Arsenic selenide (As2Se3): Human health tier II assessment

04 July 2014

CAS Number: 1303-36-2

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This assessment was carried out by staff of the National Industrial Chemicals Notification and Assessment Scheme (NICNAS) using the Inventory Multi-tiered Assessment and Prioritisation (IMAP) framework.

The IMAP framework addresses the human health and environmental impacts of previously unassessed industrial chemicals listed on the Australian Inventory of Chemical Substances (the Inventory).

The framework was developed with significant input from stakeholders and provides a more rapid, flexible and transparent approach for the assessment of chemicals listed on the Inventory.

Stage One of the implementation of this framework, which lasted four years from 1 July 2012, examined 3000 chemicals meeting characteristics identified by stakeholders as needing priority assessment. This included chemicals for which NICNAS already held exposure information, chemicals identified as a concern or for which regulatory action had been taken overseas, and chemicals detected in international studies analysing chemicals present in babies’ umbilical cord blood.

Stage Two of IMAP began in July 2016. We are continuing to assess chemicals on the Inventory, including chemicals identified as a concern for which action has been taken overseas and chemicals that can be rapidly identified and assessed by using Stage One information. We are also continuing to publish information for chemicals on the Inventory that pose a low risk to human health or the environment or both. This work provides efficiencies and enables us to identify higher risk chemicals requiring assessment.

The IMAP framework is a science and risk-based model designed to align the assessment effort with the human health and environmental impacts of chemicals. It has three tiers of assessment, with the assessment effort increasing with each tier. The Tier I assessment is a high throughput approach using tabulated electronic data. The Tier II assessment is an evaluation of risk on a substance-by-substance or chemical category-by-category basis. Tier III assessments are conducted to address specific concerns that could not be resolved during the Tier II assessment.

These assessments are carried out by staff employed by the Australian Government Department of Health and the Australian Government Department of the Environment and Energy. The human health and environment risk assessments are conducted and published separately, using information available at the time, and may be undertaken at different tiers.

This chemical or group of chemicals are being assessed at Tier II because the Tier I assessment indicated that it needed further investigation.

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NICNAS has made every effort to assure the quality of information available in this report. However, before relying on it for a specific purpose, users should obtain advice relevant to their particular circumstances. This report has been prepared by NICNAS using a range of sources, including information from databases maintained by third parties, which include data supplied by industry. NICNAS has not verified and cannot guarantee the correctness of all information obtained from those databases. Reproduction or further distribution of this information may be subject to copyright protection. Use of this information without obtaining the permission from the owner(s) of the respective information might violate the rights of the owner. NICNAS does not take any responsibility whatsoever for any copyright or other infringements that may be caused by using this information.

Acronyms & Abbreviations

Chemical Identity

Synonyms Arsenic sesquiselenide
Arsenous selenide
Diarsenic triselenide

Structural Formula Structural formula of Arsenic selenide (As2Se3)
Molecular Formula As2Se3
Molecular Weight (g/mol) 386.72
Appearance and Odour (where available) Odourless brown/black powder.
SMILES [As](=[Se])[Se][As]=[Se]


No specific Australian use, import, or manufacturing information has been identified.


The following international uses have been identified through the United States geological survey (USGS) website:

The chemical has reported commercial use including:

  • coating of photoconductors used in photocopying machines (drum).

The chemical has reported site-limited use including:

  • as a laboratory reagent.


The chemical, is specifically exempted for its major use from the group entry 'arsenic' in the Poisons Standard (Standard for the Uniform Scheduling of Medicines and Poisons (SUSMP)) in Schedule 7 which has below entry for industrial uses: "ARSENIC except:

(a) when separately specified in this Schedule;

(b) when included in Schedule 4 or 6;

(c) as selenium arsenide in photocopier drums;

(d) as 10,10'-oxydiphenoxarsine in silicone rubber mastic containing 120 mg/kg or less of arsenic;

(e) as 10,10'-oxydiphenoxarsine contained in polyvinyl chloride and polyurethane extruded and moulded articles containing 160 mg/kg or less of arsenic other than when included in articles:

(i) in contact with food stuffs, animal feeds or potable water;

(ii) of clothing and footwear in contact with the skin;

(iii) used as infant wear; or

(iv) intended for use as packaging materials;

(f) in animal feeds containing 75 g/tonne or less of arsenic; or

(g) in paints containing 0.1 % or less of arsenic calculated on the non-volatile content of the paint."

