Methomyl (Ref: OMS 1196)

Methomyl (Ref: OMS 1196)	Last updated: 18/01/2023
(Also known as: DPX X1179)

SUMMARY

Methomyl is an oxime carbamate insecticide. It is highly soluble in water but has a low volatility and would not normally be expected to leach to groundwater. It is not normally persistent in soil or water systems. It is highly toxic to mammals and a cholinesterase inhibitor. It shows a moderate to high toxicity to most fauna and flora.

Data alerts

The following alerts are based on the data in the tables below. An absence of an alert does not imply the substance has no implications for human health, biodiversity or the environment but just that we do not have the data to form a judgement.

Environmental fate	Ecotoxicity	Human health
Environmental fate High alert: Drainflow: Mobile	Ecotoxicity High alert: Birds acute ecotoxicity: High; Fish chronic ecotoxicity: High; Daphnia acute ecotoxicity: High; Daphnia chronic ecotoxicity: High; Bees acute contact ecotoxicity: High; Bees acute oral ecotoxicity: High	Human health High alert: Mammals acute toxicity: High; Endocrine distrupter; Acetyl cholinesterase inhibitor

GENERAL INFORMATION

Description

An insecticide used to control a wide range of foliar and soil-borne insects. Also a pesticide transformation product

Example pests controlled

Lepidoptera, Coleoptera and Diptera

Example applications

Lettuce; Artichokes; Rhubarb; Orchard crops; Sod turf; Alfalfa; Sugarbeet; Cotton

Efficacy & activity

Availability status

Current

Introduction & key dates

First registered in the United States in 1968

UK regulatory status

UK COPR regulatory status

Not approved

Date COPR inclusion expires

Expired

UK LERAP status

No UK approval for use

EC Regulation 1107/2009 (repealing 91/414)

EC Regulation 1107/2009 status

Not approved

Dossier rapporteur/co-rapporteur

Belgium/Romania

Date EC 1107/2009 inclusion expires

Expired

EU Candidate for substitution (CfS)

Yes - low ADI / ARfD / AOEL

Listed in EU database

Yes

Approved for use (✓) under EC 1107/2009 in the following EU Member States

ATAustria	BEBelgium	BGBulgaria	CYCyprus	CZCzech Republic	DEGermany	DKDenmark	EEEstonia	ELGreece
		✓	✓					✓
ESSpain	FIFinland	FRFrance	HRCroatia	HUHungary	IEIreland	ITItaly	LTLithuania	LULuxembourg
✓				✓		✓
LVLatvia	MTMalta	NLNetherlands	PLPoland	PTPortugal	RORomania	SESweden	SISlovenia	SKSlovakia
	✓			✓	✓

Additional information

Also used in

Australia, USA

Chemical structure

Isomerism

Methomyl is a mixture of (Z)- and (E)-isomers. The Z-isomer is strongly favored thermodynamically.

Chemical formula

C₅H₁₀N₂O₂S

Canonical SMILES

CC(=NOC(=O)NC)SC

Isomeric SMILES

C/C(=N\OC(=O)NC)/SC

International Chemical Identifier key (InChIKey)

UHXUZOCRWCRNSJ-UHFFFAOYSA-N

International Chemical Identifier (InChI)

InChI=1S/C5H10N2O2S/c1-4(10-3)7-9-5(8)6-2/h1-3H3,(H,6,8)/b7-4+

2D structure diagram/image available?

Yes

Cambridge Crystallographic Data Centre diagrams

Common Name	Relationship	Link
methomyl	Unstated isomer
(E)-methomyl	(E)-isomer
(Z)-methomyl	(Z)-isomer

General status

Pesticide type

Insecticide, Acaricide, Metabolite

Metabolite Type

Soil, Animal, Groundwater, Surface water, Plant

Substance groups

Carbamate insecticide; Oxime carbamate insecticide; Carbamate acariicide; Oxime carbamate acaricide

Minimum active substance purity

980 g kg⁻¹

Known relevant impurities

EU dossier - None declared

Substance origin

Synthetic

Mode of action

Systemic with contact and stomach action. Cholinesterase inhibitor.

