MCPA-thioethyl

MCPA-thioethyl	Last updated: 26/05/2025
(Also known as: phenothiol)

SUMMARY

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: Drainflow: Mobile	Ecotoxicity High alert: Fish acute ecotoxicity: High; Daphnia chronic ecotoxicity: High	Human health Moderate alert: Mammals acute toxicity: Moderate; Reproduction/development effects

GENERAL INFORMATION

Description

A phenoxy plant growth regulator used to suppress broadleaved weeds in various crops, mainly in orchards and citrus groves

Example pests controlled

Broadleaved weeds

Example applications

Citrus; Orchards; Fruit groves

Efficacy & activity

Availability status

Current

Introduction & key dates

1973, introduced

GB regulatory status

GB COPR regulatory status

Approved

Date COPR inclusion expires

31/10/2029

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

Poland/Netherlands

Date EC 1107/2009 inclusion expires

15/08/2026

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

Morocco

Chemical structure

Isomerism

None

Chemical formula

C₁₁H₁₃ClO₂S

Canonical SMILES

CCSC(=O)COC1=C(C=C(C=C1)Cl)C

Isomeric SMILES

International Chemical Identifier key (InChIKey)

AZFKQCNGMSSWDS-UHFFFAOYSA-N

International Chemical Identifier (InChI)

InChI=1S/C11H13ClO2S/c1-3-15-11(13)7-14-10-5-4-9(12)6-8(10)2/h4-6H,3,7H2,1-2H3

2D structure diagram/image available?

Yes

Cambridge Crystallographic Data Centre diagrams

Common Name	Relationship	Link
MCPA	Parent

General status

Pesticide type

Herbicide; Plant Growth Regulator

Substance groups

Aryloxyalkanoic acid herbicide; Phenoxyacetic herbicide

Minimum active substance purity

955 g kg⁻¹

Known relevant impurities

EU 2022 dossier - None declared

Substance origin

Synthetic

Mode of action

Selective, systemic with translocation. Synthetic auxin.

CAS RN

25319-90-8

EC number

246-831-4

CIPAC number

US EPA chemical code

431500

PubChem CID

32876

CLP index number

607-051-00-3

Molecular mass

244.74

PIN (Preferred Identification Name)

S-ethyl (4-chloro-2-methylphenoxy)ethanethioate

IUPAC name

S-ethyl 4-chloro-o-tolyloxythioacetate

CAS name

S-ethyl (4-chloro-2-methylphenoxy)ethanethioate

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 crystalline solid

Related substances & organisms

MCPA

MCPA-butyl

MCPA-ethyl

MCPA-isopropyl

Formulations

Property

Value

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

Sipcam Inagra S.A.

Example products using this active

Fengib 20% EC
HF Calibra

Formulation and application details

Often supplied as soluble concentrate 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)

2.28

Low

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

1000000

Acetone

144000

Methanol

1000000

Ethyl acetate

1000000

Xylene

Melting point (°C)

41.5

Boiling point (°C)

Degradation point (°C)

280

Flashpoint (°C)

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

2.82 X 10⁰⁴

Calculated

Log P

4.45

High

Fat solubility of residues

Solubility

Insoluble

Data type

Regulatory data - observed in metabolism and farm animal feeding studies

Density (g ml⁻¹)

1.291

Dissociation constant pKa) at 25 °C

Not applicable

No dissociation

Vapour pressure at 20 °C (mPa)

0.13

at 25 °C

Low volatility. If applied directly to plants, drift is a concern & mitigation is advisable

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

0.2102

Moderately volatile

Volatilisation as max % of applied dose lost

From plant surface

From soil surface

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

No absorption >290nm

Surface tension (mN m⁻¹)

Degradation

Property

Value

Source; quality score; and other information

Interpretation

General biodegradability

Not readily biodegradable

Soil degradation (days) (aerobic)

DT₅₀ (typical)

0.08

Non-persistent

DT₅₀ (lab at 20 °C)

0.08

Non-persistent

DT₅₀ (field)

DT₉₀ (lab at 20 °C)

1.03

Non-persistent

DT₉₀ (field)

DT₅₀ modelling endpoint

Note

EU 2022 dossier, Lab studies DT₅₀ (normalised) range 0.013-0.699 days, DT₉₀ (measured) range 0.044-2.788 days, Soils= 3

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

Moderately fast

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)

Mobile

K_oc (mL g⁻¹)

Notes and range

EU dossier value for MCPA

Freundlich

K_f (mL g⁻¹)

61.61

Slightly mobile

K_foc (mL g⁻¹)

3430

¹/_n

0.950

Notes and range

EU Dossier K_f range 25.68-146.46 mL g⁻¹, K_foc range 2855-3981 mL g⁻¹, ¹/_n range 0.928-0.972, Soils=5

pH sensitivity

Fate indices

Property

Value

Source; quality score; and other information

Interpretation

GUS leaching potential index

-0.51

Calculated

Low leachability

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

Value

4.62 X 10^-07

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)

CT₅₀ (days)

Known soil metabolites

Metabolite

Major/Minor fraction

$Click here for further information on Major/Minor fraction$

Estimated maximum occurrence fraction

Notes

MCPA (Ref: BAS 009H)

Major fraction

0.857

4-chloro 2-methylphenol

Major fraction

0.198

Known groundwater metabolites

None

Other known metabolites

None

ECOTOXICOLOGY

Terrestrial ecotoxicology

Property

Value

Source; quality score; and other information

Interpretation

Mammals - Acute oral LD₅₀ (mg kg⁻¹)

450

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)

> 400

Colinus virginianus

Moderate

Birds - Short term dietary (LC₅₀/LD₅₀)

> 1040 mg kg feed⁻¹

Colinus virginianus

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

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

140.5

Moderate

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

9.8

Eisenia andrei corr

Moderate

Soil micro-organisms

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

Dose: 1.224 kg ha⁻¹ 28 Day

Collembola

Acute LC₅₀ (mg kg⁻¹)

Chronic NOEC (mg kg⁻¹)

0.265

Folsomia candida corr

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 10 day LD₅₀ as µg bee⁻¹ day⁻¹

87.42

Apis mellifera

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)

0.085

Oncorhynchus mykiss

High

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

0.2

Salmo gairdneri

Moderate

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

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

0.131

Daphnia magna

Moderate

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

0.009

Daphnia magna

High

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)

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

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

> 1.593

Lemna gibba

Moderate

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

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

> 2.3

Scenedesmus subspicatus

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)

450

Rat

Moderate

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

5000

Rat

Mammals - Inhalation LC₅₀ (mg l⁻¹)

> 5.38

Rat 4 hr (aerosol)

Other Mammal toxicity endpoints

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

0.05

as MCPA

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

0.15

as MCPA

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

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

0.04

as MCPA

Dermal penetration studies (%)

Dangerous Substances Directive 76/464

List II as MCPA

Exposure Routes

Public

Occupational

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 as MCPA almost complete in urine

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

Highly toxic
Possible kidney, liver & blood toxicant

Handling issues

Property

Value and interpretation

General

Not explosive or oxidising
IMDG Transport Hazard Class 6.1

CLP classification 2013

Health: H302, H373
Environment: H400, H410

WHO Classification

II (Moderately hazardous)

UN Number

UN3345

Waste disposal & packaging

Packaging Group III (minor danger)

Shelf-life, storage, stability and reactivity

TRANSLATIONS

Language

Name

English

MCPA-thioethyl

French

German

Danish

Italian

Spanish

Greek

Polish

MCPA tioetyl

Swedish

Hungarian

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