­Radiation Exposure Dosage Chart:

This chart lists ionizing radiation only. Of all the types of non-ionizing radiation, only ultraviolet rays are cancer-causing agents.

  • 10,000 mSv (1,000,000 mrem) as a short-term and whole-body dose would cause immediate illness and subsequent death within a few weeks.
  • 1,000 to 10,000 mSv (100,000 to 1,000,000 mrem) in a short-term dose would cause severe radiation sickness with increasing likelihood of fatality.
  • 1,000 mSv (100,000 mrem) in a short-term dose will cause immediate radiation sickness in a person of average physical attributes, but would be unlikely to cause death.
  • Short-term doses greater than 1000 mSv (100,000 mrem) over a long period create a definite risk to develop cancer in the future.
  • At doses above 100 mSv (10,000 mrem), the probability of cancer (rather than the severity of illness) increases with dose.
  • 50 mSv (5,000 mrem) is thought to be the lowest dose at which cancer may occur in adults. It is also the highest dose allowed by regulation in any one year of occupational exposure.
  • 20 mSv/yr (2,000 mrem) averaged over five years is the limit for radiological personnel such as employees in the nuclear industry, uranium or mineral sands miners and hospital workers (who are all closely monitored).
  • 10-12 mSv (1,000-1,200 mrem) in one dose is the equivalent of a full body CT scan.
  • 3 mSv/yr (300 mrem) is the typical background radiation from natural sources in North America, including an average of almost 2 mSv/yr from radon in air.
  • 2 mSv/yr (200 mrem) is the typical background radiation from natural sources, including an average of 0.7 mSv/yr from radon in air. This is close to the minimum dose received by all humans anywhere on Earth.
  • 0.3-0.6 mSv/yr (30-60 mrem) is a typical range of dose rates from artificial sources of radiation, mostly medical. It includes bone density scans, dental X-rays, chest X-rays, and bone X-rays.
  • 0.01-.03 mSv (1-3 mrem) is typical radiation from a single coast-to-coast airplane flight. However, high-mileage frequent flying (100,000 to 450,000 miles per year) can range from 1 to 6 mSv (100-600 mrem) per year.

[sources: World Nuclear Association and Health.com]

Radiation Exposure

Radiation is everywhere. It's been part of our environment since the planet was born. Radiation exists in the atmosphere, the ground, the water and even within our own bodies. It's called natural background radiation, and it's perfectly safe.

Radiation affects your body by depositing energy in your tissues, which can cause cell damage. In some cases, this won't cause any effect. In others, the cell can become abnormal and later malignant. It depends on the strength and duration of the exposure. In the rare occurrence of a huge amount of radiation exposure in a short time, death can occur in a matter of days or hours. We call this acute exposure. Chronic exposure, on the other hand, is frequent exposure to low doses of radiation, over a long period. There can be a delay between initial exposure and consequent health effects. To date, the best information we have about health risk and radiation exposure comes from the survivors of the atomic bomb in Japan and people who work with radiation every day or receive radiation as medical treatment.

We measure amounts of radiation exposure in units called millirem (mrem). Higher readings are measured in mSv, which you can multiply by 100 to get mrem. In the United States, people receive an average annual dose of about 360 mrem. More than 80 percent of this dose comes from natural background radiation [source: DOE]. However, outside considerations greatly affect the average dose. Where and how you live affects the amount of radiation exposure you receive. For example, people who live in the Pacific Northwest part of the United States typically only receive about 240 mrem from natural and man-made sources. However, people in the Northeast receive up to 1700 mrem per year, mostly due to radon that is natural to rocks and soil. Is 1700 mrem safe? Take a look at the sidebar to see.

So what do you do if you're exposed? Find out on the next page.