Methoxychlor (Ref: OMS 466)

Methoxychlor (Ref: OMS 466)	Last updated: 04/09/2025
(Also known as: methoxychlore; dimethoxy-DT; dianisyl trichloroethane; ENT 1716; DMDT)

GENERAL INFORMATION

Description

In veterinary practices, methoxychlor was once used as an ectoparasiticide

Examples of veterinary uses

Use for general insect control

Examples of species treated

Cats; Dogs; Cattle, Horses

Approval status

VMR 2013/2033 approval status (GB/UK)

Not approved

EU Regulatory approval status

Not approved

Chemical structure

Isomerism

Methoxychlor exhibits positional isomerism due to the possibility of substitution at different positions on its aromatic rings. The commercial product is primarily p,p'-methoxychlor, where both methoxy groups are para-substituted on the phenyl rings. However, technical-grade methoxychlor contains a mixture of isomers, including o,p'-methoxychlor, where one methoxy group is ortho-substituted.

Chemical formula

C₁₆H₁₅Cl₃O₂

Canonical SMILES

COC1=CC=C(C=C1)C(C2=CC=C(C=C2)OC)C(Cl)(Cl)Cl

Isomeric SMILES

International Chemical Identifier key (InChIKey)

IAKOZHOLGAGEJT-UHFFFAOYSA-N

International Chemical Identifier (InChI)

InChI=1S/C16H15Cl3O2/c1-20-13-7-3-11(4-8-13)15(16(17,18)19)12-5-9-14(21-2)10-6-12/h3-10,15H,1-2H3

2D structure diagram/image available?

Yes

Cambridge Crystallographic Data Centre diagrams

Common Name	Relationship	Link
methoxychlor	-

General status

Veterinary substance type

Insecticide

Substance groups

Organochloride insecticide

Minimum active substance purity

Known relevant impurities

Substance origin

Synthetic

Mode of action

Contact and stomach action. Central nervous stimulant, producing hyperactivity, convulsions and death. Sodium channel modulator.

Molecular targets

[Progesterone synthesis, Inhibitor]

CAS RN

72-43-5

EC number

200-779-9

CIPAC number

US EPA chemical code

034001

PubChem CID

4115

CLP index number

No data found

Therapeutic Class

ATCvet Code

None allocated

Controlled Drug?

Regulation 37/2010 MRL Classification

Molecular mass

345.65

PIN (Preferred Identification Name)

IUPAC name

1,1,1-trichloro-2,2-bis(4-methoxyphenyl)ethane

CAS name

1,1'-(2,2,2-trichloroethylidene)bis(4-methoxybenzene)

Forever chemical

Other status information

POP candidate; OSPAR pfa

Relevant Environmental Water Quality Standards

Physical state

Colourless crystalline solid

Commercial

Property

Value

Availability status

Current

Introduction & key dates

Circa 1948, introduced

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

Kincaid Enterprises

Example products using this active

Double-M
Chemform
Moxie
Marlate

Formulation and application details

Supplied in a variety of formulations including emulsifiable concentrates, wettable powders, flowables, seed treatments and aerosols

Commercial production

Methoxychlor is synthesised through a condensation reaction between anisole (methoxybenzene) and chloral (trichloroacetaldehyde) in the presence of an acidic catalyst, typically sulfuric or hydrochloric acid. This reaction forms a central trichloromethyl-substituted carbon that links two anisole molecules, resulting in the final compound.

Impact on climate of production and use

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

0.1

Low

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

440000

Xylene

50000

Methanol

700000

Trichloroethane

1333000

Dichloromethane

Melting point (°C)

Boiling point (°C)

Degradation point (°C)

Flashpoint (°C)

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

6.76 X 10⁰⁵

Calculated

Log P

5.83

High

Fat solubility of residues

Solubility

Soluble

Data type

Regulatory data - observed in metabolism and farm animal feeding studies

Density (g ml⁻¹)

1.41

Dissociation constant pKa) at 25 °C

Vapour pressure at 20 °C (mPa)

0.08

Low volatility

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

2.00 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

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)

120

Persistent

DT₅₀ (lab at 20 °C)

120

Persistent

DT₅₀ (field)

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

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)

80000

Notes and range

Best available data

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

-1.88

Calculated

Low leachability

Bio-concentration factor

BCF (l kg⁻¹)

1622

(Other literature values Log BCF range 2.8-4.1 (R3))

Threshold for concern

CT₅₀ (days)

Not available

Known soil metabolites

Metabolite

Major/Minor fraction

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

Estimated maximum occurrence fraction

Notes

1,1-(2,2-dichloroethylidene)bis(4-methoxybenzene)

Known groundwater metabolites

None

Other known metabolites

None

ECOTOXICOLOGY

Terrestrial ecotoxicology

Property

Value

Source; quality score; and other information

Interpretation

Mammals - Acute oral LD₅₀ (mg kg⁻¹)

> 6000

Rat

Low

Mammals - Short term dietary NOEL

(mg kg⁻¹)

Rat 2 yr

(ppm diet)

200

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

Birds - Acute LD₅₀ (mg kg⁻¹)

> 2000

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)

> 23.6

Apis mellifera

Moderate

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

5.0

Apis mellifera

Moderate

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)

0.052

Oncorhynchus mykiss

High

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

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

> 0.59

Danio rerio Embryo

Moderate

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

0.00078

Daphnia magna

High

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

0.001

Daphnia magna

High

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

0.014

Ceriodaphnia dubia

High

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)

36.7

Chironomus dilutus 10 day LC₅₀

Moderate

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) (EC₅₀)

0.6

Scenedesmus quadricauda

Moderate

Algae - Chronic (growth rate, fresh; mg l⁻¹)

Mesocosm study data

NOEAEC mg l⁻¹

Marine bivalves – Acute EC₅₀, development (mg l⁻¹)

> 0.325

Crassostrea gigas Larva

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)

> 6000

Rat

Low

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

2000

Rabbit

Mammals - Inhalation LC₅₀ (mg l⁻¹)

Other Mammal toxicity endpoints

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

0.1

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

Metabolised and mainly eliminated through the faeces

Health issues

Specific human health issues

Carcinogen

Genotoxic

Endocrine disruptor

; ; ; ;

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

Endocrine issues - strong estrogenic effect
Potential kidney & liver toxicant
IARC Group 3 carcinogen - not classifiable; CLP data - suspected carcingen
May damage vital organs

Handling issues

Property

Value and interpretation

General

Highly flammable and easily ignited by heat, sparks and flames
IMDG Transport Hazard Class 6.1

CLP classification 2013

Health: H302, H312, H332, H351, H371
Environment: H400

WHO Classification

U (Unlikely to present an acute hazard)

UN Number

UN2761

Waste disposal & packaging

Packaging Group III (minor danger)

Shelf-life, storage, stability and reactivity

TRANSLATIONS

Language

Name

English

methoxychlor

French

methoxychlore

German

Methoxychlor

Danish

methoxychlor

Italian

metossicloro

Spanish

metoxiclor

Greek

Polish

metoksychlor

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