Dioxathion (Ref: Hercules AC25)

Dioxathion (Ref: Hercules AC25)	Last updated: 04/09/2025
(Also known as: dioxation; delnav; dioxane phosphate; dioxationum)

GENERAL INFORMATION

Description

An organophosphate compound once used as an insecticide on livestock

Examples of veterinary uses

Once used to control ticks, fleas and mites

Examples of species treated

Cattle; Goats; Sheep; Pigs

Approval status

VMR 2013/2033 approval status (GB/UK)

Not approved

EU Regulatory approval status

Not approved

Chemical structure

Isomerism

Dioxathion exhibits cis–trans isomerism, which arises from the spatial arrangement of its two sulphur-containing substituents on the dioxane ring. The molecule contains a central 1,4-dioxane ring substituted with two diethyl phosphorodithioate groups at the 2 and 3 positions. Depending on whether these bulky groups are on the same side of the ring (cis) or opposite sides (trans), the molecule exists in two distinct geometric forms. The cis-isomer is approximately four times more acutely toxic than the trans-isomer. Technical-grade dioxathion is typically a mixture of both isomers.

Chemical formula

C₁₂H₂₆O₆P₂S₄

Canonical SMILES

CCOP(=S)(OCC)SC1C(OCCO1)SP(=S)(OCC)OCC

Isomeric SMILES

No data

International Chemical Identifier key (InChIKey)

VBKKVDGJXVOLNE-UHFFFAOYSA-N

International Chemical Identifier (InChI)

InChI=1S/C12H26O6P2S4/c1-5-15-19(21,16-6-2)23-11-12(14-10-9-13-11)24-20(22,17-7-3)18-8-4/h11-12H,5-10H2,1-4H3

2D structure diagram/image available?

Yes

General status

Veterinary substance type

Insecticide

Substance groups

Organophosphate insecticide; Organophosphate acaricide; Organothiophosphate insecticide; Organothiophosphate acaricide

Minimum active substance purity

>68%

Known relevant impurities

Substance origin

Synthetic

Mode of action

Acetylcholinesterase (AChE) inhibitor.

Molecular targets

[Cholinesterase, Inhibitor]

CAS RN

78-34-2

EC number

201-107-7

CIPAC number

124

US EPA chemical code

037801

PubChem CID

6531

CLP index number

015-063-00-X

Therapeutic Class

ATCvet Code

None allocated

Controlled Drug?

Regulation 37/2010 MRL Classification

Molecular mass

456.54

PIN (Preferred Identification Name)

O,O,O',O'-tetraethyl S,S'-1,4-dioxane-2,3-diyl bis(phosphorodithioate)

IUPAC name

S,S'-(1,4-dioxane-2,3-diyl) O,O,O',O'-tetraethyl bis(phosphorodithioate)

CAS name

S,S'-1,4-dioxane-2,3-diyl bis(O,O-diethyl phosphorodithioate)

Forever chemical

Other status information

Marine Pollutant; Subject to the provisions of the UK Poisons Act 1972

Relevant Environmental Water Quality Standards

Physical state

Reddish-brown liquid

Commercial

Property

Product

Manufacturer

Authorisation Route

Legal Class (GB/UK)

Availability status

Considered obsolete but may be available in some countries

Introduction & key dates

1959, first reported; 1988, withdrawn USA

Example products (past and present) using this active

Formulation and application details

Commercial production

The production of dioxathion involves synthesising a central 1,4-dioxane ring substituted with two diethyl phosphorodithioate groups at the 2 and 3 positions. The process begins with the formation of the dioxane backbone, typically through condensation of ethylene glycol derivatives under acidic conditions. Once the ring is established, the key step involves introducing the phosphorodithioate moieties via esterification or nucleophilic substitution using diethyl phosphorodithioic chloride or similar reagents. This results in the formation of the symmetrical bis-substituted compound.

Impact on climate of production and use

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

1.55

at 25 °C

Low

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

20000

Kerosene

10000

n-hexane

Melting point (°C)

-2

Boiling point (°C)

Degradation point (°C)

Flashpoint (°C)

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

2.82 X 10⁰³

Calculated

Log P

3.45

High

Fat solubility of residues

Solubility

Soluble

Data type

Regulatory data - observed in metabolism and farm animal feeding studies

Density (g ml⁻¹)

1.26

Dissociation constant pKa) at 25 °C

Vapour pressure at 20 °C (mPa)

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

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)

DT₉₀ (lab at 20 °C)

DT₉₀ (field)

Note

Literature values give DT₅₀ range 15 (silty clay loam) - 55 days (clay)

Manure DT₅₀ (days)

Aqueous photolysis DT₅₀ (days) at pH 7

Value

Stable

Note

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

Value

Stable

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)

Non-mobile

K_oc (mL g⁻¹)

11845

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

-0.11

Calculated

Low leachability

Bio-concentration factor

BCF (l kg⁻¹)

CT₅₀ (days)

Known metabolites

None

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)

(ppm diet)

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

Birds - Acute LD₅₀ (mg kg⁻¹)

> 3600

Anas platyrhynchos

Low

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)

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)

> 50

Moderate

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)

0.118

Oncorhynchus mykiss

Moderate

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)

0.00035

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

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)

235

Rat

Mammals - Inhalation LC₅₀ (mg l⁻¹)

Other Mammal toxicity endpoints

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

0.0015

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

May be absorded through the skin - PPE/PPC required

Mammalian dose elimination route and rate

Eliminated in faeces and urine

Health issues

Specific human health issues

Carcinogen

Genotoxic

Endocrine disruptor

No data found

; ; ; ;

No data found

Reproduction / development effects

Acetyl cholinesterase inhibitor

Neurotoxicant

No data found

Respiratory tract irritant

Skin irritant

Skin sensitiser

No data found

Eye irritant

Phototoxicant

No data found

General human health issues

May cause mild transient conjunctivitis
Very toxic

Handling issues

Property

Value and interpretation

General

Prevent generation of mists

CLP classification 2013

Health: H300, H311, H330
Environment: H400, H410

WHO Classification

Ib (Highly hazardous)

UN Number

Waste disposal & packaging

Shelf-life, storage, stability and reactivity

TRANSLATIONS

Language

Name

English

dioxathion

French

dioxathion

German

Dioxathion

Danish

Italian

Spanish

dioxation

Greek

Polish

dioksation

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