CR3 News Magazine 2017 VOL 4: SEPTEMBER Radon Resolutions | Page 36

Research Article For reprint orders, please contact: [email protected] County level incidence rates of chronic lymphocytic leukemia are associated with residential radon levels S Cristina Oancea 1 , Bradley C Rundquist 2 , Isaac Simon 3 , Sami Swartz 2 , Yun Zheng 4 , Xudong Zhou 4 , Mary Ann Sens 4 & Gary G Schwartz* ,1 Aim: We previously reported that incidence rates for chronic lymphocytic leukemia (CLL) among US states are significantly correlated with levels of residential radon (RR). Because these correlations could be influenced by confounding and/or misclassification among large geographic units, we reinvestigated them using smaller geographic units that better reflect exposure and disease at the individual level. Methods: We examined the relationships between CLL and RR per county in 478 counties with publicly-available data. Results: After adjustment for ultraviolet radiation, a possible risk factor for CLL, county rates for CLL and RR were significantly correlated among males and females both together and separately (p < 0.0001). Conclusion: CLL is significantly associated with RR at the county level. First draft submitted: 6 April 2017; Accepted for publication: 31 May 2017; Published online: 24 August 2017 Chronic lymphocytic leukemia (CLL) is the most common adult leukemia in western popula- tions  [1] , with approximately 18,960 new cases and 4660 related deaths annually in the USA  [2] . CLL is predominantly a disease of the elderly, with a median age at diagnosis of 71 years. It is more common among Caucasians and its incidence is almost twice as high among men than women  [3–5] . The etiology of CLL is poorly understood. A family history of hematologic malignancy is an estab- lished risk factor  [6,7] .  Atopic conditions (e.g., allergy, hay fever, asthma and eczema) appear to be protective  [8] . Environmental risk factors for CLL have not been consistently identified. Pesticides have been implicated in several  [9–11]  but not all  [12] studies. An increased risk in association with exposure to sunlight/ultraviolet radiation (UVR)  has been reported for non-Hodgkin lymphomas as a group  [13,14] .  Conversely,  a protective effect of UVR has been reported for CLL individually  [8,15] .    An etiologic role for ionizing radiation in CLL is controversial  [16] . Increased risks for CLL have not been observed among atomic bomb survivors and among other highly radiation-exposed populations, leading to the long-standing view that CLL is not radiogenic  [17,18] .  However, that view has been challenged by findings of significant associations between ionizing radiation and CLL among Czech uranium miners and Chernobyl cleanup workers  [19–23] .    The most important source of ionizing radiation for the general public is exposure to radon at home  [24] . Radon is a naturally- occurring gas that is the product of radioactive elements present in rocks and soil. The gas enters homes through cracks in the foundation and can be trapped inside, particularly during winter when Keywords  • chronic lymphocytic leukemia • epidemiology • ionizing radiation • latitude • radon Department of Population Health, School of Medicine & Health Sciences, University of North Dakota, Grand Forks, ND 58202, USA Department of Geography & Geographic Information Science, University of North Dakota, College of Arts & Sciences, Grand Forks, ND 58202, USA 3 Department of Earth System Science & Policy, University of North Dakota, John D. Odegard School of Aerospace Sciences, Grand Forks, ND, 58202, USA 4 Department of Pathology, University of North Dakota, School of Medicine & Health Sciences, Grand Forks, ND 58202, USA *Author for correspondence: Tel.: [phone]; Fax: [phone]; [email protected] 1 2 10.2217/fon-2017-0165 © 2017 Future Medicine Ltd Future Oncol. (2017) 13(21), 1573–1581 part of ISSN 1479-6694 1573