Parathion-methyl (Ref: OMS 213)

Parathion-methyl (Ref: OMS 213)	Last updated: 17/06/2025
(Also known as: metaphos; meptox; thiophenit; quinophos; methyl-parathion)

SUMMARY

Data alerts

The following alerts are based on the data in the tables below. An absence of an alert does not imply the substance has no implications for human health, biodiversity or the environment but just that we do not have the data to form a judgement.

Environmental fate	Ecotoxicity	Human health
Environmental fate Moderate alert: Drainflow: Moderately mobile	Ecotoxicity High alert: Fish chronic ecotoxicity: High; Daphnia acute ecotoxicity: High; Daphnia chronic ecotoxicity: High	Human health High alert: Mammals acute toxicity: High; Acetyl cholinesterase inhibitor; Neurotoxicant

GENERAL INFORMATION

Description

An insecticide used to control sucking and chewing insects in a wide range of crops

Example pests controlled

Aphids; Boll weevils; Mealybugs; Scale; Armyworms

Example applications

Cereals; Cotton; Vegetables; Soybean; Fruit; Vines

Efficacy & activity

Availability status

Current

Introduction & key dates

circa 1950, introduced

GB regulatory status

GB COPR regulatory status

Not approved

Date COPR inclusion expires

Expired

GB LERAP status

No UK approval for use as a plant protection agent

EC Regulation 1107/2009 (repealing 91/414)

EC Regulation 1107/2009 status

Not approved

Dossier rapporteur/co-rapporteur

Italy

Date EC 1107/2009 inclusion expires

Expired

EU Candidate for substitution (CfS)

Listed in EU database

Yes

Approved for use (✓) under EC 1107/2009 in the following EU Member States

ATAustria	BEBelgium	BGBulgaria	CYCyprus	CZCzech Republic	DEGermany	DKDenmark	EEEstonia	ELGreece

ESSpain	FIFinland	FRFrance	HRCroatia	HUHungary	IEIreland	ITItaly	LTLithuania	LULuxembourg

LVLatvia	MTMalta	NLNetherlands	PLPoland	PTPortugal	RORomania	SESweden	SISlovenia	SKSlovakia

Approved for use (✓) under EC 1107/2009 by Mutual Recognition of Authorisation and/or national regulations in the following EEA countries

ISIceland	NONorway

Additional information

Also used in

Australia; USA; Costa Rica

Chemical structure

Isomerism

None

Chemical formula

C₈H₁₀NO₅PS

Canonical SMILES

COP(=S)(OC)OC1=CC=C(C=C1)[N+](=O)[O-]

Isomeric SMILES

No data

International Chemical Identifier key (InChIKey)

RLBIQVVOMOPOHC-UHFFFAOYSA-N

International Chemical Identifier (InChI)

InChI=1S/C8H10NO5PS/c1-12-15(16,13-2)14-8-5-3-7(4-6-8)9(10)11/h3-6H,1-2H3

2D structure diagram/image available?

Yes

Cambridge Crystallographic Data Centre diagrams

Common Name	Relationship	Link
parathion-methyl	-

General status

Pesticide type

Insecticide

Substance groups

Organophosphate insecticide; Organophosphate acaricide; Organothiophosphate insecticide; Organothiophosphate acaricide

Minimum active substance purity

Known relevant impurities

Substance origin

Synthetic

Mode of action

Contact and stomach insecticide. Acetylcholinesterase (AchE) inhibitor.

CAS RN

298-00-0

EC number

206-050-1

CIPAC number

487

US EPA chemical code

053501

PubChem CID

4130

CLP index number

015-035-00-7

Molecular mass

263.21

PIN (Preferred Identification Name)

IUPAC name

O,O-dimethyl O-4-nitrophenyl phosphorothioate

CAS name

O,O-dimethyl O-(4-nitrophenyl) phosphorothioate

Other status information

May be subject to PIC regulations; Potential groundwater contaminant; Marine Pollutant; Subject to the provisions of the UK Poisons Act 1972

Relevant Environmental Water Quality Standards

Herbicide Resistance Class (HRAC MoA class)

Not applicable

Herbicide Resistance Class (WSSA MoA class)

Not applicable

Insecticide Resistance Class (IRAC MoA class)

Fungicide Resistance Class (FRAC MOA class)

Not applicable

Examples of recorded resistance

Aedes melanimon, Aedes nigromaculis, Anopheles albimanus, Coleomegilla maculata, Culex pipiens pallens, many others

Physical state

Colourless crystals

Related substances & organisms

parathion-ethyl

dicapthon

Formulations

Property

Value

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

Bayer CropScience
FCC Ltd
Cheminova A/S
Monsanto

Example products using this active

Sweeper
Amithion
Prompt
Sabidol
Wolfatox

Formulation and application details

Available in a wide variety of formulations including dustable powders, emulsifible concentrates, encapsulated suspensions, ULV liquid and wettable powders.

