What is Radon?

Radon is characterized as a colorless and odorless gas that originates from the natural decay of uranium in soil, rock, and water. It is notably recognized as the second leading cause of lung cancer among non-smokers in the United States, which makes the correct answer particularly significant in the context of public health and indoor air quality. High levels of radon can accumulate in homes, especially in lower levels such as basements, creating a serious health risk for occupants. This places importance on radon testing and mitigation strategies in the context of sustainable building practices, as addressing radon exposure is crucial for ensuring the safety and well-being of the building's occupants.

The other options do not accurately represent radon’s characteristics or significant health effects. For instance, while some gases are harmful to aquatic life, radon is not one of them. Additionally, radon's lack of visibility distinguishes it from any commonly known visible gases. Furthermore, while indoor air pollutants can arise from cleaning products, this is not relevant to radon, which originates from natural geological processes rather than human activities. This distinction reinforces the importance of understanding radon’s unique risks and the need for proactive measures in building design and maintenance.