Mineral Oil vs Potassium Bromate: which is worse?

What is Mineral Oil?

Mineral oil (E905) is a refined petroleum product used as a food-grade lubricant, coating agent, and glazing agent in food processing and production. Food-grade mineral oil is a highly refined grade of petroleum distillate with specifications limiting impurities. It differs from pharmaceutical-grade (Vaseline) and cosmetic-grade mineral oils in refinement level.

What is Potassium Bromate?

Potassium bromate (KBrO3) is an oxidizing agent used in commercial bread baking as a flour maturing agent and dough conditioner. It strengthens gluten networks, improves dough elasticity, and produces a more uniform, light-textured baked product. It is a white crystalline powder.

Documented risks

Mineral Oil: EFSA has raised significant concerns about mineral oil hydrocarbons (MOH) contamination in food through two pathways: (1) deliberate food-grade mineral oil use in coatings and processing, and (2) migration from recycled paper and cardboard food packaging into food. MOH comprises two types: mineral oil saturated hydrocarbons (MOSH), which accumulate in human adipose tissue, liver, and spleen, and mineral oil aromatic hydrocarbons (MOAH), which include polycyclic aromatic hydrocarbons (PAHs) that are potentially carcinogenic. A 2011 Swiss study found mineral oil hydrocarbons in human liver and spleen samples from autopsy, demonstrating real bioaccumulation. EFSA's 2023 preliminary opinion identified MOAH contamination in food as a safety concern that cannot be dismissed, recommending ALARA (as low as reasonably achievable) minimization. Untreated and mildly treated mineral oils are IARC Group 1 human carcinogens for occupational inhalation. Highly refined food-grade mineral oil (E905) is not classified as a direct carcinogen, but MOAH contamination in even food-grade mineral oil is an ongoing concern.

Potassium Bromate: Potassium bromate is classified by the International Agency for Research on Cancer (IARC) as Group 2B — a possible human carcinogen — based on sufficient evidence in animals. This classification was formalized in 1999. The landmark toxicology study is Kurokawa et al. (1990), published in Environmental Health Perspectives (PMC1567851), which demonstrated that KBrO3 induces renal cell tumors (kidney cancer), mesotheliomas of the peritoneum, and follicular cell tumors of the thyroid in rats. Importantly, the researchers demonstrated KBrO3 is a complete carcinogen — it possesses both tumor-initiating and tumor-promoting activities for renal tumorigenesis. The mechanism of carcinogenicity involves generation of reactive oxygen species, particularly hydroxyl radicals and superoxide radicals. These radicals cause oxidative DNA damage, specifically 8-hydroxydeoxyguanosine (8-OHdG) formation in rat kidney cells — a well-characterized biomarker of oxidative DNA damage. California declared potassium bromate a known carcinogen under Proposition 65 in 1991, requiring cancer warning labels on California products containing it. Multiple advocacy organizations including CSPI (1999 petition) and EWG (2015 petition) have petitioned the FDA for a federal ban. As of 2025, the FDA has urged voluntary industry elimination since the early 1990s but has not issued a formal ban. Nephrotoxicity from high-dose potassium bromate is well documented in case reports of accidental or intentional poisonings: it causes irreversible renal tubular necrosis, permanent deafness (cochlear damage), and blindness (optic nerve damage). These effects occur at doses far above food consumption scenarios but demonstrate the compound's acute toxicological potency. FDA testing in 1999 found residual potassium bromate above expert-recommended safe limits in more than half of 17 tested bread and roll products, demonstrating that the 'it bakes off completely' argument does not always hold in commercial practice.