- Email: [email protected]
Radon activity in Saudi houses
Nuclear Tracks and Radiation Measurements, Vol. 8, Nos. I-,:1, pp. 395-398, 1984. Printed in Great Britain.
,
0191 278X/84 $3.00 + .00 1984 Pergamon Press Ltd.
RADON ACTIVITY IN SAUDI HOUSES F. Abu-Jarad & M.I. AI-Jarallah Department of Physics University of Petroleum & Minerals Dhahran, Saudi Arabia
ABSTRACT Long term measurements of radon's concentrations inside Saudi Houses being studied using CR-39 Plastic Track Detectors fixed inside sealed plastic cups. The cups were left for about 7 months in the houses. The measurements were done in different cities of different provinces in the country. The analysis of 636 cups showed that the radon concentration in different cities was ranging from 0.27 pCi/l (in Khobar) to 0.98 pCi/l (in Taif). In exceptional places in Eastern Province, it is found that the lowest concentration was in the University offices (0.13 pCi/l) and the highest was in the University unoccupied houses (0.81 pCi/l). It is found that the ventilation is the main factor affecting the radon concentration in houses.
KEYWORDS
Radon concentration,
Saudi Arabia, CR-39 Track Detectors,ventilation.
INTRODUCTION
The estimation of long exposure of populations to low levels of radon and its decay products in dwelling is a general problem. Thus recently several surveys for measuring the concentration of radon and its products have been done. Some of these surveys measured the integrated value of radon over long periods of times using passive track detectors (Frank & Benton 1977, Alter & Fleisher 1981, Miles 1981, Urban & Piesch 1981 Abu-Jarad 1980, 1984). The long-time-integrated measurements should give better estimations of population dose than short-time ones, since they give long-term average exposures in the conditions in which the inhabitants of the house live their normal lives. This is the first survey which was done in Saudi Arabia. Most of the surveys reported uptil now were carried out in cold countries like Europe, Canada and USA. Therefore this survey may be of some interest as it was carried out in a hot country.
The majority of the houses are constructed of concrete and blocks (crushed stones + sand + cement). The country is generally very hot in summer season which extends for most of the year. Most of the buildings which were monitored were airconditioned. In winter the weather is quite cold particularly in Central and Eastern Provinces, while it is mild in the Western province. The humidity levels are high in both Western and Eastern provinces because they are located along the Red Sea and the Arabian Gulf respectively while the levels are low in the Central province. "Taif" city is an exceptional case because it lies on top of mountains 1200 ft above sea level, and is cold in winter and mild in summer.
METHOD In this survey a plastic cup was used as a holder for a CR-39 Plastic Track Detector 395
396
F. ABU J A R A D and M. 1. A L - J A R A L L A H
(Pershore Molding Ltd.) which is fixed inside the bottom of the cup (Fig.l). A hole was made in the cover of the cup which was then sealed from inside with foam. This was done to stop the aerosole and daughter's particles from entering the cup while allowing the radon gas among other air consistuents to pass through. In the decay of radon-222 to its short lived daughters (Z18Po, 214Pb, 21~Bi, 214Po), three alpha particles will be emitted in this series from Rn, 218Po and 214Po (5.49, 6.00 and 7.68 MeV respectively). Some of these m-particles will hit the plastic if it falls within their ranges. Therefore the CR-39 detector will accumulate by time number of tracks proportional to the concentration of radon gas in the room.
Two to three cups were placed in each house in different rooms for a perlod of about 7 months. In total 1200 cups were distributed throughout the main cities in the country. Out of these 636 detectors were analyzed and the remaining are yet to be analyzed. The results of these analyses are presented here. The etching conditions are 70°C, 30% KOH, 9 hour and the solution was continuously stirred. The system was calibrated in the National Radiological Protection Board (NRPB) in Harwell, U.K.
RESULTS Table 1 gives results of all the analyzed samples from different provinces. The following observations can be made from the table. It is clear from Table I that Eastern and Central provinces and Jeddah in Western province have nearly some radon concentration.
In the Eastern province one notices the difference in radon concentration between houses in Dammam and Khobar (~0.3 pCi/l) and Dhahran/University (~0.4 pCi/]). It may be mentioned that houses in Dammam and Khobar are not centrally airconditioned as are in the University. This will be responsible for a better ventilation in the houses in Dammam and Khobar thus may result in lower radon concentration as compared to the University houses.
The highest concentration found in "Taif" city (0.98 pCi/l) could be due to the fact that it is a cold place having low ventilation in the buildings. The other possibility could be due to a high concentration of uranium in the building materials. This will be studied in the near future.
