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Arsenous oxide
Last updated: 22/08/2024
(Also known as: arsenious acid; arsenic trioxide; arsenic (III) oxide; arsenic (3+) oxide; diarsenic trioxide; arsenic sesquioxide)
SUMMARY
Arsenous oxide was once used as a rodenticide and in sheep dips. It is no longer approved for use in most countries due to its toxicity to humans and the environment. Arsenous oxide is highly toxic to all mammals, is a carcinogen, a reproduction toxin and highly corrosive. It is quite soluble in aqueous solution but practically insoluble in most organic solvents. It is also toxic to most fauna and flora.
GENERAL INFORMATION
Description
A now obsolete antiparasitic agent
Availability status
Considered obsolete but may be available in some countries
Introduction & key dates
circa 16th century, introduced
Examples of veterinary uses
Used, historically, in sheep dips
Examples of species treated
Sheep
Approval status
VMR 2013/2033 approval status (GB/UK)
Not approved
EU Regulatory approval status
Not approved
Chemical structure
Isomerism
None
Chemical formula
As₂O₃
Canonical SMILES
[O-2].[O-2].[O-2].[As+3].[As+3]
Isomeric SMILES
-
International Chemical Identifier key (InChIKey)
QTLQKAJBUDWPIB-UHFFFAOYSA-N
International Chemical Identifier (InChI)
InChI=1S/2As.3O/q2*+3;3*-2
2D structure diagram/image available?
Yes
General status
Veterinary substance type
Antiparasitic
Substance groups
Inorganic compound
Minimum active substance purity
-
Known relevant impurities
-
Substance origin
Synthetic
Mode of action
Inhibits sulfhydral enzymes
Molecular targets
[Sulfhydral enzymes, Inhibitor]
CAS RN
1327-53-3
Alternative/old CAS RN
28380-38-3
EC number
215–481–4
CIPAC number
250
US EPA chemical code
-
PubChem CID
14888
CLP index number
033-003-00-0
Therapeutic Class
-
ATCvet Code
Not allocated
Controlled Drug?
No
Regulation 37/2010 MRL Classification
-
Molecular mass
197.84
PIN (Preferred Identification Name)
diarsenic trioxide
IUPAC name
diarsenic trioxide
CAS name
arsenic oxide
Other status information
PAB Bad Actor Chemical
Relevant Environmental Water Quality Standards
-
Physical state
Colourless crystalline solid
Formulations
Property
Product
Manufacturer
Authorisation Route
Legal Class (GB/UK)
Example products (past and present) using this active
- - - -
Formulation and application details
-
ENVIRONMENTAL FATE
Property
Value
Source; quality score; and other information
Interpretation
Solubility - In water at 20 °C (mg l⁻¹)
17000
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)
Insoluble
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
Chloroform		 -
Insoluble
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
Diethyl ether		 -
Insoluble
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
Ethanol		 -
Melting point (°C)
272
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
 -
Boiling point (°C)
465
Q3 Q = Miscellaneous data from online sources
3 = Unverified data of known source
 -
Degradation point (°C)
- - -
Flashpoint (°C)
- - -
Octanol-water partition coefficient at pH 7, 20 °C
P
- - -
Log P
- - -
Fat solubility of residues
Solubility
- - -
Data type
- - -
Density (g ml⁻¹)
- - -
Dissociation constant pKa) at 25 °C
- - -
-
Vapour pressure at 20 °C (mPa)
- - -
Henry's law constant at 25 °C (Pa m³ mol⁻¹)
- - -
Volatilisation as max % of applied dose lost
From plant surface
- - -
From soil surface
- - -
Maximum UV-vis absorption L mol⁻¹ cm⁻¹
- - -
Surface tension (mN m⁻¹)
- - -
Refractive Index
- - -
Environmental release
-
Degradation
Property
Value
Source; quality score; and other information
Interpretation
Soil degradation (days) (aerobic)
DT₅₀ (typical)
- - -
DT₅₀ (lab at 20 °C)
- - -
DT₅₀ (field)
- - -
DT₉₀ (lab at 20 °C)
- - -
DT₉₀ (field)
- - -
Note
-
Manure DT₅₀ (days)
- - -
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)
- - -
Sediment phase only DT₅₀ (days)
- - -
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
-
Soil adsorption and mobility
Property
Value
Source; quality score; and other information
Interpretation
Linear
Kd (mL g⁻¹)
- - -
Koc (mL g⁻¹)
-
Notes and range
-
Freundlich
Kf (mL g⁻¹)
- - -
Kfoc (mL g⁻¹)
-
1/n
-
Notes and range
-
pH sensitivity
-
Fate indices
Property
Value
Source; quality score; and other information
Interpretation
GUS leaching potential index
- - -