Schedule 7 chemicals are labelled with 'Dangerous Poison'.  These are substances with a high potential for causing harm at low exposure and which require special precautions during manufacture, handling or use. These poisons should be available only to specialised or authorised users who have the skills necessary to handle them safely. Special regulations restricting their availability, possession, storage or use may apply.

"Arsenic and its compounds" are restricted hazardous chemicals under Schedule 10 (Prohibited carcinogens, restricted carcinogens and restricted hazardous chemicals) of the Work Health and Safety (WHS) regulations (WHS, 2011). Specifically, use is restricted in: abrasive blasting at a concentration of greater than 0.1 % as arsenic; and for spray painting.


International restrictions include:

European Union (EU) Cosmetic Directive 76/768/EEC Annex II: List of substances which must not form part of the composition of cosmetic products.

Canada List of Prohibited and Restricted Cosmetic Ingredients ("Hotlist").

New Zealand cosmetic products group standard - Schedule 4: Components cosmetic products must not contain.

Existing Work Health and Safety Controls

Hazard Classification

The chemical ("Arsenic compounds with the exception of those specified elsewhere in HSIS") is classified as hazardous, with the following risk phrases for human health in the Hazardous Substances Information System (HSIS) (Safe Work Australia):

T; R23/25 (Acute toxicity)


No specific exposure standards are available.


The following exposure standards are identified (Galleria Chemica):

An exposure limit time weighted average (TWA) of 0.01–5 mg/m³ in different countries such as USA (Alaska, Hawaii), Canada (Yukon), Norway and Switzerland.

In the absence of specific data for arsenic selenide (1303-33-9), data available for the trivalent inorganic arsenic compounds (trivalent arsenites) can be used for this chemical as it is an inorganic arsenic compound with an oxidative state of +3. The key health hazards of the chemical are those identified in the NICNAS assessment of trivalent arsenites (NICNAS a). These are carcinogenicity, genotoxicity, corrosiveness, acute toxicity and damage to health by repeated oral exposure. The solubility of the chemical, and hence the bioavailability of arsenic, will impact on the acute effects through oral, dermal or inhalation exposure and highly insoluble compounds are not expected to have corrosive local effects. However, chronic exposure, even to insoluble compounds such as arsenic selenide (1303-36-2) may result in long term systemic effects such as cancer (IARC, 2012, NICNAS b). As selenium and sulfur lie in the same group of compounds in the periodic table of elements, the current hazards identified are likely to be similar to the naturally occurring arsenic sulfides (realgar and orpiment (1303-33-9), neither of which are listed on AICS as they are naturally occurring substances).

Critical Health Effects

The critical health effects for risk characterisation include systemic long-term effects (carcinogenicity and genotoxicity), systemic acute effects (acute toxicity by the oral route of exposure) and local effects (corrosivity). The chemical may also cause toxic effects following repeated exposure through inhalation.

Available data for trivalent arsenites on reproductive and developmental toxicity are equivocal. However, risk management controls to mitigate risk from the above hazards would be sufficient to address reproductive and developmental toxicity.  

Public Risk Characterisation

Given the uses identified for the chemical, it is unlikely that the public will be exposed. Hence, the public risk from this chemical is not considered to be unreasonable.

Occupational Risk Characterisation

There is expected to be very limited occupational exposure to the chemical due to its very specialised major use (photoconductors in photocopying machines). However, given the critical systemic long-term and systemic acute health effects, the chemical may pose an unreasonable risk to workers unless adequate control measures to minimise oral and inhalation exposure to the chemical are implemented. The chemical should be appropriately classified and labelled to ensure that a person conducting a business or undertaking (PCBU) at a workplace (such as an employer) has adequate information to determine appropriate controls.

The data available support an amendment to the hazard classification in HSIS (refer to Recommendation section).

NICNAS Recommendation

Current risk management measures are considered adequate to protect public and workers’ health and safety, provided that all requirements are met under workplace health and safety and poisons legislation as adopted by the relevant state or territory. No further assessment is required.

Work Health and Safety

The chemical is recommended for classification and labelling under the current approved criteria and adopted GHS as below. This does not consider classification of physical hazards and environmental hazards.

