15 Male smokers, compared to non-smokers, have more oxidative lesions in sperm DNA 16 and more chromosomal abnormalities in sperm. Smoking by fathers, therefore, may plausibly increase the risk of birth defects and childhood cancer in offspring. A new epidemiological study suggests that the rate of childhood cancers is increased in offspring of male smokers, e.g., acute lymphocytic leukemia, lymphoma, and brain tumors are increased three to four times. White cells and other phagocytic cells of the immune system combat bacteria, parasites and virus-infected cells by destroying them with potent, mutagenic oxidizing agents. The oxidants protect humans from immediate death from infection, but they also cause oxidative damage to DNA, chronic cell killing with compensatory cell division, and mutation 23 and thus contribute to the carcinogenic process.
Antioxidants appear to inhibit some of the pathology of chronic inflammation.
Chronic infections cause about 21 percent of new cancer cases in developing countries and 9 percent in developed countries. Many lifestyle factors such as reproductive history, lack of exercise, obesity and alcohol intake influence hormone levels and therefore increase risk. 26 Other causal factors in human cancer are excessive alcohol consumption, excessive sun exposure, and viruses. Genetic factors also play a significant role and interact with lifestyle and other risk factors. Biomedical research is uncovering important genetic variation in humans.