Table 2 lists the radon concentration in exceptional places in Eastern province. The highest concentration was recorded in unoccupied closed houses in the University campus (0.81 pCi/l). These houses are newly constructed and are centrally airconditioned. During the monitoring period these houses were unoccupied and the airconditioning was not on, which meant almost negligible ventilation. Poor ventilation could be the reason for such a high activity. This conclusion supports the high activity monitored in Tail. The other University campus houses were populated and are centrally airconditioned all the time with cooling and heating system. Their concentration (0.39 pCi/l) is about half of the concentration in the closed houses (0.81 pCi/l) lying in the same campus and similar construction material. This means that ventilation is the main reason for the difference in concentration between the two groups of houses. Earlier studies also showed the importance of ventilation on radon concentration (Abu-Jarad & Fremlin 1982,83). The least concentration (O.13 pCi/l) was recorded in the offices of the academic campus. This could be because of higher ventilation rate in the office buildings. Also the building materi~l oer unit volume in the academic building is less than that of the campus houses. The frequency
distribution
of all samples
in Fig. 2 shows
log normal
distribution
due to
RADON ACTIVITY IN SAUDI HOUSES
the varlatior~ and another.
in radon concentration
in houses
397
in the same city and between one city
CONCLUSION The average radon concentration in all the analyzed samples (636) is 0.41 pCi/l. This average is nearly equal to an average from similar study carried out in the U.K. (0.42 pCi/l in winter season) - Abu-Jarad and Fremlin 1984 (to be published in Health Physics). In both cases the ventilation was kept minimum possible, in UK to keep houses warm while in Saudi Arabia to keep them cool in summer. Thus the ventilation was poor in both the cases. It is concluded that the large variation in the radon concentration is mainly due to the different rate of ventilation. ACKNOWLEDGMENT We ~ u l d like to thank the University of Petroleum and Minerals for supporting this project referenced PHYS/RADON 222/59. Thanks are also due to J. Miles of the NRPB in the U.K. for his cooperation in the calibration of the system. Thanks also to Mr. D.A. Khan for his assistance and Mr. M.A. Shad for secretarial help. REFERENCES Abu-Jarad,
F. and Fremlin, J.H. and Bull R.K. 1980, Phys. Med. Biol. 25 (4) 683-694.
Abu-Jarad and Fremlin, J. 1982, Health Physics 43, pp. 75-80. Abu-Jarad and Fremlin, J.H., Health Physics,
1983, 44 (5) PP.479-
Abu-Jarad and Fremlin, J. 1984, l!ealth Physics. Alter, H.M. and Fleischer,
In press.
R.L. 1981, Health Physics, 420, pp. 693-702.
Frank, A.L. and Benton, E.V., 1977, Nuclear Track ~, pp. 149-179. Miles, J.C.H. and Dew, E.J., 1981, in proceeding of the 11th International Conference on Solid State Nuclear Track Detectors, Bristol, 7-12 Sept. 1981 published as supplement No: 3 to the journal Nuclear Track. Urban, M. and Piesch, E. 1981, in proceeding of the 11th International Conference on Solid State Nuclear Track Detectors, Bristol, 7-12 Sept. 1981 published as supplement No: 3 to the journal Nuclear Track. TABLE
Province
Eastern
Central Western All
I
-
RADON CONCENTRATION (pCi/l) IN DIFFERENT CITIES LOCATED IN DIFFERENT PROVINCES OF SAUDI ARABIA
City
# of samples
Dammam Khoba r Dhahran/ University Houses.
Jeddah Tall
! i I i
Mean by city pCi/l
34 38 339
0.3±0.02 0.27±0.03 0.39±0.02
118 77 30 636
O.41±0.02 0.35±0.03 0.98±0.07
Mean by province pCi/l 0.38±0.02
0.41±0.02 I
0.52±0.04 O.41±0.02
398
F. A B U - J A R A D and M. 1. A L - J A R A L L A H
TABLE 2 - RADON CONCENTRATION ( p C i / l ) IN EXCEPTIONAL PLACES IN EASTERN PROVINCE
CONDITION OF THE HOUSES
MEAN pCi/l
# OF SAMPLES
Occupied University Houses
202
0.39+_0.02
41
0.81_+0.22
13
0.13_+0.01
Unoccupied University Houses Offices in Academic Buildings.
18o 7.6
cm
I=
160
I
I
140 3.2 120
bO >m
CR-39 detector
]m
100
I
I
8o 5.8 cm
u.l kL
Fig.
6o
I. A CROSS SECTION OF THE PASSIVE ENVIRONMENTAL DOSIMETER FOR MEASURING RADON CONCENTRATION IN HOUSES.
4O
20
i
0.2
O.
Th 0.6
0.8
RADON CONCENTRATION FIG. 2.
I
I .25
I .5
pCi/l
THE FREQUENCY DISTRIBUTION AS A FUNCTION OF RADON CONCENTRATION FOR 636 CR-39 DETECTORS PLACED IN DIFFERENT AREAS IN SAUDI ARABIA.
