Toxic wastes frequently include carcinogens, and exposure to them through some mechanism, such as leakage or evaporation from storage, causes cancer to occur more frequently in exposed persons. In 2008, for example, a cluster of the uncommon blood cancer polycythemia vera was discovered at a hazardous waste disposal site in northeast Pennsylvania. The cause was considered to be contamination with the chemical 2,4-dichlorophenoxyacetic acid (2,4-D). Such sites are often located near residential areas where children play. Cancers can also be caused by toxic substances that enter the body through smoking, drinking alcohol, eating contaminated food, or using contaminated needles and instruments during medical procedures. Cancer is now the second most common disease among people aged 15 to 44 years in the United States. This type of cancer results when your skin comes into contact with a toxic substance or radiation. It may feel like a bug bite or a sunburn and later turns into a sore. These sores usually heal on their own but sometimes doctors can find scar tissue after the fact that shows they once been sores.