Methomyl

Long-term toxicity to aquatic invertebrates

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

long-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 211 (Daphnia magna Reproduction Test)

Deviations:

no

Qualifier:

according to guideline

Guideline:

EPA OPPTS 850.1300 (Daphnid Chronic Toxicity Test)

Deviations:

no

GLP compliance:

yes

Specific details on test material used for the study:

Methomyl technical
DPX-X1179-571
Purity: 99.4%

Analytical monitoring:

yes

Vehicle:

yes

Remarks:

water

Test organisms (species):

Daphnia magna

Test type:

flow-through

Water media type:

freshwater

Limit test:

no

Total exposure duration:

21 d

Hardness:

136-140 mg/L (as CaCO3)

Test temperature:

19.5 to 20.7°C

pH:

8.0-8.4

Dissolved oxygen:

≥ 8.7 mg/L

Conductivity:

325-381 µS/cm

Nominal and measured concentrations:

Nominal: 0, 0.75, 1.5, 3.0, 6.0, and 12 µg/L
Measured: 0, 0.75, 1.6, 3.0, 6.2, and 11 µg/L

Reference substance (positive control):

no

Key result

Duration:

21 d

Dose descriptor:

NOEC

Effect conc.:

1.6 µg/L

Nominal / measured:

meas. (not specified)

Key result

Duration:

21 d

Dose descriptor:

LOEC

Effect conc.:

3 µg/L

Nominal / measured:

meas. (not specified)

Basis for effect:

other: decreased survival of first generation at 6.2 and 11 µg/L. reductions in reproduction and total length at 3.0 µg/L.

Key result

Duration:

21 d

Dose descriptor:

other: MATC

Effect conc.:

2.2 µg/L

Key result

Duration:

21 d

Dose descriptor:

EC50

Effect conc.:

5.48 µg/L

Nominal / measured:

meas. (not specified)

Basis for effect:

mortality

Key result

Duration:

21 d

Dose descriptor:

EC50

Effect conc.:

4.92 µg/L

Nominal / measured:

meas. (not specified)

Basis for effect:

other: mean number of neonates per adult at test start

Key result

Duration:

21 d

Dose descriptor:

EC50

Effect conc.:

8.98 µg/L

Nominal / measured:

meas. (not specified)

Basis for effect:

other: mean number of neonates per reproduction day

Validity criteria fulfilled:

yes

Conclusions:

21-day NOEC = 1.6 µg/L
21-day LOEC = 3.0 µg/L
21-day MATC = 2.2 µg/L

Executive summary:

The objective of this study was to determine the effects of methomyl on the survival, growth and reproduction of the cladoceran, Daphnia magna, during a 21-day exposure period under flow-through test conditions. The test was conducted according to OECD guideline 211 and EPA OPPTS guideline 850.1300 (draft). Daphnids were exposed to a geometric series of five test concentrations and a negative (dilution water) control. Nominal test concentrations selected for the test were 0.75, 1.5, 3.0, 6.0 and 12µg/L. Measured concentrations were 0.75, 1.6, 3.0, 6.2, and 11 µg/L. Two replicate test chambers were maintained in each treatment and control group. Two test compartments were maintained in each test chamber for the treatment and control group, with five neonate daphnids in each compartment, for a total of 20 daphnids per test concentration. First-generation daphnids were observed daily during the test for immobility, the onset of reproduction, and clinical signs of toxicity. Following the onset of reproduction, the numbers of second-generation daphnids were counted approximately three times per week (e.g., Monday, Wednesday and Friday), and at test termination (Day 21). Body lengths and dry weights of the surviving first-generation daphnids were measured at the end of the test (Day 21).

Significant reductions in survival of the first generation daphnid were noted in the 6.2 and 11 μg/L and in reproduction and total length in the 3.0 μg/L treatment level. Consequently, the NOEC was 1.6 μg/L and the LOEC was 3.0 μg/L. The MATC was estimated to be 2.2 μg/L. The 21-day EC50 for survival was 5.48 µg/L. the 21-day EC50 for mean number of neonates per reproductive day was 8.98 µg/L. The 21-day EC50 for mean number of neonates per adult at test start was 4.92 µg/L.

Reference 2

Endpoint:

long-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 test procedures were based upon the “Proposed Standard Practice for Conducting Daphnia magna Renewal Chronic Toxicity Tests” currently under development by Committee E-47 of the American Society for Testing and Materials (Draft No. 8, February 1981).

