Coumaphos (Ref: OMS 485)

Coumaphos (Ref: OMS 485)	Last updated: 15/09/2025
(Also known as: counafosum; coumafos; cumafos; ENT 17957)

GENERAL INFORMATION

Description

An organophosphate insecticide used for control of a wide variety of livestock insects

Examples of veterinary uses

Used to control cattle grubs, screw-worms, lice, scabies, flies, and ticks

Examples of species treated

Sheep; Goats; Cattle; Horses; Pigs; Poultry

Approval status

VMR 2013/2033 approval status (GB/UK)

Not approved

EU Regulatory approval status

Not approved

Chemical structure

Isomerism

An organophosphate insecticide used for control of a wide variety of livestock insects

Chemical formula

C₁₄H₁₆ClO₅PS

Canonical SMILES

CCOP(=S)(OCC)OC1=CC2=C(C=C1)C(=C(C(=O)O2)Cl)C

Isomeric SMILES

No data

International Chemical Identifier key (InChIKey)

BXNANOICGRISHX-UHFFFAOYSA-N

International Chemical Identifier (InChI)

InChI=1S/C14H16ClO5PS/c1-4-17-21(22,18-5-2)20-10-6-7-11-9(3)13(15)14(16)19-12(11)8-10/h6-8H,4-5H2,1-3H3

2D structure diagram/image available?

Yes

General status

Veterinary substance type

Antiparasitic, Insecticide, Acaricide, Anthelmintic, Ectoparasiticide

Substance groups

Organophosphate veterinary substance; Organothiophosphate veterinary substance

Minimum active substance purity

Known relevant impurities

Substance origin

Synthetic

Mode of action

Non-systemic, Acetylcholinesterase (AChE) inhibitor.

Molecular targets

[Cholinesterase, Inhibitor]

CAS RN

56-72-4

EC number

200-285-3

CIPAC number

121

US EPA chemical code

036501

PubChem CID

Therapeutic Class

Antiparasitic products, insecticides & repellents: Ecoparasiticides, insecticides & repellents

ATCvet Code

QP53AF08

Controlled Drug?

Regulation 37/2010 MRL Classification

Allowed substance (Table 1: Bees]

Molecular mass

362.77

PIN (Preferred Identification Name)

IUPAC name

O-3-chloro-4-methyl-2-oxo-2H-chromen-7-yl O,O-diethyl phosphorothioate

CAS name

O-(3-chloro-4-methyl-2-oxo-2H-1-benzopyran-7-yl) O,O-diethyl phosphorothioate

Forever chemical

Other status information

Relevant Environmental Water Quality Standards

UK Environment Agency non-statutory standard for the protection of freshwater and saltwater aquatic life: 0.03 µg l⁻¹ as annual average; 0.1 µg l⁻¹ as max acceptable conc.

Physical state

Tan crystalline solid

Commercial

Property

Value

Availability status

Current

Introduction & key dates

Circa 1953, introduced

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

Bayer Healthcare
Bayer Animal Health
Y-Tex Corp

Example products using this active

Resitox
Muscatox
Baymix
Asuntol

Formulation and application details

Usually supplied as pour-ons, sprays and dips for topical use

Commercial production

The production of coumaphos typically involves the esterification of 3-chloro-4-methyl-7-hydroxycoumarin with diethyl chlorothiophosphate. One efficient method uses an aqueous-phase reaction, where the coumarin derivative is combined with an acid-binding agent and a phase-transfer catalyst, then reacted with diethyl chlorothiophosphate under controlled temperatures, usually between 50–80 DegC for 20 to 150 minutes. After the reaction, the mixture is filtered, washed to neutrality, and dried to yield coumaphos as a crystalline product.

Impact on climate of production and use

Data for the amount of life cycle GHGs produced by coumaphos are not available in the public domain. However, whilst estimates vary, more general data suggests that between 14 and 19 kilograms of CO₂e is emitted per kilogram of insecticide produced.

ENVIRONMENTAL FATE

Property

Value

Source; quality score; and other information

Interpretation

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

1.5

Low

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

238200

Acetone

900

Xylene

130

Octanol

63900

Methylene chloride

Melting point (°C)

Boiling point (°C)

Degradation point (°C)

Flashpoint (°C)

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

7.24 X 10⁰³

Calculated

Log P

3.86

High

Fat solubility of residues

Solubility

Data type

Density (g ml⁻¹)

1.38

Dissociation constant pKa) at 25 °C

Vapour pressure at 20 °C (mPa)

0.000013

Low volatility

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

0.011

Estimated

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)

Refractive Index

Environmental release

Degradation

Property

Value

Source; quality score; and other information

Interpretation

Soil degradation (days) (aerobic)

DT₅₀ (typical)

152

Persistent

DT₅₀ (lab at 20 °C)

DT₅₀ (field)

DT₉₀ (lab at 20 °C)

DT₉₀ (field)

Note

General literature gives DT₅₀ between 100-300 days (R4)

Manure DT₅₀ (days)

Aqueous photolysis DT₅₀ (days) at pH 7

Value

Note

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

Value

Stable

Note

Not sensitive to pH

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)

Non-mobile

K_oc (mL g⁻¹)

18000

Notes and range

Other literature values range 5778-21120 mL g⁻¹ (R3)

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

-0.56

Calculated

Low leachability

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

chlorferon

O,O-diethyl phosphorothionate (Ref: DETP)

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)

7.1

Rat

High

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)

29.4

Anas platyrhynchos

High

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

Vegetative vigour ER₅₀ (g ha⁻¹)

Seedling emergence ER₅₀ (g ha⁻¹)

Honeybees (Apis spp.)

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

Apis mellifera

Moderate

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

4.6

Apis mellifera

Moderate

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

> 25

Moderate

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)

0.55

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)

0.0001

Daphnia magna

High

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

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, fonds growth, fresh) - 7 day (mg l⁻¹)

Aquatic plants (rooted, growth rate, fresh) - 14 day (mg l⁻¹)

Algae - Acute (growth rate, fresh; mg l⁻¹)

Algae - Chronic (growth rate, fresh; 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)

7.1

Rat

High

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

860

Rat

Mammals - Inhalation LC₅₀ (mg l⁻¹)

0.341

Rat

Other Mammal toxicity endpoints

Intraperitoneal LD₅₀ = 7.5 mg kg⁻¹

Rat

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

None allocated

JMPR 1990

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

List I

Exposure Routes

Public

Occupational

Occupational exposure may occur through inhalation of spray mists and dermal contact

Mammalian dose elimination route and rate

In rats excretion is rapid largely unmetabolised

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

May cause seizures, incontinence, respiratory depression, loss of consciousness
Harmful if swallowed, inhaled or absorbed through the skin

Handling issues

Property

Value and interpretation

General

Prevent generation of dust
IMDG Transport Hazard Class 6.1

CLP classification 2013

Health: H300, H312
Environment: H400, H410

WHO Classification

Ib (Highly hazardous)

UN Number

UN2783

Waste disposal & packaging

Shelf-life, storage, stability and reactivity

TRANSLATIONS

Language

Name

English

coumaphos

French

coumaphos

German

Coumaphos

Danish

coumaphos

Italian

cumafos

Spanish

cumafos

Greek

coumaphos

Polish

kumafos

Swedish

Hungarian

Dutch

cumafos

Norwegian

Record last updated:	15/09/2025
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