Mineral oils and cancer
Mineral oils, which include untreated and mildly refined petroleum distillates, have been classified as known human carcinogens since 1980. These substances comprise complex mixtures of hydrocarbons and are prevalent in various industrial settings, where they are commonly used as lubricants and in the manufacturing of refined oil products. Research has linked mineral oil exposure to several types of cancers, particularly skin cancers such as squamous cell carcinoma, as well as stomach, bladder, pancreatic, lung, and throat cancers. The primary routes of exposure include dermal contact, inhalation, and ingestion, which can occur in industries like metalworking, printing, and automobile manufacturing.
Symptoms associated with mineral oil-related cancers may vary, with skin cancers resulting in painful marks or tumors, and gastrointestinal cancers often causing abdominal pain. Inhalation or ingestion can lead to respiratory issues that progressively worsen. Although studies have shown a consistent association between mineral oil exposure and certain cancers, some research has produced conflicting results. Despite the identified health risks, mineral oils remain widely used across many sectors, underscoring the importance of awareness and safety measures in their handling.
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Subject Terms
Mineral oils and cancer
ROC STATUS: Known human carcinogen since 1980
ALSO KNOWN AS: Petroleum distillate, untreated and mildly refined oils
RELATED CANCERS: Skin cancers, particularly squamous skin cell cancers of the scrotum, as well as stomach, bladder, pancreatic, large intestine, rectal, mouth, throat, and lung cancers
DEFINITION: Mineral oils include lubricant-based oils and other products derived from them. They are insoluble in water and are composed of complex mixtures of aliphatic hydrocarbons, naphthenics, and aromatics. Among those considered to be most carcinogenic are the polycyclic aromatic hydrocarbons (PAH), particularly benzopyrene, as well as nitrosamines, chlorinated paraffins, long-chain aliphatics, sulfur, N-phenyl-2-naphthylamine, and formaldehyde.
Exposure routes: Mineral oils can be absorbed directly through dermal contact, via inhalation, and by ingestion of substances containing or contaminated with untreated or mildly treated mineral oils.
Where found: Minerals are found at industry work sites and in the environment. By one estimate, more than 1.3 billion gallons of used (and potentially contaminated) motor oil are produced annually, of which, the US Environmental Protection Agency believes, 500 million gallons are disposed of improperly.
At risk: Workers in the metal, glass, newspaper printing, automobile, and airplane manufacture, and cotton and jute spinning industries are commonly in contact with mildly treated or untreated mineral oils.
ETIOLOGY AND SYMPTOMS OF ASSOCIATED CANCERS: Mineral oils generally cause skin cancers by dermal contact, resulting in red, swollen, and possibly painful marks or tumors on or beneath the skin. Stomach cancer and pancreatic cancer often cause abdominal pain. Bladder, large intestine, and rectal cancers, often caused by ingestion of harmful levels of mineral oils, affect the excretion of waste, making urination or excretion painful. Cancers of the mouth, throat, and lung are generally caused by inhalation or ingestion of toxic substances in mineral oils. First symptoms are flulike or coldlike irritation of breathing passages, which progressively increases to the point at which breathing and speaking are affected, eventually severely.
History: Mineral oils are used as a base in manufacturing many types of refined lubricant oils. These refined oil products are used in construction work, metalwork, diesel oil manufacturing, and mining. According to the Report on Carcinogens (2021), many lubricating oils are used in automobile manufacturing and operation. These include engine oils, transmission oils, lubricating oils for gears, bearing oils, and transmission fluids. Highly refined and purified white mineral oils are used for certain medicinal, food, and pharmacological purposes.
Most studies on mineral oils as carcinogens have involved relationships between cancers and metalworkers. Case studies published in the early 1980s revealed an excess incidence of skin cancers, particularly scrotal cancer, in these metalworkers, as well as higher levels of gastrointestinal and bladder cancers. Similarly, studies of cancer incidence in printing occupations have suggested an increased incidence of and mortality related to a variety of respiratory cancers, including buccal cavity, pharyngeal, and lung cancers due to mineral oil exposure. However, some subsequent research generated inconsistent or contradictory findings regarding the role of mineral oil in developing such a range of cancer sites.
Results from several animal studies show similar relationships. For example, mice treated with repeated application of mineral oils directly to the skin had dramatically increased incidence of skin cancer. Similar applications of mineral oils to rabbits and rhesus monkeys produced tumors typically associated with the skin. Further, recent reviews of studies and epidemiological studies have appeared to confirm an association between exposure to mineral oil and other cancers.
Despite the significant health risks, mineral oils continue to be widely used in the United States and globally, with their products available for sale everywhere. The majority of manufactured mineral oil products are used for lubricants, another smaller percent is used as aromatic oils, and the remaining are produced for greases. Refined mineral oils remain an important component of many industries where lubricants are necessary, highlighting the pervasiveness of the issue.
Bibliography
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IARC Working Group on the Evaluation of Carcinogenic Risks to Humans. Chemical Agents and Related Occupations: A Review of Human Carcinogens. vol. 100F. Lyon: Internatl. Agency for Research on Cancer, 2012.
James, Ken, and Brian Handwerk. “Is Motor Oil a Renewable Resource? Re-refiners Say Yes.” National Geographic, 2 June 2011, www.nationalgeographic.com/science/article/110601-green-motor-oil-recycling. Accessed 27 June 2024.
“Mineral Oils: Untreated and Mildly Treated - Cancer-Causing Substances.” National Cancer Institute, 3 May 2024, www.cancer.gov/about-cancer/causes-prevention/risk/substances/mineral-oils. Accessed 27 June 2024.
"NPDES: Stormwater Best Management Practice, Developing a Used Oil Recycling Program." Environmental Protection Agency, Dec. 2021, www.epa.gov/system/files/documents/2021-11/bmp-developing-a-used-oil-recycling-program.pdf. Accessed 27 June 2024.
Wright, Jeremy. “The Fundamentals of Mineral Base Oil Refining.” Machinery Lubrication, 2012, www.machinerylubrication.com/Read/28960/mineral-oil-refining. Accessed 27 June 2024.