If you’re offered a plate of blackened barbecue food this summer, you might think twice about eating it. It’s commonly thought that food that has been burnt could cause cancer. This is in part down to one particular molecule that forms when food is cooked at high temperatures, known as acrylamide. But while the chemical is a known potential toxin and carcinogen in its industrial form, the link between consuming it in food and developing cancer is much less clear.
The reason we even know about acrylamide’s potential dangers are down to a railway tunnel. Nearly 20 years ago, workers were building a tunnel through the Hallandsås ridge on the Bjäre peninsula in southern Sweden. Cows nearby started to show strange symptoms, staggering around and in some cases collapsing and dying. This prompted an investigation that showed that they had been drinking contaminated stream water and that the contamination was from a toxic molecule, acrylamide.
The construction workers had been using its polymer, polyacrylamide, as a crack sealant. This was, in itself, quite safe. But the polymer-forming reaction was incomplete, so some unreacted acrylamide was still present. The workers were tested to see if they also had unsafe levels of acrylamide in their blood, with a second “control” group of people who had no known exposure to industrial acrylamide used as a benchmark. However, it turned out that the control group also had surprisingly high amounts of acrylamide in their blood.
At first it was thought that burgers might be the source. Then high levels of acrylamide were found in potato products such as fried potatoes, as well as in coffee. It then became clear that acrylamide formation was associated with carbohydrate-rich foods, rather than protein-rich ones, and with foods that had been heated above 120°C (250°F), that is food that has been fried, roasted or baked. This was a new discovery, but acrylamide must always have been formed in this style of cooking, ever since cooking was invented.