Journal of Environmental Radioactivity 83 (2005) 91e99

www.elsevier.com/locate/jenvrad

Measurement of natural radioactivityin building materials in Qena

city, Upper Egypt

Nour Khalifa Ahmed

Physics Department, Faculty of Science, South Valley University, Qena, Egypt

Received 1 November 2004; received in revised form 9 February 2005; accepted 4 March 2005

Available online 28 April 2005

Abstract

Building materials cause direct radiation exposure because of their radium, thorium andpotassium content. In this paper, samples of commonly used building materials (bricks,

cement, gypsum, ceramics, marble, limestone and granite) in Qena city, Upper Egypt havebeen collected randomly over the city. The samples were tested for their radioactivity contentsby using gamma spectroscopic measurements. The results show that the highest mean value of226Ra activity is 205G 83 Bq kg�1 measured in marble. The corresponding value of 232Th is

118G 14 Bq kg�1 measured in granite. For 40K this value is (8.7G 3.9)! 102 Bq kg�1

measured in marble. The average concentrations of the three radionuclides in the differentbuilding materials are 116G 54, 64G 34 and (4.8G 2.2)! 102 Bq kg�1 for 226Ra, 232Th and40K, respectively. Radium equivalent activities and various hazard indices were also calculatedto assess the radiation hazard. The maximum mean of radium equivalent activity Raeq is436G 199 Bq kg�1 calculated in marble. The highest radioactivity level and dose rate in air

from these materials were calculated in marble.� 2005 Elsevier Ltd. All rights reserved.

Keywords: Radioactivity; Building materials; Environmental; Spectroscopy

E-mail address: nour_khalifa2000@yahoo.com

0265-931X/$ - see front matter � 2005 Elsevier Ltd. All rights reserved.

doi:10.1016/j.jenvrad.2005.03.002

92 N.K. Ahmed / J. Environ. Radioactivity 83 (2005) 91e99

1. Introduction

Studies of natural radiation background are of great importance because it is themain source of exposure of human kind. Building materials is one of the sourceswhich cause direct radiation exposure, for this there are many papers which reportthe natural radionuclide content of building materials over the world (Ali et al.,1996; Tufail et al., 1992, 1994; Chen et al., 1993; Khan et al., 1992). The content of226Ra, 232Th and 40K in these materials is of major interest with regard to theradioactivity indoors. Brick, cement, gypsum and granite stone may producesignificant external dose rates in the range of nGy h�1 (Louizi and Proukakis, 1994).In addition to the materials used for the structure of a building, materials used forthe decoration of the rooms have also to be considered as possible sources forradioactivity indoors, e.g. ceramics, tiles for floors and walls. These materials cancontain uranium salts for coloring purposes. Measurement of natural radioactivitydue to gamma rays from these materials, and consequently the determination of thedose rate, helps firstly to implement precautionary measures whenever the dose isfound to be above the recommended limits. Secondly, knowledge of gammaradioactivity is required by the building construction association to adopt preventivemeasures to tone down the harmful effects of ionizing radiation.

The aim of this paper is to measure gamma activity due to 226Ra, 232Th and 40K aswell as the dose rate from some used building materials in Qena city, and to continuethe program of measuring natural radioactivity in different environmental media inUpper Egypt started in physics department, Faculty of Science at Qena since 1990.

2. Experimental procedure

For radioactivity measurement samples of commonly used building materials,bricks, cement, gypsum, lime, marble and granite stone, in Qena city have beencollected randomly over the city and tested for their natural radioactivity content.Ten to fifteen samples from each kind of building material were crushed and dried at105 �C in an oven and then ground and sieved to less than 90 mm particle size. Thesamples were hermetically sealed in cylindrical plastic boxes 13 mm height and55 mm diameter. The samples were closed tightly to limit as far as possible escape ofradon. Each box was analyzed after secular equilibrium of 226Ra and 232Th withtheir decay products was obtained using HP Ge detector setup and 8192 channelMCA.

