Some science behind the scenes
Potassium bromate is typically used in the United States as a flour improver (E number E924). It acts to strengthen the dough and to allow higher rising. It is an oxidizing agent
If too much is added, or if the bread is not baked long enough or not at a high enough temperature, then a residual amount will remain, which has proven to be harmful if consumed. Potassium bromate might also be used in the production of malt barley, for which application the U.S. Food and Drug Administration (FDA) has prescribed certain safety conditions, including labelling standards for the finished malt barley product. It is a very powerful oxidizer (E° = 1.5 volts, comparable to potassium permanganate).
Potassium bromate is classified as a category 2B carcinogen (possibly carcinogenic to humans) by the International Agency for Research on Cancer (IARC).
It has been banned from use in food products in the European Union, Argentina, Brazil, Canada, Nigeria, South Korea, Peru and some other countries. It was banned in Sri Lanka in 2001, China in 2005, and India on 20 June 2016.
In the United States of America, it has not been banned.
The FDA sanctioned the use of bromate before the Delaney clause of the Food, Drug, and Cosmetic Act—which bans potentially carcinogenic substances— went into effect in 1958. But since 1991 the FDA has urged bakers to voluntarily stop using it. In California a warning label is required when bromated flour is used.
Japanese baked goods manufacturers stopped using potassium bromate voluntarily in 1980; however, Yamazaki Baking resumed its use in 2005, claiming they had new production methods to reduce the amount of the chemical which remained in the final product.
Environ Health Perspect. 1990 Jul;87:309-35. Toxicity and carcinogenicity of potassium bromate--a new renal carcinogen. Kurokawa Y1, Maekawa A, Takahashi M, Hayashi Y. Division of Toxicology, National Institute of Hygienic Sciences, Tokyo, Japan.
Potassium bromate (KBrO3) is an oxidizing agent that has been used as a food additive, mainly in the bread-making process. Although adverse effects are not evident in animals fed bread-based diets made from flour treated with KBrO3, the agent is carcinogenic in rats and nephrotoxic in both man and experimental animals when given orally. It has been demonstrated that KBrO3 induces renal cell tumors, mesotheliomas of the peritoneum, and follicular cell tumors of the thyroid. In addition, experiments aimed at elucidating the mode of carcinogenic action have revealed that KBrO3 is a complete carcinogen, possessing both initiating and promoting activities for rat renal tumorigenesis. However, the potential seems to be weak in mice and hamsters. In contrast to its weak mutagenic activity in microbial assays, KBrO3 showed relatively strong potential inducing chromosome aberrations both in vitro and in vivo. Glutathione and cysteine degrade KBrO3 in vitro; in turn, the KBrO3 has inhibitory effects on inducing lipid peroxidation in the rat kidney. Active oxygen radicals generated from KBrO3 were implicated in its toxic and carcinogenic effects, especially because KBrO3 produced 8-hydroxydeoxyguanosine in the rat kidney. A wide range of data from applications of various analytical methods are now available for risk assessment purposes.
PMID: 2269236 ; PMCID: PMC1567851