Elsevier

Radiation Measurements

Volume 43, Supplement 1, August 2008, Pages S471-S474
Radiation Measurements

Comparative study of short- and long-term indoor radon measurements

https://doi.org/10.1016/j.radmeas.2008.04.053Get rights and content

Abstract

Short-term indoor radon measurements are used widely. Therefore, it is interesting to find out a correlation between these measurements and long-term measurements which reflect a better average radon concentration of individual measurement. To find the correlation between the two measurements of indoor radon concentrations at low radon levels, a study was carried out at 34 locations of King Fahd University of Petroleum & Minerals (KFUPM), Dhahran, Saudi Arabia using active and passive methods. In the short-term active method, a radon gas analyzer (AlphaGUARD) was used for a duration of 24 h in each measurement. In the long-term passive method, CR-39 based radon dosimeters were utilized for a period of 6 months, from January 2006 to June 2006. The short-term active measurements showed that the average, minimum and maximum radon concentrations were 19, 8 and 58Bqm-3, respectively, with a standard deviation of 8.6Bqm-3. The long-term passive measurements showed that the average, minimum and maximum radon concentrations were 25, 10 and 67Bqm-3, respectively, with a standard deviation of 12Bqm-3. The two measurements showed a poor correlation (R2=0.38). The long-term measurements showed on the average higher concentrations by a factor of 1.3.

Introduction

Natural radiations are the biggest sources of radiation exposure to the world population. The sources of natural radiation include cosmic radiation and terrestrial radiation which cause external and internal exposures. The annual average dose to the world population from natural radiation sources has been estimated to be 2.4 mSv of which one-third is the external exposure and two-third the internal exposure (Wang, 2002). The highest component of the annual equivalent dose comes from the inhalation of radon (222Rn) and its short-lived alpha-emitting decay products 218Po and 214Po. Alpha particles emitted from 222Rn, 218Po and 214Po deposit their energies to the tissues of the lungs, as a result, lung cancer might be produced (William Field et al., 2000; Lubin and Boice, 1997). Soil and rocks under houses plus building materials are ordinarily the principal contributors to indoor radon which is typically four or five times more concentrated than the radon outdoors, where greater air dilution occurs (Turner, 1995). There has been more measurement of radon and its short-lived decay products than of any other radioactivity except weapons test fall-out (Harley, 1992). International conferences were held recently to present and review the work on radon in different parts of the world (Fernandez et al., 2005, Sugahara et al., 2004). A variety of methods were developed to measure radon and its decay products which included active and passive methods, short- and long-term measurements. Different ionization chambers and scintillation counters were used in the active measurements of radon while thermoluminescent detectors, charcoal adsorption and nuclear track detectors (NTDs) were applied in the passive measurements of radon. In recent years, some research work has been carried out in the field of radon dosimetry in Saudi Arabia (Al-Jarallah and Fazal-ur-Rehman, 2006, Al-Jarallah and Fazal-ur-Rehman, 2005; Al-Mustafa et al., 2005, Abu-Jarad et al., 2003, Fazal-ur-Rehman et al., 2003). Because radon levels tend to vary from day to day and season to season, a short- term test is less likely than a long-term test to represent the home's average radon level (National Safety Council, USA, 2004; Arizona Radiation Regulatory Agency USA, 2007). Seasonal correction factors for short-term radon measurements are generally derived from consideration of the average variation of radon concentration in a large number of houses in many countries. However, these factors might not be appropriate in areas which are geologically very different (The University of Northampton, 2007).

A comparative study of short- and long-term measurements of indoor radon concentrations at low radon levels was carried out at 34 locations of King Fahd University of Petroleum & Minerals (KFUPM), Dhahran, Saudi Arabia using active and passive methods, respectively. These locations include offices (16), student dormitories (11) and faculty houses (7). In the short-term measurement, radon gas analyzer was used (Al-Jarallah, 2001), whereas in the long-term measurement, CR-39 NTDs based radon dosimeters were used (Al-Jarallah and Fazal-ur-Rehman, 2005). The results of this comparative study are presented in this paper.

Section snippets

Short-term measurements by active system

A radon gas analyzer type Alpha Guard 2000 PRQ from Genitron Instruments (Germany) was used to measure radon concentration (Al-Jarallah, 2001, Al-Jarallah et al., 2001). The measuring gas gets in diffusion mode via a large surface glass filter into an ionization chamber. Only the gaseous radon-222 may pass, while the radon progeny products are prevented to enter the ionization chamber. At the same time the filter protects the interior of the chamber from contamination of aerosol particles. This

Results and discussion

In the short-term measurement method, radon concentration was measured in each room every 1 h for a total period of 24 h. Fig. 2 shows one of these measurements, where the x-axis indicates the measurement time while the y-axis indicates radon concentration. The error bars in individual measurements are also shown in the figure. The uncertainty in individual measurement is better than 20% which is relatively high because of low radon concentrations. The short-term active measurements showed that

Conclusion

A comparative study of short- and long-term indoor radon measurements in KFUPM Buildings was carried out using active and passive techniques, respectively. The correlation between the two measurements was poor showing a linear correlation coefficient of 0.38. The long-term measurements showed on the average higher concentrations by a factor of 1.3.

Acknowledgment

The authors would like to thank Physics Department, King Fahd University of Petroleum & Minerals (KFUPM), Dhahran, Saudi Arabia for the research support.

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