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Imazamethabenz-methyl (Ref: AC 222293)
Last updated: 11/02/2021
(Also known as: imazamethabenz, methyl variant; CL 222293)

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:
Earthworms acute ecotoxicity: Moderate
Human health
Moderate alert:
Possible Reproduction/development effects
GENERAL INFORMATION
Description
A post-emergence herbicide for use in winter cereals and other crops to control grasses and some dicotyledonous weeds
Example pests controlled
Grasses and some dicotyledonous weeds
Example applications
Sunflowers; Wheat; Barley
Efficacy & activity
-
Availability status
Current
Introduction & key dates
1982, first reported; 1998, first registered 1988
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
UK
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
                 
Also used in
Also used in
USA
Chemical structure
Isomerism
A chiral molecule
Chemical formula
C₁₆H₂₀N₂O₃
Canonical SMILES
COC(=O)c1ccc(C)cc1C2=NC(C)(C(C)C)C(=O)N2.COC(=O)c3cc(C)ccc3C4=NC(C)(C(C)C)C(=O)N4
Isomeric SMILES
No data
International Chemical Identifier key (InChIKey)
WXUNXXKSYBUHMK-UHFFFAOYSA-N
International Chemical Identifier (InChI)
InChI=1S/C16H20N2O3/c1-9(2)16(4)15(20)17-13(18-16)12-8-10(3)6-7-11(12)14(19)21-5/h6-9H,1-5H3,(H,17,18,20)
2D structure diagram/image available?
Yes
General status
Pesticide type
Herbicide
Substance group
Imidazolinone
Minimum active substance purity
-
Known relevant impurities
-
Substance origin
Synthetic
Mode of action
Selective, systemic absorbed through roots and leaves. Inhibits plant amino acid synthesis - acetohydroxyacid synthase AHAS.
CAS RN
81405-85-8
EC number
-
CIPAC number
529
US EPA chemical code
128842
PubChem CID
54744
Molecular mass
288.3
PIN (Preferred Identification Name)
-
IUPAC name
mix of methyl 6-[(RS)-4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl]-m-toluate and methyl 2-[(RS)-4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl]-p-toluate
CAS name
methyl 2-[4,5-dihydro-4-methyl-4-(1-methylethyl)-5-oxo-1H-imidazol-2-yl]-4(or 5)-methylbenzoate
Other status information
-
Relevant Environmental Water Quality Standards
-
Herbicide Resistance Classification (HRAC)
B
Herbicide Resistance Classification (WSSA)
2
Insecticide Resistance Classification (IRAC)
Not applicable
Fungicide Resistance Classification (FRAC)
Not applicable
Examples of recorded resistance
Avena fatua, Alopecurus myosuroides
Physical state
Off-white powder
Formulations
Property
Value
Example manufacturers & suppliers of products using this active now or historically
  • Assert
Example products using this active
  • BASF
  • Nufarm Americas Inc.
Formulation and application details
Usually supplied as a liquid concentrate or as soluble granules.
ENVIRONMENTAL FATE
Property
Value
Source; quality score; and other information
Interpretation
Solubility - In water at 20 °C (mg l⁻¹)
1114
K4 K = Research datasets, e.g. Pandora, Demetra
4 = Verified data
High
Solubility - In organic solvents at 20 °C (mg l⁻¹)
291000
C4 C = AGRITOX (click here )
4 = Verified data
Acetone
-
135000
C4 C = AGRITOX (click here )
4 = Verified data
Chloroform
-
57500
C4 C = AGRITOX (click here )
4 = Verified data
Xylene
-
400
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
n-Hexane
-
Melting point (°C)
131
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
-
Boiling point (°C)
- - -
Degradation point (°C)
- - -
Flashpoint (°C)
93
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
(closed cup)
-
Octanol-water partition coefficient at pH 7, 20 °C
P
3.47 X 1001 Calculated -
Log P
1.54
H4 H = The US ARS pesticide properties database (click here )
4 = Verified data
Low
Bulk density (g ml⁻¹)
0.3
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
