Antonyms for natural radiation include artificial radiation, man-made radiation, and synthetic radiation. These terms refer to radiation that is produced by humans through various activities, such as nuclear power plants, medical procedures, and industrial processes. While natural radiation occurs spontaneously in the environment, artificial radiation is often the result of deliberate human actions that increase the amount of radiation in a particular area. Unlike natural radiation, which is relatively harmless in low doses, exposure to high levels of artificial radiation can have serious health effects, including cancer, genetic mutations, and radiation sickness. Therefore, it is essential to monitor and regulate artificial radiation to protect human health and the environment.