Chlorpyrifos-methyl (Ref: OMS 1155)

Chlorpyrifos-methyl (Ref: OMS 1155)	Last updated: 25/04/2025
(Also known as: ENT 27520; Dowco 214; chlorpyriphos-methyl; chlorpyrifos-me)

SUMMARY

An organophosphate broad-spectrum insecticide. It has a low aqueous solubility, is quite volatile and is non-mobile. There is a low risk of leaching to groundwater based on its chemical properties. It tends not to be persistent in soil or water systems. It is not highly toxic to mammals but is classified as an acetyl cholinesterase inhibitor and a neurotoxicant. It is also a skin irritant and sensitiser. It is highly toxic to fish, aquatic invertebrates and honeybees and moderately toxic to birds, aquatic plants, algae and earthworms.

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: Potential for particle bound transport: Medium	Ecotoxicity High alert: Fish chronic ecotoxicity: High; Daphnia acute ecotoxicity: High; Daphnia chronic ecotoxicity: High; Bees acute contact ecotoxicity: High; Bees acute oral ecotoxicity: High	Human health High alert: Endocrine disrupter; Acetyl cholinesterase inhibitor; Neurotoxicant

GENERAL INFORMATION

Description

An insecticide and acaricide used to control soil and foliage pests

Example pests controlled

Scale; Wooly aphid; Leaf roller; Caterpillars; Cutworms; Rootworms; Cockroaches; Flea beetles; Flies; Termites; Fire ants

Example applications

Grains; Cotton; Fruit including apples, pears, grapes, pineapples, bananas, strawberries, mango; Tomatoes; Nuts; Vegetables including carrots, cabbages, cauliflower

Efficacy & activity

Chlorpyrifos has been used very successfully over a long period of time to control a wide range of foliar pests on agricultural crops.

Availability status

Current

Introduction & key dates

1966, first reported; 1985, first marketed USA

GB regulatory status

GB COPR regulatory status

Not approved

Date COPR inclusion expires

Not applicable

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

Spain/Poland

Date EC 1107/2009 inclusion expires

Not applicable

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

Chemical structure

Isomerism

None

Chemical formula

C₇H₇Cl₃NO₃PS

Canonical SMILES

COP(=S)(OC)OC1=NC(=C(C=C1Cl)Cl)Cl

Isomeric SMILES

No data

International Chemical Identifier key (InChIKey)

HRBKVYFZANMGRE-UHFFFAOYSA-N

International Chemical Identifier (InChI)

InChI=1S/C7H7Cl3NO3PS/c1-12-15(16,13-2)14-7-5(9)3-4(8)6(10)11-7/h3H,1-2H3

2D structure diagram/image available?

Yes

Cambridge Crystallographic Data Centre diagrams

Common Name	Relationship	Link
chlorpyrifos	Parent
chlorpyrifos-methyl	-

General status

Pesticide type

Insecticide; Acaricide

Substance groups

Organophosphate insecticide; Organophosphate acaricide; Organothiophosphate insecticide; Organothiophosphate acaricide

Minimum active substance purity

960 g kg⁻¹

Known relevant impurities

EU dossier - Sulfotep <3.0 g kg⁻¹, Sulfotep-ester <5.0 g kg⁻¹

Substance origin

Synthetic

Mode of action

Non-systemic with contact, stomach and respiratory action. Acetylcholinesterase (AChE) inhibitor.

CAS RN

5598-13-0

EC number

227-011-5

CIPAC number

486

US EPA chemical code

059102/219300

PubChem CID

21803

CLP index number

015-084-00-4

Molecular mass

322.53

PIN (Preferred Identification Name)

O,O-dimethyl O-(3,5,6-trichloropyridin-2-yl) phosphorothioate

IUPAC name

O,O-dimethyl O-3,5,6-trichloro-2-pyridyl phosphorothioate

CAS name

O,O-dimethyl O-(3,5,6-trichloro-2-pyridinyl) phosphorothioate

Other status information

OSPAR soc; WFD priority substance; Marine Pollutant; PAN Bad Actor Chemical

Relevant Environmental Water Quality Standards

UK Environment Agency non-statutory standard for the protection of aquatic life: Freshwater annual average 0.002 µg l⁻¹, max acceptable conc 0.01 µg l⁻¹; Saltwater annual average 0.001 µg l⁻¹, max acceptable conc 0.01 µg l⁻¹

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

blattella germanica, culex tarsalis, plutella xylostella, sitophilus zeamais, tribolium castaneum, aedes nigromaculis, plus others

