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(4-chlorophenoxy)acetic acid
Last updated: 12/01/2021
(Also known as: (4-chlorophenoxy)acetic acid ; PCPA; 4-CPA; 4-ChFu; 4-CPA)

SUMMARY
4-CPA is a plant growth regulator that does not have approval for use in the EU. It is highly soluble in water and is quite volatile. Little is known about its persistence in soil and aquatic systems. It is moderately toxic to mammals and has a high potential for bioaccumulation. It is also a recognised irritant. It is moderately toxic to birds, honeybees and most aquatic organisms. However, it has a relatively low toxicity to fish.
GENERAL INFORMATION
Description
A plant growth regulator used fruit setting and thining
Example pests controlled
Growth - in terms of thinging and fruit set
Example applications
Tomatoes; Grapes
Efficacy & activity
-
Availability status
Current
Introduction & key dates
Current
UK regulatory status
UK COPR regulatory status
Not approved
Date COPR inclusion expires
Expired
UK LERAP status
Not applicable
EC Regulation 1107/2009 (repealing 91/414)
EC Regulation 1107/2009 status
Not approved
Dossier rapporteur/co-rapporteur
Not applicable
Date EC 1107/2009 inclusion expires
Expired
EU Candidate for substitution (CfS)
Not applicable
Listed in EU database
Yes
Approved for use (✓) under EC 1107/2009 in the following EU Member States
ATAustria
BEBelgium
BGBulgaria
CYCyprus
CZCzech Republic
DEGermany
DKDenmark
EEEstonia
ELGreece
                 
ESSpain
FIFinland
FRFrance
HRCroatia
HUHungary
IEIreland
ITItaly
LTLithuania
LULuxembourg
                 
LVLatvia
MTMalta
NLNetherlands
PLPoland
PTPortugal
RORomania
SESweden
SISlovenia
SKSlovakia
                 
