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.: +1 707 777 6598; Fax: +1 701 777 0980; [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