Radiological impact of dietary intakes of naturally occurring radionuclides on Pakistani adults.

Daily dietary intakes of three naturally occurring long-lived radionuclides (232)Th, (238)U and (40)K were estimated for the adult population of Pakistan using neutron activation analysis (NAA), inductively coupled plasma mass spectrometry (ICP-MS) and atomic absorption spectrometry (AAS), respectively. The daily intakes of (232)Th ranged from 4 to 29 mBq, (238)U ranged from 17 to 82 mBq and (40)K ranged from 51 to 128 Bq. The geometric means of these intakes were 10 mBqd(-1) for (232)Th, 33 mBqd(-1) for (238)U and 78.5 Bqd(-1) for (40)K. The measured values give annual committed effective doses of 0.80, 0.53 and 178.75 microSvyr(-1) for (232)Th, (238)U and (40)K, respectively to Pakistani population. The net radiological impact of these radionuclides is 180.08 microSvyr(-1). This value gives cancer risk factor of 4.5 x 10(-4) and loss of life expectancy of 0.87 days only. Whereas ICRP cancer risk factor for general public is 2.5 x 10(-3) and total risk involve from the all natural radiation sources based on global average annual radiation dose of 2.4 mSvyr(-1) is 6.0 x 10(-3). The estimated cancer risk shows that probability of increase of cancer risk from daily Pakistani diet is only a minor fraction of ICRP values. Therefore, the diet does not pose any significant health hazard and is considered radiologically safe for human consumption.

Radiation protection aspects of shallow land disposal of low and intermediate level liquid and solid radioactive waste at PINSTECH.

Operation of Pakistan Research Reactors 1 and 2, radioisotope production plants, and allied laboratories at the Pakistan Institute of Nuclear Science & Technology (PINSTECH) generates radioactive waste effluents of low and intermediate level. These waste materials are managed in a way to keep the human health and the environment free of radiation associated hazards. The prime practice has been of shallow ground or near-surface disposal type. Different measures and operational procedures at the institute, in step with the international norms for the management of low and intermediate level waste, have been adopted. To ensure the safe disposal practices and radiation safety of the workers and of the general public, radiological safety related routines are practiced with due concern. Some safety aspects of the prevailing practices are discussed in this presentation.

Assessment of strontium and calcium levels in Pakistani diet.

To cope with nuclear emergency effectively due to ingestion of fission fragment (90)Sr, adequacy of nutritionally and radiologically important elements strontium and calcium was studied in typical Pakistani diet and baseline analytical data were generated. Concentrations of strontium and calcium were measured by using inductively coupled plasma-atomic emission spectroscopy (ICP-AES) and atomic absorption spectrometry (AAS) techniques. Daily dietary intake of strontium and calcium varied from 0.9 to 5.7 mg and 217 to 713 mg with the geometric mean value x geometric standard deviation of 2.6 x 1.7 and 487.1 x 1.4 mg d(-1), respectively. The average Sr concentration in the Pakistani diet was 1.4 times higher while Ca concentration was 0.4 times lower than the recommended values of the International Commission on Radiological Protection (ICRP). The calculated Sr/Ca ratio 5.3E-03 was also higher than the ICRP value. The study depicts that the strontium concentration in the Pakistani diet is adequate, while the calcium concentration is inadequate according to international standards and needs improvement.

Thorium concentration in Pakistani diet.

To evaluate radiation doses due to ingestion of thorium activity by members of the public, baseline analytical data on thorium concentration in a typical Pakistani diet was generated. Food samples were collected from major districts/ cities of the country using the market basket method, and typical daily diets were prepared. Thorium concentration was determined by instrumental neutron activation analysis. It was found to vary from 1.6 ng g(-1) to 12 ng g(-1). The median value was 4.6 ng g(-1). This leads to median daily thorium intake of 2.7 microg d(-1). The geometric mean was 2.6 microg d(-1), which was 13% less than the ICRP value. Based on these measurements the average intake of 232Th activity was 10 mBq d(-1), and the average annual and committed effective doses for adults were estimated to be 8.8 x 10(-7) Sv y(-1) and 4.4 x 10(-5) Sv, respectively.

Caesium concentration in the Pakistani diet.

