whole grain bread
The study reported in JAMA Internal Medicine found that whole grains slashed the risk of dying by 15 percent. The results were highly significant in heart disease.Mattie Hagedorn/Flickr

You may have to think twice before eating a loaf of bread from even a well-established brand. A new study conducted by the Delhi-based non-profit organisation, Centre for Science and Environment (CSE), has shown that 84 per cent of the samples of bread and other bakery products collected from Delhi had residues of potassium bromate, potassium iodate or both.

Potassium bromate and potassium iodate have been banned as food ingredients in many countries following the studies that revealed these chemicals as carcinogenic. Potassium iodate can also lead to a higher intake of iodine, which can potentially affect thyroid function.

However, the Indian food regulating authority allows the use of both these chemicals as flour treatment agents in breads.

Potassium bromate also helps achieve high rising and a uniform finish in bread, according to the study. 

In order to test the presence of these hazardous chemicals in bread, the CSE's Pollution Monitoring Laboratory collected 38 samples of bread and other bakery products from retail shops, bakeries and fast food outlets in Delhi during May-June 2015.

The survey found that 32 out of 38 samples (84 percent) contained potassium bromate and/or iodate in the range of 1.15–22.54 ppm (parts per million). It further said that all the samples of white bread, pav, bun and ready-to-eat pizza bread were found to contain both the chemicals. "19 of 24 samples or 79 per cent of bread and about 75 per cent of ready-to-eat burger bread also tested positive for the chemicals," according to the study.

The highest level of potassium bromate and iodate was found in sandwich bread. This was followed by pav, bun and white bread. Some popular brands of breads, such as Perfect Bread, Harvest Gold and Britannia were found to contain high to average levels of potassium bromate and/or iodate. Harvest Gold Sandwich bread had the highest concentration of the chemicals, the study found.

The products, including pizzas and burgers, of seven popular fast food outlets, such as KFC, McDonald's, Domino's and Nirula's, tested positive for the chemicals. However, their levels were lower than the ones found in bread, pav and bun, according to the study.

In 1986, the International Agency for Research on Cancer (IARC), associated with the World Health Organization (WHO), stated that there was sufficient evidence to show the carcinogenicity of potassium bromate. The chemical, according to the findings, caused renal tubular tumours (adenomas and carcinomas), and thyroid follicular tumours in laboratory animals. IARC later acknowledged that human exposure to potassium bromate could occur due to its use as a dough conditioner and classified it as Class 2B which means possibly carcinogenic (cancer-causing) to humans, according to the study.