Metribuzin (Ref: DPX G2504)

Metribuzin (Ref: DPX G2504)	Last updated: 20/05/2025
(Also known as: metribuzine; DIC 1468; AE F055208)

SUMMARY

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; Drainflow: Mobile	Ecotoxicity Moderate alert: Birds acute ecotoxicity: Moderate; Birds chronic ecotoxicity: Moderate; Fish acute ecotoxicity: Moderate; Fish chronic ecotoxicity: Moderate; Daphnia acute ecotoxicity: Moderate; Daphnia chronic ecotoxicity: Moderate; Bees acute oral ecotoxicity: Moderate; Earthworms acute ecotoxicity: Moderate; Earthworms chronic ecotoxicity: Moderate	Human health High alert: Mammals chronic toxicity: High; Endocrine disrupter; Reproduction/development effects

GENERAL INFORMATION

Description

A pre- and post-emergence herbicide used to control weeds in cereals and a range of other crops

Example pests controlled

Grasses; Broadleaved weeds

Example applications

Soybeans; Potatoes; Barley, Wheat; Asparagus; Sugarcane; Tomatoes; Peas; Lentils

Efficacy & activity

Efficiacy demonstrated through extensive use and field trials

Availability status

Current

Introduction & key dates

1968, first reported; 1971, first marketed

GB regulatory status

GB COPR regulatory status

Approved

Date COPR inclusion expires

31/07/2028

GB LERAP status

Check label - may vary with formulation

EC Regulation 1107/2009 (repealing 91/414)

EC Regulation 1107/2009 status

Not approved

Dossier rapporteur/co-rapporteur

Estonia/Germany

Date EC 1107/2009 inclusion expires

Expired

EU Candidate for substitution (CfS)

Yes - two 'Persistent-Bioaccumulative-Toxic' criteria

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

C₈H₁₄N₄OS

Canonical SMILES

CC(C)(C)C1=NN=C(N(C1=O)N)SC

Isomeric SMILES

No data

International Chemical Identifier key (InChIKey)

FOXFZRUHNHCZPX-UHFFFAOYSA-N

International Chemical Identifier (InChI)

InChI=1S/C8H14N4OS/c1-8(2,3)5-6(13)12(9)7(14-4)11-10-5/h9H2,1-4H3

2D structure diagram/image available?

Yes

Cambridge Crystallographic Data Centre diagrams

Common Name	Relationship	Link
metribuzin	-

General status

Pesticide type

Herbicide

Substance groups

Triazinone herbicide

Minimum active substance purity

930 g kg⁻¹

Known relevant impurities

EU dossier - None declared

Substance origin

Synthetic

Mode of action

Selective, systemic with contact and residual activity. Inhibits photosynthesis (photosystem II).

CAS RN

21087-64-9

EC number

244-209-7

CIPAC number

283

US EPA chemical code

101101

PubChem CID

30479

CLP index number

606-034-00-8

Molecular mass

214.29

PIN (Preferred Identification Name)

IUPAC name

4-amino-6-tert-butyl-4,5-dihydro-3-methylthio-1,2,4-triazin-5-one

CAS name

4-amino-6-(1,1-dimethylethyl)-3-(methylthio)-1,2,4-triazin-5(4H)-one

Other status information

Potential groundwater contaminant

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

Amaranthus hybridus

Physical state

White crystalline solid

Formulations

Property

Value

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

AgriGuard
Bayer CropScience
DuPont
Greencrop
Makhteshim-Agan
NACL Industries Limited

Example products using this active

Artist
Lexone 2
Sencorex WG
Shotput
Sencor

Formulation and application details

Often supplied as wettable powders, liquid suspensions or water-dispersible granules

ENVIRONMENTAL FATE

Property

Value

Source; quality score; and other information

Interpretation

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

10700

High

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

820

n-Heptane

60000

Xylene

250000

Ethyl acetate

449400

Acetone

Melting point (°C)

125.3

Boiling point (°C)

Decomposes before boiling

Degradation point (°C)

230

Flashpoint (°C)