Also used in
Also used in
-
Chemical structure
Isomerism
None
Chemical formula
C₈H₇ClO₃
Canonical SMILES
C1=CC(=CC=C1OCC(=O)O)Cl
Isomeric SMILES
No data
International Chemical Identifier key (InChIKey)
SODPIMGUZLOIPE-UHFFFAOYSA-N
International Chemical Identifier (InChI)
InChI=1S/C8H7ClO3/c9-6-1-3-7(4-2-6)12-5-8(10)11/h1-4H,5H2,(H,10,11)
2D structure diagram/image available?
Yes
Cambridge Crystallographic Data Centre diagrams
Common Name Relationship Link
(4-chlorophenoxy)acetic acid -
General status
Pesticide type
Plant growth regulator, Herbicide
Substance group
Auxin
Minimum active substance purity
-
Known relevant impurities
-
Substance origin
Synthetic
Mode of action
Auxin-transport inhibitor. Absorbed by tissue and translocated to roots
CAS RN
122-88-3
EC number
204-581-3
CIPAC number
291
US EPA chemical code
019401
PubChem CID
26229
Molecular mass
186.59
PIN (Preferred Identification Name)
(4-chlorophenoxy)acetic acid
IUPAC name
4-chlorophenoxyacetic acid
CAS name
(4-chlorophenoxy)acetic acid
Other status information
-
Relevant Environmental Water Quality Standards
-
Herbicide Resistance Classification (HRAC)
Not known
Herbicide Resistance Classification (WSSA)
Not known
Insecticide Resistance Classification (IRAC)
Not applicable
Fungicide Resistance Classification (FRAC)
Not applicable
Examples of recorded resistance
-
Physical state
Off-white crystalline solid
Formulations
Property
Value
Example manufacturers & suppliers of products using this active now or historically
  • Poltomat
  • Marks 4-CPA
Example products using this active
  • A. H. Marks
  • Hockley International Ltd.
Formulation and application details
Available in a range of formulations including aerosols, liquids and tablets
ENVIRONMENTAL FATE
Property
Value
Source; quality score; and other information
Interpretation
Solubility - In water at 20 °C (mg l⁻¹)
957
CA3 CA = Medical and toxicological databases and information systems e.g. TOXNET (click here )
3 = Unverified data of known source
High
Solubility - In organic solvents at 20 °C (mg l⁻¹)
- - -
Melting point (°C)
157
CA3 CA = Medical and toxicological databases and information systems e.g. TOXNET (click here )
3 = Unverified data of known source
-
Boiling point (°C)
Decomposes before boiling
V3 V = ChemID online databases / IPCS INCHEM (ChemID; IPCS INCHEM )
3 = Unverified data of known source
-
Degradation point (°C)
- - -
Flashpoint (°C)
Not expected to self ignite; Not highly flammable
V3 V = ChemID online databases / IPCS INCHEM (ChemID; IPCS INCHEM )
3 = Unverified data of known source
-
Octanol-water partition coefficient at pH 7, 20 °C
P
1.78 X 1002 Calculated -
Log P
2.25
CA3 CA = Medical and toxicological databases and information systems e.g. TOXNET (click here )
3 = Unverified data of known source
Low
Bulk density (g ml⁻¹)
1.52
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
-
Dissociation constant pKa) at 25 °C
3.01
DW4 DW = Don Wauchope personal database for Pka data: Wauchope, R. D. and Edwards, J. Dissociation constants for pesticide active ingredients: a database and comparison with predicted values. MS in preparation
4 = Verified data
-
Weak acid
Vapour pressure at 20 °C (mPa)
2.40 X 10-02
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
Low volatility
Henry's law constant at 25 °C (Pa m³ mol⁻¹)
6.48 X 10-08
CA3 CA = Medical and toxicological databases and information systems e.g. TOXNET (click here )
3 = Unverified data of known source
Non-volatile
Maximum UV-vis absorption L mol⁻¹ cm⁻¹
- - -
Surface tension (mN m⁻¹)
- - -
Degradation
Property
Value
Source; quality score; and other information
Interpretation
General biodegradability
-
Soil degradation (days) (aerobic)
DT₅₀ (typical)
- - -
DT₅₀ (lab at 20 °C)
- - -
DT₅₀ (field)
- - -
DT₉₀ (lab at 20 °C)
- - -
DT₉₀ (field)
- - -
DT₅₀ modelling endpoint
- - -
Note
-
Dissipation rate RL₅₀ on plant matrix
Value
- - -
Note
-
Dissipation rate RL₅₀ on and in plant matrix
Value
- - -
Note
-
Aqueous photolysis DT₅₀ (days) at pH 7
Value
- - -
Note
-
Aqueous hydrolysis DT₅₀ (days) at 20 °C and pH 7
Value
- - -
Note
-
Water-sediment DT₅₀ (days)
- - -
Water phase only DT₅₀ (days)
- - -
Soil adsorption and mobility
Property
Value
Source; quality score; and other information
Interpretation
Linear
Kd
-
CA2 CA = Medical and toxicological databases and information systems e.g. TOXNET (click here )
2 = Unverified data of unknown source
Mobile
Koc
18
Notes and range
Estimated
Freundlich
Kf
- - -
Kfoc
-
1/n
-
Notes and range
-
pH sensitivity
-
Fate indices
Property
Value
Source; quality score; and other information
Interpretation
GUS leaching potential index
- - -
SCI-GROW groundwater index (μg l⁻¹) for a 1 kg ha⁻¹ or 1 l ha⁻¹ application rate
Value
Cannot be calculated - -
Note
-
Potential for particle bound transport index
- - -
Potential for loss via drain flow
- - -
Other known metabolites
Metabolite name and reference
Aliases
Formation medium / Rate
Estimated maximum occurrence fraction
Metabolising enzymes
centrophenoxine - Plant - -
ECOTOXICOLOGY
Property
Value
Source; quality score; and other information
Interpretation
Bio-concentration factor
BCF (l kg⁻¹)
Low risk
Q3 Q = Miscellaneous internet resources
3 = Unverified data of known source
Based on LogP < 3
Low risk
CT₅₀ (days)
- -
Mammals - Acute oral LD₅₀ (mg kg⁻¹)
850
C4 C = AGRITOX (click here )
4 = Verified data
Rat
Moderate
Mammals - Short term dietary NOEL
(mg kg⁻¹)
- - -
(ppm diet)
- -
Mammals - Chronic 21d NOAEL (mg kg⁻¹ bw d⁻¹)
- - -
Birds - Acute LD₅₀ (mg kg⁻¹)
- - -
Birds - Short term dietary (LC₅₀/LD₅₀)
- - -