,
0191 278X/84 $3.00 + .00 1984 Pergamon Press Ltd.
RADON ACTIVITY IN SAUDI HOUSES F. Abu-Jarad & M.I. AI-Jarallah Department of Physics University of Petroleum & Minerals Dhahran, Saudi Arabia
ABSTRACT Long term measurements of radon's concentrations inside Saudi Houses being studied using CR-39 Plastic Track Detectors fixed inside sealed plastic cups. The cups were left for about 7 months in the houses. The measurements were done in different cities of different provinces in the country. The analysis of 636 cups showed that the radon concentration in different cities was ranging from 0.27 pCi/l (in Khobar) to 0.98 pCi/l (in Taif). In exceptional places in Eastern Province, it is found that the lowest concentration was in the University offices (0.13 pCi/l) and the highest was in the University unoccupied houses (0.81 pCi/l). It is found that the ventilation is the main factor affecting the radon concentration in houses.
KEYWORDS
Radon concentration,
Saudi Arabia, CR-39 Track Detectors,ventilation.
INTRODUCTION
The estimation of long exposure of populations to low levels of radon and its decay products in dwelling is a general problem. Thus recently several surveys for measuring the concentration of radon and its products have been done. Some of these surveys measured the integrated value of radon over long periods of times using passive track detectors (Frank & Benton 1977, Alter & Fleisher 1981, Miles 1981, Urban & Piesch 1981 Abu-Jarad 1980, 1984). The long-time-integrated measurements should give better estimations of population dose than short-time ones, since they give long-term average exposures in the conditions in which the inhabitants of the house live their normal lives. This is the first survey which was done in Saudi Arabia. Most of the surveys reported uptil now were carried out in cold countries like Europe, Canada and USA. Therefore this survey may be of some interest as it was carried out in a hot country.
The majority of the houses are constructed of concrete and blocks (crushed stones + sand + cement). The country is generally very hot in summer season which extends for most of the year. Most of the buildings which were monitored were airconditioned. In winter the weather is quite cold particularly in Central and Eastern Provinces, while it is mild in the Western province. The humidity levels are high in both Western and Eastern provinces because they are located along the Red Sea and the Arabian Gulf respectively while the levels are low in the Central province. "Taif" city is an exceptional case because it lies on top of mountains 1200 ft above sea level, and is cold in winter and mild in summer.
METHOD In this survey a plastic cup was used as a holder for a CR-39 Plastic Track Detector 395
396
F. ABU J A R A D and M. 1. A L - J A R A L L A H
(Pershore Molding Ltd.) which is fixed inside the bottom of the cup (Fig.l). A hole was made in the cover of the cup which was then sealed from inside with foam. This was done to stop the aerosole and daughter's particles from entering the cup while allowing the radon gas among other air consistuents to pass through. In the decay of radon-222 to its short lived daughters (Z18Po, 214Pb, 21~Bi, 214Po), three alpha particles will be emitted in this series from Rn, 218Po and 214Po (5.49, 6.00 and 7.68 MeV respectively). Some of these m-particles will hit the plastic if it falls within their ranges. Therefore the CR-39 detector will accumulate by time number of tracks proportional to the concentration of radon gas in the room.
Two to three cups were placed in each house in different rooms for a perlod of about 7 months. In total 1200 cups were distributed throughout the main cities in the country. Out of these 636 detectors were analyzed and the remaining are yet to be analyzed. The results of these analyses are presented here. The etching conditions are 70°C, 30% KOH, 9 hour and the solution was continuously stirred. The system was calibrated in the National Radiological Protection Board (NRPB) in Harwell, U.K.
RESULTS Table 1 gives results of all the analyzed samples from different provinces. The following observations can be made from the table. It is clear from Table I that Eastern and Central provinces and Jeddah in Western province have nearly some radon concentration.
In the Eastern province one notices the difference in radon concentration between houses in Dammam and Khobar (~0.3 pCi/l) and Dhahran/University (~0.4 pCi/]). It may be mentioned that houses in Dammam and Khobar are not centrally airconditioned as are in the University. This will be responsible for a better ventilation in the houses in Dammam and Khobar thus may result in lower radon concentration as compared to the University houses.
The highest concentration found in "Taif" city (0.98 pCi/l) could be due to the fact that it is a cold place having low ventilation in the buildings. The other possibility could be due to a high concentration of uranium in the building materials. This will be studied in the near future.
