Bentazone

Bentazone	Last updated: 04/06/2025
(Also known as: bendioxide; bentazon)

SUMMARY

Bentazone is a herbicide used to control annual weeds. It is highly soluble in water, volatile and, as it is mobile, may present a risk of leaching to groundwater. It is not likely to be persistent in soil systems but may be persistent in water under certain conditions. It is moderately toxic to humans and a recognised skin and eye irritant. Bentazone is also moderately toxic to birds, fish, aquatic invertebrates 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 High alert: Drainflow: Mobile	Ecotoxicity Moderate alert: Birds acute ecotoxicity: Moderate; Birds chronic ecotoxicity: Moderate	Human health Moderate alert: Mammals acute toxicity: Moderate; Mammals chronic toxicity: Moderate

GENERAL INFORMATION

Description

A post-emergence contact diazinone herbicide used to control annual weeds in a variety of crops

Example pests controlled

Black bindweed; Nightshade; Fat hen; Hedge mustard; Shepherd's purse; Wild radish; Wild turnip; Bellvine; Starburr; Anoda weed

Example applications

Corn; Rice; Alfalfa; Sorghum; Linseed; Peanuts; Beans; Peas; Clover; Chives; Garlic; Ornamentals e.g. begonia; Soybeans; Turf

Efficacy & activity

Availability status

Current

Introduction & key dates

1972, first introduced

GB regulatory status

GB COPR regulatory status

Approved

Date COPR inclusion expires

31/05/2031

GB LERAP status

None

EC Regulation 1107/2009 (repealing 91/414)

EC Regulation 1107/2009 status

Approved

Dossier rapporteur/co-rapporteur

Netherlands/Germany

Date EC 1107/2009 inclusion expires

31/10/2027

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; Egypt; Morocco

Chemical structure

Isomerism

None

Chemical formula

C₁₀H₁₂N₂O₃S

Canonical SMILES

CC(C)N1C(=O)C2=CC=CC=C2NS1(=O)=O

Isomeric SMILES

No data

International Chemical Identifier key (InChIKey)

ZOMSMJKLGFBRBS-UHFFFAOYSA-N

International Chemical Identifier (InChI)

InChI=1S/C10H12N2O3S/c1-7(2)12-10(13)8-5-3-4-6-9(8)11-16(12,14)15/h3-7,11H,1-2H3

2D structure diagram/image available?

Yes

General status

Pesticide type

Herbicide

Substance groups

Benzothiazinone herbicide

Minimum active substance purity

960 g kg⁻¹

Known relevant impurities

EU dossier: 1,2-dichloroethane <3.0 mg kg⁻¹

Substance origin

Synthetic

Mode of action

Selective action, absorbed by foliage with very little translocation. Inhibits photosynthesis (photosystem II).

CAS RN

25057-89-0

EC number

246-585-8

CIPAC number

366

US EPA chemical code

275200

PubChem CID

2328

CLP index number

613-012-00-1

Molecular mass

240.3

PIN (Preferred Identification Name)

3-(propan-2-yl)-1H-2?6,1,3-benzothiadiazine-2,2,4(3H)-trione

IUPAC name

3-isopropyl-1H-2,1,3-benzothiadiazin-4(3H)-one 2,2-dioxide

CAS name

3-(1-methylethyl)-1H-2,1,3-benzothiadiazin-4(3H)-one 2,2-dioxide

Other status information

Potential groundwater contaminant

Relevant Environmental Water Quality Standards

UK Environment Agency statutory standard for the protection of surface water quality and aquatic life: annual mean classification of inland waters, coastal waters & relevant territorial waters: 500 µg l⁻¹

Herbicide Resistance Class (HRAC MoA class)

Herbicide Resistance Class (WSSA MoA class)

Insecticide Resistance Class (IRAC MoA class)

Not applicable

Fungicide Resistance Class (FRAC MOA class)

Not applicable

Examples of recorded resistance

Physical state

White to yellow coloured crystals depending upon purity

Related substances & organisms

bentazone-sodium

Formulations

Property

Value

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

AgriGuard
BASF
Goldengrass
BOC Sciences

Example products using this active

Basagran
Zone 48
Troy 480
Herbatox
Leader
Laddox
Sharda Bentazon

Formulation and application details

Usually formulated as a soluble concentrate or granules, 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)

7112

High

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

18.0

n-Heptane

21000

Toluene

388000

Ethyl acetate

556000

Methanol

Melting point (°C)

139

Boiling point (°C)

Decomposes before boiling

Degradation point (°C)

210

Flashpoint (°C)

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

3.47 X 10^-01

Calculated

Log P

-0.46

Low

Fat solubility of residues

Solubility

Possible

Data type

Higher than expected fat observed in metabolism and farm animal feeding studies. More research pending.

