Tissue Annual Effective Doses Estimation from Natural Occurring Radioactive Materials at Ramlet Homayier Area-South Western Sinai, Egypt

γ-ray spectrometric survey shows many radioactive anomalies within the ferruginous siltstone of the lower Um Bogma Formation. The high average eU/eTh values indicate an addition of uranium (migration in) in both the two regions. The results obtained from field measurements show that the indoor annual effective dose in Ramlit Homayier and Heboush area are (48.71 mSv) and (19.70 mSv) respectively while that estimated by HPGE detector were (1.90 and 0.08 mSv). According to AEDE obtained, the dose delivered to each tissue is estimated and it reveals high dose risk to public derived from the exposure to subsurface NORM in Ramlet Homayier more than Heboush area for most body tissues Consequently staying in such levels of NORM requires a high caution and awareness to minimize the health risk accompanied to daily exposure of public and applying radiation protection principals to achieve a better safe working and living environment.


Fig. 1: Geologic map of Ramlet Homayier area
For the Paleozoic succession the main subdivisions, include three major lithostratigraphic units that comprise from base to top: a): Sarabit El Khadim, Abu Hamata and Adedia Formations as discussed by Soliman and Abu El Fetouh [1], b): Um Bogma Formation [2]. c): El-Hashash, Magharet El-Maiah and Abu Zarab Formations [1], Abu Thora Formation [3]. The unconformity surfaces were recorded between Um Bogma Formation and other lower and upper formations figure (1) The succession of the Paleozoic rocks exposed in most parts of the mapped area consists of seven formations namely from the oldest to youngest: Sarabit El Khadim, Abu Hamata, Adediya, Um Bogma, El Hashash, Magharet El Maiah and Abu Zarab Formations.
Um Bogma Formation is the most important formation in the Paleozoic succession from the radioactivity and mineralization points of view.

Materials and Methods
The field radiometric measurements of eU (ppm), eTh (ppm) and K% were obtained using a portable differential gamma ray spectrometer model Rs-230 BGO Super-Spec, serial No. 4333, the reading were given directly each 30 second.
Two techniques were used measurements of the annual effective dose. i) Radon gas measurements using Solid State Nuclear Track Detectors (SSNTD): In this technique, a closed cup contains SSNTD's was used according to the following procedures.
The applying of closed cup technique in which the detector after cutting into pieces of about 1 cm 2 and, numbered then, hanged at the inside volume of the cup from the bottom is inserted inside a close can (cup) with specific dimensions, then covered with a filter paper or a membrane. This configuration admits detectors only radon gas through diffusion process but exclude its decay products. Radon gas inside the enclosure decays through its chain of decay products, producing a track density which is proportional to the detector's radon gas exposure [4].
After exposure time (30 day), the cups were recovered and the detectors were collected and chemically etched in a thermostatically-controlled water bath at specified temperatures with an aqueous solution of NaOH at specified molarities and etching times, the etchant solution is 6.25 N NaOH and the etching temperature was maintained at (70 ±1) ºC for 8 hours.  .
A dose coefficient of 3 mSv/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 and this corresponds to 6.9 x 10 -6 mSv/Bq h m -3 [5].
For indoor workers involving substantial physical activity, and exposures in tourist caves, ICRP recommends 6 mSv/mJ h m -3 . Using the standard equilibrium factor assumption of F = 0.4, this corresponds to 1.4 x 10 -5 mSv/Bq h m -3 [5].
Calculating the dose from inhaling radon involves multiplying the average radon level (Bq/m 3 ) by time spent, and the right dose coefficient. As a result the following equations are used to calculate the annual effective dose Effective dose = Radon level X Time X Dose coefficient (2) Where; Radon level : is the radon concentration in Bq/Kg Time : is the time spent for exposure in hour Dose coefficient: is the conversion factor to dose from radon concentration mSv/Bqhm -3 ii) Radiometric measurements γ-ray spectrometer is NaI(Tl) The system of gamma ray spectrometer consists of Bicron scintillation detector, NaI(Tl) crystal, 76x76 mm, hermetically sealed with a photomultiplier tube in aluminum housing. 2-For estimating the annual effective dose equivalent AEDE (mSv/y) from dose rate, two main factors must be introduced i) a conversion coefficient from absorbed dose in air to effective does must take in account with a value of 0.7 Sv /Gy. ii) Outdoor occupancy factor reports a value of a conversion coefficient factor from absorbed dose in air to effective dose received by adults, and 0.2 for the outdoor occupancy factor and 0.8 for indoor occupancy factor [9,10] Then AEDE (mSv/y) can be written as: AEDE (mSv/ y) = D (n Gy h -1 ) x 8760(h/y) x 0.2 x 0.7 Sv Gy -1 x 10 -6 (4) The world average annual effective dose equivalent (AEDE) from outdoor terrestrial gamma radiation is 70 µSv/h [11] The International Commission of Radiological Protection (ICRP) recommended that no individual should receive more than 50 mSv/y from all natural and artificial radiation sources in his/her environment [12]. The recent recommendations of IAEA indicate that the permissible levels of dose rates reaching up to 5 mSv/y for public members and up to 20 mSv/y for the occupational members [9,13] 3-Radiation indices factors, it gives a complete measure about how the radiation is affecting on human body.
-Radium equivalent is the factor introduced to establish a state of uniformity distributions of the three main radioactive nuclei as the distribution of 226 Ra , 232 Th and 40 K in soil is not uniform [14].
Ra eq = A Ra + ( A Th X 1.43) +( A K X 0.077) The recommended maximum value of Ra eq is 370 Bq/kg [15].
-External hazard index (H ex ), measures the external hazard due to the emitted gamma radiation. It was calculated by the equation [16].
For the safe limits, (H ex ) should be less than unity -Internal hazard index (H in ), the internal hazard index which controls the internal exposure to 222 Rn and its radioactive progeny and is given by [17].
For the safe limits, (H in ) should be less than unity -Radioactivity level index (I γ ), estimates the level of radiation risk, especially γ -rays, associated with natural radio nuclides in specific materials [18,19].
Where, A Ra , A Th and A K are the Activity concentrations of 226 Ra, 232 Th and 40 K in Bq/kg respectively. The safety value for this index is ≤ 1.

