Dimethoate (Ref: OMS 94)

Dimethoate (Ref: OMS 94)	Last updated: 14/12/2024
(Also known as: phosphamide; fosamid; OMS 111; ENT 24650)

SUMMARY

Dimethoate is an organophosphate insecticide. It is highly soluble in water, has low groundwater leaching potential and is volatile. It is non-persistent in soil, mobile but does not normally persist in aerobic aquatic systems. It is moderately toxic to mammals but may have serious health implications for humans as it is an acetyl cholinesterase inhibitor and may cause reproduction or development effects. It is highly toxic to birds and honeybees, moderately toxic to most aquatic species and earthworms.

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; Birds chronic ecotoxicity: High; Bees acute contact ecotoxicity: High; Bees acute oral ecotoxicity: High	Human health High alert: Mammals chronic toxicity: High; Acetyl cholinesterase inhibitor

GENERAL INFORMATION

Description

An insecticide and acaricide used to control a wide range of pests including Aphididae, Coleoptera and Lepidoptera. Also a pesticide transformation product.

Example pests controlled

Aphids; Thrips; Whiteflies; Leaf & plant hoppers; Fruit flies; Grasshoppers; Jassids; Spidermites

Example applications

Fruit including apples, pears, citrus; Alfalfa; Corn; Cotton; Pecans; Safflower; Sorghum; Soybean; Sugarbeet; Turnips; Beetroot; Tobacco; Cereals including wheat, rye, triticale

Efficacy & activity

Established for many years. Tested in a wide range of field trials that have demonstrated efficacy.

Availability status

Current

Introduction & key dates

1951, first reported

GB regulatory status

GB COPR regulatory status

Not approved

Date COPR inclusion expires

Expired

GB LERAP status

Possible - check label

EC Regulation 1107/2009 (repealing 91/414)

EC Regulation 1107/2009 status

Not approved

Dossier rapporteur/co-rapporteur

Italy/Bulgaria

Date EC 1107/2009 inclusion expires

Expired

EU Candidate for substitution (CfS)

Not applicable

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

Approved for use (✓) under EC 1107/2009 by Mutual Recognition of Authorisation and/or national regulations in the following EEA countries

ISIceland	NONorway

Additional information

Also used in

Australia, Morocco

Chemical structure

Isomerism

None

Chemical formula

C₅H₁₂NO₃PS₂

Canonical SMILES

CNC(=O)CSP(=S)(OC)OC

Isomeric SMILES

No data

International Chemical Identifier key (InChIKey)

MCWXGJITAZMZEV-UHFFFAOYSA-N

International Chemical Identifier (InChI)

InChI=1S/C5H12NO3PS2/c1-6-5(7)4-12-10(11,8-2)9-3/h4H2,1-3H3,(H,6,7)

2D structure diagram/image available?

Yes

Cambridge Crystallographic Data Centre diagrams

Common Name	Relationship	Link
dimethoate	-

General status

Pesticide type

Insecticide, Acaricide, Metabolite

Metabolite Type

Soil

Substance groups

Organophosphate insecticide; Organophosphate acaricide; Organothiophosphate insecticide; Organothiophosphate acaricide

Minimum active substance purity

970 g kg⁻¹

Known relevant impurities

EU dossier - omethoate <2g kg⁻¹, isodimethoate <3g kg⁻¹

Substance origin

Synthetic

Mode of action

Systemic with contact and stomach action. Acetylcholinesterase (AChE) inhibitor.

CAS RN

60-51-5

EC number

200-480-3

CIPAC number

US EPA chemical code

035001

PubChem CID

3082

CLP index number

015-051-00-4

Molecular mass

229.26

PIN (Preferred Identification Name)

O,O-dimethyl S-[2-(methylamino)-2-oxoethyl] phosphorodithioate

IUPAC name

2-dimethoxyphosphinothioylthio-N-methylacetamide

CAS name

O,O-dimethyl S-(2-(methylamino)-2-oxoethyl) phosphorodithioate

Other status information

Potential groundwater contaminant; Severe Marine Pollutant

Relevant Environmental Water Quality Standards

UK Statutory standard for the protection of aquatic life in inland waters, coastal and territorial waters: 1 µg l⁻¹ as annual average
UK statutory standard for surface water quality: 'Good' for freshwater, transitional and coastal waters 0.48 µg l⁻¹, 4.0 µg l⁻¹ 95th percentile

