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2-Methyl-4-chlorophenoxyacetic Acid

PubChem CID
7204
Structure
2-Methyl-4-chlorophenoxyacetic Acid_small.png
2-Methyl-4-chlorophenoxyacetic Acid_3D_Structure.png
2-Methyl-4-chlorophenoxyacetic Acid__Crystal_Structure.png
Molecular Formula
Synonyms
  • MCPA
  • 94-74-6
  • (4-Chloro-2-methylphenoxy)acetic acid
  • 2-METHYL-4-CHLOROPHENOXYACETIC ACID
  • Agroxone
Molecular Weight
200.62 g/mol
Computed by PubChem 2.2 (PubChem release 2021.10.14)
Dates
  • Create:
    2005-03-26
  • Modify:
    2025-01-18
Description
(4-chloro-2-methylphenoxy)acetic acid is a chlorophenoxyacetic acid that is (4-chlorophenoxy)acetic acid substituted by a methyl group at position 2. It has a role as a synthetic auxin, an environmental contaminant and a phenoxy herbicide. It is a chlorophenoxyacetic acid and a member of monochlorobenzenes.
2-methyl-4-chlorophenoxyacetic acid or MCPA is a powerful, selective, widely used phenoxy herbicide. It controls broadleaf weeds, including thistle and dock, in cereal crops and pasture. It is selective for plants with broad leaves, and this includes most deciduous trees. Clovers are tolerant at moderate application levels. It is currently classified as a restricted use pesticide in the United States.
A powerful herbicide used as a selective weed killer.
See also: MCPA-sodium (annotation moved to).

1 Structures

1.1 2D Structure

Chemical Structure Depiction
2-Methyl-4-chlorophenoxyacetic Acid.png

1.2 3D Conformer

1.3 Crystal Structures

CCDC Number
Associated Article
Crystal Structure Data
Crystal Structure Depiction
Crystal Structure Depiction

2 Names and Identifiers

2.1 Computed Descriptors

2.1.1 IUPAC Name

2-(4-chloro-2-methylphenoxy)acetic acid
Computed by Lexichem TK 2.7.0 (PubChem release 2021.10.14)

2.1.2 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)
Computed by InChI 1.0.6 (PubChem release 2021.10.14)

2.1.3 InChIKey

WHKUVVPPKQRRBV-UHFFFAOYSA-N
Computed by InChI 1.0.6 (PubChem release 2021.10.14)

2.1.4 SMILES

CC1=C(C=CC(=C1)Cl)OCC(=O)O
Computed by OEChem 2.3.0 (PubChem release 2024.12.12)

2.2 Molecular Formula

C9H9ClO3
C9H9ClO3
Computed by PubChem 2.2 (PubChem release 2021.10.14)

2.3 Other Identifiers

2.3.1 CAS

94-74-6

2.3.2 Deprecated CAS

11111-13-0, 11111-14-1, 127289-40-1, 50926-55-1, 57425-61-3
11111-14-1, 127289-40-1, 50926-55-1

2.3.3 European Community (EC) Number

2.3.4 UNII

2.3.5 UN Number

2.3.6 ChEBI ID

2.3.7 ChEMBL ID

2.3.8 DSSTox Substance ID

2.3.9 HMDB ID

2.3.10 ICSC Number

2.3.11 KEGG ID

2.3.12 Metabolomics Workbench ID

2.3.13 Nikkaji Number

2.3.14 NSC Number

2.3.15 Wikidata

2.3.16 Wikipedia

2.4 Synonyms

2.4.1 MeSH Entry Terms

  • 2 Methyl 4 chlorophenoxyacetic Acid
  • 2-Methyl-4-chlorophenoxyacetic Acid
  • Agroxone
  • MCPA
  • Methoxone

2.4.2 Depositor-Supplied Synonyms

3 Chemical and Physical Properties

3.1 Computed Properties

Property Name
Molecular Weight
Property Value
200.62 g/mol
Reference
Computed by PubChem 2.2 (PubChem release 2021.10.14)
Property Name
XLogP3
Property Value
2.6
Reference
Computed by XLogP3 3.0 (PubChem release 2021.10.14)
Property Name
Hydrogen Bond Donor Count
Property Value
1
Reference
Computed by Cactvs 3.4.8.18 (PubChem release 2021.10.14)
Property Name
Hydrogen Bond Acceptor Count
Property Value
3
Reference
Computed by Cactvs 3.4.8.18 (PubChem release 2021.10.14)
Property Name
Rotatable Bond Count
Property Value
3
Reference
Computed by Cactvs 3.4.8.18 (PubChem release 2021.10.14)
Property Name
Exact Mass
Property Value
200.0240218 Da
Reference
Computed by PubChem 2.2 (PubChem release 2021.10.14)
Property Name
Monoisotopic Mass
Property Value
200.0240218 Da
Reference
Computed by PubChem 2.2 (PubChem release 2021.10.14)
Property Name
Topological Polar Surface Area
Property Value
46.5 Ų
Reference
Computed by Cactvs 3.4.8.18 (PubChem release 2021.10.14)
Property Name
Heavy Atom Count
Property Value
13
Reference
Computed by PubChem
Property Name
Formal Charge
Property Value
0
Reference
Computed by PubChem
Property Name
Complexity
Property Value
184
Reference
Computed by Cactvs 3.4.8.18 (PubChem release 2021.10.14)
Property Name
Isotope Atom Count
Property Value
0
Reference
Computed by PubChem
Property Name
Defined Atom Stereocenter Count
Property Value
0
Reference
Computed by PubChem
Property Name
Undefined Atom Stereocenter Count
Property Value
0
Reference
Computed by PubChem
Property Name
Defined Bond Stereocenter Count
Property Value
0
Reference
Computed by PubChem
Property Name
Undefined Bond Stereocenter Count
Property Value
0
Reference
Computed by PubChem
Property Name
Covalently-Bonded Unit Count
Property Value
1
Reference
Computed by PubChem
Property Name
Compound Is Canonicalized
Property Value
Yes
Reference
Computed by PubChem (release 2021.10.14)

3.2 Experimental Properties

3.2.1 Physical Description

White solid; [Hawley] Slightly beige solid; [MSDSonline]
WHITE CRYSTALLINE POWDER WITH CHARACTERISTIC ODOUR.

3.2.2 Color / Form

White to light brown solid flakes, crystal powder or liquid.
Farm Chemicals Handbook 2000. Willoughby, Ohio: Meister 2000., p. C 245
Plates from benzene or toluene
Budavari, S. (ed.). The Merck Index - An Encyclopedia of Chemicals, Drugs, and Biologicals. Whitehouse Station, NJ: Merck and Co., Inc., 1996., p. 981
White crystalline solid (pure compd)
Lewis, R.J., Sr (Ed.). Hawley's Condensed Chemical Dictionary. 13th ed. New York, NY: John Wiley & Sons, Inc. 1997., p. 705
Colorless crystalline solid (pure)
Tomlin, C.D.S. (ed.). The Pesticide Manual - World Compendium, 11 th ed., British Crop Protection Council, Surrey, England 1997, p. 767

3.2.3 Melting Point

118-119 °C
Lewis, R.J., Sr (Ed.). Hawley's Condensed Chemical Dictionary. 13th ed. New York, NY: John Wiley & Sons, Inc. 1997., p. 705
Melting point: 115-117 °C /technical grade MCPA/
Tomlin, C.D.S. (ed.). The Pesticide Manual - World Compendium, 11 th ed., British Crop Protection Council, Surrey, England 1997, p. 767
113-119 °C

3.2.4 Solubility

Tomlin, C.D.S. (ed.). The Pesticide Manual - World Compendium, 11 th ed., British Crop Protection Council, Surrey, England 1997, p. 768
INSOL IN CARBON DISULFIDE; SOLUBILITY (G/100 ML): ETHER 77, ETHANOL 153, N-HEPTANE 0.5, TOLUENE 6.2, XYLENE 4.9
Weed Science Society of America. Herbicide Handbook. 5th ed. Champaign, Illinois: Weed Science Society of America, 1983., p. 293
Weast, R.C. (ed.). Handbook of Chemistry and Physics. 60th ed. Boca Raton, Florida: CRC Press Inc., 1979., p. C-91
Free acid insol in water but sodium and amine salts are soluble
Weiss, G.; Hazardous Chemicals Handbook. 1986, Noyes Data Corporation, Park Ridge, NJ 1986., p. 705
Sol in benzene
Lide, D.R. (ed.). CRC Handbook of Chemistry and Physics. 73rd ed. Boca Raton, FL: CRC Press Inc., 1992-1993., p. 3-386
For more Solubility (Complete) data for 2-METHYL-4-CHLOROPHENOXYACETIC ACID (6 total), please visit the HSDB record page.
Solubility in water: none

3.2.5 Density

1.56 @ 25 °C/15.5 °C
Ahrens, W.H. Herbicide Handbook of the Weed Science Society of America. 7th ed. Champaign, IL: Weed Science Society of America, 1994., p. 182
Relative density (water = 1): 1.3

3.2.6 Vapor Pressure

0.0000059 [mmHg]
5.90X10-6 mm Hg
Woodrow JE et al; pp. 61-81 in Long Range Transport of Pesticides Chelsea, MI: Lewis (1990)
Vapor pressure, Pa at 20 °C: (negligible)

3.2.7 LogP

log Kow = 3.25
Ilchmann A et al; Chem Ing Tech 65: 72-5 (1993)
2.8

3.2.8 Henry's Law Constant

Henry's Law constant= 4.8X10-10 atm-cu m/mole @ 25 °C
USDA; Agric Res Service. ARS Pesticide Properties Database on MCPA (94-74-6). Available from, as of Oct 2000: https://www.ars.usda.gov/Services/docs.htm?docid=14199

3.2.9 Stability / Shelf Life

NONVOLATILE
Spencer, E. Y. Guide to the Chemicals Used in Crop Protection. 7th ed. Publication 1093. Research Institute, Agriculture Canada, Ottawa, Canada: Information Canada, 1982., p. 361
The acid is chemically very stable.
Hartley, D. and H. Kidd (eds.). The Agrochemicals Handbook. 2nd ed. Lechworth, Herts, England: The Royal Society of Chemistry, 1987., p. A253/Aug 87
Amine salt stable indefinitely. Ester stability depends upon formulations.
Farm Chemicals Handbook 1992. Willoughby, OH: Meister Publishing Co., 1992., p. C-210

3.2.10 Decomposition

When heated to decomposition it emits toxic fumes of /hydrogen chloride and nitrogen oxides/.
Lewis, R.J. Sax's Dangerous Properties of Industrial Materials. 9th ed. Volumes 1-3. New York, NY: Van Nostrand Reinhold, 1996., p. 575
WHEN HEATED TO DECOMP, IT EMITS TOXIC FUMES OF /HYDROGEN CHLORIDE/.
Sax, N.I. Dangerous Properties of Industrial Materials. 6th ed. New York, NY: Van Nostrand Reinhold, 1984., p. 740

3.2.11 Corrosivity

Non-corrosive
Farm Chemicals Handbook 2000. Willoughby, Ohio: Meister 2000., p. C 245

3.2.12 Dissociation Constants

pKa= 3.13
Cessna AJ, Grover R; J Agric Food Chem 26: 289-92(1978)

3.2.13 Collision Cross Section

146.16 Ų [M-H]-
S61 | UJICCSLIB | Collision Cross Section (CCS) Library from UJI | DOI:10.5281/zenodo.3549476

3.2.14 Other Experimental Properties

The acid, pka 3.07, forms water sol alkali metal and amine salts, though precipitation of calcium or magnesium salts may occur with hard water.
Tomlin, C.D.S. (ed.). The Pesticide Manual - World Compendium, 11 th ed., British Crop Protection Council, Surrey, England 1997, p. 767
Solutions of the alkali metal salts are alkaline in reaction and will corrode aluminum and zinc.
Worthing, C.R. and S.B. Walker (eds.). The Pesticide Manual - A World Compendium. 8th ed. Thornton Heath, UK: The British Crop Protection Council, 1987., p. 514

3.3 SpringerMaterials Properties

3.4 Chemical Classes

3.4.1 Pesticides

Herbicides
Active substance -> EU Pesticides database: Approved
Pesticides -> Herbicides, Chlorophenoxy
Pesticide
S120 | DUSTCT2024 | Substances from Second NORMAN Collaborative Dust Trial | DOI:10.5281/zenodo.13835254

Environmental transformation -> Pesticides (parent, predecessor)

Environmental transformation -> Pesticide transformation products (metabolite, successor)

S60 | SWISSPEST19 | Swiss Pesticides and Metabolites from Kiefer et al 2019 | DOI:10.5281/zenodo.3544759
Herbicides, Transformation products
S69 | LUXPEST | Pesticide Screening List for Luxembourg | DOI:10.5281/zenodo.3862688
Pesticide (MCPA) -> USDA PDB

4 Spectral Information

4.1 1D NMR Spectra

1 of 2
1D NMR Spectra
NMR: 9679 (Sadtler Research Laboratories Spectral Collection)
2 of 2
1D NMR Spectra

4.1.1 1H NMR Spectra

1 of 3
View All
Spectra ID
Instrument Type
JEOL
Frequency
90 MHz
Solvent
CDCl3
Shifts [ppm]:Intensity
7.06:123.00, 6.58:89.00, 6.67:92.00, 6.59:54.00, 7.02:76.00, 7.14:334.00, 7.14:311.00, 7.03:79.00, 7.12:133.00, 4.67:1000.00, 6.68:129.00, 10.69:194.00, 7.13:218.00, 2.25:946.00, 7.05:122.00
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Instrument Name
BRUKER AC-300
Source of Sample
Tokyo Kasei Kogyo Company, Ltd., Tokyo, Japan
Copyright
Copyright © 1991-2024 John Wiley & Sons, Inc. All Rights Reserved.
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4.1.2 13C NMR Spectra

