Paraquat (Ref: PP 148)

Paraquat (Ref: PP 148)	Last updated: 29/05/2025
(Also known as: orthoparaquat; PP 910)

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 High alert: Mammals chronic toxicity: High; Genotoxic

GENERAL INFORMATION

Description

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

Example pests controlled

Broadleaved weeds including cocksfoot, blue heliotrope (Heliotropium amplexicaule); Grasses including wild oats, Yorkshire fog grass, ryegrass, fescue; Datura spp.; Wandering jew (Tradescantia fluminensis)

Example applications

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

Efficacy & activity

Availability status

Current

Introduction & key dates

1962, introduced

GB regulatory status

GB COPR regulatory status

Not approved

Date COPR inclusion expires

Expired

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

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; USA; Canada; Mexico; Brazil; Japan; India; China; Indonesia; Thailand; New Zealand

Chemical structure

Isomerism

None

Chemical formula

C₁₂H₁₄N₂

Canonical SMILES

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

Isomeric SMILES

No data

International Chemical Identifier key (InChIKey)

INFDPOAKFNIJBF-UHFFFAOYSA-N

International Chemical Identifier (InChI)

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

2D structure diagram/image available?

Yes

Cambridge Crystallographic Data Centre diagrams

Common Name	Relationship	Link
paraquat dichloride	Variant
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

Substance origin

Synthetic

Mode of action

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

CAS RN

4685-14-7

EC number

217-615-7

CIPAC number

US EPA chemical code

PubChem CID

15939

CLP index number

No data found

Molecular mass

186.25

PIN (Preferred Identification Name)

IUPAC name

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

CAS name

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

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

Colourless to pale yellow crystalline solid

Related substances & organisms

paraquat dichloride

paraquat diiodide

paraquat dimetilsulfate

Formulations

Property

Value

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

AgriGuard
Clayton
Syngenta

Example products using this active

AgriGuard Paraquat

Formulation and application details

Often supplied as a soluble concentrate that is mixed with water and used as a spray

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)

143000

Methanol

100

Acetone

100

Toluene

100

Hexane

Melting point (°C)

Boiling point (°C)

Degradation point (°C)

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)

4.00 X 10^-12

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)

3000

Very persistent

DT₅₀ (lab at 20 °C)

5000

Very persistent

DT₅₀ (field)

2800

Very persistent

DT₉₀ (lab at 20 °C)

DT₉₀ (field)

DT₅₀ modelling endpoint

Note

Field studies DT₅₀ range 7-8 years (UK)

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

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

Value

Stable

Note

Stable pH 5 to pH 9, 30 days at 25 and 40 °C

Water-sediment DT₅₀ (days)

Stable

Water phase only DT₅₀ (days)

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

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)

1000000

Notes and range

Freundlich

K_f (mL g⁻¹)

K_foc (mL g⁻¹)

¹/_n

Notes and range

pH sensitivity

Fate indices

Property

Value

Source; quality score; and other information

Interpretation

GUS leaching potential index

-6.89

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)

Rat

(ppm diet)

> 100

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

2.5

Unknown species Lowest relevant reproductive NOAEL/NOEL

High

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)

Soil micro-organisms

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

Dose: 720 kg ha⁻¹ 1 yr

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)

9.26

Moderate

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

> 9.06

Moderate

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)

Oncorhynchus mykiss

Moderate

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

> 8.0

Clarias gariepinus

Moderate

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

> 100

Danio rerio

Low

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

4.4

Daphnia magna

Moderate

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

0.12

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)

0.037

Lemna gibba

Moderate

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

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

0.00023

Raphidocelis subcapitata

High

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)

200

Rat

Mammals - Inhalation LC₅₀ (mg l⁻¹)

0.6

Rat

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)

0.005

Dog SF=100

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

Dog 90 day SF=100

Dermal penetration studies (%)

0.5

Dangerous Substances Directive 76/464

[No unacceptable risks to bystanders identified]

Exposure Routes

Public

No unacceptable risks to operators or other workers identified

Occupational

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
Some evidence has suggested that paraquat may be a carcinogen

Handling issues

Property

Value and interpretation

General

Not explosive or oxidising
IMDG Transport Hazard Class 6.1

CLP classification 2013

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

WHO Classification

II (Moderately hazardous)

UN Number

UN2810

Waste disposal & packaging

Packaging Group II (moderate danger)

Shelf-life, storage, stability and reactivity

Chemically stable under standard ambient conditions

TRANSLATIONS

Language

Name

English

paraquat

French

paraquat

German

Paraquat

Danish

paraquat

Italian

paraquat

Spanish

paracuat

Greek

Polish

parakwat

Swedish

Hungarian

Dutch

Norwegian

Record last updated:	29/05/2025
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