Edible oils are also susceptible to unintentional adulteration. Environmental conditions can lead to the appearance of pesticides, heavy metals, pyrolytic contaminants, polychlorinated biphenyls (PCBs), and dioxins in oils. Improper storage of oilseeds can lead to the production of mycotoxins, which are toxic secondary metabolites of mold. The fact that oils frequently undergo industrial processing prior to use in edible applications creates another opportunity for oil contamination. While processing is effective at removing some undesirable compounds that can negatively impact the health, taste, appearance, and shelf stability of oils, the industrial process itself can produce contaminants. These so-called “processing contaminants” include 3-MCPD esters, glycidyl esters, and ?,??unsaturated aldehydes, which can also form when oils are heated to high temperatures for cooking applications.