GLP compliance:

no

Specific details on test material used for the study:

Methomyl technical
Purity: >99%

Analytical monitoring:

yes

Vehicle:

yes

Remarks:

water

Test organisms (species):

Daphnia magna

Test type:

other: static renewal

Water media type:

freshwater

Limit test:

no

Total exposure duration:

21 d

Hardness:

92.8 mg/L (as CaCO3)

Test temperature:

20°C

pH:

fresh test solution: 7.1-8.6
old test solution: 6.2-7.7

Dissolved oxygen:

fresh test solution: 7.4 ppm
old test solution: 4.2-5.4

Conductivity:

216 µmhos

Nominal and measured concentrations:

Nominal: 0, 0.4, 0.8, 1.6, 3.1, 6.2 and 12.5 µg/L
Measured: 0, 0.7, 1.0, 1.6, 3.5, 7.5 and 13.8 µg/L

Reference substance (positive control):

no

Key result

Duration:

21 d

Dose descriptor:

other: MATC

Effect conc.:

> 1.6 - < 3.5 µg/L

Nominal / measured:

meas. (not specified)

Basis for effect:

reproduction

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

28.7 µg/L

Basis for effect:

mortality

Details on results:

In the rangefinding study, the 48-hour LC50 was estimated to be 28.7 µg/L.

In the 21-day chronic test, the test substance did not affect daphnid survival and growth; however, a statistically significant effect was observed on reproduction. Based on the reproductive effect, the maximum acceptable toxicant concentration for Daphnia magna exposed for 21 days to the test substance was estimated to be > 1.6 but < 3.1 µg/L (nominal) or >1.6 and < 3.5 µg/L (measured).

All reproductive parameters investigated showed significant reductions. These included: reduced number of young at 3.1, 6.3, and 12.5 µg/L; reduced number of young/adult reproductive day at 6.3 µg/L and first day of reproduction was significantly delayed at 0.8, 1.6, 3.1, 6.2, and 12.5 µg/L. However this delay in first day of reproduction, while significant by LSD, was not felt to be biologically significant except at 3.1, 6.3, and 12.5 µg/L, where the delay affected number of young produced.

Validity criteria fulfilled:

yes

Conclusions:

21-day MATC (Daphnia magna) was estimated to be > 1.6 but < 3.5 µg/L (measured).

Executive summary:

Daphnia magna were exposed for 21 days under static renewal conditions to nominal concentration of the test substance ranging from 0.4 to 12 µg/L. The test material’s effect on daphnid survival, growth and reproduction was assessed. The 48-hour LC50 was estimated to be 28.7 µg/L. In the 21-day chronic test, the test substance did not affect daphnid survival and growth; however, a statistically significant effect was observed on reproduction. Based on the reproductive effect, the maximum acceptable toxicant concentration for Daphnia magna exposed for 21 days to the test substance was estimated to be > 1.6 but < 3.1 µg/L (nominal) or >1.6 and < 3.5 µg/L (measured). 

Reference 3

Endpoint:

long-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

EPA OPP 72-4 (Fish Early Life-Stage and Aquatic Invertebrate Life-Cycle Studies)

Deviations:

no

GLP compliance:

yes

Specific details on test material used for the study:

Methomyl technical
DPX-X1179-512
Purity: 98.6%

Analytical monitoring:

yes

Vehicle:

yes

Remarks:

water

Test organisms (species):

Americamysis bahia (previous name: Mysidopsis bahia)

Test type:

flow-through

Water media type:

saltwater

Limit test:

no

Total exposure duration:

28 d

Test temperature:

23.1 - 26.6°C

pH:

7.7-8.1

Dissolved oxygen:

7.3 to 8.3

Salinity:

13-16 ppt

Nominal and measured concentrations:

Nominal: 0, 0.017, 0.033, 0.063, 0.13 and 0.25 mg/L
Measured: 0, 0.0145, 0.0291, 0.0591, 0.121, and 0.253 mg/L

Reference substance (positive control):

no

Key result

Duration:

28 d

Dose descriptor:

NOEC

Effect conc.:

0.029 mg/L

Nominal / measured:

meas. (not specified)

Key result

Duration:

28 d

Dose descriptor:

LOEC

Effect conc.:

0.059 mg/L

Nominal / measured:

meas. (not specified)

Key result

Duration:

28 d

Dose descriptor:

other: MATC

Effect conc.:

0.042 mg/L

Nominal / measured:

meas. (not specified)

Key result

Duration:

28 d

Dose descriptor:

EC50

Effect conc.:

0.131 mg/L

Nominal / measured:

meas. (not specified)

Basis for effect:

immobilisation

Details on results:

Control survival at the end of the test was 83% in each replicate. Offspring production averaged 3.9 young per female in the A replicate and 5.3 young per female in the B replicate based upon 10 female mysids per replicate test chamber. No sublethal effects other than growth and reproductive effects were noted during the test except for three mysids exposed to 0.121 mg/L that were swimming erratically on day 7. Since this effect occurred only in this replicate on this one day, it was not believed to be significant.

