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

Short-term toxicity to fish

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

short-term toxicity to fish

Type of information:

experimental study

Adequacy of study:

key study

Study period:

From 15 to 19 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 4.11 (U.S. Food and Drug Administration, March 1987).

Deviations:

no

GLP compliance:

yes

Analytical monitoring:

yes

Details on sampling:

Water samples were removed and analyzed at 0 and 96 hours from both replicate vessel of each test concentration and the controls. Each exposure solution sample was collected from the approximate midpoint of the aquarium with a volumetric pipet.

Vehicle:

yes

Details on test solutions:

A primary stock solution at a concentration 5.0 mg/L was prepared by diluting 0.0533 g of nonlabeled test substance with 10 mL of acetone in a volumetric bask. A subsequent stock solution with a concentration of 1.0 mg/L was prepared by mixing 160 μL of the 5.0 mg A.I./mL stock solution with 50 μL of a 3.7 mg/L radiolabeled 3H-test substance stock solution and then diluting this mixture with 790 μL of acetone. Test solutions were prepared by adding the appropriate amount of stock to 15 L of dilution water. Two sets of replicate control aquaria were established. One set contained the same dilution water and was maintained under the same conditions as the test aquaria but contained no test substance; the other set contained the maximum amount of solvent present in any exposure solution (0.010 mL/L) and was designated the solvent control.

Test organisms (species):

Oncorhynchus mykiss (previous name: Salmo gairdneri)

Details on test organisms:

TEST ORGANISM
- Common name: rainbow trout
- Strain: Oncorhynchus mykiss
- Source: Spring Creek Trout Hatchery, Lewiston, Montana
- Age at study initiation (mean and range, SD):
- Length at study initiation (length definition, mean, range and SD): mean total length: 41 mm (range 35-53 mm)
- Weight at study initiation (mean and range, SD): mean wet weight: 0.63 g (range 0.37-1.24 g)
- Feeding during test: Fish were not fed during exposure.

ACCLIMATION
- Acclimation period: 14 days
- Acclimation conditions (same as test or not): same as test
- Type and amount of food: a dry commercial pelleted food, ad libitum
- Feeding frequency: daily except during the 48 hours prior to testing
- Health during acclimation (any mortality observed): no mortality was observed.

No additional data

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

96 h

Post exposure observation period:

None stated

Hardness:

28-30 mg/L CaCO3

Test temperature:

11-13 ℃

pH:

5.8-7.9

Dissolved oxygen:

5.9-9.4 mg/L

Salinity:

None stated

Nominal and measured concentrations:

Nominal concentration: 47, 27, 17, 10 and 6.0 μg/L
Measured concentration: 26, 13, 7.6, 2.5 and 1.9 μg/L

Details on test conditions:

TEST SYSTEM
- Test vessel: 18.9-L glass aquaria
- Material, size, headspace, fill volume: Contained 15 L of test solution. The exposure solution depth in each aquarium was 18.4 cm with a surface area of 819 cm2.
- Aeration: not aerated
- No. of organisms per vessel: 10
- No. of vessels per concentration (replicates): 2
- No. of vessels per control (replicates): 2
- No. of vessels per vehicle control (replicates): 2
- Biomass loading rate: 0.42 grams of biomass per liter of test solution

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: soft water reconstituted from deionized water
- Alkalinity: 37 mg/L
- Ca/mg ratio: 44 mg/L
- Conductivity: 130 μmhos/cm

OTHER TEST CONDITIONS
- Adjustment of pH:
- Photoperiod: 16 hours light and 8 hours darkness
- Light intensity: Light at an intensity of 30 footcandles was provided at the solution surface.

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) : All aquaria were examined after 24, 48, 72 and 96 hours of exposure as follows: mortalities were recorded, dead fish were removed, and observations of the live fish and the physical characteristics of the test solutions were recorded. Dissolved oxygen concentrations, temperature and pH were measured in the control and all test concentrations at 0, 24, 48, 72 and 96 hours.

