Cancer is a group of diseases involving abnormal cell growth with the potential to invade or spread to other parts of the body. These contrast with benign tumors, which do not spread to other parts of the body. Possible signs and symptoms include a lump, abnormal bleeding, prolonged cough, unexplained weight loss and a change in bowel movements. While these symptoms may indicate cancer, they may have other causes. Over 100 types of cancers affect humans.
The fact that the general incidence of leukemia has doubled in the last two decades may be due, partly, to the increasing use of x-rays for numerous purposes. The incidence of leukemia in doctors, who are likely to be so exposed, is twice that of the general public. In radiologists … the incidence is ten times greater.
Isaac Asimov (1965) as quoted in Isaac Asimov’s Book of Science and Nature Quotations (1988), 233.
Pesticides are used around the world but can persist in the environment, contaminating drinking and irrigation water with toxic organic compounds. One example is Vietnam where herbicides and dioxins applied during the Vietnam war entered the water cycle, possibly leading to cancers and abnormalities in newborn babies.