How Average Americans Are Exposed to About 620 Millirem of Radiation Each Year

Average Americans are exposed to a significant amount of radiation each year, primarily due to both natural and man-made sources. This exposure totals around 620 millirem (mrem) annually, which is generally considered quite safe. Let's explore the various ways in which Americans are exposed to radiation.

Radiation Exposure Sources

620 millirem of radiation exposure per year can be broken down into two main categories: natural background sources and man-made sources. Here is a detailed look at each category:

1. Natural Background Radiation and Cosmic Rays

Approximately half of the 620 mrem comes from natural background radiation, primarily from radioactive isotopes in the soil and cosmic rays. This type of radiation exposure is increased for those living at higher altitudes, as the atmosphere provides less shielding from these cosmic rays.

There are two main contributors to natural background radiation:

Cosmic Radiation: This radiation is primarily associated with solar radiation and cosmic rays that the atmosphere normally shields us from. During flights, passengers are exposed to a higher dose of cosmic radiation, as the protective atmosphere is thinned at high altitudes. Radiation from Rocks and Soil: Rocks and soil, especially those containing uranium and thorium, contribute to natural background radiation. On average, an acre-foot (about 1233 cubic meters) contains around 5.5 pounds (12 kg) of uranium and thorium. These materials, while mildly radioactive, are consistently present in the environment.

2. Man-Made Radiation Sources

The other half of the 620 mrem exposure comes from man-made sources, which include medical, industrial, and commercial activities. These sources contribute to a variety of radiation exposures:

Medical Imaging: X-rays, CT scans, and other medical imaging procedures use radiation to diagnose and treat medical conditions. These procedures contribute a significant portion of the man-made radiation exposure. Radon Gas: Radon gas is a naturally occurring radioactive gas that can accumulate in very well-insulated and poorly ventilated buildings. Radon is a byproduct of the decay of uranium in the soil and can lead to significant health risks if levels are high. Naturally Occurring Radioactive Materials (NORMs): NORMs are naturally radioactive materials found in oil and gas products. Equipment and pipes used in the handling of these products, especially pipes, can become intensely radioactive. These materials can pose significant health risks if not managed properly. Laser Explosives Test Sites: The United States has detonated over 1000 nuclear devices near the Nevada Test Site in Las Vegas. While many of these were above ground, fallout from these tests has been taken up into trees. These trees, used in various forestry products, still contain some of this fallout, albeit at lower levels. Forestry Products and Stone and Concrete: Stone and concrete products, as well as forestry products, often contain trace amounts of radiation. This radiation is minimal but contributes to the overall exposure.

Conclusion

In summary, the 620 mrem of radiation exposure per year that average Americans experience is a combination of natural and man-made sources. While this level of exposure is generally considered safe, it is essential to understand the sources of radiation and take precautions where appropriate.