is any of numerous complex hydrocarbon compounds consisting of three or more benzene rings in a compact molecular arrangement. Some types of PNA’s are known to be carcinogenic (cancer causing). PNA’s are formed in fossil fuel combustion and other heat processes, such as catalytic cracking. They can also form when foods or other organic substances are charred. PNA’s occur naturally in many foods, including leafy vegetables, grain cereals, fruits, and meats.