J. K. Amoako

ASSESSMENT OF RADIOFREQUENCY RADIATION WITHIN THE VICINITY OF SOME GSM BASE STATIONS IN GHANA

A radiofrequency (RF) electromagnetic radiation safety survey had been carried out at public access points in 46 towns with 76 Global Systems for Mobile communication cell sites in two major cities in Ghana. The objective was to determine the levels of RF field in residential areas, schools and market places, and compare the measured results with the guidelines set by the International Commission of Non-Ionising Radiation (ICNIRP). Measurements were made with log-periodic antenna coupled with spectrum analyzer. The results varied from 0.85 to 1.07 mW m(-2) and 0.78 to 1.19 mW m(-2) for the transmission frequencies of 900 and 1800 MHz, respectively. The result generally shows a compliance with the ICNIRP limit of 0.024 % but was 108 times higher than a similar survey carried out in Ghana 2 y ago.

Measurement and analysis of radiofrequency radiations from some mobile phone base stations in Ghana.

A survey of the radiofrequency electromagnetic radiation at public access points in the vicinity of 50 cellular phone base stations has been carried out. The primary objective was to measure and analyse the electromagnetic field strength levels emitted by antennae installed and operated by the Ghana Telecommunications Company. On all the sites measurements were made using a hand-held spectrum analyser to determine the electric field level with the 900 and 1800 MHz frequency bands. The results indicated that power densities at public access points varied from as low as 0.01 microW m(-2) to as high as 10 microW m(-2) for the frequency of 900 MHz. At a transmission frequency of 1800 MHz, the variation of power densities is from 0.01 to 100 microW m(-2). The results were found to be in compliant with the International Commission on Non-ionizing Radiological Protection guidance level but were 20 times higher than the results generally obtained for such a practice elsewhere. There is therefore a need to re-assess the situation to ensure reduction in the present level as an increase in mobile phone usage is envisaged within the next few years.

Patient dose assessment due to fluoroscopic exposure for some selected fluoroscopic procedures in Ghana

Organ and effective doses to 90 patients undergoing some selected fluoroscopic examinations at the Korle-Bu Teaching Hospital were estimated using the Monte Carlo-based program (PCXMC version 1.5). Radiation dose was estimated from free-in-air measurements. The mean effective doses were found to be 0.29 +/- 0.07, 0.84 +/- 0.13, 3.15 +/- 0.44, 6.24 +/- 0.70 and 0.38 +/- 0.05 mSv for urethrogram, barium swallow, barium meal, barium enema and myelogram examinations, respectively. The dose area product was estimated to be 3.55 +/- 0.95, 16.44 +/- 2.60, 50.81 +/- 7.04, 99.69 +/- 10.85 and 9.32 +/- 0.99 Gy cm(2) for urethrogram, barium swallow, barium meal, barium enema and myelogram examinations, respectively. Optimisation of procedures is required for barium enema and barium meal examinations.

Analysis of calibration results of radiation survey meters used for area monitoring.

Analyses of the results of calibration of survey meters carried out at the Secondary Standards Dosimetry Laboratory (SSDL) in Ghana over a period of 4 y (2008-2011) are reported. The calibration factors (CFs) of the set of survey meters indicated that ∼91.04 % were within the acceptable limit of ± 20.0 %. A higher percentage of the survey meters indicated CFs in the range of 0.95-1.15 except a few of them which indicated values <0.55. Some of the survey meters also recorded CFs >1.15. The degree of uncertainty in the measurements ranged from 0.03 to 17 % with the majority of them ranging from 0.03 to 6.0 % and a few of them >6.0 %. The results show that most of the survey meters calibrated were within the requirements of the regulations and may provide data for future development of calibration techniques in the country.

