Many nitrosamines, or simple organic oxides of nitrogen, are carcinogenic. That and hydrocarbons are carcinogens in cigarette smoke and increase the risk of lung cancer. Also another chemical gas, vinyl chloride, gas has been found to be an agent of sarcoma of the blood vessels in the liver. Many drugs as well as alkylating agents used to treat cancer are carcinogenic. Even though these chemicals break the DNA of cancerous cells, which kills them, it also induces cancer in normal cells.
Some hormones created in humans can also cause cancer.
Aspergillus that causes a number of c ancer, but generally liver cancer. Many carcinogens have not been discovered but research is being done to discover other carcinogens to keep people aware and safe. There are also many different biological agents which cause cancers. The most common biological agents are the oncogenic viruses that commonly bring about the formation of neoplasms in some smaller animals. Also some of these viruses are thought to cause human cancers, and one has even been proven to cause leukemia.