Indoor radon is the second leading cause of which condition in the United States?

Indoor radon is identified as the second leading cause of lung cancer in the United States, following smoking. Radon is a colorless, odorless gas that can accumulate in homes and buildings, particularly in areas with poor ventilation. When inhaled, radon decays into radioactive particles that can damage lung tissue and increase the risk of developing lung cancer over time. This association is particularly concerning for smokers, as the combined risk from smoking and radon exposure significantly elevates lung cancer risk.

The other choices—heart disease, respiratory illness, and asthma—do not have the same direct correlation with radon exposure as lung cancer does. While radon can contribute to general respiratory issues, it is specifically linked to lung cancer as a significant risk factor, making it crucial for homeowners and real estate professionals to be aware of radon levels in properties.