Herbicide Resistance Class (HRAC MoA class)

Not applicable

Herbicide Resistance Class (WSSA MoA class)

Not applicable

Insecticide Resistance Class (IRAC MoA class)

Fungicide Resistance Class (FRAC MOA class)

Not applicable

Examples of recorded resistance

Amblyseius psuedolongispinosus, Aphis gossypii, Culex pipiens pallens, Myzus persicae, many others

Physical state

Grey to white coloured crystals with slight foul odour

Can be a metabolite of:

Parent

Formation medium

Estimated maximum occurrence fraction

1107/2009 relevancy

formothion

Soil

0.700

Major fraction

Formulations

Property

Value

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

BASF
Headland
American Cyanamide
Sumitomo
FBC
Boehringer
Nutrien Ag Solutions Ltd

Example products using this active

Dimethoate 40
Danadim
Danadim Progress
Cygon
Rogor
Roxion
Dimate
Genfarm Dimethoate

Formulation and application details

Often supplied as an emulsion concentrate, wettable powder or as a dustable powder

ENVIRONMENTAL FATE

Property

Value

Source; quality score; and other information

Interpretation

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

25900

High

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

313000

Xylene

1030000

Toluene

295

n-Hexane

1590000

Methanol

Melting point (°C)

50.5

Boiling point (°C)

Decomposes before boiling

Degradation point (°C)

113

Flashpoint (°C)

350

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

5.62 X 10⁰⁰

Calculated

Log P

0.75

Low

Fat solubility of residues

Solubility

Insoluble

Data type

Regulatory data

Density (g ml⁻¹)

1.31

Dissociation constant pKa) at 25 °C

Not applicable

No dissociation

Vapour pressure at 20 °C (mPa)

2.5

Low volatility. If applied directly to plants or soil, drift is a concern & mitigation is advisable

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

1.42 X 10^-06

Non-volatile

Volatilisation as max % of applied dose lost

From plant surface

13.8

24 hr

Volatilisation is not considered critical for air pollution

From soil surface

1.3

24 hr

Volatilisation is not considered critical for air pollution

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

Neutral soln: No maxima observed above 200 nm
Acid soln: 207.nm=5405
Basic soln: 226.5nm=3175.6

Surface tension (mN m⁻¹)

69.5

Degradation

Property

Value

Source; quality score; and other information

Interpretation

General biodegradability

Not readily biodegradable

Soil degradation (days) (aerobic)

DT₅₀ (typical)

2.5

Non-persistent

DT₅₀ (lab at 20 °C)

2.5

Non-persistent

DT₅₀ (field)

7.2

Non-persistent

DT₉₀ (lab at 20 °C)

9.6

Non-persistent

DT₉₀ (field)

DT₅₀ modelling endpoint

2.8

normalised geometric mean

Note

EU 2017 dossiers range Lab studies DT₅₀ range 2.1-4.3 days, DT₉₀ range 7.8–14.1 days, soils=4; Field studies range 4.6-9.8 days

Dissipation rate RL₅₀ (days) on plant matrix

Value

3.7

Note

Published literature RL₅₀ range 0.9-6.2 days, 20 field & undercover grown crops, various matrices, n=28

Dissipation rate RL₅₀ (days) on and in plant matrix

Value

4.6

Note

Published literature RL₅₀ range 0.9-11.2 days, 32 field & undercover grown crops, various matrices, n=40

Aqueous photolysis DT₅₀ (days) at pH 7

Value

175

Stable

Note

Not a significant degradation route

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

Value

Moderately persistent

Note

pH sensitive: DT₅₀ 158 days at pH 5, 4.4 days at pH 9, all at 25 °C

Water-sediment DT₅₀ (days)

15.5

Fast

Water phase only DT₅₀ (days)

12.6

Moderately fast

Sediment phase only DT₅₀ (days)

Air degradation

As this parameter is not normally measured directly, a surrogate measure is used: ‘Photochemical oxidative DT₅₀’. Where data is available, this can be found in the Fate Indices section below.

