Age-dependent Effective Dose Research Articles

Assessment of Age-Dependent Effective Dose and Toxicity Risks Due To Ingestion of 226RA and 228RA in River Water Samples in a Part of Bitumen Belt, Ondo State. Nigeria

Exposure to naturally occurring radioactive chemical elements in food and water is attracting the attention of many researchers in recent times because of its deleterious health effects. In this study, the activity concentrations of natural radionuclides in some river waters in southwestern Nigeria were measured using high-purity germanium (HPGe) detector. They ranged from 0.12 to 2.31, 0.17 to 2.85, and 7.86 to 65.51 Bql-1 for 226Ra, 228Ra, and 40K respectively. Mean of the total annual effective dose were 9.86, 2.46, 1.71, 2.43, 5.74, and 0.99 mSvy-1 for age groups ≤1y, 1-2y, 2-7y, 7-12y, 12-17y, and >17y respectively. Estimated mass concentration of 226Ra and 228Ra in the samples ranged from 3.29x10-6 to 59.71x10-6 µgl-1 with a mean of 35.04x10-6 µgl-1 and 1.69x10-8 to 28.30x10-8 µgl-1 with a mean of 14.30x10-8 µgl-1 respectively. Mortality and morbidity risks ranged from 0.04x10-3 to 0.77x10-3 with a mean of 0.42x10-3 and 0.04x10-3 to 0.80x10-3 with a mean of 0.44x10-3 respectively for 226Ra while they ranged from 0.11x10-3 to 1.89x10-3 with a mean of 0.96x10-3 and 0.16x10-3 to 2.66x10-3 with a mean of 1.38x10-3 respectively for 228Ra. Lifetime average daily dose (LADD) of 226Ra and 228Ra ranged from 9.39x10-14 µgkg-1d-1 to 181.01x10-14 µgkg-1d-1 with a mean of 100.06x10-14 µgkg-1d-1 and 4.82x10-16 µgkg-1d-1 to 80.70x10-16 µgkg-1d-1 with a mean of 40.90x10-16 µgkg-1d-1 respectively. The hazard quotient (HQ) for 226Ra and 228Ra ranged from 8.38x10-14 to 161.61x10-14 with a mean of 89.33x10-14 and 4.30x10-16 to 70.09x10-16 with a mean of 36.50x10-16 respectively. Radiological hazard indicator of radium is of concern in these river water samples.

Age-dependent dose assessment of uranium intake from bottled water in Punjab state, India

Abstract Uranium, both a radioactive material and a heavy metal, poses a health risk due to its radiological properties and chemical toxicity. In the present study, uranium concentration and relative age-dependent effective dose have been measured in 27 commercial brands of bottled waters collected randomly from different districts of Punjab, India. Uranium concentration varied from 0.19 to 9.29 μg l−1 with a mean value of 1.58 μg l−1, a standard deviation of 1.95 μg l−1 and a median of 0.82 μg l−1. Uranium concentrations in all the samples were found to be lower than the World Health Organization (WHO) and U.S. Environmental Protection Agency (USEPA) prescribed limit of 30 μg l−1 and AERB India proposed a radiological based limit of 60 μg l−1. Based on permissible limits, all the samples were suitable for human consumption. The annual effective dose was determined by taking the recommended water intake values of different age groups. The mean annual effective dose for all age groups was well within the International Commission on Radiological Protection (ICRP) recommended reference dose level of 1 mSv y−1. The highest dose was calculated for infants, which makes them the most crucial group of the population.

Natural radioactivity measurements and age-dependent dose assessment in groundwater from Al-Zulfi, Al-Qassim and Al-Majmaah regions, Saudi Arabia

In this study, the levels of natural radioactivity in the groundwater samples collected from 26 different locations in Al-Zulfi, Al-Qassim and Al-Majmaah regions were determined. The estimated average values of 226Ra, 228Ra, 40K, gross α and gross β activities in the samples were 0.87 Bq L−1, 1.33 Bq L−1, 4.22 Bq L−1, 36.82 mBq L−1 and 831.91 mBq L−1, respectively. We found that age-dependent effective ingestion dose from radionuclides in all samples were higher than WHO recommended levels of 0.1 µSv y−1 for adults 0.2 µSv y−1 for children and 0.26 µSv y−1 for infants while 20 sampling locations have age-dependent effective dose equivalent from β contributors were higher than WHO recommended level of 0.1 mSv y−1.

