Alpha-cypermethrin (Ref: OMS 3004)

Alpha-cypermethrin (Ref: OMS 3004)	Last updated: 04/09/2025
(Also known as: alphacypermethrin; alphamethrin; FMC 63318; FMC 39391; alfamethrin)

SUMMARY

Alpha-cypermethrin is a widely used pyrethroid insecticide. It has a low aqueous solubility, in relatively volatile and, based on its chemical properties, is not expected to leach to groundwater. However, it is considered to be a serious water pollutant. It is moderately persistent in soil and has been known to persist in water. It is highly toxic to mammals and a recognised irritant. It is relatively non-toxic to birds but is highly toxic to most aquatic organisms and honeybees. Alpha-cypermethrin is moderately toxic to earthworms.

GENERAL INFORMATION

Description

A pyrethroid pour-on antiparasitic treatment

Examples of veterinary uses

Used for the control of ectoparasites such as ticks, fleas, lice and blowflies

Examples of species treated

Cattle; Sheep; Goats; Pigs; Horses; Poultry; Dogs

Approval status

VMR 2013/2033 approval status (GB/UK)

Approved - usually as prescription-only-medicine to be authorised by a registered, qualified person (POM-VPS)

EU Regulatory approval status

Approved

Chemical structure

Isomerism

Cypermethrin itself is a chiral molecule and consists of eight isomers, four cis and four trans. Alpha-Cypermethrin contains more than 90% of the insecticidally most active enantiomer pair of the four cis isomers of cypermethrin

Chemical formula

C₂₂H₁₉Cl₂NO₃

Canonical SMILES

CC1(C(C1C(=O)OC(C#N)C2=CC(=CC=C2)OC3=CC=CC=C3)C=C(Cl)Cl)C

Isomeric SMILES

CC1([C@H]([C@H]1C(=O)OC(C#N)C2=CC(=CC=C2)OC3=CC=CC=C3)C=C(Cl)Cl)C

International Chemical Identifier key (InChIKey)

KAATUXNTWXVJKI-DXCJPMOASA-N

International Chemical Identifier (InChI)

InChI=1S/C22H19Cl2NO3/c1-22(2)17(12-19(23)24)20(22)21(26)28-18(13-25)14-7-6-10-16(11-14)27-15-8-4-3-5-9-15/h3-12,17-18,20H,1-2H3/t17-,18?,20-/m0/s1

2D structure diagram/image available?

Yes

Cambridge Crystallographic Data Centre diagrams

Common Name	Relationship	Link
alpha-cypermethrin	-

General status

Veterinary substance type

Antiparasitic,

Other bioactivity & uses

Biocide; Wood preservative

Substance groups

Pyrethroid insecticide

Minimum active substance purity

980 g kg⁻¹

Known relevant impurities

EU dossier - None declared

Substance origin

Synthetic

Mode of action

Non-systemic with contact and stomach action. Sodium channel modulator.

Molecular targets

[Sodium channel, Modulator]

CAS RN

67375-30-8

EC number

257-842-9

CIPAC number

454

US EPA chemical code

PubChem CID

49833

CLP index number

607-422-00-X

Therapeutic Class

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

ATCvet Code

QP53AC08

Controlled Drug?

Regulation 37/2010 MRL Classification

Allowed substance (Table 1: Bovine, Ovine)

Molecular mass

416.30

PIN (Preferred Identification Name)

rac-(R)-cyano(3-phenoxyphenyl)methyl (1S,3S)-3-(2,2-dichloroethenyl)-2,2-dimethylcyclopropane-1-carboxylate

IUPAC name

[cyano-(3-phenoxyphenyl)methyl] (1R,3R)-3-(2,2-dichloroethenyl)-2,2-dimethylcyclopropane-1-carboxylate

CAS name

(R)-cyano(3-phenoxyphenyl)methyl (1S,3S)-rel-3-(2,2-dichloroethenyl)-2,2-dimethylcyclopropanecarboxylate

Forever chemical

Other status information

Marine pollutant; Some applications are approved under GB Biocides Products Regulations

Relevant Environmental Water Quality Standards

UK Environment Agency non-statutory standard for the protection of aquatic life in freshwater and saltwater annual average 0.0002 µg l⁻¹, max acceptable conc 0.002 µg l⁻¹
UK statutory standard for water quality: ‘Good’ for fresh, transitional & saltwater: 0.1 ng l⁻¹ as annual mean conc, 0.4 ng l⁻¹ 95th percentile

Physical state

Colourless crystals

Related substances & organisms

cypermethrin

beta-cypermethrin

theta-cypermethrin

zeta-cypermethrin

zeta-cypermethrin

Commercial

Property

Product

Manufacturer

Authorisation Route

Legal Class (GB/UK)

Availability status

Current

Introduction & key dates

1983, first reported; circa 1985, first introduced

Example products (past and present) using this active

Dysect Cattle Pour-On Solution

Zoetis UK Ltd

UK National authorisation (IC)

Prescription only medicine to be authorised by suitably qualified person (POM-VPS)

Disect Sheep Pour-On

Zoetis UK Ltd

UK National authorisation (IC)

