Radon gas is an important environmental carcinogen. Which statement best describes recommended public health action to reduce radon-related lung cancer risk in homes?

Assume all homes are radon-free if they are modern constructions; no testing or mitigation is necessary because radon only accumulates in very old buildings.

Encourage people to move to lower altitude areas because radon concentration is determined solely by elevation and will always be safe at lower elevations regardless of local geology.

Test homes for radon using detectors, and if levels are elevated, mitigate ventilation or sealing and follow region-specific guidance, particularly in areas known to have higher indoor radon levels.

Rely exclusively on sunscreen and UV-protective clothing as mitigation, since radon exposure is primarily through ultraviolet radiation pathways.