Assessment of 226Ra age-dependent dose from water intake

The radioactivity in canal and ground waters collected in a 2-year long observation from the vicinity of the Rare Earth Research and Development Center (RRDC), Phathumthani Province, Thailand, was measured in order to determine the concentration of 226Ra and to estimate the age-dependent effective dose to humans due to consumption. 226Ra activities in both canal and ground waters were well below the WHO guidance level for drinking water quality of 1 Bq L −1. The highest 226Ra effective doses per year were found for infants and teens. However, the observed levels of calculated 226Ra effective doses for all age groups in both canal and ground waters show satisfactory low values (less than 15 μSv yr −1). These values are acceptable in accordance with the WHO recommended reference dose level of 100 μSv yr −1 from water intake of 2 L day −1.

Effective dose equivalent and effective dose for some selected radiopharmaceuticals

The ratios of effective dose to effective dose equivalent in adults have been calculated for all 206 radiopharmaceuticals given in ICRP publication 53. Of 48 cases where the ratios were found to be greater than unity, 10 radiopharmaceuticals that have the highest values of the ratios were chosen for the study. Values of the ratio varied from 1.47 to 2.00 with one exception where it was 35.19 (for krypton-91m). The effective dose coefficients were also computed by the modified approach. For non-radioiodinated radiopharmaceuticals, values of the ratio were around . Using the modified approach of calculation, age dependent effective dose coefficients have also been estimated. It is seen that in cases where the thyroid contributes maximum to the effective dose, its percentage contribution does not change with age. However, when the maximum contribution to the effective dose comes from bone marrow its percentage contribution goes on decreasing progressively as age increases.

Organ Doses and Effective Dose as a Function of Organ Depths under Body Surface for External Photon Exposure.

A simplified method in which the equivalent doses in tissue or organs and effective dose for external photon exposure according to the ICRP 1990 Recommendations could be approximated by a single empirical expression is proposed. In this method, the position of an organ is assumed to be the main factor that determine its dose for external photon irradiation. Many organ depths with different body size for ages 1, 5, 10 years and adults were determined using the cross-sections of mathematical organ descriptions, and effective depth for approximating effective dose was obtained with the organ depths assigned to tissue weighting factors.Compared with the precised data for adults by the Monte Carlo method, the simple expression gives good approximates for most of deep organs and effective dose within about 20% except some organs, especially for lateral geometry. It was found that irradiation geometry affects the variations in age-dependent effective dose, and that the effective depths for ages 1, 5, 10 years, normalized to the adults depth, are directly proportional to the cubic root of the body weight. The usefulness of the concept of effective depth was also discussed with regard to the specified point of effective does in the body, obtained from the combination of the depths for the three typical geometries.

Estimation of age-dependent internal dose from radiopharmaceuticals

The age-dependence of the radiation dose absorbed in a target organ or the total body is determined by the mass, size, shape and separation of the organs as well as by the metabolic behaviour of the radionuclide compound. Using values of the specific absorbed dose for adults, the age-dependent effective dose equivalents for 28 radiopharmaceuticals (62 radionuclides) were calculated by modifying the above mentioned values, considering radiation type, organ mass and source-target separation. From the results, the currently used mathematical models for the modification of values of specific absorbed doses in the adult prove to be of sufficient accuracy. In comparison with the few available values calculated by Monte Carlo-techniques, the authors' method overestimates the specific absorbed fractions by a factor of four in the least favourable cases. For practical radionuclide dose estimates, these deviations are of minor importance as long as the availability of reliable information on the metabolic behaviour of radionuclide compounds and radiopharmaceuticals as a function of age is extremely limited. Considering, however, both the parenteral administration and the short half-life of radionuclides used in paediatric nuclear medicine, this uncertainty in regard to the gastrointestinal absorption and the biological half-lives is of little consequence for the results of absorbed dose calculations.