Isoxaben (Ref: EAF 496)

Isoxaben (Ref: EAF 496)	Last updated: 15/02/2021
(Also known as: benzamizole; benzamidazole; EL 107)

GENERAL INFORMATION

Description

A broad-spectrum pre-emergence soil-acting amide herbicide for use mainly with grass and fruit to control broad-leaved weeds

Example pests controlled

Broad-leaved weeds including marestail, hairy fleabane, mallow, Shepherd's purse, henbit, checkweed, sowthistle

Example applications

Tree-nut plantations; Orchards; Vinyards; Ornamental trees and shrubs; Winter cereals

Efficacy & activity

Availability status

Current

Introduction & key dates

1984, France

UK regulatory status

UK COPR regulatory status

Approved

Date COPR inclusion expires

31/05/2024

UK LERAP status

None

EC Regulation 1107/2009 (repealing 91/414)

EC Regulation 1107/2009 status

Approved

Dossier rapporteur/co-rapporteur

Austria/Finland

Date EC 1107/2009 inclusion expires

31/05/2021

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
		✓		✓		✓

Also used in

Australia

Chemical structure

Isomerism

Isomeric with the isomers typically comprising around 2% of the product

Chemical formula

C₁₈H₂₄N₂O₄

Canonical SMILES

CCC(C)(CC)C1=NOC(=C1)NC(=O)C2=C(C=CC=C2OC)OC

Isomeric SMILES

No data

International Chemical Identifier key (InChIKey)

PMHURSZHKKJGBM-UHFFFAOYSA-N

International Chemical Identifier (InChI)

InChI=1S/C18H24N2O4/c1-6-18(3,7-2)14-11-15(24-20-14)19-17(21)16-12(22-4)9-8-10-13(16)23-5/h8-11H,6-7H2,1-5H3,(H,19,21)

2D structure diagram/image available?

Yes

General status

Pesticide type

Herbicide

Substance group

Benzamide

Minimum active substance purity

910 g kg⁻¹

Known relevant impurities

EU dossier - toluene 3g kg⁻¹

Substance origin

Synthetic

Mode of action

Selective, disrupts root and stem development in germinating seeds. Inhibition of cell wall synthesis.

CAS RN

82558-50-7

EC number

407-190-8

CIPAC number

701

US EPA chemical code

125851

PubChem CID

73672

Molecular mass

332.39

PIN (Preferred Identification Name)

IUPAC name

N-[3-(1-ethyl-1-methylpropyl)-1,2-oxazol-5-yl]-2,6-dimethoxybenzamide

CAS name

N-(3-(1-ethyl-1-methylpropyl)-5-isoxazolyl)-2,6-dimethoxybenzamide

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 known

Examples of recorded resistance

Physical state

Colourless crystalline solid or waxy powder

Related substances & organisms

terbuthylazine

trifluralin

Formulations

Property

Value

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

Fargro Axit
Skirmish
Flexidor 125
EAF-496

Example products using this active

AgriGuard
Dow AgroSciences
Landseer
Syngenta
Elanco

Formulation and application details

Often supplied as a suspension concentrate

ENVIRONMENTAL FATE

Property

Value

Source; quality score; and other information

Interpretation

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

0.93

Low

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

88000

Ethyl acetate

270000

Acetone

98000

Methanol

4000

Xylene

Melting point (°C)

175.3

Boiling point (°C)

Decomposes before boiling

Degradation point (°C)

200

Flashpoint (°C)

Not expected to self ignite; Not highly flammable

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

8.71 X 10⁰³

Calculated

Log P

3.94

High

Bulk density (g ml⁻¹)

0.58

Dissociation constant pKa) at 25 °C

9.78

Weak acid

Vapour pressure at 20 °C (mPa)

5.50 X 10^-04

Low volatility

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

1.96 X 10^-04

Non-volatile

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

Neutral solution: 252nm = 16500
Acidic solution: 252nm = 16500
Basic solution, 215nm = 11400, 275nm = 20800

Surface tension (mN m⁻¹)

72.9 +/- 0.18

at 19°C

Degradation

Property

Value

Source; quality score; and other information

Interpretation

General biodegradability

Soil degradation (days) (aerobic)

DT₅₀ (typical)

105

Persistent

DT₅₀ (lab at 20 °C)

301

Persistent

DT₅₀ (field)

123

Persistent

DT₉₀ (lab at 20 °C)

1017.5

Very persistent

DT₉₀ (field)

407.1

DT₅₀ modelling endpoint

Note

EU dossier lab studies DT₅₀ range 127-891 days (normalised), DT₉₀ range 421-2952 days; field studies DT₅₀ range 66-309 days, DT₉₀ range 219-1028 dats

Dissipation rate RL₅₀ on plant matrix

Value

6.7

Note

Published literature RL₅₀ range 5.0-8.4 days, 2 field crops, various matrices, n=2

Dissipation rate RL₅₀ on and in plant matrix

Value

3.8

Note

Turf grass blades, n=1

Aqueous photolysis DT₅₀ (days) at pH 7

Value

Moderately fast

Note

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

Value

Stable

Note

Stable pH 5 to pH 9

Water-sediment DT₅₀ (days)

16.8

Fast

Water phase only DT₅₀ (days)

