Acetochlor (Ref: CP 55097)

Acetochlor (Ref: CP 55097)	Last updated: 26/05/2025
(Also known as: ICIA-5676; acetochlore; R0 25538; MON 097)

SUMMARY

Acetochlor is a herbicide forr the control of grasses and some broadleaved weeds. It is moderately soluble in water and is quite volatile. Based on its chemical properties it would not be expected to leach to groundwater. It is not persistence in soil systems but may be very persistent in aquatic systems under certain conditions. It has a high mammalian toxicity and it has a low potential for bioaccumulation. It is a known mutagen and may cause undesirable reproduction/development effects. Acetochlor is a recognised irritant and skin sensitizer. Acetochlor is moderately toxic to birds, honeybees, earthworms and most aquatic organisms however it is highly toxic to algae.

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; Fish acute ecotoxicity: Moderate; Fish chronic ecotoxicity: Moderate; Daphnia acute ecotoxicity: Moderate; Daphnia chronic ecotoxicity: Moderate; Earthworms acute ecotoxicity: Moderate	Human health High alert: Genotoxic; Endocrine disrupter; Reproduction/development effects

GENERAL INFORMATION

Description

A chloroacetanilide herbicide used mainly pre-emergence or pre-planting to control annual grasses and some broadleaved weeds

Example pests controlled

Annual grasses including feathertop chloris, goosegrass, sweet buffalo grass and crab grass; Certain Broadleaved weeds including morning glory, marigold, pigweed and cocklebur; Yellow nutsedge

Example applications

Vegetables including cabbage, peas and onions; Fruit including citrus, apples, pears, plums, apricots; Coffee; Corn; Sugarbeet; Sugarcane; Potatoes

Efficacy & activity

Availability status

Current

Introduction & key dates

circa 1985, first introduced; 1994, first registered in USA

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

Spain

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

USA

Chemical structure

Isomerism

None

Chemical formula

C₁₄H₂₀ClNO₂

Canonical SMILES

CCC1=CC=CC(=C1N(COCC)C(=O)CCl)C

Isomeric SMILES

International Chemical Identifier key (InChIKey)

VTNQPKFIQCLBDU-UHFFFAOYSA-N

International Chemical Identifier (InChI)

InChI=1S/C14H20ClNO2/c1-4-12-8-6-7-11(3)14(12)16(10-18-5-2)13(17)9-15/h6-8H,4-5,9-10H2,1-3H3

2D structure diagram/image available?

Yes

General status

Pesticide type

Herbicide

Substance groups

Chloroacetanilide herbicide

Minimum active substance purity

940 g kg⁻¹

Known relevant impurities

EU DAR dossier - Ethyl chloroacetate 6 g kg⁻¹; 2-ethyl-6-methylaniline 3 g kg⁻¹

Substance origin

Synthetic

Mode of action

Selective, absorbed mainly by shoots and roots of germinating weeds. Inhibition of very long chain fatty acids (VLCFA, inhibition of cell division)

CAS RN

34256-82-1

EC number

251-899-3

CIPAC number

496

US EPA chemical code

121601

PubChem CID

1988

CLP index number

616-037-00-6

Molecular mass

269.77

PIN (Preferred Identification Name)

2-chloro-N-(ethoxymethyl)-N-(2-ethyl-6-methylphenyl)acetamide

IUPAC name

2-chloro-N-ethoxymethyl-6'-ethylacet-o-toluidide

CAS name

2-chloro-N-(ethoxymethyl)-N-(2-ethyl-6-methylphenyl)acetamide

Other status information

Chemical subject to PIC regulations; PAN Bad Actor

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 liquid

Formulations

Property

Value

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

Monsanto
Dow Agrosciences

Example products using this active

Harness
Trophy
Trophee
Acenit
Guardian
Sacemid
Surpass

Formulation and application details

Usually supplied as an emulsifiable concentrate or capsule suspension that 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)

282

Moderate

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

5000000

Acetone

500000

Ethyl acetate

756000

Toluene

100000

Ethanol

Melting point (°C)

10.6

Boiling point (°C)

172

Degradation point (°C)

238

Flashpoint (°C)

160

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

1.38 X 10⁰⁴

Calculated

Log P

4.14

High

Fat solubility of residues

Solubility

Insoluble

Data type

Regulatory data

Density (g ml⁻¹)

1.12

Dissociation constant pKa) at 25 °C

Not applicable

No dissociation

Vapour pressure at 20 °C (mPa)

2.2 X 10^-02

Low volatility

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

2.1 X 10^-03

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 solution: 273nm = 448, 265nm = 538
Acid solution: 273nm = 466, 265nm = 552

Surface tension (mN m⁻¹)

46.3

20 °C

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)

10.6

Non-persistent

DT₅₀ (field)

12.1

Non-persistent

DT₉₀ (lab at 20 °C)

40.4

Moderately persistent

DT₉₀ (field)

40.2

DT₅₀ modelling endpoint

Note

EU dossier lab studies DT₅₀ range 3.4-29 days, DT₉₀ range 11.1-96.3 days; field studies DT₅₀ range 7-17 days, DT₉₀ range 23.3-56.5 days

Dissipation rate RL₅₀ (days) on plant matrix

Value

Note

Dissipation rate RL₅₀ (days) on and in plant matrix

Value

1.64

Note

Rice, whole plant, n=1

Aqueous photolysis DT₅₀ (days) at pH 7

Value

Stable

Note

Not a major route of degradation

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

Value

Stable

Note

Stable between pH 5 and pH 9

Water-sediment DT₅₀ (days)

19.7

Fast

Water phase only DT₅₀ (days)

40.5

Stable

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)

3.21

Moderately mobile

K_oc (mL g⁻¹)

