For well over a century, science and regulations have ensured the safety of petroleum products that go into consumer goods. Nowhere is this more evident than in three widely used product categories: white mineral oil, petrolatum and microcrystalline wax. During the refining process, potentially carcinogenic polycyclic aromatic hydrocarbons (PAHs) are extracted from these petroleum products. However, the same may not be true with natural oils and components.
This article presents the results of a study of PAH levels-carcinogenic and non-carcinogenic-in both refined petroleum and natural components used in consumer products such as food, cosmetics and pharmaceuticals. The study underscores the importance of regulations to ensure product safety, in both the highly regulated refined petroleum product industry and the non-regulated natural product industry.
A Brief History
Consumer products based on refined petroleum products first came on the market within years after Colonel Edwin L. Drake drilled the first oil well in Titusville, Pennsylvania, in 1859. A brief look at the history of refined petroleum products can dispel the common misperception that petroleum-based components in consumer products are not natural and are thus inherently suspect.
Hundreds of years before the drilling of the famous Drake Well, both Native Americans and Europeans had been using naturally pooled mineral oil for medicinal purposes. It was reputed by folklore as a cure for many ailments, including rheumatism and arthritis. With the extraction of large quantities of crude oil, chemists immediately began isolating novel compounds.
Among these refined petroleum products were white mineral oil, petrolatum and microcrystalline wax. These products are all refined from crude oil using physical separation and chemical purification and modification steps. Physical refinement methods include atmospheric and vacuum distillation, along with crystallization steps to separate wax and oil. Chemical purification and modification steps include propane deasphalting, solvent extractions, hydrogenation, isomerization, reaction with oleum, or through fuming sulfuric acid and adsorption filtration.
Heres a closer look at these products and their applications:
White Mineral Oil comes from base oils (aka mineral oils) that are produced in large quantities as a liquid product of petroleum refining. White mineral oil is a severely refined mineral oil specifically processed to meet pharmacopeia standards, where any potentially harmful constituents are removed. These highly refined products are hydrophobic, colorless, tasteless, odorless and chemically inert. The best-known application is baby oil, but white mineral oil is used across a wide range of product categories. It is used in food applications as a release agent, in agricultural grain de-dusting, as a polymer modifier in plastics and elastomers, as an active ingredient in pharmaceuticals, and in personal-care products as an emollient.
Petrolatum. In 1872, Robert Chesebrough patented Vaseline, and by 1880, the product was incorporated into one of the first printings of the United States Pharmacopeia. This first petrolatum product was developed by distilling and deodorizing the waxy substance that collects around the sucker rods at the oil wellhead. Today, petrolatum is also used as a food ingredient, protective coating and as a release agent. It is also used as an active pharmaceutical ingredient in skin protectants. The material is an excellent emollient, the gold standard for moisturization in skin care, and petroleum jelly is a fixture on bathroom and hospital shelves.
Microcrystalline Wax. Microcrystalline wax was first developed in 1926 by separating the solids from petrolatum. Its commercial development was limited until shortages in vital packaging materials during World War II drove the development of military applications for the wax, and production was stepped up tremendously. A research bulletin from 1947 details how, during the war, microcrystalline wax was used as a protective coating for spare parts, ammunition, paper and field rations. Denser, tackier and more elastic than paraffin waxes, microcrystalline wax is used in an extensive array of products, including tires and rubber; candles; adhesives; corrugated boards; castings, and a host of others, such as a viscosity modifier in hot-melt adhesive formulations. The USP grade is used extensively in chewing gum base and lipstick formulations.
The USP Imprimatur
When a pharmaceutical ingredient is labeled USP, what does that mean? It means the product conforms to the official standards and analytical procedures published by the nonprofit U.S. Pharmacopeia Convention (www.usp.org). USP monographs cover hundreds of drugs, drug ingredients and excipients, including USP-grade white mineral oils, petrolatum and microcrystalline waxes. Only when an ingredient meets the stipulated level of strength, quality and purity can it be labeled as USP. This enforceable, science-based standard also confirms that the material meets federal Food & Drug Administration regulations found in 21 CFR for pharmaceutical ingredients.
Over 140 countries recognize USP drug standards, and product labels also may reference the food and pharma standards of other national organizations, among them British Pharmacopoeia (BP); Germanys Deutsches Arzneibuch (DAB); the Food Chemical Codex; EU Pharmacopoeia (EUP); and Japanese Industrial Standards (JIS). All of these organizations have rigorous, enforceable standards, making them co-regulators in a sense with the FDA and other governmental bodies.
A Historic Record
To understand todays stringent regulations regarding the production and use of refined petroleum products, it is useful to review the long history of research into their safety when used in consumer products.
The first recognition that chemical exposure could cause human cancer was reported by Sir Percivall Pott in 1775. Pott noted an increased incidence of scrotal cancer among the population of men who had apprenticed as climbing boys for the chimney sweeps of London during his time. He linked the tumors to the soot that collected in the unwashed areas of the body where the tumors formed.
Studies conducted in the 1920s confirmed Potts early observations, and identified polycyclic aromatic hydrocarbons-specifically, benzo(a)pyrene, now known as the most active carcinogenic PAH ever discovered-as the chemical agent that caused the cancer.