CAS RN

16752-77-5

EC number

240-815-0

CIPAC number

264

US EPA chemical code

090301

PubChem CID

5353758

CLP index number

006-045-00-2

Molecular mass

162.21

PIN (Preferred Identification Name)

IUPAC name

S-methyl (EZ)-N-(methylcarbamoyloxy)thioacetimidate

CAS name

methyl N-(((methylamino)carbonyl)oxy)ethanimidothioate

Other status information

Marine Pollutant; Chemical subject to PIC regulations; Subject to the provisions of the UK Poisons Act 1972

Relevant Environmental Water Quality Standards

Herbicide Resistance Classification (HRAC)

Not applicable

Herbicide Resistance Classification (WSSA)

Not applicable

Insecticide Resistance Classification (IRAC)

Fungicide Resistance Classification (FRAC)

Not applicable

Examples of recorded resistance

Aphis gossypii, Bemisia tabaci, Chrysoperla carnea, Earias vittella, Frankliniella occidentalis, Heliothis assulta, many more

Physical state

White crystalline solid

Can be a metabolite of:

Parent

Formation medium

Estimated maximum occurrence fraction

1107/2009 relevancy

alanycarb

Soil

Major fraction

thiodicarb

Soil

0.798

Major fraction

thiodicarb

Groundwater

Relevant

Formulations

Property

Value

Example manufacturers & suppliers of products using this active now or historically

AgroCare
Bayer CropScience
FCC

Example products using this active

Methomyl 20SC
Lannate
Lanox
Nudrin
Metofan

Formulation and application details

Often supplied as a soluble concentrate or emulsifiable concentrate. May be applied aerially in the US.

ENVIRONMENTAL FATE

Property

Value

Source; quality score; and other information

Interpretation

Solubility - In water at 20 °C (mg l⁻¹)

55000

High

Solubility - In organic solvents at 20 °C (mg l⁻¹)

97100

n-Heptane

250000

Acetone

1000000

Methanol

420000

Ethanol

Melting point (°C)

79.6

Boiling point (°C)

Decomposes before boiling

Degradation point (°C)

192

Flashpoint (°C)

Octanol-water partition coefficient at pH 7, 20 °C

1.23 X 10⁰⁰

Calculated

Log P

0.09

Low

Fat solubility of residues

Solubility

Data type

Density (g ml⁻¹)

1.32

Dissociation constant pKa) at 25 °C

Not applicable

No dissociation

Vapour pressure at 20 °C (mPa)

0.72

Low volatility

Henry's law constant at 25 °C (Pa m³ mol⁻¹)

2.13 X 10^-06

Non-volatile

Maximum UV-vis absorption L mol⁻¹ cm⁻¹

Neutral solution: 234nm = 9010
Acidic solution: 234nm = 8980
Basic solution: 234nm = 8890

Surface tension (mN m⁻¹)

73.7

at 20.1°C

Degradation

Property

Value

Source; quality score; and other information

Interpretation

General biodegradability

Soil degradation (days) (aerobic)

DT₅₀ (typical)

Non-persistent

DT₅₀ (lab at 20 °C)

6.97

Non-persistent

DT₅₀ (field)

DT₉₀ (lab at 20 °C)

25.3

Non-persistent

DT₉₀ (field)

DT₅₀ modelling endpoint

Note

EU dossier lab studies DT₅₀ range 4.6-8.6 days, DT₉₀ range 15.4-38.2 days; Other sources: DT₅₀ 30 days (DW4)

Dissipation rate RL₅₀ on plant matrix

Value

3.0

Note

Published literature RL₅₀ range 0.5-8.7 days, 8 field & undercover grown crops, various matrices, n=14

Dissipation rate RL₅₀ on and in plant matrix

Value

4.0

Note

Published literature RL₅₀ range 0.9-6.4 days, 13 field & undercover grown crops, various matrices, n=14

Aqueous photolysis DT₅₀ (days) at pH 7

Value

Stable

Note

Aqueous hydrolysis DT₅₀ (days) at 20 °C and pH 7

Value

Stable

Note

Stable pH 5 to pH 7, DT₅₀ 36 days at pH 9, all at 25 °C

Water-sediment DT₅₀ (days)

3.7

Fast

Water phase only DT₅₀ (days)

2.9

Moderately fast

Soil adsorption and mobility

Property

Value

Source; quality score; and other information

Interpretation

Linear

K_d

Mobile

K_oc

Notes and range

Freundlich

K_f

0.381

Mobile

K_foc

25.2

¹/_n

0.86

Notes and range

EU dossier K_f range 0.145-0.809 mL g⁻¹, K_foc range 13.3-42.8 mL g⁻¹, ¹/_n range 0.82-0.89, Soils=5

pH sensitivity

Fate indices

Property

Value

Source; quality score; and other information

Interpretation

GUS leaching potential index

2.19

Calculated

Transition state

SCI-GROW groundwater index (μg l⁻¹) for a 1 kg ha⁻¹ or 1 l ha⁻¹ application rate

Value

1.45 X 10^-02

Calculated

Note

Potential for particle bound transport index

Low

Calculated

Potential for loss via drain flow

Mobile

Calculated

Bio-concentration factor

BCF (l kg⁻¹)

