Calculating Radon Doses

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Radon levels (in Bq/m3) are used directly to control radon levels in homes and most workplaces. However, sometimes it is necessary to calculate the effective dose due to radon exposure for some workplaces.

ICRP develops dose coefficients to simplify the calculation of equivalent dose and effective dose for inhaled or ingested radionuclides.

In simplest terms, calculating the dose from inhaling radon involves multiplying the average radon level (e.g. in Bq/m3) by the time spent, and the right dose coefficient.

Effective dose = radon level × time × dose coefficient

Using the dose coefficient for most circumstances, breathing air with 50 Bq/m3 of radon (a typical worldwide value indoors) for one year gives an effective dose of 3 mSv.

For working indoors doing substantial physical activity, or for exposures in tourist caves, the recommended dose coefficient is higher, so breathing air with 50 Bq/m3 of radon for one year gives an effective dose of 6 mSv.

Details

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In most circumstances, ICRP recommends a dose coefficient of 3 mSv per mJ h m-3. Using the standard equilibrium factor assumption of F = 0.4 (the ratio between the concentration of radon progeny and radon-222) for most situations, this corresponds to 6.9 x 10-6 mSv per Bq h m-3.

For work indoors involving substantial physical activity, and exposures in tourist caves, ICRP recommends 6 mSv per mJ h m-3. Using the standard equilibrium factor assumption of F = 0.4, this corresponds to 1.4 x 10-5 mSv per Bq h m-3.

Where aerosol characteristics are significantly different from typical conditions; sufficient, reliable aerosol data are available, and estimated doses warrant more detailed consideration, it is possible to calculate site-specific dose coefficients using data provided in ICRP Publication 137.

Quotes from ICRP Publications

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Occupational Intakes of Radionuclides, Part 3: Publication 137 paragraphs 57-60

The present situation is a remarkable consistency between coefficients obtained by dosimetric calculations and conversion coefficients based on epidemiological comparisons…

For the calculation of doses following inhalation of radon and radon progeny in most circumstances, the Commission recommends a dose coefficient of 3 mSv per mJ h m-3 (approximately 10 mSv per WLM). The Commission considers this dose coefficient to be applicable to the majority of circumstances with no adjustment for aerosol characteristics. The corresponding dose coefficient expressed in terms of radon-222 gas exposure depends on the equilibrium factor, F, between radon gas and its progeny. Using the standard assumption of F = 0.4 for most situations, 3 mSv per mJ h m-3 corresponds to 6.9 x 10-6 mSv per Bq h m-3.

For the specific situations of work indoors involving substantial physical activity, and exposures in tourist caves, the Commission recommends a dose coefficient of 6 mSv per mJ h m-3 (approximately 20 mSv per WLM). Using the standard assumption of F = 0.4 for most situations, 6 mSv per mJ h m-3 corresponds to 1.4 x 10-5 mSv per Bq h m-3.

In cases where aerosol characteristics are significantly different from typical conditions; sufficient, reliable aerosol data are available; and, estimated doses warrant more detailed consideration, it is possible to calculate site-specific dose coefficients using the data provided…

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