Methyl isothiocyanate (Ref: SN-32866)

Methyl isothiocyanate (Ref: SN-32866)	Last updated: 30/10/2025
(Also known as: methyl mustard oil; MITC; isothiocyanic acid methyl ester; MIT; R014821)

GENERAL INFORMATION

Description

A highly toxic multipurpose soil fumigant. Also a pesticide transformation product and used in the production of many pesticides and other chemicals.

Examples of veterinary uses

Examples of species treated

Approval status

VMR 2013/2033 approval status (GB/UK)

EU Regulatory approval status

Chemical structure

Isomerism

None

Chemical formula

C₂H₃NS

Canonical SMILES

CN=C=S

Isomeric SMILES

International Chemical Identifier key (InChIKey)

LGDSHSYDSCRFAB-UHFFFAOYSA-N

International Chemical Identifier (InChI)

InChI=1S/C2H3NS/c1-3-2-4/h1H3

2D structure diagram/image available?

Yes

General status

Veterinary substance type

Metabolite Type

Soil; Groundwater

Substance groups

Fumigant pesticide

Minimum active substance purity

Known relevant impurities

Substance origin

Synthetic

Mode of action

Fumigant with contact action. It inactivates the sulfhydryl groups of essential enzymes in living organisms.

Molecular targets

CAS RN

556-61-6

EC number

209-132-5

CIPAC number

None allocated

US EPA chemical code

068103

PubChem CID

11167

CLP index number

615-002-00-2

Therapeutic Class

ATCvet Code

Controlled Drug?

Regulation 37/2010 MRL Classification

Molecular mass

73.11

PIN (Preferred Identification Name)

IUPAC name

methyl isothiocyanate

CAS name

isothiocyanatomethane

Global Governance status: Listed (✓) under

UK Poisons List Order 1972	Rotterdam Convention	Montreal Protocol
XNo The Poisons List Order 1972	XNo Rotterdam Convention	XNo Montreal Protocol
Stockholm Convention	OSPAR	EU Water Framework Directive
XNo Stockholm Convention	XNo OSPAR	XNo EU Water Framework Directive

Relevant Environmental Water Quality Standards

Forever chemical

Other status information

Physical state

Colourless crystalline solid

Can be a metabolite of:

Parent

Formation medium

Estimated maximum occurrence fraction

1107/2009 relevancy

metam-ammonium

Soil

0.829

Major fraction

metam-ammonium

Groundwater

Relevant

imazalil sulphate

Soil

Minor fraction

dazomet

Groundwater

Relevancy unknown

metam-sodium

Soil

0.829

Major fraction

metam-sodium

Groundwater

Relevant

metam-potassium

Groundwater

Relevant

metam-potassium

Soil

0.829

Major fraction

metam

Soil

0.829

Major fraction

metam

Groundwater

Relevant

imazalil nitrate

Soil

Minor fraction

imazalil

Soil

0.096

Minor fraction

dazomet

Soil

0.740

Major fraction

Commercial

Property

Value

Availability status

Introduction & key dates

1987, first registered

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

Schering

Example products using this active

Trapex

Formulation and application details

Usually supplied as an emulsifiable concentrate for drip irrigation systems

Commercial production

Commercial production of methyl isothiocyanate typically involves the reaction of methylamine with carbon disulfide, followed by oxidation or thermal decomposition of the resulting dithiocarbamate salt.

Impact on climate of production and use

Life cycle studies for the CO₂-e emissions from the production of methyl isothiocyanate are not available in the public domain. However, they can be roughly estimated from data that is available for similar processes. It is estimated that producing 1 kg of methyl isothiocyanate would emit around 7.7 kg CO₂-e.

ENVIRONMENTAL FATE

Property

Value

Source; quality score; and other information

Interpretation

Solubility - In water at 20 °C at pH 7 (mg l⁻¹)

8940

High

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

Melting point (°C)

Boiling point (°C)

119

Degradation point (°C)

Flashpoint (°C)

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

1.12 X 10⁰¹

Calculated

Log P

1.05

Low

Fat solubility of residues

Solubility

Data type

Density (g ml⁻¹)

1.07

Dissociation constant pKa) at 25 °C

12.3

Strong base

Vapour pressure at 20 °C (mPa)

1739000

Highly volatile. 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)

14.2

Moderately volatile

Volatilisation as max % of applied dose lost

From plant surface

From soil surface

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

Neutral soln: 235nm=635, 283nm=65, 321nm=17
Alkaline soln: 276nm=46, 320nm=5, 290nm=>10
Acidic soln: 235nm=635, 283nm=23, 290nm=>10

Surface tension (mN m⁻¹)

Refractive Index

Environmental release

Degradation

Property

Value

Source; quality score; and other information

Interpretation

Soil degradation (days) (aerobic)

DT₅₀ (typical)

2.1

Non-persistent

DT₅₀ (lab at 20 °C)

2.1

Non-persistent

DT₅₀ (field)

3.2

Non-persistent

DT₉₀ (lab at 20 °C)

6.99

Non-persistent

DT₉₀ (field)