-
Dissociation constant pKa) at 25 °C
2.9
DW4 DW = Don Wauchope personal database for Pka data: Wauchope, R. D. and Edwards, J. Dissociation constants for pesticide active ingredients: a database and comparison with predicted values. MS in preparation
4 = Verified data
-
Strong acid
Vapour pressure at 20 °C (mPa)
1.50 X 10-03
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
Low volatility
Henry's law constant at 25 °C (Pa m³ mol⁻¹)
5.05 X 10-07
H4 H = The US ARS pesticide properties database (click here )
4 = Verified data
Non-volatile
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)
47
K4 K = Research datasets, e.g. Pandora, Demetra
4 = Verified data
Moderately persistent
DT₅₀ (lab at 20 °C)
47
K4 K = Research datasets, e.g. Pandora, Demetra
4 = Verified data
Moderately persistent
DT₅₀ (field)
- - -
DT₉₀ (lab at 20 °C)
- - -
DT₉₀ (field)
- - -
DT₅₀ modelling endpoint
- - -
Note
General literature DT₅₀ range 45-57 days (R3)
Dissipation rate RL₅₀ on plant matrix
Value
- - -
Note
-
Dissipation rate RL₅₀ on and in plant matrix
Value
- - -
Note
-
Aqueous photolysis DT₅₀ (days) at pH 7
Value
36
K4 K = Research datasets, e.g. Pandora, Demetra
4 = Verified data
Stable
Note
-
Aqueous hydrolysis DT₅₀ (days) at 20 °C and pH 7
Value
133
K4 K = Research datasets, e.g. Pandora, Demetra
4 = Verified data
Persistent
Note
Slow at pH 5 to pH7, rapid at pH 9
Water-sediment DT₅₀ (days)
- - -
Water phase only DT₅₀ (days)
7
K4 K = Research datasets, e.g. Pandora, Demetra
4 = Verified data
Moderately fast
Soil adsorption and mobility
Property
Value
Source; quality score; and other information
Interpretation
Linear
Kd
-
H3 H = The US ARS pesticide properties database (click here )
3 = Unverified data of known source
Mobile
Koc
35
Notes and range
Other sources: 51 mL g⁻¹ (DW3)
Freundlich
Kf
- - -
Kfoc
-
1/n
-
Notes and range
-
pH sensitivity
-
Fate indices
Property
Value
Source; quality score; and other information
Interpretation
GUS leaching potential index
4.11 Calculated High leachability
SCI-GROW groundwater index (μg l⁻¹) for a 1 kg ha⁻¹ or 1 l ha⁻¹ application rate
Value
1.21 X 1000 Calculated -
Note
-
Potential for particle bound transport index
Medium Calculated -
Potential for loss via drain flow
Mobile Calculated -
Key metabolites
Metabolite
Formation medium
Estimated maximum occurrence fraction
1107/2009 relevancy
imazamethabenz (Ref: AC 263840)
Soil - -
ECOTOXICOLOGY
Property
Value
Source; quality score; and other information
Interpretation
Bio-concentration factor
BCF (l kg⁻¹)
Low risk
Q3 Q = Miscellaneous internet resources
3 = Unverified data of known source
Based on LogP < 3
Low risk
CT₅₀ (days)
- -
Mammals - Acute oral LD₅₀ (mg kg⁻¹)
> 5000
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
Rat
Low
Mammals - Short term dietary NOEL
(mg kg⁻¹)
12.5
L2 L = Pesticide manuals and hard copy reference books / other sources
2 = Unverified data of unknown source
Rat 2 year
High
(ppm diet)
- -
Mammals - Chronic 21d NOAEL (mg kg⁻¹ bw d⁻¹)
- - -
Birds - Acute LD₅₀ (mg kg⁻¹)
> 2150
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
Anas platyrhynchos
Low
Birds - Short term dietary (LC₅₀/LD₅₀)
- - -
Birds - Chronic 21d NOEL (mg kg⁻¹ bw d⁻¹)
- - -
Fish - Acute 96 hour LC₅₀ (mg l⁻¹)
> 100
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
Oncorhynchus mykiss
Low
Fish - Chronic 21 day NOEC (mg l⁻¹)
- - -
Aquatic invertebrates - Acute 48 hour EC₅₀ (mg l⁻¹)
> 220
J4 J = Pesticide Action Network database (click here )
4 = Verified data
Daphnia magna
Low
Aquatic invertebrates - Chronic 21 day NOEC (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)
- - -
Non-target plants
- - -
- - -
Algae - Acute 72 hour EC₅₀, growth (mg l⁻¹)
78.1
