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PubMed1992

The accident at Chernobyl and trisomy 21 in Finland.

Our objective was to explore whether the radiation fallout in Finland after the accident at the Chernobyl nuclear power plant in April 1986 led to an increased incidence of trisomy 21. In this geographic and temporal cohort study, the country was divided into three zones according to the amounts of radioactive fallout and internal radiation caused by two cesium isotopes. The 518 cytologically verified cases of trisomy 21 were divided into a control group (conceived before the accident), and a study group of children whose expected dates of birth were in the post-accident years 1987-1988, i.e., pregnancies commenced after May 1986. The cases were also divided into three subgroups according to the zones of radiation. There were no significant differences in prevalence of trisomy 21 between the control and study groups nor between the three zones in spite of the significant differences in the levels of radiation and in the body burden that prevailed throughout the study period. Power estimates showed that in the two zones of lower radiation, an increase of 0.5% in the prevalence would have been detected with a power of 0.85, and in the somewhat smaller zone of the highest radiation, with a power of 0.70. The study lends no further support to the view that the low radiation fallout in western Europe would have been causally associated with trisomy 21.

Accidents↗
PubMed1992

Transfer factor of 131I from the fallout to human thyroid dose equivalent after the Chernobyl accident.

A similar pattern of variation with time in observed maxima of daily dose equivalent rates in human thyroids (TD - microSv.d-1) and of daily fallout radioactivities (FR - kBq.m-2) has been found after the Chernobyl accident. An estimate of the time-lag between the maxima in TD lines and the preceding FR peaks was made of about seven days for adult and nine days for juveniles. Applying this time-lag it was possible to estimate transfer factors from the fallout to thyroid dose equivalent: the highest estimated values were 221 microSv/kBq.m-2 for adult and 641 microSv/kBq.m-2 for juvenile thyroids. These values differ from those published by UNSCEAR (United Nations 1988), which have been calculated for various regions of Czechoslovakia, from ingestion and inhalation intake estimates. A broad variation of transfer factor values could be expected to result from such transfer calculations using ingestion and inhalation estimates. The findings also support the concept of a need for prolonged iodine prophylaxy after emissions of radioiodine into the environment.

Accidents↗
PubMed1992

Investigations of radiocaesium in the natural terrestrial environment in Norway following the Chernobyl accident.

Radioactive fallout from the Chernobyl accident affected parts of central Norway to a considerable extent, in particular the 134Cs+137Cs deposition had a significant impact on the natural environment. When this became apparent, a comprehensive radioecological research programme was initiated in order to study the behaviour of radiocaesium in boreal and alpine ecosystems, with emphasis on food-chains leading to exposure of species used for human consumption, i.e., reindeer and freshwater fish. In this paper results from the terrestrial part of this research programme during the period 1986-1990 are presented. The work was mainly confined to the mountain areas of Dovre and Rondane. Parallel studies were performed in eutrophic and strongly oligotrophic communities. The influence of local variations in topography and microclimate on the observed radiocaesium levels in topsoils, lichens and vascular plants was studied in detail. Currently a significant re-distribution of radiocaesium from the originally strongly exposed surfaces to those that were less exposed is observed. In the soil, radiocaesium is strongly retained in the litter and raw humus layers. Current levels in lichens are 1-2 orders of magnitude higher than in vascular plants. This strongly affects the seasonal variation of radiocaesium in reindeer, showing winter maxima of about 5 times higher than the August levels. The radiocaesium levels in reindeer showed a decline of approximately a factor of 3 during the period 1987-1990. Other animal species studied in the programme exhibited substantially lower radiocaesium levels than reindeer, but a considerable interspecies variation was observed.

Accidents↗
PubMed1991

[The perception of the radiation situation and assessment of their own health status by the population living in an area under strict radiation control].

Studies of subjective perception of the radiation situation, self-estimation of the health status by the population, the attitude of the population to the formal information available were carried out in the strong radiation control areas and in the regions not polluted by radioactive fallout. Before the accident 71.6% of the population were not aware of real danger of radiation for health. During the accident and after it, mass media were the main source of information on the consequences of the accident and the effect of radiation (71.1%). 38% of the information was provided by scientists and specialists. 89.6% of the persons interviewed experience anxiety whatever the intelligence available. Only 13.4% of those who live in the areas polluted by radionuclides feel well. The low self-estimation of the health status, the high level of anxiety together with the deficiency of radiation and hygienic intelligence favour the forcing of the social and psychological tension and reduce the effectiveness of the whole complex of measures carried out in the areas polluted with radionuclides.

Accidents↗
PubMed1991

Components of total irradiation dose in Switzerland and their ranges.

