2,4-D (Ref: L 208)

2,4-D (Ref: L 208)	Last updated: 13/11/2024
(Also known as: 2,4 PA; 2,4-dichlorophenoxyacetic acid; aqualin; hedonal)

SUMMARY

2,4-D is a selective, systemic herbicide used for the control of broad-leaved weeds. It is highly soluble in water, volatile and has a low potential to leach to groundwater based on its chemical properties. It is non-persistent in soil but may persist in aquatic systems under certain conditions. It is moderately toxic to mammals but should not bioaccumulate. It may have negative effects on reproduction, development and is considered to be a neurotoxin and an irritant. It is moderately toxic to birds and most aquatic species as well as honeybees 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: GUS: High leachability; Drainflow: Mobile	Ecotoxicity Moderate alert: Birds acute ecotoxicity: Moderate; Birds chronic ecotoxicity: Moderate; Fish acute ecotoxicity: Moderate; Bees acute oral ecotoxicity: Moderate; Earthworms acute ecotoxicity: Moderate; Earthworms chronic ecotoxicity: Moderate	Human health High alert: Endocrine disrupter; Reproduction/development effects; Neurotoxicant

GENERAL INFORMATION

Description

A translocated phenoxy herbicide for use in cereals, grass and amenity use. Can also be a pesticide transformation product

Example pests controlled

Broad-leaved weeds; Evasive weeds in aquatic situations

Example applications

Turf grass & pastures; Non-cropping situations; Amenity sites; Orchards; Cereals including barley, wheat and oats; Lucerne

Efficacy & activity

Availability status

Current

Introduction & key dates

circa 1950, introduction

GB regulatory status

GB COPR regulatory status

Approved

Date COPR inclusion expires

31/12/2030

GB LERAP status

Check label - may vary with formulation

EC Regulation 1107/2009 (repealing 91/414)

EC Regulation 1107/2009 status

Approved

Dossier rapporteur/co-rapporteur

Greece/Poland

Date EC 1107/2009 inclusion expires

31/12/2030

EU Candidate for substitution (CfS)

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, Morocco

Chemical structure

Isomerism

None

Chemical formula

C₈H₆Cl₂O₃

Canonical SMILES

C1=CC(=C(C=C1Cl)Cl)OCC(=O)O

Isomeric SMILES

No data

International Chemical Identifier key (InChIKey)

OVSKIKFHRZPJSS-UHFFFAOYSA-N

International Chemical Identifier (InChI)

InChI=1S/C8H6Cl2O3/c9-5-1-2-7(6(10)3-5)13-4-8(11)12/h1-3H,4H2,(H,11,12)

2D structure diagram/image available?

Yes

Cambridge Crystallographic Data Centre diagrams

Common Name	Relationship	Link
2,4-D	-
2,4-D	-

General status

Pesticide type

Herbicide, Plant Growth Regulator, Metabolite

Metabolite Type

Soil

Substance groups

Phenoxy herbicide; Phenoxy PGR; Phenoxyacetic herbicide; Auxin PGR

Minimum active substance purity

960 g kg⁻¹

Known relevant impurities

EU dossier - dioxins & furans; 2,4-dichlorophenol

Substance origin

Synthetic

Mode of action

Selective, systemic, absorbed through roots and increases biosynthesis and production of ethylene causing uncontrolled cell division and so damages vascular tissue. Synthetic auxin.

CAS RN

94-75-7

EC number

202-361-1

CIPAC number

US EPA chemical code

030001

PubChem CID

1486

CLP index number

607-039-00-8

Molecular mass

221.04

PIN (Preferred Identification Name)

(2,4-dichlorophenoxy)acetic acid

IUPAC name

(2,4-dichlorophenoxy)acetic acid

CAS name

(2,4-dichlorophenoxy)acetic acid

Other status information

Potential groundwater contaminant

Relevant Environmental Water Quality Standards

UK statutory standard for protection of aquatic life for inland, coastal & territorial surface waters as annual average: 40 µg l⁻¹

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

Limnocharis flava, Limnophila erecta, Papaver rhoeas, Sisymbrium orientale

Physical state

White powdery solid

Related substances & organisms

2,4-D-dimethylammonium

2,4-D-ammonium

2,4-D-choline

2,4-D-ethyl

2,4-D-isoctyl

2,4-D-lithium

Can be a metabolite of:

Parent

Formation medium

Estimated maximum occurrence fraction

1107/2009 relevancy

2,4-DEP

Soil

2,4-D-isoctyl

Soil

Major fraction

2,4-D-ammonium

Soil

1.00

Major fraction

2,4-D-choline

Soil

Major fraction

2,4-D-diethylammonium

Soil

Major fraction

2,4-D-dodecylammonium

Soil

Major fraction

2,4-D-ethyl

Soil

Major fraction

2,4-D-heptylammonium

Soil

Major fraction

2,4-D-isobutyl

Soil

Major fraction

2,4-D-isopropyl

Soil

Major fraction

2,4-D-isopropylammonium

Soil

Major fraction

2,4-D-lithium

Soil

Major fraction

2,4-D-meptyl

Soil

Major fraction

2,4-D-methyl

Soil

Major fraction

2,4-D-methylammonium

Soil

Major fraction

2,4-D-octyl

Soil

Major fraction

2,4-D-pentyl

Soil

Major fraction

2,4-D-potassium

Soil

Major fraction

2,4-D-propyl

Soil

Major fraction

2,4-D-sodium

Soil

Major fraction

2,4-D-tefuryl

Soil

Major fraction

2,4-D-tetradecylammonium

Soil

Major fraction

2,4-D-triethylammonium

Soil

Major fraction

2,4-D-trolamine

Soil

Major fraction

2,4-D-doboxyl

Soil

Major fraction

2,4-D-tripromine

Soil

Major fraction

2,4-D-etexyl

Soil

1.00

Major fraction

2,4-D-terboxyl

Soil

Major fraction

2,4-D-butotyl

Soil

1.00

Major fraction

2,4-D-dimethylammonium

Soil

1.00

Major fraction

2,4-D-diolamine

Soil

Major fraction

2,4-D-butyl ester

Soil

1.00

Major fraction

2,4-DB

Soil

0.261

Major fraction

Formulations

Property

Value

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

AgriChem
Dow AgroSciences
Headland
Nufarm
Vitax

Example products using this active

Depitox
Esteem
Weed B Gone
Killex
Junction
Tordon 101
Herboxone
Polo
Staff 500
DMA SL
DMA 600

Formulation and application details

Often supplied as a soluble concentrate which is mixed with water and applied as a spray

ENVIRONMENTAL FATE

Property

Value

Source; quality score; and other information

Interpretation

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

24300

High

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

6400

Toluene

212000

Acetone

810000

Methanol

8000

Dichloromethane

Melting point (°C)

138.7

Boiling point (°C)

273.0

Degradation point (°C)

200

Flashpoint (°C)

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

1.51 X 10^-01

Calculated

Log P

-0.82

Low

Fat solubility of residues

Solubility

Data type

Density (g ml⁻¹)

1.57

Dissociation constant pKa) at 25 °C

3.40

Strong acid

Vapour pressure at 20 °C (mPa)

0.009

Low volatility

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

4.0 X 10^-06

Non-volatile

Volatilisation as max % of applied dose lost

From plant surface

From soil surface

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

pH 1.16: 227nm=7344.4, 228nm=1448.9
pH 7.0: 228nm=8815.6, 283nm=1940
pH 11.3: 229nm=8984.5nm, 283nm=1977.5

Surface tension (mN m⁻¹)

70.5

Degradation

Property

Value

Source; quality score; and other information

Interpretation

General biodegradability

Soil degradation (days) (aerobic)

DT₅₀ (typical)

4.4

Non-persistent

DT₅₀ (lab at 20 °C)

4.4

Non-persistent

DT₅₀ (field)

28.8

Non-persistent

DT₉₀ (lab at 20 °C)

47.9

Moderately persistent

DT₉₀ (field)

96.3

DT₅₀ modelling endpoint

Note

EU dossier lab studies DT₅₀ range 1.2-94.6 days, DT₉₀ range 5.4-195.56 days; Field studies DT₅₀ range 22-38 days, DT₉₀ range 74-127 days; Other sources: 1.7-13.1 days (R3)

Dissipation rate RL₅₀ (days) on plant matrix

Value

2.2

Note

Published literature RL₅₀ range 1.1-3.0 days, 3 field crops, various matrices, n=3

Dissipation rate RL₅₀ (days) on and in plant matrix

Value

12.7

Note

Published literature RL₅₀ range 1.1-24.8 days, 4 field crops, various matrices, n=6

Aqueous photolysis DT₅₀ (days) at pH 7

Value

Stable

Note

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

Value

Stable

Note

Stable between pH 5 to pH 9

Water-sediment DT₅₀ (days)

18.2

Fast

Water phase only DT₅₀ (days)

7.7

Moderately fast

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)

0.70

Mobile

K_oc (mL g⁻¹)

39.3

Notes and range

EU dossier K_d range 0.32-1.22 mL g⁻¹, K_oc range 23-68 mL g⁻¹, Soils=7; Other literature multiple studies K_d range 1.59-1.88 mL g⁻¹, K_oc range 31-275 mL g⁻¹ (R4)

Freundlich

K_f (mL g⁻¹)

0.45

Mobile

K_foc (mL g⁻¹)

¹/_n

0.83

Notes and range

EU dossier K_f range 0.19-0.83 mL g⁻¹, K_foc range 12-42 mL g⁻¹, ¹/_n range 0.78-0.90, Soils=7; Other literature multiple studies K_f range 0.003-8.7 mL g⁻¹, K_foc range 0.15-875 mL g⁻¹, ¹/_n range 0.35-1.59, Soils = 18

pH sensitivity

Fate indices

Property

Value

Source; quality score; and other information

Interpretation

GUS leaching potential index

3.82

Calculated

High leachability

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

Value

6.92 X 10^-01

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

Bio-concentration factor

BCF (l kg⁻¹)

