Paraquat dichloride

Paraquat dichloride	Last updated: 26/05/2025
(Also known as: methyl viologen )

SUMMARY

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: Very persistent; Potential for particle bound transport: High	Ecotoxicity High alert: Birds acute ecotoxicity: High	Human health Moderate alert: Mammals acute toxicity: Moderate; Reproduction/development effects

GENERAL INFORMATION

Description

A herbicide used to control common weeds and grasses in a wide range of agricultural and amenity situations

Example pests controlled

Broadleaved weeds including cocksfoot; Grasses including wild oats, Yorkshire fog grass, ryegrass, fescue

Example applications

Rice; Lucerne; Beans & peas; Hops; Vineyards; Potaoes; Non-cropped areas such as roadways, paths

Efficacy & activity

Availability status

Introduction & key dates

1964, first registered USA

GB regulatory status

GB COPR regulatory status

Not approved

Date COPR inclusion expires

Not applicable

GB LERAP status

No UK approval for use as a plant protection agent

EC Regulation 1107/2009 (repealing 91/414)

EC Regulation 1107/2009 status

Not approved

Dossier rapporteur/co-rapporteur

Date EC 1107/2009 inclusion expires

Not applicable

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

Chemical structure

Isomerism

None

Chemical formula

C₁₂H₁₄Cl₂N₂

Canonical SMILES

C[N+]1=CC=C(C=C1)C2=CC=[N+](C=C2)C.[Cl-].[Cl-]

Isomeric SMILES

International Chemical Identifier key (InChIKey)

FIKAKWIAUPDISJ-UHFFFAOYSA-L

International Chemical Identifier (InChI)

InChI=1S/C12H14N2.2ClH/c1-13-7-3-11(4-8-13)12-5-9-14(2)10-6-12;;/h3-10H,1-2H3;2*1H/q+2;;/p-2

2D structure diagram/image available?

Yes

Cambridge Crystallographic Data Centre diagrams

Common Name	Relationship	Link
paraquat dichloride	-
paraquat dibromide	Variant

General status

Pesticide type

Herbicide

Substance groups

Quarternary ammonium herbicide

Minimum active substance purity

Known relevant impurities

EU dossier - free 4,4¢-bipyridyl 0.2%

Substance origin

Synthetic

Mode of action

Broad-spectrum, non-residual activity with contact and some desiccant action. Photosystem I (electron transport) inhibitor.

CAS RN

1910-42-5

EC number

217-615-7

CIPAC number

US EPA chemical code

061601

PubChem CID

15938

CLP index number

613-090-00-7

Molecular mass

257.16

PIN (Preferred Identification Name)

1,1'-dimethyl-[4,4'-bipyridine]-1,1'-diium dichloride

IUPAC name

1,1'-dimethyl-4,4'-bipyridinium dichloride

CAS name

1,1'-dimethyl-4,4'-bipyridinium dichloride

Other status information

PAN Dirty Dozen; Chemical subject to PIC regulations; Subject to the provisions of the UK Poisons Act 1972

Relevant Environmental Water Quality Standards

Herbicide Resistance Class (HRAC MoA class)

Herbicide Resistance Class (WSSA MoA class)

Insecticide Resistance Class (IRAC MoA class)

Not applicable

Fungicide Resistance Class (FRAC MOA class)

Not applicable

Examples of recorded resistance

Lolium rigidum

Physical state

off-white crystalline solid

Related substances & organisms

paraquat

paraquat diiodide

paraquat dimetilsulfate

Formulations

Property

Value

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

Syngenta
ICI Plant Protection
Pillar International
Inquinosa

Example products using this active

Gramoxone Extra
Gramoxone Max
Cyclone
Pathclear

Formulation and application details

Usually formulated as a soluble concentrate or aqueous liquid

ENVIRONMENTAL FATE

Property

Value

Source; quality score; and other information

Interpretation

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

620000

High

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

100

Acetone

100

Toluene

100

Ethyl acetate

100

Hexane

Melting point (°C)

Decomoses before melting

Boiling point (°C)

Decomposes before boiling

Degradation point (°C)

340

Flashpoint (°C)

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

3.16 X 10^-05

Calculated

Log P

-4.5

Low

Fat solubility of residues

Solubility

Data type

Density (g ml⁻¹)

1.5

Dissociation constant pKa) at 25 °C

Not applicable

No dissociation

Vapour pressure at 20 °C (mPa)

0.01

Low volatility

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

4.0 X 10^-09

Non-volatile

Volatilisation as max % of applied dose lost

From plant surface

From soil surface

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

290nm

Surface tension (mN m⁻¹)

