Topramezone (Ref: BAS 670 H)

Topramezone (Ref: BAS 670 H)	Last updated: 27/06/2025
(Also known as: benzuocaotong)

SUMMARY

Topramezone is a post-emergence herbicide. It is highly soluble in water, non-volatile but, based on its chemical properties, has a high risk of leaching to groundwater. It can be persistent in both soil and aquatic systems. It is moderately toxic to mammals but a low potential for bioaccumulation. It is classified as an irritant. It is moderately toxic to birds, honeybees, earthworms, fish and aquatic invertebrates.

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: GUS: High leachability	Ecotoxicity Moderate alert: Fish chronic ecotoxicity: Moderate; Bees acute oral ecotoxicity: Moderate; Earthworms chronic ecotoxicity: Moderate	Human health High alert: Reproduction/development effects

GENERAL INFORMATION

Description

A post-emergence herbicide for broadleaved weeds and grasses used mainly on corn

Example pests controlled

Giant foxtail; Broadleaved signal grass; Crabgrass; Goosegrass; Woolly cupgrass; Shattercane; Johnsongrass; Barnyardgrass

Example applications

Field corn (grain, silage, seed); Sweetcorn; Popcorn

Efficacy & activity

Availability status

Current

Introduction & key dates

2006, 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

France

Date EC 1107/2009 inclusion expires

Not applicable

EU Candidate for substitution (CfS)

No data

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

Morocco

Chemical structure

Isomerism

None

Chemical formula

C₁₆H₁₇N₃O₅S

Canonical SMILES

CC1=C(C=CC(=C1C2=NOCC2)S(=O)(=O)C)C(=O)C3=CNN(C3=O)C

Isomeric SMILES

No data

International Chemical Identifier key (InChIKey)

IYMLUHWAJFXAQP-UHFFFAOYSA-N

International Chemical Identifier (InChI)

InChI=1S/C16H17N3O5S/c1-9-10(15(20)11-8-17-19(2)16(11)21)4-5-13(25(3,22)23)14(9)12-6-7-24-18-12/h4-5,8,21H,6-7H2,1-3H3

2D structure diagram/image available?

Yes

General status

Pesticide type

Herbicide

Substance groups

Benzoylpyrazole herbicide; Pyrazole herbicide; Oxazole herbicide

Minimum active substance purity

970 g kg⁻¹

Known relevant impurities

EU dossier - None declared

Substance origin

Synthetic

Mode of action

Systemic, highly selective, rapidly absorbed and translocated. Bleaching: inhibition of 4-hydroxyphenyl-pyruvate-dioxygenase.

CAS RN

210631-68-8

EC number

606-699-4

CIPAC number

800

US EPA chemical code

123009

PubChem CID

11302979

CLP index number

No data found

Molecular mass

363.39

PIN (Preferred Identification Name)

[3-(4,5-dihydro-1,2-oxazol-3-yl)-4-(methanesulfonyl)-2-methylphenyl](5-hydroxy-1-methyl-1H-pyrazol-4-yl)methanone

IUPAC name

[3-(4,5-dihydro-1,2-oxazol-3-yl)-4-mesyl-o-tolyl](5-hydroxy-1-methylpyrazol-4-yl)methanone

CAS name

[3-(4,5-dihydro-3-isoxazolyl)-2-methyl-4-(methylsulfonyl)phenyl](5-hydroxy-1-methyl-1H-pyrazol-4-yl)methanone

Other status information

PAN Bad Actor Chemical

Relevant Environmental Water Quality Standards

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 crystalline solid

Formulations

Property

Value

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

Avmac
BASF
Bayer CropScience
Nippon Soda

Example products using this active

Pylex
BAS 670 00H
Armezon
Alphard

Formulation and application details

Formulations include suspension concentrates

ENVIRONMENTAL FATE

Property

Value

Source; quality score; and other information

Interpretation

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

100000

High

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

10000

Acetone

10000

Toluene

10000

n-Heptane

10000

Ethyl acetate

Melting point (°C)

220.9

Boiling point (°C)

Degradation point (°C)

