysis to be 0.1 μg/L (0.0001 mg/L). The No Observed Effect Concentration established for this study was 0.025 μg/L (0.000025 mg/L), the lowest mean measured concentration tested.

Description of key information

A study on Daphnia magna is available. The 48-hour EC50 was calculated to be 0.0001 mg/L. The No Observed Effect Concentration established for this study was 0.000025 mg/L (Collins, 1992).

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Dose descriptor:

EC50

Effect concentration:

0 mg/L

Additional information

A study was conducted on Daphnia magna according to FDA Technical Assistance Document 4.08 under GLP (Collins, 1992).

The 48-hour EC50 (based on mean concentrations) was calculated by moving average angle analysis to be 0.1 μg/L (0.0001 mg/L). The No Observed Effect Concentration established for this study was 0.025 μg/L (0.000025 mg/L), the lowest mean measured concentration tested.