Metamitron (Ref: BAY DRW 1139)

Metamitron (Ref: BAY DRW 1139)	Last updated: 31/10/2024
(Also known as: metamitrone; methiamitron; BAY 134028)

SUMMARY

Metamitron is a widely used herbicide. It is highly soluble in water and is not considered to be highly volatile. It can be moderately persistent in some soil systems depending on local conditions. Metamitron may also be persistent in aquatic systems. Generally, it is quite toxic to most fauna and flora. Metamitron is moderately toxic to mammals if ingested, is an endocrine disruptor and may be a thyroid toxicant.

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: GUS: Transition state; Drainflow: Moderately mobile	Ecotoxicity Moderate alert: Birds acute ecotoxicity: Moderate; Birds chronic 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: Endocrine disrupter

GENERAL INFORMATION

Description

A herbicide effective against grass and broad-leaved weeds in beet crops

Example pests controlled

Grasses; Broad-leaved weeds

Example applications

Sugarbeet; Fodder beet; Mangels; Red beet; Pome fruit

Efficacy & activity

Availability status

Current

Introduction & key dates

1975, first reported

GB regulatory status

GB COPR regulatory status

Approved

Date COPR inclusion expires

31/08/2031

GB LERAP status

None

EC Regulation 1107/2009 (repealing 91/414)

EC Regulation 1107/2009 status

Approved

Dossier rapporteur/co-rapporteur

Denmark/Latvia

Date EC 1107/2009 inclusion expires

30/11/2026

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

USA, Morocco

Chemical structure

Isomerism

None

Chemical formula

C₁₀H₁₀N₄O

Canonical SMILES

CC1=NN=C(C(=O)N1N)C2=CC=CC=C2

Isomeric SMILES

No data

International Chemical Identifier key (InChIKey)

VHCNQEUWZYOAEV-UHFFFAOYSA-N

International Chemical Identifier (InChI)

InChI=1S/C10H10N4O/c1-7-12-13-9(10(15)14(7)11)8-5-3-2-4-6-8/h2-6H,11H2,1H3

2D structure diagram/image available?

Yes

Cambridge Crystallographic Data Centre diagrams

Common Name	Relationship	Link
metamitron	-

General status

Pesticide type

Herbicide

Substance groups

Triazinone herbicide

Minimum active substance purity

980 g kg⁻¹

Known relevant impurities

EU dossier - None declared

Substance origin

Synthetic

Mode of action

Selective, systemic, absorbed mainly by roots and translocated. Inhibits photosynthesis (photosystem II).

CAS RN

41394-05-2

EC number

255-349-3

CIPAC number

381

US EPA chemical code

PubChem CID

38854

CLP index number

613-129-00-8

Molecular mass

202.21

PIN (Preferred Identification Name)

IUPAC name

4-amino-4,5-dihydro-3-methyl-6-phenyl-1,2,4-triazin-5-one

CAS name

4-amino-3-methyl-6-phenyl-1,2,4-triazin-5(4H)-one

Other status information

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

Yellow crystals

Formulations

Property

Value

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

Bayer CropScience
Makhteshim-Agan
Nufarm
Sipcam
White Agrochemicals

Example products using this active

Galahad
Goldbeet
Goltix 90
Goltix Flowable
Goltix Super
Goltix WG
Marquise
MM70
Skater
Goltix gold

Formulation and application details

Available in a variety of formulations including wettable powders and water-dispersible granules

ENVIRONMENTAL FATE

Property

Value

Source; quality score; and other information

Interpretation

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

1770

High

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

37000

Acetone

2000

Xylene

20000

Ethyl acetate

33000

Dichloromethane

Melting point (°C)

166.6

Boiling point (°C)

Degradation point (°C)

250

Flashpoint (°C)

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

7.08 X 10⁰⁰

Calculated

Log P

0.85

Low

Fat solubility of residues

Solubility

Data type

Density (g ml⁻¹)

1.35

Dissociation constant pKa) at 25 °C

Not applicable

No dissociation

Vapour pressure at 20 °C (mPa)

7.44 X 10^-04

Low volatility

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

8.95 X 10^-08

Non-volatile

Volatilisation as max % of applied dose lost

From plant surface

From soil surface

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

311.1nm = 11789

Surface tension (mN m⁻¹)

68.0

at 20°C

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)

Non-persistent

DT₅₀ (field)

11.1

Non-persistent

DT₉₀ (lab at 20 °C)

39.7

Moderately persistent

DT₉₀ (field)

36.8

DT₅₀ modelling endpoint

Note

EU dossier lab studies DT₅₀ range 2.2-44.5 days (normalised), DT₉₀ range 11.3-113.6 days, field studies DT₅₀ range 6.6-11 days, DT₉₀ range 22.0-73 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

0.02

Fast

Note

1.45 hrs river, pH 7 and test conditions, 0.5 hrs pure water, natural summer light, 50 deg N

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

Value

480

Very persistent

Note

pH sensitive: DT₅₀ 353.2 days at pH 5, 8.5 days at pH 9, all at 20 °C

Water-sediment DT₅₀ (days)

11.1

Fast

Water phase only DT₅₀ (days)

10.5

Moderately fast

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)

0.89

Moderately mobile

K_oc (mL g⁻¹)

77.7

Notes and range

EU dossier K_d range 0.193-1.59, K_oc range 22.9-132.5, Soils=4

Freundlich

K_f (mL g⁻¹)

1.09

Moderately mobile

K_foc (mL g⁻¹)

