09/19/2026
New research is adding important evidence to a question that has received relatively little attention: the relationship between residential radon exposure and malignant brain and central nervous system cancer.
Mowrer and colleagues followed 159,391 postmenopausal women participating in the Women’s Health Initiative for an average of 17.7 years. During that period, 451 malignant brain/CNS cancers were identified.
The researchers evaluated residential radon exposure using five different geographic exposure metrics — and estimated risk was elevated across all five.
Using one of the study’s radon exposure models, women in the highest estimated exposure group had a 49% higher hazard of malignant brain/CNS cancer compared with women in the lowest group.
That consistency matters.
The radon estimates are imperfect, but the same exposure-assessment methods were applied to women who developed cancer and those who did not. This type of exposure imprecision generally tends to weaken a real association rather than create one.
And measuring radon directly in 159,000 homes over decades would not necessarily provide a perfect measure of individual exposure. People move, spend time away from home, and occupy different areas of buildings. Reconstructing long-term environmental exposure is one of the fundamental challenges of environmental epidemiology.
No single study establishes causality. Evidence develops through replication, consistency, biological understanding, and the accumulation of research.
This is now the largest cohort study examining residential radon and malignant brain/CNS cancer, and its findings are consistent with the previous cohort study conducted in Denmark.
The authors conclude that residential radon “may contribute meaningfully to the overall burden of CNS cancers” and describe it as “a potentially modifiable environmental risk factor.”
That makes this an important finding to follow — and an important reason to continue improving how we characterize long-term radon exposure in environmental health research.
We thank Carson Mowrer and Dr. Matthew Bozigar for reviewing our interpretation of their research and helping us communicate the findings accurately.
Source: Mowrer et al., Neuroepidemiology (2026)