1 of 3
View All
Spectra ID
Instrument Type
Varian
Frequency
25.16 MHz
Solvent
CDCl3
Shifts [ppm]:Intensity
16.03:595.00, 126.54:474.00, 126.64:603.00, 65.23:836.00, 126.44:1000.00, 130.99:931.00, 174.91:784.00, 154.39:612.00, 112.36:966.00
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Source of Sample
Pfaltz & Bauer, Inc., Waterbury, Connecticut
Copyright
Copyright © 1980, 1981-2024 John Wiley & Sons, Inc. All Rights Reserved.
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4.2 Mass Spectrometry

4.2.1 GC-MS

1 of 6
View All
NIST Number
52381
Library
Main library
Total Peaks
87
m/z Top Peak
141
m/z 2nd Highest
200
m/z 3rd Highest
77
Thumbnail
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2 of 6
View All
NIST Number
362943
Library
Replicate library
Total Peaks
46
m/z Top Peak
141
m/z 2nd Highest
77
m/z 3rd Highest
200
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4.2.2 MS-MS

1 of 6
View All
Spectra ID
Ionization Mode
Negative
Top 5 Peaks
141.0114 100
Thumbnail
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2 of 6
View All
Spectra ID
Ionization Mode
Negative
Top 5 Peaks

141.0113 100

121.0294 5.48

105.0344 4.50

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4.2.3 LC-MS

1 of 47
View All
Authors
Kevin S. Jewell; Björn Ehlig; Arne Wick
Instrument
TripleTOF 6600 SCIEX
Instrument Type
LC-ESI-QTOF
MS Level
MS2
Ionization Mode
NEGATIVE
Ionization
ESI
Collision Energy
110
Fragmentation Mode
CID
Column Name
Zorbax Eclipse Plus C18 2.1 mm x 150 mm, 3.5 um, Agilent
Retention Time
10.052 min
Precursor m/z
199.0167
Precursor Adduct
[M-H]-
Top 5 Peaks
34.9676 999
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License
dl-de/by-2-0
2 of 47
View All
Authors
Kevin S. Jewell; Björn Ehlig; Arne Wick
Instrument
TripleTOF 6600 SCIEX
Instrument Type
LC-ESI-QTOF
MS Level
MS2
Ionization Mode
NEGATIVE
Ionization
ESI
Collision Energy
40
Fragmentation Mode
CID
Column Name
Zorbax Eclipse Plus C18 2.1 mm x 150 mm, 3.5 um, Agilent
Retention Time
10.052 min
Precursor m/z
199.0167
Precursor Adduct
[M-H]-
Top 5 Peaks

141.0084 999

34.9676 146

105.0307 60

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License
dl-de/by-2-0

4.3 UV Spectra

MAX ABSORPTION (AQ SOLN): 279 NM; MOLAR EXTINCTION COEFFICIENT @ THIS WAVELENGTH 1500
Kearney, P.C., and D. D. Kaufman (eds.) Herbicides: Chemistry, Degredation and Mode of Action. Volumes 1 and 2. 2nd ed. New York: Marcel Dekker, Inc., 1975., p. 9
UV: 3794 (Sadtler Research Laboratories Spectral Collection)
Weast, R.C. and M.J. Astle. CRC Handbook of Data on Organic Compounds. Volumes I and II. Boca Raton, FL: CRC Press Inc. 1985., p. V2 76

4.4 IR Spectra

IR Spectra
IR: 5667 (Sadtler Research Laboratories Prism Collection)

4.4.1 FTIR Spectra

1 of 2
Technique
KBr WAFER
Source of Sample
Amchem Products, Inc., Ambler, Pennsylvania
Copyright
Copyright © 1980, 1981-2024 John Wiley & Sons, Inc. All Rights Reserved.
Thumbnail
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2 of 2
Technique
KBr WAFER
Source of Sample
Riedel-De Haen AG
Copyright
Copyright © 1980, 1981-2024 John Wiley & Sons, Inc. All Rights Reserved.
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4.4.2 ATR-IR Spectra

Source of Sample
Aldrich
Catalog Number
261866
Copyright
Copyright © 2018-2024 Sigma-Aldrich Co. LLC. - Database Compilation Copyright © 2018-2024 John Wiley & Sons, Inc. All Rights Reserved.
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4.4.3 Vapor Phase IR Spectra

Instrument Name
DIGILAB FTS-14
Technique
Vapor Phase
Copyright
Copyright © 1980, 1981-2024 John Wiley & Sons, Inc. All Rights Reserved.
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4.5 Other Spectra

Intense mass spectral peaks: 141 m/z (100%), 200 m/z (75%), 77 m/z (63%), 143 m/z (33%)
Hites, R.A. Handbook of Mass Spectra of Environmental Contaminants. Boca Raton, FL: CRC Press Inc., 1985., p. 172
Intense mass spectral peaks: 111 m/z, 165 m/z
Pfleger, K., H. Maurer and A. Weber. Mass Spectral and GC Data of Drugs, Poisons and their Metabolites. Parts I and II. Mass Spectra Indexes. Weinheim, Federal Republic of Germany. 1985., p. 298

6 Chemical Vendors

7 Agrochemical Information

7.1 Agrochemical Category

Herbicide
Pesticide active substances -> Herbicides
Herbicides, Transformation products
S69 | LUXPEST | Pesticide Screening List for Luxembourg | DOI:10.5281/zenodo.3862688

7.2 Agrochemical Transformations

MCPA has known environmental transformation products that include 2-methyl-4-chlorophenol and cloxyfonac.

MCPA is a known environmental transformation product of MCPA-thioethyl.

S78 | SLUPESTTPS | Pesticides and TPs from SLU, Sweden | DOI:10.5281/zenodo.4687924

MCPA has known environmental transformation products that include cloxyfonac and 2-methyl-4-chlorophenol.

MCPA is a known environmental transformation product of MCPB.

S60 | SWISSPEST19 | Swiss Pesticides and Metabolites from Kiefer et al 2019 | DOI:10.5281/zenodo.3544759

7.3 EU Pesticides Data

Active Substance
mcpa
Status
Approved [Reg. (EC) No 1107/2009]
Date
Approval: 01/05/2006 Expiration: 15/08/2026
Legislation
05/57/EC, Reg. (EU) 2017/1511, Reg. (EU) 2018/1262, Reg. (EU) 2019/1589, Reg. (EU) 2021/1449, Reg. (EU) 2022/1480, Reg. (EU) 2023/1757, Reg. (EU) No 540/2011, Reg. (EU) No 762/2013, Reg. (EU)2020/1511
ADI
0.05 mg/kg bw/day [SCoFCAH July 08]
ARfD
0.15 mg/kg bw [Dir 05/57]
AOEL
0.04 mg/kg bw/day [Dir 05/57]

7.4 USDA Pesticide Data Program

8 Pharmacology and Biochemistry

8.1 MeSH Pharmacological Classification

Herbicides
Pesticides used to destroy unwanted vegetation, especially various types of weeds, grasses (POACEAE), and woody plants. Some plants develop HERBICIDE RESISTANCE. (See all compounds classified as Herbicides.)

8.2 Absorption, Distribution and Excretion

... NOT ABSORBED THROUGH SKIN TO ANY APPRECIABLE EXTENT ... . /2,4-D/
International Labour Office. Encyclopedia of Occupational Health and Safety. Volumes I and II. New York: McGraw-Hill Book Co., 1971., p. 666
(14)C MCPA ... INJECTED IV INTO PREGNANT MICE, WHICH WERE THEN STUDIED BY AUTORADIOGRAPHY AT INTERVALS OF 5 MIN TO 72 HR. DISTRIBUTION PATTERN WAS CHARACTERIZED BY HIGH CONCN IN BLOOD UP TO 4 HR & ACCUMULATION IN VISCERAL YOLK SAC EPITHELIUM UP TO 24 HR AFTER INJECTION. RADIOACTIVE SUBSTANCE PASSED THE PLACENTA, BUT FETAL TISSUES NEVER REACHED CONCN OF THE MATERNAL TISSUES. RADIOACTIVITY WAS ELIMINATED FROM FETUSES & MOTHERS BY 24 HR AFTER INJECTION.
Hayes, Wayland J., Jr. Pesticides Studied in Man. Baltimore/London: Williams and Wilkins, 1982., p. 533
WHEN ADMINISTERED TO RATS BY STOMACH TUBE, THE HIGHEST CONCENTRATIONS OF (14)C MCPA IN THE TISSUES WAS REACHED IN 2-8 HR & THEN DECLINED RAPIDLY. DURING THE FIRST 24 HOURS 92.3% OF THE DOSE WAS DISCOVERED IN URINE & 6.8% IN THE FECES.
Hayes, Wayland J., Jr. Pesticides Studied in Man. Baltimore/London: Williams and Wilkins, 1982., p. 533
ABOUT 50% OF THE TOTAL DOSE WAS DETECTED IN URINE OF 4 VOLUNTEERS WITHIN 48 HR AFTER EACH INGESTED 5 MG OF MCPA. FIVE DAYS AFTER INGESTION, THE CONCENTRATION IN THE URINE WAS BELOW THE DETECTABLE LEVEL OF 0.02 PPM.
Hayes, Wayland J., Jr. Pesticides Studied in Man. Baltimore/London: Williams and Wilkins, 1982., p. 535
For more Absorption, Distribution and Excretion (Complete) data for 2-METHYL-4-CHLOROPHENOXYACETIC ACID (8 total), please visit the HSDB record page.

8.3 Metabolism / Metabolites

YIELDS 4-CHLORO-2-HYDROXYMETHYLPHENOXYACETIC ACID & N-(4-CHLORO-2-METHYLPHENOXYACETYL)-L-ASPARTIC ACID IN RAPE & IN CAMPION. YIELDS 4-CHLORO-2-METHYLPHENOXYACETYL-BETA-D-GLUCOSE PROBABLY IN RAPE. /FROM TABLE/
Goodwin, B.L. Handbook of Intermediary Metabolism of Aromatic Compounds. New York: Wiley, 1976., p. C-32
... 2-METHYL-4-CHLOROPHENOL WAS DETECTED IN MILK OF DAIRY COWS & IN KIDNEYS OF SHEEP & CATTLE.
National Research Council. Drinking Water & Health Volume 1. Washington, DC: National Academy Press, 1977., p. 513
ARTHROBACTER SP AND FLAVOBACTERIUM PEREGRINUM DEGRADED MCPA TO 4-CHLORO-2-METHYLPHENOL. FLAVOBACTERIUM FURTHER OXIDIZED PHENOL TO RELEASE ALL CHLORIDE. ASPERGILLUS NIGER VAN TIEGH ALSO METABOLIZED MCPA TO 4-CHLORO-2-METHYL-5-HYDROXYPHENOXYACETIC ACID.
Menzie, C.M. Metabolism of Pesticides. U.S. Department of the Interior, Bureau of Sport Fisheries and Wildlife, Publication 127. Washington, DC: U.S. Government Printing Office, 1969., p. 116
... GRAM-NEGATIVE SOIL BACTERIUM METABOLIZED MCPA TO 5-CHLORO-O-CRESOL, A COMPOUND BELIEVED TO BE 6-HYDROXY-MCPA & ALPHA-METHYL-GAMMA-CARBOXYMETHYLENE-DELTA ALPHA-BUTENOLIDE.
Menzie, C.M. Metabolism of Pesticides. U.S. Department of the Interior, Bureau of Sport Fisheries and Wildlife, Publication 127. Washington, DC: U.S. Government Printing Office, 1969., p. 116
For more Metabolism/Metabolites (Complete) data for 2-METHYL-4-CHLOROPHENOXYACETIC ACID (6 total), please visit the HSDB record page.
CDDs are absorbed through oral, inhalation, and dermal routes of exposure. CDDs are carried in the plasma by serum lipids and lipoproteins, distributing mainly to the liver and adipose tissue. CDDs are very slowly metabolized by the microsomal monooxygenase system to polar metabolites that can undergo conjugation with glucuronic acid and glutathione. They may increase the rate of their own metabolism by inducing CDDs induce both phase I and phase II enzymes. The major routes of excretion of CDDs are the bile and the feces, though smaller amounts are excreted in the urine and via lactation. (L177)
L177: ATSDR - Agency for Toxic Substances and Disease Registry (1998). Toxicological profile for chlorinated dibenzo-p-dioxins (CDDs). U.S. Public Health Service in collaboration with U.S. Environmental Protection Agency (EPA). http://www.atsdr.cdc.gov/toxprofiles/tp104.html

8.4 Transformations

9 Use and Manufacturing

9.1 Uses

EPA CPDat Chemical and Product Categories
The Chemical and Products Database, a resource for exposure-relevant data on chemicals in consumer products, Scientific Data, volume 5, Article number: 180125 (2018), DOI:10.1038/sdata.2018.125
Sources/Uses
Used as a post-emergence herbicide for control of annual and perennial broad leaved weeds in cereals, herbage seed crops, flax, rice, vines, peas, potatoes, asparagus, grassland, turf, orchards, roadsides, forestry, and aquatic areas; [HSDB]
Industrial Processes with risk of exposure
Farming (Pesticides) [Category: Industry]
For 2-Methyl-4-chlorophenoxyacetic acid (USEPA/OPP Pesticide Code: 030501) ACTIVE products with label matches. /SRP: Registered for use in the U.S. but approved pesticide uses may change periodically and so federal, state and local authorities must be consulted for currently approved uses./
U.S. Environmental Protection Agency/Office of Pesticide Program's Chemical Ingredients Database on 2-Methyl-4-chlorophenoxyacetic acid (94-74-6). Available from, as of Sept 8, 2000: https://npirspublic.ceris.purdue.edu/ppis/
MCPA is used as a postemergence herbicide for control of broadleaf weeds in agricultural applications.
IARC. Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Humans. Geneva: World Health Organization, International Agency for Research on Cancer, 1972-PRESENT. (Multivolume work). Available at: https://monographs.iarc.fr/ENG/Classification/index.php, p. V30 257 (1983)
HERBICIDE FOR CONTROL OF ANNUAL & PERENNIAL WEEDS
SRI
Post-emergence control of annual and perennial broad leaved weeds (including thistles and docks) in cereals (alone or undersown), herbage seed crops, flax, rice, vines, peas, potatoes, asparagus, grassland, turf, under fruit trees, and on roadside verges and embankments. Control of broad-leaved and woody weeds in forestry. Control of aquatic broad leaved weeds.
Tomlin, C.D.S. (ed.). The Pesticide Manual - World Compendium, 11 th ed., British Crop Protection Council, Surrey, England 1997, p. 768
Dioxins occur as by-products from the manufacture of organochlorides, the bleaching of paper, chlorination by waste and drinking water treatment plants, municipal solid waste and industrial incinerators, and natural sources such as volcanoes and forest fires. (L177, L178)
L177: ATSDR - Agency for Toxic Substances and Disease Registry (1998). Toxicological profile for chlorinated dibenzo-p-dioxins (CDDs). U.S. Public Health Service in collaboration with U.S. Environmental Protection Agency (EPA). http://www.atsdr.cdc.gov/toxprofiles/tp104.html
L178: Wikipedia. Polychlorinated dibenzodioxins. Last Updated 19 May 2009. http://en.wikipedia.org/wiki/Polychlorinated_dibenzodioxins

