Radon concentration and radon effective dose rate in dwellings of some villages in the district of Ajloun, Jordan H.M. Al-Khateeb a,n , A.A. Al-Qudah b , F.Y. Alzoubi a , M.K. Alqadi a , K.M. Aljarrah a a Department of Physics, Jordan University of Science and Technology, P.O. Box 3030 Irbid 22110, Jordan b Department of Physics, College of Science/Girl Branch, University of Ha’il, P.O. Box 2440, Hail, Saudi Arabia article info Article history: Received 1 October 2011 Received in revised form 21 March 2012 Accepted 10 April 2012 Available online 13 April 2012 Keywords: Radon Indoor air Effective doses Different floor Building material Jordan abstract Indoor and soil radon concentrations were measured in the villages of Ayn-Jana, Ishtafena, Samta and Umm-Yanabe’ in the district of Ajloun, Jordan. Several factors that are strongly related to the radon concentrations are considered whether in soil such as its type or indoors such as room occupation type, floor level and building materials. In the village of Ayn-Jana, our results showed that the average radon concentration decreases gradually as the floor level increases. The highest concentration was found to be in the ground floor (35.5 75.0 Bq m 3 ) and the lowest was in the second floor (22.973.2 Bq m 3 ). Regarding the effect of ventilation rate in the same village, storage rooms revealed the highest concentration (38.875.4 Bq m 3 ) while the lowest concentration was in living rooms (33.8 74.4 Bq m 3 ). In the four villages, it was found that the highest radon concentration was in the dwellings made of clay (45.776.7 Bq m 3 ) and the lowest was in dwellings made of brick (33.976.4 Bq m 3 ). In general, the average indoor radon concentration in these villages was 36.372.3 Bq m 3 and it corresponds to an average effective dose rate of 0.9270.06 mSv yr 1 . These indoor radon concentrations as well as the annual effective dose are below the action level recommended by ICRP. The average radon concentration in soil of these villages was about 2.55 70.20 kBq m 3 , and it ranges from 2.08 70.12 kBq m 3 in the village of Ayn-Jana to 3.6270.13 kBq m 3 in the village of Ishtafena. & 2012 Elsevier Ltd. All rights reserved. 1. Introduction Radon is a natural inert gas produced continuously from decay of radium in natural decay chains of uranium and thorium in soil, rocks and water all over the earth. The radioisotope 222 Rn (usually called radon), produced from the decay of 238 U, is the main source of radiation exposure to human life (ICRP, 1993). Radon has a longer half-life (3.83 days), while other isotopes, 220 Rn (usually called Thoron) and 219 Rn (usually called Actinon), produced from 232 Th and 235 U respectively, are usually less significant because of their much shorter half-lives. Therefore, radon is the most dominant hazardous radionuclide. If radon is inhaled, it decays in lungs by means of alpha-emission and causes damages as the emitted alpha particles strike the lung tissues, resulting in lung cancer in the long term (ICRP, 1993; Bochicchio et al., 1988; Field et al., 2000). Radon is considered to be the second leading cause of lung cancer after smoking. Worldwide studies were conducted to measure and tabulate radon concentration in soil, air and water to end up with recommendations as well as to build databases (UNSCEAR, 2000; Al-Kofahi et al., 1992; Abu-Jarad et al., 2003; Magalhaes et al., 2003; Srivastava, 2004; Akrama et al., 2005; Diyuna et al., 2005; Friedmann, 2002; Pouloa et al., 2005). In Jordan, several indoor radon surveys have been carried out. For example, Al- Kofahi et al. (1992) studied radon levels in the city of Irbid while Abumurad et al. (1997) and Khatibeh et al. (1997) conducted comprehensive studies of radon levels covering the main cities in Jordan. Rabadi and Abumurad (2008) measured radon concentra- tions in dwellings, soil and water of Ajloun city. As a comple- mentary, we measured radon concentrations indoor and in soil in the villages of Ayan-Jana, Ishtafena, Samta and Umm-Yanabe’ in the district of Ajloun, in order to assess public exposure to radon. The district of Ajloun has more than 130,000 inhabitants, who constitute about 4% of the Jordan’s total population. Ajloun city lies in northwest of Jordan at about 70 km from Amman, capital Jordan, and at about 770 m above sea level. The villages under investigation lie in forests of green oak and pine trees around the city and they are at about 900–1100 m above sea level. No standard pattern for houses in these villages is noticed and they typically consist of three up to four rooms built of stones, cement and bricks while old houses are made of clay and stone. Contents lists available at SciVerse ScienceDirect journal homepage: www.elsevier.com/locate/apradiso Applied Radiation and Isotopes 0969-8043/$ - see front matter & 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.apradiso.2012.04.009 n Corresponding author. Current address: Basic Sciences Department, College of Medicine, King Saud Bin Abdulaziz University for Health Sciences, P.O. Box 22490, Riyadh 11426, Saudi Arabia. Fax: þ966 1 252 0088x47130. E-mail addresses: hkhateeb@just.edu.jo, khateebh@ksau-hs.edu.sa (H.M. Al-Khateeb). Applied Radiation and Isotopes 70 (2012) 1579–1582