Azamethiphos (Ref: GCA 18809)	Last updated: 15/09/2025
(Also known as: OMS 1825)

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SUMMARY

Azamethiphos is an organophosphate used as an insecticide and as an antiparasitic agent for veterinary use. It is highly soluble in water, volatile and not expected to leach to groundwater. Not a great deal is known about its environmental persistence. It is moderately toxic to mammals and not expected to bioaccumulate. It is a mutagen, neurotoxicant and an acetyl cholinesterase inhibitor. Azamethiphos is highly toxic to birds and aquatic invertebrates and moderately toxic to fish.

GENERAL INFORMATION

Description	An organophoshorus insecticide used for parasitic control
Examples of veterinary uses	Used in fish farming to control external parasites on Atlantic Salmon and for parasite control on other animals
Examples of species treated	Salmon; Dogs; cats

Approval status

VMR 2013/2033 approval status (GB/UK)	Approved - usually as prescription-only-medicine to be authorised by a veterinarian (POM-V)
EU Regulatory approval status	Approved

Chemical structure

Isomerism	None
Chemical formula	C₉H₁₀ClN₂O₅PS
Canonical SMILES	COP(=O)(OC)SCN1C2=NC=C(C=C2OC1=O)Cl
Isomeric SMILES	No data
International Chemical Identifier key (InChIKey)	VNKBTWQZTQIWDV-UHFFFAOYSA-N
International Chemical Identifier (InChI)	InChI=1S/C9H10ClN2O5PS/c1-15-18(14,16-2)19-5-12-8-7(17-9(12)13)3-6(10)4-11-8/h3-4H,5H2,1-2H3
2D structure diagram/image available?	Yes

General status

Veterinary substance type	Antiparasitic, Veterinary hygiene
Substance groups	Organophosphate insecticide; Organothiophosphate insecticide
Minimum active substance purity	>95%
Known relevant impurities	-
Substance origin	Synthetic
Mode of action	Contact and stomach action, rapid knockdown. Acetylcholinesterase (AChE) inhibitor.
Molecular targets	[Cholinesterase, Inhibitor]
CAS RN	35575-96-3
EC number	252-626-0
CIPAC number	None allocated
US EPA chemical code	129101
PubChem CID	71482
Therapeutic Class	Antiparasitic products, insecticides & repellents: Ecoparasiticides, insecticides & repellents
ATCvet Code	QP53AF17
Controlled Drug?	No
Regulation 37/2010 MRL Classification	Allowed substance (Table 1: Salmonidae)
Molecular mass	324.68
PIN (Preferred Identification Name)	S-[(6-chloro-2-oxo-1,3-oxazolo[4,5-b]pyridin-3(2H)-yl)methyl] O,O-dimethyl phosphorothioate
IUPAC name	S-6-chloro-2,3-dihydro-2-oxo-1,3-oxazolo[4,5-b]pyridin-3-ylmethyl O,O-dimethyl phosphorothioate
CAS name	S-[(6-chloro-2-oxooxazolo[4,5-b]pyridin-3(2H)-yl)methyl] O,O-dimethyl phosphorothioate
Forever chemical	-
Other status information	PAN Bad Actor Chemical
Relevant Environmental Water Quality Standards	UK non-statutory standard for protection of freshwater and saltwater aquatic life 0.02 µg l⁻¹ as annual average, 0.05 as max acceptable conc.
Physical state	Colourless to grey cystalline solid

