Pyraclofos (Ref: OMS 3040)

Pyraclofos (Ref: OMS 3040)	Last updated: 04/09/2025
(Also known as: TIA 230)

GENERAL INFORMATION

Description

An obsolete organophosphate insecticide used for external and internal parasite control

Examples of veterinary uses

Substance used for eradicating parasites such as helminths, nematodes, ticks and others

Examples of species treated

Cattle; Horses; Sheep; Pigs; Poultry; Cats; Dogs

Approval status

VMR 2013/2033 approval status (GB/UK)

Not approved

EU Regulatory approval status

Not approved

Chemical structure

Isomerism

Pyraclofos exhibits stereoisomerism due to the presence of a chiral centre in its molecular structure. This chiral centre gives rise to two enantiomers: S-(+)-pyraclofos and R-(−)-pyraclofos.

Chemical formula

C₁₄H₁₈ClN₂O₃PS

Canonical SMILES

CCCSP(=O)(OCC)OC1=CN(N=C1)C2=CC=C(C=C2)Cl

Isomeric SMILES

No data

International Chemical Identifier key (InChIKey)

QHGVXILFMXYDRS-UHFFFAOYSA-N

International Chemical Identifier (InChI)

InChI=1S/C14H18ClN2O3PS/c1-3-9-22-21(18,19-4-2)20-14-10-16-17(11-14)13-7-5-12(15)6-8-13/h5-8,10-11H,3-4,9H2,1-2H3

2D structure diagram/image available?

Yes

General status

Veterinary substance type

Antiparasitic, Insecticide

Substance groups

Organophosphate insecticide; Orgnothiophosphate insecticide; Phenylpyrazole insecticide

Minimum active substance purity

Known relevant impurities

Substance origin

Synthetic

Mode of action

Respiratory, contact and stomach action. Acetylcholinesterase inhibitor.

Molecular targets

[Cholinesterase, Inhibitor]

CAS RN

89784-60-1

Alternative/old CAS RN

77458-01-6

EC number

618-301-6

CIPAC number

None allocated

US EPA chemical code

PubChem CID

93460

CLP index number

No data found

Therapeutic Class

ATCvet Code

None allocated

Controlled Drug?

Regulation 37/2010 MRL Classification

Molecular mass

360.8

PIN (Preferred Identification Name)

IUPAC name

(RS)-[O-1-(4-chlorophenyl)pyrazol-4-yl O-ethyl S-propyl phosphorothioate]

CAS name

O-[1-(4-chlorophenyl)-1H-pyrazol-4-yl] O-ethyl S-propyl phosphorothioate

Forever chemical

Other status information

Evidence of use in third world countries; PAN listed Highly Hazardous Chemical

Relevant Environmental Water Quality Standards

Physical state

Pale yellow oil

Commercial

Property

Value

Availability status

Considered obsolete

Introduction & key dates

1989, registered Japan; 2004, withdrawn China

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

Sumitomo Chemical Co. Ltd.
Schering-Plough Animal Health

Example products using this active

Starlex
Voltage
Boltage
Coopers Colleague Broad Spectrum Sheep & Lamb Drench

Formulation and application details

Available in a variety of formulations including emulsifiable concentrates, granules and wettable powders.

Commercial production

The synthesis of pyraclofos involves constructing its complex structure through a multi-step process centered around phosphorothioate ester formation. The key intermediate is 1-(4-chlorophenyl)-1H-pyrazol-4-ol, which is first reacted with ethyl chlorophosphate to introduce the O-ethyl phosphorothioate group. This intermediate is then coupled with propyl mercaptan under controlled conditions to yield the final product: O-[1-(4-chlorophenyl)-1H-pyrazol-4-yl] O-ethyl S-propyl phosphorothioate. The reaction typically requires an inert atmosphere and a base such as triethylamine to neutralise byproducts.

Impact on climate of production and use

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

Moderate

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

Miscible

Acetone

Miscible

Ethanol

Miscible

Methanol

Melting point (°C)

Not applicable

Boiling point (°C)

454

Degradation point (°C)

Flashpoint (°C)

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

5.89 X 10⁰³

Calculated

Log P

3.77

High

Fat solubility of residues

Solubility

Data type

Density (g ml⁻¹)

1.271

Dissociation constant pKa) at 25 °C

Vapour pressure at 20 °C (mPa)

1.60 X 10^-03

Low volatility

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

1.75 X 10^-05

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)

Moderately persistent

DT₅₀ (lab at 20 °C)

DT₅₀ (field)

Moderately persistent

DT₉₀ (lab at 20 °C)

DT₉₀ (field)

Note

Best available data

Manure DT₅₀ (days)

Aqueous photolysis DT₅₀ (days) at pH 7

Value

Note

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

Value

Non-persistent

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)

Slightly mobile

K_oc (mL g⁻¹)

2095

Notes and range

Estimated

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

1.15

Calculated

Low leachability

Bio-concentration factor

BCF (l kg⁻¹)

CT₅₀ (days)

Known soil and groundwater metabolites

None

Other known metabolites

Metabolite name and reference

Aliases

Formation medium / Rate

Estimated maximum occurrence fraction

1-(4-chlorophenyl)pyrazol-4-yl-6-O-malonyl-beta-D-glcopyranoside

Plant

0.51

1-(4-chlorophenyl)pyrazo-4-yl sulfate

Rat (Urine)

0.7

desethylpyraclofos

Rat (Urine, Faecal)

1-(4-chlorophenyl)pyrazol-4-yl-beta-D-glcopyranoside

Plant

des-S-propylpyraclofos

Rat (Urine, Faecal)

O-ethyl-S-propyl-phosphorothioate

Rat (Urine)

monoethylphosphate

Rat (Urine)

ECOTOXICOLOGY

Terrestrial ecotoxicology

Property

Value

Source; quality score; and other information

Interpretation

Mammals - Acute oral LD₅₀ (mg kg⁻¹)

237

Rat

Moderate

Mammals - Short term dietary NOEL

(mg kg⁻¹)

0.1

Rat 2 yr

High

(ppm diet)

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

Birds - Acute LD₅₀ (mg kg⁻¹)

164

Colinus virginianus

Moderate

Birds - Short term dietary (LC₅₀/LD₅₀)

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

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

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

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)

0.953

Apis mellifera

High

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

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)

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)

0.028

Cyprinidae spp.

High

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)

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)

237

Rat

Moderate

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

2000

Rat

Mammals - Inhalation LC₅₀ (mg l⁻¹)

1.46

Rat

Other Mammal toxicity endpoints

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

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; List II

Exposure Routes

Public

Occupational

Mammalian dose elimination route and rate

Rapidly absorbed, metabolised and excreted in the urine

Health issues

Specific human health issues (hazard-based)

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

Harmful if swallowed

Handling issues

Property

Value and interpretation

General

IMDG Transport Hazard Class 6.1

CLP classification 2013

Health: H301

WHO Classification

II (Moderately hazardous)

UN Number

UN2811

Waste disposal & packaging

Packaging Group III (minor danger)

Shelf-life, storage, stability and reactivity

TRANSLATIONS

Language

Name

English

pyraclofos

French

pyraclofos

German

Pyraclofos

Danish

pyraclofos

Italian

piraclofos

Spanish

piraclofos

Greek

Polish

pyraklofos

Swedish

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