Quality assurance (QA) procedures were established to generate reliableresults for a set of trace elements of radiological significance, namely Cs,Sr, Th and U. Special attention was given to design QA procedures by incorporatingboth internal and external analytical quality control (AQC) procedures, sincethe project involved a group of countries working on the same analytical problemunder different conditions. The procedures included (1) use of existing certifiedreference materials (CRMs) to validate analytical methods, (2) generatingreference values in selected CRMs where certified results were not available,(3) preparing a new total diet CRM, (4) adopting the concept of a CentralReference Laboratory (CRL) to harmonize QA efforts, and finally, (5) analysisof 10% of all samples in the project by both the CRL and participant laboratoriesto assess performance of the methods used.
Neutron activation followed by simple radiochemical separation was employed to determine the concentration of thorium (232Th) in different human tissues. The median232Th concentrations (ng/g) in tissues with ranges given in parentheses are lymph nodes: 64.7 (31.4–85.5), lungs: 9.2 (1.5–16.0), hair: 5.2 (2.9–11.0), kidney: 1.7 (0.9–4.0), liver: 0.9 (0.2–4.9) and blood 0.01 (0.006–0.030). The reliability of analysis was tested by analyzing standard reference material Orchard Leaves (US, NBS).
The intake and tissue distribution of thorium (2 3 2Th) was studied in an urban (Bombay) population in India. From the analysis of 16 whole diet samples, the average daily intake through food was found to be 2 g (range 0.8–4.3 g·d–1). The estimated intake through drinking water and inhalation comes out to be 0.03 and 0.02 g per day. From the analysis of human autopsy tissue samples it is observed that the concentration ranges in lungs and bone are 1.5–16 g/kg and 0.2–9.0 g/kg fresh weight respectively. The average urinary concentration is 12 ng/1 (range 7–22 ng/l for 10 samples). Among the different body tissues, pulmonary lymph nodes were found to contain the highest concentration (geometric mean 53.4 g/kg, range 31.4–85.5 g/kg for 6 samples). Analysis of the samples was done by the neutron activation technique. 311.8 keV gamma photons of2 3 3Pa which is the activation product of2 3 2Th, were counted after chemical separation. A 54 cm3 intrinsic Ge detector coupled to 1024-channel analyser was used. Using the average lung content and the daily average intake values of thorium through inhalation, the clearance half-time from lung was estimated.
Rib bone samples of human accident victims were analyzed for thorium. The analysis was carried out using neutron activation technique to determine Th-232. The age of the victims ranged between 6 years and 65 years. The thorium concentration was found to increase with age. The measured concentration ranged from 0.20 ng/g fresh weight at age 6 years to 1.84 ng/g at age 65 years. The arithmetic mean and geometric mean concentrations were found to be 0.54±0.38 ng/g and 0.46x/÷1.8 ng/g (by excluding the outlier high value of 65-year-old individual). These values are much lower in comparison to those reported by earlier workers. Assuming the total skeletal weight as 14.3% of the body weight and taking the average Indian's body weights as 14.5, 38 and 50 kg at ages 5, 15 and >18 years, the estimate of total skeletal thorium was made.A plot of the total skeletal thorium with age groupings 0–10, 10–20... 50–60 years could be fitted into a linear relation with age. However, the deviation of data in 40–50 and 50–60-year age groups was such that the data could also be fitted into a sub-linearly increasing curve. Both the fittings, however, show a considerably lower rate of uptake in bone than that expected from substitution of Indian (Bombay) intake data into the ICRP model of Th metabolism.
A simple method employing neutron activation and radiochemical separation was developed for simultaneous determination of the concentrations of232Th(Th) and238U(U) in biological materials. Using this method, it is possible to detect 0.05 and 0.2 ng of Th and U, respectively, in the samples. This method was applied to determine the daily dietary intake of these two nuclides by the population living in the high background areas of India (Monazite area), where the soil contains very high levels of these two nuclides. The comparison of the daily intakes by the population living in high and normal background areas showed significantly higher intake of these two nuclides by the high background population.
