Section: 16 | Relative Dose Ranges from Ionizing Radiation |
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John R. Rumble, ed., CRC Handbook of Chemistry and Physics, 103rd Edition (Internet Version 2022), CRC Press/Taylor & Francis, Boca Raton, FL.
If a specific table is cited, use the format: "Physical Constants of Organic Compounds," in CRC Handbook of Chemistry and Physics, 103rd Edition (Internet Version 2022), John R. Rumble, ed., CRC Press/Taylor & Francis, Boca Raton, FL.


Thomas J. Bruno

It is important to place in perspective the relative ionizing radiation dose acquired in common laboratory settings. The most commonly encountered source is a 63Ni source used in gas chromatographic electron capture detectors (ECDs) and in ion mobility spectrometers (IMSs) (Ref. 1). In both instruments, the source is sealed and has a radioactivity of 15 mCi. An exposure value cited refers only to normal operation; it does not consider exposures if the device is dismantled or allowed to overheat.


Natural background consists of the highly variable sum of all ubiquitous sources of ionizing radiation encountered on the planet (Ref. 2). Background in general can be divided into the following four major contributions:

Contribution Average dose, mrem/year, United States
Terrestrial contribution 21
Cosmic contribution 33
Airborne radon (and daughter) contribution 228
Internal consumption contribution 29
Total Natural Background 311

In the United States, the average natural background ionizing radiation level is 311 mrem. This is variable due primarily to differences in altitude and primordial radionuclides and their daughters. For example, the averages in the United Kingdom and Finland are 200 mrem and 700 mrem, respectively. Higher levels are found at higher altitudes and regions with a larger radon budget. Within the United States, for example, the background in Denver, Colorado is approximately 450 mrem, while in most of Florida, it is closer to 230 mrem. The terrestrial contribution primarily arises from radionuclides of potassium, uranium, and thorium, and their daughters. The cosmic contribution arises primarily from muons, neutrons, and electrons, and varies with terrestrial magnetic field and altitude. The internal contribution results from consuming radionuclides of potassium and carbon in food and water. By far the largest contribution is from radon and radon daughters. The radon budget results from terrestrial sources of uranium (Ref. 3). Within the United States, the action level requiring indoor radon mitigation is reached when a measurement results in 4 pCi/L (150 Bq/m3) or higher. This level of radioactivity results in a dose of between 300 mrem and 700 mrem, assuming 80% indoor occupancy. The range cited results from different dose conversion coefficients and dosimetric models used by different agencies (Ref. 4).

Typical Incremental Increases above Background

Exposure to ionizing radiation in the laboratory results in a dose level in excess of the background levels discussed above (Ref. 5). The following charts place in perspective the additional dose received above background for some common exposures. Since in Figure 1 the ranges are dwarfed by tobacco use, Figure 2 is presented with this contribution removed. This is significant because the tobacco dose is specific to the lungs, and not the whole body. A more relevant comparison for Figure 1 would be obtained by multiplying the listed 8000 mrem by the tissue-weighting factor for the lungs, 0.12.

The high incremental level associated with tobacco use (1 mrem/hr while smoking) results from the accumulation of 210Po and 210Pb (radon daughters that are alpha and gamma emitters) on tobacco leaves. The incremental dose accrued by air travel is dependent on altitude, with higher levels associated with higher altitudes, and will range between 0.3 mrem/hr and 0.5 mrem/hr. The incremental dose due to medical imaging or radiation treatment can be misleading. For many individuals the dose can be close to zero, but in the case of radiation treatment it can be much higher. Indeed, patients given certain radiation treatments become incremental sources themselves, resulting in incremental dosage above background to attending medical personnel, caregivers, and the general public. The entry for clocks in both Figures 1 and 2 is for older (even antique) clocks that have dials coated with Ra/ZnS paint to provide illumination.

figure 1 described below

FIGURE 1: A comparison of increments to natural background levels, explicit for the 15 mCi 63Ni sources used in electron capture detectors and ion mobility spectrometers.

figure 2 described below

FIGURE 2: The same comparison as in Figure 1, but with tobacco use removed. Thus, the data shown above are all whole-body dosages.

In instrumentation such as ECDs and IMSs, the devices are sealed sources in shielded enclosures, and are covered by general licenses in the United States. They are designed with inherent radiation safety features so that they can be used by persons with no radiation training or experience (Ref. 6).


  1. Bruno, T. J., and Svoronos, P. D. N., CRC Handbook of Basic Tables for Chemical Analysis – Data-Driven Methods and Interpretation, Fourth Edition, CRC Press/Taylor & Francis, Boca Raton, FL, 2021. []
  2. Metting, N. F., Ionizing Radiation Dose Ranges, Office of Science, U.S. Department of Energy, <>, 2010.
  3. NCRP Report 160, Ionizing Radiation Exposure of the Population of the United States, Recommendations of the National Council on Radiation Protection and Measurements, Bethesda, MD, 2009.
  4. Background Information on “Update on Perspectives and Recommendations on Indoor Radiation,” position statement of the Health Physics Society, 2009.
  5. Johnson, T. E., and Fellman, A., Estimated Dose and Risk from 15mCi 63Ni Sealed Source Type NR-348-D-111-B, Report Prepared for Hewlett Packard Co., CSI Radiation Safety, Gaithersburg, MD, 1999.
  6. <>, accessed July 2018.
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