On average, Americans receive an annual radiation dose of about 0.62 rem, with half of this dose coming from natural background radiation. The main source of background exposure is radon in the air, along with smaller amounts from cosmic rays and the Earth itself. The other half of the dose comes from man-made sources, such as medical, commercial, and industrial sources. Medical procedures account for the majority of human exposure to man-made radiation, with x-rays, mammography, and CT scans being common examples. These procedures do not involve radioactive material and are regulated by State health agencies. Additionally, all organic matter and water contain small amounts of radiation, resulting in an average internal dose of about 30 millirem per year. Overall, a yearly dose of 620 millirem has not been shown to cause harm to humans.
https://www.nrc.gov/about-nrc/radiation/around-us/doses-daily-lives.html