Man-made radiation consists of the same types of radioactive materials with the exception of the heavy nuclei. In fact, the annual variation in natural background is much larger than the entire LANL contribution.
Terrestrial radiation varies daily, seasonally, and geographically.
Different soil types also affect radiation levels. Placement of the dosimeters is important because dosimeters that are placed in a narrow canyon will receive terrestrial radiation from the walls and the floor of the canyon and will show higher exposures than dosimeters placed on a flat surface where no walls are nearby. Cosmic radiation doses increase with increasing elevation because there is less atmosphere to attenuate the radiation. The fluctuations of terrestrial and cosmic radiation sources make it difficult to detect an increase in radiation levels from LANL sources, which are typically much smaller than the magnitude of the natural fluctuations. In an attempt to evaluate the impact from Laboratory operations, TLDs are placed around the Laboratory and in the surrounding communities.