Nicholas Priest

The biological behaviour and bioavailability of aluminium in man, with special reference to studies employing aluminium-26 as a tracer: review and study update

Until 1990 biokinetic studies of aluminium metabolism and biokinetics in man and other animals had been substantially inhibited by analytical and practical difficulties. Of these, the most important are the difficulties in differentiating between administered aluminium and endogenous aluminium-especially in body fluids and excreta and the problems associated with the contamination of samples with environmental aluminium. As a consequence of these it was not possible to detect small, residual body burdens of the metal following experimental administrations. Consequently, many believed aluminium to be quantitatively excreted within a short time of uptake in all, but renal-failure patients. Nevertheless, residual aluminium deposits in a number of different organs and tissues had been detected in normal subjects using a variety of techniques, including histochemical staining methods. In order to understand the origins and kinetics of such residual aluminium deposits new approaches were required. One approach taken was to employ the radioisotope (67)Ga as a surrogate, but this approach has been shown to be flawed-a consequence of the different biological behaviours of aluminium and gallium. A second arose from the availability, in about 1990, of both (26)Al-a rare and expensive isotope of aluminium-and accelerator mass spectrometry for the ultra-trace detection of this isotope. Using these techniques the basic features of aluminium biokinetics and bioavailability have been unravelled. It is now clear that some aluminium is retained in the body-most probably within the skeleton, and that some deposits in the brain. However, most aluminium that enters the blood is excreted in urine within a few days or weeks and the gastrointestinal tract provides an effective barrier to aluminium uptake. Aspects of the biokinetics and bioavailability of aluminium are described below.

Minimum requirements for reporting analytical data for environmental samples.(IUPAC Technical Report).

In view of the significance of environmental analytical data, it is essential that the quality of both sampling strategy and analysis be assured and that procedures used, as well as all relevant additional information, are reported. There is a minimum level of information required in order to guarantee the fitness-for-use of the data. Emanating from discussions on the fundamental problems of the analysis of environmental samples for chemical or biological contaminants, a general guidance is given regarding the minimum information that should be provided to adequately describe the sampling strategy, method of sampling, sample properties, handling between sampling and analysis (including storage conditions, pretreatments, homogenization, subsampling), and the analytical methodology (including calculation and validation procedures). Special attention and specific guidance are given for the environmental compartments soil, pore water, groundwater, inland surface water, sediment, seawater, precipitation water, and air.

A biokinetic model to describe the distribution and excretion of arsenic by man following acute and chronic intakes of arsenite/arsenate compounds by ingestion.

An empirical mathematical model, comprising 17 compartments, has been produced to describe the biokinetics of ingested inorganic arsenic (As) in man — required to interpret bioassay data and to predict As tissue concentrations resulting from acute and chronic intakes of inorganic As. The rate constants used to describe the bi-directional transfer of As between compartments were chosen to result in model outcomes that match published data on the distribution of As in tissues and on the retention and excretion of radioisotopes of As administered to human subjects. The model was deployed in acute and chronic intake modes to produce predictions of tissue concentrations and excretion levels. Under conditions of chronic daily intake (1 μg d-1) for 50 years predicted final tissue concentrations vary by a factor of ∼2. Highest concentrations are predicted to occur in skin and bone (∼230ng kg-1). Tissue concentrations in all tissues other than bone are predicted to reach equilibrium after ∼100 days, and at this time, the amount of As excreted in urine has also reached approximate equilibrium at 79% of the daily dietary intake. This level then remains relatively constant unless intake ceases when tissue levels of As fall rapidly. Data on organic and inorganic As concentrations in urine were used to predict inorganic As intake and average tissue content for the USA population. Predicted tissue concentrations ranged from 2.3 μg kg -1 in skin to 1.1 μg kg-1 in muscle for an average inorganic As intake of 9.3 μg d-1.

Environmental factors influencing the prevalence of respiratory diseases and allergies among schoolchildren in Chiang Mai, Thailand

Air quality has seriously deteriorated as a consequence of population growth and urbanisation and respiratory diseases increased among residents of urban areas in Chiang Mai Province, Thailand. An International Study of Asthma and Allergies in Childhood (ISAAC) study was conducted among children attending schools located in the selected sites to assess the potential impacts of air pollution on health. The results showed that the prevalence of asthma was similar in all of the schools (approximately 5%; p = 1.000) but that the prevalence of rhinitis [24.3% (CI = 19.4–30.1) vs. 15.7% (CI = 10.3–23.0); p = 0.029] and atopic dermatitis [12.5% (CI = 9.1–16.8) vs. 7.2% (CI = 3.7–12.6); p = 0.093)] was higher in the urban schools, which were exposed to more pollution. Logistic regression analysis identified factors that may be involved, including air pollution, some components of the diet and contact with animals.