Daily dietary intakes of radioactive and non-radioactive caesium for the Pakistani population were measured. Food samples were collected on market basket method and were analysed using Instrumental Neutron Activation Analysis technique. The radioactive caesium ((137)Cs) in these samples was below the detectable limit, i.e. 1 mBq g(-1). The geometric mean of the mass fraction of stable caesium was 9.56 x 1.53 ng g(-1). The estimated daily dietary intake of caesium was 5.65 x 1.53 microg d(-1) or 0.088 microg kg(-1) of body weight of the reference Pakistani man weighing 64 kg. These values are 38.2% smaller than the recommended ICRP values for a 70 kg standard man. However, caesium concentration in the Pakistani diet is comparable with other reported values in the literature.

Nutritional and radiological impact of dietary potassium on the Pakistani population.

The nutritional status of dietary potassium and the radiological impact of its isotope (40)K were estimated for the Pakistani population. Potassium concentration was determined in dietary samples by atomic absorption spectrometry. An average potassium concentration was 4.54+/-0.89 mg/g, which leads to potassium dietary intake of 2.69+/-0.54 g/day and the radiological hazard due to (40)K activity was 79.94 Bq/day. The annual and lifetime effective doses calculated for the reference Pakistani man weighing 64 kg due to measured activity of (40)K were found to be 1.65 x 10(-4) Sv y(-1) and 8.27 x 10(-3) Sv, respectively. Measured data showed that the potassium concentration in the Pakistani diet is adequate and safe according to international standards.

Intercomparison of INAA and ICP-MS results for thorium determination in Pakistani diet.

A pilot study on ingestion and organ content of trace elements of importance in radiological protection was to be carried out in Pakistan. Baseline analytical data on daily dietary intake of thorium was to be measured using Instrumental Neutron Activation Analysis (INAA) technique. To determine the accuracy and reliability of our technique, some samples were measured in Pakistan using INAA and in Japan using Inductively Coupled Plasma-Mass Spectrometry. For intercomparison of results overall mean Z-scores were calculated. The results showed validity of our technique. Mean value of 232Th concentration in Pakistani diet samples using INAA technique is 0.0062 +/- 0.0028 microg/g and with ICP-MS technique is 0.0069 +/- 0.0032 microg/g.

Norm and associated radiation hazards in bricks fabricated in various localities of the North-West Frontier Province (Pakistan).

The activity concentrations of natural gamma-emitting radionuclides and associated radiation hazards due to 40K, 226Ra and 232Th have been measured in baked brick samples, collected from six highly populated areas of the North-West Frontier Province (NWFP) of Pakistan. For the detection, analysis and data acquisition, a high purity germanium (HPGe) detector coupled with a high resolution multichannel analyser (MCA) was used. The range of the average values of the activity concentrations due to 40K, 226Ra and 232Th were found to be 680.3 +/- 22.2-784.4 +/- 30.7 Bq kg(-1), 36.9 +/- 3.5-51.9 +/- 3.3 Bq kg(-1) and 52.5 +/- 3.6-67.6 +/- 3.1 Bq kg(-1), respectively. Radium equivalent (Ra(eq)) activities and various hazard indices were also calculated to assess the radiation hazards. All the brick samples showed Ra, activities within the limit (370 Bq kg(-1)) set by the Organization for Economic Cooperation and Development (OECD) countries. The results of different criterion formulae also complemented each other in this study. The derived data have been compared with the reported values for other countries of the world.

Assessment of the natural radioactivity and its radiological hazards in Shewa-Shahbaz Garhi igneous complex, Peshawar Plain, NW Pakistan.

Forty-two representative rock samples used for construction purpose were collected from the quarries and outcrops of the rock units forming the Shewa-Shahbaz Garhi igneous complex, North-West Pakistan. Radioactivity of terrestrial radionuclides (238U, 232Th, and 40K) was measured in these samples using gamma ray spectrometry system with an HPGe detector. The samples showed fairly high mean concentrations of 51 +/- 16 Bq kg(-1) of 238U, 70 +/- 20 Bq kg(-1) of 232Th and 1,272 +/- 367 Bq kg(-1) of 40K. Mean absorbed gamma dose rate in air of 119 +/- 29 nGy h(-1) was found. Assessment of radiological hazards was made by calculating radium equivalent activities with external and internal hazard indices. The calculations showed radium equivalent activity ranging from 52 to 346 Bq kg(-1). External and internal hazard indices ranging from 0.14 to 0.94 and 0.17 to 1.1, respectively, were found.

