When you are in the kitchen and heat the oil to the temperature required to cook chips or stir-fries many harmful particles are released into the air. They are chemicals named polycyclic aromatic hydrocarbons (PAHs), and a recent study conducted in Singapore found that these particles are cancer-causing. By consequence, repeated exposure to polycyclic aromatic hydrocarbons could increase your risk of developing cancer.

PAH's are compounds made up of hydrogen and carbon only (hydrocarbons) and they are the result of incomplete combustion. For instance, we can find them in coal tar (released by heating coal not having enough oxygen to burn it all) or in the exhaust of Diesel engines badly maintained. Many of them are hazardous, such as benz[a]pyrene which is a very potent carcinogen.

The study claims that PAHs produced by high heated oil when cooking deep-frying cheeps are similar to the dangerous chemicals found in tobacco smoke and exhaust fumes. All kind of cooking oils, especially vegetable oils, produce these hazardous particles. The total of harmful chemical released depends by the amount of oil used and the level of temperature maintained during the cooking process.

A comparison of the different cooking methods revealed that deep-frying done in Malaysian kitchens released more PAHs than the traditional Chinese stir-frying. The Indian cooking style cut down on the hydrocarbons because much of the food is simmered or boiled.

The study authors estimate that people regularly exposed to high levels of PAHs would have an increased chance of developing cancer.