156

Notes and range

EU dossier K_d range 0.13-17.0 mL g⁻¹, K_oc range 28-377 mL g⁻¹, Soils=10

Freundlich

K_f (mL g⁻¹)

4.50

Moderately mobile

K_foc (mL g⁻¹)

285

¹/_n

1.21

Notes and range

EU dossier kf range 0.37-20 mL g⁻¹, K_foc range 74.0-600 mL g⁻¹, ¹/_n range 0.79-2.16, Soils=13

pH sensitivity

Fate indices

Property

Value

Source; quality score; and other information

Interpretation

GUS leaching potential index

1.67

Calculated

Low leachability

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

Value

3.22 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

2.3

Calculated using the Atkinson method. Assumed 1.5E+06 OH/cm³, 12 hr

Below the level of concern for long-range air transport

Bio-concentration factor

BCF (l kg⁻¹)

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

t-sulfonic acid

Major fraction

0.118

t-oxanilic acid (Ref: MON 52766)

Major fraction

0.171

t-sulfinylacetic acid (Ref: MON 52709)

Major fraction

0.18

acetic acid

2-[(2-ethyl-6-methylphenyl)amino]-2-oxoethanesulfonic acid

N-(ethoxymethyl)-N-(2-ethyl-6-methylphenyl)acetamide

Known groundwater metabolites

Metabolite

EC SANCO/221/2000 relevancy

ADI (mg kg⁻¹ bodyweight day⁻¹)

WHO drinking water guidance value (μg L⁻¹ day⁻¹)

t-sulfonic acid

Relevant

0.25

1500

t-sulfinylacetic acid (Ref: MON 52709)

Relevant

0.29

1740

t-oxanilic acid (Ref: MON 52766)

Relevant

0.25

1500

s-sulfonic acid

Relevant

0.25

1500

t-norchloro acetochlor

Relevant

Other known metabolites

Metabolite name and reference

Aliases

Formation medium / Rate

Estimated maximum occurrence fraction

2-[(2-ethyl-6-methylphenyl)amino]-2-oxoethanesulfonic acid
Note: EFSA, 2011

acetochlor M13; s-sulfonic acid

Surface water

N-(ethoxymethyl)-N-(2-ethyl-6-methylphenyl)acetamide
Note: EFSA, 2011

acetochlor M06; t-norchloroacetochlor

Surface water; Sediment

t-oxanilic acid (Ref: MON 52766)
Note: EFSA, 2011

Surface water

t-sulfinylacetic acid (Ref: MON 52709)
Note: EFSA, 2011

Surface water

t-sulfonic acid
Note: EFSA, 2011

Surface water

ECOTOXICOLOGY

Terrestrial ecotoxicology

Property

Value

Source; quality score; and other information

Interpretation

Mammals - Acute oral LD₅₀ (mg kg⁻¹)

1929

Rat

Moderate

Mammals - Short term dietary NOEL

(mg kg⁻¹)

> 10

Rat

High

(ppm diet)

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

Birds - Acute LD₅₀ (mg kg⁻¹)

928

Colinus virginianus

Moderate

Birds - Short term dietary (LC₅₀/LD₅₀)

1057 mg kg bw⁻¹ day⁻¹

Anas platyrhynchos

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

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

105.5

Eisenia foetida corr

Moderate

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

Soil micro-organisms

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

Dose: maximum field rate 100 Day

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)

> 200

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

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)

0% Mortality at 2000 g ha⁻¹

Chrysoperla carnea

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

1.56

Aphidius rhopalosiphi

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

831

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)

0.36

Oncorhynchus mykiss

Moderate

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

0.13

Oncorhynchus mykiss

Moderate

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

3.35

Danio rerio

Moderate

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

8.3

Daphnia magna

Moderate

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

0.022

Daphnia magna

Moderate

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

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

1.9

Americamysis bahia

Moderate

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

Sediment dwelling organisms - Chronic 28 day NOEC, static, water (mg l⁻¹)

1.6

Chironomus riparius

Moderate

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

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

0.0027

Lemna gibba

High

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

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

0.0036

Pseudokirchneriella subcapitata

High

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

0.00059

Selenastrum capricornutum

High

Mesocosm study data

NOEAEC mg l⁻¹

0.002

lotic systems

NOEAEC mg l⁻¹

Marine bivalves – Acute EC₅₀ (mg l⁻¹)

> 7.2

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)

1929

Rat

Moderate

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

2000

Rat

Mammals - Inhalation LC₅₀ (mg l⁻¹)

3.99

Rat 4 hr (nose only)

Other Mammal toxicity endpoints

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

0.0036

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

1.5

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 (%)

0.05-50

concentration dependent

Dangerous Substances Directive 76/464

Exposure Routes

Public

Minimal risk from any route
Source: US EPA

Occupational

Dermal absorption possible during handling

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

Excreted mainly in the urine and bile.

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

Slightly toxic
Possible thyroid, liver and kidney toxicant
US EPA - Likely to be a human carcinogen
Endocrine issues - Interaction with uterine estrogen receptors

Handling issues

Property

Value and interpretation

General

Avoid generation of dusts
IMDG Transport Hazard Class 9
Not explosive or oxidising
Flammable liquid

CLP classification 2013

Health: H315, H317, H332, H335
Environment: H400, H410

WHO Classification

III (Slightly hazardous)

UN Number

UN3082

Waste disposal & packaging

Packaging Group III (minor danger)

Shelf-life, storage, stability and reactivity

TRANSLATIONS

Language

Name

English

acetochlor

French

acetochlore

German

Acetochlor

Danish

acetochlor

Italian

acetoclor

Spanish

acetoclor

Greek

Polish

acetochlor

Swedish

Hungarian

acetoklor

Dutch

Norwegian

Record last updated:	26/05/2025
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