Activity concentrations were averaged from photopeaks at several energies. For226Ra, the 351.9 and 609.3 keV gamma lines of 214Bi and 214Pb, respectively, wereused. For confirmation, the other lines (1120, 1764 and 2204 keV) were alsomonitored. For 232Th, the gamma lines of 228Ac and 208T1 at 911.1 and 583.01 keV,respectively, were averaged. 40K is measured directly through its gamma photopeakat 1460.7 keV. Methods of adjustment, calibration and calculations have beendescribed in detail in earlier publications (Salahel-din, 2003; Abbady, 2002).

93N.K. Ahmed / J. Environ. Radioactivity 83 (2005) 91e99

3. Results and discussion

3.1. Activity concentration

226Ra, 232Th and 40K contents of building material are determined by the origin ofthe raw materials used for private and public buildings. From the results it can be seenthat the lowestmean value of 226Ra concentration is 33G 20 Bq kg�1measured in claybrick, while the highest mean value for the same radionuclide is 205G 83 Bq kg�1

measured in marble. 232Th lowest mean value is 14G 10 Bq kg�1 recorded in mudbrick and the highest mean value is 118G 14 Bq kg�1 measured in granite. Thecorresponding values of 40K are (2.5G 0.5)! 102 and (8.7G 3.9)! 102 Bq kg�1

measured in white cement and marble, respectively. These results are given in Table 1.The average concentration of the three radionuclides in the different building

materials are 116G 54, 64G 34 and (4.8G 2.2)! 102 Bq kg�1 for 226Ra, 232Th and40K, respectively. Fig. 1 is the means of the three radionuclides in all samples underinvestigation.

Radium, thorium and potassium are not uniformly distributed in soil or rocks,from which building materials are derived, but the radioactivity varies, often greatly,over a distance of some meters (Slunga, 1988). The measured values of radium andthorium contents of soil therefore show only the average radioactivity of an area. Onthe basis of the half lives of radium and thorium the radon and thoron production,and hence their gamma emitting daughters, in building materials during the life timeof a building may be considered to be constant.

3.2. Radium equivalent activity (Raeq)

As mentioned before and consequently, the distribution of 226Ra, 232Th and 40Kin building materials is not uniform. Uniformity in respect of exposure to radiationhas been defined in terms of radium equivalent activity (Raeq) in Bq kg�1 to compare

Table 1

Summary results of the mean activity concentration of these radionuclides in some used raw building

materials in Qena city

Type of building

material

Radionuclides concentration (Bq kg�1)

Ra-226 Th-232 K-40

Range Mean Range Mean Range Mean

Gypsum 10e170 105G 6 3e70 45G 15 300e700 500G 141

Lime brick 60e180 132G 47 10e90 45G 29 60e800 306G 148

White cement 30e130 72G 33 20e80 46G 21 200e300 250G 50

Portland cement 20e120 134G 67 10e170 88G 35 20e700 416G 162

Granite 80e330 187G 90 100e140 118G 14 250e1300 852G 297

Marble 110e340 205G 83 50e210 115G 60 300e1500 865G 392

Mud brick 24e100 53G 18 3e45 14G 10 2e1300 325G 202

Clay brick 12e60 33G 20 8e73 37G 17 160e773 511G 158

Ceramics 40e230 126G 54 10e130 72G 39 80e600 300G 102

94 N.K. Ahmed / J. Environ. Radioactivity 83 (2005) 91e99

the specific activity of materials containing different amounts of 226Ra, 232Th and40K. It is calculated through the following relation (Beretka and Mathew, 1985):

RaeqZðCTh!1:43ÞCCRaCðCK!0:077Þ ð1Þ

where CTh is the 232Th activity concentration (Bq kg�1), CRa is the 226Ra activityconcentration (Bq kg�1) and CK is the 40K activity concentration (Bqkg�1).