The 7-day EC50 for immobility was 0.153 mg/L with 95% confidence limits of 0.121 to 0.253 mg/L. The 14-day EC50 for immobility was 0.147 mg/L with 95% confidence limits of 0.121 to 0.253 mg/L. The 21-day EC50 for immobility was 0.141 mg/L with 95% confidence limits of 0.121 to 0.253 mg/L. The 28-day EC50 for immobility was 0.131 mg/L with 95% confidence limits of 0.0591 to 0.253 mg/L.

Validity criteria fulfilled:

yes

Conclusions:

28-day NOEC = 0.0291 mg/L
28-day LOEC = 0.0591 mg/L
28-day MATC = 0.0415 mg/L
28-day EC50 (immobility) = 0.131 mg/L

Executive summary:

The chronic toxicity of the test substance to the mysid, Americamysis bahia, was tested according to EPA OPP 72-4. The test was performed under flow-through, unaerated conditions at 25±2°C. The dilution water was natural seawater collected from the Atlantic Ocean in Marblehead, Massachusetts and diluted to a salinity of 13 to 16 parts per thousand with deionized water. Juvenile mysids used in the test were obtained from an in-house culture (the original culture was from Aquatic BioSystems, Inc., Fort Collins, Colorado). Mysids were less than 24 hours old and in good condition at the beginning of the study.

 

Nominal methomyl technical concentrations were 0 (control), 0.017, 0.033, 0.063, 0.13 and 0.25 mg/L. Mean measured methomyl concentrations were ND (not detected at or above the limit of detection, 0.005 mg/L; control), 0.0145, 0.0291, 0.0591, 0.121, and 0.253 mg/L which represented recoveries of 85, 88, 94, 93 and 101%, respectively. Mean measured methomyl concentrations were used to calculate the no observed effect concentration (NOEC), lowest observed effect concentration (LOEC) and maximum acceptable toxicant concentration (MATC).

 

Biological parameters evaluated were survival of first generation mysids, sublethal effects including reproduction and the total length, wet weight and dry weight of surviving first generation mysids. The most sensitive measure of toxicity determined by statistical analysis of survival, growth and reproductive data was the number of young per surviving female. The NOEC was 0.0291, the LOEC 0.0591 and the MATC 0.0415 mg/L.

Reference 4

Endpoint:

long-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 211 (Daphnia magna Reproduction Test)

Deviations:

no

Qualifier:

according to guideline

Guideline:

EPA OPPTS 850.1300 (Daphnid Chronic Toxicity Test)

Deviations:

no

GLP compliance:

yes

Specific details on test material used for the study:

Methomyl technical
DPX-X1179-571
Purity: 99.4%

Analytical monitoring:

yes

Vehicle:

yes

Remarks:

water

Test organisms (species):

Daphnia magna

Test type:

flow-through

Water media type:

freshwater

Limit test:

no

Total exposure duration:

3 d

Post exposure observation period:

Daphnids were exposed for 3 days and observed through test day 21

Hardness:

136-140 mg/L (as CaCO3)

Test temperature:

20.0 to 20.7°C

pH:

8.1 to 8.4

Dissolved oxygen:

≥ 8.5 mg/L

Conductivity:

322-380 µS/cm

Nominal and measured concentrations:

Nominal: 0, 12 µg/L
Measured: 0, 11 µg/L

Details on test conditions:

At the end of the three days exposure, daphnids were returned to the test chamber with dilution water only until the end of the test (21 days).

Reference substance (positive control):

no

Key result

Duration:

3 d

Dose descriptor:

NOEC

Effect conc.:

11 µg/L

Nominal / measured:

meas. (not specified)

Basis for effect:

mortality

Remarks:

no reduction in survival in any of the three age groups

Key result

Duration:

3 d

Dose descriptor:

LOEC

Effect conc.:

11 µg/L

Nominal / measured:

meas. (not specified)

Basis for effect:

other: length

Remarks:

Reduction in length noted in the 3-day age treatment group

Key result

Duration:

3 d

Dose descriptor:

LOEC

Effect conc.:

11 µg/L

Nominal / measured:

meas. (not specified)

Basis for effect:

other: dry weight

Remarks:

reductino in dry weight in the 17-day treatment group

Key result

Duration:

3 d

Dose descriptor:

LOEC

Effect conc.:

11 µg/L

Nominal / measured:

meas. (not specified)

Basis for effect:

reproduction

Remarks:

significant reductions in reproduction in the 3 and 10-day age treatments

Details on results:

No statistically significant reductions in survival were noted in any of the three age groups exposed to 11 μg a.s./L for 72 hours. Statistically significant reductions in reproduction were noted in the 3 and 10-day age treatment groups. A statistically significant reduction was noted in total length in the 3-day age treatment group and in dry weight in the 17-day age treatment group. The results suggest that the brief exposure (72 hours) of daphnids of different ages (3, 10 or 17-days of age at exposure initiation) to methomyl had no statistically significant impact on their survival at the end of the 21-day test. However, the exposure of the organisms early on in their life stage (3 or 10 days of age) had an adverse impact on their growth and/or reproduction.

