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What radiation levels are considered safe?

The first step is to determine what your estimated annual radiation dose level is. There are many sources of radiation, some natural, and some man-made. First, let's take a look at these sources:

Cosmic Radiation

This is radiation from outer space, from the Sun and other stars. It is partly blocked by the Earth's atmosphere, so the higher your altitude, the less air is present to stop it, and the higher the levels. It varies from around 25 mrem a year at sea level, to around 50 mrem a year if you live at an altitude of 1 mile. At two miles, it would be around 100 mrem a year.

This is the reason that you get a small radiation dose when you take an airplane flight. Planes fly at altitudes of several miles, though fortunately the length of a flight is only a few hours. A typical dose rate is 0.5 mrem per hour of flight.

Terrestrial Radiation

This is due to radiation from uranium, thorium, and other radioactive materials naturally found in the soil. An average value is around 30 mrem a year, though this can be much less along the coasts, around half as much. And it can be twice as much in states such as Colorado. This USGS map shows typical radiation levels around the USA.

Inhaled Radon is estimated at around 200 mrem a year.

If you live in certain parts of the world, like certain villages in India and Brazil that have high levels of thorium in local sands, the dose rate can be much higher. Kerala, India and Minas Garais, Brazil has rates of around 1,000 mrem a year.

Radiation in Food

Foods naturally contain Carbon-14 which is radioactive, as well as Potassium, of which a small amount is radioactive. This results in an average dose of around 20 mrem a year. Also, some plants and animals naturally accumulate radioactive materials, resulting in higher than background dose rates.

You and other People

You naturally contain Potassium, Carbon-14, and other radionuclides. This makes you radioactive. To the tune of around 40 mrem a year. Other people are also radioactive, so you get slight doses from being around other people as well.

Other Sources of Radiation

Nuclear weapons fallout is estimated to be less than 1 mrem a year.

Watching TV gives you a dose of about 1 mrem a year.

Porcelain false teeth or crowns give you around 0.1 mrem a year.

While it is true that there is a slight increase in radiation does due to living close to a nuclear power plant, typically on the order of 0.01 mrem a year (insignificant), the average dose from living near a coal fired power plant is three times as high! This is due to the release of uranium/etc naturally mixed in with the coal.

If you use a plutonium powered pacemaker, your yearly dose rate is about 100 mrem. If your spouse has one, you get around 7.5 mrem a year. Apparently there are only around 100 people in the USA with such a device.

Radiation from X-Rays and Medical Tests

According to the American Nuclear Society, the following are the typical dose levels from various medical tests:
  • Extremity (arm, leg, etc) Xray: 1 mrem
  • Dental Xray: 1 mrem
  • Chest Xray: 6 mrem
  • Nuclear Medicine (thyroid scan): 14 mrem
  • Neck/Skull Xray: 20 mrem
  • Pelvis/Huip Xray: 65 mrem
  • CAT Scan: 110 mrem
  • Upper GI Xray: 245 mrem
  • Barium Enema: 405 mrem

OK, so total them up. You'll probably end up with around 300 mrem a year, perhaps more, if you take a lot of airplane flights, or have a lot of medical x-rays or nuclear medicine procedures.

As you can see, the major source of your radiation dose rate is due to natural sources, radon, cosmic radiation, and terrestrial radiation. Man made sources of radiation are completely swamped by these natural sources in most cases.

The average total dose rate for the USA is 360 mrem a year. It has been estimated that your chance of dying from cancer increases 10% if you accumulate a total of 250,000 mrem. This would be over 3,000 mrem a year over 80 years, for example. This estimates presumably assume a linear risk factor between dose and the chance of getting cancer, and there are those who now dispute such assumptions, which means the risks from low levels of radiation may be overstated.

A single dose of around 450 R (450,000 mR) is usually considered produce death in 50% of the cases.

If you're interested in measuring your local radiation levels, our line of radiation detectors may be of interest to you.

Thinking of buying a surplus CDV-700 or 715 detector? Be sure to read our report first.