NOT in food. Mutagenic, carcinogenic if dosage is high enough. Meat and fish cooked at high temperatures. Mutagenic, carcinogenic if dosage is high enough. Meat and fish cooked at high temperatures.
Highest temperatures represent the primary risk.
It appears from the research about Maillard molecules, heterocyclic amines, and PAHs that the most dangerous compounds are formed at the highest temperatures, and that the longer the processing time, the more reaction products appear. While it's possible the reasoning as to passage through digestive barriers might be true as far as heat- denatured proteins are concerned, no evidence has been found that denatured proteins might be toxic. Most, if not all, Maillard compounds also appear naturally, in foods stored at room temperature, or inside the body. There is evidence that toxicity increases with temperature. Cooking probably represents a small risk in overall context, particularly with diets that are predominantly raw already.