22 April 2006
NewScientist.com news service
Andy Coghlan

Just four years ago, on the Thursday morning of 25 April 2002, millions of people awoke to newspaper and TV reports that their breakfast might be laced with a deadly chemical.

They hadn't been poisoned, nor were they victims of an unscrupulous food manufacturer. Nevertheless, the reports warned, the slice of bread, bowl of cereal or plate of waffles in front of them might contain a potent cancer-causing chemical called acrylamide. The implications were astounding. Scientists said the chemical might be impossible to eradicate, as it was created during the normal cooking process. And the health effects were impossible to judge.

Though the story faded from the front pages, New Scientist can reveal the unprecedented research effort that is under way to learn more about acrylamide. The twin goals are to establish whether it might be responsible for an epidemic of cancer and other illnesses, and to eliminate acrylamide as far as possible from our food. Andy Coghlan takes up the story of one of the biggest food scares of modern times.

NO ONE expected the news delivered by Leif Busk and Margareta Törnqvist on 24 April 2002. Speaking in Sweden to the biggest press conference the country had seen for almost 20 years, the two scientists announced to the world that the toxic industrial chemical acrylamide was lurking in a huge range of everyday foods.

"It was a complete bolt from the blue," recalls Diane Benford, head of the UK Food Standards Agency's toxicology branch. The discovery meant that almost everyone must be ingesting this toxic substance, with unknown consequences for public health. "Acrylamide was suddenly discovered in food, whereas previously, it was only known as an industrial chemical. It was unprecedented," she says.

The reaction to the news was unprecedented too, starting with the huge press interest in the announcement. "What we wanted to bring out by holding the press conference was that we needed more data," says Busk, who is still based at Sweden's National Food Administration in Stockholm. What resulted was a global media frenzy, followed by fearful consumers demanding to know what foods, if any, were safe to eat. "We didn't anticipate the information vacuum that would result."

Governments, international health authorities and the food industry reacted quickly. In June 2002, the World Health Organization convened a summit on acrylamide in Geneva, Switzerland, which revealed how little we knew about the chemical and its effects. Since then, tens of millions of dollars have been spent on hundreds of research projects to find the answers, and next week scientists will come together to discuss progress at a meeting convened by the UN's food regulator, the Codex Alimentarius Commission.

What is clear is that acrylamide is formed by what is known as the Maillard reaction, in which amino acids react with sugars when food is heated to more than 120 °C and begins to brown. Bread crusts and fried or roasted potatoes are among the many foods in which the Maillard reaction is responsible for the characteristic texture and taste. Acrylamide forms from the reaction between the amino acid asparagine and reducing sugars such as glucose and fructose, which are found in large quantities in plants such as potatoes and cereals.

The current best guess is that half the acrylamide we ingest comes from processed foods, and half from food cooked at home. Richard Stadler, technical director of an initiative by the European Union's Confederation of the Food and Drink Industries (CIAA) to eliminate acrylamide from processed food, says research is ongoing to pin down exactly where the acrylamide in our diet comes from.

It is also becoming apparent that acrylamide might be far more prevalent in food than even the Swedish researchers thought. According to data from 17 countries published in February 2005 by the Joint FAO/WHO Expert Committee on Food Additives (JECFA) we now know that the chemical is found in foods ranging from olives, pizza and beer to baby foods and green tea. Between 10 and 20 per cent of our exposure is thought to come from pastries and cookies, while in some countries up to 39 per cent of exposure comes from coffee.

That puts acrylamide in a different category from carcinogens in food such as aflatoxins or ochratoxin A, which are produced by fungi that contaminate cereal crops. For these toxins, legal safety levels can be set on the quantities that can be present in food, ensuring that only safe levels are ingested. That is virtually impossible with acrylamide, as it is everywhere. "We realised we couldn't remove products containing it from sale," says Busk. "There would be nothing left in the shops." Even if that were done, acrylamide would still be produced during home cooking.

Acrylamide is known to have potent health effects. It is potentially neurotoxic, and workers in the building and construction industry exposed to polyacrylamide, which is prepared on site from acrylamide, have developed numbness in their fingers and toes, while prolonged exposure can trigger paralysis, Busk says.

According to Busk, any cancers caused by acrylamide in food will only show up in sophisticated, large epidemiological studies, and these have not been done. "The risk is low compared to smoking, but high compared with other food carcinogens," he says. "It's probably the same level of risk as background natural radiation."

The advice of most experts is to continue to eat a balanced diet low in fried foods and high in fruit and vegetables, which is what most also advise on nutritional grounds.