Cancer is not one disease. It is a hundred or more diseases. It can be induced in experimental animals by the use of chemicals, radiations or viruses. Inspired by the success with antibiotics in controlling infectious diseases, the public,and indeed cancer research scientists have been concentrating in seeking a cure. It is just possible that for many of the forms of cancer there will be no magic cure and the most practical approach will be to find means of prevention and of prophylaxis Certain occupations carry a higher risk of cancer development compared to the rest of the population.
Current evidence suggests that there exists no safe threshold level for a carcinogenic chemical.
It produces one hundred per cent incidence of cancer in rats when incorporated in their diet at levels of 15 ppb. Our knowledge of the action of chemical carcinogens indicates that they act optimally when administered as frequent small doses over a period of time rather than as large single doses. Because such weak carcinogens are unlikely to be implicated epidemiologically, they may be as dangerous, or possibly more dangerous than the more obvious potent carcinogens. There is long latent period between exposure to a carcinogenic chemical and the clinical appearance of cancer. There are instances of persons who had been born in the vicinity of asbestos mines and left the area in early childhood, developing mesothelioma in their fifties and sixties.