2,4-DB (Ref: ENT 8538)

2,4-DB (Ref: ENT 8538)	Last updated: 29/08/2024
(Also known as: hedonal; trinoxol)

SUMMARY

2,4-DB is a post-emergence herbicide that is used to control broad-leaved weeds. It is highly soluble in water and most organic solvents. It is relatively volatile but it may leach to groundwater under certain conditions. It is not persistent in soil systems but may tend to be persistent in aquatic systems. It is moderately toxic to mammals and there is some concern regarding its potential for bioaccumulation. It is moderately toxic to birds, earthworms, honeybees and most aquatic organisms.

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 Moderate alert: Drainflow: Moderately mobile	Ecotoxicity Moderate alert: Birds acute ecotoxicity: Moderate; Birds chronic ecotoxicity: Moderate; Fish acute ecotoxicity: Moderate; Daphnia acute ecotoxicity: Moderate; Daphnia chronic ecotoxicity: Moderate; Earthworms chronic ecotoxicity: Moderate	Human health Moderate alert: Mammals acute toxicity: Moderate; Mammals chronic toxicity: Moderate; Genotoxic; Endocrine disrupter

GENERAL INFORMATION

Description

A herbicide used for post-emergence control of many annual and perennial broad-leaved weeds

Example pests controlled

Broad-leaved weeds including bindweed, thistles, docks, nettles, mallow, pigweed, plantain; Brush

Example applications

Wheat; Barley; Maize; Sorghum; Rice; Grassland: Lawns and turf areas; Aquatic situations; Non-cropped areas including roadsides, railways and utilities rights of way.

Efficacy & activity

Availability status

Current

Introduction & key dates

1942, first identified; 1944, first marketed

GB regulatory status

GB COPR regulatory status

Approved

Date COPR inclusion expires

31/10/2032

GB LERAP status

None

EC Regulation 1107/2009 (repealing 91/414)

EC Regulation 1107/2009 status

Approved

Dossier rapporteur/co-rapporteur

Belgium/Greece

Date EC 1107/2009 inclusion expires

31/10/2032

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

Chemical structure

Isomerism

None

Chemical formula

C₁₀H₁₀Cl₂O₃

Canonical SMILES

CNC.C1=CC(=C(C=C1Cl)Cl)OCCCC(=O)O

Isomeric SMILES

No data

International Chemical Identifier key (InChIKey)

YIVXMZJTEQBPQO-UHFFFAOYSA-N

International Chemical Identifier (InChI)

InChI=1S/C10H10Cl2O3/c11-7-3-4-9(8(12)6-7)15-5-1-2-10(13)14/h3-4,6H,1-2,5H2,(H,13,14)

2D structure diagram/image available?

Yes

Cambridge Crystallographic Data Centre diagrams

Common Name	Relationship	Link
2,4-DB	-

General status

Pesticide type

Herbicide, Plant Growth Regulator

Substance groups

Phenoxy herbicide; Auxin PGR

Minimum active substance purity

940 g kg⁻¹

Known relevant impurities

EU dossier 2016 - dibenzo-p-dioxins; polychlorinated dibenzofurans

Substance origin

Synthetic

Mode of action

Selective, systemic. Synthetic auxin causing stem and leaf malformations leading to death.

CAS RN

94-82-6

Alternative/old CAS RN

607-083-00-8

EC number

202-366-9

CIPAC number

US EPA chemical code

030801

PubChem CID

1489

CLP index number

607-083-00-8

Molecular mass

249.09

PIN (Preferred Identification Name)

4-(2,4-dichlorophenoxy)butanoic acid

IUPAC name

4-(2,4-dichlorophenoxy)butyric acid

CAS name

4-(2,4-dichlorophenoxy)butanoic acid

Other status information

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

White crystals whith faint phenolic odour

Related substances & organisms

linuron

Formulations

Property

Value

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

United Phosphorus
Headland

Example products using this active

Butoxone
Butyrac
Cedar
DB Straight
Embutone
Venceweed

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)

4385

High

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

185200

Acetone

113800

Methanol

90700

Ethyl acetate

10500

Xylene

Melting point (°C)

119

Boiling point (°C)

Decomposes before boiling

Degradation point (°C)

270

Flashpoint (°C)

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

1.66 X 10⁰¹

Calculated

Log P

1.22

Low

Fat solubility of residues

Solubility

Data type

Density (g ml⁻¹)

1.46

Dissociation constant pKa) at 25 °C

4.1

Weak acid

Vapour pressure at 20 °C (mPa)

9.0 X 10^-04

Low volatility

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

4.6 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

Neutral sol: 230 nm= 9820, 284nm = 2260, 291nm = 1790

Surface tension (mN m⁻¹)

71.0

99.1% w/w

Degradation

Property

Value

Source; quality score; and other information

Interpretation

General biodegradability

Soil degradation (days) (aerobic)

DT₅₀ (typical)

2.87

Non-persistent

DT₅₀ (lab at 20 °C)

2.87

Non-persistent

DT₅₀ (field)

15.6

Non-persistent

DT₉₀ (lab at 20 °C)

5.7

Non-persistent

DT₉₀ (field)

DT₅₀ modelling endpoint

Note

EU 2016 Dossier lab studies DT₅₀ range 1.2-25.1 days, DT₉₀ range 6.2-75 days, Soils=5; 2002 EU dossier lab studies DT₅₀ range 1-2 days, DT₉₀ range 4-7.3 days; field studies DT₅₀ 7.2-24 days (warm conditions)

