What are the known or suspected causes of childhood cancer?
The causes of childhood cancers are largely unknown. A few conditions, such as Down syndrome, other specific chromosomal and genetic abnormalities, and ionizing radiation exposures, explain a small percentage of cases. Environmental causes of childhood cancer have long been suspected by many scientists but have been difficult to pin down, partly because cancer in children is rare and because it is difficult to identify past exposure levels in children, particularly during potentially important periods such as pregnancy or even prior to conception. In addition, each of the distinctive types of childhood cancers develops differently—with a potentially wide variety of causes and a unique clinical course in terms of age, race, gender, and many other factors. Possible risk factors for specific childhood cancers are discussed in the SEER monograph mentioned above. It can be found at http://seer.cancer.gov/publications/childhood/ on the Internet. A number of studies are examining suspected or