8.8

Moderately fast

Soil adsorption and mobility

Property

Value

Source; quality score; and other information

Interpretation

Linear

K_d

8.7

Slightly mobile

K_oc

909

Notes and range

EU dossier K_d range 6.43-12.6 mL g⁻¹, K_oc range 700-1290 mL g⁻¹, Soils=4

Freundlich

K_f

3.3

Moderately mobile

K_foc

354

¹/_n

0.905

Notes and range

EU dossier K_f range 0.81-6.63 mL g⁻¹, K_foc range 190-570 mL g⁻¹, ¹/_n range 0.892-0.911, Soils=5

pH sensitivity

Fate indices

Property

Value

Source; quality score; and other information

Interpretation

GUS leaching potential index

3.03

Calculated

High leachability

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

Value

3.43 X 10^-01

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-(3-(1-hydroxy-1-methyl-propyl)-5-isoxazolyl)-2,6,dimethoxybenzamide

Soil

0.108

Major fraction, Relevancy unknown

N-(3-(1-ethyl-1-methyl-2-oxypropyl)isoxazol-5-yl)-2,6-dimethoxybenzamide

Soil

0.073

Minor fraction, Relevancy unknown

N-(3-amino-4-ethyl-4-methyl-2-hexenoyl)-2,6-dimethoxybenzamide

Soil

0.60

Major fraction; Relevant

2,6-dimethoxybenzamide

Soil

0.129

Major fraction; Relevant

Other known metabolites

Metabolite name and reference

Aliases

Formation medium / Rate

Estimated maximum occurrence fraction

Metabolising enzymes

6-(1-ethyl-1-methylpropyl)-2-(2-hydroxy-6-methoxyphenyl)-4-pyrimidinol
Note: DT50 soil 47 days

methoxyphenyl pyrimidinol

Soil (Anaerobic)

0.331

2-hydroxy-6-methoxybenzamide

hydroxymethoxy benzamide

Water

ECOTOXICOLOGY

Property

Value

Source; quality score; and other information

Interpretation

Bio-concentration factor

BCF (l kg⁻¹)

70.5

Whole fish

Low potential

CT₅₀ (days)

0.49

Mammals - Acute oral LD₅₀ (mg kg⁻¹)

> 10000

Rat

Low

Mammals - Short term dietary NOEL

(mg kg⁻¹)

5.6

Rat 2 year

High

(ppm diet)

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

200

Rat Reproductive NOAEL

Moderate

Birds - Acute LD₅₀ (mg kg⁻¹)

> 2000

Colinus virginianus

Low

Birds - Short term dietary (LC₅₀/LD₅₀)

> 937 mg kg bw⁻¹ day⁻¹

Colinus virginianus

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

Anas platyrhynchos NOEL

Moderate

Fish - Acute 96 hour LC₅₀ (mg l⁻¹)

> 0.87

Cyprinodon variegatus

Moderate

Fish - Chronic 21 day NOEC (mg l⁻¹)

0.87

Oncorhynchus mykiss

Moderate

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

> 1.3

Daphnia magna

Moderate

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

0.69

Daphnia magna

Moderate

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)

8.0

Chironomus riparius development

Moderate

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

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

0.011

Lemna gibba

Moderate

Non-target plants

Cocklebur
Seedling emergence, ER₅₀
as g ha⁻¹

625

-
Vegetative vigour, ER₅₀
A5 Sugar beet

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

> 1.4

Raphidocelis subcapitata

Moderate

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

> 1.4

Selenastrum capricornutum

Low

Honeybees (Apis spp.)

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

> 100

Low

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

> 100

Low

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)

> 500

Eisenia foetida corr

Moderate

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

3.34

Eisenia foetida corr

Moderate

Other soil macro-organisms

Acute LC₅₀ (mg kg⁻¹)

Chronic NOEC (mg kg⁻¹)

Other arthropod (1)

LR₅₀ g ha⁻¹

1000

48 hour
Aphidius rhopalosiphi

% Effect

Other arthropod (2)

LR₅₀ g ha⁻¹

1000

7 day
Typhlodromus pyri

% Effect

Soil micro-organisms

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

Dose: 6.97 mg kg⁻¹ soil 28 days

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)

> 10000

Rat

Low

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

2000

Rat

Mammals - Inhalation LC₅₀ (mg l⁻¹)

2.68

Rat 4 hr (nose only)

Other Mammal toxicity endpoints

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

0.05

SF=100

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

None allocated

Dog SF=100

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

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

0.25

Dog SF = 435

Dermal penetration studies (%)

6.6-16.7

concentration dependent

Dangerous Substances Directive 76/464

Exposure Routes

Public

Negligible risk to bystanders
Dietary exposure considered to be low risk

Occupational

Risk of exposure acceptable under label recommendations for use for personal protection clothing and equipment

MRLs

European

EU MRL pesticide database

Notes

Drinking Water Standards

Drinking Water MAC (μg l⁻¹)

0.1

EU Dir 89/778/EC limit

Health issues

Specific human health issues

Carcinogen

Genotoxic

Endocrine disruptor

; ; ; ;

No data found

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

Bioaccumulates
Possible liver toxicant
USEPA - some evidence to suggest possible human carcinogen

Handling issues

Property

Value and interpretation

General

Not explosive or oxidising

CLP classification 2013

Environment: H413

EC Risk Classification

N - Dangerous for the environment: R50, R53

EC Safety Classification

S60, S61

WHO Classification

U (Unlikely to present an acute hazard)

UN Number

Waste disposal & packaging

TRANSLATIONS

Language

Name

English

isoxaben

French

isoxaben

German

Isoxaben

Danish

isoxaben

Italian

isoxaben

Spanish

isoxaben

Greek

Polish

izoksaben

Swedish

isoxaben

Hungarian

Dutch

Record last updated:	15/02/2021
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