Low risk

Based on LogP < 3

Low risk

CT₅₀ (days)

Known soil metabolites

Metabolite

Major/Minor fraction

$Click here for further information on Major/Minor fraction$

Estimated maximum occurrence fraction

Notes

methomyl oxime (Ref: IN-X1177)

Minor fraction

0.022

acetonitrile

Minor fraction

Known groundwater metabolites

None

Other known metabolites

Metabolite name and reference

Aliases

Formation medium / Rate

Estimated maximum occurrence fraction

Metabolising enzymes

acetonitrile

Rat (Blood, Liver)

acetamide

Animal; Rat

E-methyl N-[[(methylamino)carbonyl]oxy]ethanimidothioate (Ref: IN-B1884)

anti-methomyl

Animal

9-hydroxy-6-methyl-3-oxo-4-oxa-7-thia-2,5-diazadec-5-en-10-oic acid (Ref: IN-HUZ57)

hydroxy cysteine of methomyl

Plant

methyl-N-[[[(hydroxymethyl)amino]carbonyl]oxy]ethanimidothioate (Ref: IN-G6520)

hydroxy methyl methomyl

Plant

2-methyl-4-thiazolemethanol (Ref: IN-NR282)

Plant

N-acetyl-S-[1-[[[(methylamino)carbonyl]oxy]imino]ethyl]-L-cysteine

methomyl mercapturate

Rat (Urine)

ECOTOXICOLOGY

Terrestrial ecotoxicology

Property

Value

Source; quality score; and other information

Interpretation

Mammals - Acute oral LD₅₀ (mg kg⁻¹)

Rat

High

Mammals - Short term dietary NOEL

(mg kg⁻¹)

Rabbit

High

(ppm diet)

Mammals - Chronic 21d NOAEL (mg kg⁻¹ bw d⁻¹)

Birds - Acute LD₅₀ (mg kg⁻¹)

24.2

Colinus virginianus

High

Birds - Short term dietary (LC₅₀/LD₅₀)

> 518.8 mg kg bw⁻¹ day⁻¹

Colinus virginianus

Birds - Chronic 21d NOEL (mg kg⁻¹ bw d⁻¹)

Earthworms - Acute 14 day LC₅₀ (mg kg⁻¹)

Eisenia foetida

Moderate

Earthworms - Chronic NOEC, reproduction (mg kg⁻¹)

1.5

Eisenia foetida

Moderate

Soil micro-organisms

Nitrogen mineralisation: No significant adverse effect
Carbon mineralisation: No significant adverse effect

Dose: 4.5 kg ha⁻¹ 28 days

Collembola

Acute LC₅₀ (mg kg⁻¹)

Chronic NOEC (mg kg⁻¹)

Non-target plants

Honeybees (Apis spp.)

Contact acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg bee⁻¹)

0.16

Apis mellifera

High

Oral acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg bee⁻¹)

0.28

Apis mellifera

High

Unknown mode acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg bee⁻¹)

Chronic

Bumblebees (Bombus spp.)

Contact acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg bee⁻¹)

Oral acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg bee⁻¹)

> 3.3

Bombus terrestris

Moderate

Literature DT₅₀ values range 0.44-3.46 µg bee⁻¹

Mason bees (Osmia spp.)

Contact acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg bee⁻¹)

Oral acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg bee⁻¹)

Other bee species (1)

Acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg insect⁻¹)

0.14

Trigona spinipes

High

Mode of exposure

Oral

Other bee species (2)

Acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg insect⁻¹)

0.05

Nannotrigona perilampoides

High

Mode of exposure

Oral

Beneficial insects (Ladybirds)

Beneficial insects (Lacewings)

Beneficial insects (Parasitic wasps) as Mortality LR₅₀ g ha⁻¹ 48 hr

0.20

Aphidius rhopalosiphi adult

Beneficial insects (Predatory mites) as Mortality LR₅₀ g ha⁻¹ 7 day

9.1

Typhlodromus pyri protonymph

Beneficial insects (Ground beetles)