TEST CONCENTRATIONS
- Range finding study
- Test concentrations: nominal concentration: 10, 6.0, 3.3, 2.2 and 1.3 μg/L
- Results used to determine the conditions for the definitive study: The initial range-finding test was conducted at three nominal exposure levels ranging from 10 to 0.10 μg/L of test substance. During this initial test, exposure concentrations were not analytically verified and therefore the effects observed were based on nominal treatment levels. At the completion of this range-finding test (96-hours), mortality was observed among 100% of the exposed rainbow trout in the highest treatment level (i.e., 10 μg/L, nominal). No mortalities or abnormal behavior was observed among organisms at the remaining lower treatment levels. Based on the results of this initial range-finding test, the following nominal concentrations were selected for the definitive study: 10, 6.0, 3.3, 2.2 and 1.3 μg/L test substance. Analysis of the exposure solutions at 0-hour of the initial definitive test resulted in an average measured concentration of test substance in the highest treatment level equal to 5.8 μg/L (58% of nominal). Following 96-hours of exposure to the highest test concentration (10 μg/L, nominal; 5.8 μg/L, measured) mortality of 10% was observed among the test organisms. During the same period, no mortalities or abnormal behavior was observed among rainbow trout exposed to the remaining lower treatment levels (i.e., 6.0-1.3 μg/L). Since<50% mortality was observed among organisms at the highest treatment level, this initial definitive test provided data which was not sufficient to determine the LC50 for test substance and rainbow trout. Review of the results of the preliminary range-finding test and the initial definitive study establish an apparent discrepancy between the observed responses. Since the initial definitive test concentrations were analytically confirmed to be within the expected concentration range, these data were considered reliable and used to select exposure levels for subsequent definitive testing. The exposure concentrations during the preliminary range-finding test were not analytically confirmed; therefore a dosing error would not have been detected. Based on these data the selected nominal exposure levels for the subsequent definitive test were: 47, 27, 17, 10 and 6.0 μg/L test substance.

Reference substance (positive control):

not specified

Duration:

96 h

Dose descriptor:

LC50

Effect conc.:

0.005 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

mortality (fish)

Remarks on result:

other: 95% CL: 0.0025-0.0076 mg/L

Duration:

96 h

Dose descriptor:

NOEC

Effect conc.:

0.003 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

mortality (fish)

Details on results:

Following 96 hours of exposure, mortality in the three highest treatment levels tested ranged from 100-85% (26-7.6 μg/L). During the same period, no mortality was observed in the remaining two tested concentrations, however two of the fish exposed to 2.5 μg/L were noted to exhibit darkened pigmentation at 72 hours, but this abnormality was no longer apparent at 96 hours. In addition, one fish exposed to the 1.9 μg/L treatment level was observed to exhibit darkened pigmentation and a partial loss of equilibrium at test termination. For acute exposures, the threshold of statistical significance (P<0.05) is generally limited to responses >10% and is based on criteria for acceptability in control performance. Based on SLI's experience with these species and in view of the low incidence (i.e., ≤ 10%) and the absence of corroborating observations at consecutive intervals, this observation was considered incidental and unrelated to the toxicity of test substance.

Results with reference substance (positive control):

None stated

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 a mortality of between 0 and 100% of the test organism population. The selection of reported LC50 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 (mortality), the number of concentrations causing partial responses, and the span of responses bracketing the LC50 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 mortalities or physical and behavioral abnormalities (e.g. lethargy, loss of equilibrium, darkened pigmentation) observed during the 96-hour exposure period, was also determined.

Validity criteria fulfilled:

yes

Conclusions:

The 96-hour LC50 (95% confidence interval) for rainbow trout exposed to test substance was estimated by non-linear interpolation to be 5.1 μg/L (0.0051 mg/L). The 95% confidence interval was calculated by binomial probability to be 2.5-7.6 μg/L (0.0025-0.0076 mg/L). The No Observed Effect Concentration established for this study was 2.5 μg/L (0.0025 mg/L).