300

Flashpoint (°C)

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

3.02 X 10^-02

Calculated

Log P

-1.52

Low

Fat solubility of residues

Solubility

Insoluble

Data type

Regulatory data

Density (g ml⁻¹)

1.406

Dissociation constant pKa) at 25 °C

4.06

Weak acid

Vapour pressure at 20 °C (mPa)

1.10 X 10^-09

Low volatility

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

7.13 X 10^-14

Non-volatile

Volatilisation as max % of applied dose lost

From plant surface

1.5

24 hr

Volatilisation is not considered critical for air pollution

From soil surface

24 hr

Volatilisation is not considered critical for air pollution

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

207nm = 27077, 272nm = 8601, 300nm = 5800, 410nm = 96

Surface tension (mN m⁻¹)

69.0

at 20°C 1% soln

Degradation

Property

Value

Source; quality score; and other information

Interpretation

General biodegradability

Soil degradation (days) (aerobic)

DT₅₀ (typical)

218

Persistent

DT₅₀ (lab at 20 °C)

218

Persistent

DT₅₀ (field)

26.1

Non-persistent

DT₉₀ (lab at 20 °C)

763

Very persistent

DT₉₀ (field)

529

DT₅₀ modelling endpoint

Note

EU dossier lab studies DT₅₀ range 85-357 days, DT₉₀ range 283-greater than 1000 days; field studies DT₅₀ range 10.8-69.3 days, DT₉₀ range 184-greater than 1000 days. Other studies: Lab DT₅₀ range 125-495 days, field studies range 3-29 days

Dissipation rate RL₅₀ (days) on plant matrix

Value

Note

Dissipation rate RL₅₀ (days) on and in plant matrix

Value

Note

Aqueous photolysis DT₅₀ (days) at pH 7

Value

Stable

Note

Data for sterile buffer solution at pH 5 and pH9, slow degradation in natural water DT₅₀ 72 days continuous irradiation

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

Value

Stable

Note

Stable pH 5 to pH 9at 25 °C, 30 days

Water-sediment DT₅₀ (days)

77.5

Moderately fast

Water phase only DT₅₀ (days)

9.5

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

Soil adsorption and mobility

Property

Value

Source; quality score; and other information

Interpretation

Linear

K_d (mL g⁻¹)

Moderately mobile

K_oc (mL g⁻¹)

171

Notes and range

Canadian dossier gives K_oc range 38-303 mL g⁻¹

Freundlich

K_f (mL g⁻¹)

1.78

Moderately mobile

K_foc (mL g⁻¹)

¹/_n

0.86

Notes and range

EU dossier K_f range 0.165-6.33, K_foc range 15.0-296.7 mL g⁻¹, ¹/_n range 0.786-0.923

pH sensitivity

Adsorption stronger on more acidic soils

Fate indices

Property

Value

Source; quality score; and other information

Interpretation

GUS leaching potential index

2.88

Calculated

High leachability

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

Value

2.15 X 10^-01

Calculated

Note

Potential for particle bound transport index

Low

Calculated

Potential for loss via drain flow

Moderately mobile

Calculated

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

25.6

Calculated using the Atkinson method. Assumed 0.8E+06 OH/cm³, 12 hr

Below the level of concern for long-range air transport

Bio-concentration factor

BCF (l kg⁻¹)

0.3

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

6-(5-hydroxy-1-methyl-1H-pyrazol-4-yl)carbonyl)-5-methyl-2,3-dihydro-4H-1-benzothiopyran-4-one (Ref: M670H10)

Minor fraction

3-(4,5-dihydro-isoxazol-3-yl)-4-methanesulfonyl-2-methyl-benzoic acid (Ref: M670H05)

Major fraction

0.192

(3-cyano-4-methanesulfonyl-2-methyl phenyl)(5-hydroxy-1-methyl-1H-pyrazol-4-yl)methanone (Ref: M670H01)

Minor fraction

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)

3-(4,5-dihydro-isoxazol-3-yl)-4-methanesulfonyl-2-methyl-benzoic acid (Ref: M670H05)