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

17.2

Slow

Note

Variable with pH: 6.3 days at pH 5, 6.9 days at pH 9

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

Value

Stable

Note

Stable between pH 5 and pH 9

Water-sediment DT₅₀ (days)

Fast

Water phase only DT₅₀ (days)

12.5

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)

Moderately mobile

K_oc (mL g⁻¹)

224

Notes and range

Other sources: 440 mL g⁻¹ (DW4)

Freundlich

K_f (mL g⁻¹)

6.03

Moderately mobile

K_foc (mL g⁻¹)

392.9

¹/_n

0.80

Notes and range

EU 2016 dossier K_f range 0.46-18.3 mL g⁻¹, K_foc range 37.8-1306 mL g⁻¹, ¹/_n range 0.65-0.95, Soils=7

pH sensitivity

Adsorption decreases with increasing pH

Fate indices

Property

Value

Source; quality score; and other information

Interpretation

GUS leaching potential index

1.68

Calculated

Low leachability

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

Value

3.85 X 10^-02

Calculated

Note

Potential for particle bound transport index

Low

Calculated

Potential for loss via drain flow

Moderately mobile

Calculated

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

Bio-concentration factor

BCF (l kg⁻¹)

175

May bioaccumulate but low risk due to usage

Threshold for concern

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-D (Ref: L 208)

Major fraction

0.261

2,4-dichlorophenol

Major fraction

0.112

Known groundwater metabolites

None

Other known metabolites

Metabolite name and reference

Aliases

Formation medium / Rate

Estimated maximum occurrence fraction

2,3,7,8-tetrachlorodibenzo[b,e]{1,4]dioxine

TCDD

N-[4-(2,4-dichlorophenoxy)butanoyl]glycine

2,4-DB glycine

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

2,5-Cl-4-HPBA

(2,4-dichloro-6-hydroxyphenoxy)acteic acid

2,4-Cl-6-HPAA

methyl 4-(2,4-dichlorophenoxy)butanoate

2,4-DB-methyl ester

(4-chlorophenoxy)acetic acid

4-CPA

ECOTOXICOLOGY

Terrestrial ecotoxicology

Property

Value

Source; quality score; and other information

Interpretation

Mammals - Acute oral LD₅₀ (mg kg⁻¹)

1470

Rat

Moderate

Mammals - Short term dietary NOEL

(mg kg⁻¹)

Rat 28 day

High

(ppm diet)

300

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

22.5

Unknown species Reproductive NOAEL

Moderate

Birds - Acute LD₅₀ (mg kg⁻¹)

1545

Colinus virginianus

Moderate

Birds - Short term dietary (LC₅₀/LD₅₀)

> 5000 mg kg feed⁻¹

Colinus virginianus

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

101

Colinus virginianus NOEC

Moderate

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

> 1000

Eisenia foetida

Low

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

Eisenia foetida 56 day

Moderate

Soil micro-organisms

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

Dose: 1.8 kg ha⁻¹

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)

> 100

Apis mellifera

Low

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

> 100

Apis mellifera

Low

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) as Mortality LR₅₀ g ha⁻¹

> 1800

Chrysoperla carnea

Beneficial insects (Parasitic wasps) as Mortality LR₅₀ g ha⁻¹

> 1800

Aphidius rhopalosiphi

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

> 1800

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)

3.5

Oncorhynchus mykiss

Moderate

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

63.4

Pimephales promelas 32 day

Low

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

4,79

Danio rerio

Low

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

Daphnia magna

Moderate

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

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)

32.5

Chironomus riparius

Low

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

24.6

Chironomus riparius

Moderate

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

68.8

Lemna minor 7 day

Low

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

> 1.1

Raphidocelis subcapitata 120 hr

Moderate

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

67.9

Unknown species

Low

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)

1470

Rat

Moderate

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

2000

Rat

Mammals - Inhalation LC₅₀ (mg l⁻¹)

> 2.3

Rat 4 hr (whole body)

Other Mammal toxicity endpoints

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

0.02

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

0.3

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

Dermal penetration studies (%)

1.1

Dangerous Substances Directive 76/464

Exposure Routes

Public

Unlikely via food or water,
Source: US EPA/EU
No risk to consumers via acute residue

Occupational

Possible dermal or inhalation exposure during mixing/loading,
Source: US EPA

MRLs

European

EU MRL pesticide database

Great Britain

GB MRL Register

Notes

MRL's scheduled for review 2024

Drinking Water Standards

Non-statutory WHO drinking water guideline 0.09 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

; ; ; ;

Reproduction / development effects

Acetyl cholinesterase inhibitor

Neurotoxicant

Respiratory tract irritant

Skin irritant

Skin sensitiser

Eye irritant

Phototoxicant

General human health issues

Possible kidney toxicant

Handling issues

Property

Value and interpretation

General

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

CLP classification 2013

Health: H302
Environment: H411

WHO Classification

II (Moderately hazardous)

UN Number

UN3077

Waste disposal & packaging

Packaging Group III (minor danger)

Shelf-life, storage, stability and reactivity

TRANSLATIONS

Language

Name

English

2,4-DB

French

2,4-DB

German

2,4-DB

Danish

2,4-DB

Italian

2,4-DB

Spanish

2,4-DB

Greek

2,4-DB

Polish

2,4-DB

Swedish

2,4-DB

Hungarian

2,4-DB

Dutch

2,4-DB

Norwegian

Record last updated:	29/08/2024
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