| MCPA (Ref: BAS 009H) |
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GENERAL INFORMATION 
for MCPA
Description: A herbicide for control of annual and perennial weeds in cereals and other crops. Can also be a pesticide transformation product.
Example pests controlled: Annual and perennial broad-leaved weeds including Charlock, Wild radish, Dandylion, Capeweed, Fat hen and Hedge mustards
Example applications: Wheat; Oats; Tritical; Rye; Establish grass; Lindseed; Asparagus
Efficacy & activity: -
Availability status: Current
Introduction & key dates: circa 1950
EC Regulation 1107/2009 (repealing 91/414):
| Status | Approved |
| Dossier rapporteur/co-rapporteur | Poland/Netherlands |
| Date inclusion expires | 31/10/2020 |
| EU Candidate for substitution (CfS) | No |
| Listed in EU database | Yes |
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, USA
Chemical structure:
| Isomerism | None |
| Chemical formula | C9H9ClO3 |
| Canonical SMILES | CC1=C(C=CC(=C1)Cl)OCC(=O)O |
| Isomeric SMILES | No data |
| International Chemical Identifier key (InChIKey) | WHKUVVPPKQRRBV-UHFFFAOYSA-N |
| International Chemical Identifier (InChI) | InChI=1S/C9H9ClO3/c1-6-4-7(10)2-3-8(6)13-5-9(11)12/h2-4H,5H2,1H3,(H,11,12) |
| 2D structure diagram/image available? | Yes |
Cambridge Crystallographic Data Centre diagrams:
| Common Name | Relationship | Link |
| MCPA | - |  |
General status:
| Pesticide type | Herbicide, Metabolite | |
| Metabolite Type | Soil | |
| Substance group | Aryloxyalkanoic acid | |
| Minimum active substance purity | 930 mg/kg | |
| Known relevant impurities | EU dossier - None declared | |
| Substance origin | Synthetic | |
| Mode of action | Selective, systemic with translocation. Synthetic auxin. | |
| CAS RN | 94-74-6 | |
| EC number | 202-360-6 | |
| CIPAC number | 2 | |
| US EPA chemical code | 030501 | |
| PubChem CID | 7204 | |
| Molecular mass (g mol-1) | 200.62 | |
| PIN (Preferred Identification Name) | - | |
| IUPAC name | 4-chloro-o-tolyloxyacetic acid | |
| CAS name | (4-chloro-2-methylphenoxy)acetic acid | |
| Other status information | Potential groundwater contaminant | |
| Relevant Environmental Water Quality Standards | UK Environment Agency non-statutory standard for the protection of freshwater aquatic life pH <7: 12 ug/L, pH >7 80 ug/L as annual average; pH <7: 120 ug/L, pH >7 800 ug/L as max acceptable conc. For salt water 80 ug/L as annual average, 800 ug/L as max acceptable conc.] Non-statutory WHO drinking water guideline 0.002 mg/L | |
| Herbicide Resistance Classification (HRAC) | O | |
| Herbicide Resistance Classification (WSSA) | 4 | |
| Insecticide Resistance Classification (IRAC) | Not applicable | |
| Fungicide Resistance Classification (FRAC) | Not applicable | |
| Examples of recorded resistance | Raphanus raphanistrum Sisymbrium orientale |
|
| Physical state | White crystalline powder | |
| Related substances & organisms | ||
Can be a metabolite of:
| Parent | Formation medium | Estimated maximum occurrence fraction | 1107/2009 relevancy |
|
| MCPB | Soil | 0.062 | Minor fraction, Relevant | |
| MCPA-thioethyl | Soil | 0.66 | Major fraction, Relevant | |
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 | None | |||
| Formulation and application details | Often supplied as soluble concentrate, wettable powder or emulsifiable concentrate. | |||
| Property |
Value | Source/Quality Score/Other Information |
Interpretation |
|
| Solubility - In water at 20oC (mg l-1) | 29390 | A5 | High | |
| Solubility - In organic solvents at 20oC (mg l-1) | 323 | A5 - Hexane | - | |
| 289300 | A5 - Ethyl acetate | - | ||
| 775600 | A5 - Methanol | - | ||
| 26500 | A5 - Toluene | - | ||
| Melting point (oC) | 116 | A5 | - | |
| Boiling point (oC) | Decomposes before boiling | A4 | - | |
| Degradation point (oC) | 290 | A5 | - | |
| Flashpoint (oC) | Not expected to self ignite; Not highly flammable | A4 | - | |
| Octanol-water partition coefficient at pH 7, 20oC | P | 1.55 X 10-01 | Calculated | - |