Decay in stored produce DT₅₀

[Milled, toasted maize flour (gofio): 41 days @ dark, ambient conditions; Field study], [Milled, toasted wheat flour (gofio): 33 days @ dark, ambient conditions; Field study]

Soil adsorption and mobility

Property

Value

Source; quality score; and other information

Interpretation

Linear

K_d (mL g⁻¹)

K_oc (mL g⁻¹)

Notes and range

Freundlich

K_f (mL g⁻¹)

0.36

Mobile

K_foc (mL g⁻¹)

28.3

¹/_n

1.014

Notes and range

EU dossier K_f range 0.25-0.42 mL g⁻¹, K_foc range 16.3-51.9 mL g⁻¹, ¹/_n range 0.965-1.05, Soils=6

pH sensitivity

Fate indices

Property

Value

Source; quality score; and other information

Interpretation

GUS leaching potential index

2.18

Calculated

Transition state

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

Value

1.69 X 10^-02

Calculated

Note

Potential for particle bound transport index

Low

Calculated

Potential for loss via drain flow

Mobile

Calculated

Photochemical oxidative DT₅₀ (hrs) as indicator of long-range air transport risk

1.6

Calculated using the Atkinson method. Assumed 1.5E+06 OH/cm³, 12 hr

Below the level of concern for long-range air transport

Bio-concentration factor

BCF (l kg⁻¹)

Whole body (Other literature Log BCF range -0.5-2.1 ())

Low potential

CT₅₀ (days)

Not available

Known soil metabolites

Metabolite

Major/Minor fraction

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

Estimated maximum occurrence fraction

Notes

omethoate (Ref: ENT 25776)

Major fraction

0.154

Bare ground, California

O-desmethyl dimethoate

Minor fraction

0.043

O,O-dimethylthiophosphoric acid

Dark

Known groundwater metabolites

None

Other known metabolites

Metabolite name and reference

Aliases

Formation medium / Rate

Estimated maximum occurrence fraction

O-desmethyl dimethoate

dimethoate metabolite X

Water; Plant

Water=0.663

O,O-dimethylthiophosphoric acid

Water; Plant

O-desmethyl omethoate carboxylic acid

dimethoate metabolite XX

Plant

O-desmethylisodimethoate

dimethoate metabolite XII

Plant

hydroxydimethoate

dimethoate metabolite V

Plant

O-desmethyl-N-desmethyl omethoate

dimethoate metabolite XXIII

Plant

dimethoate carboxylic acid

dimethoate metabolite III

Rat

O-desmethyl omethoate
Note: Weak cholinesterase inhibitor

dimethoate metabolite XI

Plant

O,O-dimethyl dithiophosphoric acid

dimethoate metabolite XV

Plant

ECOTOXICOLOGY

Terrestrial ecotoxicology

Property

Value

Source; quality score; and other information

Interpretation

Mammals - Acute oral LD₅₀ (mg kg⁻¹)

245

Rat

Moderate

Mammals - Short term dietary NOEL

(mg kg⁻¹)

0.18

Dog 1 yr

High

(ppm diet)

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

1.2

Rat Reproductive NOAEL

High

Birds - Acute LD₅₀ (mg kg⁻¹)

10.5

Colinus virginianus

High

Birds - Short term dietary (LC₅₀/LD₅₀)

14.8 mg/kq bw/day

Colinus virginianus

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

Colinus virginianus NOEL

High

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

Eisenia foetida

Moderate

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

2.87

Eisenia foetida 56 day

Moderate

Soil micro-organisms

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

Dose: 8.0 mg kg⁻¹ soil

Collembola

Acute LC₅₀ (mg kg⁻¹)

13.0

Folsomia candida 14 day

Chronic NOEC (mg kg⁻¹)

8.1

Folsomia candida

Non-target plants

1800

Carrot Cabbage Pea Sunflower Oats Onion
Vegetative vigour, ER₅₀
as g ha⁻¹

Honeybees (Apis spp.)

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

0.1

Apis mellifera

High

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

0.1

Apis mellifera

High

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

Chronic as 10-day LDD₅₀ µg bee⁻¹ day⁻¹

0.015

Apis mellifera

Notes

[The residual time to 25% mortality (RT25) value for honeybees is 104 hrs (range 72-120 hrs) - USEPA data]; [USEPA LD50 contact reported as 0.0098 ug/bee, oral reported as 0.056 ug/bee]

Bumblebees (Bombus spp.)

