Effective Dose Radon 222 of the Tap Water in Children and Adults People; Minab City, Iran

222Rn is a radioactive, odorless, and colorless element which has a half-life of 3.83 days. One of 222Rn main resources are Groundwater (wells, springs, etc.). Hence, the use of groundwater with high concentration of 222Rn can increase the risk of lung and stomach cancers. Concentration of 222Rn in tap water of Minab city in two temperatures 5 and 15 ºC was measured by radon meter model RTM1668-2. The effective dose was calculated by equations proposed by UNSCEAR. Geometric mean concentration of 222Rn in drinking water was found to be 0.78±0.06 and 0.46±0.04 Bq/l at 5 and 15 °C (p value<0.05), respectively. The effective doses were 0.006 and 0.003 mSv/y for adults, and 0.011 and 0.007 mSv/y for the children, respectively (p value<0.05). Besides, the effective dose for adult through inhaling 222Rn at 5 and 15 °C were estimated 0.0021 and 0.0012mSv/y, respectively. Geometric mean concentration in 222Rn drinking water and effective dose received from drinking water and inhalation of 222Rn is lower than WHO and EPA standard limits. Increasing temperature of drinking water will decrease the effective dose received. Annual Effective dose received from inhalation and consumption of 222Rn in drinking water in children is more than adults.

DNA lung cells and leads to lung cancer in the population (Todorovic, Nikolov, Forkapic, Bikit, & Mrdja, 2012;Motesaddi, Fakhri, Alizadeh, Mohseni, & Jafarzadeh, 2014). European Commission and the World Health Organization has proposed concentration of 222 Rn in the drinking water, 100 Bq/l as the standard limit (WHO, 2006). EPA 11 Bq/l, has been suggested as the maximum concentration Level (MCL) of 222 Rn in drinking water (Environmental Protection Agency, may 2012). Many studies have shown that groundwater resources rather than surface water resources have much higher concentration of radioactive materials such as 222 Rn (Amin, 2013;Rožmarić, Rogi, Benedik, & Štrok, 2012). The total indicative dose (TID) induced by radioactive substances ( 3 H, 40 K, 222 Rn) as well as those produced through 222 Rn decayed in drinking water is reported to be 0.1 mSv/y by WHO and the European committee WHO, 2004). Due to the exit of 222 Rn during water transfer in distribution network, water transfer from one container to another, storing and boiling water, determining the standardized effective dose induced by 222 Rn is difficult (Ishikawa, Tokonami, Yoshinaga, & Narazaki, 2005). Hence, the effective standard level dose 0.1 mSv/y is used for the analysis. In the present study, the effective dose of 222 Rn received by children and adult age groups in Minab drinking water was calculated.

Study Area
Minab city with a population of approximately 90 thousand people is located in geographic coordinates 27º06'40N and 57º05'52, at an elevation of 45 meters above sea level ( Figure 1). The city is located in a hot and humid region and the water consumption per capital was high. The only water resources in this town are three deep wells (Groundwater source), the water of which is pumped out and distributed with no purification process.

Sample Collection
Since the retention time of water in the distribution network is effective on the concentration of 222 Rn (Ishikawa, Tokonami, Yoshinaga, & Narazaki, 2005), thus, the sampled locations were determined from the beginning to the end of the distribution network. For 4 consecutive months, the sampling was done in 10 regions of the town. Meanwhile, 25 samples were selected from each region. During each stage of time, a total of 250 samples, each containing 2l of city tap water were obtained from 10 regions Sampling was conducted according to the proposed method (EPA). spectrophotometry, inductively coupled plasma/mass spectrophotometer, gamma spectrophotometry and liquid Scintillation (Rožmarić, Rogi, Benedik, & Štrok, 2012). Recently, many studies measure the concentration of 222 Rn portable devices, such as RAD7 RTM (Mehra and Bala, 2013;Ju, Ryu, Jang, Dong, & Chung, 2012;Todorovic, Jovana Nikolov, Sofija Forkapic, Istvan Bikit, & Dusan Mrdja, 2012;Lee & Kim, 2006). Hence, in this study a model of portable alpha spectrophotometry RTM1688-2 was used to measure 222 Rn in drinking water.
To determine the effect of water temperature on the diffusion rate 222 Rn of water, measurements was done at 5 and 15ºC temperatures. According to measurement of 300 mL, after the sample size reached the intended temperature, the device was placed in a closed cycle (Figure 2). The time for balance between concentration of 222 Rn and its decay products (daughters 222 Rn) is 4 hour approximately Mehra & Bala, 2013;Lee & Kim, 2006). Hence, the 4 hour mean concentration of 222 Rn (Bq/l) and the initial temperature (ºC) was recorded. Figure. 2. Measurement water 222 Rn levels by RTM 1688-2 device, manufactured by Sarad corporation in Germany.

