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].
The exact causes are unknown, but colon cancer has several potential risk factors. Polyps. Colon cancer usually derives from precancerous polyps that exist in the large intestine. The most common types of polyps are: Adenomas: These can resemble the normal lining of the colon but look different under a microscope. They can become cancerous.