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Pyraclofos (Ref: OMS 3040)
Last updated: 22/10/2025
(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?
No
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
Global Governance status: Listed (✓) under
UK Poisons List Order 1972 Rotterdam Convention Montreal Protocol
XNo
The Poisons List Order 1972
XNo
Rotterdam Convention
XNo
Montreal Protocol
Stockholm Convention OSPAR EU Water Framework Directive
XNo
Stockholm Convention
XNo
OSPAR
XNo
EU Water Framework Directive
Relevant Environmental Water Quality Standards
-
Forever chemical
-
Other status information
Evidence of use in third world countries
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.
  • 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 at pH 7 (mg l⁻¹)
33
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
 Moderate
Solubility - In organic solvents at 20 °C (mg l⁻¹)
Miscible
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
Acetone		 -
Miscible
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
Ethanol		 -
Miscible
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
Methanol		 -
Melting point (°C)
Not applicable
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
 -
Boiling point (°C)
454
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
 -
Degradation point (°C)
- - -
Flashpoint (°C)
- - -
Octanol-water partition coefficient at pH 7, 20 °C
P
5.89 X 1003 Calculated -
Log P
3.77
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
 High
Fat solubility of residues
Solubility
- - -
Data type
- - -
Density (g ml⁻¹)
1.271
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
 -
Dissociation constant pKa) at 25 °C
- - -
-
Vapour pressure at 20 °C (mPa)
1.60 X 10-03
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
 Low volatility
Henry's law constant at 25 °C (Pa m³ mol⁻¹)
1.75 X 10-05
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
 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)
39
K4 K = Research datasets (e.g. Pandora, Demetra; these datasets no longer available). Norman Ecotoxicology database. (click here )
4 = Verified data
 Moderately persistent
DT₅₀ (lab at 20 °C)
- - -
DT₅₀ (field)
50
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
 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
29
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
 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
Kd (mL g⁻¹)
-
Q2 Q = Miscellaneous data from online sources
2 = Unverified data of unknown source
 Slightly mobile
Koc (mL g⁻¹)
2095
Notes and range
Estimated
Freundlich
Kf (mL g⁻¹)
- - -
Kfoc (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
F3 F = U.S. EPA ECOTOX database / U.S. EPA pesticide fate database / Miscellaneous WHO documents / FAO data, IPCS INCHEM data (US EPA Databases Related to Pesticide Risk Assessment )
3 = Unverified data of known source
Rat		 Moderate
Mammals - Short Term Oral NOAEL (mg kg⁻¹ bw d⁻¹)
- - -
Mammals - Long Term (Chronic) Oral NOAEL (mg kg⁻¹ bw d⁻¹)
- - -
Birds - Acute LD₅₀ (mg kg⁻¹)
164
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
Colinus virginianus		 Moderate
Birds - Short term dietary LC₅₀ (mg kg⁻¹ bw d⁻¹)
- - -
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
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
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)
- - -
Beneficial insects (Butterflies)
Contact
- - -
Notes
-
Oral
- - -
Notes
-
Aquatic ecotoxicology
Property
Value
Source; quality score; and other information
Interpretation
Temperate Freshwater Fish - Acute 96 hour LC₅₀ (mg l⁻¹)
0.028
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
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
- - -
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
F3 F = U.S. EPA ECOTOX database / U.S. EPA pesticide fate database / Miscellaneous WHO documents / FAO data, IPCS INCHEM data (US EPA Databases Related to Pesticide Risk Assessment )
3 = Unverified data of known source
Rat		 Moderate
Mammals - Short Term Oral NOAEL (mg kg⁻¹ bw d⁻¹)
- - -
Mammals - Long Term (Chronic) Oral NOAEL (mg kg⁻¹ bw d⁻¹)
- - -
Mammals - Dermal LD₅₀ (mg kg⁻¹ body weight)
> 2000
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
Rat		 -
Mammals - Inhalation LC₅₀ (mg l⁻¹)
1.46
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
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
Q3 Q = Miscellaneous data from online sources
3 = Unverified data of known source
 -
Health issues
Specific human health issues (hazard-based)
Carcinogen
Genotoxic
Endocrine disruptor
XNo, known not to cause a problem
A0 A = Chromosome aberration (EFSA database)
0 = No data
;
B0 B = DNA damage/repair (EFSA database)
0 = No data
;
C0 C = Gene mutation (EFSA database)
0 = No data
;
D0 D = Genome mutation (EFSA database)
0 = No data
;
E0 E = Unspecified genotoxicity type (miscellaneous data source)
0 = No data
 No data found
Reproduction / development effects Acetyl cholinesterase inhibitor Neurotoxicant
?Possibly, status not identified
✓Yes, known to cause a problem
?Possibly, status not identified
Respiratory tract irritant Skin irritant Skin sensitiser
XNo, known not to cause a problem
XNo, known not to cause a problem
 No data found
Eye irritant Phototoxicant  
XNo, known not to cause a problem
 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: 22/10/2025
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

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