Chloroxuron (Ref: C 1983)

Chloroxuron (Ref: C 1983)	Last updated: 30/04/2021
(Also known as: chloroxyphenidin; chloroxyfenidim )

SUMMARY

Chloroxuron is a herbicide that is no longer approved for use in the UK or the EU. It has a low aqueous solubility and is not volatile. It is moderately persistent in soil systems but is unlikely to persist in aquatic systems. Based on its physico-chemical properties it is not expected to leach to groundwater. It is moderately toxic to birds, fish, aquatic invertebrates, algae and honey bees. Mammalian toxicity is low.

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: Moderately persistent; Drainflow: Slightly mobile; Potential for particle bound transport: Medium	Ecotoxicity Moderate alert: Birds acute ecotoxicity: Moderate; Fish acute ecotoxicity: Moderate; Daphnia acute ecotoxicity: Moderate; Bees acute contact ecotoxicity: Moderate	Human health Moderate alert: Possible Carcinogen

GENERAL INFORMATION

Description

An obsolete selective phenylurea herbicide once used to control annual grasses, mosses and broad-leaved weeds

Example pests controlled

Barnyardgrass; Nightshade; Carpetweed; Corn cockle; Dandelion; Goosegrass; Crabgrass; Ragweed; Puslane; Shepherd's purse; Pigweed; Velvetleaf

Example applications

Soybeans; Onions; Strawberries; Celery; Ornamentals; vegetables including onions, carrots, leeks, peas & beans

Efficacy & activity

Availability status

Considered obsolete but may be available in some countries

Introduction & key dates

1961, first reported

UK regulatory status

UK COPR regulatory status

Not approved

Date COPR inclusion expires

Expired

UK LERAP status

No UK approval for use

EC Regulation 1107/2009 (repealing 91/414)

EC Regulation 1107/2009 status

Not approved

Dossier rapporteur/co-rapporteur

Not applicable

Date EC 1107/2009 inclusion expires

Expired

EU Candidate for substitution (CfS)

Not applicable

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

Additional information

Also used in

Chemical structure

Isomerism

Chemical formula

C₁₅H₁₅ClN₂O₂

Canonical SMILES

CN(C)C(=O)NC1=CC=C(C=C1)OC2=CC=C(C=C2)Cl

Isomeric SMILES

No data

International Chemical Identifier key (InChIKey)

IVUXTESCPZUGJC-UHFFFAOYSA-N

International Chemical Identifier (InChI)

InChI=1S/C15H15ClN2O2/c1-18(2)15(19)17-12-5-9-14(10-6-12)20-13-7-3-11(16)4-8-13/h3-10H,1-2H3,(H,17,19)

2D structure diagram/image available?

Yes

General status

Pesticide type

Herbicide

Substance group

Dimethylurea

Minimum active substance purity

Known relevant impurities

Substance origin

Synthetic

Mode of action

Photosynthetic electron transport inhibitor at the photosystem II receptor. Growth inhibition and chlorotic and necrotic effects on foliage

CAS RN

1982-47-4

EC number

217-843-7

CIPAC number

187

US EPA chemical code

025501

PubChem CID

16115

Molecular mass

290.75

PIN (Preferred Identification Name)

N'-[4-(4-chlorophenoxy)phenyl]-N,N-dimethylurea

IUPAC name

3-[4-(4-chlorophenoxy)phenyl]-1,1-dimethylurea

CAS name

N'-[4-(4-chlorophenoxy)phenyl]-N,N-dimethylurea

Other status information

Relevant Environmental Water Quality Standards

Herbicide Resistance Classification (HRAC)

Herbicide Resistance Classification (WSSA)

Insecticide Resistance Classification (IRAC)

Not applicable

Fungicide Resistance Classification (FRAC)

Not applicable

Examples of recorded resistance

Physical state

Solid

Formulations

Property

Value

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

Syngenta
Ciba Geigy AG

Example products using this active

Tenoran
Norex
Gesamoos

Formulation and application details

Usually supplied as a wettable powder

ENVIRONMENTAL FATE

Property

Value

Source; quality score; and other information

Interpretation

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

3.7

Low

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

44000

Acetone

106000

Dichloromethane

4000

Toluene

35000

Toluene

Melting point (°C)

151

Boiling point (°C)

Degradation point (°C)

Flashpoint (°C)

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

2.51 X 10⁰³

Calculated

Log P

3.4

High

Bulk density (g ml⁻¹)

Dissociation constant pKa) at 25 °C

Vapour pressure at 20 °C (mPa)