The present knowledge about dose components in Switzerland and their ranges is reviewed. Considerable ranges are found for doses induced by radon decay-products and by cosmic and terrestrial radiation. Yearly doses from radon decay-products show average values between about 1 and 20 mSv in different communities and individual values up to about 150 mSv. The reliability of these average values is, however, limited, because radon concentrations have been measured up to now only in a small number of houses, and because corrections of the raw data are necessary, increasing the uncertainty of the results. Doses from terrestrial and cosmic radiation show locally variable values between about 0.5 and 1.5 mSv per year. These doses are mainly derived from outdoor measurements. Therefore, these results also are only of limited use in possible epidemiological applications.

Background Radiation↗
PubMed1978

Biophysical aspects of Am-241 and Pu-241 in the environment.

Most of plutonium released by nuclear explosions is Pu-241 which decays to Am-241. We have studied the deposition of Pu-241 and Am-241 in lichens collected since 1958 in the central part of Sweden (62.3 degrees N, 12. 4 degrees E). Comparative studies with Pu-isotopes, Pu-239 + 240 and Pu-238 were also performed. In 1972 the total accumulated deposition of Pu-241 was 8 mCi/km2 of Pu-239 + 240 1 mCi/km2 and of Am-241 0.2 mCi/km2. About 80% of the Am-241 activity has been formed in situ from decay of Pu-241. The biological mean-residence time for all Pu-isotopes were about 6 years and for Am-241 4 years. The spatial distribution of Am-241 in the lichen carpet is quite different from that of Pu-241. The activity concentrations of Am-241 and Pu-241 have been studied in reindeer liver and bone. The average concentrations found were in liver 0.6 and 40 pCi/kg, in bone 0.2 and 6 pCi per kg for Am-241 and Pu-241 respectively. The activity content of Am-241 and Pu-241 in the Lapps due to their reindeer diet was estimated to be in liver 1.0 E-4 and 1.0 E-2 pCi/kg, in bone (3-9) E-5 and 1.0 E-2 pCi/kg for Am-241 and Pu-241 respectively. The estimated values for the fractions of ingested activity retained were in liver 7 E-6 and 14 E-6, in bone 20 E-6 for Am-241 and Pu-241 respectively. The fraction of ingested activity of Pu retained in reindeer liver is about 2-3 times higher than that of Am.

Americium↗
PubMed1992

Zirconium. An abnormal trace element in biology.

The action of Zirconium (Zr) on biological systems presents an enigma. It is ubiquitous, being present in nature in amounts higher than most trace elements. It is taken up by plants from soil and water and accumulated in certain tissues. The entry into animal systems in vivo is related to the mode of exposure and the concentration in the surrounding environment. Retention is initially in soft tissues and then slowly in the bone. The metal is able to cross the blood brain-barrier and is deposited in the brain and the placental barrier to enter milk. The daily human uptake has been known to be as high as 125 mg. The level of toxicity has been found to be moderately low, both in histological and cytological studies. The toxic effects induced by very high concentrations are nonspecific in nature. Despite the presence and retention in relatively high quantities in biological systems, Zr has not yet been associated with any specific metabolic function. Very little information is available about its interaction with the compounds of the genetical systems, such as nucleic acids. Apparently, the metal is neither an essential nor toxic element in the conventional sense. However, the increasing exposure to this element through its increasing use in new materials and following radioactive fallout, has increased the importance of the study of its effects on living organisms. The tetravalent nature of the ionic state and the high stability of the compounds formed are important factors that need to be considered, as also the accumulation of this element in the brain, reminiscent of the relationship between Al3+ and Alzheimer's disease.

Animals↗
PubMed1991

Down's syndrome in the Lothian region of Scotland--1978 to 1989.

A study of Down's syndrome in Lothian for the years 1978-1989 revealed a significantly higher than expected incidence of cases in 1987. The increased incidence was particularly significant among women aged 35 years or more. The increase could not be attributed to demographic changes on birth rates or to the age distribution of the women concerned. A temporal association between the cluster of cases and the events at Chernobyl in April 1986 was demonstrated. However, according to current understanding, there is no biologically plausible explanation to link the 2 events, given the reported levels of radioactive fallout in the Lothian region, resulting from the Chernobyl disaster. An explanation for the increased incidence of Down's syndrome in 1987 remains outstanding.

Abnormalities, Radiation-Induced↗
PubMed1992

In-situ determination of deposited radionuclide activities: improved method using derived depth distributions from the measured photon spectra.

When applying the standard method of in-situ gamma spectrometry to determine deposited radionuclide activities, an assumption is needed regarding the depth distribution of radionuclides in the ground. The method can be improved by assessing, from information contained in the spectrum, the attenuation of the radiation by the soil and vegetation. By comparing the count rates of the x ray and the gamma-ray lines of its daughter nuclide 137mBa, the 137Cs activity per area can be determined. The range of applicability of the method is discussed by means of an uncertainty analysis, and the method is applied to post-Chernobyl measurements. A comparison with the results of the standard method of in-situ spectrometry demonstrates the progress achieved by the proposed method. Nevertheless, the method still has some shortcomings for the peak analysis that could be improved by better detector resolution or better computer software.

Cesium Radioisotopes↗