| metribuzin (Ref: DPX G2504) |
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GENERAL INFORMATION 
for metribuzin
Description: A pre- and post-emergence herbicide used to control weeds in cereals and a range of other crops
Example pests controlled: Grasses; Broad-leaved weeds
Example applications: Soybeans; Potatoes; Barley, Wheat; Asparagus; Sugarcane; Tomatoes; Peas; Lentils
Efficacy & activity: -
Availability status: Current
Introduction & key dates: 1968, first reported; 1971, first marketed
EC Regulation 1107/2009 (repealing 91/414):
| Status | Approved |
| Dossier rapporteur/co-rapporteur | Estonia/Germany |
| Date inclusion expires | 31/07/2018 |
| EU Candidate for substitution (CfS) | Yes - two 'Persistent-Bioaccumulative-Toxic' criteria |
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 |
HR |
HU |
IE |
IT |
LT |
LU |
LV |
MT |
NL |
PL |
PT |
RO |
SE |
SI |
SK |
UK |
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Also used in: Australia
General status:
| Pesticide type | Herbicide | |
| Substance group | Triazinone | |
| Minimum active substance purity | 930 +/- 20 g/kg | |
| Known relevant impurities | EU dossier - None declared | |
| 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 | |
| Isomerism | - | |
| Chemical formula | C8H14N4OS | |
| SMILES | O=C1/C(=N\N=C(\SC)N1N)C(C)(C)C | |
| International Chemical Identifier key (InChIKey) | FOXFZRUHNHCZPX-UHFFFAOYSA-N | |
| International Chemical Identifier (InChI) | InChI=1S/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 | |
| PIN (Preferred Identification Name) | - | |
| 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 | |
| Herbicide Resistance Classification (WSSA) | 5 | |
| Insecticide Resistance Classification (IRAC) | Not applicable | |
| Fungicide Resistance Classification (FRAC) | Not applicable | |
| Examples of recorded resistance | Amaranthus hybridus | |
| Physical state | White crystalline solid | |
| Related substances & organisms | ||
Formulations:
| Property |
Value | |||
| Example manufacturers & suppliers of products using this active now or historically |
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| Example products using this active |
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| UK LERAP status | Buffer probably required in UK - see product label | |||
| Formulation and application details | Often supplied as wettable powders, liquid suspensions or water-dispersible granules. | |||
ENVIRONMENTAL FATE
for metribuzin
| 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 expected to self ignite; 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 | Low volatility | |
| Henry's law constant at 25oC (Pa m3 mol-1) | 2.00 X 10-05 | A5 | 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 |
General biodegradability | - |
| 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) | - | - | - | |
| DT50 modelling endpoint | - | - | - | |
| Note | EU dossier DT50 range 5.3-17.7 days, DT90 range 17.6-91.8 days | |||
| 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 | 0.2 | C4 | Fast |
| Note | - | |||
| Aqueous hydrolysis DT50 (days) at 20oC and pH 7 | Value | Stable | A5 | - |
| 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 | 1107/2009 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 | - | - |
| Property |
Value | Source/Quality Score/Other Information |
Interpretation |
|
| Bio-concentration factor | BCF (l kg-1) | 10 | A5 | Low potential |
| CT50 (days) | Not available | - | ||
| Mammals - Acute oral LD50 (mg kg-1) | 322 | A5 Rat | Moderate | |
| 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 | Moderate | |
| 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 | Moderate | |
| 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 | |
| Non-target plants | 15.7 | A5 Brassica napus Seedling emergence, ER50 as g/ha |
- | |
| 12.3 | A5 Brassica napus Vegetative vigour, ER50 as g/ha |
- | ||
| 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 | Contact acute 48 hour LD50 (μg bee-1) | 200 | A5 | Low |
| Oral acute 48 hour LD50 (μg bee-1) | 166 | A5 | Low | |
| Unknown mode acute 48 hour LD50 (μg bee-1) | - | - | - | |
| Earthworms - Acute 14 day LC50 (mg kg-1) | 427 | A5 Eisenia foetida | Moderate | |
| Earthworms - Chronic 14 day NOEC, reproduction (mg kg-1) | > 5.25 | A5 Eisenia foetida, 56 days | Moderate | |
| Other soil macro-organisms - e.g. Collembola | LR50 / EC50 / NOEC / % Effect | - | - | - |
| Other arthropod (1) | LR50 g ha-1 | 65.9 | 48 hour A5 Aphidius rhopalosiphi, adult |
- |
| % Effect | - | - | - | |
| Other arthropod (2) | LR50 g ha-1 | 72.9 | 7 day A5 Typhlodromus pyri, protonymph |
- |
| % Effect | - | - | - | |
| Soil micro-organisms | Nitrogen mineralisation: No significant adverse effect Carbon mineralisation: No significant adverse effect |
A4 Dose: Not stated, 28 days |
- | |
| Mesocosm study data | NOEAEC mg l-1 | - | - | - |
| NOEAEC mg l-1 | - | - | - | |
HUMAN HEALTH AND PROTECTION
for metribuzin
General:
| Property |
Value | Source/Quality Score/Other Information |
Interpretation |
|
| Threshold of Toxicological Concern (Cramer Class) |
High (class III) | - | - | |
| Mammals - Acute oral LD50 (mg kg-1) | 322 | A5 Rat | Moderate | |
| 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 dependent | - | |
| 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 | |||
| European MRLs | Click here for the EU MRL pesticide database | |||
| Drinking Water MAC (μg l-1) | - | - | - | |
Health issues:
| Carcinogen | Mutagen | Endocrine disrupter | Reproduction / development effects | Cholinesterase inhibitor | Neurotoxicant | |||
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| Respiratory tract irritant | Skin irritant | Skin sensitiser | Eye irritant | Phototoxicant | ||||
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| General human health issues | Endocrine issues - Hyperthyroidism, alteration of somatotropin levels Thyroid toxicant |
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: Yes, known to cause a problem
: No, known not to cause a problem
: Possibly, status not identified
- : No data found
Handling issues:
| Property |
Value | Source/Quality Score/Other Information |
Interpretation |
|
| General |
Not explosive IMDG Transport Code is usually 9 |
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| CLP classification 2013 | Health: H302 Environment: H400, H410 |
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| EC Risk Classification |
Xn - Harmful: R22 N - Dangerous for the environment: R50, R53 |
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| 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 |
Packaging Group III (minor danger) | |||
| Language | Name |
| English | metribuzin |
| French | metribuzine |
| German | Metribuzin |
| Danish | metribuzin |
| Italian | metribuzin |
| Spanish | metribuzina |
| Greek | metribuzin |
| Slovenian | metribuzin |
| Polish | metrybuzyna |
| Swedish | metribuzin |
| Hungarian | metribuzin |
| Dutch | metribuzine |
Record last updated: Tuesday 20 March 2018
Contact: aeru@herts.ac.uk