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

> 0.94

Bombus terrestris 72 hr

High

Literature DT₅₀ values range 0.94-5.6 µg bee⁻¹

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

> 0.33

Bombus terrestris 72 hr

High

Literature DT₅₀ values range 0.33-4.7 µg bee⁻¹

Mason bees (Osmia spp.)

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

1.02

Osmia lignaria

Moderate

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

0.25

Osmia lignaria

High

Other bee species (1)

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

0.0009

Megachile rotundata

High

Mode of exposure

Contact

Other bee species (2)

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

0.0021

Nomia melanderi

High

Mode of exposure

Contact

Beneficial insects (Ladybirds) as Mortality LC₅₀ mg l⁻¹

> 2.34

Coccinella septempunctata Adult

Beneficial insects (Lacewings) as % Mortality at dose 1.5 g ha⁻¹

3.0

Chrysoperla carnea Larva

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

0.014

Aphidius rhopalosiphi

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

2.24

Typhlodromus pyri Adult

Beneficial insects (Ground beetles)

Aquatic ecotoxicology

Property

Value

Source; quality score; and other information

Interpretation

Temperate Freshwater Fish - Acute 96 hour LC₅₀ (mg l⁻¹)

30.2

Oncorhynchus mykiss

Moderate

Temperate Freshwater Fish - Chronic 21 day NOEC (mg l⁻¹)

0.4

Oncorhynchus mykiss

Moderate

Tropical Freshwater Fish - Acute 96 hour LC₅₀ (mg l⁻¹)

0.021

Danio rerio Fingerlings

High

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

Daphnia magna

Moderate

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

0.04

Daphnia magna

Moderate

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

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

15.0

Americamysis bahia

Moderate

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

0.00129

Chironomus dilutus

High

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

0.08

Chironomus riparius EC05

Moderate

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)

90.4

Raphidocelis subcapitata

Low

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

Unknown species

Low

Mesocosm study data

NOEAEC mg l⁻¹

Marine bivalves

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)

245

Rat

Moderate

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

2000

Rat

Mammals - Inhalation LC₅₀ (mg l⁻¹)

1.68

Rat 4 hr (whole body)

Other Mammal toxicity endpoints

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

None allocated

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

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

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

None allocated

Dermal penetration studies (%)

0.09-2.0

concentration dependent

Dangerous Substances Directive 76/464

List I; List II

Exposure Routes

Public

No unacceptable risks to bystanders identified
Possible dietary exposure but this is mitigated by the MRLs

Occupational

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

Non-statutory WHO drinking water guideline 0.006 mg l⁻¹

UK EA QS database 2018

Drinking Water MAC (μg l⁻¹)

Mammalian dose elimination route and rate

Rapidly excreted predominately via urine as as parent substance, limited metabolism

Health issues

Specific human health issues

Carcinogen

Genotoxic

Endocrine disruptor

; ; ; ;

Reproduction / development effects

Acetyl cholinesterase inhibitor

Neurotoxicant

Respiratory tract irritant

Skin irritant

Skin sensitiser

Eye irritant

Phototoxicant

No data found

General human health issues

Highly toxic, harmful if swallowed
US EPA - Possible human carcinogen; CLP data - no evidence of carcinogenicity
Endocrine issues - Disruption of thyroid hormones action
Possible liver toxicant
Some evidence of neurotoxicity but not conclusive

Handling issues

Property

Value and interpretation

General

Not explosive or oxidising
IMDG Transport Hazard Class 9

CLP classification 2013

Health: H302, H312
Environment: H410
Handling, H242

WHO Classification

II (Moderately hazardous)

UN Number

UN3077

Waste disposal & packaging

Packaging Group III (minor danger)

Shelf-life, storage, stability and reactivity

Chemically stable under standard ambient conditions

TRANSLATIONS

Language

Name

English

dimethoate

French

dimethoate

German

Dimethoat

Danish

dimethoat

Italian

dimetoato

Spanish

dimetoato

Greek

dimethoate

Polish

dimetoat

Swedish

dimetoat

Hungarian

dimetoat

Dutch

dimethoat

Norwegian

Record last updated:	14/12/2024
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