Radiation and Environmental Biophysics

Jung, Horst

doi: 10.1007/s004110050035pmid: N/A

Feychting, M.

doi: 10.1007/s004110050036pmid: 9008000

The relationship between occupational exposure to extremely low-frequency electromagnetic fields and adult leukaemia has been studied extensively during the last decade. The first studies were based on crude exposure assessments, estimated through job titles, with no or only limited control of confounding factors. The results were often inconsistent, indicating no effects in about 50% of the studies, while the other half showed only small to moderate effects. Concern has been raised that crude exposure-assessment methods might have diluted the effect estimates, and that improvement of the methods used for exposure assessment would result in more consistent associations. The present review emphasises the latest studies with considerably improved exposure assessments, as well as the control of confounding factors. Results from studies where exposure was assessed through measurements of the magnetic fields at the workplace are still inconsistent. These studies provide some support for the hypothesis of an association between magnetic field exposure and adult leukaemia, especially for chronic lymphocytic leukaemia, but inconsistencies between and within studies weaken the evidence. The lack of consistency regarding the type of leukaemia associated with magnetic field exposure might be explained by differences between the study designs or the populations studied, but based on the existing evidence, no firm conclusions can be drawn.

Rochedo, E. R. R.; Conti, L. F. C.; Paretzke, H. G.

doi: 10.1007/s004110050037pmid: 9008001

The structure and mathematical model of PARATI, a detailed computer programme developed for the assessment of the radiological consequences of an accidental contamination of urban areas, is described with respect to the scenarios used for the estimation of exposure fields in a village or town, the models for the initial and secondary contamination with the radionuclide 137Cs, the concepts for calculating the resulting radiation exposures and the changes with time of the contamination and radiation fields. Kerma rates at various locations in tropical urban areas are given, and the contribution of different contaminated surfaces to these rates after dry or wet deposition are discussed.

Chen, Jing; Nekolla, Elke; Kellerer, Albrecht M.

doi: 10.1007/s004110050038pmid: 9008002

The objective of this study was the computation of microdosimetric functions and quantities for sparsely ionizing radiations. The calculations are performed on simulated electron tracks generated by Monte-Carlo techniques. Ten different radiations of biomedical interest are considered. The comparison of radiation qualities shows marked differences between these sparsely ionizing radiations. The microdosimetric data are represented graphically for use in radiation biology and in clinical applications.

Müller, W.-U.; Heckeley, N.; Streffer, C.

doi: 10.1007/s004110050039pmid: 9008003

One-cell mouse embryos were exposed to either 3H-thymidine (100 or 200 kBq/ml) or 3H-arginine (2.5 to 50 kBq/ml) for 2 h either in G1, S or G2 phase. 3H-Arginine affected embryonic development and cell proliferation in an activity-dependent way irrespective of the cell cycle stage exposed, whereas 3H-thymidine was effective only at higher activities and only after exposure during S phase.

Lyng, Fiona M.; O'Reilly, Sandra; Cottell, David C.; Seymour, Colin B.; Mothersill, C.

doi: 10.1007/s004110050040pmid: 9008004

The phenomenon of delayed heritable lethal damage (often referred to as ``lethal mutations'') in the progeny of cells which survive irradiation is now well established, but little is known of the mechanism by which this cell death occurs. Current theories suggest a generalised genomic instability affecting all cells which leads to the production of some mutations which are lethal, or alternatively that a lethal mutation gene is activated, mutated or induced by radiation and leads to persistent and random cell death at high levels in the progeny. The aim of this study was to look at the morphology of progeny of irradiated cells at various times after irradiation to establish how widespread morphological abnormalities were in the population and whether there was any evidence that such abnormalities were clonal. Using two different cell lines, the results showed that morphological evidence possibly suggestive of apoptosis occurred in the cultures after all doses of radiation and up to 45 cell doublings after exposure. There was no evidence of a decrease in the numbers of damaged or dead cells in colonies with number of divisions after irradiation, or with decreasing original radiation dose. There was a significant dose-dependent increase in the number of cells with microvilli for both cell lines. The dose-dependency of this effect did not change with number of divisions after irradiation. It is clear that morphological evidence of cellular damage persists for several generations after the initial exposure. The effects are widespread in the cell population, and their constancy over time argues strongly for a general instability and against a clonal mechanism, since clonal descendants should die out and leave undamaged survivors. The lack of evidence for necrosis or senescence together with many morphological changes in the cultures suggestive of apoptosis could indicate an active mechanism of cell death. It is concluded that survivor populations of irradiated cells from two widely different mammalian cell lines demonstrate an altered phenotype including gross morphological changes. These result in a higher probability that cell division will fail to yield two healthy progeny.

