Chlorpyrifos (Ref: OMS 971)

Chlorpyrifos (Ref: OMS 971)	Last updated: 10/04/2025
(Also known as: ENT 27311; chlorpyriphos; Dowco 179; chlorpyrifos ethyl)

SUMMARY

An organophosphate 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 can be moderately persistent in soil systems but is not usually persistent in water systems. It is highly toxic to mammals, is classified as a reproduction toxicant, an acetyl cholinesterase inhibitor and a neurotoxicant. It is also a skin and eye irritant. It is highly toxic to birds, fish, aquatic invertebrates and honeybees and moderately toxic to 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: Birds acute ecotoxicity: High; Birds chronic ecotoxicity: High; Fish acute ecotoxicity: High; Fish chronic ecotoxicity: High; Daphnia acute ecotoxicity: High; Daphnia chronic ecotoxicity: High; Bees acute contact ecotoxicity: High; Bees acute oral ecotoxicity: High; Earthworms chronic ecotoxicity: High	Human health High alert: Mammals acute toxicity: High; Mammals chronic toxicity: High; Endocrine disrupter; Reproduction/development effects; Acetyl cholinesterase inhibitor; Neurotoxicant

GENERAL INFORMATION

Description

A broad-spectrum organophosphorus insecticide and acaricide used to control soil and foliage pests

Example pests controlled

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

Example applications

Cereals including barley, wheat; Cotton; Fruit including apples, pears, grapes, pineapples, bananas, strawberries, mango; Tomatoes; Nuts; Vegetables inclding carrots, cabbages, cauliflower, Brussel sprouts; Ornamentals

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

1965, first reported and introduced

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

Australia

Chemical structure

Isomerism

None

Chemical formula

C₉H₁₁Cl₃NO₃PS

Canonical SMILES

CCOP(=S)(OCC)OC1=NC(=C(C=C1Cl)Cl)Cl

Isomeric SMILES

No data

International Chemical Identifier key (InChIKey)

SBPBAQFWLVIOKP-UHFFFAOYSA-N

International Chemical Identifier (InChI)

InChI=1S/C9H11Cl3NO3PS/c1-3-14-17(18,15-4-2)16-9-7(11)5-6(10)8(12)13-9/h5H,3-4H2,1-2H3

2D structure diagram/image available?

Yes

Cambridge Crystallographic Data Centre diagrams

Common Name	Relationship	Link
chlorpyrifos	-

General status

Pesticide type

Insecticide

Substance groups

Organophosphate insecticide; Organophosphate acaricide; Organothiophosphate insecticide; Organothiophosphate acaricide

Minimum active substance purity

970 g kg⁻¹

Known relevant impurities

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

Substance origin

Synthetic

Mode of action

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

CAS RN

2921-88-2

EC number

220-864-4

CIPAC number

221

US EPA chemical code

059101

PubChem CID

2730

CLP index number

015-084-00-4

Molecular mass

350.58

PIN (Preferred Identification Name)

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

IUPAC name

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

CAS name

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

Other status information

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

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

Aedes aegypti, Aedes nigromaculis, Anopheles pharoensis, Bemisia argentifolii, Culex pipiens pipiens, Helicoverpa armigera, Plutella xylostella, Spodoptera litura, Tribolium castaneum, plus others

Physical state

White to light brown coloured crystals

Related substances & organisms

chlorpyrifos-methyl

Formulations

Property

Value

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

Dow AgroSciences
Headland
Makhteshim-Agan
SumiAgro
Scotts

Example products using this active

Alpha Chlorpyrifos
Ballad
Cyren
Dursban WG
Equity
Govern
Parapet
Hatchet
Lorsban

Formulation and application details

Usually supplied as an emulsifiable concentrates that is mixed with water and applied as a spray. Also supplied as granules for direct application to soil.

