Benzene is a highly flammable organic chemical found in nature and also in plastics, rubber, gasoline and cigarette smoke. It most commonly makes its way into the water supply through discharge from factories, as well as leaching from gas storage tanks and landfills. Benzene ingestion in large amounts can cause vomiting, stomach irritation, convulsions and even death. It has been linked to blood related problems, like anemia, and can affect the tissues that form blood cells, especially the bone marrow. Long-term exposure to high levels of benzene can damage the immune system and make the person more prone to cancer, especially leukemia.