Implementation of dose management system at radiation protection board of Ghana Atomic Energy Commission

The dose management system (DMS) is a computer software developed by the International Atomic Energy Agency for managing data on occupational exposure to radiation sources and intake of radionuclides. It is an integrated system for the user-friendly storage, processing and control of all existing internal and external dosimetry data. The Radiation Protection Board (RPB) of the Ghana Atomic Energy Commission has installed, customised, tested and using the DMS as a comprehensive DMS to improve personnel and area monitoring in the country. Personnel dose records from the RPBs database from 2000 to 2009 are grouped into medical, industrial and education/research sectors. The medical sector dominated the list of monitored institutions in the country over the 10-y period representing ∼87 %, while the industrial and education/research sectors represent ∼9 and ∼4 %, respectively. The number of monitored personnel in the same period follows a similar trend with medical, industrial and education/research sectors representing ∼74, ∼17 and ∼9 %, respectively. Analysis of dose data for 2009 showed that there was no instance of a dose above the annual dose limit of 20 mSv, however, 2.7 % of the exposed workers received individual annual doses >1 mSv. The highest recorded individual annual dose and total collective dose in all sectors were 4.73 mSv and 159.84 man Sv, respectively. Workers in the medical sector received higher individual doses than in the other two sectors, and average dose per exposed worker in all sectors is 0.25 mSv.

Assessment of annual whole-body occupational radiation exposure in medical practice in Ghana (2000–09)

Occupational exposure to radiation in medical practice in Ghana has been analysed for a 10-y period between 2000 and 2009. Monitored dose data in the medical institution in Ghana from the Radiation Protection Institutes database were extracted and analysed in terms of three categories: diagnostic radiology, radiotherapy and nuclear medicine. One hundred and eighty medical facilities were monitored for the 10-y period, out of which ~98% were diagnostic radiology facilities. Only one nuclear medicine and two radiotherapy facilities have been operational in the country since 2000. During the 10-y study period, monitored medical facilities increased by 18.8%, while the exposed workers decreased by 23.0%. Average exposed worker per entire medical institution for the 10-y study period was 4.3. Annual collective dose received by all the exposed workers reduced by a factor of 4 between 2000 and 2009. This is seen as reduction in annual collective doses in diagnostic radiology, radiotherapy and nuclear medicine facilities by ~76, ~72 and ~55%, respectively, for the 10-y period. Highest annual collective dose of 601.2 man mSv was recorded in 2002 and the least of 142.6 man mSv was recorded in 2009. Annual average values for dose per institution and dose per exposed worker decreased by 79 and 67.6%, respectively between 2000 and 2009. Average dose per exposed worker for the 10-y period was least in radiotherapy and highest in diagnostic radiology with values 0.14 and 1.05 mSv, respectively. Nuclear medicine however recorded average dose per worker of 0.72 mSv. Correspondingly, range of average effective doses within the diagnostic radiology, radiotherapy and nuclear medicine facilities were 0.328-2.614, 0.383-0.728 and 0.448-0.695 mSv, respectively. Throughout the study period, an average dose per medical institution of 3 mSv and an average dose per exposed worker of 0.69 mSv were realised. Exposed workers in diagnostic radiology primarily received most of the individual annual doses >1 mSv. The entire study period had 705 instances in which exposed workers received individual annual doses >1 mSv. On thermoluminescent dosemeter (TLD) return rates, facilities in Volta and Eastern Regions recorded highest return rates of 94.3% each. Ashanti Region recorded the least TLD return rate with 76.7%.

Assessment of annual whole-body occupational radiation exposure in education, research and industrial sectors in Ghana (2000-09).