Table 2 lists the radon concentration in exceptional places in Eastern province. The highest concentration was recorded in unoccupied closed houses in the University campus (0.81 pCi/l). These houses are newly constructed and are centrally airconditioned. During the monitoring period these houses were unoccupied and the airconditioning was not on, which meant almost negligible ventilation. Poor ventilation could be the reason for such a high activity. This conclusion supports the high activity monitored in Tail. The other University campus houses were populated and are centrally airconditioned all the time with cooling and heating system. Their concentration (0.39 pCi/l) is about half of the concentration in the closed houses (0.81 pCi/l) lying in the same campus and similar construction material. This means that ventilation is the main reason for the difference in concentration between the two groups of houses. Earlier studies also showed the importance of ventilation on radon concentration (Abu-Jarad & Fremlin 1982,83). The least concentration (O.13 pCi/l) was recorded in the offices of the academic campus. This could be because of higher ventilation rate in the office buildings. Also the building materi~l oer unit volume in the academic building is less than that of the campus houses. The frequency
distribution
of all samples
in Fig. 2 shows
log normal
distribution
due to
RADON ACTIVITY IN SAUDI HOUSES
the varlatior~ and another.
in radon concentration
in houses
397
in the same city and between one city
CONCLUSION The average radon concentration in all the analyzed samples (636) is 0.41 pCi/l. This average is nearly equal to an average from similar study carried out in the U.K. (0.42 pCi/l in winter season) - Abu-Jarad and Fremlin 1984 (to be published in Health Physics). In both cases the ventilation was kept minimum possible, in UK to keep houses warm while in Saudi Arabia to keep them cool in summer. Thus the ventilation was poor in both the cases. It is concluded that the large variation in the radon concentration is mainly due to the different rate of ventilation. ACKNOWLEDGMENT We ~ u l d like to thank the University of Petroleum and Minerals for supporting this project referenced PHYS/RADON 222/59. Thanks are also due to J. Miles of the NRPB in the U.K. for his cooperation in the calibration of the system. Thanks also to Mr. D.A. Khan for his assistance and Mr. M.A. Shad for secretarial help. REFERENCES Abu-Jarad,
F. and Fremlin, J.H. and Bull R.K. 1980, Phys. Med. Biol. 25 (4) 683-694.
Abu-Jarad and Fremlin, J. 1982, Health Physics 43, pp. 75-80. Abu-Jarad and Fremlin, J.H., Health Physics,
1983, 44 (5) PP.479-
Abu-Jarad and Fremlin, J. 1984, l!ealth Physics. Alter, H.M. and Fleischer,
In press.
R.L. 1981, Health Physics, 420, pp. 693-702.
Frank, A.L. and Benton, E.V., 1977, Nuclear Track ~, pp. 149-179. Miles, J.C.H. and Dew, E.J., 1981, in proceeding of the 11th International Conference on Solid State Nuclear Track Detectors, Bristol, 7-12 Sept. 1981 published as supplement No: 3 to the journal Nuclear Track. Urban, M. and Piesch, E. 1981, in proceeding of the 11th International Conference on Solid State Nuclear Track Detectors, Bristol, 7-12 Sept. 1981 published as supplement No: 3 to the journal Nuclear Track. TABLE
Province
Eastern
Central Western All
I
-
RADON CONCENTRATION (pCi/l) IN DIFFERENT CITIES LOCATED IN DIFFERENT PROVINCES OF SAUDI ARABIA
City
# of samples
Dammam Khoba r Dhahran/ University Houses.
Jeddah Tall
! i I i
Mean by city pCi/l
34 38 339
0.3±0.02 0.27±0.03 0.39±0.02
118 77 30 636
O.41±0.02 0.35±0.03 0.98±0.07
Mean by province pCi/l 0.38±0.02
0.41±0.02 I
0.52±0.04 O.41±0.02
398
F. A B U - J A R A D and M. 1. A L - J A R A L L A H
TABLE 2 - RADON CONCENTRATION ( p C i / l ) IN EXCEPTIONAL PLACES IN EASTERN PROVINCE
CONDITION OF THE HOUSES
MEAN pCi/l
# OF SAMPLES
Occupied University Houses
202
0.39+_0.02
41
0.81_+0.22
13
0.13_+0.01
Unoccupied University Houses Offices in Academic Buildings.
18o 7.6
cm
I=
160
I
I
140 3.2 120
bO >m
CR-39 detector
]m
100
I
I
8o 5.8 cm
u.l kL
Fig.
6o
I. A CROSS SECTION OF THE PASSIVE ENVIRONMENTAL DOSIMETER FOR MEASURING RADON CONCENTRATION IN HOUSES.
4O
20
i
0.2
O.
Th 0.6
0.8
RADON CONCENTRATION FIG. 2.
I
I .25
I .5
pCi/l
THE FREQUENCY DISTRIBUTION AS A FUNCTION OF RADON CONCENTRATION FOR 636 CR-39 DETECTORS PLACED IN DIFFERENT AREAS IN SAUDI ARABIA.