Ben-Amotz, A.; Rachmilevich, Boris; Greenberg, Simon; Sela, Mordechai; Weshler, Zeev

doi: 10.1007/s004110050041pmid: 9008005

β-Carotene and other carotenoids are reported to be potent free radical quenchers, singlet oxygen scavengers, and lipid antioxidants. Whole-body irradiation is known to cause an immunosuppression effect in mammals through the possible initiation and production of reactive oxygen species. We decided to test the possible antioxidative effect against whole-body irradiation of a natural β-carotene, composed of equal amounts of the all-trans and 9-cis isomers, obtained from the unicellular alga Dunaliella bardawil. Rats were fed on ground commercial food enriched with natural β-carotene (50 mg/kg diet). On completion of 1 week with β-carotene, the rats were exposed to a single dose of 4 Gy whole-body irradiation, after which their livers and blood were removed for β-carotene and retinol analysis in comparison with control livers of animals irradiated or not, or supplemented with β-carotene after irradiation. A normal increase in body weight with no ill effects was noted in the groups of rats whose diet was supplemented by β-carotene before and after irradiation, compared with the reduction in the specific growth rate in the group of rats irradiated without β-carotene. Liver β-carotene and retinol decreased significantly after irradiation compared with the rats which were not irradiated. This decrease was not shown in rats fed β-carotene prior to irradiation, and the effect of irradiation was partially cured by supplementation with β-carotene after irradiation. High-pressure liquid chromatography (HPLC) analysis of the irradiated animals showed a selective decline in 9-cis β-carotene and in retinol over all-trans β-carotene and retinyl esters. These results suggest that 9-cis β-carotene and retinol protect in vivo against the cellular damage by free radicals induced after whole-body irradiation.

Berroud, A.; Roy, A. Le; Voisin, P.

doi: 10.1007/s004110050042pmid: 9008006

Effects of ionizing radiation on biological membranes include alterations in membrane proteins, peroxidation of unsaturated lipids accompanied by perturbations of the lipid bilayer polarity. We have measured radiation-induced membrane modifications using two fluorescent lipophilic membrane probes (TMA-DPH and DPH) by the technique of fluorescence polarization on two different cell lines (Chinese hamster ovary CHO-K1 and lymphoblastic RPMI 1788 cell lines). γ-Irradiation was performed using a 60Co source with dose rates of 0.1 and 1 Gy/min for final doses of 4 and 8 Gy. Irradiation induced a decrease of fluorescence intensity and anisotropy of DPH and TMA-DPH in both cell lines, which was dose-dependent but varied inversely with the dose rate. Moreover, the fluorescence anisotropy measured in lymphoblastic cells using TMA-DPH was found to decrease as early as 1 h after irradiation, and remained significantly lower 24 h after irradiation. This study indicates that some alterations of membrane fluidity are observed after low irradiation doses and for some time thereafter. The changes in membrane fluidity might reflect oxidative damage, thus confirming a radiation-induced fluidization of biological membranes. The use of membrane fluidity changes as a potential biological indicator of radiation injury is discussed.

Hillmann, U.; Schimmack, W.; Jacob, P.; Bunzl, K.

doi: 10.1007/s004110050043pmid: 9008007

Several years after the deposition of fallout radiocesium, the maximal activity of this radionuclide will not remain at the soil surface but be found rather in deeper layers. In order to estimate the total radiocesium contamination of a large area and the resulting γ-dose rate by in-situ spectrometry, it is necessary to approximate the vertical distribution of this radionuclide by an analytical function. Observations at ten undisturbed grassland soils in Bavaria, Germany, show that the resulting depth distributions can be approximated closely by a three-parameter Lorentz function. This function characterises the observed distributions in all three critical sections, i.e. the surface layer, the distribution around the maximal concentration, and the tail at greater depth. It is also shown that the observed total activity per unit area of the soil due to 137Cs agrees very well with the corresponding value obtained from the integrated Lorentz function. The two coefficients of the Lorentz function, which characterise the location (depth) and width of the maximum in the activity distribution, are shown to be correlated. In part II of this study, it will be shown how the parameters of the Lorentz function can also be obtained by in-situ γ-ray spectrometry. As a result, it is possible to use in-situ γ-ray spectrometry to obtain the total 137Cs activity per unit area also for sites where the vertical distribution of this radionuclide in the soil is no longer exponential.

Romanyukha, A. A.; Degteva, M. O.; Kozheurov, V. P.; Wieser, A.; Jacob, P.; Ignatiev, E. A.; Vorobiova, M. I.

doi: 10.1007/s004110050044pmid: 9008008

During 1949–1956, about 76 × 106 m3 of radioactive liquid waste containing a total activity of 1017 Bq was discharged into the Techa River by the first Russian industrial nuclear facility Mayak. As a consequence, the population living in the river valley received considerable internal and external radiation doses. The results of a first application of electron paramagnetic resonance (EPR) of tooth enamel for a retrospective individual dose evaluation of the residents of the Techa riverside are presented. Three main contributions to the dose absorbed in tooth enamel have been considered: external exposure mainly from the Techa River sediments, internal exposure mainly due to 90Sr; and background radiation including all other sources of exposure except the Techa River. The teeth of 86 inhabitants of the town Kamensk-Uralskii were analysed to determine the age-dependent contribution of the background radiation to the enamel dose. For 22 residents of the middle and lower Techa riverside, measurements of the 90Sr whole-body content and EPR measurements of the absorbed dose in enamel were used to establish a correlation between these two quantities. Finally, absorbed doses in the enamel of five residents of the upper Techa riverside were determined by the EPR method. Contributions of the background radiation and the internal 90Sr contamination were subtracted to determine the external exposure of the residents.