Potassium Bromate (E924a): The Carcinogen In Your Daily Bread

TL;DR

Potassium Bromate (E924a) is an oxidizing agent used to bleach flour and strengthen gluten in dough, leading to cheaper, higher-rising bread. It is classified as a Category 2B carcinogen (possibly carcinogenic to humans) and is banned in the EU, UK, Canada, Brazil, and China. In the US, it is still legal. Kale rates it as Avoid (Red).

What is Potassium Bromate (E924a)?

Potassium Bromate is an odorless white crystalline powder. In the baking industry, it acts as a "flour improver."

When added to flour, it strengthens the gluten network, allowing pockets of gas to hold their shape better. This results in bread that rises higher, has a uniform texture, and stays white.

Where is it found?

It is almost exclusively found in refined flour products.

• Commercial Bread: Sliced white bread, hamburger buns, and hot dog buns.
• Pizza Crusts: Especially frozen or fast-food pizza dough.
• Pastries: Donuts, cookies, and heavily processed bakery items.
• Bagels: Some supermarket bagel brands.
• Flour: Some brands of "bromated" all-purpose or bread flour sold for home baking.

Health Concerns

1. Cancer Risk

This is the single reason why most of the world has banned it. In 1982, Japanese researchers discovered that potassium bromate causes thyroid, kidney, and other cancers in rats and mice. The International Agency for Research on Cancer (IARC) classifies it as a Category 2B carcinogen.

The argument for keeping it legal in the US is that the baking process should convert all the bromate into harmless bromide. However, testing has shown that if bread is not baked long enough or at a high enough temperature, or if too much additive is used, residual bromate remains in the finished product.

2. Kidney Toxicity

In addition to cancer risk, high levels of bromate ingestion can be toxic to the kidneys and cause hearing loss. While these acute effects are rare from bread consumption, the potential for long-term, low-level toxicity remains a concern.

Kale's Verdict: Avoid (Red)

Kale rates E924a (Potassium Bromate) as Avoid (Red).

The fact that it is banned in Canada, Europe, and China should be a massive warning sign. The risk is simply unnecessary. "Better" looking bread is not worth a potential cancer risk, however small.

California requires a cancer warning label on products containing potassium bromate (Prop 65), which has led many national brands to phase it out—but not all.

How to Avoid It

1. Read the Ingredients: Look specifically for "Potassium Bromate" or "Bromated Flour."
2. Scan with Kale: We'll flag this red alert instantly.
3. Check the "Unbleached" Label: Unbleached flour is rarely bromated.
4. Shop at Whole Foods: Whole Foods Market (and similar health-conscious chains) bans potassium bromate from all products they sell.

Final Thoughts

Potassium Bromate represents the worst kind of food additive: one that benefits the manufacturer (cheaper, faster production) while passing all the risk onto the consumer. There are safer ways to make bread rise.

Don't gamble with your toast. Download Kale to keep carcinogens out of your breakfast.