It is assumed that 370 Bq kg�1 of 226Ra, 259 Bq kg�1 of 232Th and 4810 Bq kg�1

of 40K produce the same gamma ray dose rate (Stranden, 1976; Krisiuk et al., 1971).A radium equivalent of 370 Bq kg�1 in building materials will produce an exposureof about 1.5 mSv y�1 to the inhabitants (UNSCEAR, 1982). Fig. 2 shows the Raeqresults in all samples under test in increasing order of magnitude. From the results itcan be noticed that the lowest value of Raeq is 98G 48 Bq kg�1 calculated in mudbrick, while the highest value is 436G 199 Bq kg�1 calculated in marble. The highRaeq values calculated in granite and marble can be rendered to the highconcentration of the three radionuclides 226Ra, 232Th and 40K in these materials asshown in Table 1. From the results it is evident that there are considerable variationsin the Raeq of the different materials and also within the same type of materialoriginating from different areas. This fact is important from the point of view ofselecting suitable materials for use in building and construction especially concerningthose which have large variations in their activities. Large variation in radiumequivalent activities may suggest that it is advisable to monitor the radioactivitylevels of materials from a new source before adopting it for use as a building material(Kumar et al., 1999). The recommended maximum levels of radium equivalents forbuilding materials to be used for homes is !370 Bq kg�1 and for industries is 370e740 Bq kg�1 (Oresegun and Babalola, 1988).

0

100

200

300

400

500

600

700

800

900

1000

Gypsum Lime brick White cement Portlandcement

Granite Marble Mud brick Clay brick Ceramics

Ac

tiv

ity

c

on

ce

ntra

tio

n (B

q/k

g)

Ra-226Th-232K-40

Fig. 1. Mean activity concentration (Bq kg�1) of 226Ra, 232Th and 40K in some building materials.

95N.K. Ahmed / J. Environ. Radioactivity 83 (2005) 91e99

Many studies have been concerned with the distribution of 236Ra and 232Th inigneous rocks (Hussein, 1998; El-Arabi, 1991). All studies are in agreement inshowing that both 236Ra and 232Th increase in abundance toward later crystallizingand more acidic rock types which is in a reasonable accord with the present study.

From another point of view, distribution of radon output is also largelydependent upon the building material used for the inner walls. Measurements onbuilding materials in England (Kliff, 1978) showed that the highest radon outputswere found in those properties having inner walls of granite and plaster. Table 2shows the mean values for 226Ra, 232Th, 40K and radium equivalent activity (Raeq)for all building materials under investigation beside other countries. Table 3 showsthe radioactivity level in the different types of building materials under investigationin increasing order.

Granite and marble activities would suggest that the use of such kind of buildingmaterials in the construction of domestic dwellings or workplaces is unlikely to giverise to any significant radiation exposure to the occupants. Accordingly, cautionmust be taken when using granite and marble as building materials because theyhave radioactivity above the proposed acceptable level (Ruixiang, 1986).

3.3. The dose rate in air from building materials

There is concern that some of the buildings will cause excessive radiation doses tothe total body due to gamma rays emitted by the 214Pb and 214Bi progeny of 226Ra.232Th decay chain and 40K also contribute to the total body radiation dose. The total

0

50

100

150

200

250

300

350

400

450

500

Mud brick Clay brick White cement Gypsum Lime brick Ceramics Portlandcement

Granite Marble

Rad

iu

m eq

uivalen

t a

ctiv

ity

(B

q/k

g)

Fig. 2. Radium equivalent activity (Bq kg�1) for some used building materials in increasing order of

magnitude.

96 N.K. Ahmed / J. Environ. Radioactivity 83 (2005) 91e99

air absorbed dose rate (nGy h�1) due to the mean specific activity concentrations of238U, 232Th and 40K (Bq kg�1) was calculated using the formula of Beck et al.(UNSCEAR, 1988; Beck et al., 1972).