5-Excess Lifetime Cancer Risk (ELCR)
Gives the probability of developing cancer over a lifetime at a given exposure level, considering 70 years as the average duration of life for human being. It is given [20].
Where AEDE is the Annual Effective Dose Equivalent, DL is the average Duration of Life (estimated to be 70 years) and RF is the Risk Factor (Sv) i.e. fatal cancer risk per Sievert. For stochastic effects, ICRP uses RF as 0.05 for the public. The percentage risk analysis associated with this index is then given [21].

6-Annual dose limits for human tissues
The effective dose is considered for the whole body while applying a tissue weighting factor (W T ) of 1, for calculating the dose for any specific tissue inside the body it's said to be fraction of 1, different tissues are affected differently so the tissue weighting factors are nor equal and are divided to three categories. Low risk (0.01), medium risk (0.05) and high risk (0.12) [22].

Results and Discussion
Two locations were chosen to be studied where urban people live there and the other where they graze their animals. Heboush and Ramlet Homayier areas are the two locations where they live and graze their animals respectively. They are covered mainly by sand.

Heboush area
A systematic ground spectrometric survey has been taken on a grid pattern that consists of a set thirty six stations were measured radio-metrically in Heboush area forming a network of four lines; each line contains 9 stations figure (2) and (3), table (1) shows the minimum, maximum and average data. According to the γ-ray spectrometric survey, Heboush area show low eU-content ranging from 0.7 ppm to 4.4 ppm this may be attributed to that Heboush area was covered by a very thick layer of barren sand. The eU/eTh ratio is a very important index for determining uranium migration in or out. The Clark value for eU/eTh in the sedimentary rocks is equal to unity [23]. The average eU/eTh ratio of the most measured stations is 2.47.

Ramlet Homayier area
It is surveyed to search for the extension of radioactive anomalies in the area and it serves as a good location for breeding animals for the local citizens living there as they camp in the area during spring time, so an environmental investigation is also important to be done. The area was covered by a very thin layer of sand in which you can reach to the lower member of Um Bogma Formation after a few centimeters.
A systematic ground spectrometric survey has been taken on a grid pattern that consists of a set of parallel profiles trending nearly in the NW-SE. Fifty six stations were measured radio-metrically in Ramlet Homayier area forming a network of four lines; each line contains 14 stations figure (4), table (1) shows the minimum, maximum and average data. According to the γ-ray spectrometric survey many radioactive anomalies were recorded within the ferruginous siltstone of the lower Um Bogma Formation table (1) reaches more than 2300 ppm eU-content. The average eU/eTh ratio of the area is 12.99 indicating an addition of uranium (migration in).