Aquatic ecotoxicology

Property

Value

Source; quality score; and other information

Interpretation

Fish - Acute 96 hour LC₅₀ (mg l⁻¹)

0.63

Lepomis macrochirus

Moderate

Fish - Chronic 21 day NOEC (mg l⁻¹)

0.076

Lepomis macrochirus

Moderate

Aquatic invertebrates - Acute 48 hour EC₅₀ (mg l⁻¹)

0.0076

Daphnia magna

High

Aquatic invertebrates - Chronic 21 day NOEC (mg l⁻¹)

0.0016

Daphnia magna

High

Aquatic crustaceans - Acute 96 hour LC₅₀ (mg l⁻¹)

0.036

Americamysis bahia

High

Sediment dwelling organisms - Acute 96 hour LC₅₀ (mg l⁻¹)

0.032

Chironomus riparius

High

Sediment dwelling organisms - Chronic 28 day NOEC, static, water (mg l⁻¹)

Sediment dwelling organisms - Chronic 28 day NOEC, sediment (mg kg⁻¹)

Aquatic plants - Acute 7 day EC₅₀, biomass (mg l⁻¹)

Algae - Acute 72 hour EC₅₀, growth (mg l⁻¹)

> 100

Selenastrum capricornutum

Low

Algae - Chronic 96 hour NOEC, growth (mg l⁻¹)

Mesocosm study data

NOEAEC mg l⁻¹

HUMAN HEALTH AND PROTECTION

General

Property

Value

Source; quality score; and other information

Interpretation

Threshold of Toxicological Concern (Cramer Class)

High (class III)

Mammals - Acute oral LD₅₀ (mg kg⁻¹)

Rat

High

Mammals - Dermal LD₅₀ (mg kg⁻¹ body weight)

2000

Rat

Mammals - Inhalation LC₅₀ (mg l⁻¹)

0.215

Rat

Other Mammal toxicity endpoints

ADI - Acceptable Daily Intake (mg kg⁻¹ bw day⁻¹)

0.0025

Rat SF=100

ARfD - Acute Reference Dose (mg kg⁻¹ bw day⁻¹)

0.0025

Rat SF=100

AAOEL - Acute Acceptable Operator Exposure Level (mg kg⁻¹ bw day⁻¹)

AOEL - Acceptable Operator Exposure Level - Systemic (mg kg⁻¹ bw day⁻¹)

0.0025

Rat SF=100

Dermal penetration studies (%)

1.2-15.0

concentration dependent

Dangerous Substances Directive 76/464

Exposure Routes

Public

No unacceptable risks to bystanders identified

Occupational

Risk of expsoure via dermal absortption
Risk of exposure acceptable under label recommendations for use for personal protection clothing and equipment

MRLs

European

EU MRL pesticide database

Great Britain

GB MRL Register

Notes

Drinking Water Standards

Drinking Water MAC (μg l⁻¹)

Mammalian dose elimination route and rate

Health issues

Specific human health issues

Carcinogen

Genotoxic

Endocrine disruptor

; ; ; ;

Reproduction / development effects

Acetyl cholinesterase inhibitor

Neurotoxicant

No data found

Respiratory tract irritant

Skin irritant

Skin sensitiser

No data found

Eye irritant

Phototoxicant

No data found

General human health issues

Possible thyroid toxicant
Endocrine issues - Weak increase of aromatase activity and estrogen production

Handling issues

Property

Value and interpretation

General

Not explosive or oxidising
IMDG Transport Code is usually 6.1
Not expected to autoignite; Not highly flammable

CLP classification 2013

Health: H300
Environment: H400, H410

WHO Classification

Ib (Highly hazardous)

UN Number

2757

Waste disposal & packaging

Packaging Group II (medium danger)

TRANSLATIONS

Language

Name

English

methomyl

French

methomyl

German

Methomyl

Danish

methomyl

Italian

metomil

Spanish

metomilo

Greek

methomyl

Polish

metomyl

Swedish

metomyl

Hungarian

metomil

Dutch

methomyl

Record last updated:	18/01/2023
Contact:	aeru@herts.ac.uk
Please cite as:	Lewis, K.A., Tzilivakis, J., Warner, D. and Green, A. (2016) An international database for pesticide risk assessments and management. Human and Ecological Risk Assessment: An International Journal, 22(4), 1050-1064. DOI: 10.1080/10807039.2015.1133242