Calculation of effective dose (Ingestion)
To determine 222 Rn annual effective dose received in the stomach from water consumption, Equation 1 was used (Sarad, 2009). In this equation E: the annual effective dose received by mSv/y, K: Coefficient conversion concentration of 222 Rn to effective dose According to mSv/Bq, KM: Annual water consumed l/y, C: the concentration of 222 Rn depending on Bq/l and T: the period of water consumption in the study, here was 365 days (Somlai, Tokonami, Ishikawa, Vancsura, & Gáspár, 2007).

Calculation of the Effective Dose (Inhalation)
In order to estimate the effective dose received annually through inhaling 222 Rn of underground water, the conversion coefficient of 2.8 µSv.lit/Bq was used (Radiation, 2000). The annual geometric mean concentration of 222 Rn (Bq/l) was multiplied by the coefficient 2.8×10 -3 , and the effective dose received annually through inhaling 222 Rn was estimated in mSv/y.

Statistical Analyses
Statistical analyses were done via SPSS 16, using One-way ANOVA method and correlation coefficient. The results were also stated in mean and standard deviation forms.

Results
Geometric mean and range of concentration of 222 Rn in drinking water was measured 0.78±0.06 Bq/l and 0.19-1.7 Bq/l at 5 ºC and 0.46±0.04 Bq/l and 0.16-1.45 Bq/l at 15 ºC, respectively (p value<0.05). (Tables 1 and  2). The  As it can be seen in Table 3, the range concentration of 222 Rn in drinking water of Amasiya (0.39-1.17 Bq/l) is within the range concentration of 222 Rn drinking water of Minab (0.16-1.7 Bq/l). The range concentration of 222 Rn in drinking water of Tehran (27.7-74.3 Bq/l), Buvaji (12-41 Bq/l), Uberiya (5.9-65.7 Bq/l), and Islamabad (25.9-158.4 Bq/l) are much greater than Minab and Amasiya cities. Difference concentration of 222 Rn in these towns (Amasiyia and Minab) may be due to different factors such as concentration of 222 Rn in the water source, geological substrate type, water retention time and temperature during the measurement (Yiğitoğlu, Öner, Yalim, Akkurt, Okur, 2010). Groundwater resources (springs, wells, etc.) due to contact with the various layers of the earth, has more Total Dissolved Solid (TDS), including radioactive materials relative to surface waters (rivers, lakes, etc.). Layers of earth containing igneous rocks (granite) are larger, with higher concentration of radioactive material 235 U (Rožmarić, Rogi, Benedik, & Štrok, 2012;Rezaei & Jalili-Majareshin, 2011). Since the 222 Rn is the product of series of 235 U decay, it can be expected that concentration in groundwater which cross from substrate type, are higher (Przylibski, Mamont-Cies´la, Kusyk, Dorda, & Kozlowska, 2004). Drinking water sources in Tehran, Buage, Umbria and Islamabad are of underground type similar to Minab and Amasia. However, concentration of 222Rn in the drinking water of Minab and Amasia is different. This could be due to differences in geological structure, measuring temperature and retention time of water. The effective dose received by www.ccsenet.org/gjhs Global Journal of Health Science Vol. 8, No. 4;2016 children age group at the temperature of 5 °C (0.011 mSv/y) was 1.57 times more than of that at 15 °C (0.006 mSv/y). For adults it was 2 times bigger. Since the mean concentration of 222 Rn at 5 °C (0.78±.06 