metribuzin (Ref: DPX G2504) ** metribuzine ** DIC 1468 ** AE F055208 ** Translations

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GENERAL INFORMATION

Description: A pre- and post-emergence herbicide used to control grasses and broad-leaved weeds in a range of crops

Introduction: 1968, first reported; 1971, first marketed

EC Directive 1107/2009 (repealing 91/414):

Status	Annex 1
Dossier rapporteur/co-rapporteur	Germany
Date inclusion expires	30/09/2017

Approved for use () or known to be used () in the following European countries:

AT

BE

BG

CY

CZ

DE

DK

EE

EL

ES

FI

FR

HU

IE

IT

LT

LU

LV

MT

NL

PL

PT

RO

SE

SI

SK

UK

Also registered in: Australia

General status:

Pesticide type	Herbicide
Substance group	Triazinone
Substance origin	Synthetic
Mode of action	Selective, systemic with contact and residual activity. Inhibits photosynthesis (photosystem II).
CAS RN	21087-64-9
EC number	244-209-7
CIPAC number	283
US EPA chemical code	101101
Chemical formula	C8H14N4OS
SMILES	O=C1/C(=N\N=C(\SC)N1N)C(C)(C)C
International Chemical Identifier (InChI)	InChI=1/C8H14N4OS/c1-8(2,3)5-6(13)12(9)7(14-4)11-10-5/h9H2,1-4H3
Structure diagram/image available?	Yes
Molecular mass (g mol-1)	214.29
IUPAC Name	4-amino-6-tert-butyl-4,5-dihydro-3-methylthio-1,2,4-triazin-5-one
CAS Name	4-amino-6-(1,1-dimethylethyl)-3-(methylthio)-1,2,4-triazin-5(4H)-one
Other status information	Potential groundwater contaminant
Herbicide Resistance Classification (HRAC)	C1
Insecticide Resistance Classification (IRAC)	Not applicable
Fungicide Resistance Classification (FRAC)	Not applicable
Physical state	White crystalline solid
Related substances & organisms	flufenacet

Formulations:

Property	Value
Example manufacturers of products using this active	AgriGuard Bayer CropScience DuPont Greencrop Makhteshim-Agan
Example products using this active	Artist Lexone 2 Sencorex WG Shotput Sencor
UK LERAP status	LERAP Category B (may vary with mixtures)
Formulation and application details	Often supplied as wettable granules that are mixed with water and used as a spray.

ENVIRONMENTAL FATE

Property		Value	Source/Quality Score/Other Information	Interpretation
Solubility - In water at 20oC (mg l-1)		1165	A5	High
Solubility - In organic solvents at 20oC (mg l-1)		820	A5 - n-Heptane	-
		60000	A5 - Xylene	-
		250000	A5 - Ethyl acetate	-
		449400	A5 - Acetone	-
Melting Point (oC)		125	A5	-
Boiling Point (oC)		Decomposes before boiling	A5	-
Degradation point (oC)		125	A5	-
Flashpoint (oC)		Not highly flammable	A5	-
Octanol-water partition coefficient at pH 7, 20oC	P	4.47 X 1001	Calculated	-
	Log P	1.65	A5	Low
Bulk density (g ml-1)/Specific gravity		1.26	A5	-
Dissociation constant (pKa) at 25oC		0.99	Q3 - @ 25degC	-
		Note: Strong acid, pKb = 13
Vapour pressure at 25oC (mPa)		0.121	A5	Non-volatile
Henry's law constant at 25oC (Pa m3 mol-1)		2.00 X 10-05	A5	Non-volatile
Henry's law constant at 20oC (dimensionless)		1.49 X 10-09	Q2	Non-volatile
GUS leaching potential index		2.57	Calculated	Transition state
SCI-GROW groundwater index (µg l-1) for a 1 kg ha-1 or 1 l ha-1 application rate	Value	7.64 X 10-02	Calculated	-
	Note	-
Potential for particle bound transport index		-	Calculated	Low
Maximum UV-vis absorption L mol-1 cm-1		294nm = 8175 (mean)	A5	-
Surface tension (mN m-1)		63.1	A5 at 20oC	-

