Potassium Bromate: Banned in 1990, Still in US Bread

I spend a lot of my time on this site talking people down: explaining that the dye isn’t poisoning their kids, that the lawsuit proved nothing, that “banned in Europe” usually means “restricted, not banned.” So I want to be clear about this one from the top: potassium bromate is the case where the alarmed instinct is basically right.

It’s a flour additive. Europe banned it in 1990. So did the UK, Canada, Brazil, Argentina, South Korea, Peru, Nigeria, and more: somewhere north of 40 countries. The cancer data in animals is reproducible and the mechanism is understood. And in the United States, it is still legal in bread today, where the FDA’s strongest action in 35 years has been to ask bakers, nicely, to please stop using it.

This is the clean one. Here’s why.

What potassium bromate does

Potassium bromate (KBrO₃) is a powerful oxidizing agent used as a flour improver. Added to dough, it strengthens the gluten network, lets the bread rise higher and faster, and produces a whiter crumb and a more uniform loaf. For an industrial baker running high volumes, it’s a genuinely useful tool: cheap, effective, and fast. That’s why it ever caught on, and why some bakers were reluctant to give it up.

The theory under which it was deemed acceptable is specific and testable: potassium bromate is supposed to be fully consumed during baking, converting to harmless potassium bromide by the time the loaf comes out of the oven. If that conversion were complete every time, the finished bread would contain no bromate, and the safety question would mostly evaporate.

It isn’t always complete. That’s the crux.

The science: solid, and pointing one way

The carcinogenicity data come from animal studies, and unlike some additives where the rodent finding is a quirky species artifact, here it’s broad and mechanistically coherent.

The International Agency for Research on Cancer, the WHO’s cancer arm, evaluated potassium bromate in 1999 and classified it Group 2B, “possibly carcinogenic to humans.” IARC found inadequate evidence in humans but sufficient evidence in experimental animals. (IARC monograph, NCBI.) In rats, bromate produced renal (kidney) tubular tumors and thyroid follicular tumors in both sexes, plus peritoneal mesotheliomas in males. (IARC.)

The mechanism matters because it’s what separates this from a story like Red Dye 3, where the rat tumors run through a hormonal pathway humans don’t share. IARC concluded that potassium bromate causes kidney tumors “through a mechanism involving oxidative damage”: bromate generates reactive oxygen species that damage DNA directly. (IARC.) Oxidative DNA damage is not a rat-specific quirk; it’s a mechanism with obvious human relevance. That’s why this finding carries more weight than a forestomach or rat-thyroid result.

Is there direct human cancer evidence from dietary bromate? No, and I won’t pretend otherwise. The human data are “inadequate,” which is why it’s Group 2B (possible) rather than Group 1 (known). But the combination of a plausible, non-species-specific mechanism, reproducible animal tumors across multiple organs, and a completely avoidable exposure with no consumer benefit is exactly the profile where precaution is cheap and sensible. There is no nutritional reason to eat bromate. The only beneficiary is the baker’s process.

What Europe did, and when

The European position is old and unambiguous. The EU’s Scientific Committee for Food concluded potassium bromate should not be used as a flour treatment agent, and it was prohibited across the bloc; the UK made it illegal in flour from 1 April 1990. (BakeryandSnacks.) Canada followed in 1994. Today it’s banned in more than 40 countries.

For the current legal status in plain terms, and how to read a flour label, the potassium bromate ingredient page is the quick-answer version. Note that a related dough conditioner, azodicarbonamide, follows a similar EU-banned/US-permitted pattern, and the trans-fat story (partially hydrogenated oils) is another case where the US eventually moved but took its time.

What the US did: almost nothing, for 35 years

Here is the part that genuinely bothers me.

The FDA never banned potassium bromate. Under 21 CFR 136.110, it remains a permitted dough conditioner in bread, rolls, and buns at up to 0.0075 parts per 100 parts of flour, or 75 ppm. (Wikipedia summary of the CFR provision; Policy Canary.) Since 1991, the agency’s posture has been to encourage bakers to voluntarily discontinue use. (CRIS, Michigan State University.)

Encourage. Not require. For 35 years.

In fairness, and this site lives on fairness, that voluntary approach has worked better than “still legal” implies. Many large industrial bakers quietly stopped using bromate years ago, partly because the residual-bromate problem creates real liability and partly because consumer-facing brands didn’t want it on the label. So the practical American exposure is lower than the legal status suggests. The honest framing isn’t “every American loaf is full of bromate.” It’s “the US still permits a Group 2B carcinogen in bread that essentially the entire developed world banned, and relies on bakers to opt out rather than requiring it.”

The official defense, that bromate converts to harmless bromide during baking, is the weak link. Measurements have repeatedly found residual bromate in finished bread, particularly when baking time, temperature, or dough conditions don’t drive the reaction to completion. The conversion is real but not reliable, which is exactly why a regulator that takes the precautionary view bans the input rather than trusting the process. The federal posture here is inertia, not science.

The fresh hook: California’s AB 418

The thing that’s finally forcing the issue isn’t the FDA. It’s California.

The California Food Safety Act (AB 418), signed in October 2023, prohibits the sale of food containing four additives (potassium bromate, brominated vegetable oil, propylparaben, and Red Dye 3) effective 1 January 2027. (Food Safety Magazine; bill text.) The bill’s author and Governor Newsom both cited the EU’s existing bans as part of the rationale.

Because California is too large a market to reformulate around, AB 418 functions as a de facto national standard: manufacturers tend to change the recipe everywhere rather than run a separate California product line. So the most likely path by which potassium bromate finally leaves American bread isn’t a federal ban. It’s a state law, citing Europe, dragging the national supply along with it. (Note: of AB 418’s four targets, Red Dye 3 was independently pulled by the FDA in 2025, and BVO was revoked federally in 2024. Bromate and propylparaben are the two where California is genuinely out ahead.)

So what do you actually do?

For most people, very little, because the exposure is already modest and shrinking. But if you want to skip it entirely, it’s easy and free:

• Read the flour label. US ingredient lists name it directly: “potassium bromate,” or flour described as “bromated.” Many bags now advertise “unbromated” as a selling point.
• Bread labels too. Bromate, if present, will be in the ingredient list.
• You don’t need to panic about a sandwich. This is a “choose unbromated when you can,” not a “the bread you ate is dangerous” situation. The risk is a long-term, dose-dependent, avoidable one, not an acute hazard.

The reason I’m comfortable being more direct here than on most pages is that the cost of avoiding bromate is essentially zero. There’s no flavor you’re giving up, no nutrient, no benefit at all: just a baker’s processing aid that the rest of the developed world decided wasn’t worth the risk a generation ago.

The takeaway

Potassium bromate is the strongest entry in the whole “banned in Europe” canon: a flour additive with reproducible, mechanistically credible animal carcinogenicity, banned across Europe since 1990 and in 40-plus countries, still legal in US bread at 75 ppm under a regulation the FDA has spent 35 years “encouraging” people not to use. The “it bakes out” defense doesn’t hold up; residual bromate turns up in finished bread. The realistic fix is California’s AB 418, taking effect in 2027 and likely to clear it from the national supply by market gravity. If you want to avoid it, buy unbromated flour and bread. It costs you nothing, which is the whole point.

For the bigger picture on why the EU and US keep landing in different places on additives like this one, see Why do I feel better in Europe?