Scientists have discovered that a huge range of everyday foods contain potentially dangerous levels of a cancer-causing toxin. Is this just another food scare, or should we be worrying about acrylamide?

What is acrylamide?

It is a chemical that is widely used in industry, particularly in the manufacture of plastics. Highly toxic, it has been shown to cause nerve damage in humans, and has been linked to infertility. The US Environmental Protection Agency lists acrylamide, which causes tumours in rats, as a "probable" human carcinogen, and has limited the maximum permitted level in American drinking water to 0.5 parts per billion. In Europe, the permitted level for acrylamide left on food from packaging is no more than ten parts per billion.

How does acrylamide get into food?

Nobody really knows, but tests suggest that it is the cooking process, rather than the food itself, that is responsible. The chemical, which is not present in raw produce, seems to be generated whenever certain foods are baked, microwaved, fried or grilled at temperatures above 120C. The longer food is cooked at high temperatures, the higher the acrylamide content is likely to be. "I would say that boiling is the only safe cooking method," says Dr Margareta Tornqvist, the Swedish scientist who first alerted the world to the danger.

Is all baked and fried food equally contaminated?

By no means. Deep-fried or fast foods seem to have the highest levels of acrylamide: sauteed spinach was found to have 112 parts per billion (ppb); chips 736ppb; deep-fried beetroot 890ppb and potato crisps 4,000ppb. The substance has also been found in relatively high levels in crackers, Ryvita, some breakfast cereals and in low levels in bread. Protein-rich foods such as chicken and beef seem to produce only moderate levels of acrylamide when heated. However, the Swedish Food Administration has advised diners to avoid heavily charred and burnt meat. There is no definitive list of which foods produce acrylamide because many have yet to be tested.

How serious is this scare?

It depends who you talk to. The food industry is naturally keen to play down the findings, but scientists seem to be taking it pretty seriously. "It is likely that this is causing cancer in the human population," Dr Jorgen Schlundt, head of food safety at the World Health Organisation, told The Sunday Times. "The experts were unanimous and clear that this is a major concern." He added that a "significant proportion" of the 30-40% of cancers linked to diet could be caused by acrylamide. Other experts think the finding may help explain why cancer rates are rising in the West, even though diet is apparently improving. Between 1971 and 1997, the number of new cancer cases recorded each year in England and Wales increased from 149,000 to 171,000. "This is a conundrum that has baffled scientists," says Tim Lang of Thames Valley University, "but the discovery of acrylamide could be the explanation we need. It means that these deaths could be caused by modern food processing and cooking techniques."

Should we be changing our diets?

At the moment, the scientific establishment is urging people not to worry about acrylamide, not least because there is no evidence that the substance is a human carcinogen. According to the WHO, the levels the average person consumes are probably lower than those found to cause nerve damage in rats. On the other hand, it would do us no harm to cut back on fatty, fried foods such as crisps and chips, and eat more fruit and vegetables. So if the acrylamide scare encourages people to do that, they will indeed be better off.