Relevant

Other known metabolites

Metabolite name and reference

Aliases

Formation medium / Rate

Estimated maximum occurrence fraction

Ref: M670H03

topramezone des-N-methyl

Plant

Ref: M670H08

topramezone methyl ketone

Plant

Ref: M670H04

demethyl hydroxy topramezone

Animal

Ref: M670H02

hydroxy topramezone

Plant; Animal

ECOTOXICOLOGY

Terrestrial ecotoxicology

Property

Value

Source; quality score; and other information

Interpretation

Mammals - Acute oral LD₅₀ (mg kg⁻¹)

> 2000

Rat

Low

Mammals - Short term dietary NOEL

(mg kg⁻¹)

0.5

Rat

High

(ppm diet)

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

Birds - Acute LD₅₀ (mg kg⁻¹)

> 2000

Colinus virginianus

Low

Birds - Short term dietary (LC₅₀/LD₅₀)

> 1085 mg kg bw⁻¹ day⁻¹

Colinus virginianus

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

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

> 1000

Eisenia foetida

Low

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

0.672

Eisenia foetida

Moderate

Soil micro-organisms

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

Dose: 0.67 mg kg⁻¹ soil 28 Day

Collembola

Acute LC₅₀ (mg kg⁻¹)

Chronic NOEC (mg kg⁻¹)

37.2

Folsomia candida

Non-target plants

46.1

Onion
Seedling emergence, ER₅₀
as mL product ha⁻¹ (BASS 670 00 Conc 336 g l⁻¹)

Buckwheat
Vegetative vigour, ER70
as mL product ha⁻¹ (BASS 670 00 Conc 336 g l⁻¹)

Honeybees (Apis spp.)

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

> 100

Apis mellifera

Low

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

> 72.05

Apis mellifera

Moderate

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)

4.4% Mortality at dose 74 g ha⁻¹

Chrysoperla carnea

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

> 100

Aphidius rhopalosiphi Adult

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

105

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)

> 100

Oncorhynchus mykiss

Low

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

0.01

Oncorhynchus mykiss

Moderate

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)

97.5

Daphnia magna

Low

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)

0.009

Lemna gibba

High

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

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

17.2

Pseudokirchneriella subcapitata

Low

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

Pseudokirchneriella subcapitata

Low

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)

> 2000

Rat

Low

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

2000

Rat

Mammals - Inhalation LC₅₀ (mg l⁻¹)

> 5.4

Rat 4 hr (head & nose)

Other Mammal toxicity endpoints

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

0.001

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

0.001

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

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

0.0006

Dermal penetration studies (%)

Dangerous Substances Directive 76/464

Exposure Routes

Public

Negligible risk to bystanders

Occupational

Possible risk on re-entry of sprayed areas

MRLs

European

EU MRL pesticide database

Great Britain

GB MRL Register

Notes

GB MRL expected to deviate from the EU MRL in mid-2023

Drinking Water Standards

Drinking Water MAC (μg l⁻¹)

0.1

EU Dir 89/778/EC limit; Calc MAC=12 µg l⁻¹

Mammalian dose elimination route and rate

Health issues

Specific human health issues

Carcinogen

Genotoxic

Endocrine disruptor

; ; ; ;

No data found

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

Eye, liver, kidney, pancreas, and thyroid toxicant
US EPA - possible human carcinogen at high doses

Handling issues

Property

Value and interpretation

General

Not explosive or oxidising
IMDG Transport Hazard Class 9
Not expected to auto-ignite; Not highly flammable

CLP classification 2013

Health: H360
Environment: H400, H410

WHO Classification

Not listed (Not listed)

UN Number

UN3077

Waste disposal & packaging

Packaging Group III (minor danger)

Shelf-life, storage, stability and reactivity

TRANSLATIONS

Language

Name

English

topramezone

French

German

Topramezone

Danish

topramezone

Italian

topramezone

Spanish

topramezona

Greek

Polish

topramezone

Swedish

Hungarian

Dutch

topramezone

Norwegian

Record last updated:	27/06/2025
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