Air quality and Radon
Radon is a gas that occurs naturally in soil and rock in some regions and that can get inside buildings by diffusing through the soil. In indoor air, it can lead to lung cancer.
(GreenFacts- Facts on Health and the Environment)
Radon gas can't be filtered, but air filtration can reduce health risks linked to radon exposure. When radon decays, it produces solid elements that stick to surfaces, such as dust particles. Breathing these dust particles can increase your risk of getting lung cancer, unless they are filtered.