It is typically used as a flour improver (E number E924), strengthening the dough and allowing higher rising. It is an oxidizing agent, and under the right conditions, will be completely used up in the baking bread. However, if too much is added, or if the bread is not cooked long enough or not at a high enough temperature, then a residual amount will remain, which may be harmful if consumed. Potassium bromate might also be used in the production of malt barley where the United States FDA has prescribed certain conditions where it may be used safely, which includes labeling standards for the finished malt barley product. It is a very powerful oxidizer (E° = 1.5 volts comparable to potassium permanganate). Bromate is considered a category 2B (possibly carcinogenic to humans) carcinogen by the International Agency for Research on Cancer (IARC).
Potassium bromate has been banned from use in food products in Europe, as well as the United Kingdom in 1990, and Canada in 1994, and most other countries. It was banned in Sri Lanka in 2001 and China in 2005. It is also banned in Nigeria, Brazil and Peru.
In the United States it has not been banned. The FDA sanctioned the use of bromate before the Delaney clause of the Food, Drug, and Cosmetic Act went into effect in 1958 — which bans carcinogenic substances — so that it is more difficult for it to now be banned. Instead, since 1991 the FDA has urged bakers to voluntarily stop using it. In California a warning label is required when bromated flour is used.