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].
PCBs are mainly broken down either by the effect (direct or indirect) of sunlight or by microorganisms. In general, the persistence of PCB congeners increases with the number of chlorine atoms. Sunlight can play a role in the breakdown of PCBs present in air, water and surface soil. In the atmosphere, PCBs that are present in the atmosphere tend to react with ozone and water under the effect of sunlight.