Validity criteria fulfilled:

yes

Conclusions:

No statistically significant reductions in survival were noted in any of the three age groups exposed to 11 μg a.s./L for 72 hours. Statistically significant reductions in reproduction were noted in the 3 and 10-day age treatment groups. A statistically significant reduction was noted in total length in the 3-day age treatment group and in dry weight in the 17-day age treatment group. The results suggest that the brief exposure (72 hours) of daphnids of different ages (3, 10 or 17-days of age at exposure initiation) to methomyl had no statistically significant impact on their survival at the end of the 21-day test. However, the exposure of the organisms early on in their life stage (3 or 10 days of age) had an adverse impact on their growth and/or reproduction.

Executive summary:

Daphnids were exposed to a single test concentration and a negative (dilution water) control for three days under flow-through conditions, with effects on reproduction evaluated in each age group through 21 days of age. The nominal test concentration selected for the test was 12 μg active substance (a.s.)/L. Two replicate test chambers were tested for each age group of the treatment and the control group. Each replicate contained two compartments with five daphnids, resulting in a total of 20 daphnids in each age group treatment and control. Daphnids from each age group were maintained in the test chambers with dilution water only until they reached the appropriate age (i.e. 3, 10 and 17 days old) when they were exposed to the test substance for three days. At the end of the three days exposure, daphnids were returned to the test chamber with dilution water only until the end of the test (21 days). Mean measured test concentrations were determined from samples of test water collected from the control group and from the 3, 10 and 17 days age groups on Days 6, 13 and 20, respectively. At test initiation, neonate daphnids were impartially assigned to exposure chambers. First-generation daphnids were observed daily during the test for immobility, the onset of reproduction, and clinical signs of toxicity. Following the onset of reproduction, the numbers of second-generation daphnids were counted three times per week (e.g., Monday, Wednesday and Friday), and at test termination (Day 21). Body lengths and dry weights of the surviving first-generation daphnids were measured at the end of the exposure period.

 

No statistically significant reductions in survival were noted in any of the three age groups exposed to 11 μg a.s./L for 72 hours. Statistically significant reductions in reproduction were noted in the 3 and 10-day age treatment groups. A statistically significant reduction was noted in total length in the 3-day age treatment group and in dry weight in the 17-day age treatment group. The results suggest that the brief exposure (72 hours) of daphnids of different ages (3, 10 or 17-days of age at exposure initiation) to methomyl had no statistically significant impact on their survival at the end of the 21-day test. However, the exposure of the organisms early on in their life stage (3 or 10 days of age) had an adverse impact on their growth and/or reproduction.

Description of key information

Duration/Value Type	Species	Value	Guideline	Reliability
21-day NOEC	Daphnia magna	1.6 µg/L	OECD 211, EPA OPPTS 1850.1300	1
21-day MATC	Daphnia magna	> 1.6 but < 3.5 µg/L	Proposed Standard Practice for Conducting Daphnia magna Renewal Chronic Toxicity Tests” currently under development by Committee E-47 of the American Society for Testing and Materials (Draft No. 8, February 1981).	2
28-day NOEC	Mysid	0.0291 mg/L	EPA OPP 72-4	1
3-day NOEC	Daphnia magna	11 µg/L	OECD 211, EPA OPPTS 1850.1300	1

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Effect concentration:

1.6 µg/L

Marine water invertebrates

Marine water invertebrates

Effect concentration:

0.029 mg/L

Additional information

The NOEC from the 21-d chronic aquatic invertebrate toxicity test in Daphnia magna is 1.6 µg/L, based on significant reductions in survival of the first generation daphnid, and in reproduction and total length. Brief exposure (72 hours) of daphnids of different ages (3, 10 or 17-days of age at exposure initiation) to the test substance had no statistically significant impact on their survival at the end of the 21-day test. However, the exposure of the organisms early on in their life stage (3 or 10 days of age) had an adverse impact on their growth and/or reproduction. The marine species, mysid, was less sensitive than the freshwater species with the chronic NOEC for aquatic invertebrates of 0.029 mg/L.