Prescription only medicine to be authorised by suitably qualified person (POM-VPS)

Zermasect sheep pour-on

Zoetis UK Ltd

UK National authorisation (IC)

Prescription only medicine to be authorised by suitably qualified person (POM-VPS)

Formulation and application details

Usually supplied as a pour-on formulation

Commercial production

Alpha-cypermethrin is produced commercially through a multi-step chemical synthesis that isolates the most biologically active isomers of cypermethrin. The process begins with the synthesis of the isomeric-mixture of cypermethrin and involves reacting 3-phenoxybenzyl alcohol with cyanoacetic acid derivatives and dichlorovinyl cyclopropane carboxylic acid. The alpha isomer is isolated using chiral resolution or selective crystallization.

Impact on climate of production and use

Production of alpha-cypermethrin is quite energy intensive. Whilst the amount of CO₂e produced during production will depend on the precise process, Audsley et al. (2009) reported that it takes 518 MJ of energy per kg produced. This is equivalent to 35.7 kg CO₂e. There will also be emissions associated with packaging, transport and application.

ENVIRONMENTAL FATE

Property

Value

Source; quality score; and other information

Interpretation

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

0.004

Low

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

596000

Toluene

21300

Methanol

584000

Ethyl acetate

Melting point (°C)

82.1

Boiling point (°C)

Decomposes before boiling

Degradation point (°C)

248

Flashpoint (°C)

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

6.31 X 10⁰⁵

Calculated

Log P

5.8

High

Fat solubility of residues

Solubility

Soluble

Data type

Regulatory data - identified in ruminant and poultry metabolism studies

Density (g ml⁻¹)

Dissociation constant pKa) at 25 °C

Not applicable

No dissociation

Vapour pressure at 20 °C (mPa)

3.8 X 10^-04

Low volatility

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

5.30 X 10^-02

Non-volatile

Volatilisation as max % of applied dose lost

From plant surface

From soil surface

Maximum UV-vis absorption L mol⁻¹ cm⁻¹

276nm = 2073, 300nm = 38.64

Surface tension (mN m⁻¹)

Not applicable

Refractive Index

Environmental release

Degradation

Property

Value

Source; quality score; and other information

Interpretation

Soil degradation (days) (aerobic)

DT₅₀ (typical)

23.0

Non-persistent

DT₅₀ (lab at 20 °C)

23.4

Non-persistent

DT₅₀ (field)

42.6

Moderately persistent

DT₉₀ (lab at 20 °C)

166

Persistent

DT₉₀ (field)

120.2

Note

EU 2017 dossier Lab studies DT₅₀ range 3.1-48.1 days - not normalised, DT₉₀ range 4.5-329.4 days, Soils=7, Field studies DT₅₀ range 11.7-114.1 days, DT₉₀ range 38.7-250.5 days, Soils = 6; EU 2004 dossier Lab studies DT₅₀ range 25-125 days, DT₉₀ range 102-792 days, Field studies DT₅₀ range 14-112 day (UK conditions), DT₉₀ range 35-385 days; Other sources:DT₅₀ 77 days (DW4)

Manure DT₅₀ (days)

Aqueous photolysis DT₅₀ (days) at pH 7

Value

6.3

Moderately fast

Note

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

Value

at 25°C

Moderately persistent

Note

DT₅₀ sensitive to pH: stable at pH 4, 3.3 days at pH 9 & 25 °C

Water-sediment DT₅₀ (days)

Fast

Water phase only DT₅₀ (days)

1.3

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

Soil adsorption and mobility

Property

Value

Source; quality score; and other information

Interpretation

Linear

K_d (mL g⁻¹)

3308

Non-mobile

K_oc (mL g⁻¹)

288735

Notes and range

EU 2017 dossier K_d range 2366-4362 mL g⁻¹, K_oc range 228622-353100 mL g⁻¹, Soils =5

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

-2.38

Calculated

Low leachability

Bio-concentration factor

BCF (l kg⁻¹)

910

Threshold for concern

CT₅₀ (days)

7.8

Known soil metabolites

Metabolite

Major/Minor fraction

$Click here for further information on Major/Minor fraction$

Estimated maximum occurrence fraction

Notes

4-hydroxy-alpha-cypermethrin (Ref: CL 194198)

Minor fraction

0.08

3-phenoxybenzoic acid

Minor fraction

0.054

3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropanecarboxylic acid

Major fraction

0.136

Known groundwater metabolites

None

Other known metabolites

Metabolite name and reference

Aliases

Formation medium / Rate

Estimated maximum occurrence fraction

3-phenoxybenzoic acid

3-PBA

Rat; Animal; Crop; Surface water; Sediment

N-(3-phenoxybenzoyl)glycine

3-PBA glycine

Animal; Crop

3-hydroxy-benzoic acid

3-HBA

Animal

4-hydroxy-alpha-cypermethrin (Ref: CL 194198)