Today, it is generally accepted that PAH molecules containing bay region protons (the space between the conjugated aromatic rings of a PAH) are more reactive and mutagenic than other PAHs. The federal Agency for Toxic Substances and Disease Registry explains that the body metabolizes these substances into an epoxy diol, which can then interact with DNA to produce adducts that promote mutations and lead to various cancers. With the discovery that these diol epoxide PAHs were cancer-causing agents, testing methods were developed to measure the concentration of different PAHs in products.
PAHs are ubiquitous in nature and found in the environment worldwide. They are produced in varying amounts whenever organic substances, plant or mineral, are burned (pyrolysis reaction). Organic substances include those comprising coal, petroleum, wood, peat and even tobacco leaves. PAHs are chemically stable and have existed in soils and marine sediments for eons.
Testing for PAH
Among the first methods to specifically test and establish limits for PAH compounds in petroleum products were UV measurements of mineral oils used in foods. Developed at the U.S. Food & Drug Administration by E.O. Haenni and M.A. Hall in the early 1960s, these measurements quantitatively correlated the UV absorbance of a product at different wavelength ranges to its PAH content.
This led to the development of extraction steps that used the solvent dimethyl sulfoxide (DMSO) to concentrate the PAHs and remove the background interference of non-PAH compounds in mineral oils. By the mid-1960s, this would enable the development of tests and establishment of the first FDA regulations on the presence of PAHs in petroleum waxes, including microcrystalline wax and petrolatum.
In the course of five years, the regulatory landscape moved from very rudimentary methods and requirements to highly sophisticated and specific analyses and restrictions on PAH content in these products. These regulatory criteria, based on extensive product and clinical testing, are in use today to evaluate the purity of the white mineral oil, petrolatum and microcrystalline waxes used in foods, pharmaceuticals and cosmetics.
The test method itself is repeatable, accurate, highly evolved, inexpensive and accepted globally as the basis for pharmaceutical regulations. It has the added advantage of not requiring extremely expensive instruments with complex calibrations. The UV spectra measured are unique to the aromatic compounds of interest.
Natural Products in Personal Care
The regulatory framework for the use of refined petroleum products is well established and stringent. There is no such regulation of natural, i.e., plant-based, products. Natural products used in personal-care applications are derived from leaves, fruit, seeds and nuts of plants, available in different grades or levels of refinement that range from extra virgin to refined, bleached and deodorized (RBD).
The various natural certifications on these materials deal only with growing and processing of the products; they do not include testing for purity or safety. The purity and safe use of these products and compounds in personal-care applications are of potential concern, due to the absence of positive controls, regulations or measurements of PAHs. Natural products with elevated PAH contents escape notice and regulation. Recent studies of PAH levels in both refined petroleum products and natural products used in personal-care products give reason for these concerns.
Comparing PAH Levels
The Biochemical Institute for Environmental Carcinogens-Prof. Dr. Gernot Grimmer Foundation in Germany has developed test methods that can measure the concentration of 28 separate PAH compounds in materials to the parts-per-billion level. These methods are recognized as some of the most sensitive evaluations available, and are also included in REACH registrations for regulated white mineral oil, petrolatum and waxes.
In one test, the BIU-Grimmer institute was provided samples of commercially available refined petroleum products for PAH analysis. The Sonneborn-branded products included Carnation and Kaydol white mineral oils; Multiwax W-445 microcrystalline wax; and Super White Protopet petrolatum. Also, because the personal-care industry has shown interest in formulating products using food-type raw materials, such as the natural substances canola oil and certified organic coconut oil, samples of these products (SonneNatural brand) were included in the evaluation for comparison and completeness.
The purpose of the testing was to identify the presence of different PAH compounds in these products, as classified by the International Agency for Research on Cancer, which groups substances according to their carcinogenic potential. The IARC classifications are shown in Table 1, on page 44.
Table 2, also on page 44, lists the results of the evaluation of both the petroleum-based and natural-based products submitted. It shows the type and quantity of PAH compounds found in the products, and the applicable IARC group classification for the carcinogenic potential of each PAH compound measured.
Analysis and Conclusion
These test results indicate that the PAH levels of petroleum-based products are well controlled, but that there is little or no control of PAH levels in natural products. This is underscored by both the total PAH and the concentrations of IARC Group 1 and 2(A+B) substances in the natural products.
This should not be surprising, as the only regulations that limit PAH levels in the U.S. Code of Federal Regulations (CFR) apply to the refined petroleum products: white mineral oil, petrolatum and microcrystalline wax. No such regulations apply to the natural products.
It is well established that petroleum-derived food- and pharmaceutical-grade white mineral oils, petrolatums and microcrystalline waxes are safe for use in personal-care products.
The same conclusion cannot be drawn for natural products, due to the lack of regulation and monitoring of the PAH levels for these substances in the United States. The data from the BIU-Grimmer study alone suggest that such regulation should deserve serious consideration.
Based in Petrolia, Pennsylvania, Timothy Yasika is regulatory manager at Sonneborn LLC, a global leader in high-purity specialty hydrocarbons for use in both consumer and industrial applications. For information about this article, email him at Tim.Yasika@Sonneborn.com