Chlorpyrifos

Short-term toxicity to aquatic invertebrates

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

short-term toxicity to aquatic invertebrates

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 202 (Daphnia sp. Acute Immobilisation Test)

Deviations:

no

Qualifier:

according to guideline

Guideline:

EPA OPP 72-2 (Aquatic Invertebrate Acute Toxicity Test)

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method C.2 (Acute Toxicity for Daphnia)

Deviations:

no

GLP compliance:

yes

Specific details on test material used for the study:

Substance ID: TSN101285
Lot #: KC28161419
Purity: 99.8%

Analytical monitoring:

yes

Details on sampling:

Aliquots (40 mL from the ALDW control, acetone control, 77.8, 130, and 216 ng/L solutions; 20 mL from the 360, 600, and 1000 ng/L solutions) were collected from the test solutions (bulk dose solutions and controls on day 0, replicate spent test solutions as well as renewed dose solutions on day 1 and replicate spent test solutions on day 2). The samples were extracted with 1 mL iso-octane by shaking on a flatbed shaker set on low speed for 30 minutes. The biphasic mixtures were allowed to separate. For the ALDW control, acetone control, 77.8, 130, 216, 360, and 600 ng/L samples, the organic phase (top) was transferred to autosampler vials for analysis directly. For the 1000 ng/L samples, a 0.5-mL aliquot of the extract was transferred to autosampler vials containing 0.5 mL iso-octane. The solutions were capped, vortexed and analyzed by GC/ECD.

Vehicle:

yes

Remarks:

Acetone

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION
- Method: A stock solution with a nominal concentration of 1.00 mg/L was prepared by gravimetrically adding approximately 10 mg of the test material to 10 mL of acetone. The dose stock solutions were prepared as serial dilutions of the next highest dose stock solution. The bulk dose solutions were prepared by adding 0.1 mL of the 778, 1296, 2160, 3600, 6000, and 10,000 ng/L dose stock solutions, respectively, to a 1L volumetric flask and filled to volume with ALDW. The flasks were then stoppered and shaken vigorously to mix the solutions.
- Chemical name of vehicle: Acetone

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM
- Common name: Water flea
- Source: In-house cultures initially obtained Aquatic Biosystems, Fort Collins, Colorado
- Age: Less than 24-hours old
- Feeding during test: Daphnia were unfed during the test
- Feed type: Daphnia were fed a mixed diet of Selenastrum capricornutum (algae) and YCT (yeast-ceraphyll trout) trout chow five times weekly.

METHOD FOR PREPARATION AND COLLECTION OF EARLY INSTARS OR OTHER LIFE STAGES: The day before instars were needed for testing, stock tanks with Daphnia greater than 14-days old which have had at least four broods were removed from the incubator. The instars were separated from adults by gently lifting the screened insert from the 2-L stock tank, releasing instars through the nylon mesh screen while retaining the adult Daphnia. The screened insert, with adult Daphnia, were then placed in another stock tank that contained daphnid water. The original solution with instars was poured through a metal sieve into another stock tank. The instars collected on the sieve were discarded, and the original solution was poured back into the initial stock tank. The corresponding screened insert holding adult Daphnia was then put back in place. This procedure was repeated the day the study was set to cull <24-hour old instars for use in the study.

Test type:

static

Water media type:

other: Adjusted (for hardness) Laboratory Dilution Water (ALDW)

Total exposure duration:

48 h

Hardness:

Control water (ALDW): 114-140 mg/L CaCO3
1000 ng/L Bulk Solution, Nominal: 144-152 mg/L CaCO3

Test temperature:

20.0-20.9 °C (20.5 ± 0.2) Measured from the bulk dose solutions and the individual test vessels
19.5-20.2 °C (Continuous temperature monitoring range from surrogate vessel)

pH:

7.3-8.2

Dissolved oxygen:

8.5-9.2 mg/L (8.9 ± 0.2) (Percent oxygen saturation averaged 100% and remained ≥96% throughout the exposure, based on a theoretical value of 8.9 mg/L)

Conductivity:

Control water (ALDW): 409-410 µmho/cm
1000 ng/L Bulk Solution, Nominal: 405-410 µmho/cm

Nominal and measured concentrations:

Nominal: 0 (water control), 0 (acetone control), 77.8, 130, 216, 360, 600, and 1000 ng/L
Measured: <12.0 ng/L (water control), <12.0 ng/L (acetone control), 72.1, 140, 234, 387, 678, and 1063 ng/L

Details on test conditions:

TEST SYSTEM
- Test vessel: 250-mL glass beakers (test vessels were then placed in an incubator thermostated at 20 ± 1°C)
- Type: Covered to reduce evaporation
- Renewal rate of test solution: Renewal at 24 hours
- 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

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: The laboratory water was Lake Huron water supplied by the City of Midland Water Treatment Plant. The water was obtained from the upper Saginaw Bay of Lake Huron off Whitestone Point and was limed and flocculated with ferric chloride. The water was pumped to the laboratory prior to municipal treatment for human consumption. Before use in the laboratory, the water was sand-filtered, pH-adjusted with gaseous CO2, carbon-filtered, and UV-irradiated.
Daphnid water (referred to adjusted lab dilution water or ALDW or daphnid dilution water or DDW) was prepared by adjusting laboratory water to a hardness of about 170 mg/L as CaC03 before autoclaving. After adjusting hardness, the water was autoclaved at 250°F (121°C) and 18 psi for 30 minutes, cooled, and aerated for approximately 24 hours before use.
- Chlorine: <10 ppb (below LOD)
- Alkalinity: 36 mg/L CaCO3
- Conductivity: 410 µmho/cm

OTHER TEST CONDITIONS
- Adjustment of pH: Yes
- Photoperiod: 16-hour light/8-hour dark
- Light intensity: 1738-1888 Lux

EFFECT PARAMETERS MEASURED: Daphnia were observed for immobility (inability to swim within 15 seconds after gentle agitation of the test container) at 24 and 48 hours of exposure.

VEHICLE CONTROL PERFORMED: Yes

RANGE-FINDING STUDY
- A 48-hour static-renewal (renewal of test solutions at -24 hours) probe study was conducted to assess the toxicity to Daphnia. One replicate of ten Daphnia per dose level were exposed to nominal test concentrations of 0 (water control), 0 (solvent control of 0.1 mL/L acetone-dosed ALDW), 100, 500, 1000, 5000, 10000, and 50000 ng/L. Immobility was observed in 100% of the Daphnia at the 50000 ng/L dose level down through the 500 ng/L dose level following 48 hours of exposure. No immobility was observed in the 100 ng/L dose level or in the controls during the study.

Reference substance (positive control):

no

Duration:

24 h

Dose descriptor:

EC50

Effect conc.:

945 ng/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

other: immobility

Remarks on result:

other: 95% CI of 794 to >1063 ng/L

Key result

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

214 ng/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

other: immobility

Remarks on result:

other: 95% CI of 186-246 ng/L

Key result

Duration:

48 h

Dose descriptor:

NOEC

Effect conc.:

72.1 ng/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

other: immobility

Details on results:

- Immobility was observed in 65% (13/20), 15% (3/20), and 5% (1/20) of the Daphnia at 1063, 678, and 387 ng/L dose levels following 24 hours of exposure. Following 48 hours of exposure, Daphnia immobility was observed in 100% (20/20) of the Daphnia at the 1063, 678, and 387 ng/L dose levels and in 55% (11/20) and 10% (2/20) of the Daphnia at the 234 and 140 ng/L dose levels, respectively. No immobility was observed in the 72.1 ng/L dose level or in the water and acetone controls at any time during the conduct of this study.

Conclusions:

24 Hr EC50: 945 ng/L
48 Hr EC50: 214 ng/L
48 Hr NOEC: 72.1 ng/L

Executive summary:

The purpose of this study was to estimate the acute toxicity of the test substance to the daphnid (Daphnia magna), over a 48-hour static-renewal (renewal of test solutions at ~24 hours) exposure period according to the guideline OECD 202. These data were used to calculate the 24- and 48-hour EC50 values (the concentrations estimated to immobilize 50 percent of the Daphnia after 24 and 48 hours of exposure, respectively) and a 48-hour no-observed-effect concentration or NOEC.

