Heinz confirmed that it uses very small amounts of bisphenol A to line the lids of cans fitted with ring-pull openers, including baked bean cans. The chemical helps to prevent such tins from corroding or releasing tin into the food.
Bisphenol A and most other endocrine disrupting chemicals are known toxins at high levels. The argument is about whether or not they are dangerous in very low levels, when they are known as micropollutants.
Heinz says it accepts that tiny amounts of bisphenol A may leach into its foods, but says levels are far below what is needed to cause any biological effect. "The levels are in parts per million or parts per billion, so small as to be almost undetectable," said a spokesman.
Tin cans are just one of many potential sources of bisphenol A. The metal is also used in soft plastics, pesticides, dental products and some baby bottles.
A 1999 study
by American researchers found that bisphenol A could mimic the sex hormone estradiol.
Mice exposed before birth to the chemical, in amounts correlating with typical
human exposures, suffered changes in postnatal growth and early puberty in females.