Case referent study of brain tumors: 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 artifact 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. In our initial report, we found no association of cellular telephone use with brain tumors. Electrical appliances produce the highest intensity exposures to low-frequency electromagnetic fields. Appliance use and the risk of brain tumors was evaluated in this hospital-based case-control study. The association of self-reported use of 14 common household appliances was investigated among the 678 cases and 686 controls who had completed self-administered questionnaires. Overall, results indicated that ELF-EMF fields from commonly used household appliances are unlikely to increase the risk of brain tumors.In other analyses, excess risks of glioma were found among electricians and farmers, and an elevated risk of meningioma was seen among auto-body painters. Evaluations are in progress to clarify the possible role of solvents, pesticides, lead, EMF and other exposures in explaining these associations. Self-reported family history of cancer showed glioma risk to be elevated only slightly and nonsignificantly among persons with a family history of brain cancer. Persons reporting a family history of prostate, stomach or colon cancer, or Hodgkins lymphoma, had an increased risk of glioma. Risk of meningioma was increased among persons reporting a family history of a benign brain tumor or melanoma. An early age at menarche and early age at first live birth appeared to be protective against glioma, but not meningioma. The risk of glioma was found to be reduced among left-handers relative to right-handers (OR=0.7; 95% CI: 0.5-0.9). Risk of glioma and meningioma appeared to vary with season of birth, with higher risks among persons born in the winter and lower risks among those born in the summer. Risk of glioma in women increased with older age at menarche. Early age at first birth was associated with reduced risk. Brain tumor risk did not appear to be related to use of hair dyes.UV Dosimetry: REB investigators conducted a pilot study of 125 volunteer radiologic technologists in which daily diaries and polysulfone UV dosimeters were used to develop better questionnaire approaches to ascertain UV exposure for skin and other cancers in this largely female occupational population. The volunteers were queried 6 months later to test the reproducibility of responses to time outdoors. Agreement between reported time on weekdays was significantly higher than for weekends. Improved exposure assessment will enable us to characterize more quantitatively the effects of UV and ionizing radiation on skin and other cancers. We are currently analyzing the validity and reproducibility of hour-based and activity-based questionnaires to capture lifetime sun exposure.