| Log P | -0.81 | A5 | Low | |
| Bulk density (g ml-1)/Specific gravity | 1.41 | A5 | - | |
| Dissociation constant (pKa) at 25oC | 3.73 | A5 | - | |
| Note: Weak acid | ||||
| Vapour pressure at 20oC (mPa) | 0.4 | A5 | Low volatility | |
| Henry's law constant at 25oC (Pa m3 mol-1) | 5.50 X 10-05 | A5 | Non-volatile | |
GUS leaching potential index  |
2.94 | Calculated | High leachability | |
| SCI-GROW groundwater index (μg l-1) for a 1 kg ha-1 or 1 l ha-1 application rate |
Value | 2.39 X 10-01 | Calculated | - |
| Note | - | |||
| Potential for particle bound transport index |
- | Calculated | Low | |
| Maximum UV-vis absorption L mol-1 cm-1 | No absorption >290nm | A5 | - | |
| Surface tension (mN m-1) | - | - | - | |
Degradation:
| Property |
Value | Source/Quality Score/Other Information |
Interpretation |
General biodegradability | - |
| Soil degradation (days) (aerobic) | DT50 (typical) | 24 | A5 | Non-persistent |
| DT50 (lab at 20oC) | 24 | A5 | Non-persistent | |
| DT50 (field) | 25 | H4 | Non-persistent | |
| DT90 (lab at 20oC) | 79 | A4 @25 degC | - | |
| DT90 (field) | - | - | - | |
| DT50 modelling endpoint | - | - | - | |
| Note | EU dossier lab studies DT50 range 7-41 days | |||
| Dissipation rate RL50 on plant matrix | Value | - | - | - |
| Note | - | |||
| Dissipation rate RL50 on and in plant matrix | Value | 4.2 | R4 | - |
| Note | Published literature RL50 range 2.9-6.2 days, 5 field crops, various matrices, n=6 | |||
| Aqueous photolysis DT50 (days) at pH 7 | Value | 0.05 | A4 | Fast |
| Note | Rapid DT50 ~ 1 hour pH 5 to pH 9 at 25 degC in test conditions, DT50 25.4 days in natural sunlight pH 5 | |||
| Aqueous hydrolysis DT50 (days) at 20oC and pH 7 | Value | Stable | A5 | - |
| Note | Stable pH 5 to pH 9 at 25 degC | |||
| Water-sediment DT50 (days) | 17 | A5 | Fast | |
| Water phase only DT50 (days) | 13.5 | A5 | Moderately fast | |
Soil adsorption and mobility:
| Property |
Value | Source/Quality Score/Other Information |
Interpretation |
|
| Linear | Kd | - | - | - |
| Koc | - | |||
| Notes and range | - | |||
| Freundlich | Kf | 0.94 | A5 | Mobile |
| Kfoc | 74 | |||
| 1/n | 0.68 | |||
| Notes and range | (1) EU dossier Kf range 0.05-1.99 mL/g; Kfoc range 38-157 mL/g, 1/n range 0.50-0.72; Soils=8; (2) Mean of 2 Norweigan soils. Fine sandy loam - Sand 49% Silt 46% Clay 5% oc=1.4% pH=6.3 Kf=1.41 1/Soils=0.74; Loam - Sand 36% Silt 45% Clay 19% OC=2.5% pH=5.5 Kf=1.50 1/n=0.81 [R4] | |||
| pH sensitivity | Less adsorption as pH increases | |||
Key metabolites:
| Metabolite | Formation medium | Estimated maximum occurrence fraction | 1107/2009 relevancy |
|
| 2-methyl-4-chlorophenol | Soil | 0.09 | Minor fraction, Relevant | |
| cloxyfonac | Soil | - | - | |
| Property |
Value | Source/Quality Score/Other Information |
Interpretation |
|
| Bio-concentration factor | BCF (l kg-1) | 1 | A5 | Low potential |
| CT50 (days) | Not available | - | ||
| Mammals - Acute oral LD50 (mg kg-1) | 962 | A5 Rat | Moderate | |
| Mammals - Short term dietary NOEL | (mg kg-1) | 60 | A5 Rat | High |
| (ppm diet) | - | - | ||
| Birds - Acute LD50 (mg kg-1) | 234 | A5 Colinus virginianus | Moderate | |
| Birds - Short term dietary (LC50/LD50) | > 983 mg kg bw-1 day-1 | A5 Colinus virginianus | - | |
| Fish - Acute 96 hour LC50 (mg l-1) | > 72 | F4 Oncorhynchus mykiss | Moderate | |
| Fish - Chronic 21 day NOEC (mg l-1) | 15 | A5 Pimephales promelas | Low | |
| Aquatic invertebrates - Acute 48 hour EC50 (mg l-1) | > 190 | A5 Daphnia magna | Low | |
| Aquatic invertebrates - Chronic 21 day NOEC (mg l-1) | 50 | A5 Daphnia magna | Low | |
| 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) | 0.152 | A4 Lemna gibba, IC50 | Moderate | |
| Non-target plants | - | - | - | |
| - | - | - | ||
| Algae - Acute 72 hour EC50, growth (mg l-1) | 79.8 | A5 Pseudokirchneriella subcapitata | Low | |
| Algae - Chronic 96 hour NOEC, growth (mg l-1) | 60 | Q2 Unknown species | Low | |
