2,4,5-trichlorophenoxyacetic acid

2,4,5-trichlorophenoxyacetic acid	Last updated: 25/05/2025
(Also known as: 2,4,5-T; trioxone; 2,4,5-T acid)

SUMMARY

2,4,5-trichlorophenoxyacetic acid is an obsolete herbicide that was used mainly on non-cropped areas. It is moderately soluble in water, has low volatility and tends to be persistent in soil systems. 2,4,5-trichlorophenoxyacetic acid has a high potential for leaching to groundwater. Limited data is available regarding its toxicity to biodiversity but it is moderately toxic to fish and algae. This substance has a moderate oral mammalian toxicity and is a reproduction/developmental toxin.

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: Persistent; GUS: High leachability; Drainflow: Very mobile	Ecotoxicity Moderate alert: Fish acute ecotoxicity: Moderate; Daphnia acute ecotoxicity: Moderate Warning: Significant data are missing	Human health High alert: Reproduction/development effects Warning: Significant data are missing

GENERAL INFORMATION

Description

An obsolete herbicide used as a foliar spray to defoliate broadleaved plants

Example pests controlled

Growth - defoliant; and total vegetation control Deciduous brush and scrub control

Example applications

Non-crop areas including rough grass pastures, farmyards, ditchbanks, industrial sites, rights of way, roadways; railways

Efficacy & activity

Availability status

Considered obsolete but may be available in some countries

Introduction & key dates

circa 1947, introduced

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

Not applicable

Date EC 1107/2009 inclusion expires

Not applicable

EU Candidate for substitution (CfS)

Not applicable

Listed in EU database

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

C₈H₅Cl₃O₃

Canonical SMILES

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

Isomeric SMILES

International Chemical Identifier key (InChIKey)

SMYMJHWAQXWPDB-UHFFFAOYSA-N

International Chemical Identifier (InChI)

InChI=1S/C8H5Cl3O3/c9-4-1-6(11)7(2-5(4)10)14-3-8(12)13/h1-2H,3H2,(H,12,13)

2D structure diagram/image available?

Yes

Cambridge Crystallographic Data Centre diagrams

Common Name	Relationship	Link
2,4,5-trichlorophenoxyacetic acid	-

General status

Pesticide type

Herbicide; Plant Growth Regulator

Substance groups

Phenoxy herbicide; Auxin PGR

Minimum active substance purity

Known relevant impurities

Substance origin

Synthetic

Mode of action

Synthetic auxin, readily absorbed by foliage and roots and translocated throughout the plant.

CAS RN

93-76-5

EC number

202-273-3

CIPAC number

None allocated

US EPA chemical code

082001

PubChem CID

1480

CLP index number

607-041-00-9

Molecular mass

255.48

PIN (Preferred Identification Name)

IUPAC name

(2,4,5-trichlorophenoxy)acetic acid

CAS name

2,4,5-trichlorophenoxyacetic acid

Other status information

Chemical subject to PIC regulations; POP; PAN Dirty Dozen; OSPAR soc; Potential marine pollutant; Potential groundwater pollutant

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

Physical state

Pale yellow crystalline solid

Formulations

Property

Value

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

Dow
Boehringer
ICI Plant Protection

Example products using this active

BCF-Bushkiller
Super D Weedone
Esterone 245
Transamine

Formulation and application details

Usually formulated as an emulsifiable concentrate or ULV

ENVIRONMENTAL FATE

Property

Value

Source; quality score; and other information

Interpretation

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

268

Moderate

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

400

Heptane

5000

Ethanol

5000

Methanol

5000

Toluene

Melting point (°C)

156

Boiling point (°C)

Decomposes before boiling

Degradation point (°C)

Flashpoint (°C)

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

1.00 X 10⁰⁴

Calculated

Log P

4.0

Other data Log P=0.60-3.46 (USDA)

High

Fat solubility of residues

Solubility

Data type

Density (g ml⁻¹)

