What is the largest natural source of radiation for humans?

Radon is recognized as the largest natural source of radiation for humans. It is a colorless, odorless gas that is produced from the decay of uranium found in soil, rock, and water. As it seeps up from the ground, radon can accumulate in buildings, particularly in basements and enclosed spaces, leading to increased exposure for individuals who spend time in those areas.

The health risks associated with radon exposure are significant, as prolonged inhalation can lead to lung cancer. This has made it a priority for health officials to monitor radon levels in homes and public buildings.

While uranium and plutonium are indeed radioactive elements, their presence in the environment is less widespread and they do not contribute to radiation exposure in the same way as radon does. Cosmic rays, originating from outer space, do contribute to radiation exposure; however, their overall contribution to the average person’s radiation dose is smaller compared to that from radon. This is why radon is highlighted as the greatest concern in terms of natural radiation sources for human exposure.