Metazachlor (Ref: BAS 47900H)

Metazachlor (Ref: BAS 47900H)	Last updated: 09/01/2025
(Also known as: metazachlore)

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: Drainflow: Mobile	Ecotoxicity Moderate alert: 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 Moderate alert: Mammals chronic toxicity: Moderate; Possible Carcinogen; Reproduction/development effects

GENERAL INFORMATION

Description

A residual herbicide used to control a wide range of weeds in crops, ornamental trees and shrubs

Example pests controlled

Grass weeds including meadow grass; Broadleaved weeds

Example applications

Winter and spring OSR; Brussel spouts; Maize; Peanuts; Sugarcane; Cotton; Tobacco; White cedar; Rhododendron; Pivet; Lilac Alder; Grey willow; Spruce

Efficacy & activity

Availability status

Current

Introduction & key dates

1982, introduced

GB regulatory status

GB COPR regulatory status

Approved

Date COPR inclusion expires

31/07/2029

GB LERAP status

Check label - may vary with formulation

EC Regulation 1107/2009 (repealing 91/414)

EC Regulation 1107/2009 status

Approved

Dossier rapporteur/co-rapporteur

Netherlands/Portugal

Date EC 1107/2009 inclusion expires

31/10/2026

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

Morocco

Chemical structure

Isomerism

None

Chemical formula

C₁₄H₁₆ClN₃O

Canonical SMILES

CC1=C(C(=CC=C1)C)N(CN2C=CC=N2)C(=O)CCl

Isomeric SMILES

No data

International Chemical Identifier key (InChIKey)

STEPQTYSZVCJPV-UHFFFAOYSA-N

International Chemical Identifier (InChI)

InChI=1S/C14H16ClN3O/c1-11-5-3-6-12(2)14(11)18(13(19)9-15)10-17-8-4-7-16-17/h3-8H,9-10H2,1-2H3

2D structure diagram/image available?

Yes

Cambridge Crystallographic Data Centre diagrams

Common Name	Relationship	Link
metazachlor	-

General status

Pesticide type

Herbicide

Substance groups

Chloroacetamide herbicide; Pyrazole herbicide

Minimum active substance purity

Known relevant impurities

Substance origin

Synthetic

Mode of action

Ergosterol inhibitor. Inhibition of very long chain fatty acids (VLCFA, inhibition of cell division)

CAS RN

67129-08-2

EC number

266-583-0

CIPAC number

411

US EPA chemical code

PubChem CID

49384

CLP index number

616-205-00-9

Molecular mass

277.75

PIN (Preferred Identification Name)

IUPAC name

2-chloro-N-(pyrazol-1-ylmethyl)acet-2',6'-xylidide

CAS name

2-chloro-N-(2,6-dimethylphenyl)-N-(1H-pyrazol-1-ylmethyl)acetamide

Other status information

PAN listed Highly Hazardous Chemical; 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

Physical state

Colourless crystals

Formulations

Property

Value

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

AgriGuard
BASF
Clayton
Makhteshim-Agan
Nufarm
Standon

Example products using this active

Alpha Metazachlor
Nimbus CS
Rapsan 500SC
Shadow
Springbok
Sultan

Formulation and application details

Often supplied as a soluble or suspension concentrate

ENVIRONMENTAL FATE

Property

Value

Source; quality score; and other information

Interpretation

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

450

Moderate

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

5000

Hexane

250000

Acetone

265000

Toluene

250000

Dichloromethane

Melting point (°C)

Variable

Boiling point (°C)

Degradation point (°C)

Flashpoint (°C)

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

3.09 X 10⁰²

Calculated

Log P

2.49

Low

Fat solubility of residues

Solubility

Insoluble

Data type

Regulatory data - observations in feeding studies showed low residue content in animal fats

Density (g ml⁻¹)

1.31

Dissociation constant pKa) at 25 °C

Not applicable

No dissociation

Vapour pressure at 20 °C (mPa)

