Trichlorfon (Ref: OMS 800)

Trichlorfon (Ref: OMS 800)	Last updated: 04/09/2025
(Also known as: chlorophos; metriphonate; trichlorphon; dipterex; chloroxyphos)

GENERAL INFORMATION

Description

An organophosphate substance with acaricidal and anthelmintic properties

Examples of veterinary uses

Used for the control of endo- and ectoparasites in and on animals of various species

Examples of species treated

Cattle; Horses

Approval status

VMR 2013/2033 approval status (GB/UK)

Not approved

EU Regulatory approval status

Not approved

Chemical structure

Isomerism

Trichlorfon exhibits chiral isomerism, meaning it exists as a mixture of two enantiomers due to the presence of a stereocentre in its molecular structure. The technical-grade material used in commercial applications is typically an isomeric mixture.

Chemical formula

C₄H₈Cl₃O₄P

Canonical SMILES

COP(=O)(C(C(Cl)(Cl)Cl)O)OC

Isomeric SMILES

No data

International Chemical Identifier key (InChIKey)

NFACJZMKEDPNKN-UHFFFAOYSA-N

International Chemical Identifier (InChI)

InChI=1S/C4H8Cl3O4P/c1-10-12(9,11-2)3(8)4(5,6)7/h3,8H,1-2H3

2D structure diagram/image available?

Yes

Cambridge Crystallographic Data Centre diagrams

Common Name	Relationship	Link
trichlorfon	Unstated isomer

General status

Veterinary substance type

Insecticide, Antiparasitic, Anthelmintic

Substance groups

Organophosphate insecticide; Organophosphate acaricide; Phosphonate acaricide; Phosphonate insecticide

Minimum active substance purity

980 g kg⁻¹

Known relevant impurities

EU dossier - diclorvos 0.02 g kg⁻¹

Substance origin

Synthetic

Mode of action

Non-systemic with contact and stomach action. Acetylcholinesterase (AChE) inhibitor.

Molecular targets

[Cholinesterase, Inhibitor]

CAS RN

52-68-6

EC number

200-149-3

CIPAC number

US EPA chemical code

057901

PubChem CID

5853

CLP index number

015-021-00-0

Therapeutic Class

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

ATCvet Code

QP52AB01; QP53AF02

Controlled Drug?

Regulation 37/2010 MRL Classification

Molecular mass

257.4

PIN (Preferred Identification Name)

rac-dimethyl [(1R)-2,2,2-trichloro-1-hydroxyethyl]phosphonate

IUPAC name

dimethyl (RS)-2,2,2-trichloro-1-hydroxyethylphosphonate

CAS name

dimethyl (2,2,2-trichloro-1-hydroxyethyl)phosphonate

Forever chemical

Other status information

Evidence of use in third world countries; Chemical subject to PIC regulations

Relevant Environmental Water Quality Standards

Physical state

Colourless to yellow or pink waxy solid

Commercial

Property

Value

Availability status

Current

Introduction & key dates

1990, first registered USA; 2007, withdraw EU

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

Bayer CropScience
Mobay
Makhteshim Agan

Example products using this active

Cekufon 80SP
Dylox
Nevugon
Cekufon
Danex

Formulation and application details

Available in a range of formulations including soluble powders, soluble concentrates, granules and spot-on sticks.

Commercial production

The commercial production of trichlorfon involves a chemical synthesis process that begins with the reaction between dimethyl hydrogen phosphite and chloral. The manufacturing process typically results in a chiral mixture of two isomers.

Impact on climate of production and use

Data for the amount of life cycle GHGs produced by trichlorfon 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)

120000

High

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

21500

Xylene

363000

Ethyl acetate

1346000

Methanol

707000

Acetone

Melting point (°C)

Boiling point (°C)

Decomposes before boiling

Degradation point (°C)

100

Flashpoint (°C)

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

2.69 X 10⁰⁰

Calculated

Log P

0.43

Low

Fat solubility of residues

Solubility

Data type

Density (g ml⁻¹)

1.68

Dissociation constant pKa) at 25 °C

Not applicable

Not determinable

Vapour pressure at 20 °C (mPa)

0.21

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)

4.50 X 10^-07

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)

71.8

at 20°C 99.3% 1g l⁻¹

Refractive Index

Environmental release

Degradation

Property

Value

Source; quality score; and other information

Interpretation

Soil degradation (days) (aerobic)

DT₅₀ (typical)

Non-persistent

DT₅₀ (lab at 20 °C)

Non-persistent

DT₅₀ (field)

DT₉₀ (lab at 20 °C)

DT₉₀ (field)

