What is radon recognized as in terms of its health effects?

Radon is classified as a known human lung carcinogen due to its radioactive properties and the health risks associated with prolonged exposure. When radon gas is inhaled, it can decay into radioactive particles that may get trapped in the lungs. Over time, this exposure increases the risk of developing lung cancer. The evidence supporting radon's status as a carcinogen is well documented, making it a significant public health concern. Awareness of its risks has led to recommendations for testing and mitigating high radon levels in homes, especially in areas known for elevated radon concentrations.

In contrast, the other options misrepresent the nature and effects of radon. Describing it as a benign gas, effective air purifier, or harmless element overlooks the substantial evidence linking radon exposure to serious health outcomes, particularly lung cancer. Therefore, identifying radon as a known human lung carcinogen is critical for understanding the public health implications and necessary precautions associated with this hazardous gas.