Studies of Non-Ionizing Radiation-Related Cancer

为了解决人们对住宅磁场暴露的癌症风险的广泛担忧，来自NCI和儿童癌症小组的研究人员对儿童急性淋巴细胞性白血病进行了一项病例对照研究。几乎没有证据表明，居住在测量到的时间加权平均(TWA)磁场水平较高或最高线码类别(替代衡量住宅附近电线的距离和特征)的房屋中，会增加儿童患急性淋巴细胞性白血病的风险。最近的分析集中在一次VIST期间收集的测量数据在一天中的任意时间、一周中的哪一天和季节中估计较长期的住宅60赫兹磁场水平的情况。我们发现了一个小的但统计上显著的季节性影响，春季住宅磁场水平低于长期估计(定义为6个双月访问的所有24小时测量的地磁平均值)，夏季高出约4%。没有发现对星期几有影响。然而，我们确实发现了一个系统的和可察觉的日效应，这表明一个傍晚黑子的测量可能会高估长期估计20%或更多。 为了进一步评估儿童白血病风险与他们个人使用电视机、吹风机和立体声耳机以及他们的母亲产前使用缝纫机之间的统计关联，在华盛顿特区及其马里兰州郊区对志愿者进行的一项实地研究中，研究了每种电器样本产生的极低频(ELF)和甚低频(VLF)磁场的特征。在距离吹风机喷嘴10厘米处测量到的极小磁场比周围环境平均升高了17倍，而耳机附近用来听音乐的磁场与60赫兹的周围环境水平没有区别。缝纫机在母亲的小腹前表面产生的极低频磁场比周围环境水平高出28倍。据估计，吹风机、立体声耳机和缝纫机的平均日使用量分别为2.6分钟、19分钟和17分钟。这些数据和之前公布的电视机测量数据并不能提供与增加峰值或TWAELF磁场暴露相关的白血病风险增加(或减少)的一致图景。总体而言，这些结果几乎没有证据支持这样的假设，即电器产生的峰值或TWAELF磁场与儿童白血病的风险存在因果关系。 脑肿瘤的病因知之甚少，在过去的几十年里，有记录的发病率急剧上升。这一增长在一定程度上是真实的，还是完全是诊断改进的人造产物，这是一个有争议的问题。尽管如此，人们还是担心，一种或多种日益常见的环境暴露可能会导致脑癌。例如工业化学品、杀虫剂、食品添加剂和电磁场。为了回应这些担忧，并促进对脑肿瘤的环境、行为和遗传原因的了解，我们正在与美国三家医院的研究人员合作，对恶性和良性脑肿瘤进行病例对照研究。正在考虑的因素包括工作场所接触化学制剂和电磁场、使用移动电话、饮食因素、肿瘤家族史、易感性的遗传决定因素、家用电器使用、生殖史和荷尔蒙暴露、病毒、医疗和牙齿暴露于电离辐射，以及病史的其他方面。这项研究的主要特点包括：研究规模庞大、注重迅速确定事故个案和约谈研究对象而不是代孕受访者、使用由工业卫生人员制定的详细、针对工作的问题来确定职业接触情况，以及储存血液样本以供将来评估遗传易感性、接触的生物标记，以及基因与环境和基因之间的相互作用。我们最初的报告涉及移动电话的使用。我们没有发现使用手机与脑瘤之间的联系。有无过敏史(OR=0.67，95%CI=0.52，0.86)和自身免疫性疾病史(OR=0.49，95%CI=0.35，0.69)与舌瘤有显著相关性。脑膜瘤或听神经瘤与任何过敏史均无明显关联，但脑膜瘤与自身免疫性疾病史呈负相关(OR=0.58，95%CI=0.38，0.92) 为了回应人们对微波和无线电频率的非电离辐射引发的癌症风险的担忧，早先一项关于暴露在微波辐射下的朝鲜战争海军退伍军人癌症死亡率的研究重新启动。总体上，死于所有疾病和所有癌症的人数明显低于预期，与雷达暴露潜力较低的20,560名船员相比，雷达暴露潜力较高的20,021名船员的死亡人数明显低于预期。在整个队列中，没有证据表明脑癌增加。睾丸癌死亡的发生率也低于预期。非淋巴细胞白血病在高暴露职业的男性中显著升高，但仅在三种高暴露职业中的一种，即航空中队的电子技师(SMR=2.2，95%CI=1.3，3.7)。在这群美国海军退伍军人中，雷达暴露对死亡率几乎没有影响。

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. There was little evidence that living in houses characterized by high measured time-weighted average (TWA) magnetic field levels or by the highest wire-code category (a surrogate measure of the distance and characteristics of power lines near homes) increases the risk of acute lymphoblastic leukemias in children. Recent analyses focused on how well measurement data collected during a single vist made at an arbitrary hour of the day, day of week, and season estimate longer term residential 60-Hz magnetic field levels. We found a small but statistically significant seasonal effect, with residential magnetic field levels lower than the long term estimate (defined as the geometirc mean of all 24 hour measurments from 6 bimonthly visits)in the spring and about 4% greater during the summer. No effect was found for the day of the week. However, we did find a systematic and appreciable diurnal effect, suggesting that an evening spot measurement may overestimate the long term estimate by 20% or more. To evaluate further the statistical associations between leukemia risk in children and their personal use of TV sets, hair dryers, and stereo headsets, and prenatal use by their mothers of sewing machines, extremely (ELF) and very low frequency (VLF) magnetic fields produced by a sample of each type of appliance were characterized in a field study of volunteers conducted in Washington,D.C. and its Maryland suburbs. ELF magentic fields measured 10 cm from nozzles of hair dryers were elevated over the ambient by a mean factor of 17, whereas fields near headsets being used to listen to music were not distinguishable from ambient levels at 60-Hz. House sewing machines produced ELF magnetic fields that were elevated by a factor of 28 over ambient levels at the front surfaces of the lower abdomen of mothers. Estimated mean daily use of hair dryers, stereo headsets, and sewing machines were 2.6, 19, and 17 minutes, respectively. These data and previously published measurements of TV sets do not provide a consistent picture of increased (or decreased) leukemia risk in relation to increasing peak or TWA ELF magnetic field exposure. Overall, the results provide little evidence supporting the hypothesis that peak or TWA ELF magnetic fields produced by appliances are causally related to the risk of childhood leukemia. 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. There was a significant association between giloma and history of any allergies (OR=0.67,95% CI=0.52,0.86) or autoimmune diseases (OR=0.49,95% CI=0.35,0.69). No significant associations were evident for meningioma or acoustic neuroma with history of any allergies, but an inverse association was observed between meningioma and history of autoimmune diseases (OR=0,58, 95% CI=0.38,0.92) 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 20,021 sailors with high radar exposure potential compared to the 20,560 sailors with lower radar exposure potential. There was no evidence of increased brain cancer in the entire cohort. Testicular cancer deaths also occurred less frequently than expected. Nonlymphocytic leukemia was significantly elevated among men in high-exposure occupations but in only one of the three high exposure occupations, namely electronic technicians in aviation squadrons (SMR=2.2, 95% CI=1.3,3.7). Radar exposure had little effect on mortality in this cohort of US Navy veterans.