H. S. Dang

Distribution of arsenic in human tissues and milk

Using neutron activation followed by radiochemical separations, the arsenic contents of various human tissues and milk were determined. The reliability of analysis was established by analysing a number of standard reference materials. The concentrations in different human tissues range from 1.6 ng As/g (fresh weight) in kidneys to 2140 ng As/g in hair. The mean arsenic levels are compared with those reported from other countries.

Distribution of thorium in human tissues

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).

Thorium in man and environment uptake and clearance

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 μg (range 0.8–4.3 μg·d−1). The estimated intake through drinking water and inhalation comes out to be 0.03 and 0.02 μg 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 μg/kg and 0.2–9.0 μg/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 μg/kg, range 31.4–85.5 μg/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.

Daily intake of uranium by urban indian population

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 μg which is much larger than that from drinking water and air, at 0.09 and 0.01 μg, 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 μg 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.

Breast feeding: Mo, As, Mn, Zn and Cu concentrations in milk of economically poor Indian tribal and urban women☆

The breast milk of 86 economically poor Indian women was analysed by neutron activation analyses for Mo, As, Mn, Zn, and Cu concentrations. The colostrum of 10 tribal women contained 0.27 microgram Cu/g, 2.1 micrograms Zn/g, 19.9 ng Mn/g, 0.73 ng As/g and 5.4 ng Mo/g, whereas 19 urban women had corresponding concentrations of 0.91 microgram Cu/g, 7.3 micrograms Zn/g, 15.3 ng Mn/g, 0.5 ng As/g and 15.3 ng Mo/g. A survey of mature milk between 1 and 6 months, 6 and 12 months and 1 and 2.5 years indicated decreasing concentrations of Zn and Mo, but increasing Mn concentrations as the post-partum period progressed. Malnourished infants received breast milk containing less Cu, Zn and Mn than those who were better nourished and of the same age group. The results, therefore, imply the necessity of supplementing breast feeds in the economically poorer groups.

Concentrations of four essential trace elements in breast milk of mothers from two socio-economic groups: preliminary observations.

Concentrations are reported for Cu, Mn, Mo and Zn in human milk samples obtained from mothers belonging to low and middle per capita family income groups. The trace element levels in milk of both groups are compared for samples obtained at two stages, viz. 3-5 days and 4-6 weeks post partum. Although the Mn level during the first stage appears to be lower in samples from the low income group, the difference is not statistically significantly (p less than or equal to 0.01). However, at 4-6 weeks post partum, Zn is significantly lower (p less than or equal to 0.01) in milk of mothers belonging to this group.

A sequential multielement separation scheme for determination of As, Mn, Mo, Cu and Zn in human milk by neutron activation analysis

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.

Simultaneous determination of232Th and238U in biological samples. Application to the estimation of their daily intake through diet

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.

Analytical Quality Assurance Procedures Developed for the IAEA's Reference Asian Man Project (Phase 2)

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.

Daily requirements of Fe, Co and Se during infancy

The daily intakes of trace elements by infants showing optimal pattern of growth are used as the basis to estimate the requirements of Fe, Co and Se during infancy. Since milk is the only food and source of nutrition in the first few months of life, the requirements of these elements are calculated from their average concentrations in human milk and the volume of milk required to supply sufficient amount of energy for maintenance and healthy growth of infants. The concentrations of the three elements in human milk were determined, using the technique of neutron activation followed by radiochemical separation.