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

5.01 X 10⁰¹

Calculated

Log P

1.7

Low

Fat solubility of residues

Solubility

Insoluble

Data type

Regulatory data

Density (g ml⁻¹)

1.26

Dissociation constant pKa) at 25 °C

1.3

Strong acid, pKa(2) = 12.8

Vapour pressure at 20 °C (mPa)

0.121

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)

1.71E05

Volatile

Volatilisation as max % of applied dose lost

From plant surface

From soil surface

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

294nm = 8175 (mean)

Surface tension (mN m⁻¹)

63.1

at 20°C

Degradation

Property

Value

Source; quality score; and other information

Interpretation

General biodegradability

Not readily biodegradable

Soil degradation (days) (aerobic)

DT₅₀ (typical)

7.03

Non-persistent

DT₅₀ (lab at 20 °C)

7.03

Non-persistent

DT₅₀ (field)

Non-persistent

DT₉₀ (lab at 20 °C)

24.0

Non-persistent

DT₉₀ (field)

DT₅₀ modelling endpoint

7.1

geometric mean of normalised values

Note

EU 2019 dossier DT₅₀ (normalised) lab studies range 5.98-7.76 days, DT₉₀ range 20.68-25.8 days, Soils=4

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

0.2

Fast

Note

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

Value

Stable

Note

Stable pH 4 to pH 9 at 25 °C over 34 days. Stable pH 4 and pH 7 at 50 °C, some hydrolysis at pH 9 and 50 °C but slow

Water-sediment DT₅₀ (days)

Moderately fast

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)

K_oc (mL g⁻¹)

Notes and range

Freundlich

K_f (mL g⁻¹)

0.874

Mobile

K_foc (mL g⁻¹)

48.3

¹/_n

0.922

Notes and range

EU 2019 dossier kf range 0.303-1.9 mL g⁻¹, K_foc range 26.8-81.5 mL g⁻¹, ¹/_n 0.89-0.95, Soils=6

pH sensitivity

Fate indices

Property

Value

Source; quality score; and other information

Interpretation

GUS leaching potential index

2.96

Calculated

High leachability

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

Value

1.99 X 10^-01

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

21.0

Calculated using the Atkinson method. Assumed 0.5E+06 OH/cm³, 24 hr

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

4-amino-6-tert-butyl-1,2,4-triazine-3,5(2H,4H)-dione (Ref: BCS-AG59919; DK-metribuzin)

Major fraction

0.136

Bayer verified

1,2,4-triazine-3,5(2H,4H)-dione, 6-(1,1-dimethylethyl)- (Ref: BCS-AA68848; DADK-metribuzin)

Major fraction

0.139

Bayer verified

desamino-metribuzin (Ref: BCS-AA91084)

Minor fraction

0.075

Bayer verified

6-tert-butyl-4-methyl-1,2,4-triazine-3,5(2H,4H)-dione (Ref: BCS-AA10228; 4-methyl-DADK-metribuzin)

Minor fraction

0.051

Bayer verified

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)

1,2,4-triazine-3,5(2H,4H)-dione, 6-(1,1-dimethylethyl)- (Ref: BCS-AA68848)

Not relevant

0.013

desamino-metribuzin (Ref: BCS-AA91084)

Not relevant

0.013

4-amino-6-tert-butyl-1,2,4-triazine-3,5(2H,4H)-dione (Ref: BCS-AG59919; DK-metribuzin)

Not relevant

0.013

6-tert-butyl-4-methyl-1,2,4-triazine-3,5(2H,4H)-dione (Ref: BCS-AA10228; 4-methyl-DADK-metribuzin)

Not relevant

0.013

Other known metabolites

Metabolite name and reference

Aliases

Formation medium / Rate

Estimated maximum occurrence fraction

6-(1-hidroxy-1-methyl-ethyl)-3-methylsulfanyl-4H-[1,2,4]-triazine-5-one

t-BuOH-desamino-metribuzin; metribuzin metabolite M05

Rat

ECOTOXICOLOGY

Terrestrial ecotoxicology

Property

Value

Source; quality score; and other information

Interpretation

Mammals - Acute oral LD₅₀ (mg kg⁻¹)