Commercial

Property	Value
Availability status	Current
Introduction & key dates	1970, introduced; 1975, first registered USA
Example manufacturers & suppliers of products using this active now or historically	Syngenta Ciba-Geigy Benchmark Animal Health Ltd Ground Animal Health Ltd
Example products using this active	Alfacron Snip Zazafly Salmosan Powder for Suspension for Fish Treatment Azasure powder suspension for fish treatment
Formulation and application details	Often supplied as a wettable powders, direct use bait formulations and as water soluble bath additives
Commercial production	The production of azamethiphos involves a multi-step chemical synthesis. The process begins with the preparation of a branched-chain chlorination product by reacting oxazole [4,5-b]pyridine-2(3H)-ketone with paraformaldehyde, thionyl chloride, and other reagents in a rotational flow kettle. This intermediate is then used to synthesize a thiophosphate ester in a second reaction unit. Finally, the ester is reacted in a third unit to yield azamethiphos.
Impact on climate of production and use	Data for the amount of life cycle GHGs produced by azamethiphos 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)		1100	E3 E = Manufacturers safety data sheets 3 = Unverified data of known source	High
Solubility - In organic solvents at 20 °C (mg l⁻¹)		610000	L3 L = Pesticide manuals and hard copy reference books / other sources 3 = Unverified data of known source Dichloromethane	-
		130000	L3 L = Pesticide manuals and hard copy reference books / other sources 3 = Unverified data of known source Benzene	-
		100000	L3 L = Pesticide manuals and hard copy reference books / other sources 3 = Unverified data of known source Methanol	-
		5800	L3 L = Pesticide manuals and hard copy reference books / other sources 3 = Unverified data of known source n-Octanol	-
Melting point (°C)		89	L3 L = Pesticide manuals and hard copy reference books / other sources 3 = Unverified data of known source	-
Boiling point (°C)		Decomposes before boiling	Q3 Q = Miscellaneous data from online sources 3 = Unverified data of known source	-
Degradation point (°C)		-	-	-
Flashpoint (°C)		150	L3 L = Pesticide manuals and hard copy reference books / other sources 3 = Unverified data of known source	-
Octanol-water partition coefficient at pH 7, 20 °C	P	1.12 X 1001	Calculated	-
	Log P	1.05	L3 L = Pesticide manuals and hard copy reference books / other sources 3 = Unverified data of known source	Low
Fat solubility of residues	Solubility	-	-	-
	Data type	-	-	-
Density (g ml⁻¹)		1.6	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)		0.0049	E3 E = Manufacturers safety data sheets 3 = Unverified data of known source	Low volatility
Henry's law constant at 25 °C (Pa m³ mol⁻¹)		1.45 X 10-06	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)	0.25	L3 L = Pesticide manuals and hard copy reference books / other sources 3 = Unverified data of known source	Non-persistent
	DT₅₀ (lab at 20 °C)	-	-	-
	DT₅₀ (field)	-	-	-
	DT₉₀ (lab at 20 °C)	-	-	-
	DT₉₀ (field)	-	-	-
	Note	Best available data, Industry data DT₅₀ in loamy sand circa 6 hours (E3)
Manure DT₅₀ (days)		-	-	-
Aqueous photolysis DT₅₀ (days) at pH 7	Value	-	-	-
	Note	-
Aqueous hydrolysis DT₅₀ (days) at 20 °C and pH 7	Value	11	L3 L = Pesticide manuals and hard copy reference books / other sources 3 = Unverified data of known source	Non-persistent
	Note	pH sensitive ranging from 33 days at pH 5 to 4.3 hrs at pH 9
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)	-	S1 S = Expert judgement 1 = Estimated data with little or no verification	Mobile
	Koc (mL g⁻¹)	25
	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		-1.57	Calculated	Low leachability
Bio-concentration factor	BCF (l kg⁻¹)	1.56	Q2 Q = Miscellaneous data from online sources 2 = Unverified data of unknown source Estimated	Low potential
	CT₅₀ (days)	Not available		-

