Future Oncol. 2017 Sep;13(21):1873-1881. doi: 10.2217/fon-2017-0165. Epub 2017 Aug 24.
County level incidence rates of chronic lymphocytic leukemia are associated with residential radon levels.

Oancea SC1, Rundquist BC2, Simon I3, Swartz S2, Zheng Y4, Zhou X4, Sens MA4, Schwartz GG1.
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Abstract
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.