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Imazapic (Ref: AC 263222)
Last updated: 11/02/2021
(Also known as: imazamethapyr; imazameth; CL 263222)

SUMMARY
Imazapic is a selective pre- and post-emergent herbicide without EU regulatory approval for use. It has a high aqueous solubility, is volatile and, based on its chemical properties, is moderately mobile and may leach to groundwater. It is may be persistent in soil systems but usually degrades quickly in aquatic systems via photolysis. It has a low mammalian toxicity and has a high potential for bioaccumulation. It has a low level of toxicity to birds but is more toxic to aquatic life and honey bees.
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:
Persistent; GUS: High leachability
Ecotoxicity
Moderate alert:
Fish chronic ecotoxicity: Moderate
Human health
Low alert
GENERAL INFORMATION
Description
A selective herbicide used for both the pre- and post-emergent control of some grasses and broad-leaved weeds.
Example pests controlled
Annual and perennial grasses and some broad-leaved weeds
Example applications
Peanuts; Rangeland; Non-cropped areas
Efficacy & activity
-
Availability status
Current
Introduction & key dates
1996
UK regulatory status
UK COPR regulatory status
Not approved
Date COPR inclusion expires
Not applicable
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
Not applicable
Date EC 1107/2009 inclusion expires
Not applicable
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
                 