Physical state

White to pale yellow solid with faint characteristic odour

Related substances & organisms

chlorpyrifos

Formulations

Property

Value

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

Dow AgroSciences

Example products using this active

Reldane 22
Gustafson 2% Reldan Dust Insecticide
Storcide EC

Formulation and application details

Usually supplied as an emulsifiable concentrate that is mixed with water and applied as a spray

ENVIRONMENTAL FATE

Property

Value

Source; quality score; and other information

Interpretation

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

2.74

Low

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

250000

Ethyl acetate

250000

Acetone

154000

Heptane

193000

Methanol

Melting point (°C)

Boiling point (°C)

Decomposes before boiling

Degradation point (°C)

175

Flashpoint (°C)

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

1.00 X 10⁰⁴

Calculated

Log P

4.00

High

Fat solubility of residues

Solubility

Soluble

Data type

Regulatory data - observed in metabolism and farm animal feeding studies

Density (g ml⁻¹)

1.67

Dissociation constant pKa) at 25 °C

Vapour pressure at 20 °C (mPa)

3.0

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

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

0.235

Moderately volatile

Volatilisation as max % of applied dose lost

From plant surface

From soil surface

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

Neutral soln: 203nm=20322, 230nm=10112, 290nm=5449
Acidic soln: 203nm=20367, 230nm=9567, 290nm=5473
Basic soln: 242nm=9475, 290nm=1423, 323nm=6817

Surface tension (mN m⁻¹)

71.9

Degradation

Property

Value

Source; quality score; and other information

Interpretation

General biodegradability

Soil degradation (days) (aerobic)

DT₅₀ (typical)

2.77

Non-persistent

DT₅₀ (lab at 20 °C)

2.77

Non-persistent

DT₅₀ (field)

1.24

Non-persistent

DT₉₀ (lab at 20 °C)

13.0

Non-persistent

DT₉₀ (field)

4.5

DT₅₀ modelling endpoint

7.64

Note

EU 2017 dossier Lab studies DT₅₀ (normalised) range 0.879-10.69 days, DT₉₀ (measured) range 2.75-36.6 days, Soils=12, Field studies DT₅₀ range 0.62-2.17 days, DT₉₀ range 2.07-7.22 days, Soils=5; Other sources: DT₅₀ 7 days (DW4)

Dissipation rate RL₅₀ (days) on plant matrix

Value

2.4

Note

Bermuda grass leaves, n=1

Dissipation rate RL₅₀ (days) on and in plant matrix

Value

19.1

Note

Published literature RL₅₀ range 1.0-71.5 days, 4 field crops, various matrices, n=4

Aqueous photolysis DT₅₀ (days) at pH 7

Value

1.74

Moderately fast

Note

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

Value

Non-persistent

Note

pH sensitive: 27 days at pH 4, 13 days at pH 9, 25 °C

Water-sediment DT₅₀ (days)

Fast

Water phase only DT₅₀ (days)

2.9

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

[Wheat grain: 19 wks @ 30 DegC, 50% RH; Modelled data], [Wheat: 17 wks @ 16 Deg C, 13.3 wks @ 23 DegC, 8.6 wks @ 30 DegC, 13% grain moisture; Field study], [Wheat: 41.7 wks @ 16 Deg C, 24.1 wks @ 23 DegC, 12.1 wks @ 30 DegC, 16% grain moisture; Field study], [Corn grain: 27.7 days @ 20-25 DegC, 40-60% RH; Lab study]

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)

4645

Notes and range

EU dossier K_oc range 1189-8100 mL g⁻¹

Freundlich

K_f (mL g⁻¹)

44.9

Slightly mobile

K_foc (mL g⁻¹)

1462

¹/_n

0.96

Notes and range

EU 2017 dossier K_f range 25.8-64.5 mL g⁻¹, K_foc range 691-1892 mL g⁻¹, ¹/_n range 0.93-0.98, Soils=5

pH sensitivity

Fate indices

Property

Value

Source; quality score; and other information

Interpretation

GUS leaching potential index

0.08

Calculated

Low leachability

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

Value

2.44 X 10^-04

Calculated

Note

Potential for particle bound transport index

Medium

Calculated

Potential for loss via drain flow

Non-mobile

Calculated

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

2.11

Calculated using the Atkinson method

Below the level of concern for long-range air transport

Bio-concentration factor

BCF (l kg⁻¹)

1800

Threshold for concern

CT₅₀ (days)

2.6

Known soil metabolites

Metabolite

Major/Minor fraction

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

Estimated maximum occurrence fraction

Notes

3,5,6-trichloro-2-pyridinol

Major fraction

0.879

2,3,5-trichloro-6-methoxypyridine

Minor fraction

0.049

chlorpyrifos (Ref: OMS 971)

