Studies of Non-Ionizing Radiation-Related Cancer

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Case referent study of brain tumors - 04030 The etiology of brain tumors and brain cancer is poorly understood, and recorded incidence rates have increased dramatically over the past several decades. In response to these findings, and to advance understanding of environmental, behavioral and genetic causes of brain tumors, we conducted a case-control study of malignant and benign brain tumors (glioma, meningioma and acoustic neuroma). Excess risks of glioma were found among electricians and farmers, and an elevated risk of meningioma was seen among auto-body painters. Detailed occupational exposure assessments were conducted for electromagnetic radiation, lead, and pesticides. No associations were seen for electromagnetic radiation, but an association was suggested for meningioma and lead. No consistent evidence was found of an association between any of six chlorinated solvents and risk of glioma or meningioma although there was limited evidence of an association between carbon tetrachloride and risk of glioma. Recent genetic analyses have indicated associations between brain tumor risk and polymorphisms in cytokine, apoptosis/cell cycle control, DNA repair and oxidative stress genes. Findings for these pathways are being followed up in larger and more comprehensive studies. Cellular Telephone Use and Cancer Risks Ionizing radiation is known to increase cancer risks, but there is no consistent evidence that non-ionizing radiofrequency radiation (cell phones) or magnetic field (power lines and electrical appliances) exposures increase cancer risk. As a result of public and Congressional concern, the Radiation Epidemiology Branch (REB) launched an early case-control study and found no relationship between cell phone use and risk of glioma, meningioma or acoustic neuroma. A study of time trends in glioma incidence in the U.S. led by REB showed no rise despite dramatic increases in cell phone use. A subsequent REB assessment demonstrated that the elevated glioma risks associated with cell phone use in a Swedish study that influenced IARCs conclusion of possible carcinogenicity was not consistent with U.S. incidence trends, though incidence trends could be consistent with the small excess of glioma in the highest level users in the Interphone study. UV Dosimetry - 10262 A pilot study of 125 volunteer radiologic technologists was performed by REB investigators in which daily diaries and polysulfone UV dosimeters were used to develop better questionnaire approaches to ascertain environmental UV exposure for future studies of 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 and the reproducibility of hour-based compared to activity-based questionnaires was poorer in adult women. Improved exposure assessment may enable us to characterize more quantitatively the effects of UV and ionizing radiation on skin and other cancers. PLCO Lung DNA Damage Study - 10334 It is unclear whether the reported associations between functional assays and increased lung cancer risk represent a true association because the tests were performed on biologic specimens collected after cancer diagnosis. It may be that they are measuring the consequence, rather than the underlying cause of cancer (termed reverse causation bias). Several DCEG investigators are participating in the effort to determine the predictive value of multiple phenotypic or functional assays in pre-diagnostic samples from lung cancer patients included in the Prostate, Lung, Colon, and Ovary (PLCO) screening trial. Primary study findings were that neomycin mutation sensitivity was associated with increased lung cancer risk. Further study of DNA repair genes will be done using existing GWAS data.