EWG’s recommendation
Avoid or limit foods containing potassium bromate.
Potassium bromate has been classified as a possible carcinogen by the World Health Organization’s cancer research agency, based on evidence of kidney and thyroid tumors in animals. Potassium bromate is intended to convert to potassium bromide during baking, but some residual potassium bromate may remain in finished products.
What is potassium bromate?
Potassium bromate is used as a dough strengthener, flour treating agent and oxidizing agent. It strengthens gluten, improves dough elasticity and helps bread rise more consistently, producing a higher-volume loaf.
Which foods contain potassium bromate?
Potassium bromate is added to some flour and dough used to make bread products, including hamburger buns, sandwich bread, rolls, tortillas, pastries and crackers.
Look for potassium bromate in product ingredient lists, usually below or next to the Nutrition Facts panel, on the back of the package. It may also appear as “bromated flour” on ingredient labels.
How is potassium bromate regulated?
The Food and Drug Administration is responsible for overseeing food additives and other ingredients. Potassium bromate entered the U.S. food supply before the 1958 Food Additives Amendment established the modern additive approval process, so it was never required to undergo full premarket safety review.
It remains permitted in bread, rolls and buns at up to 75 parts per million of flour weight. In 2024, the FDA identified potassium bromate as a priority additive for safety reassessment.
The WHO cancer research agency has classified potassium bromate as possibly carcinogenic to humans. It has been banned from food in the EU, U.K., Canada, Brazil, China, South Korea and many other countries.
Since 1990, potassium bromate has been on California’s Proposition 65 list of chemicals known to cause cancer. The state will prohibit potassium bromate in food starting in 2027. Arkansas enacted a ban in 2025, which will go into effect in 2028. New York has passed legislation, which awaits the governor’s signature, and numerous other states have introduced similar bills.
Potassium bromate is prohibited in certified organic foods under Agriculture Department organic standards, which bar synthetic substances.
What does the science say about potassium bromate?
When bread bakes, heat is supposed to convert potassium bromate into potassium bromide, a less-harmful compound. But if baking times are too short, temperatures too low, or dough too thick, that conversion is incomplete – leaving residual potassium bromate in the finished product.
The kidney is the primary vulnerable organ: Long-term animal studies found significant increases in kidney tumors in rats, along with other tumors in the lining of the abdomen and, in some studies, the thyroid gland.
Laboratory and animal studies show that potassium bromate can cause oxidative stress – a buildup of reactive molecules that can damage cells – as well as DNA breaks and chromosomal damage.
Research has also found that potassium bromate can damage DNA through a distinct mechanism, generating reactive intermediates that cause specific DNA lesions. Those lesions can contribute to mutations.
Direct evidence of harm in humans is limited, and research about exactly how potassium bromate causes cancer is ongoing.
Find out more
Learn more about recommendations relating to potassium bromate – and the full EWG Dirty Dozen™ list of food chemicals – on EWG’s research page.
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