ENVIRONMENTAL FATE

Property

Value

Source; quality score; and other information

Interpretation

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

Moderate

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

200000

Dichloromethane

200000

Toluene

15000

Hexane

Melting point (°C)

35.5

Boiling point (°C)

Degradation point (°C)

Flashpoint (°C)

150

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

1.00 X 10⁰³

Calculated

Log P

Moderate

Fat solubility of residues

Solubility

Data type

Density (g ml⁻¹)

1.36

Dissociation constant pKa) at 25 °C

Vapour pressure at 20 °C (mPa)

0.2

Low volatility. If applied directly to plants, drift is a concern & mitigation is advisable

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

8.57 X 10^-03

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)

Degradation

Property

Value

Source; quality score; and other information

Interpretation

General biodegradability

Soil degradation (days) (aerobic)

DT₅₀ (typical)

Non-persistent

DT₅₀ (lab at 20 °C)

Non-persistent

DT₅₀ (field)

Non-persistent

DT₉₀ (lab at 20 °C)

DT₉₀ (field)

DT₅₀ modelling endpoint

Note

PIC DGD states lab DT₅₀ range 1-18 days

Dissipation rate RL₅₀ (days) on plant matrix

Value

3.6

Note

Published literature RL₅₀ range 0.4-6.7 days, 6 field crops, various matrices, n=8

Dissipation rate RL₅₀ (days) on and in plant matrix

Value

1.9

Note

Published literature RL₅₀ range 0.7-6.6 days, 7 field crops, various matrices, n=12; Fruit in cold storage RL₅₀ range 63-65 days, n=2

Aqueous photolysis DT₅₀ (days) at pH 7

Value

Moderately fast

Note

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

Value

Non-persistent

Note

Water-sediment DT₅₀ (days)

Fast

Water phase only DT₅₀ (days)

Slow

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)

Moderately mobile

K_oc (mL g⁻¹)

240

Notes and range

Freundlich

K_f (mL g⁻¹)

34.4

Moderately mobile

K_foc (mL g⁻¹)

442

¹/_n

1.038

Notes and range

Literature data: K_f range 8.0-37.8 (178 for peat) mL g⁻¹, K_foc range 276-677 (276 for peat) mL g⁻¹, ¹/_n range 0.909-1.123, Soils=8

pH sensitivity

Fate indices

Property

Value

Source; quality score; and other information

Interpretation

GUS leaching potential index

1.35

Calculated

Low leachability

SCI-GROW groundwater index (μg l⁻¹) for a 1 kg ha⁻¹ or 1 l ha⁻¹ application rate

Value

1.93 X 10^-02

Calculated

Note

Potential for particle bound transport index

Low

Calculated

Potential for loss via drain flow

Moderately mobile

Calculated

Photochemical oxidative DT₅₀ (hrs) as indicator of long-range air transport risk

Bio-concentration factor

BCF (l kg⁻¹)

Oncorhynchus mykiss

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)

Rat

High

Mammals - Short term dietary NOEL

(mg kg⁻¹)

Rat 2 yr

(ppm diet)

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

Birds - Acute LD₅₀ (mg kg⁻¹)

> 1044

Anas platyrhynchos

Moderate

Birds - Short term dietary (LC₅₀/LD₅₀)

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

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

Eisenia foetida

Moderate

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

Soil micro-organisms

Collembola

Acute LC₅₀ (mg kg⁻¹)

Chronic NOEC (mg kg⁻¹)

Non-target plants

Honeybees (Apis spp.)

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

19.5

Apis mellifera

Moderate

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

750

Apis mellifera

Low

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

Chronic

Notes

[The residual time to 25% mortality (RT25) value for honeybees is 189 hrs (range 171-207 hrs) - USEPA data]

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)

0.0157

Megachile rotundata

High

Mode of exposure

Contact

Other bee species (2)

Acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg insect⁻¹)

0.096

Trigona spinipes

High

Mode of exposure

Contact

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)

> 2.7

Oncorhynchus mykiss

Moderate

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

0.0089

Cyprinodon variegatus

High

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

6.88

Danio rerio EC₅₀ Embryo 5 day

Moderate

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

> 0.0073

Daphnia magna

High

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

0.00018

Daphnia magna

High

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

> 0.0008

Ceriodaphnia dubia

High

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

0.00035

Americamysis bahia

High

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)

115

Chironomus dilutus Growth

Low

Aquatic plants (free-floating, growth) - Acute 7 day EC₅₀, biomass (mg l⁻¹)

Aquatic plants (rooted, growth) - Acute 14 day EC₅₀, biomass (mg l⁻¹)

Algae - Acute 72 hour EC₅₀, growth (mg l⁻¹)

Scenedesmus subspicatus

Moderate

Algae - Chronic 96 hour NOEC, growth (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)

45.0

Rat

Mammals - Inhalation LC₅₀ (mg l⁻¹)

0.17

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

Skin absorption, and to a lesser extent inhalation and ingestion

MRLs

European

EU MRL pesticide database

Great Britain

GB MRL Register

Notes

Drinking Water Standards

Drinking Water MAC (μg l⁻¹)

Mammalian dose elimination route and rate

Almost completely excreted by the kidneys (urine) within 24 hours as phenolic metabolites

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

Extremely hazardous
IARC Group 3 carcinogen - not classifiable; US EPA - not likely to be a human carcinogen

Handling issues

Property

Value and interpretation

General

Explosive on heating
Flammable
IMDG Transport Hazard Class 6.1

CLP classification 2013

Handling: H226
Health: H300, H311, H330, H373
Environment: H400, H410

WHO Classification

Ia (Extremely hazardous)

UN Number

UN2783

Waste disposal & packaging

Shelf-life, storage, stability and reactivity

TRANSLATIONS

Language

Name

English

parathion-methyl

French

parathion-methyl

German

Parathion-methyl

Danish

parathion-methyl

Italian

paration-metile

Spanish

paratión-metil

Greek

parathion-methyl

Polish

paration metylu

Swedish

Hungarian

Dutch

parathion-methyl

Norwegian

Record last updated:	17/06/2025
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