0.089

Low volatility

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

5.9 X 10^-05

Non-volatile

Volatilisation as max % of applied dose lost

From plant surface

10.6

Beans 24 hr

Volatilisation is not considered critical for air pollution

From soil surface

4.0

Beans 24 hr

Volatilisation is not considered critical for air pollution

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

Surface tension (mN m⁻¹)

Degradation

Property

Value

Source; quality score; and other information

Interpretation

General biodegradability

Soil degradation (days) (aerobic)

DT₅₀ (typical)

8.6

Non-persistent

DT₅₀ (lab at 20 °C)

10.8

Non-persistent

DT₅₀ (field)

6.8

Non-persistent

DT₉₀ (lab at 20 °C)

DT₉₀ (field)

DT₅₀ modelling endpoint

Note

EU dossier lab studies DT₅₀ range 5.5-25.3 days, field studies DT₅₀ range 2.8-21.3 days; Other data - field studies DT₅₀ range 26-114 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

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

Value

Stable

Note

Stable pH 4 to pH 9

Water-sediment DT₅₀ (days)

20.6

Fast

Water phase only DT₅₀ (days)

216

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)

0.78

Mobile

K_oc (mL g⁻¹)

54.0

Notes and range

EU dossier K_d range 0.37-1.66 mL g⁻¹, K_oc range 29.2-73.1 mL g⁻¹, Soils=4

Freundlich

K_f (mL g⁻¹)

1.02

Moderately mobile

K_foc (mL g⁻¹)

79.6

¹/_n

0.993

Notes and range

EU dossier K_f range 0.37-2.20 mL g⁻¹, K_foc range 72.5-83.5 mL g⁻¹, ¹/_n range 0.988-0.996, Soils=4

pH sensitivity

Fate indices

Property

Value

Source; quality score; and other information

Interpretation

GUS leaching potential index

1.75

Calculated

Low leachability

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

Value

1.08 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

6.5

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

Below the level of concern for long-range air transport

Bio-concentration factor

BCF (l kg⁻¹)

Low risk

Based on LogP < 3

Low risk

CT₅₀ (days)

Known soil metabolites

Metabolite

Major/Minor fraction

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

Estimated maximum occurrence fraction

Notes

metazachlor oxalic acid (Ref: BH 479-4)

Major fraction

0.162

BASF verified

metazachlor sulfonic acid (Ref: BH 479-8)

Major fraction

0.216

BASF verified

N-(2,6-dimethylphenyl)-N-(1H-pyrazol-1-ylmethyl)aminocarbonylmethylsulfinyl acetic acid (Ref: BH 479-9)

Minor fraction

0.053

BASF verified; CAS NR: 1246215-97-3

methyl N-(2,6-dimethylphenyl)-N-(1H-pyrazol-1-ylmethyl)aminocarbonylmethylsulfoxide (Ref: BH 479-11)

Minor fraction

0.075

BASF verified; CAS NR: 1242182-77-9

N-[(2-hydroxycarbonyl-6-methyl)phenyl]-N-(1H-pyrazol-1-ylmethyl)oxalamide (Ref: BH 479-12)

Minor fraction

0.03

BASF 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)

metazachlor oxalic acid (Ref: BH 479-4)

Not relevant

0.33

1980

metazachlor sulfonic acid (Ref: BH 479-8)

Not relevant

0.2

1200

N-(2,6-dimethylphenyl)-N-(1H-pyrazol-1-ylmethyl)aminocarbonylmethylsulfinyl acetic acid (Ref: BH 479-9)

Relevant

0.05

300

methyl N-(2,6-dimethylphenyl)-N-(1H-pyrazol-1-ylmethyl)aminocarbonylmethylsulfoxide (Ref: BH 479-11)