1.8

Dissociation constant pKa) at 25 °C

2.88

Strong acid

Vapour pressure at 20 °C (mPa)

0.01

Low volatility

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

1.2 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

Surface tension (mN m⁻¹)

Degradation

Property

Value

Source; quality score; and other information

Interpretation

General biodegradability

Soil degradation (days) (aerobic)

DT₅₀ (typical)

350

Persistent

DT₅₀ (lab at 20 °C)

350

Persistent

DT₅₀ (field)

DT₉₀ (lab at 20 °C)

DT₉₀ (field)

DT₅₀ modelling endpoint

Note

General literature gives DT₅₀ around 48 weeks

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

Note

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

Value

Note

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)

2.48

Very mobile

K_oc (mL g⁻¹)

Notes and range

USDA database K_d range 0.30-6.20 mL g⁻¹; Kioc range 39-186 mL g⁻¹, n=5; Other data K_oc range 39-92,123 mL g⁻¹

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

7.63

Calculated

High leachability

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

Value

1.21 X 10⁰²

Calculated

Note

Potential for particle bound transport index

Medium

Calculated

Potential for loss via drain flow

Very mobile

Calculated

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

Bio-concentration factor

BCF (l kg⁻¹)

CT₅₀ (days)

Known soil and groundwater metabolites

None

Other known metabolites

Metabolite name and reference

Aliases

Formation medium / Rate

Estimated maximum occurrence fraction

2,4,5-trichlorophenol

Surface water

ECOTOXICOLOGY

Terrestrial ecotoxicology

Property

Value

Source; quality score; and other information

Interpretation

Mammals - Acute oral LD₅₀ (mg kg⁻¹)

500

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)

Birds - Short term dietary (LC₅₀/LD₅₀)

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

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

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

Soil micro-organisms

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)

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)

1.3

Oncorhynchus mykiss

Moderate

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

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

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

5.0

Daphnia magna

Moderate

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

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

200

Ceriodaphnia dubia

Low

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, growth) - Acute 7 day EC₅₀, biomass (mg l⁻¹)

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

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

2.0

Green algae

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)

500

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)

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)

Dermal penetration studies (%)

Dangerous Substances Directive 76/464

Exposure Routes

Public

Occupational

The most probable route of exposure is via inhalation and dermal exposure

MRLs

European

EU MRL pesticide database

Great Britain

GB MRL Register

Notes

Drinking Water Standards

Non-statutory WHO drinking water guideline 0.009 mg l⁻¹

UK EA QS database 2018

Drinking Water MAC (μg l⁻¹)

Mammalian dose elimination route and rate

Health issues

Specific human health issues

Carcinogen

Genotoxic

Endocrine disruptor

No data found

; ; ; ;

Reproduction / development effects

Acetyl cholinesterase inhibitor

Neurotoxicant

No data found

Respiratory tract irritant

Skin irritant

Skin sensitiser

No data found

Eye irritant

Phototoxicant

No data found

General human health issues

Toxic by ingestion and inhalation
May cause contact dermatitis

Handling issues

Property

Value and interpretation

General

No information available

CLP classification 2013

Health: H302, H315, H319, H335
Environment: H400, H410

WHO Classification

Not classified: Obsolete (Not classified: Obsolete)

UN Number

Waste disposal & packaging

Shelf-life, storage, stability and reactivity

TRANSLATIONS

Language

Name

English

2,4,5-trichlorophenoxyacetic acid

French

acide 2,4,5-trichloro phenoxyacetique

German

(2,4,5-Trichlor-phenoxy)-essigsaeure

Danish

Italian

acido (2,4,5-tricloro-fenossi)-acetico

Spanish

Greek

Polish

kwas 2,4,5-trojchlorofenoksyoctowy

Swedish

Hungarian

Dutch

2,4,5-trichloor-fenoxy)-azijnzuur

Norwegian

Record last updated:	25/05/2025
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