Diclofop (Ref: AE F021079)

Diclofop (Ref: AE F021079)	Last updated: 05/02/2024
(Also known as: diclofop acid; diclofop free acid; HOE 021079)

SUMMARY

Diclofop is a grass herbicide which is usually used as the methyl variant. It is highly soluble in water and is not considered to be volatile. It is not normally environmentally persistent. Diclofop is moderately toxic to mammals via the oral route. Its toxicity to biodiversity tends to be moderate to low.

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: Moderately persistent; GUS: Transition state; Drainflow: Moderately mobile	Ecotoxicity Moderate alert: Daphnia acute ecotoxicity: Moderate; Daphnia chronic ecotoxicity: Moderate; Earthworms acute ecotoxicity: Moderate; Earthworms chronic ecotoxicity: Moderate	Human health Moderate alert: Mammals acute toxicity: Moderate; Possible Carcinogen; Reproduction/development effects

GENERAL INFORMATION

Description

Post-emergence herbicide usually used as the methyl variant. Also a pesticide transformation product

Example pests controlled

Wild oats; Crowsfoot grass; Annual ryegrass; Common barbgrass

Example applications

Vegetables including brassicas, beans, carrots, peas, parsnips, onions; Sugarbeet; Cereals including barley, wheat; Oilseed rape; Potatoes

Efficacy & activity

Availability status

Current

Introduction & key dates

circa 1982, introduced

UK regulatory status

UK COPR regulatory status

Approved

Date COPR inclusion expires

31/05/2026

UK LERAP status

None

EC Regulation 1107/2009 (repealing 91/414)

EC Regulation 1107/2009 status

Approved

Dossier rapporteur/co-rapporteur

Portugal/France

Date EC 1107/2009 inclusion expires

31/08/2026

EU Candidate for substitution (CfS)

Yes - low ADI / ARfD / AOEL

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

A chiral molecule. Substance is racemic.

Chemical formula

C₁₅H₁₂Cl₂O₄

Canonical SMILES

CC(C(=O)O)OC1=CC=C(C=C1)OC2=C(C=C(C=C2)Cl)Cl

Isomeric SMILES

International Chemical Identifier key (InChIKey)

OOLBCHYXZDXLDS-UHFFFAOYSA-N

International Chemical Identifier (InChI)

InChI=1S/C15H12Cl2O4/c1-9(15(18)19)20-11-3-5-12(6-4-11)21-14-7-2-10(16)8-13(14)17/h2-9H,1H3,(H,18,19)

2D structure diagram/image available?

Yes

Cambridge Crystallographic Data Centre diagrams

Common Name	Relationship	Link
diclofop-methyl	Variant

General status

Pesticide type

Herbicide, Metabolite

Metabolite Type

Soil

Substance groups

Aryloxyphenoxypropionate herbicide

Minimum active substance purity

930 g kg⁻¹

Known relevant impurities

EU dossier - None declared

Substance origin

Synthetic

Mode of action

Selective, absorbed by leaves and inhibits fatty acid synthesis. Inhibition of acetyl CoA carboxylase (ACCase)

CAS RN

40843-25-2

EC number

No data found

CIPAC number

358

US EPA chemical code

110902

PubChem CID

38687

CLP index number

607-165-00-3

Molecular mass

327.16

PIN (Preferred Identification Name)

rac-(2R)-2-[4-(2,4-dichlorophenoxy)phenoxy]propanoic acid

IUPAC name

(RS)-2-[4-(2,4-dichlorophenoxy)phenoxy]propionic acid

CAS name

2-[4-(2,4-dichlorophenoxy)phenoxy]propanoic 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

Pale yellow solid

Related substances & organisms

diclofop-phenol

diclofop-methyl

Can be a metabolite of:

Parent

Formation medium

Estimated maximum occurrence fraction

1107/2009 relevancy

diclofop-methyl

Soil

0.87

Major fraction

Formulations

Property

Value

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

Bayer CropScience
Bayer Environmental

Example products using this active

Hoe-Grass
Hoelon 3EC
Illoxan
One-shot

Formulation and application details

Usually supplied as an emulsion 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)

122700

High

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

Melting point (°C)

Boiling point (°C)

Degradation point (°C)

Flashpoint (°C)

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

4.07 X 10⁰¹

Calculated

Log P

1.61

Low

Fat solubility of residues

Solubility

Data type

Density (g ml⁻¹)

1.4

Dissociation constant pKa) at 25 °C

3.43

Weak acid

Vapour pressure at 20 °C (mPa)

2.5 X 10^-03

Low volatility

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

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)

Non-persistent

DT₅₀ (lab at 20 °C)

23.9

Non-persistent

DT₅₀ (field)

35.2

Moderately persistent

DT₉₀ (lab at 20 °C)

84.7

Moderately persistent

DT₉₀ (field)

DT₅₀ modelling endpoint

Note

EU dossier lab studies DT₅₀ range 5.1-74.0 days, DT₉₀ range 23.3-246 days, Field studies DT₅₀ range 25.7-52.2 days ; General literature DT₅₀ range 10 days (sand) - 30 days (sandy clay)

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)

58.3

Moderately fast

Water 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.

Soil adsorption and mobility

Property

Value

Source; quality score; and other information

Interpretation

Linear

K_d

K_oc

Notes and range

Freundlich

K_f

6.3

Moderately mobile

K_foc

289

¹/_n

0.882

Notes and range

EU dossier kf range 0.76-13.54 mL g⁻¹, kfoc range 148-505.5 mL g⁻¹, ¹/_n range 0.819-0.913, Soils=6

pH sensitivity

Yes

Fate indices

Property

Value

Source; quality score; and other information

Interpretation

GUS leaching potential index

2.38

Calculated

Transition state

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

Value

1.24 X 10^-01

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)

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)

> 586

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)

> 10000

Phasianidae

Low

Birds - Short term dietary (LC₅₀/LD₅₀)

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

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

> 500

Eisenia foetida corr

Moderate

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

Eisenia foetida corr

Moderate

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)

> 100

as methyl variant

Low

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

> 131

as methyl variant

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)

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)

> 100

Oncorhynchus mykiss

Low

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

16.0

Oncorhynchus mykiss

Low

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

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)

0.0156

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)

Chironomus riparius

Moderate

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

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

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

10.4

Pseudokirchneriella subcapitata

Low

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

Mesocosm study data

NOEAEC mg l⁻¹

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)

> 586

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)

0.001

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

0.03

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

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

0.003

Dermal penetration studies (%)

Dangerous Substances Directive 76/464

Exposure Routes

Public

Occupational

Readily absorbed through the gastrointestinal tract

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

; ; ; ;

No data found

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

Kidney and liver toxicant, CLP data - diclofop-methyl is classified as a likely human carcinogen

Handling issues

Property

Value and interpretation

General

Not explosive or oxidising

CLP classification 2013

Health: H302, H317
Environment: H400, H410

WHO Classification

II (Moderately hazardous)

UN Number

Waste disposal & packaging

Shelf-life, storage, stability and reactivity

TRANSLATIONS

Language

Name

English

diclofop

French

German

Danish

Italian

Spanish

Greek

Polish

dichlofop

Swedish

Hungarian

Dutch

Norwegian

Record last updated:	05/02/2024
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