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].
Carcinogens cause cancer by producing changes (or mutations) in the genetic material, or DNA, of a cell. These mutations result in uncontrolled cell division. A cancer-causing substance can alter the DNA of a cell directly or it can react with other chemicals in the body to form substances that cause gene mutations.