Mineral oil is a transparent, colorless, and odorless substance derived from petroleum. It is a complex mixture of various hydrocarbons, primarily alkanes and cycloalkanes, and its stability and low cost make it useful in both industrial and consumer applications. The widespread use of this petroleum derivative has led to public concern regarding its potential link to cancer. A factual, evidence-based distinction must be made to clarify the actual risk, as the safety profile depends entirely on its manufacturing process, which determines the final grade.
Understanding the Different Grades of Mineral Oil
The term “mineral oil” is a broad designation covering substances with different refinement levels and safety profiles. The factor that differentiates these grades is the removal of specific aromatic compounds during manufacturing. These compounds are polycyclic aromatic hydrocarbons (PAHs), which are naturally present in crude petroleum oil and are known to be carcinogenic.
The most basic, unrefined mineral oil is often referred to as industrial grade and is used in settings like machining or metal processing. This grade retains a higher concentration of PAHs, making it unsuitable for contact with food, medicine, or the human body. Confusion about mineral oil’s safety often stems from failing to differentiate this industrial product from the consumer-grade equivalent.
In contrast, the type of mineral oil found in consumer products is highly refined, often called white mineral oil or pharmaceutical grade. Extensive processing steps, such as solvent extraction and hydro-treatment, are used to remove the hazardous aromatic components. These refining steps purify the oil to a point where it is chemically stable, inert, and meets the safety requirements for human use.
Official Carcinogen Classification: The Scientific Consensus
The definitive answer to mineral oil’s cancer risk is found in the classification provided by international scientific bodies like the International Agency for Research on Cancer (IARC). IARC, part of the World Health Organization, has evaluated mineral oils and issued different classifications based on their degree of refinement.
Untreated or mildly-treated mineral oils, those that retain high levels of PAHs, are classified by IARC as Group 1 substances, meaning they are known to be carcinogenic to humans. This classification is based on occupational studies, such as those involving mulespinners and metal workers, who experienced prolonged skin exposure to these less-refined industrial oils decades ago. The cancer-causing potential is directly linked to the presence of 3-to-7 ring polycyclic aromatic compounds (PACs) that were not removed in older refining methods.
The classification changes for the highly refined mineral oils used in modern consumer goods. These white mineral oils are classified by IARC as Group 3, meaning they are “not classifiable as to its carcinogenicity to humans.” This means there is insufficient scientific evidence to conclude that this highly purified grade poses a cancer risk. The extensive refinement process effectively removes the carcinogenic PAHs, rendering the final product non-hazardous.
The process of refinement determines the risk profile. Scientific bodies confirm that the highly processed, purified oil is fundamentally different from its crude source material. The National Toxicology Program (NTP) similarly does not list highly refined white mineral oil as a known or reasonably anticipated human carcinogen.
Regulatory Safety Standards in Consumer Products
Regulatory bodies worldwide enforce purity standards to ensure that only non-hazardous, highly refined mineral oil is used in consumer applications. These standards translate the scientific consensus into practical guidelines for manufacturers. The purification process is rigorous, requiring the final product to meet specifications comparable to pharmaceutical-grade ingredients.
In the United States, the Food and Drug Administration (FDA) regulates mineral oil as a direct food additive under specific conditions, such as for use in food packaging or as a protective coating. The oil must meet the purity requirements of the U.S. Pharmacopeia (USP) standard for white mineral oil. These requirements ensure the oil is free from carcinogenic aromatic hydrocarbons.
European Union regulations impose purity thresholds for mineral oil used in cosmetics and food contact materials. A key measure is the IP 346 test, which ensures the oil contains less than three percent of substances extractable with dimethyl sulfoxide (DMSO). This low extractable content serves as a proxy measure for the near-complete absence of carcinogenic PAHs.
This regulatory framework ensures that common consumer products like baby oil, lotions, and certain laxatives contain only the highly refined, non-carcinogenic grade of mineral oil. When highly refined mineral oil is used as intended in regulated consumer goods, it poses no known carcinogenic risk.