Degradation:

Property		Value	Source/Quality Score/Other Information	Interpretation
Soil degradation (days) (aerobic)	DT50 (typical)	11.5	A5	Non-persistent
	DT50 (lab at 20oC)	11.5	A5	Non-persistent
	DT50 (field)	19	Y4	Non-persistent
	DT90 (lab at 20oC)	49	A5	-
	DT90 (field)	-	-	-
	Note	EU dossier DT50 range 5.3-17.7 days, DT90 range 17.6-91.8 days
Aqueous photolysis DT50 (days) at pH 7	Value	0.2	C4	Fast
	Note	-
Aqueous hydrolysis DT50 (days) at 20oC and pH 7	Value	Stable	A5	Very persistent
	Note	Stable pH 4 to pH 9 at 25 degC over 34 days. Stable pH 4 and pH 7 at 50 degC, some hydrolysis at pH 9 and 50 degC but slow
Water-Sediment DT50 (days)		50	A5	Moderately fast
Water phase only DT50 (days)		41	A5	Stable

Soil adsorption and mobility:

Property		Value	Source/Quality Score/Other Information	Interpretation
Linear	Kd	-	-	-
	Koc	-
	Notes and range	-
Freundlich	Kf	0.959	A5	Mobile
	Kfoc	37.92
	1/n	1.08
	Notes and range	EU dossier kf range 0.018-1.9, Kfoc range 3.14-81.5 mL/g, 1/n 0.89-1.52, Soils=7
pH sensitivity		No

Key metabolites:

Metabolite		Formation Medium	Estimated Maximum Occurrence Fraction	91/414 Relevancy
diketo-metribuzin (Ref: AE 1344183)		Soil	0.097	Minor fraction, Relevant
desaminodiketometribuzin		Soil	0.167	Major fraction, Relevant

Other known metabolites:

Metabolite name and reference	Aliases	Formation Medium / Rate	Estimated Maximum Occurrence Fraction	Metabolising Enzymes
4-amino-6-(1,1-dimethylethyl)-1,2,4-triazine-5(4H)-one	desmethylthio-metribuzin	Groundwater	-	-
6-tert-butyl-4,5-dihydro-1,2,4-triazin-5-one-3-mercapturic acid	-	Groundwater	-	-
6-(1-hidroxy-1-methyl-ethyl)-3-methylsulfanyl-4H-[1,2,4]-triazine-5-one	t-BuOH-desamino-metribuzin; metribuzin metabolite M05	Rat	-	-
4-methyl-6-(1,1-dimethylethyl)-1,2,4-triazine-3,5(2H,4H)-dione	4-methyl-desamino-diketo-metribuzin; metribuzin metabolite M17	Groundwater	-	-