F4 F = U.S. EPA ECOTOX database / U.S. EPA pesticide fate database / Miscellaneous WHO documents (US EPA Databases Related to Pesticide Risk Assessment )
4 = Verified data
Pseudokirchneriella subcapitata
Low
Algae - Chronic 96 hour NOEC, growth (mg l⁻¹)
50
Q2 Q = Miscellaneous internet resources
2 = Unverified data of unknown source
Unknown species
Low
Honeybees (Apis 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)
> 100
K4 K = Research datasets, e.g. Pandora, Demetra
4 = Verified data
Low
Unknown mode acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg bee⁻¹)
- - -
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 pollinators (1)
Acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg insect⁻¹)
- - -
Mode of exposure
-
Other pollinators (2)
Acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg insect⁻¹)
- - -
Mode of exposure
-
Earthworms - Acute 14 day LC₅₀ (mg kg⁻¹)
> 123
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
Eisenia foetida
Moderate
Earthworms - Chronic NOEC, reproduction (mg kg⁻¹)
- - -
Other soil macro-organisms
Acute LC₅₀ (mg kg⁻¹)
- - -
Chronic NOEC (mg kg⁻¹)
- - -
Other arthropod (1)
LR₅₀ g ha⁻¹
- - -
% Effect
- - -
Other arthropod (2)
LR₅₀ g ha⁻¹
- - -
% Effect
- - -
Soil micro-organisms
- - -
Mesocosm study data
NOEAEC mg l⁻¹
- - -
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
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
Rat
Low
Mammals - Dermal LD₅₀ (mg kg⁻¹ body weight)
2000
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
Rabbit
-
Mammals - Inhalation LC₅₀ (mg l⁻¹)
5.8
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
Rat
-
Other Mammal toxicity endpoints
- - -
ADI - Acceptable Daily Intake (mg kg⁻¹ bw day⁻¹)
0.0625
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
-
ARfD - Acute Reference Dose (mg kg⁻¹ bw day⁻¹)
- - -
AAOEL - Acute Acceptable Operator Exposure Level (mg kg⁻¹ bw day⁻¹)
- - -
AOEL - Acceptable Operator Exposure Level - Systemic (mg kg⁻¹ bw day⁻¹)
- - -
Dermal penetration studies (%)
- - -
Dangerous Substances Directive 76/464
- - -
Exposure Routes
Public
-
Occupational
-
MRLs
European
EU MRL pesticide database 
Notes
-
Drinking Water Standards
- - -
Drinking Water MAC (μg l⁻¹)
- - -
Health issues
Specific human health issues
Carcinogen
Genotoxic
Endocrine disruptor
XNo, known not to cause a problem
A3 A = Chromosome aberration (EFSA database)
3 = Negative
;
B0 B = DNA damage/repair (EFSA database)
0 = No data
;
C0 C = Gene mutation (EFSA database)
0 = No data
;
D0 D = Genome mutation (EFSA database)
0 = No data
;
E0 E = Unspecified genotoxicity type (miscellaneous data source)
0 = No data
No data found
Reproduction / development effects Acetyl cholinesterase inhibitor Neurotoxicant
?Possibly, status not identified
XNo, known not to cause a problem
XNo, known not to cause a problem
Respiratory tract irritant Skin irritant Skin sensitiser
Yes, known to cause a problem
XNo, known not to cause a problem
No data found
Eye irritant Phototoxicant  
Yes, known to cause a problem
No data found  
General human health issues
May cause irreversible eye damage
Handling issues
Property
Value and interpretation
General
Prevent generation of mists
Corrosive
CLP classification 2013
Not classified: Obsolete
EC Risk Classification
Xi - Irritant: R36
N - Dangerous for the environment: R50
EC Safety Classification
-
WHO Classification
U (Unlikely to present an acute hazard)
UN Number
-
Waste disposal & packaging
-
TRANSLATIONS
Language
Name
English
imazamethabenz-methyl
French
imazamethabenz
German
Imazamethabenz-methyl
Danish
imazamethabenz-methyl
Italian
imazamethabenz
Spanish
imazametabenz-metil
Greek
-
Polish
imazametabenz metylu
Swedish
-
Hungarian
-
Dutch
imazamethabenzmethyl

Record last updated: 11/02/2021
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