Chemicals capable of causing cancer arise from a variety of sources. These include certain synthetic chemicals used in industry, some natural compounds formed during the curing and burning of tobacco, compounds formed during the cooking of meat, and chemicals present in certain plants and molds. Two categories have been identified, those capable of causing DNA damage and mutations directly (genotoxic, or direct-acting, carcinogens) and those that require prior metabolic activation by cells of the host to be converted to mutagens (epigenic, or indirect-acting, carcinogens). In the industrial countries much progress has been made in significantly decreasing and preventing exposure to ...(100 of 22361 words)