9.1.1 Use Classification

Hazard Classes and Categories ->
Herbicides, Transformation products
S69 | LUXPEST | Pesticide Screening List for Luxembourg | DOI:10.5281/zenodo.3862688

Environmental transformation -> Pesticides (parent, predecessor)

Environmental transformation -> Pesticide transformation products (metabolite, successor)

S60 | SWISSPEST19 | Swiss Pesticides and Metabolites from Kiefer et al 2019 | DOI:10.5281/zenodo.3544759

9.2 Methods of Manufacturing

CHLORINATION OF O-CRESOL FOLLOWED BY REACTION WITH THE SODIUM SALT OF MONOCHLOROACETIC ACID
SRI
Ethylmercaptan + 2-methyl-4-chlorophenoxyacetic acid (thioesterification)
Ashford, R.D. Ashford's Dictionary of Industrial Chemicals. London, England: Wavelength Publications Ltd., 1994., p. 552

9.3 Impurities

The technical grade might contain 3-40% 6-chloro-2-methylphenoxyacetic acid. The hormone-type herbicide, commercial grade contains 4% of 4-chloro-o-cresol.
Verschueren, K. Handbook of Environmental Data on Organic Chemicals. 3rd ed. New York, NY: Van Nostrand Reinhold Co., 1996., p. 1267

9.4 Formulations / Preparations

USEPA/OPP Pesticide Code 030501; Trade Names: Mephanac; Agroxone; Bordermaster; BH MCPA; Cekherbex; chiptox; DED-Weed; empal; Hedonal M; Hormotuho; Kilsem; M 40; Phenoxylene Plus; Rhomene; Rhonox; Shamrox; Vacate; Fluid 4; weedar; Weedone; Zelan; Dikotex; Hedonal.
U.S. Environmental Protection Agency/Office of Pesticide Program's Chemical Ingredients Database on 2-Methyl-4-chlorophenoxyacetic acid (94-74-6). Available from, as of Sept 8, 2000: https://npirspublic.ceris.purdue.edu/ppis/
TECHNICAL MCPA HAS TYPICAL COMPOSITION OF: MCPA, 94-96%; 2-METHYL-6-CHLOROPHENOXYACETIC ACID, 1.5-3.0%; MIXTURE OF 2-METHYL-4,6-DICHLOROPHENOXYACETIC ACID, 2-METHYLPHENOXYACETIC ACID, 2-CHLOROPHENOXYACETIC ACID, 4-CHLOROPHENOXYACETIC ACID, & 2,6-DIMETHYL-4-CHLOROPHENOXYACETIC 0.5-1.5%; CHLORO-O-CRESOL, 0.5% & WATER, 1.0%.
National Research Council. Drinking Water & Health Volume 1. Washington, DC: National Academy Press, 1977., p. 513
MCPA IS AVAILABLE AS AMINES, ESTERS, & SODIUM OR POTASSIUM SALTS.
Weed Science Society of America. Herbicide Handbook. 5th ed. Champaign, Illinois: Weed Science Society of America, 1983., p. 293
BANVEL M IS MIXTURE OF MCPA & BANVEL. BROMINAL PLUS & BRONATE...ARE MIXTURE OF MCPA & BROMOXYNIL. PHENOXYLENE SUPER IS MIXTURE OF MCPA WITH DICAMBA. BANLENE PLUS, RAZOL DOCK PROPORTIONS.
Farm Chemicals Handbook 1981. Willoughby, Ohio: Meister, 1981., p. C-207
For more Formulations/Preparations (Complete) data for 2-METHYL-4-CHLOROPHENOXYACETIC ACID (10 total), please visit the HSDB record page.

9.5 Consumption Patterns

HERBICIDE, OF WHICH APPROXIMATELY 69% IS USED ON WHEAT, 18% ON OTHER GRAINS, & 13% ON RICE (1975)
SRI
(1992) Total pounds applied to: wheat and grains (3,445,394); barley (633,976); pasture (225,232); oats (207,439); rice (60,022); field and grass seed (51,260; flax (13,334); dry peas (7,103); rye (6,942); green peas (6,636).
USGS; Pesticide 1992 Annual Use Map on MCPA (94-74-6). Available from, as of Oct 2000: https://ca.water.usgs.gov/pnsp/use92/

9.6 U.S. Production

(1975) 1.77X10+9 GRAMS (CONSUMPTION)
SRI

9.7 General Manufacturing Information

EPA TSCA Commercial Activity Status
Acetic acid, 2-(4-chloro-2-methylphenoxy)-: ACTIVE
EPA TSCA Regulatory Flag
TP - indicates a substance that is the subject of a proposed TSCA section 4 test rule.
Avoid spray drifts onto susceptible plants such as grapes, tomatoes, & cotton.
Farm Chemicals Handbook 2000. Willoughby, Ohio: Meister 2000., p. C 245
SELECTIVE FOLIAGE BROADLEAF KILLER, SIMILAR TO 2,4-D. MORE SELECTIVE THAN 2,4-D @ EQUAL RATES ON CEREALS, LEGUMES & FLAX. APPLICATION METHODS: AERIAL & GROUND APPLICATION; LOW-VOLUME SPRAY. RATES: USED @ RATES FROM 0.12 TO 1 LB AI/ACRE. USUAL CARRIER: WATER 2 TO 30 GAL/ACRE.
Weed Science Society of America. Herbicide Handbook. 5th ed. Champaign, Illinois: Weed Science Society of America, 1983., p. 293
... Herbicide absorbed by the leaves and roots, with translocation. Concentrates in the meristematic regions, where it inhibits growth.
Ahrens, W.H. Herbicide Handbook of the Weed Science Society of America. 7th ed. Champaign, IL: Weed Science Society of America, 1994., p. 182
/MCPA/ is a systemic hormone-type selective herbicide.
Worthing, C.R. and S.B. Walker (eds.). The Pesticide Manual - A World Compendium. 8th ed. Thornton Heath, UK: The British Crop Protection Council, 1987., p. 514
For more General Manufacturing Information (Complete) data for 2-METHYL-4-CHLOROPHENOXYACETIC ACID (6 total), please visit the HSDB record page.

10 Identification

10.1 Analytic Laboratory Methods

ACTIVE INGREDIENTS ARE PRECIPITATED BY HYDROGEN CHLORIDE & EXTRACTED WITH CHLOROFORM. SOLVENT IS EVAPORATED, RESIDUE DISSOLVED IN ACETONE, & ABSORBANCE MEASURED @ CHARACTERISTIC IR WAVELENGTHS.
Association of Official Analytical Chemists. Official Methods of Analysis. 10th ed. and supplements. Washington, DC: Association of Official Analytical Chemists, 1965. New editions through 13th ed. plus supplements, 1982., p. 12/110 2.262
APPLICABLE TO DETERMINATION OF 2-METHYL-4-CHLOROPHENOXYACETIC ACID IN MUNICIPAL & INDUSTRIAL DISCHARGES BY GC USING ECD OR HALIDE DETECTOR.
PRESSLEY TA, LONGBOTTOM JE; THE DETERMINATION OF CHLORINATED HERBICIDES IN INDUSTRIAL AND MUNICIPAL WASTEWATER: METHOD 615; REPORT(EPA-600/4-82-005; PB82-155995): 24 (1982)
HPLC PROCEDURE ALLOWING DIRECT SIMULTANEOUS SEPARATION & DETECTION OF HERBICIDES USED IN RICE CULTIVATION. DETECTION LIMITS OF 0.01-0.03 PPM.
CABRAS P ET AL; J CHROMATOGR 234 (1): 249 (1982)
DETERMINATION OF THE PESTICIDES MCPA BY LOW TEMPERATURE PHOSPHORIMETRY, MINIMUM DETECTABLE AMT WAS 0.2 PPM, WITH RANGE OF O.5-50 PPM.
TRAUTWEIN NL, GUYON JC; ANAL LETT 15(A9) 811 (1982)
For more Analytic Laboratory Methods (Complete) data for 2-METHYL-4-CHLOROPHENOXYACETIC ACID (8 total), please visit the HSDB record page.

10.2 Clinical Laboratory Methods

AFTER EXPOSURE, URINE SAMPLES WERE ANALYZED BY HPLC. 0.02 UG/ML WAS BELOW DETECTABLE LEVEL.
FJELDSTAD P, WANNAG A; SCAND J WORK ENVIRON HEALTH 3 (2): 100 (1977)

11 Safety and Hazards

11.1 Hazards Identification

11.1.1 GHS Classification

1 of 6
View All
Pictogram(s)
Corrosive
Irritant
Environmental Hazard
Signal
Danger
GHS Hazard Statements

H302 (100%): Harmful if swallowed [Warning Acute toxicity, oral]

H312 (16.8%): Harmful in contact with skin [Warning Acute toxicity, dermal]

H315 (99.6%): Causes skin irritation [Warning Skin corrosion/irritation]

H318 (99.6%): Causes serious eye damage [Danger Serious eye damage/eye irritation]

H332 (16.8%): Harmful if inhaled [Warning Acute toxicity, inhalation]

H400 (98.2%): Very toxic to aquatic life [Warning Hazardous to the aquatic environment, acute hazard]

H410 (98.2%): Very toxic to aquatic life with long lasting effects [Warning Hazardous to the aquatic environment, long-term hazard]

Precautionary Statement Codes

P261, P264, P264+P265, P270, P271, P273, P280, P301+P317, P302+P352, P304+P340, P305+P354+P338, P317, P321, P330, P332+P317, P362+P364, P391, and P501

(The corresponding statement to each P-code can be found at the GHS Classification page.)

ECHA C&L Notifications Summary

Aggregated GHS information provided per 226 reports by companies from 11 notifications to the ECHA C&L Inventory. Each notification may be associated with multiple companies.

Information may vary between notifications depending on impurities, additives, and other factors. The percentage value in parenthesis indicates the notified classification ratio from companies that provide hazard codes. Only hazard codes with percentage values above 10% are shown.

11.1.2 Hazard Classes and Categories

Acute Tox. 4 (100%)

Acute Tox. 4 (16.8%)

Skin Irrit. 2 (99.6%)

Eye Dam. 1 (99.6%)

Acute Tox. 4 (16.8%)

Aquatic Acute 1 (98.2%)

Aquatic Chronic 1 (98.2%)

Acute toxicity - category 4

Skin irritation - category 2

Eye damage - category 1

Hazardous to the aquatic environment (acute) - category 1

Hazardous to the aquatic environment (chronic) - category 1

11.1.3 Fire Hazards

Not combustible. Liquid formulations containing organic solvents may be flammable. Gives off irritating or toxic fumes (or gases) in a fire. Risk of fire and explosion if formulations contain flammable/explosive solvents.

11.1.4 Hazards Summary

A skin, eye, and respiratory tract irritant; May be toxic to human reproduction or development, based on animal studies; [ICSC] May cause skin, eye, nose, and throat irritation; Effects in high dose oral studies of rats include histopathological changes to liver, kidneys, and spleen; [HSDB] Based on animal studies, not likely to cause congenital defects; No human data available; [REPROTOX] Chlorophenoxy herbicides are possibly carcinogenic to humans (Group 2B), but No adequate data were available on the carcinogenicity of MCPA. [IARC] See 2,4D.
REPROTOX - Scialli AR, Lione A, Boyle Padgett GK. Reproductive Effects of Chemical, Physical, and Biological Agents. Baltimore: The Johns Hopkins University Press, 1995.

11.1.5 Fire Potential

Nonflammable
Sax, N.I. Dangerous Properties of Industrial Materials Reports. New York: Van Nostrand Rheinhold, 1987., p. 8:6/1988

11.1.6 Skin, Eye, and Respiratory Irritations

/SRP: Irritation of skin, eyes, nose, and throat may also occur./

11.2 First Aid Measures

Inhalation First Aid
Fresh air, rest. Refer for medical attention.
Skin First Aid
Remove contaminated clothes. Rinse and then wash skin with water and soap. Refer for medical attention .
Eye First Aid
Rinse with plenty of water (remove contact lenses if easily possible). Refer immediately for medical attention.
Ingestion First Aid
Rinse mouth. Give one or two glasses of water to drink. Refer immediately for medical attention.

11.3 Fire Fighting

In case of fire in the surroundings, use appropriate extinguishing media.

11.4 Accidental Release Measures

11.4.1 Spillage Disposal

Personal protection: filter respirator for organic gases and particulates adapted to the airborne concentration of the substance. Do NOT let this chemical enter the environment. Sweep spilled substance into sealable containers. If appropriate, moisten first to prevent dusting. Carefully collect remainder. Then store and dispose of according to local regulations.

