Potassium bromate

Potassium bromate has been used as a bread improver (flour maturing agent) since the early 20th century — it oxidizes gluten proteins, strengthening the dough structure and producing whiter, higher-rising bread [1]. When used correctly, it is theoretically fully reduced to bromide during baking and no residual bromate remains in the finished bread [2]. However, improperly baked or thicker breads may retain residual bromate [1]. Canada banned potassium bromate as a food additive in 1994; the EU, Brazil, and many other countries have also banned it. The FDA in the United States classifies it as GRAS (Generally Recognized As Safe) under proper use conditions but has not banned it, despite an EPA carcinogenicity classification [2]. Potassium bromate is also used in hair permanents (as a neutralizer) and in malt production [1].

Dietary exposure from commercially baked bread and baked goods made with bromated flour [1]. Hair permanent users have dermal exposure to bromate neutralizer solutions [2]. Industrial exposure in chemical oxidation processes where potassium bromate is used as an oxidant [1].

Bromate ion (BrO₃⁻) is the active toxicant — it is reduced in vivo by cellular reductants to generate reactive oxygen species (specifically, hydroxyl radical and bromine-containing radicals) that cause oxidative DNA damage [1]. In animal studies, potassium bromate induced renal cell carcinomas, thyroid follicular cell tumors, and peritoneal mesotheliomas in rats. EPA classifies it as a Group B2 probable carcinogen; IARC Group 2B [2]. The kidney is the primary target organ — renal tubular cells are most exposed as the kidney concentrates and excretes bromate [1].

Consumers of bromated bread — primarily in the United States where bromated flour is still permitted [1]. Hair salon workers and clients using bromate-containing permanent wave neutralizers [2]. Industrial workers using potassium bromate as an oxidant [1].

1. Look for 'unbromated flour' on bread labels in the United States — artisan bakeries and organic bakers typically use unbromated flour [1]. 2. Bread from California is safer — California requires a cancer warning label on bromated bread, leading most California bakers to avoid it [2]. 3. Ascorbic acid (vitamin C) can substitute for bromate as a flour improver and is used throughout Europe [1]. 4. Hair salons should use thioglycolate-based permanents instead of bromate neutralizers [2].