(Also known as: arsanote Liquid; MSMA; agent purple; monosodium methanarsonate)
SUMMARY
Monosodium methylarsonate is a herbicide that is not widely approved for use in the developed world due to its toxicity. As well as being highly toxic it is also a known skin, eye and inhalation irritant. It is highly soluble in water and considered to be persistent in soils. Monosodium methylarsonate is moderately toxic to fish, algae and honeybees and slightly less toxic to birds.
Data alerts
The following alerts are based on the data in the tables below. An absence of an alert does not imply the substance has no implications for human health, biodiversity or the environment but just that we do not have the data to form a judgement.
Example manufacturers & suppliers of products using this active now or historically
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Example products using this active
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Formulation and application details
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ENVIRONMENTAL FATE
Property
Value
Source; quality score; and other information
Interpretation
Solubility - In water at 20 °C (mg l⁻¹)
580000
Q3 Q = Miscellaneous data from online sources 3 = Unverified data of known source
High
Solubility - In organic solvents at 20 °C (mg l⁻¹)
-
-
-
Melting point (°C)
-
V3 V = ChemID Online Databases; Chemspider; PubChem. (ChemID ) 3 = Unverified data of known source
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Boiling point (°C)
-
-
-
Degradation point (°C)
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-
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Flashpoint (°C)
-
-
-
Octanol-water partition coefficient at pH 7, 20 °C
P
7.94 X 10-04
Calculated
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Log P
-3.1
V3 V = ChemID Online Databases; Chemspider; PubChem. (ChemID ) 3 = Unverified data of known source
Low
Fat solubility of residues
Solubility
-
-
-
Data type
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-
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Density (g ml⁻¹)
-
-
-
Dissociation constant pKa) at 25 °C
9.02
Q3 Q = Miscellaneous data from online sources 3 = Unverified data of known source
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Weak acid
Vapour pressure at 20 °C (mPa)
-
-
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Henry's law constant at 25 °C (Pa m³ mol⁻¹)
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-
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Volatilisation as max % of applied dose lost
From plant surface
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-
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From soil surface
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-
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Maximum UV-vis absorption L mol⁻¹ cm⁻¹
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-
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Surface tension (mN m⁻¹)
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-
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Degradation
Property
Value
Source; quality score; and other information
Interpretation
General biodegradability
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Soil degradation (days) (aerobic)
DT₅₀ (typical)
200
F3 F = U.S. EPA ECOTOX database / U.S. EPA pesticide fate database / Miscellaneous WHO documents / FAO data, IPCS INCHEM data (US EPA Databases Related to Pesticide Risk Assessment ) 3 = Unverified data of known source
Persistent
DT₅₀ (lab at 20 °C)
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-
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DT₅₀ (field)
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-
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DT₉₀ (lab at 20 °C)
-
-
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DT₉₀ (field)
-
-
-
DT₅₀ modelling endpoint
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-
-
Note
Arsenic is environmentally stable
Dissipation rate RL₅₀ (days) on plant matrix
Value
2.54
R3 R = Peer reviewed scientific publications 3 = Unverified data of known source
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Note
Peanut leaves, n=1
Dissipation rate RL₅₀ (days) on and in plant matrix
Value
-
-
-
Note
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Aqueous photolysis DT₅₀ (days) at pH 7
Value
Stable
F3 F = U.S. EPA ECOTOX database / U.S. EPA pesticide fate database / Miscellaneous WHO documents / FAO data, IPCS INCHEM data (US EPA Databases Related to Pesticide Risk Assessment ) 3 = Unverified data of known source
Stable
Note
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Aqueous hydrolysis DT₅₀ (days) at 20 °C and pH 7
Value
Stable
F3 F = U.S. EPA ECOTOX database / U.S. EPA pesticide fate database / Miscellaneous WHO documents / FAO data, IPCS INCHEM data (US EPA Databases Related to Pesticide Risk Assessment ) 3 = Unverified data of known source
Stable
Note
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Water-sediment DT₅₀ (days)
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-
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Water phase only DT₅₀ (days)
-
-
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Sediment phase only DT₅₀ (days)
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-
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Air degradation
As this parameter is not normally measured directly, a surrogate measure is used: ‘Photochemical oxidative DT₅₀’. Where data is available, this can be found in the Fate Indices section below.
Decay in stored produce DT₅₀
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Soil adsorption and mobility
Property
Value
Source; quality score; and other information
Interpretation
Linear
Kd (mL g⁻¹)
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-
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Koc (mL g⁻¹)
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Notes and range
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Freundlich
Kf (mL g⁻¹)
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-
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Kfoc (mL g⁻¹)
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1/n
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Notes and range
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pH sensitivity
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Fate indices
Property
Value
Source; quality score; and other information
Interpretation
GUS leaching potential index
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-
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SCI-GROW groundwater index (μg l⁻¹) for a 1 kg ha⁻¹ or 1 l ha⁻¹ application rate
Value
Cannot be calculated
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Note
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Potential for particle bound transport index
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Potential for loss via drain flow
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-
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Photochemical oxidative DT₅₀ (hrs) as indicator of long-range air transport risk
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-
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Bio-concentration factor
BCF (l kg⁻¹)
Low risk
Q3 Q = Miscellaneous data from online sources 3 = Unverified data of known source
Based on LogP < 3
Low risk
CT₅₀ (days)
-
-
Known metabolites
None
ECOTOXICOLOGY
Terrestrial ecotoxicology
Property
Value
Source; quality score; and other information
Interpretation
Mammals - Acute oral LD₅₀ (mg kg⁻¹)
2449
F3 F = U.S. EPA ECOTOX database / U.S. EPA pesticide fate database / Miscellaneous WHO documents / FAO data, IPCS INCHEM data (US EPA Databases Related to Pesticide Risk Assessment ) 3 = Unverified data of known source
F3 F = U.S. EPA ECOTOX database / U.S. EPA pesticide fate database / Miscellaneous WHO documents / FAO data, IPCS INCHEM data (US EPA Databases Related to Pesticide Risk Assessment ) 3 = Unverified data of known source
Rat
Low
Mammals - Dermal LD₅₀ (mg kg⁻¹ body weight)
2000
F3 F = U.S. EPA ECOTOX database / U.S. EPA pesticide fate database / Miscellaneous WHO documents / FAO data, IPCS INCHEM data (US EPA Databases Related to Pesticide Risk Assessment ) 3 = Unverified data of known source
Rabbit
-
Mammals - Inhalation LC₅₀ (mg l⁻¹)
2.2
F3 F = U.S. EPA ECOTOX database / U.S. EPA pesticide fate database / Miscellaneous WHO documents / FAO data, IPCS INCHEM data (US EPA Databases Related to Pesticide Risk Assessment ) 3 = Unverified data of known source
Rat
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Other Mammal toxicity endpoints
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-
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ADI - Acceptable Daily Intake (mg kg⁻¹ bw day⁻¹)
-
-
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ARfD - Acute Reference Dose (mg kg⁻¹ bw day⁻¹)
0.1
F3 F = U.S. EPA ECOTOX database / U.S. EPA pesticide fate database / Miscellaneous WHO documents / FAO data, IPCS INCHEM data (US EPA Databases Related to Pesticide Risk Assessment ) 3 = Unverified data of known source
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
Ecotoxicity
Human health