11.4.2 Disposal Methods

SRP: At the time of review, criteria for land treatment or burial (sanitary landfill) disposal practices are subject to significant revision. Prior to implementing land disposal of waste residue (including waste sludge), consult with environmental regulatory agencies for guidance on acceptable disposal practices.
Incineration: Liquids should be atomized into an incinerator equipped with an appropriate effluent gas cleaning device, and combustion maybe improved by mixing with a more flammable solvent (acetone or benzene). Solids should be combined with paper or other flammable material. An alternate procedure is to dissolve the solid in a flammable solvent and spray the solutions into the fire chamber.
United Nations. Treatment and Disposal Methods for Waste Chemicals (IRPTC File). Data Profile Series No. 5. Geneva, Switzerland: United Nations Environmental Programme, Dec. 1985., p. 69

11.4.3 Preventive Measures

SRP: The scientific literature for the use of contact lenses in industry is conflicting. The benefit or detrimental effects of wearing contact lenses depend not only upon the substance, but also on factors including the form of the substance, characteristics and duration of the exposure, the uses of other eye protection equipment, and the hygiene of the lenses. However, there may be individual substances whose irritating or corrosive properties are such that the wearing of contact lenses would be harmful to the eye. In those specific cases, contact lenses should not be worn. In any event, the usual eye protection equipment should be worn even when contact lenses are in place.

11.5 Handling and Storage

11.5.1 Safe Storage

Provision to contain effluent from fire extinguishing. Separated from strong bases and food and feedstuffs. Store in an area without drain or sewer access. Cool.

11.5.2 Storage Conditions

Keep in well-ventilated area.
Sax, N.I. Dangerous Properties of Industrial Materials Reports. New York: Van Nostrand Rheinhold, 1987., p. 8:6/1988
Do not transport or store near fertilizers, seeds, insecticides, or fungicides.
Farm Chemicals Handbook 1992. Willoughby, OH: Meister Publishing Co., 1992., p. C-210

11.6 Exposure Control and Personal Protection

11.6.1 Inhalation Risk

Evaporation at 20 °C is negligible; a harmful concentration of airborne particles can, however, be reached quickly on spraying or when dispersed, especially if powdered.

11.6.2 Effects of Short Term Exposure

The substance is irritating to the skin and respiratory tract. The substance is corrosive to the eyes. The substance may cause effects on the nervous system and heart when ingested in large amounts.

11.6.3 Allowable Tolerances

Tolerances are established for residues of the herbicide 2-methyl-4-chlorophenoxyacetic acid from application of the herbicide in the acid form or in the form of its sodium, ethanolamine, diethanolamine, triethanolamine, isopropanolamine, diisopropanolamine, triisopropanolamine, or dimethylamine salts or its isooctyl or butoxyethyl esters in or on raw agricultural commodities as follows: alfalfa, 0.1 ppm; alfalfa, hay, 0.1 ppm; barley, grain, 0.1 ppm (N); barley, straw, 2 ppm; clovers, 0.1 ppm; clover, hay, 0.1 ppm; flax, straw, 2 ppm; flaxseed, 0.1 ppm (N); grasses, pasture, 300 ppm; grasses, rangeland, 300 ppm; grass, canary, annual, seed, 0.1 ppm; grass, canary, annual, straw, 0.1 ppm; grass, hay, 20 ppm; lespedeza, 0.1 ppm; lespedeza, hay, 0.1 ppm; oats, forage, 20 ppm; oats, grain, 0.1 ppm; oats, straw, 2 ppm; peas, 0.1 ppm (N); peavines, 0.1 ppm (N); peavines, hay, 0.1 ppm (N); rice, grain, 0.1 ppm (N); rice, straw, 2 ppm; rye, forage, 20 ppm; rye, grain, 0.1 ppm (N); rye, straw, 2 ppm; sorghum, fodder, 20 ppm; sorghum, forage, 20 ppm; sorghum, grain, 0.1 ppm; trefoils, 0.1 ppm; trefoil, hay, 0.1 ppm; vegetables, seed and pod, 0.1 ppm; vetches, 0.1 ppm; vetch, hay, 0.1 ppm; wheat, forage, 20 ppm; wheat, grain, 0.1 ppm (N); wheat, straw, 2 ppm.
40 CFR 180.339(a) (4/1/2000)
Tolerances are established for combined negligible residues (N) of the herbicide 2-methyl-4-chlorophenoxyacetic acid and its metabolite 2-methyl-4-chlorophenol in or on the following raw agicultural commodities: cattle, fat, 0.1 ppm (N); cattle, mbyp, 0.1 ppm (N); cattle, meat, 0.1 ppm (N); goats, fat, 0.1 ppm (N); goats, mbyp, 0.1 ppm (N); goats, meat, 0.1 ppm (N); hogs, fat, 0.1 ppm (N); hogs, mbyp, 0.1 ppm (N); hogs, meat, 0.1 ppm (N); horses, fat, 0.1 ppm (N); horses, mbyp, 0.1 ppm (N); horses, meat, 0.1 ppm (N); milk, 0.1 ppm (N); sheep, fat, 0.1 ppm (N); sheep, mbyp, 0.1 ppm (N); and sheep, meat, 0.1 ppm (N).
40 CFR 180.339(b) (4/1/2000)

11.6.4 Personal Protective Equipment (PPE)

General handling procedure: wear rubber gloves for all handling; extinguishing method: self-contained breathing apparatus, rubber gloves, hats, suits, and boots must be worn.
Sax, N.I. Dangerous Properties of Industrial Materials Reports. New York: Van Nostrand Rheinhold, 1987., p. 8:6/1988

11.6.5 Preventions

Exposure Prevention
PREVENT DISPERSION OF DUST!
Inhalation Prevention
Use local exhaust or breathing protection.
Skin Prevention
Protective gloves. Protective clothing.
Eye Prevention
Wear safety goggles or eye protection in combination with breathing protection if powder.
Ingestion Prevention
Do not eat, drink, or smoke during work. Wash hands before eating.

11.7 Stability and Reactivity

11.7.1 Hazardous Reactivities and Incompatibilities

Reacts with alkalis to form salts
Farm Chemicals Handbook 1992. Willoughby, OH: Meister Publishing Co., 1992., p. C-210

11.8 Transport Information

11.8.1 Packaging and Labelling

Do not transport with food and feedstuffs.

11.8.2 EC Classification

Symbol: Xn, N; R: 22-38-41-50/53; S: (2)-26-37-39-60-61

11.8.3 UN Classification

UN Hazard Class: 9; UN Pack Group: III

11.9 Regulatory Information

Status Regulation (EC)
05/57/EC, Reg. (EU) 2017/1511, Reg. (EU) 2018/1262, Reg. (EU) 2019/1589, Reg. (EU) 2021/1449, Reg. (EU) 2022/1480, Reg. (EU) 2023/1757, Reg. (EU) No 540/2011, Reg. (EU) No 762/2013, Reg. (EU)2020/1511
New Zealand EPA Inventory of Chemical Status
MCPA: HSNO Approval: HSR003327 Approved with controls

11.9.1 Federal Drinking Water Guidelines

EPA 30 ug/L
USEPA/Office of Water; Federal-State Toxicology and Risk Analysis Committee (FSTRAC). Summary of State and Federal Drinking Water Standards and Guidelines (11/93) To Present

11.9.2 State Drinking Water Guidelines

(FL) FLORIDA 1,000 ug/l
USEPA/Office of Water; Federal-State Toxicology and Risk Analysis Committee (FSTRAC). Summary of State and Federal Drinking Water Standards and Guidelines (11/93) To Present
(ME) MAINE 4 ug/l
USEPA/Office of Water; Federal-State Toxicology and Risk Analysis Committee (FSTRAC). Summary of State and Federal Drinking Water Standards and Guidelines (11/93) To Present
(MN) MINNESOTA 3 ug/l
USEPA/Office of Water; Federal-State Toxicology and Risk Analysis Committee (FSTRAC). Summary of State and Federal Drinking Water Standards and Guidelines (11/93) To Present

11.9.3 FIFRA Requirements

Tolerances are established for residues of the herbicide 2-methyl-4-chlorophenoxyacetic acid from application of the herbicide in the acid form or in the form of its sodium, ethanolamine, diethanolamine, triethanolamine, isopropanolamine, diisopropanolamine, triisopropanolamine, or dimethylamine salts or its isooctyl or butoxyethyl esters in or on raw agricultural commodities as follows: alfalfa; alfalfa, hay; barley, grain; barley, straw; clovers; clover, hay; flax, straw; flaxseed; grasses, pasture; grasses, rangeland; grass, canary, annual, seed; grass, canary, annual, straw; grass, hay; lespedeza; lespedeza, hay; oats, forage; oats, grain; oats, straw; peas; peavines; peavines, hay; rice, grain; rice, straw; rye, forage; rye, grain; rye, straw; sorghum, fodder; sorghum, forage; sorghum, grain; trefoils; trefoil, hay; vegetables, seed and pod; vetches; vetch, hay; wheat, forage; wheat, grain; wheat, straw.
40 CFR 180.339(a) (4/1/2000)
Tolerances are established for combined negligible residues (N) of the herbicide 2-methyl-4-chlorophenoxyacetic acid and its metabolite 2-methyl-4-chlorophenol in or on the following raw agicultural commodities: cattle, fat; cattle, mbyp; cattle, meat; goats, fat; goats, mbyp; goats, meat; hogs, fat; hogs, mbyp; hogs, meat; horses, fat; horses, mbyp; horses, meat; milk; sheep, fat; sheep, mbyp; and sheep, meat.
40 CFR 180.339(b) (4/1/2000)
As the federal pesticide law FIFRA directs, EPA is conducting a comprehensive review of older pesticides to consider their health and environmental effects and make decisions about their future use. Under this pesticide reregistration program, EPA examines health and safety data for pesticide active ingredients initially registered before November 1, 1984, and determines whether they are eligible for reregistration. In addition, all pesticides must meet the new safety standard of the Food Quality Protection Act of 1996. 2-methyl-4-chlorophenoxyacetic acid is found on List A, which contains most food use pesticides and consists of the 194 chemical cases (or 350 individual active ingredients) for which EPA issued registration standards prior to FIFRA, as amended in 1988. Case No: 0017; Pesticide type: Herbicide; Registration Standard Date: 09/12/89; Case Status: OPP is reviewing data from the pesticide's producers regarding its human health and/or environmental effects, or OPP is determining the pesticide's eligibility for reregistration and developing the Reregistration Eligibility Decision (RED) document.; Active ingredient (AI): 2-methyl-4-chlorophenoxyacetic acid; Data Call-in (DCI) Date(s): 05/12/93, 04/06/94, 03/03/95, 10/13/95; AI Status: The producers of the pesticide has made commitments to conduct the studies and pay the fees required for reregistration, and are meeting those commitments in a timely manner.
USEPA/OPP; Status of Pesticides in Registration, Reregistration and Special Review p.126 (Spring, 1998) EPA 738-R-98-002

11.10 Other Safety Information

Chemical Assessment

IMAP assessments - Acetic acid, (4-chloro-2-methylphenoxy)-: Environment tier I assessment

IMAP assessments - Acetic acid, (4-chloro-2-methylphenoxy)-: Human health tier I assessment

11.10.1 Special Reports

EXTENSIVE ACUTE & CHRONIC TOXICITY DATA FOR MCPA IN MAMMALS, BIRDS, WILDLIFE, AQUATIC ORGANISMS, AMPHIBIANS, INSECTS & NEMATODES ARE PRESENTED.[BOVEY RW; TOXICOLOGY OF PHENOXY HERBICIDES IN ANIMALS AND MAN - GENERAL CONSIDERATIONS; IN: THE SCIENCE OF 2,4,5-T AND ASSOCIATED HERBICIDES. (JOHN WILEY & SONS: NY); CHO4: 71 (1980)]

12 Toxicity

12.1 Toxicological Information

12.1.1 Toxicity Summary

CDDs cause their toxic effects by binding to the aryl hydrocarbon receptor and subsequently altering the trascription of certain genes. The affinity for the Ah receptor depends on the structure of the specific CDD. The change in gene expression may result from the direct interaction of the Ah receptor and its heterodimer-forming partner, the aryl hydrocarbon receptor nuclear translocator, with gene regulatory elements or the initiation of a phosphorylation/dephosphorylation cascade that subsequently activates other transcription factors. The affected genes include several oncogenes, growth factors, receptors, hormones, and drug-metabolizing enzymes. The change in transcription/translation of these genes is believed to be the cause of most of the toxic effects of CDDs. This includes 2,3,7,8-tetrachlorodibenzo-p-dioxin's carcinogenicity is thought to be the result of its ability to alter the capacity of both exogenous and endogenous substances to damage the DNA by inducing CYP1A1- and CYP1A2-dependent drug-metabolizing enzymes. (L177)
L177: ATSDR - Agency for Toxic Substances and Disease Registry (1998). Toxicological profile for chlorinated dibenzo-p-dioxins (CDDs). U.S. Public Health Service in collaboration with U.S. Environmental Protection Agency (EPA). http://www.atsdr.cdc.gov/toxprofiles/tp104.html

12.1.2 EPA IRIS Information

Toxicity Summary
EPA IRIS Summary PDF (Update: Aug-28-1987 )
Critical Effect Systems

Hepatic

Urinary

Reference Dose (RfD), chronic
5 x 10 ^-4 mg/kg-day

12.1.3 RAIS Toxicity Values

Oral Chronic Reference Dose (RfDoc) (mg/kg-day)
0.0005
Oral Chronic Reference Dose Reference
IRIS Current
Oral Subchronic Chronic Reference Dose (RfDos) (mg/kg-day)
0.0005
Oral Subchronic Chronic Reference Dose Reference
HEAST Current

12.1.4 USGS Health-Based Screening Levels for Evaluating Water-Quality

Chemical
MCPA
USGS Parameter Code
68641
Chemical Classes
Pesticide
Noncancer HBSL (Health-Based Screening Level)[μg/L]
300
Reference
Smith, C.D. and Nowell, L.H., 2024. Health-Based Screening Levels for evaluating water-quality data (3rd ed.). DOI:10.5066/F71C1TWP

12.1.5 Evidence for Carcinogenicity

Cancer Classification: Not Likely to be Carcinogenic to Humans
USEPA Office of Pesticide Programs, Health Effects Division, Science Information Management Branch: "Chemicals Evaluated for Carcinogenic Potential" (April 2006)

12.1.6 Carcinogen Classification

Carcinogen Classification
2B, possibly carcinogenic to humans. (L135)

12.1.7 Health Effects

Exposure to large amounts of CDDs causes chloracne, a severe skin disease with acne-like lesions that occur mainly on the face and upper body. CDDs may also cause liver damage and induce long-term alterations in glucose metabolism and subtle changes in hormonal levels. In addition, studies have shown that CDDs may disrupt the endocrine system and weaken the immune system, as well as cause reproductive damage and birth defects, central and peripheral nervous system pathology, thyroid disorders, endometriosis, and diabetes. 2,3,7,8-Tetrachlorodibenzo-p-dioxin is also a known human carcinogen. (L177, L178)
L177: ATSDR - Agency for Toxic Substances and Disease Registry (1998). Toxicological profile for chlorinated dibenzo-p-dioxins (CDDs). U.S. Public Health Service in collaboration with U.S. Environmental Protection Agency (EPA). http://www.atsdr.cdc.gov/toxprofiles/tp104.html
L178: Wikipedia. Polychlorinated dibenzodioxins. Last Updated 19 May 2009. http://en.wikipedia.org/wiki/Polychlorinated_dibenzodioxins

12.1.8 Exposure Routes

The substance can be absorbed into the body by inhalation of its aerosol, through the skin and by ingestion.

