Potassium Bromate (Bromated Flour)
Last reviewed October 18, 2026 · Evidence strength: Limited · How we grade evidence
In plain words: Potassium bromate is sometimes added to flour to make bread rise higher. It causes cancer in lab animals, many countries don't allow it, and California bans it starting in 2027. Proper baking should break most of it down, but "bromated flour" on a label is an easy thing to avoid.
Also listed on labels as: Potassium bromate, Bromated flour, Bromated wheat flour, E924
What is it, and why is it in food?
Potassium bromate strengthens dough so bread rises higher and has a finer crumb. It's supposed to break down into harmless bromide during baking, but leftover amounts depend on the recipe and baking time. It's used in some buns, rolls, bagels and frozen sandwiches.
What does the science say?
| The popular claim | "Bromated flour is a carcinogen banned elsewhere." (A common claim; we didn't find it in the five experts' own pages.) |
| Our verdict on that claim | Supported |
| Evidence strength | Limited: consistent animal cancer evidence and regulator action; no human data. |
| Kinds of studies | Animal studies, IARC classification, reviews, state law |
- Animals: Potassium bromate caused kidney tumors in rats in classic studies,1 and thyroid tumors too. Reviews confirm it's carcinogenic in rodents and that leftover bromate can remain in baked goods.2
- IARC: possibly carcinogenic to humans (Group 2B).3
- People: human data are lacking; a 2026 review mentions only "possible" links with digestive cancers.4
What do regulators say?
- California bans it in food from January 1, 2027.5
- FDA still permits it.
- It's not permitted in the EU, UK and Canada, according to common reporting (we didn't re-check each country's rules).
Who should be careful?
- Everyone can easily skip it, especially kids, who eat more bread for their size.
How common is it in US foods?
In our check of USDA's Branded Foods database, 606 of 438,129 US packaged foods with an ingredient list name potassium bromate or bromated flour (about 0.1%, or roughly 1 in 723).6 It shows up most often in: breads & buns (152); cookies & biscuits (65); frozen appetizers & hors d'oeuvres (63); prepared subs & sandwiches (48); pizza (43). These are label records companies sent to USDA, mostly in 2021 to 2023, so some products have changed since. Counts come from a text match of ingredient lists and are approximate.
Swaps and tips for families
- Look for "unbromated flour" or simply no bromate on bread and bun labels.
- Most major bread brands don't use it; it's more common in some rolls, buns and frozen sandwiches.
Beyond the plate: related non-food exposures
Bromate also forms as a byproduct when drinking water is disinfected with ozone. Public water systems regulate it.
Frequently asked questions
Is potassium bromate banned in the US?
Not nationally. California bans it in food from January 1, 2027, and FDA still permits it.
Does baking remove potassium bromate?
Baking should break most of it down, but leftover amounts depend on how the bread is made.
What does unbromated flour mean?
It means the flour wasn't treated with potassium bromate. That's the one you want.
Related guides
- Azodicarbonamide (ADA)
- Calcium Propionate
- Brominated Vegetable Oil (BVO)
- Flavors, flour treatments and more
Sources
Every source below was checked against PubMed, the publisher or the official page by our research team in October 2026.
- Toxicity and carcinogenicity of potassium bromate--a new renal carcinogen. Environmental health perspectives, 1990. PubMed 2269236 · doi:10.1289/ehp.9087309
- Potassium bromate: Effects on bread components, health, environment and method of analysis: A review. Food chemistry, 2020. PubMed 31865111 · doi:10.1016/j.foodchem.2019.125964
- Potassium bromate (IARC Monographs vol. 73). IARC Monogr Eval Carcinog Risks Hum, 1999. PubMed 10804966
- Potassium bromate as a probable human Carcinogen: multi-organ toxicity and chemopreventive potential of dietary antioxidants-a comprehensive review. Mutagenesis, 2026. PubMed 42172136 · doi:10.1093/mutage/geag022
- California Health & Safety Code 109025 (AB 418). Link
- FoodData Central, Branded Foods dataset (release 2026-04-30). U.S. Department of Agriculture, Agricultural Research Service, 2026. Link
This guide is for general education. It is not medical advice and does not replace advice from your doctor, pediatrician, allergist or registered dietitian. If you think you or your child reacted to a food, talk to a health professional. Research changes; we review these pages when new evidence or rules come out. Last reviewed October 18, 2026. Spotted an error? Email [email protected].