2.30 X 10^-04

Low volatility

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

6.00 X 10^-05

Non-volatile

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)

Moderately persistent

DT₅₀ (lab at 20 °C)

DT₅₀ (field)

Moderately persistent

DT₉₀ (lab at 20 °C)

DT₉₀ (field)

DT₅₀ modelling endpoint

Note

Literature states DT₅₀ typically ranges from 30 to 60 days, 110 days silt loam aerobic conditions (CA3)

Dissipation rate RL₅₀ on plant matrix

Value

Note

Dissipation rate RL₅₀ on and in plant matrix

Value

Note

Aqueous photolysis DT₅₀ (days) at pH 7

Value

0.015

Fast

Note

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

Value

2896

Very persistent

Note

Water-sediment DT₅₀ (days)

Water phase only DT₅₀ (days)

Stable

Soil adsorption and mobility

Property

Value

Source; quality score; and other information

Interpretation

Linear

K_d

Slightly mobile

K_oc

2820

Notes and range

Best available data

Freundlich

K_f

K_foc

¹/_n

Notes and range

pH sensitivity

Fate indices

Property

Value

Source; quality score; and other information

Interpretation

GUS leaching potential index

0.98

Calculated

Low leachability

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

Value

1.96 X 10^-02

Calculated

Note

Potential for particle bound transport index

Medium

Calculated

Potential for loss via drain flow

Slightly mobile

Calculated

Key metabolites

Metabolite

Formation medium

Estimated maximum occurrence fraction

1107/2009 relevancy

N-(4-chlorophenoxy)-phenyl-N-methylurea

Soil

Not assessed under 91/414 or 1107/2009

N-(4-chlorophenoxy)-phenylurea

Soil

Not assessed under 91/414 or 1107/2009

4-chlorophenoxy-aniline

Soil

Not assessed under 91/414 or 1107/2009

ECOTOXICOLOGY

Property

Value

Source; quality score; and other information

Interpretation

Bio-concentration factor

BCF (l kg⁻¹)

105

Estimated

Threshold for concern

CT₅₀ (days)

Not available

Mammals - Acute oral LD₅₀ (mg kg⁻¹)

> 3700

Rat

Low

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)

2000

Anas platyrhynchos

Moderate

Birds - Short term dietary (LC₅₀/LD₅₀)

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

Fish - Acute 96 hour LC₅₀ (mg l⁻¹)

100

Oncorhynchus mykiss

Moderate

Fish - Chronic 21 day NOEC (mg l⁻¹)

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

2.95

Daphnia magna

Moderate

Aquatic invertebrates - Chronic 21 day NOEC (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 - Acute 7 day EC₅₀, biomass (mg l⁻¹)

Non-target plants

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

0.016

Unknown species

Moderate

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

Honeybees (Apis spp.)

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

Moderate

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)

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 pollinators (1)

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

Mode of exposure

Other pollinators (2)

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

Mode of exposure

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

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

Other soil macro-organisms

Acute LC₅₀ (mg kg⁻¹)

Chronic NOEC (mg kg⁻¹)

Other arthropod (1)

LR₅₀ g ha⁻¹

% Effect

Other arthropod (2)

LR₅₀ g ha⁻¹

% Effect

Soil micro-organisms

Mesocosm study data

NOEAEC mg l⁻¹

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)

> 3700

Rat

Low

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

Mammals - Inhalation LC₅₀ (mg l⁻¹)

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

Exposure Routes

Public

Occupational

Occupational exposure may occur through inhalation of dusts and dermal contact

MRLs

European

EU MRL pesticide database

Great Britain

GB MRL Register

Notes

Drinking Water Standards

Drinking Water MAC (μg l⁻¹)

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

No data found

Eye irritant

Phototoxicant

No data found

General human health issues

Harmful by ingestion and inhalation
May be harmful by skin contact
Under certain conditions may form carcinogenic dimethylnitrosamine

Handling issues

Property

Value and interpretation

General

Fire may produce irritating or poisonous gases

CLP classification 2013

Health: H332
Environment: H400

EC Risk Classification

Xn - Harmful: R20, R22

EC Safety Classification

WHO Classification

U (Unlikely to present an acute hazard)

UN Number

Waste disposal & packaging

TRANSLATIONS

Language

Name

English

chloroxuron

French

chloroxuron

German

Chloroxuron

Danish

chloroxuron

Italian

cloroxuron

Spanish

cloroxuron

Greek

Polish

chloroksuron

Swedish

Hungarian

Dutch

chloroxuron

Record last updated:	30/04/2021
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