Authors:H. Dang, H. Desai, D. Jaiswal, S. Kayasth, and S. Somasundaram
A simple separation scheme for the analysis of As, Mn, Mo, Cu and Zn using neutron activation is described. It has been checked
using three standard reference materials, A-11 milk powder (IAEA) and bovine liver and orchard leaves (USNBS) and found to
give acceptable results. This scheme was applied for determination of these trace elements in mature human milk samples. The
concentrations of As, Mn, Mo, Cu in samples obtained from two socio-economic groups—low and middle incomes—were not significantly
different. However, Zn levels in samples obtained from the poor income group were significantly lower than in those obtained
from the other group.
Authors:H. Dang, D. Jaiswal, V. Pullat, and U. Mishra
The blood serum is the fluid medium through which most of the minerals are absorbed into the human body and get metabolized. The concentrations of Th in blood serum is in equilibrium with the content of Th in human body and therefore could reflect its content in the body. The daily intake (ingestion and inhalation) and the corresponding concentration of Th in blood serum of a group of subjects living in the high-background (monazite) area of Kerala State were measured and compared with the daily intake and corresponding blood serum concentrations of Th in three other groups of subjects namely: (1) those living in normal background area, (2) administrative staff working in Thorium Plant but not directly exposed to Th and its compounds, and (3) the occupational workers from Thorium Plant working for a time period in the range15–30 years. The Th concentration in the blood serum of subjects from high background area were found to be only marginally higher in comparison to the similar data from normalbackground area, which indicated that internal exposure due to Th to the subjects living in high background is quite low.
Authors:C. Sunta, H. Dang, D. Jaiswal, and S. Soman
Neutron activation followed by a simple radio-chemical separation procedure was employed to determine the concentrations of thorium (232Th) in human blood serum, clot, and urine of normal subjects and three groups of occupationally exposed persons. The thorium concentrations in the blood serum, clot, and urine samples of the exposed groups were distinctly higher than those of the other study groups and were found to increase with increasing occupational length of the persons. Daily urinary excretion is correlated with serum thorium burden and it is estimated that the daily excreted thorium is about 15% of the thorium in the serum pool.
Authors:H. Dang, V. Pullat, D. Jaiswal, M. Parameswaran, and C. Sunta
The daily intake of uranium (238U) by an urban Indian adult population was estimated by the analysis of a duplicate diet, drinking water, and air samples using neutron activation and radio-chemical separation. The uranium intake through food is 0.55 g which is much larger than that from drinking water and air, at 0.09 and 0.01 g, respectively. The total daily dietary intake of uranium, calculated from the concentrations measured in the individual food ingredients and their daily consumption (based on the national survey), is found to be 2.2 g which is a factor of 3.5 higher than that based on a duplicate urban diet. The maximum contribution to the daily intake is found to be from cereals. The lower intake by the urban population is most likely due to their lower food consumption.
Authors:H. Kawamura, R. Parr, H. Dang, W. Tian, R. Barnes, and G. Iyengar
Analytical quality assurance procedures adopted for use in the IAEA Co-ordinated Research Project on Ingestion and Organ Content of Trace Elements of Importance in Radiological Protection are designed to ensure comparability of the analytical results for Cs, I, Sr, Th, U and other elements in human tissues and diets collected and analysed in nine participating countries. The main analytical techniques are NAA and ICP-MS. For sample preparation, all participants are using identical food blenders which have been centrally supplied after testing for contamination. For quality control of the analyses, six NIST SRMs covering a range of matrices with certified and reference values for the elements of interest have been distributed. A new Japanese reference diet material has also been developed. These quality assurance procedures are summarized here and new data are presented for Cs, I, Sr, Th and U in the NIST SRMs.