68e07683_SAHRA___Home_Water_Testing__Likely_source
[Lab result] Radon gas [Potential health effects] Exposure to high levels may result in an increased incidence of lung diseases, such as emphysema and pulmonary fibrosis. Several studies of individuals exposed over long periods have reported significant increases in early mortality due to cancer and nonneoplastic (noncancer) diseases. Exposure is principally through inhalation of the gas as it is released through showerheads and taps. [Treatment options] Regulated and controlled by water providers with aeration. Some activated carbon filters reduce it in tap water (POU). [Likely source] 
Naturally occurring
SAHRA - Home Water Testing
Likely source