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

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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	glyphosate imazapyr

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	-

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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