Major fraction

N-methyl-dichloro-2-pyridinone

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)

5000

Rat

Low

Mammals - Short term dietary NOEL

(mg kg⁻¹)

0.1

Rat 2 yr

High

(ppm diet)

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

Birds - Acute LD₅₀ (mg kg⁻¹)

923

Colinus virginianus

Moderate

Birds - Short term dietary (LC₅₀/LD₅₀)

2010 ppm

Colinus virginianus

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

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

182

Eisenia foetida

Moderate

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

12.5

Eisenia foetida

Moderate

Soil micro-organisms

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

Dose: 0.5 kg ha⁻¹

Collembola

Acute LC₅₀ (mg kg⁻¹)

Chronic NOEC (mg kg⁻¹)

0.075

Folsomia candida

Non-target plants

Honeybees (Apis spp.)

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

0.148

Apis mellifera

High

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

0.177

Apis mellifera

High

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

Chronic as 10-day LC₅₀ µg bee⁻¹ day⁻¹

0.002

Apis mellifera

Notes

Bumblebees (Bombus spp.)

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

0.09

Bombus terrestris 48 hr

High

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

> 0.36

Bombus terrestris

High

Literature LD₅₀ values range >0.02 - 0.38 µg bee⁻¹ depending on study exposure time

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)

9.0% Mortality at dose 0.12 kg ha⁻¹, 48 hr

Coccinella septempunctata Adults

Beneficial insects (Lacewings) as Mortality LR₅₀ g ha⁻¹

36.89

Chrysoperla carnea Larva

Beneficial insects (Parasitic wasps) as Mortality LR₅₀ g ha⁻¹

0.56

Aphidius rhopalosiphi Adult

Beneficial insects (Predatory mites) as Mortality LR₅₀ g ha⁻¹

158.25

Typhlodromus pyri Protonymph

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)

0.41

Oncorhynchus mykiss

Moderate

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

0.005

Oncorhynchus mykiss

High

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

9.88

Danio rerio EC₅₀ Embryo

Moderate

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

0.0006

Daphnia magna

High

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

0.00001

Daphnia magna

High

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, 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)

0.57

Raphidocelis subcapitata

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)

5000

Rat

Low

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

2000

Rat

Mammals - Inhalation LC₅₀ (mg l⁻¹)

> 0.67

Rat (whole body)

Other Mammal toxicity endpoints

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

None allocated

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

None allocated

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

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

None allocated

Dermal penetration studies (%)

Dangerous Substances Directive 76/464

List I; List II

Exposure Routes

Public

Occupational

Absorbed from the gastrointestinal tract and through intact skin

MRLs

European

EU MRL pesticide database

Great Britain

GB MRL Register

Notes

Drinking Water Standards

Non-statutory WHO drinking water guideline 0.03 mg l⁻¹

UK EA QS database 2018

Drinking Water MAC (μg l⁻¹)

Mammalian dose elimination route and rate

Extensively metabolised, and eliminated maily via the urine within 72 hrs

Health issues

Specific human health issues

Carcinogen

Genotoxic

Endocrine disruptor

; ; ; ;

Reproduction / development effects

Acetyl cholinesterase inhibitor

Neurotoxicant

No data found

Respiratory tract irritant

Skin irritant

Skin sensitiser

Eye irritant

Phototoxicant

General human health issues

Suspected cardiovascular & blood toxicant
Highly toxic by ingestion
Some studies indicate a link between chlorpyrifos metabolites and learning difficulties in children
Endocrine issues - Antagonist to androgen activity

Handling issues

Property

Value and interpretation

General

Not explosive or oxidising
IMDG Transport Hazard Class 6.1
Not expected to auto-ignite; Not highly flammable

CLP classification 2013

Health: H317
Environment: H400, H410

WHO Classification

III (Slightly hazardous)

UN Number

UN2811

Waste disposal & packaging

Packaging Group III (minor danger)

Shelf-life, storage, stability and reactivity

TRANSLATIONS

Language

Name

English

chlorpyrifos-methyl

French

chlorpyriphos-methyl

German

Chlorpyrifos-methyl

Danish

chlorpyrifos-methyl

Italian

clorpirifos-metile

Spanish

clorpirifos-metil

Greek

chlorpyrifos-methyl

Polish

chloropyrifos metylowy

Swedish

Hungarian

klorpirosz-metil

Dutch

chloorpyrifos-methyl

Norwegian

Record last updated:	25/04/2025
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