In deciding whether to visit ground zero at Trinity Site, the following information may prove helpful to you.
Radiation levels in the fenced, ground zero area are low. On an average the levels are only 10 times greater than the region's natural background radiation. A one-hour visit to the inner fenced area will result in a whole body exposure of one-half to one milliroentgen.
To put this in perspective, a U.S. adult receives an average exposure of 90 milliroentgens every year from natural and medical sources. For instance, the Department of Energy says we receive between 35 and 50 milliroentgens every year from the sun and from 20 to 35 milliroentgens every year from our food. Living in a brick house adds 50 milliroentgens of exposure every year compared to living in a frame house. Finally, flying coast to coast in a jet airliner gives an exposure of between three and five milliroentgens on each trip.
Although radiation levels are low, some feel any extra exposure should be avoided. The decision is yours. It should be noted that small children and pregnant women are potentially more at risk than the rest of the population and are generally considered groups who should only receive exposure in conjunction with medical diagnosis and treatment. Again, the choice is yours.
At ground zero, Trinitite, the green, glassy substance found in the area, is still radioactive and must not be picked up.
Typical radiation exposures for Americans
Per The National Council on Radiation Protection
On hour at ground zero = ½ mrem
Cosmic rays from space = 40 mrem at sea level per year
Radioactive minerals in rocks and soil = 55 mrems per year
Radioactivity from air, water, and food = anywhere from 20 to 400 mrem per year
About 22 mrem per chest X-ray and 900 mrem for whole-mouth dental X- rays
Smoking one pack of cigarettes a day for one year = 40 mrem
Miscellaneous such as watch dials and smoke detectors = 2 mrem per year