322

Rat

Moderate

Mammals - Short term dietary NOEL

(mg kg⁻¹)

2.2

Rat

High

(ppm diet)

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

3.3

Rat Reproductive NOAEL

High

Birds - Acute LD₅₀ (mg kg⁻¹)

164

Colinus virginianus

Moderate

Birds - Short term dietary (LC₅₀/LD₅₀)

> 359 mg kg bw⁻¹ day⁻¹

Colinus virginianus

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

Colinus virginianus NOAEL

Moderate

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

427

Eisenia foetida

Moderate

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

> 52.3

Eisenia foetida 56 day

Moderate

Soil micro-organisms

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

Dose: Not stated 28 Day

Collembola

Acute LC₅₀ (mg kg⁻¹)

Chronic NOEC (mg kg⁻¹)

15.95

Folsomia candida

Non-target plants

15.7

Brassica napus
Seedling emergence, ER₅₀
as g ha⁻¹

12.3

Brassica napus
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)

> 100

Apis mellifera

Low

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

> 76.7

Apis mellifera

Moderate

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

Chronic as 10-day LC₅₀ mg bee⁻¹ day⁻¹

619.52

Apis mellifera

Notes

Bumblebees (Bombus spp.)

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

> 100

Bombus terrestris

Low

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

> 140

Bombus terrestris

Low

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) as Mortality LR₅₀ g ha⁻¹

947

Coccinella septempunctata

Beneficial insects (Lacewings) as Mortality LR₅₀ g ha⁻¹

> 1050

Chrysoperla carnea

Beneficial insects (Parasitic wasps) as Mortality LR₅₀ g ha⁻¹ 48 hr

34.1

Aphidius rhopalosiphi

Beneficial insects (Predatory mites) as Mortality LR₅₀ g ha⁻¹ 7 day

40.1

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)

74.6

Oncorhynchus mykiss

Moderate

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

5.6

Oncorhynchus mykiss growth

Moderate

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

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

Daphnia magna

Moderate

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

0.305

Daphnia magna

Moderate

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

> 25

Ceriodaphnia dubia LC₅₀

Moderate

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

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

> 43.2

Chironomus riparius 24 hr EC₅₀

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)

0.0161

Lemna gibba

Moderate

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

0.18

Myriophyllum spicatum 14d NOEC

Moderate

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

0.0266

Desmodesmus subspicatus

Moderate

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

0.019

Unknown species

Moderate

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)

322

Rat

Moderate

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

5000

Rat

Mammals - Inhalation LC₅₀ (mg l⁻¹)

2.05

Rat 4 hr (dust nose only)

Other Mammal toxicity endpoints

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

0.013

Rat SF=100

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

0.02

SF=100

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

No data

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

0.02

SF=100

Dermal penetration studies (%)

0.3-20.0

concentration dependent

Dangerous Substances Directive 76/464

Exposure Routes

Public

No unacceptable risks to bystanders identified

Occupational

Minimal risk for operators using protection clothing and equipment

MRLs

European

EU MRL pesticide database

Great Britain

GB MRL Register

Notes

Drinking Water Standards

Drinking Water MAC (μg l⁻¹)

Mammalian dose elimination route and rate

It is rapidly distributed in the body and excreted via the urine and 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

Endocrine issues - Hyperthyroidism, alteration of somatotropin levels
Thyroid toxicant

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: H302, H373
Environment: H400, H410

WHO Classification

II (Moderately hazardous)

UN Number

UN3077

Waste disposal & packaging

Packaging Group III (minor danger)

Shelf-life, storage, stability and reactivity

Limited shelf-life

TRANSLATIONS

Language

Name

English

metribuzin

French

metribuzine

German

Metribuzin

Danish

metribuzin

Italian

metribuzin

Spanish

metribuzina

Greek

metribuzin

Polish

metrybuzyna

Swedish

metribuzin

Hungarian

metribuzin

Dutch

metribuzine

Norwegian

Record last updated:	20/05/2025
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