DZ0:427CUC0:662CThC0:0432CK ð2Þ

where CU is the mean activity concentration of 238U, CTh is the mean activityconcentration of 232Th and CK is the mean activity concentration of 40K in samples.This equation is used for calculating the absorbed dose rate in air at a height of 1.0 mabove the ground from measured radionuclide concentration in environmentalmaterials. Table 3 summarizes the results of the dose rates in air from some usedbuilding materials. From the results it can be noticed that marble and granite containhigher 226Ra, 232Th and 40K than other investigated types, and consequently theyproduce higher dose rates in air, a result which is in a reasonable accord with otherpublished data (Hussein, 1998; El-Arabi, 1991).

Table 3

Radioactivity level and dose rate in some used building materials

Type of building material Radioactivity level Dose rate (nGy h�1)

Mud brick 0.26G 0.13 45.7G 7

Clay brick 0.34G 0.15 60.3G 8

White cement 0.42G 0.18 72.0G 8.5

Gypsum 0.56G 0.10 96G 10

Lime brick 0.59G 0.30 99.5G 10

Ceramics 0.68G 0.32 114.6G 11

Portland cement 0.79G 0.35 133.6G 12

Granite 1.14G 0.36 194.6G 14

Marble 1.18G 0.54 200.9G 14

Table 2

Mean values for 226Ra, 232Th, 40K and Raeq activity for all building materials under investigation beside

other countries

Country Concentration (Bq kg�1) Raeq(Bq kg�1)

References

226Ra 232Th 40K

Range Mean Range Mean Range Mean

Ireland !1e140 32 !1e57 18 4e1977 353 e Lee et al. (2004)

South Korea 6.5e271 e N.D.e89.9 e 16.8e1081 e e Lee et al. (2001)

Algerian 12e65 e 7e51 e 36e675 e !370 Amrani and

Tahtat (2001)

Sri Lankan e 35 e 72 e 585 183 Hewamanna

et al. (2001)

Pakistan

(Brick)

36.9e52 52.5e68 680e784 !370 Khan et al.

(2002)

Southwestern

Nigeria

(Concrete blocks)

4.3e66.8 15.7 12.4e266.5 36 86.2e1073 253 100.5 Farai and

Ademola (2005)

Present work 10e340 116 3e210 64 2e1500 480 246

97N.K. Ahmed / J. Environ. Radioactivity 83 (2005) 91e99

3.4. External hazard index

According to ICRP (1977) the upper limit of radiation dose arising from buildingmaterials is 1.5 mSv y�1. For limiting the radiation dose to this value, Krieger (1981)proposed the following conservative model based on infinitely thick walls withoutwindows and doors to serve as a criterion for the calculation of external hazard indexHex e defined as:

HexZCRa

370C

CTh

259C

CK

4810ð3Þ

where CRa, CTh and CK are the activity concentrations of 226Ra, 232Th and 40K,respectively, in Bq kg�1 for the material. Hewamanna et al. (2001) corrected thismodel after considering a finite thickness of walls and the existence of windows anddoors. Taking these considerations into account, the equation used for thecalculation of external hazard index becomes:

HexZCRa

740C

CTh

520C

CK

9620ð4Þ

The value of this index must be less than unity for the radiation hazard to benegligible, i.e. the radiation exposure due to radioactivity in construction materialsmust be limited to 1.5 mSv y�1. The obtained values of Hex are shown in Fig. 3.

3.5. Internal hazard index

In addition to the external irradiation, radon and its short-lived products are alsohazardous to the respiratory organs. The internal exposure to radon and its daughterproducts is quantified by the internal hazard index (Hin) which is given by thefollowing equation (Krieger, 1981).

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

Gypsum Lime brick White cement Portlandcement

Granite Marble Mud brick Clay brick Ceramics

Hazard

in

dex

HEXHIN

Fig. 3. External and internal hazard index in some used building materials.