Reference 2

Endpoint:

short-term toxicity to fish

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

From 03 to 07 Nov 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 4.11 (U.S. Food and Drug Administration, March 1987)

Deviations:

no

GLP compliance:

yes

Analytical monitoring:

yes

Details on sampling:

Water samples were removed and analyzed at 0- and 96-hours from each replicate vessel of each test concentration and the controls. Each exposure solution sample was collected from the approximate midpoint of the aquarium with a volumetric pipet.

Vehicle:

yes

Details on test solutions:

A test substance stock solution was prepared with the tritium radio-labeled test article by transferring the entire contents of the vial (i.e., 15.3 mg) 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 0.295 mg/mL. The stock solution used to prepare the test solutions was then prepared by dissolving 0.1048 g of non-labeled test substance with 5.8 mL of the superstock solution (0.295 mg/mL) in a 10 mL volumetric flask and brought to volume with acetone. The appropriate volume of stock solution was added to 15 L of dilution water to prepare each replicate exposure solution. Two sets of replicate control aquaria were established. One set contained the same dilution water and was maintained under the same conditions as the test aquaria but contained no test substance. The second set contained the maximum amount of solvent present in any exposure solution (0.006 mL/L) and was designated the solvent control.

Test organisms (species):

Lepomis macrochirus

Details on test organisms:

TEST ORGANISM
- Common name: Bluegill sunfish
- Strain: Lepomis macrochirus
- Source: a commercial supplier in Connecticut
- Age at study initiation (mean and range, SD):
- Length at study initiation (length definition, mean, range and SD): 39 mm (mean), range 32-45 mm
- Weight at study initiation (mean and range, SD): 0.70 g (mean), range 0.36-0.98 g
- Feeding during test: Fish were not fed during exposure.

ACCLIMATION
- Acclimation period: 14 days
- Acclimation conditions (same as test or not): same as test
- Type and amount of food: a dry commercial pelleted food, ad libitum
- Feeding frequency: daily except during the 48 hours prior to testing
- Health during acclimation (any mortality observed): no mortality was observed

No additional data

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

96 h

Post exposure observation period:

None stated

Hardness:

30-31 mg/L CaCO3

Test temperature:

18-23 ℃

pH:

7.1-7.8

Dissolved oxygen:

1.4-9.4 mg/L

Salinity:

None stated

Nominal and measured concentrations:

Nominal concentration: 60, 37, 22, 13 and 8.0 μg/L
Measured concentration: 47, 25, 12, 7.1 and 2.3 μg/L

Details on test conditions:

TEST SYSTEM
- Test vessel: 18.9-L glass aquaria
- Material, size, headspace, fill volume: 15 L test solution, the test solution depth was 18.4 cm with a surface area of 819 cm2.
- Aeration: Aeration was initiated in each test solution and the controls at 72 hours of exposure using a Supreme Dynamaster air pump and air stones. Aeration was continued until test termination.
- No. of organisms per vessel: 10
- No. of vessels per concentration (replicates): 2
- No. of vessels per control (replicates): 2
- No. of vessels per vehicle control (replicates): 2
- Biomass loading rate: 0.47 grams of biomass per liter of test solution

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: reconstituted from deionized water
- Alkalinity: 39 mg/L
- Ca/mg ratio: 54 mg/L
- Conductivity: 170 μmhos/cm

OTHER TEST CONDITIONS
- Adjustment of pH:
- Photoperiod: a photoperiod of 16 hours light and 8 hours darkness
- Light intensity: Light at an intensity of 30 footcandles was provided at the solution surface.

EFFECT PARAMETERS MEASURED (with observation intervals if applicable): During the definitive exposure, all aquaria were examined after 24, 48, 72 and 96 hours of exposure as follows: mortalities were recorded, dead fish were removed, and observations of the surviving fish and the physical characteristics of the test solutions were recorded. Dissolved oxygen concentrations, temperature and pH were measured in the controls and all test concentrations at 0, 24, 48, 72 and 96 hours.