Radiological significance of building bricks in Pakistan.

Baked clay bricks samples were collected from both urban and rural areas of the North West Frontier Province of Pakistan and natural radioactivity due to 40K, 226Ra and 232Th has been measured in these samples. The specific absorbed dose rates due to natural radioactivity emanating from the walls, floors and ceilings of the typical model rooms made of these building bricks have been calculated applying the mesh size adaptive volume integral methodology. The occupancy factor, representing the weighted average of all the population in the country, was taken to be 0.3 in this study. The values of estimated annual effective dose rates for whole body were found to be 0.38 and 0.35 mSv.y(-1) for the two types of model rooms. These values are smaller than those predicted by UNSCEAR for normal background areas. Thus the building bricks analysed in this study do not pose any significant health problem to the population.

Radiological impact on the workers, members of the public, and environment from the partial decommissioning of Pakistan Research Reactor-I and its associated radioactive residues.

The Pakistan Research Reactor-I (PARR-I) is a swimming pool type research reactor originally designed and built for a thermal power of 5 MW using High Enriched Uranium (HEU) fuel. In 1990-1991 the reactor was redesigned, partially decommissioned and recommissioned to operate with Low Enriched Uranium (LEU) fuel at a thermal power of 10 MW. An essential requirement, construction and commissioning of a wet spent fuel storage bay and fabrication of an irradiated fuel transfer cask were completed before actual dismantling of the reactor core. During the partial decommissioning operations, radioactive waste generated included 600 m3 low-level liquid radioactive waste and 14 m3 of solid radioactive waste with an average specific activity of 4.52 Bq ml(-1) and 2.22 kBq g(-1), respectively. External radiation doses of the workers were determined using TLD (NG 6,7) and direct reading dosimeters. The maximum individual external radiation dose received by any worker during this practice was 5 mSv, which was 25% of the annual dose limit of 20 mSv. Detection and measurement of internal contamination was carried out using bioassay techniques. During the whole operation, not a single case of internal contamination was detected. The ambient radiation levels around waste seepage pits are periodically monitored using TLD (G-2 cards) and G. M. radiation survey meters. Underground migration of radioactivity is checked by analyzing seepage water samples taken from boreholes that have been dug at different locations in the vicinity of the radioactive residues. The monitoring around disposal sites containing radioactive residues has been continued during the last 9 y and will be continued in the future. So far, no rise in the environmental gamma radiation dose level and migration of underground radionuclides has been found in the vicinity of these disposal sites. Working personal during the decommissioning of PARR-I have been found to be radiologically safe. Adherence to the ALARA principle, sound decommissioning and proper radioactive waste disposal procedures helped to protect the working personnel, members of the public, and the environment from the harmful effects of the ionizing radiations present due to the partial decommissioning of the research reactor and its radioactive residues. Experience gained during this work, along with the current international procedures, will be helpful for full restoration of the environment from radioactive residues likely to be generated in the future from any other practices in Pakistan.

Evaluation of body mass index for a reference Pakistani man and woman.

To strengthen the radiation protection infrastructure, a pilot study on physical characteristics for Reference Asian Man was carried out in Pakistan. Physical data on height and weight of Pakistani men and women were collected and compiled for all age groups to establish a Reference Pakistani Man/Woman which contributed toward the Reference Asian Man/Woman. A correlation between Age and Body Mass Index (BMI) of Pakistani MALES (i.e., rm = +0.89) and FEMALES (i.e., rf = +0.71) was observed. Average BMI of Pakistani males and females for the age group of 20-50 y was found to be 21.95 kg m(-2) and 21.20 kg m(-2), respectively. From recent literature and work of others BMI for Reference Asian Male (RAM) and Reference Asian Female (RAF) has been found to be 20.79 kg m(-2) and 20.81 kg m(-2). Results of our study fall within BMI ranges for male/female adults of Asian countries, i.e., 19.14-22.98 kg m(-2) and 19.38-22.71 kg m(-2), respectively. However, no significant sex specific difference has been noted.