Still another suspect in the lineup of possible cancer causes is radiation, since it is well known that radiation can cause mutations in cells, which could in turn reproduce and lead to cancer. We are all subjected to many sources of radiation. First, the earth is constantly bombarded from outer space with what is called "cosmic radiation." It is possible that this radiation could cause occasional mutations resulting in cancer. But virtually no researchers seriously suggest that background radiation is a major cause of cancer. For one thing, all parts of the world are equally exposed to this form of radiation, which makes it difficult to explain major variations among different countries in incidence rates and kinds of cancer. If background radiation were a major cause of cancer, its effects should be relatively equal in all countries.

Another possibility being discussed lately is that fluorocarbons released from aerosol cans may be capable of destroying the protective layer of ozone in the atmosphere, leading to an increased exposure to ultraviolet radiation from the sun. Although this could certainly lead to potential health problems, high levels of ultraviolet rays are not normally associated with any cancer other than skin cancer. And since these changes in the atmosphere have not yet occurred, this source cannot account for present cases of cancer.

There has also been considerable discussion of the harmful effects of X-rays and other radiation used in medical diagnosis and treatment. The evidence is still unclear, and caution is certainly reasonable (for example, a correlation has been observed between using radiation to treat arthritis and subsequent development of leukemia). But citing this source of radiation as the cause of cancer suffers from the same problem as the harmful substance theory: many people who have been exposed to high levels of X-rays or other radiation do not get cancer, while people who have relatively low exposure still get the disease. Statistically it may be a factor, but for the patient who asks, "Why me?" it does not provide anything like a complete answer.

*14\347\2*

Cancer