Density (g ml⁻¹)

1.41

Dissociation constant pKa) at 25 °C

3.51

Weak acid; pKa(2)=2.50

Vapour pressure at 20 °C (mPa)

0.17

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)

7.20 X 10^-05

Non-volatile

Volatilisation as max % of applied dose lost

From plant surface

From soil surface

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

pH 4.4: 225nm=30854; 335nm=2987.8

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)

7.5

Non-persistent

DT₉₀ (lab at 20 °C)

91.2

Moderately persistent

DT₉₀ (field)

31.9

DT₅₀ modelling endpoint

Note

EU dossier Lab studies DT₅₀ range 8-35.0 days, DT₉₀ range 32-149.8 days, Soils=12; field study DT₅₀ range 3.0-31.3 days, DT₉₀ range 12.9-87.7 days, Soils=8

Dissipation rate RL₅₀ (days) on plant matrix

Value

Note

Dissipation rate RL₅₀ (days) on and in plant matrix

Value

1.5

Note

Wheat, whole plant, n=1

Aqueous photolysis DT₅₀ (days) at pH 7

Value

Moderately fast

Note

DT₅₀ 122 hours at pH 5, 14 hours at pH 9

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

Value

Stable

Note

Stable pH 5 to pH 9

Water-sediment DT₅₀ (days)

716

Stable

Water phase only DT₅₀ (days)

Stable

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)

0.72

Mobile

K_oc (mL g⁻¹)

55.3

Notes and range

EU dossier K_d range 0.22-2.99 mL g⁻¹; K_oc range 13-176 mL g⁻¹, Soils=7

Freundlich

K_f (mL g⁻¹)

0.97

Mobile

K_foc (mL g⁻¹)

59.6

¹/_n

0.93

Notes and range

EU 2015 dossier K_f range 0.02-3.06 mL g⁻¹, K_foc range 3.0-158.0 mL g⁻¹, ¹/_n range 0.7-1.03, Soils=25; Literature data: K_f range 1.2-1.9 mL g⁻¹, kfoc range 37-238 mL g⁻¹, ¹/_n range 1.00-1.01, Soils = 13

pH sensitivity

Fate indices

Property

Value

Source; quality score; and other information

Interpretation

GUS leaching potential index

1.95

Calculated

Transition state

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

Value

1.74 X 10^-02

Calculated

Note

Potential for particle bound transport index

Low

Calculated

Potential for loss via drain flow

Mobile

Calculated

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

2.1

Calculated using the Atkinson method.

Below the level of concern for long-range air transport

Bio-concentration factor

BCF (l kg⁻¹)

Low potential

CT₅₀ (days)

Not available

Known soil metabolites

Metabolite

Major/Minor fraction

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

Estimated maximum occurrence fraction

Notes

2-amino-N-isopropylbenzamide

Minor fraction

N-methyl bentazone

Minor fraction

0.057

Known groundwater metabolites

Metabolite

EC SANCO/221/2000 relevancy

ADI (mg kg⁻¹ bodyweight day⁻¹)

WHO drinking water guidance value (μg L⁻¹ day⁻¹)

N-methyl bentazone

Relevancy unknown

Other known metabolites

Metabolite name and reference

Aliases

Formation medium / Rate

Estimated maximum occurrence fraction

8-hydroxy-bentazone

Plant; Animal; Surface water; Sediment

6-hydroxy bentazone

Plant; Animal

N-methyl bentazone

Surface water; Sediment

3-isopropyl-4,5-dioxo-1,3,4,5,6,7-hexahydrocyclopenta[c][1,2,6]thiadiazine-6-carboxylic acid 2,2-dioxide, salts (Ref: M351H023)

