What is the estimated average outdoor radon level?

The estimated average outdoor radon level is approximately 0.4 pCi/L. This figure represents the typical concentration of radon found in outdoor air, which is significantly lower than indoor radon levels, primarily due to dilution in the outdoor environment. Radon is a naturally occurring radioactive gas that originates from the decay of uranium in soil, rock, and water, and while it can accumulate in enclosed spaces like homes, it is much less concentrated outdoors. Understanding the average outdoor radon level is critical for contextualizing radon measurements in indoor environments, where levels can be influenced by various factors such as building materials and ventilation.