The study was conducted with two groups of ten Daphnia exposed to nominal test concentrations of 0 (water control), 0 (carrier solvent control of 0.1 mL/L acetone-dosed control water) 77.8, 130, 216, 360, 600, and 1000 ng/L, over a 48-hour exposure period. The concentration of the test substance in the test solutions was confirmed by collecting samples on days 0 and 1 (from bulk solutions) and days 1 and 2 (from spent solutions of each replicate test vessel). The collected samples were analyzed by gas chromatography/electron capture detection (GC/ECD) and external standard quantitation. Study average percent of nominal values ranged from 92.7 to 113%. The overall average percent of nominal and standard deviation values for the entire study (n=6) were 106 ± 6.90%. The resulting mean concentrations for the study were less than the lowest level quantified of 12.0 ng/L for the water and acetone control and 72.1, 140, 234, 387, 678, and 1063 ng/L for the treatment solutions.

Observations were made at 24 and 48 hours for immobility (inability to swim within 15 seconds after gentle agitation of the test container). These data were statistically evaluated, where applicable, using mean concentrations. The resulting values are listed below:

The 24-hour EC50 value was 945 ng/L, with a 95% confidence interval of 794 to >1063 ng/L. The Probit slope at 24 hours was 5.1 with a 95% confidence interval of 2.5-7.7.

The 48-hour EC50 value was 214 ng/L, with a 95% confidence interval of 186-246 ng/L. The Probit slope at 48 hours was 7.8 with a 95% confidence interval of 4.7-11.

The 48-hour NOEC was 72.1 ng/L and was determined based on biological interpretation of the data and the highest exposure level exhibiting no Daphnia immobility.

Reference 2

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Qualifier:

no guideline followed

Principles of method if other than guideline:

The purpose of this study was to estimate the acute toxicity of the test substance in various water matrices to the daphnid (Ceriodaphnia dubia), over a 48-hour static exposure period. Observations were made daily for Mortality and sublethal effects. These data were used to calculate the 48-hour EC50 values and a 48-hour NOEC.

GLP compliance:

no

Specific details on test material used for the study:

Substance ID: AGR 273801
Purity: 99.1%

Analytical monitoring:

yes

Vehicle:

yes

Remarks:

Acetone

Test organisms (species):

Ceriodaphnia dubia

Test type:

static

Water media type:

other: Dilution Water

Total exposure duration:

48 h

Remarks on exposure duration:

Multiple studies were performed including exposure of 1) test substance in dilution water; 2) test substance in humic acid; 3) test substance in Piperonyl Butoxide (PBO); 4) test substance in local waters and; 5) test substance in CCCSD Effluent;

Test temperature:

25 ± 2°C

pH:

6.8-8.3

Dissolved oxygen:

>40% saturation after 48-h; typically measured at 0 and 48h, not determined for small sample volumes

Nominal and measured concentrations:

Definitive 1 (Test substance): 0 (control), 0 (solvent control), 3.1, 6.3, 12.5, 25, 50, and 100 ng/L
Definitive 2 (Test substance/Humic acid): 0 (control), 25, 50, 100, 200, 400 ng/L for test substance and 0 (control), 1, 2.5, 5, 10 mg/L for HA
Definitive 3 (Test substance/PBO): 0 (control), 25, 50, 100, 200, 400 ng/L for test substance and 0 (control), 125, 250, 500, 1000 µg/L for PBO
Definitive 4 (Test substance/local waters): 0 (control), 25, 50, 100, 200, and 400 ng/L
Definitive 5 (Test substance/CCCSD Effluent): 0 (control), 6.25, 12.5, 25, 50, and 100%

Reference substance (positive control):

no

Key result

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

62 ng/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mortality

Remarks on result:

other: Test substance with dilution water

Duration:

48 h

Dose descriptor:

NOEC

Effect conc.:

25 ng/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: sublethal effects

Remarks on result:

other: Test substance with dilution water

Key result

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

>= 152 - <= 263 ng/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mortality

Remarks on result:

other: Test substance with humic acid (humic acid increased the 48-h EC50 value by 2.5-4.2 fold

Duration:

48 h

Dose descriptor:

NOEC

Effect conc.:

100 ng/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: sublethal effects

Remarks on result:

other: Test substance with humic acid

Key result

Duration:

48 h

Remarks on result:

other: Test substance with PBO: At concentrations of 100-400 µg/L, PBO effectively reduced or eliminated the toxicity of the test substance

Key result

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

283 ng/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mortality

Remarks on result:

other: Test substance with local waters (toxicity reduced by 4.6-5.2 fold)

Duration:

48 h

Dose descriptor:

NOEC

Effect conc.:

200 ng/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: sublethal effects

Remarks on result:

other: Test substance with local waters

Key result

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

>= 55 - <= 71 other: %

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mortality

Remarks on result:

other: Test substance with CCCSD Effluent

Conclusions:

Test substance with dilution water: 48-h EC50: 62 ng/L; NOEC: 25 ng/L
Test substance with humic acid: 48-h EC50: 152-263 ng/L (Humic acid increased the 48-h EC50 value by 2.5-4.2 fold); NOEC: ~100 ng/L
Test substance with PBO: At concentrations of 100-400 µg/L, PBO effectively reduced or eliminated the toxicity of the test substance
Test substance with local waters: 48-h EC50: 283 ng/L (toxicity reduced by 4.6-5.2 fold); NOEC: 200 ng/L
Test substance with CCCSD Effluent: 48-h EC50: 55-71%

Executive summary:

The purpose of this study was to estimate the acute toxicity of the test substance in various water matrices to the daphnid (Ceriodaphnia dubia), over a 48-hour static exposure period. Observations were made daily for Mortality and sublethal effects.

Multiple studies were performed including exposure of

1) test substance with dilution water

2) test substance with humic acid

3) test substance with Piperonyl Butoxide (PBO)

4) test substance with local waters

5) test substance with CCCSD (Central Contra Costa County Sanitation District) Effluent

Studies were undertaken to begin to investigate the bioavailability and toxicity of the test substance to the daphnid, Ceriodaphnia dubia. Preliminary studies indicated that toxicity was decreased by the addition of a mixed algal diet to the test solutions; the 48-h EC50 value increased from 62 ng/L to >100 ng/L. Subsequent studies investigated the role that an exogenous organic carbon source, Aldrich humic acid, would have on bioavailability and toxicity. Humic acid increased the 48-h EC50 value by 2.5-4.2 fold. At a nominal humic acid concentration of 10 mg/L, the 48-h EC50 value was 263 ng/L. In locally collected river and pond waters (total organic carbon 8.2-10.8 mg/L) toxicity of the test substance was reduced by 4.6-5.2 fold; 48-h EC50 values were 283 ng/L in all waters tested.

The effect of an enzymatic inhibitor, piperonyl butoxide (PBO), was also investigated. PBO inhibits the conversion of the test substance to the active oxon moiety. At concentrations of 100-400 µg/L, PBO effectively reduced or eliminated the toxicity of the test substance, while higher PBO concentrations (500-1000 µg/L) resulted in toxicity due to PBO itself.

Overall, these studies indicated that the presence of exogenous and ambient organic carbon was able to effectively attenuate the toxicity of the test substance to the daphnid, C. dubia.

Description of key information

48-hour EC₅₀ (Daphnia magna): 214 ng/L; OECD 202, EU Method C.2, EPA 72 -2; Reliability = 1

48-hour EC₅₀(Ceriodaphnia dubia): 62 ng/L; no guideline followed; Reliability = 2

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Effect concentration:

214 ng/L

Additional information

Acute aquatic invertebrate tests were conducted in several freshwater species. The 48-h EC₅₀ value in Daphnia magna was 214 ng/L.