Which gas is naturally occurring and has been linked to lung cancer?

Radon is a naturally occurring radioactive gas that is produced from the decay of uranium found in soil, rock, and water. It is particularly concerning because it can accumulate in homes and buildings, especially in areas with poor ventilation. Long-term exposure to elevated levels of radon has been linked to an increased risk of lung cancer, making it a significant public health hazard. The U.S. Environmental Protection Agency (EPA) has set guidelines to mitigate radon levels in indoor environments, emphasizing the importance of testing homes for this gas.

The other options, while they can have harmful effects, do not specifically carry the same strong association with lung cancer as radon does. For instance, carbon monoxide is primarily known as a poisonous gas that can cause harmful health effects but is not directly linked to cancer. Chlorofluorocarbons (CFCs) are compounds that were commonly used in refrigerants and aerosol propellants and are more known for their role in ozone depletion rather than as carcinogens. Asbestos, while a known carcinogen linked to lung cancer and mesothelioma, is not classified as a gas; it is a mineral that can become airborne under certain conditions. Therefore, radon stands out as the correct choice regarding its natural occurrence