Nickel compounds and metallic nickel

ROC STATUS: Metallic nickel, reasonably anticipated human carcinogen since 1980; nickel compounds, known human carcinogens since 2002

ALSO KNOWN AS: Ni

DEFINITION: Nickel is a silvery-white, hard, malleable, and ductile metal that forms complex compounds, often with oxygen, sulfur, iron, and arsenic. Some nickel uptake may be essential to humans, but more concentrated amounts can be harmful. It remains unknown exactly which forms of nickel compounds are carcinogenic. Still, studies show that airborne and water-soluble compounds may be most associated with cancer risk, possibly because of greater exposure.

Because nickel is widely distributed in soils, water, air, detergents, tobacco, e-cigarette liquid, and food, everyone is exposed to varying levels of nickel and its compounds. Food, including vegetables and chocolates, often contains larger amounts of nickel, as does tobacco. Nickel fumes or contaminants released by tobacco smoking may cause an increased risk of respiratory cancers, including those of the nose, larynx, and lungs. Contaminant levels of nickel in humans have also been linked with congenital disabilities, including heart disorders, and have been implicated in the cancerous proliferation of breast cells.

In addition to being identified in the National Toxicology Program’s Report on Carcinogens as carcinogenic, nickel compounds and nickel metal are classified by the International Agency for Research on Cancer (IARC) as Group 1 compounds, which are “carcinogenic to humans.” Nickel and its compounds have also been identified as hazardous air pollutants in the United States Clean Air Act. Nickel subsulfide and nickel refinery dust are labeled carcinogens by the U.S. Environmental Protection Agency (EPA).

RELATED CANCERS: Nasal, throat, lung, breast, and prostate cancers

Exposure routes: Inhalation of nickel fumes from tobacco smoke, e-cigarettes, and aerosols; burning of fossil fuels; ingestion of foods, especially chocolates and vegetables; medical devices,

Where found: Earth has a solid nickel core, and most soils typically contain trace amounts of nickel, which can be absorbed by plants and ingested by animals, including humans. Soil nickel and nickel compounds may be leached into water systems or wind-driven and carried as nickel-contaminated dust in the atmosphere. Small amounts of nickel and its compounds also occur in the world’s oceans and seas, where organisms can absorb it. It is a contaminant in coal and oil and is emitted into the atmosphere by power plants and incinerators. Nickel compounds are also found in jewelry, other metals, and everyday household items such as detergents.

At risk: Everyone is at some risk. Workers in smelters that process ores containing nickel, in the electroplating industry, and in steel manufacturing are at risk of higher exposure to nickel and its compounds. Tobacco use in all its forms also exposes heavy users to nickel contaminants that may increase the risk of cancer. A blood, urine, or feces test can measure the amount of nickel in the human body for those concerned about possible high exposure.

Etiology and symptoms of associated cancers: Nasal, throat, lung, breast, and prostate cancer are all related to inhalation or ingestion of nickel compounds and metallic nickel in excess amounts. Nasal, throat, and lung cancer can affect breathing, speaking, taste, and smell. Breast cancer can be present in the form of a subdermal lump that may be painful. Prostate cancer can cause severe pain, decrease urination flow, frequency, or strength, and inhibit ejaculation. It can be present in the form of a subdermal lump that may be painful.

History: Nickel and its compounds are primarily used to prepare alloys of steel and other metal products. For example, adding nickel to steel, copper, and other metals makes an alloy stronger and more resistant to heat and corrosion. Thus, nickel is essential in gas turbines and rocket engines, where strength and resistance to high temperatures are factors. Nickel alloys are also used to manufacture propeller shafts of boats and piping in desalinization plants, where corrosion resistance is important. Nickel is also a key ingredient in rechargeable nickel-cadmium batteries, coinage, and nickel plating of jewelry and other products.

Nickel and its compounds are recognized and listed as carcinogenic, especially in occupations where workers are routinely exposed to nickel fumes. In 1984, the EPA formally determined that nickel and its compounds, especially nickel subsulfides, are human carcinogens. In 1990, the International Agency for Research on Cancer also listed nickel and its compounds as potentially carcinogenic.

Bibliography

"Nickel Compounds and Metallic Nickel: 15th Report on Carcinogens." National Toxicology Program, National Institutes of Health, 2021, www.ncbi.nlm.nih.gov/books/NBK590828. Accessed 20 June 2024.

"Nickel Compounds." National Cancer Institute, 8 Dec. 2022, www.cancer.gov/about-cancer/causes-prevention/risk/substances/nickel. Accessed 20 June 2024.

"Nickel - ToxFAQs." Agency for Toxic Substances and Disease Registry, Aug. 2023, www.atsdr.cdc.gov/toxfaqs/tfacts15.pdf. Accessed 20 June 2024.

"Occupational Cancer." Centers for Disease Control, U.S. Department of Health & Human Services, 12 Feb. 2024, www.cdc.gov/niosh/topics/cancer/default.html. Accessed 20 June 2024.

Prueitt, Robyn L. "Systematic Review of the Potential Respiratory Carcinogenicity of Metallic Nickel in Humans." Critical Reviews in Toxicology, vol. 50, no. 7, 2020, pp. 605–639. doi.org/10.1080/10408444.2020.1803792.

"The Facts on Nickel." Dartmouth Toxic Metals Superfund Research Program, Dartmouth College, 2022, sites.dartmouth.edu/toxmetal/more-metals/nickel-hidden-in-plain-sight/the-facts-on-nickel. Accessed 20 June 2024.