Institutions in the education, research and industrial sectors in Ghana are quite few in comparison to the medical sector. Occupational exposure to radiation in the education, research and industrial sectors in Ghana have been analysed for a 10 y period between 2000 and 2009, by extracting dose data from the database of the Radiation Protection Institute, Ghana Atomic Energy Commission. Thirty-four institutions belonging to the three sectors were monitored out of which ∼65% were in the industrial sector. During the 10 y study period, monitored institutions ranged from 18 to 23 while the exposed workers ranged from 246 to 156 between 2000 and 2009. Annual collective doses received by all the exposed workers reduced by a factor of 2 between 2000 and 2009. This is seen as a reduction in annual collective doses in education/research and industrial sectors by ∼39 and ∼62%, respectively, for the 10 y period. Highest and least annual collective doses of 182.0 man mSv and 68.5 man mSv were all recorded in the industrial sector in 2000 and 2009, respectively. Annual average values for dose per institution and dose per exposed worker decreased by 49 and 42.9%, respectively, between 2000 and 2009. Average dose per exposed worker for the 10 y period was least in the industrial sector and highest in the education/research sector with values 0.6 and 3.7 mSv, respectively. The mean of the ratio of annual occupationally exposed worker (OEW) doses for the industrial sector to the annual OEW doses for the education/research sector was 0.67, a suggestion that radiation protection practices are better in the industrial sector than they are in the education/research sector. Range of institutional average effective doses within the education/research and industrial sectors were 0.059-6.029, and 0.110-2.945 mSv, respectively. An average dose per all three sectors of 11.87 mSv and an average dose per exposed worker of 1.12 mSv were realised for the entire study period. The entire study period had 187 instances in which exposed workers received individual annual doses >1 mSv, with exposed workers in the education/research sector primarily receiving most of this individual dose.

PUBLIC EXPOSURE TO MULTIPLE RF SOURCES IN GHANA

This paper describes an effort to respond to the suggestion in World Health Organization (WHO) research agenda to better quantify potential exposure levels from a range of radiofrequency (RF) sources at 200 public access locations in Ghana. Wide-band measurements were performed-with a spectrum analyser and a log-periodic antenna using three-point spatial averaging method. The overall results represented a maximum of 0.19% of the ICNIRP reference levels for public exposure. These results were generally lower than found in some previous but were 58% (2.0 dB) greater, than found in similar work conducted in the USA. Major contributing sources of RF fields were identified to be FM broadcast and mobile base station sites. Three locations with the greatest measured RF fields could represent potential areas for epidemiological studies.

ANALYSIS OF ELECTRIC FIELD STRENGTH AND POWER AROUND SELECTED MOBILE BASE STATIONS

The analysis of channel power and electric field strength at various locations from mobile base stations using power sensor, spectrum analyzer and log-periodic antenna revealed maximum potential exposure between the range of 61.1 and 254.7 m. Generally, the potential exposure values ranged from 0.0717 to 0.8950 mW m-2 with a maximum deviation of 22.22%. GSM900 was found to be more pronounced than GSM1800 and UMTS2100. Though the results complied with ICNIRP reference levels with a wide margin of 0.01%, it was higher than some previous work and South African mean value of 0.16 mW m-2, agreed with similar work elsewhere but lower than a global average value of 0.730 mW m-2.

SPATIAL DISTRIBUTION OF ELECTRIC FIELD STRENGTH AT A TEACHING HOSPITAL PREMISES DUE TO TRANSMISSIONS BETWEEN 87.5 MHz AND 2.6 GHz

A radiofrequency (RF) electromagnetic radiation safety assessment had been carried out at public access points within the compound of a teaching hospital. The frequency band investigated ranged from 87.5 MHz to 2.6 GHz. Eighty-eight measurements were made using a spectrum analyser coupled with a log-periodic antenna. The objective was to determine the level and nature of RF fields within the immediate premise of the facility where patients of health conditions are kept and treated. Results complied with the International Commission of Non-Ionising Radiation (ICNIRP) guidelines. The values of the resolved electric field at four spatial heights ranged from 1.00 ± 0.144 mV/m to 1.174 ± 0.169 V/m. Power densities varied from 2.65 ± 0.38 nWm-2 to 3.66 ± 0.528 mWm-2. There were relatively high contributions from frequencies above 900 MHz compared with contributions from lower frequency bands.