Potassium bromate linked to kidney tumours in rats
What it found
In rats, potassium bromate caused kidney tumours, tumours of the peritoneum and thyroid, and kidney damage.
In people, case reports show kidney damage and deafness after swallowing large amounts.
What they found
Studies in people
Kidney damage in people
Case reports of people who swallowed potassium bromate, often from permanent wave kits, describe vomiting, diarrhoea, kidney failure, and deafness. In reported cases, 9 out of 24 adults died 3 to 5 days after taking it.
Animal and lab studies
Kidney tumours in rats
In rats given potassium bromate in drinking water for up to 110 weeks, kidney tumours (renal cell tumours) increased significantly. The tumours appeared at doses of 125 ppm and above, and were more common in males.
Other tumours in rats
Rats also developed mesotheliomas of the peritoneum and follicular cell tumours of the thyroid. These were seen at higher doses, mainly 250 and 500 ppm.
Weak effects in mice and hamsters
Mice and hamsters given potassium bromate in drinking water developed some kidney tumours, but far fewer than rats. The authors say the potential seems weak in these species.
Bread-based diets
Animals fed bread made from flour treated with potassium bromate at levels up to 200 ppm showed no ill effects in short studies. Long-term feeding of bread from flour treated with 50 or 75 ppm also found no dose-related increase in tumours.
How it may act
In lab tests, potassium bromate caused chromosome damage and produced active oxygen radicals. It also acted as both an initiator and a promoter of kidney tumours in rats.
What the authors conclude
- They conclude that clear evidence exists that when potassium bromate is given orally in drinking water, it is carcinogenic in rats of both sexes.
- They note that the International Agency for Research on Cancer concluded there is sufficient evidence for carcinogenicity in experimental animals, but no data on carcinogenicity to humans.
- They state that the potential seems to be weak in mice and hamsters.
How it was done
Potassium bromate was chosen for testing because it was widely used as a food additive in bread-making and had shown positive results in mutagenicity tests. The authors wanted to understand how it might cause cancer.
The authors reviewed their own laboratory studies and other published research. These included long-term feeding studies in rats, mice and hamsters, tests in newborn animals, and studies of how it might promote tumours. They also looked at case reports of human poisoning.
What it can’t tell you
- These are mostly animal studies. They can't show what happens in people who eat bread made with potassium bromate.
- The human data come from case reports of people who swallowed large amounts by accident or on purpose, not from studies of typical dietary exposure.
- The paper does not provide information on the risk from the very low levels of potassium bromate that might remain in bread after baking.
Who paid
- Authors work at
- National Institute of Hygienic Sciences, Japan
The paper
- Title
- Toxicity and carcinogenicity of potassium bromate--a new renal carcinogen
- Type
- ReviewThe authors read earlier studies and describe what they found. It isn’t a new study.
- Evidence
- Studies in people · animals · lab
- Summarised from
- Full text
- Cite
- Kurokawa Y, Maekawa A, Takahashi M, Hayashi Y (1990). Toxicity and carcinogenicity of potassium bromate--a new renal carcinogen. Environmental health perspectives. doi:10.1289/ehp.9087309Free full textPubMed 2269236DOI
Summary written 26 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error