Degradation

Property

Value

Source; quality score; and other information

Interpretation

General biodegradability

Soil degradation (days) (aerobic)

DT₅₀ (typical)

365

Very persistent

DT₅₀ (lab at 20 °C)

365

Very persistent

DT₅₀ (field)

365

Very persistent

DT₉₀ (lab at 20 °C)

DT₉₀ (field)

DT₅₀ modelling endpoint

Note

Stable and persistent, General literature DT₅₀ up to 20 years

Dissipation rate RL₅₀ (days) on plant matrix

Value

Note

Dissipation rate RL₅₀ (days) on and in plant matrix

Value

Note

Aqueous photolysis DT₅₀ (days) at pH 7

Value

Stable

Note

Stable at all relevant wavelengths

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

Value

Stable

Note

Stable at all relevant pHs

Water-sediment DT₅₀ (days)

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)

Non-mobile

K_oc (mL g⁻¹)

100000

Notes and range

EU dossier K_oc range 8400-40000000 mL g⁻¹

Freundlich

K_f (mL g⁻¹)

3240

Non-mobile

K_foc (mL g⁻¹)

228537

¹/_n

2.9

Notes and range

K_f range 717-6260 mL g⁻¹; K_foc range 14340-581000 mL g⁻¹; ¹/_n range 1.96-4.0, Soils=9

pH sensitivity

No, adsorption correlates to soil clay content

Fate indices

Property

Value

Source; quality score; and other information

Interpretation

GUS leaching potential index

-3.48

Calculated

Low leachability

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

Value

5.35 X 10^-03

Calculated

Note

Estimated concentrations of chemicals with Koc values greater than 9995 ml g⁻¹ are beyond the scope of the regression data used in SCI-GROW development. If there are concerns for such chemicals, a higher tier groundwater exposure assessment should be considered, regardless of the concentration returned by SCI-GROW

Potential for particle bound transport index

High

Calculated

Potential for loss via drain flow

Non-mobile

Calculated

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

Bio-concentration factor

BCF (l kg⁻¹)

Low risk

Based on LogP < 3

Low risk

CT₅₀ (days)

Known metabolites

None

ECOTOXICOLOGY

Terrestrial ecotoxicology

Property

Value

Source; quality score; and other information

Interpretation

Mammals - Acute oral LD₅₀ (mg kg⁻¹)

110

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)

Unknown species

High

Birds - Short term dietary (LC₅₀/LD₅₀)

698 mg kg feed⁻¹

Unknown species

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

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

> 1000

Eisenia foetida

Low

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

> 1000

Eisenia foetida 7 day

Low

Soil micro-organisms

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

Dose: 720 kg ha⁻¹ 1 year

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)

Moderate

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)

> 48

Moderate

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)

Oncorhynchus mykiss

Moderate

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

2.5

Oncorhynchus mykiss 30 day

Moderate

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

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

1.2

Daphnia magna

Moderate

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

0.01

Daphnia magna

Moderate

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)

0.367

Chironomus riparius

Moderate

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

100

Chironomus riparius

Moderate

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

0.088

Lemna gibba

Moderate

Aquatic plants (rooted, growth) - Acute 14 day EC₅₀, biomass (mg l⁻¹)

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

0.32

Raphidocelis subcapitata

Moderate

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

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)

110

Rat

Moderate

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

Mammals - Inhalation LC₅₀ (mg l⁻¹)

Other Mammal toxicity endpoints

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

0.004

as paraquat

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

0.005

as paraquat

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

Not applicable

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

0.0004

as paraquat

Dermal penetration studies (%)

0.5

Dangerous Substances Directive 76/464

Exposure Routes

Public

No unacceptable risks to bystanders identified

Occupational

No unacceptable risks to operators or other workers identified

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

Respiratory tract irritant

Skin irritant

Skin sensitiser

No data found

Eye irritant

Phototoxicant

No data found

General human health issues

Potential liver, kidney, stomach, intestine and respiratory system toxicant
May damage lungs if inhaled

Handling issues

Property

Value and interpretation

General

Not explosive or oxidising
IMDG Transport Hazard Class 6.1
Not expected to auto-ignite; Not highly flammable

CLP classification 2013

Health: H301, H311, H315, H319, H330, H335, H372
Environment: H400, H410

WHO Classification

II (Moderately hazardous)

UN Number

UN2811

Waste disposal & packaging

Packaging Group II (moderate danger)

Shelf-life, storage, stability and reactivity

TRANSLATIONS

Language

Name

English

paraquat dichloride

French

German

Danish

Italian

Spanish

Greek

Polish

Swedish

Hungarian

Dutch

Norwegian

Record last updated:	26/05/2025
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