Bq/l) is more than that of 15 °C (0.46±.04 Bql -1 ), the effective dose received is higher at this temperature. The effective dose received annually by adults and children from drinking water at 5 and 15 °C was below the standard 0.1 mSv/y. The activated coefficient of converting 222 Rn to effective dose is higher in children group than adults . The effective dose received from drinking water in this age group at the temperatures of 5 and 15 °C are 1.83 and 2.33 times bigger than adults'.  (Xinwei, 2006) 0.03-0.14 Bovaji/China  0.0002 0.0004 Balaton/Netherlands (Kralik, Friedrich and Vojir, 2003) 0.005 Australia (Sahin, Çetinkaya, Saç, & Içhedef, 2013) 0.00014-0.00003 0.000122-0.0003 -Gotaya/Turkey Effective dose due to inhalation of 222 Rn from drinking water is much lower than the standard 1mSv/y effective dose due to 222 Rn inhalation (Villalba, Sujoa, Cabrera, Jime´neza, & Villalobos, 2005). Effective dose received from 222 Rn inhalation from drinking water at 5 ºC, is 1.82 times bigger than that of temperature 15 ºC. As can be seen in Table 4, the effective dose received by children (0.011 and 0.007 mSv/y) and adults (0.006 and 0.003 mSv/y) at a temperature 5 and 15 ºC of drinking water of Minab city is greater than Tehran (0.000129 and 0.00066 mSv/y), Balaton (0.0004 and 0.0002 mSv/y), Mashhad (0.00029 mSv/y for adult), Australia (0.005 mSv/y for adult), Gotaya (0.000122-0.0003 mSv/y) and Kastomono (0.00032-0.00093 mSv/y in summer and 0.00049-0.0008 mSv/y in the spring). 222 Rn concentration range in drinking water of Tehran (27.7-74.3 Bq/l) is more than Minab City (0.16-1.7 Bq/l). However, due to the low effective dose conversion factor activity (0.35×10 -8 Sv/Bq) and capital annual consumption of water (children 75lit and adults 100lit), a lower effective dose is received by people of Tehran (N. Alirezazadeh, 2005). Lower effective dose in other cities can be due to low concentration of 222 Rn, conversion factors and capital water consumption. Effective dose of induced inhalation in Minab (0.0021 and 0.0012 mSv/y) is higher than cities of Mashhad (0.0004 mSv/y), Gotiya (0.00003-0.00014 mSv/y) and is lower than cities of Tehran (0.01mSv/y), and Bovaji (0.03-0.14 mSv/y). However, effective dose of inhalation activity conversion factor of Minab (2.8 µSv/y) is higher than Tehran cities and Bovaji (1.8 µSvy -1 ) (Xinwei, 2006;N. Alirezazadeh, 2005), but due to the higher concentration of 222 Rn in tap water, inhalation effective dose is higher in Minab city.

Conclusion
Geometric mean concentration of 222 Rn in drinking water at temperatures 5 and 15 ºC (0.78±0.06 and 0.46±0.04 www.ccsenet.org/gjhs Global Journal of Health Science Vol. 8, No. 4;2016 Bq/l) are lower than EPA and WHO standard limits. Annual Effective dose received from inhalation and consumption of 222 Rn in drinking water in children is more than adults (p value<0.05). Also, effective dose received in both age groups, are much lower than EPA and WHO standard limits. Increasing the temperature reduces the effect on concentration of 222 Rn in drinking water, followed by a reduction in received effective dose. Hence, it is recommended to reduce the effective dose received in the cities with high concentration of 222 Rn in drinking water, water ingestion be at higher temperature.