45. The largest natural source of ionizing radiation comes from ___________. The largest anthropogenic source of ionizing radiation comes from ______________.

The largest natural source of ionizing radiation comes from space and is known as cosmic radiation. Cosmic radiation consists of high-energy particles, such as protons and atomic nuclei, that originate from the sun and other celestial bodies in the universe. These particles can penetrate the Earth's atmosphere and reach its surface, resulting in natural exposure to ionizing radiation.

To further understand and verify this information, you can consult reputable sources such as scientific articles, textbooks, or organizations specializing in radiation research, such as the International Atomic Energy Agency (IAEA) or the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR).

On the other hand, the largest anthropogenic (human-made) source of ionizing radiation can be attributed to medical procedures, specifically diagnostic imaging techniques that use ionizing radiation, such as X-rays and computed tomography (CT) scans. These medical procedures are essential for diagnosing various medical conditions.

To verify this information, you can refer to official reports and studies published by health organizations like the World Health Organization (WHO) or consult databases on medical radiation exposure maintained by relevant regulatory bodies in your country. These sources provide data on the usage of ionizing radiation in medical settings and its contribution to overall anthropogenic radiation exposure.