Bio-concentration factor
BCF (l kg⁻¹)
- - -
CT₅₀ (days)
- -
Known metabolites

None

ECOTOXICOLOGY
Terrestrial ecotoxicology
Property
Value
Source; quality score; and other information
Interpretation
Mammals - Acute oral LD₅₀ (mg kg⁻¹)
20
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
Rat		 High
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)
- - -
Earthworms - Acute 14 day LC₅₀ (mg kg⁻¹)
- - -
Earthworms - Chronic NOEC, reproduction (mg kg⁻¹)
- - -
Soil micro-organisms
- - -
Collembola
Acute LC₅₀ (mg kg⁻¹)
- - -
Chronic NOEC (mg kg⁻¹)
- - -
Non-target plants
- - -
- - -
Honeybees (Apis 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)
- - -
Unknown mode acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg bee⁻¹)
- - -
Chronic
- - -
Notes
-
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 bee species (1)
Acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg insect⁻¹)
- - -
Mode of exposure
-
Other bee species (2)
Acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg insect⁻¹)
- - -
Mode of exposure
-
Beneficial insects (Ladybirds)
- - -
Beneficial insects (Lacewings)
- - -
Beneficial insects (Parasitic wasps)
- - -
Beneficial insects (Predatory mites)
- - -
Beneficial insects (Ground beetles)
- - -
Aquatic ecotoxicology
Property
Value
Source; quality score; and other information
Interpretation
Temperate Freshwater Fish - Acute 96 hour LC₅₀ (mg l⁻¹)
> 18.1
F4 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 )
4 = Verified data
Oncorhynchus mykiss		 Moderate
Temperate Freshwater Fish - Chronic 21 day NOEC (mg l⁻¹)
2.65
P3 P = Other non-EU, UK or US Governments and Regulators
3 = Unverified data of known source
Oncorhynchus mykiss 10 day		 Moderate
Tropical Freshwater Fish - Acute 96 hour LC₅₀ (mg l⁻¹)
> 12.9
F4 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 )
4 = Verified data
Danio rerio		 Moderate
Temperate Freshwater Aquatic invertebrates - Acute 48 hour EC₅₀ (mg l⁻¹)
> 3.85
P4 P = Other non-EU, UK or US Governments and Regulators
4 = Verified data
Daphnia magna		 Moderate
Temperate Freshwater Aquatic invertebrates - Chronic 21 day NOEC (mg l⁻¹)
1.85
P4 P = Other non-EU, UK or US Governments and Regulators
4 = Verified data
Daphnia magna		 Moderate
Tropical Freshwater Aquatic invertebrates - Acute 48 hour EC₅₀ (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)
10
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
Lemna paucicostata		 Moderate
Algae - Acute 72 hour EC₅₀, growth (mg l⁻¹)
- - -
Algae - Chronic 96 hour NOEC, growth (mg l⁻¹)
- - -
Mesocosm study data
NOEAEC mg l⁻¹
- - -
NOEAEC mg l⁻¹
- - -
Marine bivalves
- - -
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)
20
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
Rat		 High
Mammals - Dermal LD₅₀ (mg kg⁻¹ body weight)
- - -
Mammals - Inhalation LC₅₀ (mg l⁻¹)
- - -
Other Mammal toxicity endpoints
Intraperitoneal LD₅₀ = 871 mg kg⁻¹
Q3 Q = Miscellaneous data from online sources
3 = Unverified data of known source
Rat		 -
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
Highly toxic - PPE/PPC essential
Mammalian dose elimination route and rate
Eliminated in urine
Q3 Q = Miscellaneous data from online sources
3 = Unverified data of known source
 -
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
;
E2 E = Unspecified genotoxicity type (miscellaneous data source)
2 = Mixed/ambiguous results
XNo, known not to cause a problem
Reproduction / development effects Acetyl cholinesterase inhibitor Neurotoxicant
✓Yes, known to cause a problem
XNo, known not to cause a problem
?Possibly, status not identified
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
Extremely toxic
IARC Group 1 carcinogen
Will cause a number of severe symptoms if ingested including chest pains, dizziness, breathing problems and weakness
Handling issues
Property
Value and interpretation
General
Dissolves in alkali to form toxic arsenites
Corrosive
CLP classification 2013
-
WHO Classification
Ia (Extremely hazardous)
UN Number
-
Waste disposal & packaging
-
Shelf-life, storage, stability and reactivity
-
TRANSLATIONS
Language
Name
English
arsenous oxide
French
oxyde arsenieux
German
-
Danish
-
Italian
-
Spanish
-
Greek
-
Polish
-
Swedish
-
Hungarian
-
Dutch
-
Norwegian
-
Record last updated: 22/08/2024
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