Radon concentrations and Annual effective dose calculations
The results shown in table (3) for the track density and radon gas concentrations (Bq/Kg) are calculated from equation (1), the indoor and outdoor annual effective doses (mSv) are calculated using equation (2) for the average result of all selected stations of both locations. ) respectively which is higher than the world limit of (100 Bq/m 3 ) in both locations [24]. For the indoor annual effective dose in Ramlet Homayier and Heboush area ranged between (7.33 to 794.93 mSv) and (6.10 to 114.07 mSv) respectively with an average of (48.71 mSv) and (19.70 mSv) respectively which is higher than the average world limit of (3 -10 mSv) for both locations [13]. On the other hand the outdoor annual effective dose in Ramlet Homayier and Heboush area ranged between (3.72 to 403.23 mSv) and (3.09 to 57.86 mSv) respectively with an average of (24.71 mSv) and (10.0 mSv) respectively which is higher than the average world limit of (3 -10 mSv) for Ramlet homayier and a border limit of Heboush area [13]. The results show that Ramlet Homayier area is having high background radioactivity due to the high subsurface abundance of NORM in that area, figure (5) and (6).  H1  H2  H3  H4  H5  H6  H7  H8  H9  H10  H11  H12  H13  H14  H15  H16  H17  H18  H19  H20  H21  H22  H23  H24  H25  H26  H27  H28  H29  H30  H31  H32  H33  H34  H35

Radiometric measurements, Annual effective doses, Hazard indices and ELCR Calculations
The results shown in table (4) for the specific activity for U, Th, Ra and K in (Bq/Kg), the dose rate DR in (nGy/h) calculated using equation (3), the indoor and outdoor annual effective doses in (mSv) calculated from equation (4), the radium equivalent in (Bq/Kg) calculated from equation (5), the internal, external and gamma indices calculated from equations (6, 7 and 8) respectively and finally the excess lifetime cancer risk calculated from equation (9); for the average result of all selected stations of both locations. The uranium specific activity shown in table (4) in Ramlet Homayier and Heboush area ranged between (7.41 to 24625.9 Bq/Kg) and (8.65 to 54.34 Bq/Kg ) respectively with an average of (877.25 and 26.48 Bq/Kg) respectively which is higher than the world average level of (50 Bq/Kg) for Ramlit Homayier area [10].
The thorium specific activity in Ramlet Homayier and Heboush area ranged between (0.41 to 483.95 Bq/Kg) and (0.41 to 24.36 Bq/Kg) respectively with an average of (44.89 and 11.63 Bq/Kg) respectively which is higher than the world average level of (40 Bq/Kg) in Ramlet Homayier area [10].
The radium specific activity in Ramlet Homayier and Heboush area ranged between (11.06 to 5906.04 Bq/Kg) and (11.06 to 88.48 Bq/Kg) respectively with an average of (758.20 and 17.51 Bq/Kg) respectively which is higher than the world average level of (40 Bq/Kg) in Ramlet Homayier area [10].
Finally the potassium specific activity in Ramlet Homayier and Heboush area ranged between (31.3 to 5759.2 Bq/Kg) and (31.3 to 125.2 Bq/Kg) respectively with an average of (219.66 and 43.47 Bq/Kg) respectively which is lower than the world average level of (500 Bq/Kg) for both locations [10]. This shows a higher level of surface radioactivity in Ramlet Homayier than Heboush area due to higher abundance of NORM.
The Dose rates shown in table (5 and 6) in Ramlet Homayier and Heboush area ranged between (6.66 to 3261.06 nGy/h) and (6.66 to 46.35 nGy/h) respectively with an average of (386.56 and 16.93 nGy/h) respectively which is higher than the average world limit of (70 nGy/h) in Ramlet Homayier area [25].
The indoor AED in Ramlet Homayier and Heboush area ranged between (0.03 to 16.06 mSv) and (0.03 to 0.23 mSv) respectively with an average of (1.90 and 0.08 mSv) respectively which is higher than the average world limit of (0.5 mSv) in Ramlet Homayier area [11] This can result in health hazard effects due to exposures to such doses that arise from surface abundance of NORM in Ramlet Homayier area, figure (7) and (8).
The outdoor AED in Ramlet Homayier and Heboush area ranged between (0.01 to 4.0 mSv) and (0.01 to 0.06 mSv) with an average of (0.47 and 0.02 mSv) respectively which is lower than the average world limit of (0.5 mSv) for both locations [11]. This can result in negligible effect of health hazard due to exposures to such doses that arise from surface abundance of NORM, figure (7) and (8).
The radium equivalent in Ramlet Homayier and Heboush area ranged between (14.05 to 7041.55 Bq/Kg) and (14.05 to 100.76 Bq/Kg) with an average of (839.31 and 37.49 Bq/Kg) respectively which is higher than the average world limit of (370 Bq/Kg) for Ramlet Homayier area [16]. This gives a sign of not using rocks from Ramlet Homayier area as a building material.   19.03) and (0.04 to 0.27) with an average of (2.27 and 0.10) respectively which is higher than unity (1) for Ramlet Homayier area [26].