Additional information
Also used in
Australia, USA
Chemical structure
Isomerism
Imazapic is a molecule with one chiral centre. The technical material is an isomeric mixture.
Chemical formula
C₁₄H₁₇N₃O₃
Canonical SMILES
CC1=CN=C(C(=C1)C(=O)O)C2=NC(C(=O)N2)(C)C(C)C
Isomeric SMILES
No data
International Chemical Identifier key (InChIKey)
PVSGXWMWNRGTKE-UHFFFAOYSA-N
International Chemical Identifier (InChI)
InChI=1S/C14H17N3O3/c1-7(2)14(4)13(20)16-11(17-14)10-9(12(18)19)5-8(3)6-15-10/h5-7H,1-4H3,(H,18,19)(H,16,17,20)
2D structure diagram/image available?
Yes
Cambridge Crystallographic Data Centre diagrams
Common Name Relationship Link
imazapic -
General status
Pesticide type
Herbicide
Substance group
Imidazolinone
Minimum active substance purity
-
Known relevant impurities
-
Substance origin
Synthetic
Mode of action
Selective, systemic, contact and residual activity, inhibiting the production of amino acids necessary for cell division and growth. Inhibits plant amino acid synthesis - acetohydroxyacid synthase AHAS.
CAS RN
104098-48-8
EC number
-
CIPAC number
None allocated
US EPA chemical code
129041
PubChem CID
91770
Molecular mass
275.30
PIN (Preferred Identification Name)
rac-5-methyl-2-[(4R)-4-methyl-5-oxo-4-(propan-2-yl)-4,5-dihydro-1H-imidazol-2-yl]pyridine-3-carboxylic acid
IUPAC name
2-[(RS)-4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl]-5-methylnicotinic acid
CAS name
2-[4,5-dihydro-4-methyl-4-(1-methylethyl)-5-oxo-1H-imidazol-2-yl]-5-methyl-3-pyridinecarboxylic acid
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
Amaranthus palmeri
Physical state
Pale tan coloured powder
Related substances & organisms
Formulations
Property
Value
Example manufacturers & suppliers of products using this active now or historically
  • BASF
  • Makhteshim Agan Group
  • Amercian Cyanamid
Example products using this active
  • Cadre
  • Plateau
  • Impose
  • Panoramic
Formulation and application details
Often supplied as watter dispersible granules
ENVIRONMENTAL FATE
Property
Value
Source; quality score; and other information
Interpretation
Solubility - In water at 20 °C (mg l⁻¹)
2230
V3 V = ChemID online databases / IPCS INCHEM (ChemID; IPCS INCHEM )
3 = Unverified data of known source
at 25 °C
High
Solubility - In organic solvents at 20 °C (mg l⁻¹)
18.9
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
Acetone
-
Melting point (°C)
205
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)
- - -
Octanol-water partition coefficient at pH 7, 20 °C
P
2.95 X 1002 Calculated -
Log P
2.47
V3 V = ChemID online databases / IPCS INCHEM (ChemID; IPCS INCHEM )
3 = Unverified data of known source
Low
Bulk density (g ml⁻¹)
1.31
Q2 Q = Miscellaneous internet resources
2 = Unverified data of unknown source
-
Dissociation constant pKa) at 25 °C
2.0
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
-
Strong acid; pKa(2) 3.6; pKa(3) 11.1
Vapour pressure at 20 °C (mPa)
0.01
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)
- - -
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)
120
Q3 Q = Miscellaneous internet resources
3 = Unverified data of known source
Persistent
DT₅₀ (lab at 20 °C)
- - -
DT₅₀ (field)
232
F3 F = U.S. EPA ECOTOX database / U.S. EPA pesticide fate database / Miscellaneous WHO documents (US EPA Databases Related to Pesticide Risk Assessment )
3 = Unverified data of known source
Persistent
DT₉₀ (lab at 20 °C)
- - -
DT₉₀ (field)
- - -
DT₅₀ modelling endpoint
- - -
Note
Literature DT₅₀ values range 31-410 days. Main degradation route is microbial.
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
0.3
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
Fast
Note
-
Aqueous hydrolysis DT₅₀ (days) at 20 °C and pH 7
Value
- - -
Note
-
Water-sediment DT₅₀ (days)
- - -
Water phase only DT₅₀ (days)
- - -
Soil adsorption and mobility
Property
Value
Source; quality score; and other information
Interpretation
Linear
Kd
-
US3 US = US Dept of Agriculture National Resources Conservation Service - various datasheets, databases and online sources
3 = Unverified data of known source
Moderately mobile
Koc
137
Notes and range
-
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
4.41 Calculated High leachability
SCI-GROW groundwater index (μg l⁻¹) for a 1 kg ha⁻¹ or 1 l ha⁻¹ application rate
Value
2.32 X 1000 Calculated -
Note
-
Potential for particle bound transport index
Medium Calculated -
Potential for loss via drain flow
Moderately mobile Calculated -
Key metabolites
Metabolite
Formation medium
Estimated maximum occurrence fraction
1107/2009 relevancy
2-(4,5-dihydro-4-methyl-4-(1-methylethyl)-5-oxo-1H-imidazol-2-yl)-3,5,pyridinecarboxylic acid (Ref: CL-312622)
Soil 0.1 -
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
R4 R = Peer reviewed scientific publications
4 = Verified data
Rat
Low
Mammals - Short term dietary NOEL
(mg kg⁻¹)
- - -
(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
R4 R = Peer reviewed scientific publications
4 = Verified data
Oncorhynchus mykiss
Low
Fish - Chronic 21 day NOEC (mg l⁻¹)
10
P3 P = Other governments and regulators
3 = Unverified data of known source
Danio rerio
Moderate
Aquatic invertebrates - Acute 48 hour EC₅₀ (mg l⁻¹)
> 100
R4 R = Peer reviewed scientific publications
4 = Verified data
Daphnia magna
Low
Aquatic invertebrates - Chronic 21 day NOEC (mg l⁻¹)
- - -
Aquatic crustaceans - Acute 96 hour LC₅₀ (mg l⁻¹)
> 97.7
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
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)
- - -
Non-target plants
- - -
- - -
Algae - Acute 72 hour EC₅₀, growth (mg l⁻¹)
0.051
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
Pseudokirchneriella subcapitata
Moderate
Algae - Chronic 96 hour NOEC, growth (mg l⁻¹)
- - -
Honeybees (Apis spp.)
Contact acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg bee⁻¹)
> 100000
R4 R = Peer reviewed scientific publications
4 = Verified data
Low
Oral acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg bee⁻¹)
- - -
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)
- - -
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
R4 R = Peer reviewed scientific publications
4 = Verified data
Rat
Low
Mammals - Dermal LD₅₀ (mg kg⁻¹ body weight)
2000
R4 R = Peer reviewed scientific publications
4 = Verified data
Rabbit
-
Mammals - Inhalation LC₅₀ (mg l⁻¹)
> 4.83
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
Rat 4 hr
-
Other Mammal toxicity endpoints
- - -
ADI - Acceptable Daily Intake (mg kg⁻¹ bw day⁻¹)
0.5
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 
Great Britain
GB MRL Register 
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
;
E3 E = Unspecified genotoxicity type (miscellaneous data source)
3 = Negative
XNo, known not to cause a problem
Reproduction / development effects Acetyl cholinesterase inhibitor Neurotoxicant
XNo, known not to cause a problem
XNo, known not to cause a problem
XNo, known not to cause a problem
Respiratory tract irritant Skin irritant Skin sensitiser
XNo, known not to cause a problem
?Possibly, status not identified
XNo, known not to cause a problem
Eye irritant Phototoxicant  
Yes, known to cause a problem
No data found  
General human health issues
No further information available
Handling issues
Property
Value and interpretation
General
No information available
CLP classification 2013
Environment: H400, H410
EC Risk Classification
Xi - Irritant: R36
EC Safety Classification
S22, S24/25, S36/37/39
WHO Classification
NL (Not listed)
UN Number
-
Waste disposal & packaging
-
TRANSLATIONS
Language
Name
English
imazapic
French
-
German
-
Danish
-
Italian
-
Spanish
imazapic
Greek
-
Polish
imazapik
Swedish
-
Hungarian
-
Dutch
-

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