98 N.K. Ahmed / J. Environ. Radioactivity 83 (2005) 91e99

HinZCRa

185C

CTh

259C

CK

4810ð5Þ

where CRa, CTh and CK are the activity concentrations of 226Ra, 232Th and 40K,respectively, in Bq kg�1 for the material. For the safe use of a material in theconstruction of dwellingsHin should be less than unity. The values ofHin for samplesunder investigation are shown in Fig. 3. From which we can see that granite andmarble have Hex and Hin values above unity. So, caution must be taken when usinggranite and marble as building materials.

4. Conclusion

Measurements of natural radioactivity in some used building materials in Qenacity led to the following conclusions:

1. The maximum value of the mean activity concentration of the three radio-nuclides 226Ra, 232Th and 40K are 205G 83, 118G 14 and (8.7G 3.9)!102 Bq kg�1 measured in marble, granite and marble, respectively. The minimumvalues are 33G 20, 14G 10 and 250G 50 Bq kg�1 measured in clay brick, mudbrick and white cement, respectively. The mean values in all samples underinvestigation are 116G 54, 64G 34 and (4.8G 2.2)! 102 Bq kg�1 for the threeradionuclides, respectively.

2. Maximum and minimum radium equivalent activity values are 431G 199 and98G 48 Bq kg�1calculated in marble and mud brick, respectively.

3. Maximum and minimum values of the dose rate in air are 201G 14 and 46G 7,while the maximum and minimum values for the radioactivity level are 1.2G 0.5and 0.26G 0.13 calculated in marble and mud brick, respectively.

4. Values of external hazard index for all samples under investigation are below theunity, while the internal hazard index for marble, granite, Portland cement andceramic exhibit values above the unity.

5. All samples under investigation are within the recommended safety limit whenused as building construction except marble and granite which have values abovethe recommended limit for homes.

References

Abbady, A.G.E., 2002. Natural radioactivity of rocks and building materials and its relevance for the

radiation exposure due to radon. Ph.D. thesis, Physics Department, Qena, South Valley University,

Egypt.

Ali, S., Tufail, M., Jamil, K., Ahmad, A., Klian, H.A., 1996. Gamma-ray activity and dose rate of brick

samples from some areas of North West Frontier Province (NWFP), Pakistan. Sci. Total Environ. 187

(3), 247e252.Amrani, D., Tahtat, M., 2001. Natural radioactivity in Algerian building materials. Appl. Radiat. Isot. 54

(4), 687e689.

Beck, H.L., Decompo, J., Gologak, J., 1972. In Situ Ge (Li) and NaI (Tl) gamma ray spectrometry. Health

and Safety Laboratory, AEC, New York, p. 258, Report HASL.

99N.K. Ahmed / J. Environ. Radioactivity 83 (2005) 91e99

Beretka, J., Mathew, P.J., 1985. Natural radioactivity of Australian building materials, industrial wastes

and by-products. Health Phys. 48, 87e95.

Chen, C.J., Weng, P.S., Chu, T.C., 1993. Radon exhalation rate from various building materials. Health

Phys. 64 (6), 613e619.

El-Arabi, A.M., 1991. Natural radioactivity of some locally rocks and soils in Wadi Qena. M.Sc. thesis,

Physics Department, Faculty of Science Qena, Assiut University, Assiut, Egypt.

Farai, I.P., Ademola, J.A., 2005. Radium equivalent activity concentrations in concrete building blocks in

eight cities in Southwestern Nigeria. J. Environ. Radioact. 79, 119e125.

Hewamanna, R., Sumithrachchi, C.S., Mahawatte, P., Nanayakkara, H.L.C., Ratnayake, H.C., 2001.

Natural radioactivity and gamma dose from Sri Lankan clay bricks used in building construction.

