Radon is known to be the ______ greatest contributor to the average American's annual radiation exposure.

Radon is recognized as the second greatest contributor to the average American's annual radiation exposure. This recognition is based on studies and assessments conducted by health and environmental agencies that quantify exposure to various sources of radiation. While cosmic rays and terrestrial radiation contribute to background radiation, radon—which is a naturally occurring radioactive gas produced from the decay of uranium in the ground—poses a significant health risk, especially in homes and buildings where it can accumulate in enclosed spaces.

The acknowledgment of radon’s contribution highlights the importance of monitoring and mitigating levels of radon in residential areas, as it is known to be a risk factor for lung cancer. Understanding the ranking of radon in terms of radiation exposure helps in prioritizing public health efforts and education regarding radon testing and remediation. The categorization of radon as the second leading source also underlines the need for ongoing awareness and actions to address its presence in indoor environments.