Mineral oil is a colorless, odorless liquid derived from crude oil. Mineral oil is a petroleum product because it is a byproduct of the petroleum refining process. However, the material used in consumer products is far removed from raw petroleum, having undergone extensive purification. This refinement transforms a crude oil distillate into the highly specific substance known as mineral oil.
Defining Mineral Oil and Its Origins
Mineral oil is a generic term for a light mixture of higher alkanes obtained from a mineral source, distinguishing it from vegetable or animal oils. It is a component of the non-fuel products yielded during the fractional distillation of crude oil. Crude oil is heated and separated into various fractions based on their boiling points, yielding gasoline, kerosene, and diesel, alongside heavier fractions that become base oils.
Mineral oil is chemically composed mainly of saturated hydrocarbons, including alkanes and cycloalkanes, making it similar to petroleum jelly. It is a transparent, colorless liquid also known as liquid paraffin, white oil, or paraffin oil, especially in medical and cosmetic contexts. The term “mineral oil” refers to its source being inorganic, or mineral-based, rather than biological.
The Purification Process for Consumer Use
The mineral oil used in cosmetic, food, and pharmaceutical applications is drastically different from the crude oil from which it originates. The initial base oil fraction contains undesirable contaminants like sulfur, nitrogen, and aromatic hydrocarbons, which must be removed through meticulous, multi-stage refining. This purification process separates low-quality industrial oil from the high-purity product safe for human contact.
Refinement begins with distillation, followed by chemical and physical treatments. Key purification steps include hydrotreating, where the oil is treated with high-pressure hydrogen to remove impurities and saturate aromatic compounds. Solvent extraction is also used to remove unwanted aromatic components.
This rigorous processing ensures the removal of potentially harmful substances, such as polycyclic aromatic hydrocarbons (PAHs), which are carcinogenic in their unrefined state. The resulting highly refined product is composed of stable and inert saturated aliphatic and alicyclic nonpolar hydrocarbons. The extent of this refinement determines the final grade and intended application of the oil.
Understanding Different Grades and Applications
Mineral oil is classified into different grades that reflect its level of purity and dictate its safe use. Technical-grade mineral oil is the least refined and is primarily used in industrial settings, such as hydraulic fluids, lubricants for machinery, and heat transfer oils. This grade is not intended for human contact.
In contrast, consumer products utilize highly purified grades, such as cosmetic-grade, National Formulary (NF), and United States Pharmacopeia (USP) or British Pharmacopoeia (BP) grades. Pharmaceutical-grade mineral oil (USP/BP) undergoes the strictest refining to meet standards for ingestion and medical applications, such as laxatives and eye ointments. Cosmetic-grade oil is similarly highly refined for safe direct skin application in lotions and moisturizers. For instance, USP-grade must demonstrate purity with no aromatics and contain no cancer-linked PAHs, making it safe for direct food contact and pharmaceutical use.
Addressing Safety Concerns and Consumer Perception
Consumer anxiety often stems from the knowledge that mineral oil originates from petroleum. This concern confuses the highly refined grades with less-refined, industrial oils that may contain impurities. Regulatory bodies like the U.S. Food and Drug Administration (FDA) and the World Health Organization (WHO) have classified the highly refined mineral oils used in consumer products as safe and non-carcinogenic.
Pharmaceutical and cosmetic-grade mineral oils are chemically inert, meaning they do not easily react with other substances. They are also non-comedogenic, meaning they do not clog pores, addressing a common misconception. When applied topically, mineral oil creates a protective, non-absorbent barrier that reduces water loss without penetrating the skin’s deeper layers.