Note

Other sources: DT₅₀ 10 days (DW4); General literature DT₅₀ range 7-30 days (R2)

Manure DT₅₀ (days)

Aqueous photolysis DT₅₀ (days) at pH 7

Value

Stable

Note

No UV degradation

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

Value

1.6

Non-persistent

Note

pH sensitive: DT₅₀ 117 days at pH 5, 31 minutes at pH 9, all at 25 °C

Water-sediment DT₅₀ (days)

Water phase only DT₅₀ (days)

1.2

Moderately fast

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

[Apple (waxed): 22.8 days @ ambient conditions; Field data], [Apple (natural): 11.8 days @ ambient conditions; Field data]

Soil adsorption and mobility

Property

Value

Source; quality score; and other information

Interpretation

Linear

K_d (mL g⁻¹)

Very mobile

K_oc (mL g⁻¹)

Notes and range

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

3.77

Calculated

High leachability

Bio-concentration factor

BCF (l kg⁻¹)

0.41

Piaractus mesopotamicus Other data: Low risk LogP<3 (A5)

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

dichloroethanol

Minor fraction

0.044

dichlorvos (Ref: OMS 14)

Major fraction

0.245

desmethyl dichlorvos

Major fraction

0.376

dichlorivinyl phosphate

Major fraction

0.407

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)

dichlorvos (Ref: OMS 14)

Relevant

dichlorivinyl phosphate

Relevancy unknown

desmethyl dichlorvos

Relevancy unknown

Other known metabolites

None

ECOTOXICOLOGY

Terrestrial ecotoxicology

Property

Value

Source; quality score; and other information

Interpretation

Mammals - Acute oral LD₅₀ (mg kg⁻¹)

212

Rat

Moderate

Mammals - Short term dietary NOEL

(mg kg⁻¹)

> 4.5

Rat 2 yr

High

(ppm diet)

> 500

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

Birds - Acute LD₅₀ (mg kg⁻¹)

> 36.8

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

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

Dose: 7.2 kg ha⁻¹ 28 Day

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)

2.85

Apis mellifera

Moderate

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

> 0.4

Apis mellifera

High

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)

568.3

Bombus terricola

Low

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)

7.5

Megachile rotundata

Moderate

Mode of exposure

Contact

Other bee species (2)

Acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg insect⁻¹)

4.147

Andrena erythronii

Moderate

Mode of exposure

Contact

Beneficial insects (Ladybirds)

Beneficial insects (Lacewings) as Mortality, LD₅₀ ug/insect

> 91.1

Chrysoperla carnea Larva

Moderate

Beneficial insects (Parasitic wasps) as Mortality LR₅₀ g ha⁻¹ 48 hr, Std lab test

0.519

Aphidius rhopalosiphi

Moderate

Beneficial insects (Predatory mites) as Mortality LR40 g ha⁻¹, Std lab test

< 1200

Typhlodromus pyri Adult

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)

0.7

Oncorhynchus mykiss

Moderate

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

0.5

Carassius auratus 30 day

Moderate

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

16.99

Danio rerio Embryo 6 days

Moderate

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

0.00096

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) (120 hr EC₅₀)

Desmodesmus subspicatus

Moderate

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

3.2

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)

212

Rat

Moderate

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

5000

Rat

Mammals - Inhalation LC₅₀ (mg l⁻¹)

> 0.53

Rat

Other Mammal toxicity endpoints

Intraperitoneal LD₅₀ = 160 mg kg⁻¹

Rat

Intramuscular LD₅₀ = 395 mg kg⁻¹

Rat

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

0.045

Rat SF=100

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

0.1

Rat SF=100

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

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

0.09

Rat SF=500

Dermal penetration studies (%)

Dangerous Substances Directive 76/464

List I; List II

Exposure Routes

Public

Possible bystander risk from spray drift

Occupational

Risk of exposure acceptable under label recommendations for use for personal protection clothing and equipment

Mammalian dose elimination route and rate

Around 70% of the total dose administered to rats is eliminated in urine within 16 hrs

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

May cause pyrexia, cyanosis, pulmonary edema, loss of sphincter control, paralysis, coma and respiratory failure
IARC Group 3 carcinogen - not classifiable; US EPA - possible human carcinogen at high doses
Endocrine issues - alteration of thyroid function

Handling issues

Property

Value and interpretation

General

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

CLP classification 2013

Health: H302, H317
Environment: H400, H410

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

trichlorfon

French

trichlorfon

German

Trichlorfon

Danish

trichlorphon

Italian

triclorfon

Spanish

triclorfon

Greek

Polish

trichlorfon

Swedish

triklorfon

Hungarian

Dutch

Norwegian

Record last updated:	04/09/2025
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