12.1.9 Symptoms

Inhalation Exposure
Cough. Sore throat. Headache. Nausea.
Skin Exposure
Redness. Pain.
Eye Exposure
Redness. Pain. Burns. Blurred vision.
Ingestion Exposure
Burning sensation in the throat and chest. Abdominal pain. Nausea. Diarrhoea. Unconsciousness. Vomiting. Weakness. Shock or collapse.
In addition to chloracne, CDD exposure causes skin rashes, discoloration, and excessive body hair. (L177)
L177: ATSDR - Agency for Toxic Substances and Disease Registry (1998). Toxicological profile for chlorinated dibenzo-p-dioxins (CDDs). U.S. Public Health Service in collaboration with U.S. Environmental Protection Agency (EPA). http://www.atsdr.cdc.gov/toxprofiles/tp104.html

12.1.10 Target Organs

Hepatic

Urinary

12.1.11 Adverse Effects

Occupational hepatotoxin - Secondary hepatotoxins: the potential for toxic effect in the occupational setting is based on cases of poisoning by human ingestion or animal experimentation.

12.1.12 Acute Effects

12.1.13 Toxicity Data

LC50 (rat) = 1,370 mg/m3/4h

12.1.14 Treatment

Treatment may include washing any areas of contact, GI decontamination if swallowed, administering an IV and forced alkaline diuresis. (L346)
L346: US Environmental Protection Agency (2009). Recognition and Management of Pesticide Poisonings. http://www.epa.gov/oppfead1/safety/healthcare/handbook/handbook.htm

12.1.15 Interactions

Probenecid increased the acute toxicity of chlorophenoxyacetic acids (2,4-D, 2,4,5-T and MCPA) in rats. Probenecid increased the brain to plasma ratios of all the three (14)C labelled chlorophenoxyacetic acids. The increase was due only partly to the displacement of chlorophenoxyacids from their binding sites in rat plasma proteins by probenecid. Probenecid did not change significantly the intracerebral distribution pattern of (14)C labelled chlorophenoxyacetic acids.
Ylitalo P et al; Gen Pharmacol 21 (5): 811-4 (1990)

12.1.16 Antidote and Emergency Treatment

Treatment is symptomatic and supportive. Oils should not be used as either cathartics or dermal cleansing agents, as they increase absorption. Gastric lavage and use of activated charcoal and sodium sulfate are indicated for ingestion. If dermal exposure occurred, contaminated clothes should be removed, and the skin should be thoroughly cleansed with soap and water. Management of seizures in both children and adults is with Valium or phenobarbital. Respiratory depression and even respiratory arrest especially with concomitant use of Valium and phenobarbital in children, may occur. These drugs preferably should be used only in critical care areas where emergency endotracheal intubation can be performed. ... Epinephrine can not be utilized in patients with organochlorine poisoning, as the organochlorines induce myocardial irritability and ventricular arrhythmias may occur. However, dopamine may be necessary in the event of hypotension unresponsive to fluid administration, and epinephrin may be necessary in the event of cardiopulmonary arrest. ... In a critically ill patient with unknown insecticide exposure, ... Atropine must be used with caution, as it can cause ventricular irritability, especially when a myocardial irritant such as an organochlorine is present. ... Hematologic, hepatic (especially with endrin, which is markedly hepatotoxic), and renal studies as well as cardiopulmonary monitoring should be carried out in acute intoxication from lindane or other organochlorines for at least 48 to 72 hr. Long term hematologic follow-up is necessary for the patient with lindane intoxication. As the carrier for these agents may be xylene or a petroleum distillate, management also must include observation and treatment for these entities. /Organochlorine pesticides/
Haddad, L.M., Clinical Management of Poisoning and Drug Overdose. 2nd ed. Philadelphia, PA: W.B. Saunders Co., 1990., p. 1084
Bath and shampoo with soap and water to remove chemicals from skin and hair. Obtain medical treatment if irritation persists. Individuals with chronic skin disease or known sensitivity to these herbicides should either avoid using them or take strict precautions to avoid contact (respirator, gloves, etc). FLUSH contaminating chemicals from eyes and copious amounts of clean water for 10-15 minutes. If irritation persists, obtain medical treatment. /Chlorophenoxy compounds/
Morgan DP; Recognition and Management of Pesticide Poisonings. 4th ed. p.66 EPA540/9-88-001. Washington, DC: U.S. Government Printing Office, March 1989
If any symptoms of illness occur during or following inhalation of spray, remove victim from contact with the material for at least 2-3 days. Allow subsequent contact with chlorophenoxy compounds only if effective respiratory protection is practiced. /Chlorophenoxy compounds/
Morgan DP; Recognition and Management of Pesticide Poisonings. 4th ed. p.66 EPA 540/9-88-001. Washington, DC: U.S. Government Printing Office, March 1989
If substantial amounts of chlorophenoxy compounds have been ingested, spontaneous emesis may occur. If vigorous emesis has not occurred, measures should be taken to empty the stomach and limit GI absorption by gastric intubation, aspiration, and lavage, following placement of a cuffed endotracheal tube. Repeated administration of charcoal at half or more the original dosage every 2-4 hr may be beneficial. If gastric aspiration and lavage is not performed due to delay in treatment, and if the patient is fully alert, administer charcoal and laxative orally. Administer iv fluids to accelerate excretion of the chlorophenoxy compound, and to limit concentration of the toxicant in the kidney. A urine flow of 4-6 ml/min is desirable. Iv saline/dextrose has sufficed to rescue comatose patients who drank 2,4-D and mecoprop several hr before hospital admission. Caution: Monitor urine protein and cells, BUN, serum creatinine, serum electrolytes, and fluid intake/output carefully to insure that renal function remains unimpaired and that fluid overload dose not occur. Forced alkaline diuresis has been used successfully in management of suicidal ingestions of chlorophenoxy compounds. Alkalinizing the urine by including sodium bicarbonate (44-88 mEq per liter) in the iv solution apparently accelerates excretion of 2,4-D dramatically and mecoprop excretion substantially. Urine pH should be maintained in the 7.5-8.8 range. Include potassium chloride as needed to offset increased potassium losses: add 20-40 mEq of potassium chloride to each liter of iv solution. Monitor serum electrolytes carefully. There may possible be some hazard to the kidneys when urine concentrations of toxicant are very high, so integrity of renal function and fluid balance should be monitored carefully as the chlorophenoxy compound is excreted. Hemodialysis is not likely to be of significant benefit in poisonings by chlorophenoxy compounds because of the extensive protein binding of these chemicals. Follow up clinical examination should include electromyographic and nerve conduction studies to detect any neuropathic changes and neuromuscular junction defects. /Chlorophenoxy compounds/
Morgan DP; Recognition and Management of Pesticide Poisonings. 4th ed. p.66-67 EPA 540/9-88-001. Washington, DC: U.S. Government Printing Office, March 1989

12.1.17 Human Toxicity Excerpts

SYMPTOMATOLOGY: 1. FATIGUE, WEAKNESS, ANOREXIA; PERHAPS NAUSEA, VOMITING & DIARRHEA. 2. LETHARGY PROGRESSING TO COMA, WITH CONSTRICTED PUPILS (MIOSIS). 3. FLACCID PARALYSIS ... DESCRIBED IN ONE COMATOSE PATIENT & GRAND MAL CONVULSIONS WITH OPISTHOTONUS IN ANOTHER. /2,4-D/
Gosselin, R.E., R.P. Smith, H.C. Hodge. Clinical Toxicology of Commercial Products. 5th ed. Baltimore: Williams and Wilkins, 1984., p. III-133
SYMPTOMATOLOGY: 7. PROGRESSIVE HYPOTENSION WITH DEATH IN PERIPHERAL VASCULAR COLLAPSE, PERHAPS ASSOC WITH ACIDOSIS DUE TO LACTIC ACIDEMIA & OTHER PRODUCTS OF HYPERMETABOLISM. 8. IN NONFATAL POISONING SEVERE & PROTRACTED.../PRC: NEUROPATHY/ WITH PAIN & PARESTHESIAS ... MUSCLE FASCICULATIONS. 8. CHRONIC EXPOSURE MAY LEAD TO CNS DEFECTS IN CONTROL OF MOTOR FUNCTION. /2,4-D/
Gosselin, R.E., R.P. Smith, H.C. Hodge. Clinical Toxicology of Commercial Products. 5th ed. Baltimore: Williams and Wilkins, 1984., p. III-133
SYMPTOMATOLOGY: 5. PROGRESSIVE DECLINE IN BLOOD PRESSURE WITH DEATH IN DEEP COMA. ... 6. DISTURBANCES IN BODY TEMP REGULATION MAY BE ENCOUNTERED. ... SEVERE REDUCTION OF BODY TEMP IN COOL OR COLD ENVIRONMENTS. MORE PROBABLY FEBRILE RESPONSES IN WARM ENVIRONMENTS OR DURING EXERCISE. /2,4-D/
Gosselin, R.E., R.P. Smith, H.C. Hodge. Clinical Toxicology of Commercial Products. 5th ed. Baltimore: Williams and Wilkins, 1984., p. III-133
... A 61 YR OLD MAN DRANK MCPA ... SHORTLY AFTERWARD, HE VOMITED, HIS SPEECH BECAME SLURRED, HIS FACE BEGAN TO TWITCH, & HIS LIMBS BEGAN TO JERK. ON ARRIVAL AT HOSPITAL, HE WAS DEEPLY UNCONSCIOUS, ALTHOUGH IT WAS ONLY 1.5 HOURS SINCE HE HAD BEEN ASYMPTOMATIC. ... PUPILS WERE CONSTRICTED & ... /DID NOT RESPOND TO LIGHT/. REFLEXES WERE DIMINISHED. THERE WAS GENERALIZED FIBRILLARY TWITCHING OF SKELETAL MUSCLE & CLONIC SPASMS OF LIMBS. ... IN ADDITION TO CNS ABNORMALITIES, & IRRITATION OF UPPER GI TRACT, EVIDENCE OF KIDNEY & LIVER INJURY WERE OBSERVED,AS WELL AS ANEMIA & PNEUMONIA. PROTEINURIA WAS PRESENT DURING 1ST TWO WEEKS. AFTER 1 WK, GLYCOSURIA ... APPEARED & GRADUALLY SUBSIDED ... .
Hayes, Wayland J., Jr. Pesticides Studied in Man. Baltimore/London: Williams and Wilkins, 1982., p. 534
For more Human Toxicity Excerpts (Complete) data for 2-METHYL-4-CHLOROPHENOXYACETIC ACID (10 total), please visit the HSDB record page.

12.1.18 Non-Human Toxicity Excerpts

FEMALE MICE FED TECHNICAL MCPA @ 5, 25, & 100 MG/KG/DAY ON DAYS 6-15 OF GESTATION. LITTER & MEAN PUP WT WERE REDUCED @ 100 MG/KG/DAY, BUT NO MAJOR MALFORMATIONS ... OBSERVED.
National Research Council. Drinking Water & Health Volume 1. Washington, DC: National Academy Press, 1977., p. 516
IN 90 DAY FEEDING STUDY OF MCPA IN RATS, GROWTH RETARDATION & INCR KIDNEY: BODY WT RATIOS ... OBSERVED @ 400 PPM OR MORE. IN ANOTHER 90-DAY FEEDING STUDY IN CHARLES RIVER RATS, SIGNIFICANT GROWTH DECREASE WAS OBSERVED WITH TECHNICAL MCPA AT 100 PPM, & HISTOPATHOLOGIC ALTERATIONS OF LIVER & KIDNEYS WERE SEEN IN BOTH SEXES AT 25 PPM OR HIGHER.
National Research Council. Drinking Water & Health Volume 1. Washington, DC: National Academy Press, 1977., p. 514
MALE SPRAGUE DAWLEY RATS WERE GIVEN 100-3000 MG/L IN DRINKING WATER OVER 9 WK PERIOD & KILLED IMMEDIATELY AFTER TREATMENT. EXPOSURE ASSOC WITH DECR WATER CONSUMPTION, DELAYED WT GAIN, & INCR IN RELATIVE WT OF LIVER, BRAIN, KIDNEYS & ADRENALS. MOST OF THESE CHANGES WERE OBSERVED AT 1000 MG/L OR HIGHER. ADDNL OBSERVATIONS WERE PARENCHYMAL CELL DEGENERATION & MODERATE & UNSPECIFIC HYPEREMIA IN LIVER, & DISAPPEARANCE OF WHITE PULP WITH MARKED LYMPHOCYTE DEPLETION IN SPLEEN.
HATTULA ML ET AL; BULL ENVIRON CONTAM TOXICOL 18 (2): 152 (1977)
DERMAL APPLICATION OF MCPA TO RABBITS CAUSED ... ERYTHEMA & LOSS OF ELASTICITY OF THE SKIN AT A WIDE RANGE OF DOSAGES. ... HIGH MORTALITY, WT LOSS, & HISTOLOGICAL CHANGES IN LIVER, KIDNEYS, SPLEEN, & THYMUS WERE CAUSED BY DAILY DERMAL APPLICATIONS AT RATES OF 1000 & 2000 MG/KG/DAY. WT LOSS OCCURRED AT 500 MG/KG/DAY.
Hayes, Wayland J., Jr. Pesticides Studied in Man. Baltimore/London: Williams and Wilkins, 1982., p. 533
For more Non-Human Toxicity Excerpts (Complete) data for 2-METHYL-4-CHLOROPHENOXYACETIC ACID (27 total), please visit the HSDB record page.