Known metabolites

None

ECOTOXICOLOGY

Terrestrial ecotoxicology

Property		Value	Source; quality score; and other information	Interpretation
Mammals - Acute oral LD₅₀ (mg kg⁻¹)		1180	L3 L = Pesticide manuals and hard copy reference books / other sources 3 = Unverified data of known source Rat	Moderate
Mammals - Short term dietary NOEL	(mg kg⁻¹)	2	L3 L = Pesticide manuals and hard copy reference books / other sources 3 = Unverified data of known source Rat	High
	(ppm diet)	20		-
Mammals - Chronic 21d NOAEL (mg kg⁻¹ bw d⁻¹)		-	-	-
Birds - Acute LD₅₀ (mg kg⁻¹)		> 30.2	L3 L = Pesticide manuals and hard copy reference books / other sources 3 = Unverified data of known source Colinus virginianus	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)	10.0	R3 R = Peer reviewed scientific publications 3 = Unverified data of known source Apis mellifera	Moderate
	Oral acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg bee⁻¹)	0.1	R3 R = Peer reviewed scientific publications 3 = Unverified data of known source 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)	-	-	-
		-
	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)		> 0.115	L3 L = Pesticide manuals and hard copy reference books / other sources 3 = Unverified data of known source Oncorhynchus mykiss	Moderate
Temperate Freshwater Fish - Chronic 21 day NOEC (mg l⁻¹)		-	-	-
Tropical Freshwater Fish - Acute 96 hour LC₅₀ (mg l⁻¹)		7.76	F4 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 ) 4 = Verified data Danio rerio	Moderate
Temperate Freshwater Aquatic invertebrates - Acute 48 hour EC₅₀ (mg l⁻¹)		0.00067	L3 L = Pesticide manuals and hard copy reference books / other sources 3 = Unverified data of known source 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	-	-	-
	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)		1180	L3 L = Pesticide manuals and hard copy reference books / other sources 3 = Unverified data of known source Rat	Moderate
Mammals - Dermal LD₅₀ (mg kg⁻¹ body weight)		2150	L3 L = Pesticide manuals and hard copy reference books / other sources 3 = Unverified data of known source Rat	-
Mammals - Inhalation LC₅₀ (mg l⁻¹)		> 0.56	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)		0.025	A5 A = EU regulatory and evaluation data as published by EC, EFSA (RAR, DAR & Conclusion dossiers), EMA (e.g. EU Annex III PIC DGD) (EU - Pesticides database; EFSA Scientific Publications ) 5 = Verified data used for regulatory purposes	-
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		In rats azamethiphos is excreted via faeces, urine & in expelled air. In fish adsorption after topical application is slow and low. Excretion is rapid in all species.	A4 A = EU regulatory and evaluation data as published by EC, EFSA (RAR, DAR & Conclusion dossiers), EMA (e.g. EU Annex III PIC DGD) (EU - Pesticides database; EFSA Scientific Publications ) 4 = Verified data	-

Health issues

Specific human health issues		Carcinogen Genotoxic Endocrine disruptor No data found A3 A = Chromosome aberration (EFSA database) 3 = Negative ; B3 B = DNA damage/repair (EFSA database) 3 = Negative ; C3 C = Gene mutation (EFSA database) 3 = Negative ; D0 D = Genome mutation (EFSA database) 0 = No data ; E1 E = Unspecified genotoxicity type (miscellaneous data source) 1 = Positive XNo, known not to cause a problem Reproduction / development effects Acetyl cholinesterase inhibitor Neurotoxicant No data found ✓Yes, known to cause a problem ✓Yes, known to cause a problem Respiratory tract irritant Skin irritant Skin sensitiser No data found ?Possibly, status not identified ?Possibly, status not identified Eye irritant Phototoxicant   ✓Yes, known to cause a problem No data found
General human health issues		Mutagenic potential

Handling issues

Property	Value and interpretation
General	IMDG Transport Hazard Class 6.1
CLP classification 2013	Health: H302, H317, H332 Environment: H400, H410
WHO Classification	II (Moderately hazardous)
UN Number	UN2783
Waste disposal & packaging	-
Shelf-life, storage, stability and reactivity	-

TRANSLATIONS

Language	Name
English	azamethiphos
French	azametiphos
German	Azamethiphos
Danish	azamethiphos
Italian	azametifos
Spanish	azametifos
Greek	-
Polish	azametifos
Swedish	azametifos
Hungarian	-
Dutch	azamethifos
Norwegian	-

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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