Amitrole

Amitrole	Last updated: 04/04/2024
(Also known as: aminotriazole; amitolamitril; weedazol)

SUMMARY

Amitrole is a triazole herbicide that is used to control a wide range of perennial grasses and broad-leaved weeds. It is volatile, highly soluble in water and, based on its chemical properties, is moderately mobile with some potential for leaching to groundwater. It is not persistent in soil systems, degradation being very rapid but may be expected to persistent in surface water under normal conditions. Amitrole has a low mammalian toxicity and is not expected to bioaccumulate. It has a moderate toxicity to most terrestrial and aquatic species.

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 chronic ecotoxicity: Moderate; Daphnia acute ecotoxicity: Moderate; Daphnia chronic ecotoxicity: Moderate; Earthworms acute ecotoxicity: Moderate	Human health High alert: Mammals chronic toxicity: High; Genotoxic

GENERAL INFORMATION

Description

A triazole herbicide used to control a wide range of perennial grasses and broad-leaved weeds.

Example pests controlled

Poison ivy; Nutgrass; Water couch; Water hyacinth; Clovers; Thistles; Chickweed; Wild oats; Brambles

Example applications

Vineyards; Non-cropped situations including roadsides; drains; ditches; Eucalupytus; Pine plantations

Efficacy & activity

Availability status

Current

Introduction & key dates

1953, first reported

UK regulatory status

UK COPR regulatory status

Not approved

Date COPR inclusion expires

Expired

UK LERAP status

No UK approval for use

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

Expired

EU Candidate for substitution (CfS)

Not applicable

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

C₂H₄N₄

Canonical SMILES

C1=NNC(=N1)N

Isomeric SMILES

No data

International Chemical Identifier key (InChIKey)

KLSJWNVTNUYHDU-UHFFFAOYSA-N

International Chemical Identifier (InChI)

InChI=1S/C2H4N4/c3-2-4-1-5-6-2/h1H,(H3,3,4,5,6)

2D structure diagram/image available?

Yes

General status

Pesticide type

Herbicide

Substance groups

Triazole herbicide

Minimum active substance purity

910 g kg⁻¹

Known relevant impurities

EU dossier - N-(1H-(1,2,4)-triazol-3-yl)-formamide <13 g kg⁻¹; 4H-(1,2,4)-triazole-3,4-diamine < 12 g kg⁻¹; methanoic acid <7 g kg⁻¹

Substance origin

Synthetic

Mode of action

Translocated, foliar-acting, non-selective action. Inhibition of lycopene cyclase.

CAS RN

61-82-5

EC number

200-521-5

CIPAC number

US EPA chemical code

004401

PubChem CID

1639

CLP index number

613-011-00-6

Molecular mass

84.08

PIN (Preferred Identification Name)

1H-1,2,4-triazol-3-amine

IUPAC name

1H-1,2,4-triazol-3-amine

CAS name

1H-1,2,4-triazol-3-amine

Other status information

OSPAR candidate; 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 crystals

Formulations

Property

Value

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

NuFarm
Bayer
American Cyanamid
Makhteshim-Agan
Fairmount
Conquest Crop Protection Pty Ltd
Nutrien Ag Solutions Limited

Example products using this active

Weedazol TL
Herbizole
Diurol
Amerol
CA 2735
Amizol
Cytrol
Conquest WeedWarden
Genfarm Amitrole 250SL

Formulation and application details

Spray application usually formulated as a concentrated liquid or soluble powder

ENVIRONMENTAL FATE

Property

Value

Source; quality score; and other information

Interpretation

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

264000

High

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

Toluene

27000

Isopropanol

100

Dichloromethane

2900

Acetone

Melting point (°C)

155

Boiling point (°C)

Decomposes before boiling

Degradation point (°C)

Flashpoint (°C)

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

1.07 X 10^-01

Calculated

Log P

-0.97

Low

Fat solubility of residues

Solubility

Insoluble

Data type

Regulatory data

Density (g ml⁻¹)

1.14

Dissociation constant pKa) at 25 °C

4.14

Weak acid pKa(2) 10.7

Vapour pressure at 20 °C (mPa)

0.033

Low volatility

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

1.76 X 10^-08

Non-volatile

Volatilisation as max % of applied dose lost

From plant surface

24 hr

Volatilisation is not considered critical for air pollution

From soil surface

Negligible

24 hr

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

198nm = 4947

Surface tension (mN m⁻¹)

73.3

Degradation

Property

Value

Source; quality score; and other information

Interpretation

General biodegradability

Soil degradation (days) (aerobic)

DT₅₀ (typical)

7.4

Non-persistent

DT₅₀ (lab at 20 °C)

7.4

Non-persistent

DT₅₀ (field)

Non-persistent

DT₉₀ (lab at 20 °C)

82.88

Moderately persistent

DT₉₀ (field)

350

DT₅₀ modelling endpoint

Note

EU dossier lab studies DT₅₀ range 4.3-17.6 dats; DT₉₀ range 11.2-289.7, soils=5; Field studies DT₅₀ range 6.8-28.1 days, DT₉₀ range 109.3-717.6, 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

Stable

Note

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

Value

Stable

Note

Not pH sensitive

Water-sediment DT₅₀ (days)

309

Slow

Water phase only DT₅₀ (days)

Stable

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.