Human biokinetics of injected bismuth-207

A healthy male volunteer received an intravenous injection of 207Bi as citrate. Levels of the tracer in blood and in excretion samples, and its retention and distribution within the body, were investigated by appropriate radioactivity measurements. Levels in blood fell very rapidly, with only 1% of the injection remaining at 7 h and only ca. 0.1% at 18 days. There was rapid initial excretion, with 55% lost during the first 47 h, principally in urine; however, longer-term losses were much slower and 0.6% remained in the body at 924 days, when the contemporary rate of loss implied a half-life of 1.9 years. Integration of the retention pattern suggested that steady exposure to bismuth compounds could lead ultimately to a body content of 24 times the daily systemic uptake. The largest organ deposit was in the liver, which after 3 days contained ca. 60% of the contemporary whole body content, consistent with reports of hepatotoxicity. These findings differ markedly from the metabolic model for bismuth proposed by the International Commission on Radiological Protection, which envisages a terminal half-life in the body of only 5 days and kidney as the site of highest deposition.

Ecological Impacts of Large–Scale War Preparations: Semipalatinsk Test Site, Kazakhstan

Development and testing of weapons of mass destruction may result in irreversible environmental changes resulting in high social risk and negative effects on human health. The former Semipalatinsk nuclear test site (STS) is a sorrowful monument of the Cold War. Nuclear tests at STS inflicted numerous economic, social and ecological problems on Kazakhstan. In the framework of the NATO “Science for Peace Program,” about 1,400 km2 of the STS have been investigated. According to the results of the Semirad project, the most contaminated area of the southeastern part of the STS is two craters, Telkem-1 and Telkem-2, formed by nuclear explosions. These craters are contaminated with the fission products, cesium-137 and strontium-90, and with components of nuclear fuel, plutonium-239 and americium-241, and the activation product, europium-154. The considerable migration of radionuclides in the 40 years since the tests were conducted was not detected. The calculated effective dose for adults from radionuclides at the Telkem craters is approximately 7 mSv. In the northern part of the STS (Semirad 2 project) the most contaminated sites are located close to the area of radiological dispersion device tests. Annual effective doses from plutonium-239 and strontium-90 can reach over 8 mSv. There is no possibility to detect the dose, largely from micron-sized “hot particles” of high radioactivity spread across the STS territory. The STS is a unique scientific preserve where scientists from all over the world are welcome to conduct research. The Republic of Kazakhstan abandoned its nuclear arsenal and opened the path to the international community to a world free of nuclear weapons.

First-generation offspring of male mice exposed to 239Pu-citrate show no evidence of leukaemia or life shortening

The aim was to test whether male mice injected with 239Pu citrate transmit induced mutations that lead to specific causes of death, decrease longevity or both. Male CBA/Ca mice injected with 239Pu citrate solutions at nominal activities of 6 and 60 Bq g – 1 were mated to females (same strain) 54 – 68 days later. Absorbed doses to the testes were estimated to be approximately 0.3 and 4.0 cGy. Control males were injected with carrier only. Longevity was evaluated. All 1807 progeny were given detailed necropsies. Haematological analysis was used in an attempt to identify leukaemia. Male progeny from both treated groups lived significantly longer than those from the control, and there was no difference in longevity between the two treatments. No evidence was found of the induction of leukaemia or of any of the numerous probable causes of death. Although numerous significant differences were found in the many comparisons made between the three groups, there was no clear indication that any harmful effects were associated with paternal preconceptional plutonium exposure. This was in spite of the initial body burden (higher dose) being approximately 2800 times the maximum body burden allowed for workers when this study was initiated.

STRONTIUM-90 CONTAMINATION WITHIN THE SEMIPALATINSK NUCLEAR TEST SITE: RESULTS OF SEMIRAD1 AND SEMIRAD2 PROJECTS - CONTAMINATION LEVELS AND PROJECTED DOSES TO LOCAL POPULATIONS

Analysis of strontium-90 in soils showed that most of the SEMIRAD1 and SEMIRAD2 project areas were little contaminated with this radionuclide indicating that the extensive testing of nuclear devices at the STS (including more than 100 groundlevel, aerial and crater-producing explosions) resulted in little dispersed local contamination by fission products, including strontium-90. However, local strontium-90 contamination produced by the Telkem, crater-producing explosions within the SEMIRAD1 study area was evident at distances less that about 3 km from the explosion sites. Within the craters soil strontium-90 concentrations reached 1 kBq kg -1 . Around the craters strontium-90 was more widely dispersed than fuel-associated radionuclides and evidence exists to suggest that it is much more mobile within the environment. Within the SEMIRAD1 study area strontium-90 levels were also elevated below the path of the fallout plume produced by the testing of the Soviet Unions first H-bomb in 1953. Radiation doses to residents of the SEMIRAD1 study area were calculated using a modified ECOSYS model. These indicated that strontium-90 was a major contributor to dose in the more contaminated regions around Telkem and close to the village of Sarzhal. Annual doses to adult males living close to Telkem were assessed to currently be about 7 mSv, but these were predicted to fall in line with the physical half-life (28.64 years) of strontium-