Indium Phosphide and Other Indium Compounds
Full Profile
General Information
Indium phosphide is composed of indium metal and phosphorus. It is a by-product created during the production of other base-metals such as zinc, copper, lead and tin.[2,3] It may also be referred to as indium mono-phosphide or InP; see the HSDB for other names and synonyms.[4]
Indium phosphide has been classified by IARC as a group 2A carcinogen, probably carcinogenic to humans.[2] Indium phosphide is carcinogenic in experimental animals.[2] Indium phosphide exposure increased the incidence of alveolar and bronchiolar carcinomas in mice and rats.[2] Other reported exposure-related cancers include hepatocellular adenomas/carcinomas and benign and malignant pheochromocytomas of the adrenal gland.[2, 12, 13] No epidemiologic studies were available for the IARC Working Group to evaluate human carcinogenicity of indium phosphide.[2]
Additionally, indium phosphide is an irritant of the skin, eye and respiratory tract.[4] Individuals exposed in the workplace have reported dental erosion, joint and bone pains, nervous system and gastrointestinal system disorders, heart pains, and general malaise.[4]
Recent studies also suggest that indium tin oxide (ITO) exposure may cause interstitial lung damage.[14,22] ITO is an important indium compound used widely as a transparent conductive coating for the manufacturing of liquid crystal displays (LCDs), flat panel displays, plasma displays, touch panels, light-emitting diodes and other electronic products.[3] ITO use accounts for 80% of total indium production.[19] ITO and other indium compounds have not been evaluated by IARC as to their carcinogenicity,[23] but they are included in IARC’s recent report identifying high-priority carcinogens in need of further research.[19]
Indium phosphide has been ranked by CAREX Canada as a Group B (possible high priority) for both the occupational and environmental settings. Prioritization was based on the carcinogenicity and other toxic properties of the substance, the prevalence of exposure in Canada, and the feasibility of assessing exposure.
Regulations and Guidelines
Occupational Exposure Limits (OEL)
| Canadian Jurisdictions | OEL (mg/m3) |
|---|---|
| Canada Labour Code | 0.1 |
| BC, AB, MB, ON, QC, NL, PE, NB, NS | 0.1 |
| SK, YT, NT, NU | 0.1 0.3 [stel] |
| Other Jurisdictions | OEL (mg/m3) |
| ACGIH 2010 TLV | 0.1 |
Canadian Environmental Guidelines
Indium phosphide was not included in any Canadian government environmental guidelines reviewed.[11,12]
Canadian Agencies/Organizations
Indium phosphide is included in Environment Canada’s Non-Domestic Substances List (NDSL).[16] It was not included in any other Canadian government chemical listings reviewed.[10,17]
Main Uses
Indium phosphide is a semiconductor used primarily in the production of optoelectronic devices such as laser diodes, light-emitting diodes (LEDs), and solar cells.[2,13] It is also used in high performance integrated circuits.[2]
Because of its unique semiconductive properties, indium phosphide is widely used to manufacture microelectronics.[2,15] Indium phosphide and other indium compound nanoparticles, with particle diameters as small as 3 nm, have been attracting significant research interest as they have great potential for use in electronics.[13,21,22]
Canadian Production and Trade
In 2007, Teck Cominco and Xstrata Copper were the primary producers of indium in Canada, recovering the metal at their zinc refineries from domestic and imported concentrates.[3] Total Canadian production was of indium metal was estimated to be around 65 tonnes in 2007.[3] Adex Mining is also proposing extraction and refining of indium from the Mount Pleasant mine in New Brunswick, which was estimated to be capable of producing 40 tonnes of indium per year.[20]
Canada accounts for 18% of US indium imports, providing a total of 111 tonnes of indium between 2002 and 2006.[3] No information on Canadian indium phosphide production was available.