Appl. Radiat. Isot. 54 (2), 365e369.Hussein, M.A., 1998. Gamma spectroscopic measurements on powdered granite samples from Aswan area

and Wadi Allaqi. M.Sc. thesis, Physics Department, Faculty of Science Aswan, South Valley

University, Egypt.

ICRP, 1977. International Commission on Radiological Protection. Recommendations of ICRP.

Publication 26. Pergamon Press, Oxford.

Khan, A.J., Prasad, R., Tyagl, R.K., 1992. Measurement of radon exhalation rate from some building

materials. Nucl. Tracks Radiat. Meas. 20 (4), 609e610.Khan, K., Aslam, M., Orfi, S.D., Khan, H.M., 2002. Norm and associated radiation hazards in bricks

fabricated in various localities of the North-West Frontier Province (Pakistan). J. Environ. Radioact.

58 (1), 59e66.

Kliff, K.D., 1978. Assessment of Airborne radon daughter concentrations in dwellings in Great Britain.

Phys. Med. Biol. 23 (4), 696e711.

Krieger, R., 1981. Radioactivity of construction materials. BetonwerkCFertigteil-Techn. 47, 468e473.

Krisiuk, E.M., Tarasov, S.I., Shamov, V.P., Shalak, N.I., Lysachenko, E.P., Gomelsky, L.G., 1971. A

study of radioactivity in building material. Leningrad Research Institute for Radiation Hygiene,

Leningrad.

Kumar, V., Ramachandran, T.V., Prasad, R., 1999. Natural radioactivity of Indian building materials and

by-products. Appl. Radiat. Isot. 51, 93e96.Lee, E.M., Menezes, G., Finch, E.C., 2004. Natural radioactivity in building materials in the Republic of

Ireland. Health Phys. 86 (4), 378e383.

Lee, S.C., Kim, C.K., Lee, D.M., Kang, H.D., 2001. Natural radionuclides contents and radon exhalation

rates in building materials used in South Korea. Radiat. Prot. Dosim. 94 (3), 269e274.Louizi, A., Proukakis, C., 1994. Measurements of natural radioactivity in Greek building materials.1st

Mediterranean Congress on Radiation Protection, Athens, April 5e7.

Oresegun, M.O., Babalola, A.I., 1988. Annual indoor dose burden estimates in dwellings built in Nigeria

with radioactive U-Th rich tailings. In: Proceedings of an international Conference on Radiation

Protection in Nuclear Energy, vol. 2, 18e22 April, IAEA, Vienna, Austria, pp. 159e166.

Ruixiang, Li, 1986. An approach to the exposure limit from natural radioactivity in building materials.

Atom. Energy Sci. Technol. 20 (5), 596e601.Salahel-din, K., 2003. Natural radioactivity of some iron ores in Upper Egypt and their dose rates. M.Sc

thesis, Physics Department, Qena, South Valley University, Egypt.

Slunga, E., 1988. Radon classification of building ground. Radiat. Prot. Dosim. 24 (114), 39e42.

Stranden, E., 1976. Some aspects on radioactivity of building materials. Health Phys. 8, 167e177.Tufail, M., Ahmad, N., Al.makky, S., Zafar, M.S., Khan, H.A., 1992. Natural radioactivity in the

ceramics used in dwelling as construction material. Sci. Total Environ. 127 (3), 243e253.

Tufail, M., Rashid, T., Mahmood, A.B., Alunad, N., 1994. Radiation doses in Pakistani houses. Sci. Total

Environ. 42 (3), 171e177.UNSCEAR, 1982. Ionizing radiation sources and biological effects. United Nations Scientific Committee

on the Effects of Atomic Radiation 1982. Report to General Assembly, With Annexes. United

Nations, New York.

UNSCEAR, 1988. Sources, effects and risks of ionizing radiation, United Nations Scientific Committee on

the Effects of Atomic Radiation, Annex A, B. United Nations, New York.