Beneficial effects of radiation and regulatory policy.

Adaptive and stimulating effects of ionizing radiation occur at near natural doses. This disagrees with linear, no-threshold hypothesis on the dose/effect relationship, which is a basis of the current radiation protection. Vast literature demonstrates that such effects, usually known as hormetic ones, occur at molecular, cellular and population levels, and often result in increase longevity and decreased cancer incidence. Exposure to lower than natural radiation causes deficiency symptoms in protozoa and bacteria. Hormetic effects suggest that the current radiation protection regulations may be too conservative. After the Chernobyl accident, adverse health effects and vast material losses were induced in the former USSR by practical implementation of the ICRP radiation protection recommendations. A revision of the current approach to managing the risks of ionizing radiation is needed for the public interest.

Vertical distribution and flows of lead and natural radionuclides in the atmosphere.

Vertical distributions of radium-226, lead-210, uranium and stable lead were observed in the troposphere and lower stratosphere over Poland at several altitudes between 0 and 15 km in the period 1973-1987. Greatly increased concentrations of stable lead and radium-226 were observed at all altitudes for several years after the Fuego volcano eruption in 1974, and also after the Nevado del Ruiz eruption in 1985. The volcanic eruptions in 1980-1982 contributed to the radium-226 and uranium levels at the higher altitudes. The annual flows of radium-226, lead-210, uranium and stable lead into the global atmosphere, estimated from their long-term average contents in the 0-15 km air layer, are 2.3 x 10(14) Bq, 8.4 x 10(15) Bq, 8.3 x 10(9) g and 3.7 x 10(12) g, respectively. These estimates are similar to those based on concentrations of these nuclides in widely dispersed glaciers in both hemispheres, and on radon-222 exhalation measurements. However, they are higher than estimates based on particulate emissions. The anthropogenic contribution to the total flow of radium-226 into the global atmosphere is approximately 3.7%, for lead-210 0.25%, uranium 17% and stable lead 9.7%.

Heavy metals in human and animal bones from ancient and contemporary France.

The concentrations of Cd, Pb, Zn, Ba, Mg and Ca have been determined in 180 human bones from the last five millenia, and in 22 contemporary and 20000-50000-year-old animal bones. The original concentrations of Cd and Zn in the ancient human bones were not changed by fossilization processes, whereas Pb and Mg tended to migrate out of the bones, and Ba and Ca concentrations increased with the age of the bones. The distribution of metals in the structure of both the ancient and contemporary bones is not uniform, and neglecting this may render it difficult to compare results obtained from different studies. In Europe and Peru in the late Middle Ages the concentration of Pb in human bones increased by one order of magnitude. The high level of Pb persisted in Europe for several centuries and only recently decreased by an order of magnitude. The concentration of Cd has increased in human bones in the 20th century, to about ten times above the pre-industrial level. The concentration of Pb in contemporary cow bones from France is below analytical detection limits, probably due to competition of Pb with Ca and P which are added to cow fodder as mineral additives.

[Chronologic course of the content of lead, cadmium and zinc in human bones in France]. / Evolution chronologique de la teneur en plomb, cadmium et zinc des os chez l'homme en France.

The concentrations of Pb, Cd and Zn have been determined in human bones from the past 5,600 years. During this time the level of Zn in bones was stable. Concentration of Cd was low and stable throughout the ages until it increased recently by an order of magnitude. Concentration of Pb increased by one order of magnitude in the Middle Ages and returned again to a low level in the contemporary population of Paris.

Tritium retention in rat after administration of various doses of tritiated water.

Hooded inbred rats were given subcutaneously HTO doses ranging from 1.8 muCi/g b.w. to 115 muCi/g b.w. Samples of liver, lung, kidney, skin muscle, small and large intestine were taken at 1, 3, and 5 days intervals within 21 days of the experiment. The concentrations of tritium in free water and bound in particular tissues have been determined, and the biological half-lifes (Tb) of tritium were calculated by means of least squares. The biological half-life of free-water tritium varied from 3.6 days in kidney to 4.8 days in muscle for the control group being slightly lower in the groups with higher HTO doses. The retention of tissue-bound tritium varied in each group of animals. Tb values varied from 10.3 days in the large intestine to 85.0 days in the muscle of the control group and were significantly lower at higher HTO doses. This result is opposite to the effect observed after external X-ray irradiation for the same radiation dose level.

Natural radionuclides in industrial and rural soils.

Radium-226, lead-210, uranium and thorium are dispersed in the environment by fly ash emitted by coal fuelled power stations. Concentrations of these nuclides have been determined in fly ash from three power stations and in soils collected in six industrial and twenty rural regions. In industrial areas the concentrations of natural radionuclides, in a 5 cm thick surface soil layer, were found to be higher than in lower layers. With the exception of lead-210 this effect was not observed in rural soils, which contained less of radium-226, uranium and thorium. It was found that the type of coal, or combustion technology, influences the amount of radium-226 dispersed in the environment which is accessible to plants.