Production and Trade (Indium Metal)
| Activity | Quantity | Year |
|---|---|---|
| Export: Mainly to the US | 28 t of ‘gallium, hafnium, indium, niobium, rhenium, thallium and articles thereof’ | 2009[6] |
| Import: Mainly from the US | 56 t of ‘gallium, hafnium, indium, niobium, rhenium, thallium and articles thereof’ | 2009[6] |
Occupational Exposures
Inhalation is the most important route of occupational exposure to indium phosphide.[2] The main occupations exposed are in the microelectronics industry, including workers involved in the production of indium phosphide crystals, ingots and wafers, in grinding and sawing operations, in device fabrication, and in clean-up activities.[2]
CAREX Canada is reviewing whether it is feasible to prepare exposure estimates for Canadian workers exposed to indium phosphide. This will likely depend on availability of exposure data.
Environmental Exposures
Indium phosphide is not a naturally occurring compound, although indium is present in trace amounts in various metal ores.[2]
Very limited information is available on environmental exposure to indium phosphide.[2,12] Low concentrations of indium metal have been detected in air (43 ng/m3), seawater (20 µg/l), rain water (0.59 µg/l) and food (up to 10 µg/kg in beef and pork).[2] Indium concentrations of up to 15 mg/kg have been reported in seafood from contaminated waters near metal smelters.[2] Average daily intake was estimated to be low and in the range of 8 – 10 µg/day.[2]
Release of indium phosphide is not reportable to Environment Canada’s National Pollutant Release Inventory.[7]
No household products were listed for indium phosphide in the US Household Products Database.[8]
Sources
- Wikimedia Commons (2009) Indium Phosphide
- IARC (2006) Monograph Summary, Volume 86 (PDF)
- Natural Resources Canada (2007) Indium Mineral Year Book (PDF)
- US National Library of Medicine (2011) Hazardous Substances Data Bank entry for Indium Phosphide (Search term: ‘indium phosphide’)
- Health Canada (2006) Categorization of the Domestic Substances List under CEPA
- TradeMap (2009) Canadian International Trade (free subscription required)
- Environment Canada (2009) The National Pollutant Release Inventory
- US Department of Health and Human Services (2011) Household Products Database
- Environment Canada (2010) Toxic Substances List – CEPA Schedule 1
- Health Canada (2010) Guidelines for Canadian Drinking Water
- Health Canada (1987) Exposure Guidelines for Residential Indoor Air Quality (PDF)
- US Department of Health and Human Services (1988) NTP Indium Phosphide Support for Chemical Nomination and Selection Process of the National Toxicology Program: Draft Report
- US Department of Health and Human Services (2001) NTP Technical Report on the Toxicology and Carcinogenesis studies of Indium Phosphide (CAS NO. 22398-80-7) In F344/N rats and B6C3F1 mice (Inhalation studies) (PDF)
- Hamaguchi T, Omae K, Takebayashi T, et al. (2008) Exposure to hardly soluble indium compounds in ITO production and recycling plants is a new risk for interstitial lung damage. Occup Environ Med 65:51–55.
- Chonan T, Taguchi O, Omae K. (2007) Interstitial pulmonary diseases in indium processing workers. Eur Respir J 29:317–324.
- Government of Canada (2011) The Substances List: Search Engine for Chemicals and Polymers
- Government of Canada (2010) Chemicals Management Plan – List of all Challenge Substances
- IARC (2011) Agents Classified by the IARC Monographs, Volumes 1-100 (PDF)
- IARC (2009) Identification of research needs to resolve the carcinogenicity of high-priority IARC carcinogens.
- Adex Mining Inc (2010) Management’s Discussion and Analysis (PDF)
- Beard MC et al. (2003) Electronic Coupling in InP Nanoparticle Arrays, Nano Lett. 3(12): 1695-1699.
- Khanna PK et al. (2005) Synthesis of Indium Phosphide Nanoparticles via Catalytic Cleavage of Phosphorus Carbon Bond in n-Trioctylphosphine by Indium. Mater Chem Phys. 92 (1): 54-58.
