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Mineral Oils: Untreated and Mildly Treated

Workers in engine repair are among those most commonly exposed to mineral oils.

What are mineral oils?

The name mineral oil has been used to describe many colorless, odorless liquids. Most often, the term refers to a liquid by-product of the distillation of petroleum to produce gasoline and other petroleum-based products from crude oil. These oils, including lubricant base oils and products derived from them, are used in manufacturing, mining, construction, and other industries.

A complete description of mineral oils should include how the oils are refined. Oils used in cosmetic products are typically highly refined, whereas those used in automotive oils and fluids tend to be unrefined or only mildly treated. Highly refined products are not covered in this section.

How are people exposed to mineral oils?

Occupational exposure to mineral oils may occur among workers in various industries, including the manufacture of automobiles, airplanes, steel products, screws, pipes, and transformers. Workers in brass and aluminum production, engine repair, copper mining, and newspaper and commercial printing may also be exposed to mineral oils. The general population may be exposed to mineral oils that occur naturally or are present as environmental contaminants.

Which cancers are associated with exposure to mineral oils?

Exposure to mineral oils is strongly associated with an increased risk of nonmelanoma skin cancer, particularly of the scrotum.

How can exposures be reduced?

The U.S. Occupational Safety & Health Administration provides information about exposure limits to mineral oils.

Selected References:

  • International Agency for Research on Cancer. Mineral Oils, Untreated or Mildly Treated, IARC Monographs on the Evaluation of Carcinogenic Risks to Humans, Volume 100F. Lyon, France: World Health Organization, 2012. Also available online. Last accessed February 15, 2019.
  • National Institute of Occupational Safety and Health. Oil Mist (Mineral), NIOSH Pocket Guide to Chemical Hazards. Atlanta, GA: Centers for Disease Control and Prevention, 2010. Also available online. Last accessed February 15, 2019.
  • National Toxicology Program. Mineral Oils: Untreated and Mildly Treated, Report on Carcinogens, Fifteenth Edition. Triangle Park, NC: National Institute of Environmental Health and Safety, 2021. Also available online. Last accessed December 5, 2022.
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