Potassium bromate has the chemical formula KBrO3, which consist of potassium, bromine and oxygen atoms, all joined chemically together as a compound by a strong ionic bond. It has the melting point of 350 C and decomposes at 370 C (Guideline, 1996). Owing to its polarity, it is soluble in water and highly stable atroom temperature. It is a white crystalline substance, odourless and has a hard texture.
Economic importance of potassium bromate
n Potassium bromate is used as an oxidizing agent, food additive (maturing flour and dough conditioner in milling and baking, manufacturing cheese and malting beer).
n It is used to fracture concrete in combination with aluminium and dinitrotluene.
n Its also used as a brominating agent in the synthesis of chemical compounds.
HISTORICAL ANALYSIS OF POTASSIUM BROMATE
A number of case reports on potassium bromate have been evaluated by many health organizations. For instance, potassium bromate has been tested by oral administration in several studies in rats and in one study each in mice and hamsters (IARC, 1997). In rats, it produced renal tubular tumors (Adenomas and carcinomas) and thyroid follicular tumor in animals of each sex and peritoneal mesotheliomas in males. In mice, it produced a low incidence of renal tubular tumors in males. In hamsters, the incidence of renal tumors was marginally increased.
In 1996, guideline reported that male Wister rats exposed to 0.4% potassium bromate in drinking water (approximately 30mg of bromate per kg body weight per day) for up to 15months, Effects were marked inhibited body weight gain in all exposed animals, karyepykaotic foci in tubules of the inner kidney medulla, increased blood urea nitrogen (BUN), and marked structural abnormalities of the cortical tubules.
Guideline in 1996 reported that most cases of human poisoning from bromate are due to the accidental or intentional ingestion of home permanent name solution which contains 2-10% of bromate. Furthermore, serious poisonings have been reported in children following ingestion of 60-120mls of 2% potassium bromate (equivalent to 46-96mg of bromate per kg of body weight per day for a 20kg child).
Lethal dose of potassium bromate are estimated to be 200-500mg/kg of body weight (154-385mg of bromate per kg of body weight). (Mark, et al., 2005) on a further study found that the toxic effect of bromate in human beings include nausea, vomiting, abdominal pain, diarrhea, varying degree of central nervous system depression, seizures, respiratory depression and pulmonary oedema, most of which are reversible. Irreversible effects include renal failure and deafness both of which have been observed following the ingestion of 240-500mg of potassium bromate per kg of body weight (185-385mg of bromate per kg of body weight).
Provisional guideline value by the Joint Expert Committee on Food Additives (JECFA) evaluated bromate and recommended that there should be no residues in food when bromate is used in food processing. On a follow up, it was concluded that there is sufficient evidence for the carcinogenicity of potassium bromate in animals (IARC, 1986). Eventually the classified bromate under they umbrella of Group 2B (possible human carcinogens).
The world health organization 33rd report of the FAO/WHO Expert on Food Additives which came out in 1989 entitled, “Evaluation of certain food additives and contaminants” directed that bromate should not be used in foods consumed. This led to the ban of bromate salts by several nations like Canada, California after their proposition 65 in September 1, 1996. Nigeria imposed the ban in 1993 by the Food and Drug Administration (FDA) and later in 2001 by National Agency for FOOD and Drug Administration and Control (NAFDAC).