Hazard Approved Criteria (HSIS)a GHS Classification (HCIS)b
Acute Toxicity Very toxic if swallowed (T+; R28) Toxic by inhalation (T; R23)* Fatal if swallowed - Cat. 2 (H300) Toxic if inhaled - Cat. 3 (H331)
Repeat Dose Toxicity Toxic: danger of serious damage to health by prolonged exposure through inhalation (T; R48/23) Toxic: Danger of serious damage to health by prolonged exposure if swallowed (T; R48/25) Causes damage to organs through prolonged or repeated exposure - Cat. 1 (H372) Causes damage to organs through prolonged or repeated exposure - Cat. 1 (H372)
Genotoxicity Muta. Cat 3 - Possible risk of irreversible effects (Xn; R68) Suspected of causing genetic defects - Cat. 2 (H341)
Carcinogenicity Carc. Cat 1 - May cause cancer (T; R45) May cause cancer - Cat. 1A (H350)

a Approved Criteria for Classifying Hazardous Substances [NOHSC:1008(2004)].

b Globally Harmonized System of Classification and Labelling of Chemicals (GHS) United Nations, 2009. Third Edition.

* Existing Hazard Classification. No change recommended to this classification

Advice for industry

Control measures

Control measures to minimise the risk from oral and inhalation exposure to the chemical should be implemented in accordance with the hierarchy of controls.  Approaches to minimise risk include substitution, isolation and engineering controls. Measures required to eliminate or minimise risk arising from storing, handling and using a hazardous chemical depend on the physical form and the manner in which the chemical is used.  Examples of control measures which may minimise the risk include, but are not limited to:

    • using closed systems or isolating operations;
    • using local exhaust ventilation to prevent the chemical from entering the breathing zone of any worker;
    • health monitoring for any worker who is at risk of exposure to the chemical if valid techniques are available to monitor the effect on the worker’s health;  
    • minimising manual processes and work tasks through automating processes;
    • work procedures that minimise splashes and spills;  
    • regularly cleaning equipment and work areas; and
    • using protective equipment that is designed, constructed, and operated to ensure that the worker does not come into contact with the chemical.

Guidance on managing risks from hazardous chemicals are provided in the Managing Risks of Hazardous Chemicals in the Workplace—Code of Practice  available on the Safe Work Australia website.

Personal protective equipment should not solely be relied upon to control risk and should only be used when all other reasonably practicable control measures do not eliminate or sufficiently minimise risk. Guidance in selecting personal protective equipment can be obtained from Australian, Australian/New Zealand or other approved standards.

Obligations under workplace health and safety legislation

Information in this report should be taken into account to assist with meeting obligations under workplace health and safety legislation as adopted by the relevant state or territory.  This includes, but is not limited to:

    • ensuring that hazardous chemicals are correctly classified and labelled;
    • ensuring that (material) safety data sheets ((m)SDS) containing accurate information about the hazards (relating to both health hazards and physicochemical (physical) hazards) of the chemical are prepared; and
    • managing risks arising from storing, handling and using a hazardous chemical.

Your work health and safety regulator should be contacted for information on the work health and safety laws in your jurisdiction.

Information on how to prepare an (m)SDS and how to label containers of hazardous chemicals are provided in relevant codes of practice such as the Preparation of Safety Data Sheets for Hazardous Chemicals— Code of Practice and Labelling of Workplace Hazardous Chemicals—Code of Practice, respectively. These codes of practice are available from the Safe Work Australia website.

A review of the physical hazards of the chemical has not been undertaken as part of this assessment.


Galleria Chemica. Accessed June 2013 at

Globally Harmonised System of Classification and Labelling of Chemicals (GHS) United Nations, 2009. Third edition. Accessed at

International Agency for Research on Cancer (IARC) (2012). Arsenic and arsenic compounds monograph. Accessed May 2013 at

National Industrial Chemicals Notification and Assessment Scheme (NICNAS). Human health Tier II assessment for trivalent arsenites. Australian Government Department of Health and Ageing. Accessed June 2013 at

Safe Work Australia (SWA). Model Work Health and Safety Regulations. Accessed June 2013 at

Safe Work Australia Hazardous Substances Information System (HSIS). Accessed June 2013 at

The Poisons Standard (the Standard for the Uniform Scheduling of Medicines and Poisons (SUSMP)) 2012. Accessed June 2013 at

United States Geological survey (USGS), Selenium and Tellurium (2003). Accessed June 2013 at

Last update 04 July 2014