Overall, they include drugs that have long been abused, such as marijuana and cocaine, and drugs whose abuse is a more recent development. Some are stimulants, some depressants, and some hallucinogens-while most exhibit multiple pharmacological properties.
Studies of PCBs in humans have found increased rates of melanomas, liver cancer, gall bladder cancer, biliary tract cancer, gastrointestinal tract cancer, and brain cancer, [1] and may be linked to breast cancer. PCBs are known to cause a variety of types of cancer in rats, mice, and other study animals. [2].
HIV, the virus that causes acquired immune deficiency syndrome (AIDS), doesnât appear to cause cancers directly. But HIV infection increases a personâs risk of getting several types of cancer, especially some linked to other viruses.iruses that can lead to cancer. Viruses are very small organisms; most canât even be seen with an ordinary microscope. They are made up of a small number of genes in the form of DNA or RNA surrounded by a protein coating.