ECOTOXICOLOGY

Property		Value	Source/Quality Score/Other Information	Interpretation
Bio-concentration factor	BCF	10	Q3 EU dossier states low risk	Low potential
	CT50 (days)	Not available		-
Bioaccumulation potential		-	Calculated	Low
Mammals - Acute oral LD50 (mg kg-1)		32	A5 Rat	High
Mammals - Short term dietary NOEL	(mg kg-1)	2.2	A5 Rat	High
	(ppm diet)	-		-
Birds - Acute LD50 (mg kg-1)		164	A5 Colinus virginianus	Moderate
Birds - Short term dietary (LC50/LD50)		> 359 mg kg bw-1 day-1	A5 Colinus virginianus	-
Fish - Acute 96 hour LC50 (mg l-1)		74.6	A5 Oncorhynchus mykiss	Moderate
Fish - Chronic 21 day NOEC (mg l-1)		5.6	A5 Oncorhynchus mykiss, growth	-
Aquatic invertebrates - Acute 48 hour EC50 (mg l-1)		49	A5 Daphnia magna	Moderate
Aquatic invertebrates - Chronic 21 day NOEC (mg l-1)		0.32	A5 Daphnia magna	-
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)		0.008	A5 Lemna gibba	High
Algae - Acute 72 hour EC50, growth (mg l-1)		0.02	A5 Scenedemus subspicatus	Moderate
Algae - Chronic 96 hour NOEC, growth (mg l-1)		0.019	Q2 Unknown species	Moderate
Honeybees - Acute 48 hour LD50 (µg bee-1)		53	A5 Oral	Moderate
Earthworms - Acute 14 day LC50 (mg kg-1)		427	A5 Eisenia foetida	Moderate
Earthworms - Chronic 14 day NOEC, reproduction (mg kg-1)		> 5.25	A4 Eisenia foetida, 56 day	Moderate
Other soil macro-organisms - e.g. Collembola	LR50product ha EC50product ha NOECproduct ha % Effect	-	-	-
Other arthropod (1)	LR50 g ha-1	65.9	48 hour A5 Aphidius rhopalosiphi, adult	Moderately harmful at 1 kg ha-1
	% Effect	-	-	-
Other arthropod (2)	LR50 g ha-1	84	7 day A5 Typhlodromus pyri, protonymph	Moderately harmful at 1 kg ha-1
	% Effect	-	-	-
Soil micro-organisms		Nitrogen mineralisation: No significant effect Carbon mineralisation: No significant effect	A4 Dose: Not stated, 28 days	-
Mesocosm study data	NOEAEC mg l-1	-	-	-
	NOEAEC mg l-1	-	-	-

HUMAN HEALTH AND PROTECTION

General:

Property		Value	Source/Quality Score/Other Information	Interpretation
Mammals - Acute oral LD50 (mg kg-1)		32	A5 Rat	High
Mammals - Dermal LD50 (mg kg-1 body weight)		> 5000	A5 Rat	-
Mammals - Inhalation LC50 (mg l-1)		2.05	A5 Rat	-
Other Mammal toxicity endpoints		-		-
ADI - Acceptable Daily Intake (mg kg-1bw day-1)		0.013	A5 Rat, SF=100	-
ARfD - Acute Reference Dose (mg kg-1bw day-1)		0.02	A5 SF=100	-
AOEL - Acceptable Operator Exposure Level - Systemic (mg kg-1bw day-1)		0.02	A5 SF=100	-
Dermal penetration studies (%)		50.0-100.0	A5 concentration dependant	-
Dangerous Substances Directive 76/464		-	-	-
Exposure Limits		-	-	-
Exposure Routes	Public	[No unacceptable risks to bystanders identified]
	Occupational	[Minimal risk for operators using protection clothing and equipment]
Examples of European MRLs (mg kg-1)	Value	Potatoes: 0.05
	Note	[A5 EU dossier proposals] For the EU pesticides database click here
Drinking Water MAC (µg l-1)		-	-	-

Health issues:

Carcinogen	Mutagen	Endocrine disrupter	Reproduction / development effects	Acetyl cholinesterase inhibitor	Neurotoxicant	Respiratory tract irritant	Skin irritant	Eye irritant
					-		-	-
General human health issues		[Thyroid toxicant]

: Yes, known to cause a problem
: No, known not to cause a problem
: Possibly, status not identified
- : No data

Handling issues:

Property		Value	Source/Quality Score/Other Information	Interpretation
General		[Not explosive], [IMDG Transport Code is usually 9]
EC Risk Classification		[Xn - Harmful: R22], [N - Dangerous for the environment: R50, R53]
EC Safety Classification		S2, S60, S61
WHO Classification		II	-	Moderately hazardous
US EPA Classification (formulation)		III	-	Caution - Slightly toxic
UN Number		Usually 3077
Waste disposal & packaging		[Usually Packaging Group III (minor danger)]

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