86.4

¹/_n

0.81

Notes and range

EU dossier K_f range 0.36-5.88 mL g⁻¹, K_foc range 22.4-303 mL g⁻¹, 1.n range 0.67-0.95, Soils=17

pH sensitivity

Fate indices

Property

Value

Source; quality score; and other information

Interpretation

GUS leaching potential index

2.16

Calculated

Transition state

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

Value

4.86 X 10^-02

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

19.8

Calculated using the Atkinson method. Assumed 1.5E+06 OH/cm³, 12 hr

Below the level of concern for long-range air transport

Bio-concentration factor

BCF (l kg⁻¹)

Estimated

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

desamino-metamitron

Major fraction

0.171

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)

desamino-metamitron

Not relevant

Other known metabolites

Metabolite name and reference

Aliases

Formation medium / Rate

Estimated maximum occurrence fraction

desamino-metamitron

Surface water; Sediment

4-amino-6-(4-hydroxyphenyl)-3-methyl-1,2,4-triazin-5(4H)-one

metamitron-4-hydroxy

Rat

6-(4-hydroxyphenyl)-3-methyl-1,2,4-triazin-5(4H)-one

metamitron-4-hydroxy-desamino

Rat (Urine, Faeces); Animal

3-methyl-4-amino-6-phenyl-1,2,4-triazine-5-one-oxide

Rat (Urine)

5-(carboxymethyl)-2-methylpyrido[2,1-f][1,2,4]triazin-9-ium-4-olate

metamitron-triazinium acetic acid

Rat (UrIne, Faeces)

6-(3-hydroxyphenyl)-3-methyl-1,2,4-triazin-5(4H)-one

metamitron-3-hydroxy-desamino

Rat (Urine, Faeces)

N-beta-D-glucosyl-4-amino-3-methyl-6-phenyl-1,2,4-triazin-5(4H)-one

metamitron-N-glucoside

Plant

(2Z)-(hydroxyimino)(phenyl)ethanoic acid

oxime-acid

Plant

N'-acetylbenzohydrazide

N-acetylbenzoic acid hydrazide

ECOTOXICOLOGY

Terrestrial ecotoxicology

Property

Value

Source; quality score; and other information

Interpretation

Mammals - Acute oral LD₅₀ (mg kg⁻¹)

1183

Rat

Moderate

Mammals - Short term dietary NOEL

(mg kg⁻¹)

> 56

Rat 2 yr

High

(ppm diet)

> 250

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

97.2

Rat Reproductive NOAEL

Moderate

Birds - Acute LD₅₀ (mg kg⁻¹)

1302

Coturnix japonica

Moderate

Birds - Short term dietary (LC₅₀/LD₅₀)

> 904 mg kg bw⁻¹ day⁻¹

Colinus virginianus

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

81.5

Colinus virginianus NOAEL

Moderate

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

914

Eisenia foetida

Moderate

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

28.0

Eisenia foetida

Moderate

Soil micro-organisms

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

Dose: 19.5 mg kg⁻¹ soil 28 Day

Collembola

Acute LC₅₀ (mg kg⁻¹)

Chronic NOEC (mg kg⁻¹)

22.4

Folsomia candida

Non-target plants

54.9

Rape
Seedling emergence, 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)

> 97.2

Apis mellifera

Moderate

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

Chronic as 10-day LDD₅₀ µg bee⁻¹ day⁻¹

> 49.25

Apis mellifera

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)

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

>= 14383

Aphidius rhopalosiphi

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

>= 14383

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)

>= 190

Oncorhynchus mykiss

Low

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

7.0

Oncorhynchus mykiss

Moderate

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

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

5.7

Daphnia magna

Moderate

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

Daphnia magna

Moderate

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 - Acute 7 day EC₅₀, biomass (mg l⁻¹)

0.4

Lemna minor

Moderate

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

0.4

Pseudokirchneriella subcapitata

Moderate

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

0.1

Unknown species

Moderate

Mesocosm study data

NOEAEC mg l⁻¹

1.12

Aquatic community

NOEAEC mg l⁻¹

Marine bivalves – Acute EC₅₀ development (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)

1183

Rat

Moderate

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

5000

Rat

Mammals - Inhalation LC₅₀ (mg l⁻¹)

3.17

Rat 4 hr (nose only)

Other Mammal toxicity endpoints

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

0.03

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

0.1

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

0.013

Dog SF=100

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

0.036

Dermal penetration studies (%)

10.0

Dangerous Substances Directive 76/464

Exposure Routes

Public

Occupational

Potenial risk to operators and other workers - PPC/PPE essential

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

Health issues

Specific human health issues

Carcinogen

Genotoxic

Endocrine disruptor

; ; ; ;

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

Harmful by inhalation and ingestion
Possible thyroid toxicant - increased incidence in male thyroid ollicular adenomas at a high dose

Handling issues

Property

Value and interpretation

General

Prevent generation of dust
Not explosive or oxidising
IMDG Transport Hazard Class 6.1
Not expected to auto-ignite; Not highly flammable

CLP classification 2013

Health: H302
Environment: H400

WHO Classification

II (Moderately hazardous)

UN Number

UN2811

Waste disposal & packaging

Packaging Group II (moderate danger)

Shelf-life, storage, stability and reactivity

TRANSLATIONS

Language

Name

English

metamitron

French

metamitrone

German

Metamitron

Danish

metamitron

Italian

metamitron

Spanish

metamitrona

Greek

metamitron

Polish

metamitron

Swedish

metamitron

Hungarian

metamitron

Dutch

metamitron

Norwegian

metamitron

Record last updated:	31/10/2024
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