Within the framework of the Protection of the Environment programme of the JRC-Ispra of the European Community, research on trace metal exposure and health effects is concerned primarily with the toxicological assessment of present levels of trace metals in the tissues of exposed and unexposed populations. Main activities are: (1) microdetermination of trace elements in human tissues in order to generate an accurate and reliable data base on the levels and biochemical forms of trace metals in differently exposed humans; (2) metabolism and biochemical mechanisms involving trace metals to assess the toxicological significance of the current levels of the elements in the human body. Few selected applications related to the different steps of the biochemical toxicology research are shown. They concern the long-term behaviour of trace metals at the target tissues of laboratory animals, the biological monitoring of vanadium in workers during maintenance operations at an oil fired power plant for energy production, and the biochemical mechanism of methylation of arsenic in vivo.
The retention of different radio-ions on columns of eleven ionic precipitates from different acid media was studied, in view
of possible applications for radiochemical separations. The results of about 2,000 adsorption experiments, carried out in
a standardized way, are presented schematically in periodic tables.
The definition of dose-response relationships in man is the essential requisite to set scientifically health protection standards
for the evaluation of a safe level exposure of humans to heavy metals. The derivation of these relationships requires sequential
multidisciplinary informations including data on metabolic patterns and biochemical effects in mammals. Unfortunately, sufficient
data are not available to establish dose-response curves expecially in long term-low level exposure conditions and a need
exists to gather such informations for each metal on absorption, distribution and excretion in laboratory animals and humans.
This paper: (1) discuss main problems related to the use of NAA in metallobiochemistry of present levels of trace elements;
(2) report data on the current applications of NAA in metallobiochemistry in relation to the work carried out in the context
of a project Heavy Metal Pollution of CEC JRC—Ispra. Applications deal with in vivo studies on laboratory animals, in vitro
studies on biochemical systems and experiments on tissues of human origin; (3) discuss the perspectives of the use of the
nuclear techniques in the environmental toxicology.
Radiochemical neutron activation analysis has been developed for the determination of arsenic down to 0.1 ng in the tissues
of 5 month old rabbits and in the diet to which animals were exposed. Much effort was devoted to study all possible interferences
and contaminations. The application of NAA to metabolic studies in laboratory animals exposed to present environmental levels
of arsenic shows marked differences between the concentrations of the element in the tissues of rats and rabbits, suggesting
that arsenic follows different metabolic pathways in these animals.
The presence of large quantities of32P in neutron activated biological specimens is often a limiting factor in the direct application of γ-ray spectroscopy. A
technique for the selective removal of phosphates in neutron activated specimens is described. The technique is based on the
adsorption of phosphates on chromatographic grade alumina. The adsorption selectivity was studied by determining the behaviour
of 49 ions when submitted to the procedure for phosphate removal. A few applications are reported as examples.
Trace element analysis has been carried out on standard biological reference samples such as bovine liver, orchard and tomato
leaves. Computer aided instrumental neutron activation analysis and, in some cases, preliminary chemical group separation
followed by NAA were used. For Ca, Mg, Ni and Si special chemical separation and Cerenkov counting were applied. *** DIRECT
SUPPORT *** A1353068 00003
Authors:E. Sabbioni, R. Pietra, J. Edel and L. Goetz
In order to prepare scientifically accurate health protection criteria documents for trace metals integrated multidisciplinary research is necessary. In particular, the rational for structuring the documents should be based primarily on the two major questions of exposure and response. Unfortunately, in a majority of cases there is a paucity of relevant data to the establishment of dose-effect relationships. This work intends to show the role that neutron activation analysis and radiotracers with very high specific radioactivity have in solving problems relevant for establishing dose-effect relationships for trace metals. Typical applications in the different research areas involved in the preparation of the protection criteria, from source and exposure to levels and forms of trace metals in humans, are presented.
Authors:M. Gallorini, E. Orvini, L. Goetz, R. Pietra and E. Sabbioni
A pyrolysis-neutron activation analysis (NAA) procedure has been developed and applied to the speciation of arsenic in solid biological samples. The method involves the retention of the inorganic arsenic in the pyrolysis boat by the addition of NaOH, the volatilization and trapping of the organic arsenic on a cation exchange resin and the subsequent NAA of the resin for the determination of the trapped arsenic. The method, developed with the aid of radiochemically labelled arsenic compounds, has been applied to the determination of the ratio of inorganic to organic arsenic species in commercical shrimps as well as in NBS standard reference materials such as oysters and orchard leaves. The results show different relative amounts of inorganic arsenic content in the samples analysed. In the shrings the fraction of inorganic arsenic was of the order of 20%, in the oysters the inorganic arsenic consfituted 60% of the total arsenic concentration while in the samples of vegetable origin more than 98% of the arsenic was of inorganic nature.
Authors:R. Pietra, E. Sabbioni, M. Gallorini and E. Orvini
Twenty-two radiochemical separation procedures for neutron activation analysis (NAA) of environmental and biological samples are presented. They are currently applied in the context of trace metal research related to the protection of the environment and human health. The radiochemical procedures are related to the separations of the elements into groups which allow the determination of up to 50 elements in each sample or to specific separations for single elements. The experience gained in the application of these radiochemical separations over more than ten years allows us to consider them as reliable for sensitive determinations of trace metals in environmental and biological samples.
Authors:G. Guzzi, R. Pietra, E. Sabbioni and F. Girardi
Cerenkov counting efficiencies for a large number of radionuclides formed by (n, γ) reactions and used in the field of activation
analysis have been obtained by two different experimental procedures. A comparison between the Cerenkov counting technique
and scintillation low-resolution gamma-ray spectrometry is also presented. Results are summarized in tables and briefly discussed.