Which of the following is a source of radiation exposure?

The correct choice encompasses a comprehensive understanding of the various sources of radiation exposure that individuals encounter in their daily lives.

Natural background radiation is emitted from cosmic rays and radioactive materials found in the Earth, such as radon gas from soil and rocks, and from certain foods that contain naturally occurring isotopes. This source of radiation is constantly present in the environment.

Medical procedures contribute significantly to radiation exposure, as diagnostic imaging techniques, such as X-rays, CT scans, and radiation therapy for cancer treatment, utilize ionizing radiation to aid in diagnosis and treatment. These procedures are indispensable in modern medicine, but they do contribute to an individual’s cumulative radiation dose.

While environmental pollutants may contribute to various health risks, they typically do not involve ionizing radiation in the same direct manner as the other options. However, it's important to note that some environmental contaminants may emit radiation depending on their composition.

Thus, recognizing that all the sources listed can lead to radiation exposure in different ways solidifies the choice of selecting "all of the above." This understanding is crucial in radiological safety and worker training, as it highlights the importance of awareness regarding both natural and artificial sources of radiation exposure in occupational settings and everyday life.