ENVIRONMENTAL FATE

Property

Value

Source; quality score; and other information

Interpretation

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

1.05

Low

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

774000

Hexane

290000

Methanol

4000000

Ethyl acetate

4000000

Toluene

Melting point (°C)

Boiling point (°C)

Decomposes before boiling

Degradation point (°C)

170

Flashpoint (°C)

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

5.01 X 10⁰⁴

Calculated

Log P

4.7

High

Fat solubility of residues

Solubility

Soluble

Data type

Regulatory data - observed in metabolism and farm animal feeding studies

Density (g ml⁻¹)

1.51

Dissociation constant pKa) at 25 °C

Not applicable

No dissociation

Vapour pressure at 20 °C (mPa)

1.43

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)

0.478

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=21174, 230nm=10359, 290nm=5620
Acid soln: 203nm=22223, 230nm=10347, 290nm=5907
Alkaline soln: 242nm=9413, 290nm=1633, 323nm=6701

Surface tension (mN m⁻¹)

Degradation

Property

Value

Source; quality score; and other information

Interpretation

General biodegradability

Not readily biodegradable

Soil degradation (days) (aerobic)

DT₅₀ (typical)

386

Very persistent

DT₅₀ (lab at 20 °C)

386

Very persistent

DT₅₀ (field)

27.6

Non-persistent

DT₉₀ (lab at 20 °C)

250

EU 2005 data

Persistent

DT₉₀ (field)

113

DT₅₀ modelling endpoint

23.4

geometric mean

Note

EU 2017 dossier Lab studies DT₅₀ range 19.8->1000 days, Soils=8, Field - studies DT₅₀ range 0.32-88.9 days, DT₉₀ range 12.2-295 days, Soils =6

Dissipation rate RL₅₀ (days) on plant matrix

Value

3.0

Note

Published literature RL₅₀ range 0.7-10.0 days, 11 field & undercover grown crops, various matrices, n=13

Dissipation rate RL₅₀ (days) on and in plant matrix

Value

7.2

Note

Published literature RL₅₀ range 0.95-127.0 days, 30 field & undercover grown crops, various matrices, n=77

Aqueous photolysis DT₅₀ (days) at pH 7

Value

29.6

Slow

Note

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

Value

53.5

Moderately persistent

Note

pH sensitive 63-73 days at pH 5, 16-23 days at pH 8

Water-sediment DT₅₀ (days)

36.5

Moderately fast

Water phase only DT₅₀ (days)

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

[Soybean: 99 days @ ambient conditions; Lab study], [Wheat grain (dried): 66.9 days @ ~25 DegC, ~80% RH; Lab study]

Soil adsorption and mobility

Property

Value

Source; quality score; and other information

Interpretation

Linear

K_d (mL g⁻¹)

126.6

Non-mobile

K_oc (mL g⁻¹)

5509

Notes and range

EU 2017 dossier K_d range 55.2-295 mL g⁻¹, K_oc range 3187-7733 mL g⁻¹, Soils=5; Other sources: 6070 mL g⁻¹ (DW3), >5000 (E4)

Freundlich

K_f (mL g⁻¹)

91.6

Slightly mobile

K_foc (mL g⁻¹)

3954

¹/_n

0.92

Notes and range

EU 2017 dossier K_f range 45.2-234 mL g⁻¹, K_foc range 1520-5442 mL./g, ¹/_n range 0.86-0.97, Soils=5

pH sensitivity

Fate indices

Property

Value

Source; quality score; and other information

Interpretation

GUS leaching potential index

0.58

Calculated

Low leachability

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

Value

1.10 X 10^-02

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

Bio-concentration factor

BCF (l kg⁻¹)

1374

(Other literature log BCF range 0.8-5.4 (R3)

Threshold for concern

CT₅₀ (days)

2.5

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

0.602

2,3,5-trichloro-6-methoxypyridine

Minor fraction

0.087

Known groundwater metabolites

None

Other known metabolites

Metabolite name and reference

Aliases

Formation medium / Rate

Estimated maximum occurrence fraction

O-ethyl-O-(3,5,6-trichloro-2-pyridyl)phosphorothioic acid

phosphorothioate

Water (Hydrolysis)