M310I017

Rat; Animal; Crop

M310I015

Rat; Animal

M310I005

Crop

M310I007

Crop

3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropanecarboxylic acid

DCVA; M310I001

Rat; Animal; Surface water; Sediment

M310I004

Rat; Animal; Crop

M310I008

Crop

hydroxylated DCVA

M310I003

Rat; Animal

3-phenoxybenzoic alcohol

3-PBAlc; M310I024

Crop

3-phenoxybenaldehyde

3-PBAld; M3010I018

Crop

ECOTOXICOLOGY

Terrestrial ecotoxicology

Property

Value

Source; quality score; and other information

Interpretation

Mammals - Acute oral LD₅₀ (mg kg⁻¹)

Rat

High

Mammals - Short term dietary NOEL

(mg kg⁻¹)

Rat

High

(ppm diet)

200

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

> 20

Unknown species Reproductive NOAEL

Moderate

Birds - Acute LD₅₀ (mg kg⁻¹)

> 2025

Colinus virginianus

Low

Birds - Short term dietary (LC₅₀/LD₅₀)

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

Coturnix japonica NOEL

Moderate

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

> 100

Eisenia foetida

Moderate

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

> 2.00

Eisenia foetida corr

Moderate

Soil micro-organisms

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

Dose: 0.3 kg ha⁻¹ 28 Day

Collembola

Acute LC₅₀ (mg kg⁻¹)

> 129

Folsomia candida corr

Chronic NOEC (mg kg⁻¹)

Non-target plants

Vegetative vigour ER₅₀ (g ha⁻¹)

> 100.0

4 plant species tested

Seedling emergence ER₅₀ (g ha⁻¹)

> 100

4 plant species tested

Honeybees (Apis spp.)

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

0.033

Apis mellifera

High

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

0.059

Apis mellifera

High

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

Chronic as 10-day LDD₅₀ µg bee⁻¹ day⁻¹

0.11

Apis mellifera

Notes

Bumblebees (Bombus spp.)

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

> 0.29

Bombus terrestris

High

Literature values DT₅₀ 24hr = 0.17 µg bee⁻¹; 72hr = 0.15 µg bee⁻¹

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

> 0.54

Bombus terrestris

High

Literature values DT₅₀ 24hr = 0.52 µg bee⁻¹; 72hr = 0.36 µg bee⁻¹

Mason bees (Osmia spp.)

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

0.25

Osmia bicornis

High

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) as Mortality LR₅₀ g ha⁻¹, Aged residue test

0.0519

Coccinella septempunctata Larva

High

Beneficial insects (Lacewings) as Mortality LR₅₀ g ha⁻¹, Aged residue test

0.00288

Chrysoperla carnea Larva

High

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

0.031

Aphidius rhopalosiphi

High

Beneficial insects (Predatory mites) as Mortality LR₅₀ g ha⁻¹, Std lab test

0.0019

Typhlodromus pyri

High

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)

0.0018

Oncorhynchus mykiss

High

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

0.00003

Pimephales promelas

High

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

> 0.00002

Danio rerio

High

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

0.00022

Daphnia magna

High

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

0.00003

Daphnia magna

High

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

0.00021

Ceriodaphnia dubia

High

Aquatic crustaceans - Acute 96 hour LC₅₀ (mg l⁻¹)

Sediment dwelling organisms - Acute 96 hour LC₅₀ (mg l⁻¹)

0.000013

Chironomus riparius

High

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) (ErC₅₀, Static)

> 0.00139

Lemna gibba

High

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

Algae - Acute (growth rate, fresh; mg l⁻¹) (96 hr ErC₅₀, Static)

>= 0.0836

Raphidocelis subcapitata

Moderate

Algae - Chronic (growth rate, fresh; mg l⁻¹) (96 hr NOEC, static)

0.0836

Raphidocelis subcapitata

Moderate

Mesocosm study data

NOEAEC mg l⁻¹

0.000015

Aquatic invertebrates and algae

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)

Rat

High

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

2000

Rat

Mammals - Inhalation LC₅₀ (mg l⁻¹)

1.33

Rat 4 hr (nose only)

Other Mammal toxicity endpoints

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

0.00125

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

0.00125

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

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

0.0005

Dermal penetration studies (%)

0.7-3.0

concentration dependent

Dangerous Substances Directive 76/464

Exposure Routes

Public

No unacceptable risks identified for the general public, bystanders and residents

Occupational

No unacceptable risks identified for operators or other farm workers

Mammalian dose elimination route and rate

In rats after 8 days 50-60% of the dose was excreted in the urine and 30-40% in the faeces. Elimination rates vary with species

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

General human health issues

Highly toxic by ingestion

Handling issues

Property

Value and interpretation

General

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

CLP classification 2013

Health: H301, H335, H373
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

Shelf-life is around 2 years under normal storage conditions.

TRANSLATIONS

Language

Name

English

alpha-cypermethrin

French

alphacypermethrine

German

alpha-Cypermethrin

Danish

alpha-cypermethrin

Italian

alfametrina

Spanish

alfacipermetrina

Greek

Polish

alfa-cypermetryna

Swedish

alfacypermetrin

Hungarian

alphamethrin / alpha cypremethrin

Dutch

alfa-cypermethrin

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