Studies of Non-Ionizing Radiation-Related Cancer

为了解决人们对住宅磁场暴露导致癌症风险的广泛担忧，NCI和儿童癌症组的研究人员进行了一项儿童急性淋巴细胞白血病的病例对照研究。最近的分析集中在暴露度量的方法学问题上，并得出结论认为，有必要对静态磁场进行反复的点测量，以将受试者的卧室划分为“共振”或“非共振”，但单点测量是不够的。此外，研究人员还测量了电器的磁场，以确定与儿童白血病有关的特定类型的电器是否会产生更高的磁场暴露。这些器具产生的磁场不足以说明统计上的关联。

To address widespread concerns about cancer risks from residential magnetic field exposures, investigators from NCI and from the Children's Cancer Group have conducted a case-control study of childhood acute lymphoblastic leukemia. Recent analyses focused on methodologic issues of exposure metrics, and concluded that repeated spot measurements of static magnetic fields would be necessary to classify bedrooms of subjects as being "in resonance" or "out of resonance", but that a single spot measurement was insufficient. In addition, magnetic fields from appliances were measured to determine if specific types of appliances, statistically linked with childhood leukemia, actually generated higher magnetic field exposures. Magnetic fields from these appliances were not sufficiently elevated to account for the statistical associations. The etiology of brain tumors is poorly understood, and recorded incidence rates have increased dramatically over the past several decades. Whether this increase is, in part, real or is entirely an artefact of improved diagnosis is a controversial issue. Nonetheless, concern has arisen that one or more increasingly common environmental exposures might cause brain cancer. Examples include industrial chemicals, pesticides, food additives, and electromagnetic fields. In response to such concerns, and to advance understanding of environmental, behavioral and genetic causes of brain tumors, we are collaborating with investigators at three U.S. hospitals in conducting a case-control study of malignant and benign brain tumors. Factors under consideration include workplace exposures to chemical agents and electromagnetic fields, use of cellular telephones, dietary factors, family history of tumors, genetic determinants of susceptibility, home appliance use, reproductive history and hormonal exposures, viruses, medical and dental exposure to ionizing radiation, and other aspects of medical history. Key features of the study include its large size, the emphasis on rapid ascertainment of incident cases and interview of study subjects rather than surrogate respondents, the use of detailed, job-specific questions developed by industrial hygienists to ascertain occupational exposures, and the storage of blood samples for future evaluation of inherited susceptibility, biomarkers of exposure, and gene-environment and gene-gene interactions. Our initial report concerned use of cellular telephones. We found no association of cellular telephone use with brain tumors. In response to concerns about cancer risk from non-ionizing radiation of microwave and radio frequencies, an earlier study of cancer mortality among Korean War Naval Service veterans exposed to microwave radiation has been reactivated. Deaths from all diseases and all cancers were significantly below expectation overall, and for the 20,000 sailors with high radar exposure potential compared to the 20,000 sailors with lower radar exposure potential. No adverse health effects appeared attributable to radar exposure during the Korean war.