Relevant

0.002

Other known metabolites

Metabolite name and reference

Aliases

Formation medium / Rate

Estimated maximum occurrence fraction

-
Note: Oral LD50 Rat=3480 mg/kg bw; Possible carcinogen

C16H19N3SO4; Metazochlor M09; 479M09

Surface water; Sediment

-
Note: Oral LD50 Rat between 500 & 2000 mg/kg bw; Possible carcinogen

C15H18N3SO2; Metazochlor M11; 479M011

Surface water; Sediment

-
Note: Oral LD50 Rat >2000 mg/kg bw

C14H13N3O5; Metazochlor M12; 479M012

Surface water; Sediment

ECOTOXICOLOGY

Terrestrial ecotoxicology

Property

Value

Source; quality score; and other information

Interpretation

Mammals - Acute oral LD₅₀ (mg kg⁻¹)

3480

Rat

Low

Mammals - Short term dietary NOEL

(mg kg⁻¹)

3.6

Rat

High

(ppm diet)

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

192

Rat Reproductive NOAEL

Moderate

Birds - Acute LD₅₀ (mg kg⁻¹)

> 2000

Colinus virginianus

Low

Birds - Short term dietary (LC₅₀/LD₅₀)

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

76.5

Colinus virginianus NOEL

Moderate

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

500

Eisenia foetida corr

Moderate

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

> 2.31

Eisenia foetida

Moderate

Soil micro-organisms

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

Dose: 7.5 mg kg⁻¹ 28 Day

Collembola

Acute LC₅₀ (mg kg⁻¹)

Chronic NOEC (mg kg⁻¹)

205

Folsomia candida corr

Non-target plants

35.1

Lettuce Glasshouse
Seedling emergence, ER₅₀
as mL product ha⁻¹ (BAS 479 22 H: Conc 500g kg⁻¹)

219.1

Rye grass Glasshouse
Vegetative vigour, ER₅₀
as mL product ha⁻¹ (BAS 479 22 H: Conc 500g kg⁻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)

> 72.2

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)

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

> 1250

Aphidius rhopalosiphi

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

> 1250

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)

8.5

Oncorhynchus mykiss

Moderate

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

2.15

Oncorhynchus mykiss

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)

0.1

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)

9.8

Chironomus riparius

Moderate

Sediment dwelling organisms - Chronic 28 day NOEC, sediment (mg kg⁻¹)

7.93

Chironomus riparius

Moderate

Aquatic plants (free-floating, growth) - Acute 7 day EC₅₀, biomass (mg l⁻¹)

0.0023

Lemna gibba

High

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

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

0.0162

Pseudokirchneriella subcapitata

Moderate

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

0.34

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)

3480

Rat

Low

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

2000

Rat

Mammals - Inhalation LC₅₀ (mg l⁻¹)

34.5

Rat

Other Mammal toxicity endpoints

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

0.08

Rat SF=100

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

0.5

Rat SF=100

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

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

0.2

Rat SF=100

Dermal penetration studies (%)

2.0-100.0

concentration dependent

Dangerous Substances Directive 76/464

Exposure Routes

Public

No unacceptable risks identified for bystanders

Occupational

Acceptable risks for authorised pattern of use

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=120 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

Respiratory tract irritant

Skin irritant

Skin sensitiser

Eye irritant

Phototoxicant

No data found

General human health issues

Possible liver toxicant
CLP data - suspected carcingen

Handling issues

Property

Value and interpretation

General

IMDG Transport Hazard Class 9

CLP classification 2013

Health: H317, H351
Environment: H400, H410

WHO Classification

III (Slightly hazardous)

UN Number

UN1993

Waste disposal & packaging

Packaging Group III (minor danger)

Shelf-life, storage, stability and reactivity

TRANSLATIONS

Language

Name

English

metazachlor

French

metazachlore

German

Metazachlor

Danish

metazachlor

Italian

metazaclor

Spanish

metazaclor

Greek

Polish

metazachlor

Swedish

metazaklor

Hungarian

metazaklor

Dutch

metazachloor

Norwegian

Record last updated:	09/01/2025
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