12.1.19 Non-Human Toxicity Values

LD50 Rat male oral 700 mg/kg
Hayes, Wayland J., Jr. Pesticides Studied in Man. Baltimore/London: Williams and Wilkins, 1982., p. 533
LD50 Rat oral 800 mg/kg
Hayes, Wayland J., Jr. Pesticides Studied in Man. Baltimore/London: Williams and Wilkins, 1982., p. 533
LD50 Rat male sc 500 mg/kg
Hayes, Wayland J., Jr. Pesticides Studied in Man. Baltimore/London: Williams and Wilkins, 1982., p. 533
LD50 Rat ip 300 mg/kg
Hayes, Wayland J., Jr. Pesticides Studied in Man. Baltimore/London: Williams and Wilkins, 1982., p. 533
For more Non-Human Toxicity Values (Complete) data for 2-METHYL-4-CHLOROPHENOXYACETIC ACID (10 total), please visit the HSDB record page.

12.2 Ecological Information

12.2.1 EPA Ecotoxicity

Pesticide Ecotoxicity Data from EPA

12.2.2 Ecotoxicity Values

LC50 LEPOMIS MACROCHIRUS (BLUEGILL) MORE THAN 10 MG/L/96 HR @ 24 °C, FINGERLING. STATIC BIOASSAY WITHOUT AERATION, PH 7.2-7.5, WATER HARDNESS 40-50 MG/L AS CALCIUM CARBONATE AND ALKALINITY OF 30-35 MG/L. /LIQUID CONCENTRATE 27.6%/
U.S. Department of Interior, Fish and Wildlife Service. Handbook of Acute Toxicity of Chemicals to Fish and Aquatic Invertebrates. Resource Publication No. 137. Washington, DC: U.S. Government Printing Office, 1980., p. 62
LC50 Salmo gairdneri (Rainbow trout) 232 mg/l/96 hr /Conditions of bioassay not specified/
Hartley, D. and H. Kidd (eds.). The Agrochemicals Handbook. 2nd ed. Lechworth, Herts, England: The Royal Society of Chemistry, 1987., p. A253/Aug 87
TLm Crassostrea virginica (American oyster) 3.13X10+4 ppb/14 day, larvae, static lab bioassay
Verschueren, K. Handbook of Environmental Data of Organic Chemicals. 2nd ed. New York, NY: Van Nostrand Reinhold Co., 1983., p. 841
LC50 Lepomis macrochirus (Bluegill) 1500 ug/l/48 hr /Conditions of bioassay not specified/
Verschueren, K. Handbook of Environmental Data of Organic Chemicals. 2nd ed. New York, NY: Van Nostrand Reinhold Co., 1983., p. 841

12.2.3 US EPA Regional Screening Levels for Chemical Contaminants

Resident Soil (mg/kg)
3.20e+01
Industrial Soil (mg/kg)
4.10e+02
Tapwater (ug/L)
7.50e+00
MCL (ug/L)
1.00e+01
Risk-based SSL (mg/kg)
2.00e-03
Chronic Oral Reference Dose (mg/kg-day)
5.00e-04
Volatile
Volatile
Mutagen
Mutagen
Fraction of Contaminant Absorbed in Gastrointestinal Tract
1
Fraction of Contaminant Absorbed Dermally from Soil
0.1

12.2.4 US EPA Regional Removal Management Levels for Chemical Contaminants

Resident Soil (mg/kg)
9.50e+01
Industrial Soil (mg/kg)
1.20e+03
Tapwater (ug/L)
2.30e+01
MCL (ug/L)
1.50e+01
Chronic Oral Reference Dose (mg/kg-day)
5.00e-04
Volatile
Volatile
Mutagen
Mutagen
Fraction of Contaminant Absorbed in Gastrointestinal Tract
1
Fraction of Contaminant Absorbed Dermally from Soil
0.1

12.2.5 ICSC Environmental Data

The substance is very toxic to aquatic organisms. This substance does enter the environment under normal use. Great care, however, should be taken to avoid any additional release, for example through inappropriate disposal.

12.2.6 Environmental Fate / Exposure Summary

2-Methyl-4-chlorophenoxyacetic acid's (MCPA) use as a commercial herbicide is expected to result in its direct release to the environment. If released to air, a vapor pressure of 5.90X10-6 mm Hg at 25 °C indicates MCPA will exist in both the vapor and particulate phases in the ambient atmosphere. Vapor-phase MCPA will be degraded in the atmosphere by reaction with photochemically-produced hydroxyl radicals; the half-life for this reaction in air is estimated to be 31 hours. Particulate-phase MCPA will be removed from the atmosphere by wet and dry deposition. Field studies have shown that aerial drift from spray applications can transport MCPA to nearby ponds and streams. MCPA may undergo direct photolysis in the air since it is photochemically reactive in water. If released to soil, MCPA is expected to have high mobility based upon a Koc ranging from 50 to 62. Various monitoring studies have shown that field applications of MCPA are subject to runoff (via rainfall) with subsequent transport (relatively small amounts) to streams and ponds. Volatilization from moist soil surfaces is not expected to be an important fate process based upon a Henry's Law constant of 4.80X10-10 atm-cu m/mole. The half-life of MCPA in soil ranges from <7 to 41 days with an average of approximately 2-3 weeks, with more rapid degradation occurring in acclimated soils. Biodegradation appears to be slower in drier soils and in flooded (anaerobic) soils. If released into water, MCPA is not expected to adsorb to suspended solids and sediment based upon its Koc. Biodegradation of MCPA is expected to occur in water based upon its biodegradability in soil, with more rapid degradation following acclimation. Volatilization from water surfaces is not expected to be an important fate process based upon this compound's Henry's Law constant. A BCF of 1 suggests that the potential for bioconcentration in aquatic organisms is low. Hydrolysis of MCPA is not expected to occur because of the lack of hydrolyzable functional groups. Occupational exposure to MCPA may occur through inhalation, swallowing of spray droplets, and dermal contact with this compound at workplaces where MCPA is produced or used. Monitoring and biodegradation data suggest that the general population is not expected to be exposed to MCPA. (SRC)

12.2.7 Natural Pollution Sources

MCPA is not known to occur as a natural product(1).
(1) IARC; IARC Monographs on the Evaluation of Carcinogen Risks to Humans. Lyon, France: World Health Organization 30: 255-66 (1983)

12.2.8 Artificial Pollution Sources

MCPA's use as a herbicide to control broadleaf weeds in agricultural applications(1,2) is expected to result in its direct release to the environment(SRC). Various monitoring studies have shown that field applications of MCPA are subject to runoff (via rainfall) with subsequent transport (relatively small amounts) to streams and ponds(3,4).
(1) Ahrens WH; Herbicide Handbook of the Weed Science Society of America 7th ed. Champaign, IL: Weed Sci Soc Amer p. 182 (1994)
(2) IARC; IARC Monographs on the Evaluation of Carcinogen Risks to Humans. Lyon, France: World Health Organization 30: 255-66 (1983)
(3) Frank R, Sirons GJ; Sci Total Environ 15: 149-67 (1980)
(4) Frank R et al; Bull Environ Contam Toxicol 44: 401-9 (1990)

12.2.9 Environmental Fate

TERRESTRIAL FATE: Based on a classification scheme(1), a Koc value ranging from the 50 to 62 (2), indicates that MCPA is expected to have high mobility in soil(SRC). Volatilization of MCPA from moist soil surfaces is not expected to be an important fate process(SRC) based on its Henry's Law constant of 4.80X10-10 atm-cu/mole(3). MCPA is not expected to volatilize from dry soil surfaces(SRC) based upon a vapor pressure of 5.90X10-6 mm Hg(4). The primary degradation process for MCPA in soil is biodegradation(5). A literature review of available laboratory persistence studies of MCPA in soil found soil half-lives ranging from <7 to 41 days with an average of about 2-3 weeks(6). MCPA is susceptible to photodegradation in sunlight(5,7); however, photodegradation at the soil surface is not considered a major degradation pathway since it is applied post-emergence to growing crops, and residues reaching the soil will be protected from sunlight by the crop canopy(5). Under field studies, the resultant average persistence of MCPA at recommended application rates is up to 1 month in moist conditions and up to 6 months under drier climates(8).
(1) Swann RL et al; Res Rev 85: 17-28 (1983)
(2) Helweg A; Weed Res 27: 287-96 (1987)
(3) USDA; Pesticide Properties Database on MCPA (94-74-6). Available from as of Oct, 2000: https://www.ars.usda.gov/Services/docs.htm?docid=14199
(4) Woodrow JE et al; Environ Tox Chem 1: 267-79 (1982)
(5) Smith AE, LaFond GP; pp. 14-22 in Enhanced Biodegradation of Pesticides in the Environment. ACS Symp Ser 426 (1990)
(6) Smith AE; Rev Weed Sci 4: 1-24 (1989)
(7) Soderquist CJ, Crosby DG; Pestic Sci 6: 17-33 (1975)
(8) Ahrens WH; Herbicide Handbook of the Weed Science Society of America 7th ed. Champaign, IL: Weed Sci Soc Amer p. 183 (1994)
AQUATIC FATE: Based on a classification scheme(1), a Koc value ranging from 50 to 62(2), indicates that MCPA is not expected to adsorb to suspended solids and sediment(SRC). Volatilization from water surfaces is not expected(3) based upon its Henry's Law constant of 4.80X10-10 atm-cu m/mole(4). According to a classification scheme(5), a BCF of 1(6), suggests the potential for bioconcentration in aquatic organisms is low. Based on degradation studies, it appears that MCPA will biodegrade in water but at a slower rate than in soil. In flooded sediment, the complete degradation of MCPA took 96 wks, but only 48 wks in moist soil; the ratio of relative persistence in moist soil vs. flooded sediment was determined to be 1:2.3(7). The direct photolysis half-life of MCPA in water (at surface conditions under summer sunlight) is about 19-20 days(8).
(1) Swann RL et al; Res Rev 85: 17-28 (1983)
(2) Helweg A; Weed Res 27: 287-96 (1987)
(3) Lyman WJ et al; Handbook of Chemical Property Estimation Methods. Washington, DC: Amer Chem Soc pp. 4-9, 15-1 to 15-29 (1990)
(4) USDA; Pesticide Properties Database on MCPA (94-74-6). Available from, as of Oct, 2000: https://www.ars.usda.gov/Services/docs.htm?docid=14199
(5) Franke C et al; Chemosphere 29: 1501-14 (1994)
(6) Murty AS; Tox of Pest to Fish, Vols I, II; CRC Press, FL pp. 70, 74 (1986)
(7) Marbury SA et al; pp. 71-117 in Envir Fate Rice Pest in Calif, Springer-Verlag NY, Inc (1996)
(8) Soderquist CJ, Crosby DG; Pest Sci 6: 17-33 (1975)
ATMOSPHERIC FATE: According to a model of gas/particle partitioning of semivolatile organic compounds in the atmosphere(1), MCPA, which has a vapor pressure of 5.90X10-6 mm Hg at 25 °C(2), will exist in both the vapor and particulate phases in the ambient atmosphere. Vapor-phase MCPA is degraded in the atmosphere by reaction with photochemically-produced hydroxyl radicals(SRC); the half-life for this reaction in air is estimated to be 30 hours(SRC), calculated from its rate constant of 1.3X10-11 cu cm/molecule-sec at 25 °C(SRC), determined using a structure estimation method(3). Particulate-phase MCPA may be removed from the air by wet and dry deposition(SRC). Aerial drift from herbicidal spraying operations can transport MCPA to nearby ponds and streams(4). A multi-year study of MCPA in surface water of a small prairie watershed concluded that the aqueous concns of MCPA were related to elevated precipitation and air levels rather than to runoff losses(5). MCPA may undergo direct photolysis since it is photochemically reactive in water(6). Exposure of aqueous solutions of MCPA in distilled water to Oct sunlight in Davis, CA resulted in a 14% decomposition of MCPA after 245 hr of exposure(7).
(1) Bidleman TF; Environ Sci Technol 22: 361-367 (1988)
(2) Woodrow JE et al; Environ Tox Chem 1: 267-79 (1982)
(3) Meylan WM, Howard PH; Chemosphere 26: 2293-99 (1993)
(4) Frank R, Sirons GJ; Sci Total Environ 15: 149-67 (1980)
(5) Rawn DFK et al; J Envir Qual 28: 906-917 (1999)
(6) Soderquist CJ, Crosby DG; Pest Sci 6: 17-33 (1975)
(7) Draper WM, Crosby DG; J Agric Food Chem 32: 231-7 (1984)

