Final answer:
Radiation from radon, a naturally-occurring radioactive gas, can cause lung cancer.
Step-by-step explanation:
Radiation from radon, a naturally-occurring radioactive gas, can cause lung cancer. When radon decays, it releases highly energetic gamma-rays that can damage living cells and lead to the development of lung cancer. The US Environmental Protection Agency recommends testing homes and schools for radon levels, as it is the second leading cause of lung cancer after smoking.