Birds - Chronic 21d NOEL (mg kg⁻¹ bw d⁻¹)
- - -
Fish - Acute 96 hour LC₅₀ (mg l⁻¹)
> 180
CA3 CA = Medical and toxicological databases and information systems e.g. TOXNET (click here )
3 = Unverified data of known source
Lepomis macrochirus
Low
Fish - Chronic 21 day NOEC (mg l⁻¹)
- - -
Aquatic invertebrates - Acute 48 hour EC₅₀ (mg l⁻¹)
> 40
Q2 Q = Miscellaneous internet resources
2 = Unverified data of unknown source
Daphnia magna
Moderate
Aquatic invertebrates - Chronic 21 day NOEC (mg l⁻¹)
- - -
Aquatic crustaceans - Acute 96 hour LC₅₀ (mg l⁻¹)
- - -
Sediment dwelling organisms - Acute 96 hour LC₅₀ (mg l⁻¹)
- - -
Sediment dwelling organisms - Chronic 28 day NOEC, static, water (mg l⁻¹)
- - -
Sediment dwelling organisms - Chronic 28 day NOEC, sediment (mg kg⁻¹)
- - -
Aquatic plants - Acute 7 day EC₅₀, biomass (mg l⁻¹)
- - -
Non-target plants
- - -
- - -
Algae - Acute 72 hour EC₅₀, growth (mg l⁻¹)
1.4
Q2 Q = Miscellaneous internet resources
2 = Unverified data of unknown source
Unknown species
Moderate
Algae - Chronic 96 hour NOEC, growth (mg l⁻¹)
1
A2 A = EU regulatory and evaluation data as published by EC, EFSA (RAR, DAR & Conclusion dossiers), EMA (e.g. EU Annex III PIC DGD) (EU - Pesticides database; EFSA Scientific Publications )
2 = Unverified data of unknown source
Unknown species
Moderate
Honeybees (Apis spp.)
Contact acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg bee⁻¹)
> 100
E3 E = Manufacturers safety data sheets
3 = Unverified data of known source
Low
Oral acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg bee⁻¹)
- - -
Unknown mode acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg bee⁻¹)
- - -
Bumblebees (Bombus spp.)
Contact acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg bee⁻¹)
- - -
-
Oral acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg bee⁻¹)
- - -
-
Mason bees (Osmia spp.)
Contact acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg bee⁻¹)
- - -
Oral acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg bee⁻¹)
- - -
Other pollinators (1)
Acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg insect⁻¹)
- - -
Mode of exposure
-
Other pollinators (2)
Acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg insect⁻¹)
- - -
Mode of exposure
-
Earthworms - Acute 14 day LC₅₀ (mg kg⁻¹)
- - -
Earthworms - Chronic NOEC, reproduction (mg kg⁻¹)
- - -
Other soil macro-organisms
Acute LC₅₀ (mg kg⁻¹)
- - -
Chronic NOEC (mg kg⁻¹)
- - -
Other arthropod (1)
LR₅₀ g ha⁻¹
- - -
% Effect
- - -
Other arthropod (2)
LR₅₀ g ha⁻¹
- - -
% Effect
- - -
Soil micro-organisms
- - -
Mesocosm study data
NOEAEC mg l⁻¹
- - -
NOEAEC mg l⁻¹
- - -
HUMAN HEALTH AND PROTECTION
General
Property
Value
Source; quality score; and other information
Interpretation
Threshold of Toxicological Concern (Cramer Class)
High (class III) - -
Mammals - Acute oral LD₅₀ (mg kg⁻¹)
850
C4 C = AGRITOX (click here )
4 = Verified data
Rat
Moderate
Mammals - Dermal LD₅₀ (mg kg⁻¹ body weight)
2200
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
Rat
-
Mammals - Inhalation LC₅₀ (mg l⁻¹)
10.6
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
Rat
-
Other Mammal toxicity endpoints
- - -
ADI - Acceptable Daily Intake (mg kg⁻¹ bw day⁻¹)
- - -
ARfD - Acute Reference Dose (mg kg⁻¹ bw day⁻¹)
- - -
AAOEL - Acute Acceptable Operator Exposure Level (mg kg⁻¹ bw day⁻¹)
- - -
AOEL - Acceptable Operator Exposure Level - Systemic (mg kg⁻¹ bw day⁻¹)
- - -
Dermal penetration studies (%)
- - -
Dangerous Substances Directive 76/464
- - -
Exposure Routes
Public
Exposure from air or water very low as it is usually used inside
Small risk of dietary exposure
Source: US EPA
Occupational
Low risk of exposure during handling
Source: US EPA
MRLs
European
EU MRL pesticide database 
Notes
-
Drinking Water Standards
- - -
Drinking Water MAC (μg l⁻¹)
- - -
Health issues
Specific human health issues
Carcinogen
Genotoxic
Endocrine disruptor
?Possibly, status not identified
A0 A = Chromosome aberration (EFSA database)
0 = No data
;
B0 B = DNA damage/repair (EFSA database)
0 = No data
;
C0 C = Gene mutation (EFSA database)
0 = No data
;
D0 D = Genome mutation (EFSA database)
0 = No data
;
E0 E = Unspecified genotoxicity type (miscellaneous data source)
0 = No data
No data found
Reproduction / development effects Acetyl cholinesterase inhibitor Neurotoxicant
?Possibly, status not identified
XNo, known not to cause a problem
XNo, known not to cause a problem
Respiratory tract irritant Skin irritant Skin sensitiser
No data found
Yes, known to cause a problem
No data found
Eye irritant Phototoxicant  
Yes, known to cause a problem
No data found  
General human health issues
Potential irritant
Potential kidney toxicant
Handling issues
Property
Value and interpretation
General
IMDG Transport Code is usually 8
CLP classification 2013
Health: H302
EC Risk Classification
Xn - Harmful: R22
EC Safety Classification
S2
WHO Classification
II (Moderately hazardous)
UN Number
Usually 3265
Waste disposal & packaging
Packaging Group III (minor danger)
TRANSLATIONS
Language
Name
English
(4-chlorophenoxy)acetic acid
French
acide 4 chlorophenoxyacetique
German
4-CPA
Danish
4-CPA
Italian
4-CPA (acido 4-clorofenossiacetico =PCPA)
Spanish
4-CPA
Greek
-
Polish
4-CPA
Swedish
-
Hungarian
4-CPA
Dutch
-

Record last updated: 12/01/2021
Contact: aeru@herts.ac.uk
Please cite as: Lewis, K.A., Tzilivakis, J., Warner, D. and Green, A. (2016) An international database for pesticide risk assessments and management. Human and Ecological Risk Assessment: An International Journal, 22(4), 1050-1064. DOI: 10.1080/10807039.2015.1133242