12.2.10 Environmental Biodegradation

AEROBIC: Microbial degradation of MCPA in soil was followed by measuring radiolabeled 14-CO2 evolution(1); in non-acclimated soil, CO2 evolution reached 40-50% after 78 days of incubation(1). At an initial MCPA concn of 5 mg/kg, CO2 evolution increased markedly after a 2-3 week lag period indicating that microbial adaptation will increase the degradation rate(1); optimum degradation occurred in soil with a moisture content of 0.6 to 1.2 field capacity(1) while degradation in dry soil was negligible(1). The importance of acclimation was demonstrated in soil degradation tests in which degradation in unacclimated soil required 46-82 days, but only 5-14.5 days were required for a subsequent degradation in the same soil(2); sterilization tests (via sodium azide) indicated that all soil degradation was microbial in nature(2). The results of laboratory studies indicated that 14C-labeled MCPA would degrade faster in soils that had received previous applications than in untreated soils(3). Microbial degradation in soil is probably due to hydroxylation with cleavage of the ether linkage (4). The dechlorination of MCPA was indicated as an acid-yielding reaction and was observed to reduce the pH in a mixed culture medium; no degradation occurred in cultures above pH 8.5 and degradation was slower at higher concns(5). In samples of sandy clay soil (pH 5.2, organic matter 6.3%) at field capacity moisture content (18.2%) and incubated at 23 °C for up to 32 weeks, MCPA, at initial concns of 10, 100, 200 and 500 ppm, degraded more rapidly at the lower concns(6). Respective losses of 40%, 60% and 90% were observed at 2, 8 and 32 weeks; the degradates were identified as 4-chloro-o-cresol, 5-chloro-3-methylcatechol, and 2,6-dimethoxyphenol(6).
(1) Helweg A; Weed Res 27: 287-96 (1987)
(2) Audus LJ; Plant Soil 3: 170-92 (1951)
(3) Smith AE et al; J Environ Qual 18: 299-302 (1989)
(4) Ahrens WH; Herbicide Handbook of the Weed Science Society of America 7th ed. Champaign, IL: Weed Sci Soc Amer p. 182 (1994)
(5) Oh KH et al; Bull Envir Contam Toxic 55: 539-545 (1995)
(6) Sattar MA; Bull Environ Contam Toxicol 28: 348 (1982)
ANAEROBIC: MCPA was reported to be rapidly degraded (actual rates not reported) in a laboratory scale semi-continuous anaerobic sludge digester(1). However, using a primary digester sludge as inoculum and a serum bottle technique, MCPA was found to be resistent (lag period > 75 days) to anaerobic degradation(2). Using a soil inoculum, (14)CO2 evolution half-lives of 32-48 days were measured(3). Using non-adapted seawater and marine sediment as inoculum, 14-CO2 evolutions of 0.1-0.9% were measured over a 24 hr incubation period(4). In flooded sediment, the complete degradation of MCPA took 96 wks, but only 48 wks in moist soil; the ratio of relative persistence in moist soil vs. flooded sediment was determined to be 1:2.3 (5). In a model ecosystem which was built to model anaerobic (sulfate-reducing) conditions in an aquifer, MCPA was relatively persistent, with only a slight decrease in concn observed; the decrease was attributed mainly to adsorption (6). In a field study conducted in a limestone aquifer and in a laboratory microcosm study, MCPA did not degrade under anaerobic conditions (7).
(1) Buisson RSK et al; Arch Environ Contam Toxicol 19: 428-32 (1990)
(2) Battersby NS, Wilson V; Appl Environ Microbiol 55: 433-9 (1989)
(3) Soulas G et al; Chemosphere 12: 1101-6 (1983)
(4) Ursin C; Chemosphere 14: 1539-50 (1985)
(5) Marbury SA et al; pp. 71-117 in Envir Fate Rice Pest in Calif, NY, NY: Springer-Verlag (1996)
(6) Kuhlmann B, Kaczmarzcyk B; Envir Toxic Water Qual: Intl J 10:119-125 (1995)
(7) Harrison I et al; Chemosphere 36:1211-1232 (1998)
In soil, metabolism involves degradation of the side-chain to 4-chloro-2-methylphenol, ring hydroxylation, and ring opening(1). Duration of residual activity in soil is approximately 3-4 months (1). Soil moisture was found to be an important biodegradation factor as the degradation rate in air-dried soils was less than 30% after 579 days of incubation(2); no degradation occurred at temperatures ranging from -30 to 0 °C (2). Field studies indicate that MCPA dissipates from soil plots with half-lives ranging from 6 to 60 days (3). In one field study, the initial MCPA half-life was approximately 29 days when using a soil that had no previous MCPA applications(4); in soil that had received 1-18 years of previous exposures, the half-life was approximately 10 days(4). Duration of residual activity in soil is approximately 3 to 4 months, following an application rate of 3 kg/ha(1). MCPA has also been observed to degrade in subsoils (5).
(1) Tomlin CDS, ed; The Pesticide Manual World Compendium. 11th ed., Surrey, England: British Crop Protection Council. p. 769 (1997)
(2) Sattar MA; Agric Ecosyst Environ 10: 75-9 (1983)
(3) Kearney PC et al; Res Rev 29: 137-49 (1969)
(4) USDA; Pesticide Properties Database on MCPA (94-74-6). Available from the Database Query page at https://www.arsusda.gov/acsl/services/ppdb/ppdb3.html as of Oct, 2000.
(5) Torstensson L; Ecol Bull (Stockholm) 27: 263-84 (1978)
(6) Anderson JPE; Fate of Pest in Subsurf Soils and Groundwater, Amer Chem Soc (1995)

12.2.11 Environmental Abiotic Degradation

The rate constant for the vapor-phase reaction of MCPA with photochemically-produced hydroxyl radicals has been estimated as 1.3X10-11 cu cm/molecule-sec at 25 °C(SRC) using a structure estimation method(1). This corresponds to an atmospheric half-life of about 30 hours at an atmospheric concentration of 5X10+5 hydroxyl radicals per cu cm(1). MCPA is not expected to undergo hydrolysis in the environment due to the lack of hydrolyzable functional groups(2). Photolysis, however, is expected to be an important degradation process. When exposed to summer sunlight or photoreactors simulating sunlight, aqueous solutions of MCPA (buffered to pHs 8-10) photolyzed to 50% of initial MCPA concn in approximately 19-20 days(3). The major photolysis product has been observed as 4-chloro-2-methylphenol, with o-cresol and 4-chloro-2-formylphenol also identified as photolysis products(3,4). The exposure of MCPA in sterilized rice paddy water to sunlight resulted in a 50% MCPA decrease in about 8-9 days, suggesting a possible photosensitized transformation(3). Exposure of aqueous solutions of MCPA in distilled water to Oct sunlight (Davis, CA) resulted in a 14% decomposition of MCPA after 245 hr of exposure(5). The photolysis of MCPA can be sensitized by the formation of sunlight-produced hydroxyl radicals(5) and by photo-oxidants generated by humates(6). Sensitization may increase the photodegradation rate by up to an order of magnitude or more(5,6); the photosensitized rate will vary among natural waters and will depend upon the availability of photocatalytic agents. 4-Chloro-2-methylphenol was identified as the major photolysis product when aqueous MCPA solutions were exposed to simulated sunlight(7); riboflavine and anthraquinone were found to photosensitize MCPA photodegradation(7).
(1) Meylan WM, Howard PH; Chemosphere 26: 2293-99 (1993)
(2) Lyman WJ et al; Handbook of Chemical Property Estimation Methods. Washington, DC: Amer Chem Soc pp. 7-4, 7-5 (1990)
(3) Soderquist CJ, Crosby DG; Pestic Sci 6: 17-33 (1975)
(4) Menzie; Metab Pesticides, p. 92 (1978)
(5) Draper WM, Crosby DG; J Agric Food Chem 32: 231-7 (1984)
(6) Stangroom et al; Wat Res 32:623-632 (1998)
(7) Clapes P et al; Chemosphere 15: 395-401 (1986)

12.2.12 Environmental Bioconcentration

A BCF of 1 was determined for trout at MCPA aqueous concns of 10-100 mg/l and using an exposure period of 10-28 day(1). In a model aquatic ecosystem study, BCFs of <1 were measured in fish and snails for the sodium salt of 2-methyl-4-chlorophenoxyacetic acid(2,3). According to a classification scheme(3), these BCF values suggest the potential for bioconcentration in aquatic organisms is low. MCPA is absorbed through leaves or roots and is readily translocated in plants(4).
(1) Murty AS; Tox of Pest to Fish, Vols I, II; CRC Press, FL pp. 70, 74 (1986)
(2) Virtanen M et al; Chemosphere 7: 431-42 (1979)
(3) Franke C et al; Chemosphere 29: 1501-14 (1994)
(4) Ahrens WH; Herbicide Handbook of the Weed Science Society of America 7th ed. Champaign, IL: Weed Sci Soc Amer p. 182 (1994)

12.2.13 Soil Adsorption / Mobility

MCPA adsorption coefficients (Kd) of 0.7 to 1.0 were measured in three soils (loamy sand and sandy loam types)(1); based upon humus contents of 2.4-3.0%(1),the Koc values of the three soils are approximately 60, 52 and 50, respectively. A similar Kd value of 0.4 was observed in a garden soil(2). Using soil thin-layer chromatography, Rf values of 0.6-1.0 were measured for Chillum silt loam (3.1% organic matter), Lakeland sand loam (0.9% organic matter) and Hagerstown silty clay loam (1.4% organic matter)(3,4); these Rf values classify MCPA as mobile in soil(3,4). When MCPA was applied to a rice field, an observed 70% decrease in MCPA was attributed to losses through soil percolation(5). In a laboratory study of leaching columns with either turf grass soil or two subsoils, most of the applied MCPA (95.4-99.0%) eluted with the first 100-ml fraction of leaching water applied to the columns, indicating that MCPA did not bind to the soils(6). According to a classification scheme(7), these Koc values suggest that MCPA is expected to have high mobility in soil.
(1) Helweg A; Weed Res 27: 287-96 (1987)
(2) Audus LJ; Plant Soil 3: 170-92 (1951)
(3) Helling CS, Turner BC; Science 162: 562-3 (1968)
(4) Helling CS; Soil Sci Soc Amer, Proc 35: 737-43 (1971)
(5) Menzie CM; Metab of Pest, Update II, US DOI Special Sci Rep - Wildlife No. 212, p. 92 (1978)
(6) Suzuki T et al; Environ Sci Technol 32: 920-929 (1998)
(7) Swann RL et al; Res Rev 85: 17-28 (1983)

12.2.14 Volatilization from Water / Soil

The Henry's Law constant for MCPA is 4.80X10-10 atm-cu m/mole(1). This Henry's Law constant indicates that MCPA is expected to be essentially nonvolatile from moist soil and water surfaces(2). MCPA is not expected to volatilize from dry soil surfaces(SRC) based upon a vapor pressure of 5.90X10-6 mm Hg(3). In a volatilization experiment, however, 90% of MCPA applied to polyethylene surfaces volatilized after 3 days of open exposure to air(4). It should be kept in mind, however, that a polyethylene surface is much different than water or soil in the environment. On soil surfaces, MCPA will likely leach or be taken up by plants fairly rapidly(5,6).
(1) USDA; Pesticide Properties Database on MCPA (94-74-6). Available from, as of Oct, 2000: https://www.ars.usda.gov/Services/docs.htm?docid=14199
(2) Lyman WJ et al; Handbook of Chemical Property Estimation Methods. Washington, DC: Amer Chem Soc pp. 15-1 to 15-29 (1990)
(3) Woodrow JE et al; pp. 61-81 in Long Range Transport of Pesticides Chelsea, MI: Lewis (1990)
(4) Seiber JN et al; Chemosphere 15: 127-38 (1986)
(5) Ahrens WH; Herbicide Handbook of the Weed Science Society of America 7th ed. Champaign, IL: Weed Sci Soc Amer p. 182 (1994)
(6) Helweg A; Weed Res 27: 287-96 (1987)

12.2.15 Environmental Water Concentrations

GROUNDWATER: MCPA was detected in 2 of 237 wells in Ontario, Canada, monitored between 1969 and 1978 at concns of 1.1-10 ppb in one well and 1001-10000 ppb in the other(1); the high concns were the result of spillage(1). During monitoring of 359 Ontario wells between 1979 and 1984, MCPA was detected only twice(2); the detections were the result of spillage(2). In a monitoring study of the Anglican Water region in the United Kingdom (an agricultural area), MCPA was detected in (detection limit of 0.1 ug/l) 0.5% of all samples at concns of 0.12 ug/l(3). MCPA was detected in 0.1% of 725 wells sampled in Minnesota at a levels of 0.33 ug/l(4). MCPA was detected in 2 of 14 wells of a shallow aquifer in 1993, during May and July, and in 1 of 14 wells in June of 1994 in central South Dakota; MCPA was not detected in the 14 wells in 4 of the 6 study years(5).
(1) Frank R et al; Pestic Monit J 13: 120-7 (1979)
(2) Frank R et al; Arch Environ Contam Toxicol 16: 9-22 (1987)
(3) Croll BT; J Inst Water Environ Manage 5: 389-95 (1991)
(4) Hallberg GR; Agric Ecosys Environ 26: 299-367 (1989)
(5) Bhatt K; Environ Monitoring Assess 47:223-237 (1997)
SURFACE WATER: In a study conducted between 1975 and 1977, MCPA was detected (detection limit of 0.1 ug/l) in 6 of 949 stream water samples collected from 11 agricultural watersheds in Ontario, Canada(1); positive samples coincided with spraying operations(1). Levels of <0.1 to 1.7 ug/l were detected into 2 of 98 water samples collected from 8 agricultural watersheds in Ontario in 1974(2). Water samples were collected at the mouths of the Grand, Saugeen and Thames Rivers in Ontario between Jan 1981 and Dec 1985(3); MCPA was detected in 1 of 100 Grand River samples (0.1 ug/l), 4 of 200 Thames River samples (1.8 ug/l mean concn), and no Saugeen samples(3). In a monitoring study of the Anglican Water region in the United Kingdom (an agricultural area), MCPA was detected in 1% of all samples at concns of <0.1 to 16.9 ug/l (detection limit not specified)(4). In a study of water and sediment of Lake Miedwie in Poland, MCPA was detected in 86 of 88 surface water samples in both 1984 and 1985, ranging from 0.05-1.32 ug/kg and 0.03-0.61 ug/kg, respectively(5).
(1) Frank R, Sirons GJ; Sci Total Environ 15: 149-67 (1980)
(2) Frank R et al; Pestic Monit J 13: 120-7 (1979)
(3) Frank R, Logan L; Arch Environ Contam Toxicol 17: 741-54 (1988)
(4) Croll BT; J Inst Water Environ Manage 5: 389-95 (1991)
(5) Beitz H et al; pp. 49 in Chem of Plant Protection Vol 9 (1994)
RAIN/SNOW/FOG: In rain and roof water collected at Gruze, Switzerland, MCPA was detected in 4 of 41 samples, generally in early April through early May, at concns up to 27 ng/l; the total annual load (excluding Nov to Jan) was 800 ng/sq m-yr (1). In a 1993-1996 study of ambient air (vapor plus particulate phases) and precipitation in an agricultural area in southern Manitoba, Canada, MCPA was detected (detection limit 10 pg/l) in precipitation at maximum concns during late May and early June, corresponding with annual local use patterns; similar temporal concn profiles were observed in each of the 4 years(2).
(1) Bucheli T et al; Environ Sci Technol 32: 3457-3464 (1998)
(2) Rawn DFK et al; J Environ Qual 28: 898-906 (1999)

