Indium Phosphide and Other Indium Compounds Profile
INDUSTRIAL CHEMICALS – PROBABLE CARCINOGEN (IARC 2A)
Indium Phosphide and Other Indium Compounds Profile
Indium phosphide is composed of indium metal and phosphorus. It is a byproduct created when isolating other base-metals such as zinc, copper, lead, and tin.[1,2] It may also be referred to as InP; see the Hazardous Substances Data Bank (HSDB) for other names and synonyms.
Indium phosphide has been classified by the International Agency for Research on Cancer (IARC) as Group 2A, probably carcinogenic to humans. Exposure to indium phosphide causes cancer in experimental animals, increasing the incidence of alveolar and bronchiolar carcinomas in mice and rats. Other reported exposure-related cancers include hepatocellular adenomas/carcinomas and benign and malignant tumours in the adrenal gland.[1,4,5] No epidemiologic studies were available for the IARC Working Group to evaluate human carcinogenicity of indium phosphide, however it was classified as Group 2A due to the extraordinarily high incidence of lung cancer, and cancers at other sites, at relatively low levels of exposure in animal models.
Additionally, indium phosphide irritates the skin, eyes, and respiratory tract. Individuals exposed in the workplace have reported dental erosion, joint and bone pains, nervous system and gastrointestinal system disorders, heart pains, and general malaise.
Recent studies suggest that exposure to another indium compound, indium tin oxide (ITO), may cause interstitial lung damage.[4,5] ITO and other indium compounds have not been evaluated by IARC as to their carcinogenicity, but they are included in IARC’s recent report identifying high-priority carcinogens in need of further research.
Regulations and Guidelines
|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
|Other Jurisdictions||OEL (mg/m3)|
|ACGIH 2020 TLV||0.1|
mg/m3 = milligrams per cubic meter
stel = short term exposure limit (15 min. maximum)
ACGIH = American Conference of Governmental Industrial Hygienists
TLV = threshold limit value (8 hour maximum)
Canadian environmental guidelines
Indium phosphide was not included in Canadian government guidelines and standards reviewed.
Indium phosphide is a semiconductor used primarily to produce optoelectronic devices such as laser diodes, light-emitting diodes (LEDs), and solar cells.[1,23] It is also used in high performance integrated circuits.
Because of its unique semiconductive properties, indium phosphide is widely used to manufacture microelectronics.[1,24] Indium phosphide and other indium compound nanoparticles, with particle diameters as small as 3 nanometres, have attracted significant research interest given their great potential for use in electronics.[5,23,25]
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. Total Canadian production of indium metal was estimated at approximately 60 tonnes in 2021. Adex Mining is also proposing to extract and refine indium from the Mount Pleasant mine in New Brunswick. This mine has an estimated capability to produce 40 tonnes of indium per year.[26,27]
Canada accounts for 23% of US indium imports, providing a total of 106 tonnes of indium between 2017 and 2020. No information on Canadian production of indium phosphide was available. A search of Trademap for “indium and articles thereof” revealed no data.
Environmental Exposures Overview
Indium phosphide is not a naturally occurring compound, although indium is present in trace amounts in various metal ores.
Very limited information is available on environmental exposure to indium phosphide.[1,29] Low concentrations of indium metal have been detected in air (43 ng/m3), seawater (20 µg/l), rainwater (0.59 µg/l) and food (up to 10 µg/kg in beef and pork). Indium concentrations of up to 15 mg/kg have been reported in seafood from contaminated waters near metal smelters. Average daily intake was estimated to be low and in the range of 8 – 10 µg/day.
Release of indium phosphide is not reportable to Environment Canada’s National Pollutant Release Inventory.
No household products were listed for indium phosphide in the US Household Products Database.
Occupational Exposures Overview
Inhalation is the most important route of occupational exposure to indium phosphide.
The main occupations exposed are in the microelectronics industry, including workers involved in: producing indium phosphide crystals, ingots, and wafers; grinding and sawing operations; fabricating devices; and cleaning activities.
CAREX Canada has not prioritized Indium Phosphide and other Indium compounds for exposure estimate development. This is because there is a lack of exposure monitoring data in the Canadian Workplace Exposure Database on which to base an estimate.
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