Methomyl

Toxicity to other aquatic organisms

Administrative data

Endpoint:

toxicity to other aquatic vertebrates

Remarks:

amphibian Xenopus laevis, larvae: (sub)lethal effects

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2015

Report date:

2015

Materials and methods

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

other: U.S. EPA, Endocrine Disruptor Screening Program Test Guidelines, OPPTS 890.1100 Amphibian Metamorphosis (Frog) (October 2009)

Deviations:

no

GLP compliance:

yes

Test material

Test material information

Constituent 1

Reference substance name:

Methomyl

EC Number:

240-815-0

EC Name:

Methomyl

Cas Number:

16752-77-5

Molecular formula:

C5H10N2O2S

IUPAC Name:

(E)-[1-(methylsulfanyl)ethylidene]amino N-methylcarbamate

Test material form:

solid: crystalline

Specific details on test material used for the study:

Methomyl technical
DPX-X1179-571
Purity: 99.4%

Sampling and analysis

Analytical monitoring:

yes

Test solutions

Vehicle:

yes

Remarks:

water

Test organisms

Aquatic vertebrate type (other than fish):

frog

Test organisms (species):

Xenopus laevis

Study design

Test type:

flow-through

Water media type:

freshwater

Limit test:

no

Total exposure duration:

21 d

Test conditions

Hardness:

134-152 mg/L (as CaCO3)

Test temperature:

21.9 to 22.4°C

pH:

6.9 to 7.2

Dissolved oxygen:

3.6 - 6.8 mg/L

Nominal and measured concentrations:

Nominal: 0, 18.3, 56.0, 168.0 μg/L
Measured: 0, 17.0, 52.2, 186 μg/L

Details on test conditions:

The general experimental design entailed exposing tadpoles to 3 different concentrations of the test chemical (n = 4 replicates per concentration) and a dilution water control (n = 4 replicates). The primary endpoints evaluated were hind limb length, body length (snout to vent [SVL]), developmental stage, wet weight, thyroid histology, and daily mortality.

Reference substance (positive control):

no

Results and discussion

Effect concentrations

Effect concentrations 1

Key result

Duration:

21 d

Dose descriptor:

NOEC

Effect conc.:

186 µg/L

Nominal / measured:

meas. (TWA)

Remarks on result:

other: no effects at the highest dose tested

Effect concentrations 2

Key result

Duration:

21 d

Dose descriptor:

LOEC

Effect conc.:

> 186 µg/L

Nominal / measured:

meas. (TWA)

Details on results:

No statistically significant effects associated with any of the Amphibian Metamorphosis Assay endpoints were found during the present study. Mild histopathology of the thyroid glands was found in both the control and the test substance treatments and was determined by the certified pathologist to be unrelated to methomyl exposure. More specifically, the incidence rate of hypertrophy and hyperplasia was the highest in stage 61 (50% and 25%), lower in stage 62 and above (25% and 0%, 15% and 0% , and 10% and 0% at stages 62, 63, and 64, respectively), and the lowest in

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Conclusions:

21d NOEC = 186 μg/L (the highest concentration tested)
21d LOEC > 186 μg/L

Executive summary:

The effect of the test substance on the metamorphosis of the South African clawed frog, (Xenopus laevis), was assessed in a flow-through, 21-day test initiated with Nieuwkoop and Faber (3) (NF) stage 51 larvae in accordance with test guidelines (U.S. EPA, Endocrine Disruptor Screening Program Test Guidelines, OPPTS 890.1100 Amphibian Metamorphosis (Frog) (October 2009)). Nominal concentrations tested were 0, 18.3, 56.0, 168.0 μg/L. Measured concentrations were 0, 17.0, 52.2, 186 μg/L. The general experimental design entailed exposing tadpoles to 3 different concentrations of the test chemical (n = 4 replicates per concentration) and a dilution water control (n = 4 replicates). The primary endpoints evaluated were hind limb length, body length (snout to vent [SVL]), developmental stage, wet weight, thyroid histology, and daily mortality.

The test substance did not significantly alter 7-day hind-limb length (HLL) or 21-day HLL. No effect on median (NF) developmental stage was observed at 7 days or 21 days. Asynchronous development was not observed in any of the treatments. Alterations, including follicular hypertrophy, were observed in thyroid gland histopathology in the control and each test concentration, but were not considered to be test substance-related. No clinical signs of sub-lethal toxicity were observed in the definitive test. The NOEC (No Observable Effect Concentration) for the test substance in a 21-day amphibian metamorphosis assay study using South African clawed frog, Xenopus laevis, was 186 μg/L based on time-weighted, mean measured methomyl concentrations and AMA endpoints. The LOEC (lowest observed effect concentration, for the same endpoint(s) was >186 μg/L.