Surface water

[2-(isopropylcarbamoyl)phenyl]sulfamic acid, salts (Ref: M351H024)

Surface water

ECOTOXICOLOGY

Terrestrial ecotoxicology

Property

Value

Source; quality score; and other information

Interpretation

Mammals - Acute oral LD₅₀ (mg kg⁻¹)

1400

Rat

Moderate

Mammals - Short term dietary NOEL

(mg kg⁻¹)

Rat

High

(ppm diet)

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

164.3

Rat Reproductive NOAEL

Moderate

Birds - Acute LD₅₀ (mg kg⁻¹)

1140

Colinus virginianus

Moderate

Birds - Short term dietary (LC₅₀/LD₅₀)

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

Anas platyrhynchos

Moderate

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

> 1000

Eisenia foetida

Low

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

Soil micro-organisms

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

Dose: 9.6 kg ha⁻¹

Collembola

Acute LC₅₀ (mg kg⁻¹)

Chronic NOEC (mg kg⁻¹)

Non-target plants

> 95.0

Sinapis alba
Seedling emergence, ER₅₀
as g ha⁻¹

95.0

Sinapis alba
Vegetative vigour, ER₅₀
as g ha⁻¹

Honeybees (Apis spp.)

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

> 200

Apis mellifera

Low

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

> 200

Apis mellifera

Low

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

Chronic

Notes

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)

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)

Beneficial insects (Lacewings)

7.0% Mortality at dose 1.44 kg ha⁻¹

Chrysoperla carnea Instar

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

699

Aphidius rhopalosiphi

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

2795

Typhlodromus pyri

Beneficial insects (Ground beetles)

3.4% Mortality at dose 9.6 kg ha⁻¹

Poecilus cupress Adult

Aquatic ecotoxicology

Property

Value

Source; quality score; and other information

Interpretation

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

> 100

Oncorhynchus mykiss

Low

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

Oncorhynchus mykiss

Low

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

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

> 100

Daphnia magna

Low

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

> 101

Daphnia magna

Low

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

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

132.5

Americamysis bahia

Low

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

62.31

Chironomus riparius

Moderate

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)

5.4

Lemna gibba

Moderate

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

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

10.1

Anabaena flos-aquae 120 hr

Low

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

25.7

Unknown species

Low

Mesocosm study data

NOEAEC mg l⁻¹

Marine bivalves – NOEL (mg l⁻¹)

0.046

Crassostrea gigas

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)

1400

Rat

Moderate

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

5000

Rat

Mammals - Inhalation LC₅₀ (mg l⁻¹)

> 5.1

Rat 4 hr (head-nose only)

Other Mammal toxicity endpoints

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

0.09

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

1.0

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

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

0.13

Dog 1 year SF=100

Dermal penetration studies (%)

0.2-0.9

concentration dependent

Dangerous Substances Directive 76/464

List II

Exposure Routes

Public

Minimal risk of dietary exposure
No unacceptable risks to bystanders identified

Occupational

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

MRLs

European

EU MRL pesticide database

Great Britain

GB MRL Register

Notes

Changes to GB MRL implemented April 2024

Drinking Water Standards

Drinking Water MAC (μg l⁻¹)

Mammalian dose elimination route and rate

Almost entirely excreted in the urine.

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

Possible blood, liver, kidney toxicant

Handling issues

Property

Value and interpretation

General

Not oxidising or explosive
Not expected to auto-ignite; Not highly flammable
IMDG Transport Hazard Class 3

CLP classification 2013

Health: H302, H317, H319
Environment: H412

WHO Classification

II (Moderately hazardous)

UN Number

UN1648

Waste disposal & packaging

Packaging Group II (moderate danger)

Shelf-life, storage, stability and reactivity

Stability may be affectd by light. Limited shelf-life.

TRANSLATIONS

Language

Name

English

bentazone

French

bentazone

German

Bentazon

Danish

bentazon

Italian

bentazone

Spanish

bentazona

Greek

bentazone

Polish

bentazon

Swedish

bentazon

Hungarian

bentazone

Dutch

bentazon

Norwegian

bentazon

Record last updated:	04/06/2025
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