12.2.16 Effluent Concentrations

2-Methyl-4-chlorophenoxyacetic acid was detected in one of 5 leachates collected from 5 sanitary landfills in Denmark during Feb 1983(1); the concn of the positive sample was 1-10 ppm(1).
(1) Schultz B, Kjeldsen P; Water Res 20: 965-70 (1986)

12.2.17 Sediment / Soil Concentrations

In a study conducted between 1975 and 1977, MCPA was not detected in sediment samples collected from streams in 11 agricultural watersheds in Ontario, Canada(1). MCPA residues of 8-52 ppm have been reported for sediments collected from Canadian estuaries(2). In a study of water and sediment of Lake Miedwie in Poland, MCPA was detected in 45 of 60 sediment samples in 1984, at 0.3-24.0 ug/kg, and in 53 of 62 sediment samples in 1985, at 2.0-15.5 ug/kg (3).
(1) Frank R, Sirons GJ; Sci Total Environ 15: 149-67 (1980)
(2) Reish DJ et al; J Water Pollut Control Fed 55: 767-87 (1983)
(3) Beitz H et al; pp. 49 in Chem of Plant Protection Vol 9 (1994)

12.2.18 Atmospheric Concentrations

URBAN/SUBURBAN: In a study of urban (indoor and outdoor) air samples collected from 14 cities in the US and Canada, MCPA was not detected (detection limit 0.001 mg/cu m) in any of 25 applicator breathing zone samples(1).
(1) Yeary RA, Leonard JA; pp. 275-281 in Pestic in Urban Environ - ACS Symp SER 522 (1993)
INDOOR: In a study of urban (indoor and outdoor) air samples collected from 14 cities in the US and Canada, MCPA was not detected (detection limit 0.001 mg/cu m) in any of the samples collected in the offices, operations rooms or warehouses of three facilities (1).
(1) Yeary RA, Leonard JA; pp. 275-281 in Pestic in Urban Environ - ACS Symp SER 522 (1993)
RURAL/REMOTE: In a study of vapor-phase and suspended particulate samples from a primarily agricultural area in rural North Dakota, MCPA (detection limit 0.3 pg/cu m) was detected in the air on 1 of 6 sampling dates in 1993, at 70 pg/cu m; and was detected on 4 of 7 sampling dates in 1994, at 2.1-12 pg/cu m(1). In a 1993-1996 study of ambient air (vapor plus particulate phases) and precipitation in an agricultural area in southern Manitoba, Canada, MCPA was detected (detection limit 2.1 pg/cu m) in the air at concns up to 13 ng/cu m and ranging from nondetectable to 13,000 pg/cu m; MCPA was mainly found in the vapor phase, with the exception of the maximum detection(2).
(1) Hawthorne SB et al; J Environ Qual 25:594-600 (1996)
(2) Rawn DFK et al; J Environ Qual 28:898-906 (1999)

12.2.19 Food Survey Values

No 2-methyl-4-chlorophenoxyacetic acid (MCPA) residues were detected in any food composites collected from July 1, 1969 to June 30, 1976 as part of the FDA's (Food and Drug Administration) Total Diet Study (market basket survey of ready-to-eat US foods)(1). In earlier Total Diet Study analyses (June 1964 to Apr 1969), MCPA was detected in 11 of 1236 food composite samples at levels ranging from a trace to 0.40 ppm(2-5).
(1) Duggan RE et al; Pesticide Residue Levels in Foods in the United States form July 1, 1969 to June 30, 1976. Washington DC: Food and Drug Admin (1983)
(2) Duggan RE et al; Pestic Monit J 1: 2-12 (1967)
(3) Duggan RE et al; Sci 151: 101-4 (1966)
(4) Corneliussen PE; Pestic Monit L 2: 140-52 (1969)
(5) Corneliussen PE; Pestic Monit J 4: 89-105 (1970)

12.2.20 Milk Concentrations

... 2-METHYL-4-CHLOROPHENOL WAS DETECTED IN MILK OF DAIRY COWS ... .
National Research Council. Drinking Water & Health Volume 1. Washington, DC: National Academy Press, 1977., p. 513

12.2.21 Probable Routes of Human Exposure

The production and formulation of 2-methyl-4-chlorophenoxyacetic acid (and its derivatives) and their use in agricultural applications are potential sources of exposure to both workers and the general population(1). Occupational exposure to 2-methyl-4-chlorophenoxyacetic acid occurs through dermal contact and inhalation of dust and sprays, especially to workers applying the compound as a herbicide(2). In one monitoring study of farmers and spraymen, dermal absorption seemed to be the dominant route of entrance(3); swallowing of spray droplets and inhalation were also possible routes of entrance(3).
(1) IARC; IARC Monographs on the Evaluation of Carcinogen Risks to Humans. Lyon, France: World Health Organization 30: 255-66 (1983)
(2) Parmeggiani L; Encyl Occup Health & Safety 3rd ed. Geneva, Switzerland: International Labour Office p. 1616-46 (1983)
(3) Kolmodin-Hedman B et al; Arch Toxicol 54: 257-65 (1983)
Air exposure to 2-methyl-4-chlorophenoxyacetic acid was determined by monitoring 24 farmers and 9 professional spraymen who were spray applying the herbicide(1); air samples were collected in the individual breathing zones during preparation and spraying(1); median concns ranged from 0.004 to 0.015 mg/cu m TWA(1); the highest concn was 0.092 mg/cu m TWA(1).
(1) Kolmodin-Hedman B et al; Arch Toxicol 54: 257-65 (1983)
Occupational exposure to MCPA may occur through inhalation and dermal contact with this compound at workplaces where MCPA is produced or used(SRC). Air exposure to MCPA was determined by monitoring 24 farmers and 9 professional spraymen who were spray applying the herbicide(1); air samples were collected in the individual breathing zones during preparation and spraying(1); median concns ranged from 0.004 to 0.015 mg/cu m TWA(1); the highest concn was 0.092 mg/cu m TWA(1).
(1) Kolmodin-Hedman B et al; Arch Toxicol 54: 257-65 (1983)

12.2.22 Body Burden

2-Methyl-4-chlorophenoxyacetic acid residues were measured in 18 urine samples collected from workers who had been spray applying the herbicide less than 24 hr previous(1); concns of 10-50 ppb were found in 8 samples, concns of 50-150 ppb were found in 5 samples, and concns of 150-500 ppb were found in 5 samples(1). In another monitoring study of farmers and professional spraymen, median urine concns of 0.31-1.7 ug/ml were detected(2).
(1) De Felip E et al; Ecotox Environ Safety 16: 170-5 (1988)
(2) Kolmodin-Hedman B et al; Arch Toxicol 54: 257-65 (1983)
IN A SUICIDE, SPECIMENS TAKEN AT AUTOPSY CONTAINED THE FOLLOWING CONCENTRATIONS OF MCPA: BLOOD, 230 PPM; LIVER, 146 PPM; HEART, 154 PPM; & BRAIN, 32.8 PPM. IN ANOTHER CASE, THE CONCENTRATIONS IN AUTOPSY SPECIMENS OF BLOOD & URINE WERE 180 & 800 PPM, RESPECTIVELY.
Hayes, Wayland J., Jr. Pesticides Studied in Man. Baltimore/London: Williams and Wilkins, 1982., p. 535

13 Literature

13.1 Consolidated References

13.2 NLM Curated PubMed Citations

13.3 Springer Nature References

13.4 Wiley References

13.5 Chemical Co-Occurrences in Literature

13.6 Chemical-Gene Co-Occurrences in Literature

13.7 Chemical-Disease Co-Occurrences in Literature

14 Patents

14.1 Depositor-Supplied Patent Identifiers

14.2 WIPO PATENTSCOPE

14.3 Chemical Co-Occurrences in Patents

14.4 Chemical-Disease Co-Occurrences in Patents

14.5 Chemical-Gene Co-Occurrences in Patents

15 Interactions and Pathways

15.1 Chemical-Target Interactions

16 Biological Test Results

16.1 BioAssay Results

17 Classification

17.1 MeSH Tree

17.2 ChEBI Ontology

17.3 KEGG: Pesticides

17.4 ChemIDplus

17.5 CAMEO Chemicals

17.6 ChEMBL Target Tree

17.7 UN GHS Classification

17.8 EPA CPDat Classification

17.9 NORMAN Suspect List Exchange Classification

17.10 EPA DSSTox Classification

17.11 EPA TSCA and CDR Classification

17.12 EPA Substance Registry Services Tree

17.13 MolGenie Organic Chemistry Ontology

18 Information Sources

  1. Australian Industrial Chemicals Introduction Scheme (AICIS)
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    EPA TSCA Classification
    https://www.epa.gov/tsca-inventory
  6. EPA DSSTox
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    https://comptox.epa.gov/dashboard/DTXSID4024195
    CompTox Chemicals Dashboard Chemical Lists
    https://comptox.epa.gov/dashboard/chemical-lists/
  7. EPA Integrated Risk Information System (IRIS)
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  10. Hazardous Substances Data Bank (HSDB)
    2-METHYL-4-CHLOROPHENOXYACETIC ACID
    https://pubchem.ncbi.nlm.nih.gov/source/hsdb/1127
  11. ILO-WHO International Chemical Safety Cards (ICSCs)
  12. New Zealand Environmental Protection Authority (EPA)
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  22. EU Pesticides Database
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    https://creativecommons.org/licenses/by/4.0/
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    https://www.norman-network.com/nds/SLE/
  24. EPA Regional Screening Levels for Chemical Contaminants at Superfund Sites
  25. USDA Pesticide Data Program
  26. USGS Health-Based Screening Levels for Evaluating Water-Quality Data
  27. Hazardous Chemical Information System (HCIS), Safe Work Australia
  28. NITE-CMC
    (4-chloro-2-methylphenoxy)acetic acid - FY2006 (New/original classication)
    https://www.chem-info.nite.go.jp/chem/english/ghs/06-imcg-0381e.html
    (4-Chloro-2-methylphenoxy)acetic acid - FY2021 (Revised classification)
    https://www.chem-info.nite.go.jp/chem/english/ghs/21-mhlw-2097e.html
    (4-Chloro-2-methylphenoxy)acetic acid - FY2018 (Revised classification)
    https://www.chem-info.nite.go.jp/chem/english/ghs/18-moe-2013e.html
  29. Regulation (EC) No 1272/2008 of the European Parliament and of the Council
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    MCPA (ISO); 4-chloro-o-tolyloxyacetic acid
    https://eur-lex.europa.eu/eli/reg/2008/1272/oj
  30. IUPAC Digitized pKa Dataset
    acetic acid, 2-(4-chloro-2-methylphenoxy)-
    https://github.com/IUPAC/Dissociation-Constants
  31. NMRShiftDB
  32. Human Metabolome Database (HMDB)
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    http://www.hmdb.ca/citing
    (4-Chloro-2-methylphenoxy)acetic acid
    http://www.hmdb.ca/metabolites/HMDB0254366
  33. SpectraBase
    [(4-CHLORO-o-TOLYL)OXY]ACETIC ACID
    https://spectrabase.com/spectrum/CYUGaxTk4UC
    (4-chloro-o-tolyloxy)acetic acid
    https://spectrabase.com/spectrum/6QRQsw5BFLQ
    [(4-CHLORO-o-TOLYL)OXY]ACETIC ACID
    https://spectrabase.com/spectrum/5TeUuqqahHk
    [(4-CHLORO-o-TOLYL)OXY]ACETIC ACID
    https://spectrabase.com/spectrum/KA9UOJ0ZAzY
    ACETIC ACID, /4-CHLORO-O- TOLYLOXY/-,
    https://spectrabase.com/spectrum/JPvWgkTAcvu
    4-Chloro-2-methylphenoxyacetic acid
    https://spectrabase.com/spectrum/DSiyZ7IcnWm
  34. Japan Chemical Substance Dictionary (Nikkaji)
  35. KEGG
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    https://www.kegg.jp/kegg/legal.html
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  38. Metabolomics Workbench
  39. NIST Mass Spectrometry Data Center
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    https://www.nist.gov/srd/public-law
    [(4-Chloro-o-tolyl)oxy]acetic acid
    http://www.nist.gov/srd/nist1a.cfm
  40. Springer Nature
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  42. The Cambridge Structural Database
  43. Wikidata
  44. Wikipedia
  45. Wiley
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    2-Methyl-4-chlorophenoxyacetic Acid
    https://www.ncbi.nlm.nih.gov/mesh/68008456
  47. PubChem
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  49. CAMEO Chemicals
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  50. EPA Substance Registry Services
  51. MolGenie
    MolGenie Organic Chemistry Ontology
    https://github.com/MolGenie/ontology/
  52. PATENTSCOPE (WIPO)
  53. NCBI
CONTENTS