Radon Concentrations in Selected Samples of Tap Water in Baghdad Government / Iraq

Radon gas is a significant health threat linked to thousands of preventable deaths each year. In this research, radon concentrations are measured in 136tap water samples collected from 34different places of Baghdad city, Iraq, using the electronic radon detector RAD-7 (Durridge Co., USA). The results of radon concentration varies from (0.012) to (0.283) Bq/L with a mean value of (0.111) Bq/L. The annual effective dose in Ingestion (stomach) and Inhalation (lungs) per person for children and adult is also calculated. The total annual effective dose of children and adults were (5.676) and (2.838) μSv/y respectively. At last may be concluded, the results of radon concentrations and annual effective dose in all samples show no significant radiological risk for the inhabitants in the reign study.


INTRODUCTION
Radon is a naturally occurring inert, radioactive, tasteless and odorless gas with half-life (3.824) days.Radon is produced from the radium , in decay series of U 238 .It has a density 7.5 times higher than that of air.It dissolves in water and can readily diffuse with gases and water vapor. In ecent decades, the studies are show that, under normal conditions more than 70% of total annual radioactive does received by people originates from natural sources of ionizing radiation, where by 54% is due to inhalation and ingestion of natural radioactive gas radon Rn 222 and its decay products.Exposure to radon via inhalation in closed rooms is the cause of about 10% of all deaths from lung cancer (ICRP, 1993;Prasad et al., 2009).However, a very high level of radon in drinking water can also lead to a significant risk of stomach and gastrin testier cancer (Kendal and Smith, 2002).Many studies have been conducted worldwide to determine its concentration in different environmental media in order to reduce its adverse effects on human beings (Hamzeh et al., 2012;Rani et al., 2013;Abojassim, 2013;Domenico et al., 2014;Abojassim et al., 2015).The aim of the present study is to investigate the radon in tap water used for drinking in Baghdad city of Iraq.

Area of study:
Baghdad is the capital of the Republic of Iraq, as well as the largest city in Iraq, which has an area of (204.2) km 2 , located along the Tigris River, at Latitude (33°20) north, longitude (44°26) east (Wiet, 1971;Stanek, 2012).In the present study (30) regions were chosen as fair distribution.The regions were determined using (GIS) as shown in Fig. 1.Table 1 show the sites studied which it is content of location name, sample code and coordinate of area under study.

MATERIALS AND METHODS
In the present study, radon concentration is measured in 136 tap water samples collected from 34 locations in Baghdad government, Iraq, using RAD-7, an electronic radon detector (Durridge Co., USA).From each location, four water samples were taken and analyzed for radon concentration.The water collected directly from the tap is used by the residents.The water samples were taken in 250-mL vials.In the present research, as a sample was collected, it was analyzed immediately on the entire sampling site.The time difference between taking the sample and analyzing it was few minutes, so no decay of radon in the water occurred.The RAD-7 detector converts alpha radiation directly to an electric signal.RAD-7 has the ability to distinguish between old and new radon (DURRIDGE, 2012).Figure 2 and 3 show the Experimental laboratory and schematic diagram of RAD-7 H 2 O respectively.RAD H 2 O gives results after a 30-min analysis with a sensitivity that matches or exceeds that of liquid scintillation methods.The RAD H 2 O method employs a closed loop aeration scheme, whereby the air volume and water volume are constant and independent of the flow rate.The air recirculates through the water and continuously extracts the radon until the state of equilibrium develops.The RAD H 2 O system reaches this state of equilibrium within about 5 min, after which no more radon can be extracted from the water.The extraction efficiency or percentage of radon removed from the water to the air loop is very high about 94%   for a 250-mL sample.The exact value of the extraction efficiency depends somewhat on ambient temperature, but it is almost always well above 90%.The RAD-7 detector converts alpha radiation directly to an electric signal.
As per EPA recommendations that all continuous radon monitors be calibrated at least every 6 months in a radon calibration chamber, the instrument was calibrated recently.The spectrum obtained from RAD-7 at the end of a run was carefully observed and there were clearly defined peaks and no noise across the spectrum.The peaks were located in the middle of the windows, which indicate the perfect working order of the instrument and hence reliable and accurate readings.
Radon enters human body through ingestion and through inhalation as radon is released from water into air.Therefore, radon in water is a source of radiation dose to stomach and lungs: • For ingestion, the annual effective dose was calculated using the formula (Somlai et al., 2007): where, E is the effective dose from ingestion (Sv), K the ingesting dose conversion factor of 222 Rn (2×10 -8 for children and 1×0 -8 Sv/Bq for adults (UNSCEAR, 1993).C Rn is the radon concentration in Bq/L, KM is the water consumption (2 L/day), t is the duration of consumption (365 d) (WHO, 2004).• For inhalation, the parameters used are (UNSCEAR, 1993;WHO, 2004): o Ratio of radon in air to radon in tap water supply was in the range of 10 -4 Bq/m 3 o Average indoor occupancy time per person was 7000 h/y o Equilibrium factor between radon and its progeny was equal to 0.4 o Dose conversion factor for radon exposure was 9 nSv (Bq h/m 3 ) -1 .
The annual effective dose due to inhalation corresponding to the concentration of 1 Bq/L in tap water was 2.5 mSv/y.

RESULTS AND DISCUSSION
The results for radon concentration in tap water samples are shown in Fig. 4. All samples in this study have radon concentrations except samples (B31, B32, B33 and B34) which are not detected by detector; therefore we exclude them from the result.The radon concentration varies from 0.012 Bq/L in sample code B29 (MASHTAL) to 0.283 Bq/L in sample code B2 (ZAHRA DISTRICT) with an average value of 0.111 Bq/L.The results of radon concentrations values in all samples were compared with the World Health Organization (WHO, 2008) (mean the radon concentrations in tap water from surface waters equals 0.4 Bq/L), it was observed that the recorded values were well within the safe limit.
The annual effective dose in the ingestion (stomach) and inhalation (lungs) per person for child and adult of age group were estimated in this research.Table 2 shows the values of the annual effective dose per person caused by different tap water samples in this

Fig. 4 :
Fig. 4: Results of radon concentrations in tap water samples

Table 1 :
The studied sites in Baghdad city

Table 2 :
Results of annual effective dose in tap water samplesNo.