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Methylarsonic acid
Last updated: 19/02/2021
(Also known as: MAA; methane arsonic acid; monomethylarsonic acid ; methylarsinic acid)

GENERAL INFORMATION
Description
A largely obsolete herbicide that was used on turf to control paspalum and summer grass
Example pests controlled
Grass weeds
Example applications
Turf
Efficacy & activity
-
Availability status
Obsolete
Introduction & key dates
1994
UK regulatory status
UK COPR regulatory status
Not approved
Date COPR inclusion expires
Not applicable
UK LERAP status
No UK approval for use
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
Not applicable
EU Candidate for substitution (CfS)
Not applicable
Listed in EU database
No
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
-
Chemical formula
CH₅AsO₃
Canonical SMILES
C[As](=O)(O)O
Isomeric SMILES
No data
International Chemical Identifier key (InChIKey)
QYPPRTNMGCREIM-UHFFFAOYSA-N
International Chemical Identifier (InChI)
InChI=1S/CH5AsO3/c1-2(3,4)5/h1H3,(H2,3,4,5)
2D structure diagram/image available?
Yes
General status
Pesticide type
Herbicide
Substance group
Organometal
Minimum active substance purity
-
Known relevant impurities
-
Substance origin
Synthetic
Mode of action
Selective, contact action with some systemic properties. Readily absorbed by leaves and translocates throughout the plant
CAS RN
124-58-3
EC number
204-705-6
CIPAC number
-
US EPA chemical code
128876
PubChem CID
8948
Molecular mass
139.97
PIN (Preferred Identification Name)
-
IUPAC name
methylarsonic acid
CAS name
methylarsonic 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
White hydroscopic crystals
Formulations
Property
Value
Example manufacturers & suppliers of products using this active now or historically
  • Ansar
Example products using this active
  • Dow
  • Drexel
Formulation and application details
Usually formulated as a soluble concentrate
ENVIRONMENTAL FATE
Property
Value
Source; quality score; and other information
Interpretation
Solubility - In water at 20 °C (mg l⁻¹)
2.56E+05
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
High
Solubility - In organic solvents at 20 °C (mg l⁻¹)
- - -
Melting point (°C)
161
V3 V = ChemID online databases / IPCS INCHEM (ChemID; IPCS INCHEM )
3 = Unverified data of known source
-
Boiling point (°C)
- - -
Degradation point (°C)
- - -
Flashpoint (°C)
- - -
Octanol-water partition coefficient at pH 7, 20 °C
P
6.61 X 10-02 Calculated -
Log P
-1.18
V3 V = ChemID online databases / IPCS INCHEM (ChemID; IPCS INCHEM )
3 = Unverified data of known source
Low
Bulk density (g ml⁻¹)
- - -
Dissociation constant pKa) at 25 °C
4.1
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
-
Strong dibasic acid
Vapour pressure at 20 °C (mPa)
215.97
V3 V = ChemID online databases / IPCS INCHEM (ChemID; IPCS INCHEM )
3 = Unverified data of known source
Highly volatile
Henry's law constant at 25 °C (Pa m³ mol⁻¹)
- - -
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
- - -
Koc
-
Notes and range
-
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
- - -
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)
2833
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
Rat
Low
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)
> 425
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
Colinus virginianus
Moderate
Birds - Short term dietary (LC₅₀/LD₅₀)
- - -
Birds - Chronic 21d NOEL (mg kg⁻¹ bw d⁻¹)
- - -
Fish - Acute 96 hour LC₅₀ (mg l⁻¹)
- - -
Fish - Chronic 21 day NOEC (mg l⁻¹)
- - -
Aquatic invertebrates - Acute 48 hour EC₅₀ (mg l⁻¹)
77.5
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known 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)
- - -
Algae - Chronic 96 hour NOEC, growth (mg l⁻¹)
- - -
Honeybees (Apis spp.)
Contact acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg bee⁻¹)
68.0
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
Moderate
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)
2833
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
Rat
Low
Mammals - Dermal LD₅₀ (mg kg⁻¹ body weight)
- - -
Mammals - Inhalation LC₅₀ (mg l⁻¹)
2.2
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
Rat 4 hr
-
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
-
Occupational
-
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
Yes, known to cause a problem
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
No data found
XNo, known not to cause a problem
No data found
Respiratory tract irritant Skin irritant Skin sensitiser
Yes, known to cause a problem
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
May cause abdominal pain, diarrhoea and vomiting if ingested
Possible kidney and liver toxicant
IARC group 2B carcinogen
Handling issues
Property
Value and interpretation
General
Emits toxic and irritating fumes in a fire
CLP classification 2013
-
EC Risk Classification
T - Toxic: R23, R25
N - Dangerous for the environment: R50/53
EC Safety Classification
S1/2, S20/21, S28, S45, S60, S61
WHO Classification
III (Slightly hazardous)
UN Number
-
Waste disposal & packaging
-
TRANSLATIONS
Language
Name
English
methylarsonic acid
French
-
German
-
Danish
-
Italian
-
Spanish
-
Greek
-
Polish
-
Swedish
-
Hungarian
-
Dutch
-

Record last updated: 19/02/2021
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