Whole fish

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

2,4-dichlorophenol

Major fraction

0.380

2,4-dichloroanisole

Major fraction

0.150

4-chlorophenol

Major fraction

0.330

Known groundwater metabolites

None

Other known metabolites

Metabolite name and reference

Aliases

Formation medium / Rate

Estimated maximum occurrence fraction

(4-chlorophenoxy)acetic acid

(2,4-dichloro-5-hydroxyphenoxy)acetic acid

5-OH-2,4-D

Plant

(2,3-dichloro-4-hydroxyphenoxy)acetic acid

4-OH-2,3-D

Plant

1,2,4-benzenetriol

Water (photolysis)

2-ethylhexyl (2,4-dichlorophenoxy)acetate

2,4-D 2-EHE

(2,5-dichloro-4-hydroxyphenoxy)acetic acid

4-OH-2,5-D

Plant

ECOTOXICOLOGY

Terrestrial ecotoxicology

Property

Value

Source; quality score; and other information

Interpretation

Mammals - Acute oral LD₅₀ (mg kg⁻¹)

> 300

Rat

Moderate

Mammals - Short term dietary NOEL

(mg kg⁻¹)

Rat

High

(ppm diet)

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

> 40.2

Unknown species Reproductive NOAEL

Moderate

Birds - Acute LD₅₀ (mg kg⁻¹)

> 500

Colinus virginianus

Moderate

Birds - Short term dietary (LC₅₀/LD₅₀)

> 5620 mg kg feed⁻¹

Colinus virginianus

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

> 100

Coturnix japonica

Moderate

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

350

Eisenia foetida

Moderate

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

62.5

Eisenia foetida

Moderate

Soil micro-organisms

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

Dose: 3 mg kg⁻¹ 28 Day

Collembola

Acute LC₅₀ (mg kg⁻¹)

Chronic NOEC (mg kg⁻¹)

Folsomia candida

Non-target plants

Lettuce
Vegetative vigour, ER₅₀
as g ha⁻¹

Lettuce
Seedling emergence, ER₅₀
as g ha⁻¹

Honeybees (Apis spp.)

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

> 100

Apis mellifera

Low

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

Apis mellifera

Moderate

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)

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) as Mortality LR₅₀ g ha⁻¹

> 3000

Aphidius rhopalosiphi

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

> 3000

Typhlodromus pyri

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)

100

Pimephales promelas

Moderate

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

27.2

Oryzias latipes 28 day

Low

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

> 160

Danio rerio

Low

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

134.2

Daphnia magna

Low

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

46.2

Daphnia magna

Low

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

> 272

Ceriodaphnia dubia

Low

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

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

> 3.88

Chironomus spp. 48 hr

Moderate

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)

2.7

Lemna gibba

Moderate

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

24.2

Raphidocelis subcapitata

Low

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

100

Chlorella vulgaris

Low

Mesocosm study data

NOEAEC mg l⁻¹

Marine bivalves – NOEC, mortality (mg l⁻¹)

99.5

Crassostrea gigas

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)

> 300

Rat

Moderate

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

2000

Rat

Mammals - Inhalation LC₅₀ (mg l⁻¹)

> 1.79

Rat 4 hr (whole body)

Other Mammal toxicity endpoints

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

0.02

Rat SF=100

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

0.30

Rat AF=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)

0.02

Rat SF=100

Dermal penetration studies (%)

0.1-4.0

concentration dependent

Dangerous Substances Directive 76/464

Exposure Routes

Public

Small risk of dermal exposure from contact with sprayed vegetation
No risk to consumers via acute residue

Occupational

Moderate risk of inhalation and dermal exposure depending on personal protection clothing and equipment utilised

MRLs

European

EU MRL pesticide database

Great Britain

GB MRL Register

Notes

Drinking Water Standards

Non-statutory WHO drinking water guideline 0.03 mg l⁻¹

UK EA QS database 2018

Drinking Water MAC (μg l⁻¹)

70.0

(For USA - EPA drinking water regulations)

Mammalian dose elimination route and rate

Rapidly excreted in urine unmetabolised

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

IARC - Group 2B carcinogen; US EPA - Not classifiable as human carcinogen
Excessive doses may affect digestive systems
Possible liver and kidney toxicant
Endocrine issues - Synergistic androgenic effects when combined with testosterone

Handling issues

Property

Value and interpretation

General

Corrosive to metals
IMDG Transport Hazard Class 9
Not explosive or oxidising
Not expected to auto-ignite; Not highly flammable

CLP classification 2013

Health: H302, H317, H318, H335
Environment: H412

WHO Classification

II (Moderately hazardous)

UN Number

UN3077

Waste disposal & packaging

Dispose of in accordance with local regulations
Packaging Group III (minor danger)

Shelf-life, storage, stability and reactivity

TRANSLATIONS

Language

Name

English

2,4-D

French

2,4-D

German

2,4-D

Danish

2,4-D

Italian

2,4-D

Spanish

2,4-D

Greek

Polish

2,4-D

Swedish

2,4-D

Hungarian

2,4-D

Dutch

2,4-D

Norwegian

2,4-D

Record last updated:	13/11/2024
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