Soil adsorption and mobility

Property

Value

Source; quality score; and other information

Interpretation

Linear

K_d

K_oc

Notes and range

Freundlich

K_f

1.60

Moderately mobile

K_foc

¹/_n

0.80

Notes and range

EU dossier, K_f range 0.152-3.79 mL g⁻¹, kfoc range 20-202, ¹/_n range 0.65-0.87, Soils=8

pH sensitivity

Fate indices

Property

Value

Source; quality score; and other information

Interpretation

GUS leaching potential index

2.48

Calculated

Transition state

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

Value

1.01 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

4.8

Calculated using the Atkinson method. Assumed 5.0E+05 OH/cm³, 24 hr

Below the level of concern for long-range air transport

Bio-concentration factor

BCF (l kg⁻¹)

2.4

Low potential

CT₅₀ (days)

Known soil metabolites

Metabolite

Major/Minor fraction

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

Estimated maximum occurrence fraction

Notes

1,2,4-triazole (Ref: CGA 71019)

Major 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)

1,2,4-triazole (Ref: CGA 71019)

Relevant

Other known metabolites

Metabolite name and reference

Aliases

Formation medium / Rate

Estimated maximum occurrence fraction

Metabolising enzymes

3-(3-amino-1,2,4-triazol-1-yl)-2-aminopropionic acid

aminotriazolylalanine

Plant

3-(1,2,4-triazol-1-yl)-2-aminopropionic acid

triazolylalanine

Plant

1,2,4-triazole (Ref: CGA 71019)

Surface water; Sediment

ECOTOXICOLOGY

Terrestrial ecotoxicology

Property

Value

Source; quality score; and other information

Interpretation

Mammals - Acute oral LD₅₀ (mg kg⁻¹)

> 5000

Rat

Low

Mammals - Short term dietary NOEL

(mg kg⁻¹)

(ppm diet)

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

0.9

Rat Reproductive NOAEL

High

Birds - Acute LD₅₀ (mg kg⁻¹)

> 2150

Colinus virginianus

Low

Birds - Short term dietary (LC₅₀/LD₅₀)

> 5000 ppm

Colinus virginianus

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

12.1

Anas platyrhynchos NOEC

Moderate

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

> 448

Moderate

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

Soil micro-organisms

Nitrogen mineralisation: Transient retardation, recovery after 42 days
Carbon mineralisation: No significant adverse effect

Dose: Not stated

Collembola

Acute LC₅₀ (mg kg⁻¹)

Chronic NOEC (mg kg⁻¹)

Non-target plants

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)

> 152

Apis mellifera

Low

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

Chronic

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

> 10305

Aphidius rhopalosiphi

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

824.4

Typhlodromus pyri

Beneficial insects (Ground beetles) as % Mortality at dose 4.72 kg ha⁻¹

3.7

Poecilus cupreus

Aquatic ecotoxicology

Property

Value

Source; quality score; and other information

Interpretation

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

> 1000

Oncorhynchus mykiss

Low

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

100

Oncorhynchus mykiss

Low

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

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

6.1

Daphnia magna

Moderate

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

0.32

Daphnia magna

Moderate

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

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

2.8

Americamysis bahia

Moderate

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)

2.5

Lemna gibba

Moderate

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

2.3

Scenedesmus subspicatus

Moderate

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

Chlorella vulgaris

Moderate

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)

> 5000

Rat

Low

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

2500

Rat

Mammals - Inhalation LC₅₀ (mg l⁻¹)

> 0.439

Rat 4 hr

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)

0.015

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

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

0.001

Dermal penetration studies (%)

Dangerous Substances Directive 76/464

Exposure Routes

Public

Minimal risk of dietary exposure, some risk to bystanders

Occupational

Risk of exposure, PPE required

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

Possible thyroid toxicant
IARC Group 3 carcinogen - not classifiable; Toxics Release Inventory (TRI) Program listed carcinogen; US NTP - suspected carcinogen; OSHA - known human carcinogen; US EPA - probable human carcinogen

Handling issues

Property

Value and interpretation

General

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

CLP classification 2013

Health: H361d, H373
Environment: H411

WHO Classification

U (Unlikely to present an acute hazard)

UN Number

UN3077

Waste disposal & packaging

Packaging Group III (minor danger)

Shelf-life, storage, stability and reactivity

TRANSLATIONS

Language

Name

English

amitrole

French

amitrole

German

Amitrol

Danish

amitrol

Italian

amitrolo

Spanish

amitrol

Greek

Polish

amitrol

Swedish

Hungarian

Dutch

amitrol

Norwegian

Record last updated:	04/04/2024
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