>0.100

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

High

(ppm diet)

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

Rat Reproductive NOAEL

High

Birds - Acute LD₅₀ (mg kg⁻¹)

39.2

Colinus virginianus

High

Birds - Short term dietary (LC₅₀/LD₅₀)

203 ppm

Anas platyrhynchos

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

2.885

Anas platyrhynchos NOEC

High

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

129

Eisenia foetida

Moderate

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

0.075

Eisenia foetida corr

High

Soil micro-organisms

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

Dose: 4.8 kg ha⁻¹

Collembola

Acute LC₅₀ (mg kg⁻¹)

Chronic NOEC (mg kg⁻¹)

0.012

Folsomia candida

Non-target plants

Honeybees (Apis spp.)

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

0.068

Apis mellifera

High

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

0.15

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

0.002

Apis mellifera

Notes

[The residual time to 25% mortality (RT25) value for honeybees is 24 hrs - USEPA data]

Bumblebees (Bombus spp.)

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

> 1.58

Bombus terrestris 72 hr

Moderate

Other literature values LD₅₀ range 0.09- 2.39 µg bee⁻¹

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

0.23

Bombus terrestris for methyl variant

High

Mason bees (Osmia spp.)

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

4.19

Osmia bicornis

Moderate

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 LC₅₀ ppm

257.4

Coccinella septempunctata Adult

Beneficial insects (Lacewings)

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

0.2

Aphidius colemani

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

1986

Typhlodromus pyri

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)

0.025

Oncorhynchus mykiss

High

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

0.00014

Oncorhynchus mykiss

High

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

> 0.13

Danio rerio Larva

Moderate

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

0.00010

Daphnia magna

High

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

0.0046

Daphnia magna

High

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

0.00007

Ceriodaphnia dubia

High

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

0.00004

Americamysis bahia

High

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

0.000024

Chironomus riparius

High

Sediment dwelling organisms - Chronic 28 day NOEC, static, water (mg l⁻¹)

0.0001

Chironomus riparius

High

Sediment dwelling organisms - Chronic 28 day NOEC, sediment (mg kg⁻¹)

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

0.53

Lemna minor

Moderate

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

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

0.48

Unknown species

Moderate

Algae - Chronic 96 hour NOEC, growth (mg l⁻¹)

0.043

Unknown species

Moderate

Mesocosm study data

NOEAEC mg l⁻¹

0.1

EAC

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)

1250

Rat

Mammals - Inhalation LC₅₀ (mg l⁻¹)

0.1

Rat (whole body)

Other Mammal toxicity endpoints

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

0.001

Rat SF=100

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)

None allocated

Dermal penetration studies (%)

0.2-25

concentration & product dependent

Dangerous Substances Directive 76/464

List I; List II

Exposure Routes

Public

Possible risks of exposure when close to spraying activity

Occupational

PPE/PPC required to mitigate any expsoure risks

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

Rapidly excreted mainly via the urine (80-90%) and the remainder in 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

Eye irritant

Phototoxicant

General human health issues

Highly toxic by ingestion
Some studies indicate a link between chlorpyrifos metabolites and learning difficulties in children
Suspected cardiovascular & blood toxicant

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: H301
Environment: H400, H410

WHO Classification

II (Moderately hazardous)

UN Number

UN2811

Waste disposal & packaging

Packaging Group III (minor danger)

Shelf-life, storage, stability and reactivity

TRANSLATIONS

Language

Name

English

chlorpyrifos

French

chlorpyriphos

German

Chlorpyrifos

Danish

chlorpyrifos

Italian

clorpirifos

Spanish

clorpirifos

Greek

chlorpyrifos

Polish

chloropyrifos

Swedish

klorpyrifos

Hungarian

chlorpyrifos

Dutch

chloorpyrifos

Norwegian

Record last updated:	10/04/2025
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