| Honeybees (Apis spp.) | Contact acute LD50 (worst case from 24 , 48 and 72 hour values - μg bee-1) | > 200 | A5 Apis mellifera | Low |
| Oral acute LD50 (worst case from 24 , 48 and 72 hour values - μg bee-1) | > 200 | A5 Apis mellifera | 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) | 325 | A5 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 | 100 | Mortality Dose: 2.1 L/ha A5 Aphidius rhopalosiphi |
- | |
| Other arthropod (2) | LR50 g ha-1 | - | - | - |
| % Effect | 0 | Mortality Dose: 2.0 L/ha A5 Typhlodromus pyri |
- | |
| Soil micro-organisms | Nitrogen mineralisation: No significant adverse effect Carbon mineralisation: No significant adverse effect |
A5 Dose: 10x field rate |
- | |
| Mesocosm study data | NOEAEC mg l-1 | - | - | - |
| NOEAEC mg l-1 | - | - | - | |
HUMAN HEALTH AND PROTECTION
for MCPA
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) | 962 | A5 Rat | Moderate | |
| Mammals - Dermal LD50 (mg kg-1 body weight) | > 4000 | A5 Rat | - | |
| Mammals - Inhalation LC50 (mg l-1) | > 6.36 | A5 Rat, 4 hr | - | |
| Other Mammal toxicity endpoints | - | - | ||
| ADI - Acceptable Daily Intake (mg kg-1bw day-1) | 0.05 | A5 Rat, SF=100 | - | |
| ARfD - Acute Reference Dose (mg kg-1bw day-1) | 0.15 | A5 Rabbit, SF=100 | - | |
| AAOEL - Acute Acceptable Operator Exposure Level (mg kg-1 bw day-1) | - | - | - | |
| AOEL - Acceptable Operator Exposure Level - Systemic (mg kg-1bw day-1) | 0.04 | A5 Rat, SF=100 | - | |
| Dermal penetration studies (%) | 2.2-2.5 | A5 concentration dependent | - | |
| Dangerous Substances Directive 76/464 | List II | - | - | |
| Exposure Routes | Public | May be absorbed through the skin | ||
| Occupational | Occupational exposure may occur through inhalation and dermal contact | |||
| European MRLs | Click here for the EU MRL pesticide database | |||
| Drinking Water Standards | - | - | - | |
| Drinking Water MAC (μg l-1) | - | - | - | |
Health issues:
| Carcinogen | Genotoxic | Endocrine disrupter | Reproduction / development effects | Cholinesterase inhibitor | Neurotoxicant | |||
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A3; B0; C0; D0; E2 |
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| Respiratory tract irritant | Skin irritant | Skin sensitiser | Eye irritant | Phototoxicant | ||||
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| General human health issues | Highly toxic May cause hypotension Possible liver toxicant |
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| Key: Genotoxicity A: Chromosome aberration (EFSA database) B: DNA damage/repair (EFSA database) C: Gene mutation (EFSA database) D: Genome mutation (EFSA database) E: Unspecified genotoxicity type (miscellaneous data source) 0: No data 1: Positive 2: Mixed/ambiguous results 3: Negative |
Key: Other : Yes, known to cause a problem  : No, known not to cause a problem  : Possibly, status not identified - : No data found |
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Handling issues:
| Property |
Value | Source/Quality Score/Other Information |
Interpretation |
|
| General |
IMDG Transport Code is usually 9 | |||
| CLP classification 2013 | Health: H302, H315, H318 Environment: H400, H410 |
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| EC Risk Classification |
Xn - Harmful: R22, R41 Xi - Irritant: R38 N - Dangerous for the environment: R50, R53 |
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| EC Safety Classification |
S2, S26, S37, S39, S60, S61 | |||
| WHO Classification | II | - | Moderately hazardous | |
| UN Number | Usually 2765 or 3082 | |||
| Waste disposal & packaging |
Packaging Group III (minor danger) | |||
| Language | Name |
| English | MCPA |
| French | MCPA |
| German | MCPA |
| Danish | MCPA |
| Italian | MCPA |
| Spanish | MCPA |
| Greek | MCPA |
| Slovenian | MCPA |
| Polish | MCPA |
| Swedish | MCPA |
| Hungarian | MCPA |
| Dutch | MCPA |
Record last updated: Monday 11 November 2019
Contact: aeru@herts.ac.uk