Polycyclic aromatic hydrocarbons are a class of organic compounds having two or more benzenes and are carcinogens. Mainly from the processing of food, especially in the process of smoking or baking, the oil on the food can be heat-polymerized to produce benzopyrene; polycyclic aromatic hydrocarbons in the environment such as atmosphere, water and soil can make food, fruits and vegetables. Being contaminated.