13.1

Note

EU dossier (2023 metam) lab studies DT₅₀ (normalised) range: 1.08-3.24 days, DT₉₀ (normalised) range 3.6-10.78 days Soils=4;Ffield studies DT₅₀ (normalised) range 1.2-5.0 days, DT₉₀ (measured) 4.1-16.5 days, Soils=4; EU dossier (dazomet) lab studies range 5-32.7 days; Other literature studies Lab range - 24 soils, nursery and forest, various app rates

Manure DT₅₀ (days)

Aqueous photolysis DT₅₀ (days) at pH 7

Value

Moderately fast

Note

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

Value

Moderately persistent

Note

pH sensitive. DT40 50 days at pH4, 11 days at pH9

Water-sediment DT₅₀ (days)

0.37

Fast

Water phase only DT₅₀ (days)

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

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)

0.56

Mobile

K_foc (mL g⁻¹)

21.7

¹/_n

0.86

Notes and range

EU dossier (Metam, 2023) K_f range 0.21-1.38 mL g⁻¹, K_foc range 9.0-71.7 mL g⁻¹, ¹/_n range 0.755-9.1, Soils=10

pH sensitivity

Fate indices

Property

Value

Source; quality score; and other information

Interpretation

GUS leaching potential index

1.35

Calculated

Low leachability

Bio-concentration factor

BCF (l kg⁻¹)

2.6

Estimated

Low potential

CT₅₀ (days)

Not available

Known metabolites

None

ECOTOXICOLOGY

Terrestrial ecotoxicology

Property

Value

Source; quality score; and other information

Interpretation

Mammals - Acute oral LD₅₀ (mg kg⁻¹)

> 100

Rat

Moderate

Mammals - Short term dietary NOEL

(mg kg⁻¹)

(ppm diet)

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

Birds - Acute LD₅₀ (mg kg⁻¹)

127

Colinus virginianus

Moderate

Birds - Short term dietary (LC₅₀/LD₅₀)

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

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

4.0

Eisenia foetida

High

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

Soil micro-organisms

Collembola

Acute LC₅₀ (mg kg⁻¹)

Chronic NOEC (mg kg⁻¹)

Non-target plants

Vegetative vigour ER₅₀ (g ha⁻¹)

Seedling emergence ER₅₀ (g ha⁻¹)

Honeybees (Apis 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)

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

Chronic

Notes

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)

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)

Mode of exposure

Other bee species (2)

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

Mode of exposure

Beneficial insects (Ladybirds)

Beneficial insects (Lacewings)

Beneficial insects (Parasitic wasps)

Beneficial insects (Predatory mites)

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)

0.0531

Oncorhynchus mykiss

High

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

0.005

Oncorhynchus mykiss 28 day

High

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

0.137

Danio rerio Embryo

Moderate

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

0.076

Daphnia magna

High

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

0.00625

Daphnia magna

High

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

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

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

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 (free-floating, fonds growth, fresh) - 7 day (mg l⁻¹) (ErC₅₀, Semi-static)

1.133

Lemna gibba 3 day

Moderate

Aquatic plants (rooted, growth rate, fresh) - 14 day (mg l⁻¹)

Algae - Acute (growth rate, fresh; mg l⁻¹) (72 hr ErC₅₀, Static)

0.21

Raphidocelis subcapitata

Moderate

Algae - Chronic (growth rate, fresh; mg l⁻¹) (72 hr ErC10, Static)

0.09

Raphidocelis subcapitata

Moderate

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)

> 100

Rat

Moderate

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

> 1290

Rabbit

Mammals - Inhalation LC₅₀ (mg l⁻¹)

0.54

Rat 4 hr (whole body)

Other Mammal toxicity endpoints

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

0.004

Dog SF=100

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

0.03

Rat SF=100

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

0.004

Rabbit SF=300

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

0.004

Dog. SF=100

Dermal penetration studies (%)

Dangerous Substances Directive 76/464

Exposure Routes

Public

Some bystander risk identified via spray drift exposure

Occupational

May be fatal if absorbed through the skin
Respiratory equipment required to mitigate risk
Risks identified in glasshouse environments

Mammalian dose elimination route and rate

80-85% excreted with urine within approx. 80 hrs

Health issues

Specific human health issues (hazard-based)

Carcinogen

Genotoxic

Endocrine disruptor

; ; ; ;

No data found

Reproduction / development effects

Acetyl cholinesterase inhibitor

Neurotoxicant

No data found

Respiratory tract irritant

Skin irritant

Skin sensitiser

Eye irritant

Phototoxicant

General human health issues

Highly toxic by ingestion
Harmful via skin exposure and inhalation
Possible thyroid toxicant
US EPA - probable human carcinogen, CLP data - suspected carcinogen

Handling issues

Property

Value and interpretation

General

Corrosive
Not explosive or oxidising

CLP classification 2013

Health: H301, H312, H314; H317; H335, H351, H372
Environment: H400, H410

WHO Classification

II (Moderately hazardous)

UN Number

Waste disposal & packaging

Shelf-life, storage, stability and reactivity

TRANSLATIONS

Language

Name

English

methyl isothiocyanate

French

isothiocyanate de methyle

German

Methylisothiocyanat

Danish

methylisothiocyanat

Italian

Isotiocianato di metile

Spanish

isotiocianato de metilo

Greek

Polish

metyloizotiocyjanian

Swedish

Hungarian

Dutch

methylisothiocyanaat

Norwegian

Record last updated:	30/10/2025
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