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].
But through scientific research, we know that our risk actually depends on a combination of our genes, our environment and aspects of our lives, many of which we can control. Cancer is caused by damage to our DNA, the chemical instructions that tell our cells what to do. Things in our environment, such as UV rays, or our lifestyle, such as the cancer-causing chemicals in tobacco, can damage our DNA. This damage builds up over time.