Hazard indices and ELCR calculations
The internal hazard index in Ramlet Homayier and Heboush area ranged between (0.13 to 34.99) and (0.07 to 0.51) with an average of (3.94 and 0.15) respectively which is which is higher than unity (1) for Ramlet Homayier area [26]. The gamma index in Ramlet Homayier and Heboush area ranged between (0.1 to 48.05) and (0.1 to 0.68) with an average of (5.65 and 0.26) respectively which is higher than the world average of (≤ 1) for Ramlet Homayier area [25].
The excess life time cancer risk in Ramlet Homayier and Heboush area ranged between (0.000029 to 0.013998) and (0.000029 to 0.000199) with an average of (0.001659 and 0.000073) respectively which is higher than the standard probability of (0.00029) for Ramlet Homayier area [22], this reveals the inadequacy of Ramlet Homayier area as a public residence area.

Annual effective dose delivered to each body tissue
The annual effective dose for each tissue is calculated from outdoor AED in Ramlit Homayier for both radon concentration from closed cup technique and radiometric measurements and indoor AED Heboush area for both radon concentration from closed cup technique and radiometric measurements and compared to the world maximum tissue dose limit for public and occupation using the tissue weighing factor for the all the tissues. The listed results from table (6) reveals a high dose risk to public derived from the exposure to subsurface NORM in Ramlet Homayier more than Heboush area for most body tissues especially in closed areas when there will be poor or insufficient ventilation and is delivered most to gonads and abdominal organs (digestive, respiratory and reproductive systems) for being there in the two locations around the 24 hours either in staying in homes or doing grazing activities. However if compared to the occupational limits it shows lower risk; on the other hand a low dose risk arise from the surface exposure to NORM in both locations. Finally applying the same daily habits requires the implementation of radiation protection principals and considering workers in Ramlet Homayier area occupational workers.
Finally, the great difference between dose delivered by NORM (surface) and cup technique (subsurface) may be attributed to, the mechanism of measurements, where in (surface) depends mainly upon γ-ray emitted from long lived nuclei, while in case of (subsurface) cup techniques it depends on the α-particles with specific energy emitted from 238 U as a parent nuclei for 226 Ra and 222 Rn.

Conclusions
According to the γ-ray spectrometric survey, Heboush area show low eU-content ranging from 0.7 ppm to 4.4 ppm this may be attributed to that Heboush area was covered by a very thick layer of barren sand. The average eU/eTh ratio of the most measured stations is 2.47 indicating the addition of uranium (migration in). While Ramlet Homayier area was covered by a very thin layer of sand in which you can reach to the lower member of Um Bogma Formation after a few centimeters. Ramlet Homayier area reaches more than 2300 ppm eU-content. The average eU/eTh ratio of the area is 12.99 indicating an addition of uranium (migration in).
This research work provides baseline data for NORM concentration in Ramlet Homayier and Heboush areas located in south western Sinai, the specific activity concentrations of 238 U, 232 Th, 226 Ra and 40 K with the radon gas concentrations gives a complete view of the radiological health hazards that public citizens are subjected to due to their daily activities either indoor or outdoor and whether its external or internal exposures. It is recommended according to this paper that staying in such levels of NORM requires a high caution and awareness to minimize the health risk accompanied to daily exposure of public and applying radiation protection principals to achieve a better safe working and living environment.
The results obtained from this research is useful for establishing a data baseline of background radiation levels in the selected area, and represent a basis to assess any further changes in the radioactivity background levels due to various geological processes or any artificial influences around the area under considerations.
The Authors declare that there is no conflict of interest.