TEST CONCENTRATIONS
- Range finding study
- Test concentrations: ranging from 940 to 9.4 μg/L
- Results used to determine the conditions for the definitive study: During this range finding test, bluegill sunfish Lepomis macrochirus were exposed under static conditions to nominal concentrations of test substance ranging from 940 to 9.4 μg/L. Following 96 hours of exposure, 100% mortality was recorded in the two highest nominal treatment levels (940 and 94 μg/L). During the same exposure period, no mortality was observed among fish exposed to the remaining concentration tested (9.4 μg/L). Based on the results of the range finding test, nominal concentrations of 60, 37, 22, 13 and 8.0 μg/L test substance were selected for the definitive study.

Reference substance (positive control):

not specified

Duration:

96 h

Dose descriptor:

LC50

Effect conc.:

0.011 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

mortality (fish)

Remarks on result:

other: 95% CL: 0.010-0.014 mg/L

Duration:

96 h

Dose descriptor:

NOEC

Effect conc.:

0.002 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

mortality (fish)

Details on results:

Following 96 hours of exposure, 100% mortality was observed in the two highest mean measured concentrations of test substance tested (47 and 25 μg/L). During the same period, mortality of 55% and 5% was observed in the 12 and 7.1 μg/L test concentrations, respectively, with sublethal effects (e.g. loss of equilibrium) observed among fish exposed to the 12 μg/L test concentration. No mortalities or sublethal effects were observed in the lowest mean measured concentration tested (2.3 μg/L test substance).

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 a mortality of between 0 and 100% of the test organism population. The selection of reported LC50 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 (mortality), the number of concentrations causing partial responses, and the span of responses bracketing the LC50 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 mortalities or physical and behavioral abnormalities (e.g. lethargy, loss of equilibrium, darkened pigmentation) observed during the 96-hour exposure period, was also determined.

Validity criteria fulfilled:

yes

Conclusions:

The 96-hour LC50 (95% confidence interval) for bluegill sunfish exposed to the test substance was calculated by probit analysis to be 11 (10-14) μg/L (0.011 mg/L (0.010-0.014 mg/L)). The No Observed Effect Concentration established for this study was 2.3 μg/L (0.0023 mg/L), the lowest mean measured concentration tested.

Description of key information

Two studies available.

The 96-hour LC50 for bluegill sunfish exposed to the test substance was calculated to be 11 μg/L. The No Observed Effect Concentration established for this study was 2.3 μg/L (Collins, 1992).

The 96-hour LC50 for rainbow trout exposed to test substance was estimated to be 5.1 μg/L. The No Observed Effect Concentration established for this study was 2.5 μg/L (Collins, 1992).

Key value for chemical safety assessment

Fresh water fish

Fresh water fish

Dose descriptor:

LC50

Effect concentration:

0.005 mg/L

Additional information

Two studies available. Both were conducted according to FDA Technical Assistance Document 4.11 under GLP (Collins, 1992). One is on bluegill sunfish, another is on rainbow trout.

The 96-hour LC50 (95% confidence interval) for rainbow trout exposed to test substance was estimated by non-linear interpolation to be 5.1 μg/L (0.0051 mg/L). The 95% confidence interval was calculated by binomial probability to be 2.5-7.6 μg/L (0.0025-0.0076 mg/L). The No Observed Effect Concentration established for this study was 2.5 μg/L (0.0025 mg/L).

The 96-hour LC50 (95% confidence interval) for bluegill sunfish exposed to the test substance was calculated by probit analysis to be 11 (10-14) μg/L (0.011 mg/L (0.010-0.014 mg/L)). The No Observed Effect Concentration established for this study was 2.3 μg/L (0.0023 mg/L), the lowest mean measured concentration tested.

The study on rainbow trout was selected as key study which used to classification due to lower LC50 value.