Final answer:
The average annual manmade radiation exposure for an adult in the U.S. is part of the total 620 mrem total radiation exposure, with additional contributions from medical sources and other human activities included.
Step-by-step explanation:
The query regards the amount of manmade radiation exposure per year. For a typical adult in the United States, the average dose from artificial radiation sources, which includes medical procedures and other manmade contributions, is considered to be a part of the total annual radiation exposure of approximately 620 mrem. Notably, this also comprises natural radiation from cosmic rays, radon, and terrestrial sources. While cosmic rays provide an average exposure of about 0.40 mSv/y, airline industry personnel average about 2 mSv/y due to altitude factors. A 12-hour flight might contribute 0.02 to 0.03 mSv to a person's annual radiation dose.