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Concept of seasonality in the light of the Chernobyl accident.

Seasonality could have a strong influence on the radiological impact of environmental radioactive contamination. Short-lived radionuclides (e.g., 131l) and those that mainly enter the food chain by direct contamination (e.g., 137Cs) are especially important in this context. In particular, the contamination of cereals is influenced by seasonality. For temperate latitudes it is generally true that radioactive contamination during winter, when the fields lie fallow and the domestic animals are stabled, will result in a significantly lower radiological impact than if a similar contamination were to take place in the summer shortly before harvesting. The impact of the Chernobyl accident on the radioactive contamination of human diet was strongly influenced by seasonality.

Accidents↗

Abandoned Rayrock uranium mill tailings in the Northwest Territories: environmental conditions and radiological impact.

Field and laboratory investigations were undertaken of the environment surrounding abandoned U mill tailings at Rayrock, Northwest Territories, Canada, to examine the extent of 226Ra and U contamination. Samples of ground water, surface water, and unconsolidated geological material from the Rayrock area were collected for chemical and radiochemical analyses. Results indicated that the surface waters contained levels of 226Ra as high as 20 Bq L-1, 210Pb as high as 1.1 Bq L-1, and ground water U as high as 2800 micrograms L-1. Lower levels of 226Ra, 210Pb, and U, 3.6 Bq L-1, 0.5 Bq L-1, and 4 micrograms L-1, respectively, were found in a small lake adjacent to the tailings area. Analysis of tailings and soil in the immediate vicinity indicates that the radionuclides and U are mobilized and can move within the tailings. Some of the mobilized radionuclides will be bound by the surrounding peat. The remainder may move to Lake Alpha in ground water. Surface water flow also transports some contaminants both in the water of Alpha Creek and by washing tailings into Lake Alpha. The potential annual external and internal dose equivalents to a hypothetical resident were calculated based on exposure from the abandoned U mill tailings, drinking water, and fish caught in the lakes in the vicinity of the tailings. While Alpha Creek and Lake Alpha water showed evidence of contamination, the rest of the water system and the fish were at natural background levels of radioactivity.

Animals↗

Radiation hygienic evaluation of nuclear fission products (review).

Nuclear-fission products (NFP) are a complex mixture of radionuclides of variable organotropism. Their physicochemical properties depend on the conditions of their formation and age. In a contaminated environment they are a source of external, contact, and internal gamma- and beta-irradiation. Dangerous is the entry of NFP into the organism, especially that of children and pregnant women. In a radiation-hygiene review, the author sums up his own materials and those of other investigators on radiation injuries developing upon the contamination of the skin and penetration of NFP into the organism. The risk of injuries and delayed effects is evaluated. Dose sizes producing injuries of different severity are given. Protective measures should be directed toward prevention of skin contamination and entry of NFP into the organism, early sanitary treatment, and prompt discharge of radionuclides from the organism. Of particular importance in the genesis of severe injury, the course of reparative processes and formation of delayed pathology, is radiation injury to the thyroid gland by iodine radioisotopes. Hence an important place among prophylactic measures should belong to the "protection" of the thyroid gland and normalization of its function.

Absorption↗

Transport of the radioisotopes iodine-131, cesium-134, and cesium-137 from the fallout following the accident at the Chernobyl nuclear reactor into cheesemaking products.

The transport of radiation contamination from milk to products of the cheese making process has been studied. The concentration of radioactive iodine and cesium in samples of sheep milk and cheese (Gruyère) products was measured for 10 consecutive production d. Milk with concentration 100 Bq/L in each of the radionuclides 131I, 134Cs, and 137Cs cheese with concentration 82.2 +/- 3.9 Bq/kg in iodine and an average of 42.3 +/- 2.3 Bq/kg in the cesium isotopes is produced. The corresponding concentrations in cream extracted from the same milk are 26.7 +/- 2.8 Bq/kg (131I) and 18.6 +/- 1.9 Bq/kg (134Cs, 137Cs).

Accidents↗

Transfer of aged Pu to cattle grazing on a contaminated environment.

Estimates are obtained of the fraction of ingested or inhaled 239+240Pu transferred to blood and tissues of a reproducing herd of beef cattle, individuals of which grazed within fenced enclosures for up to 1064 d under natural conditions with no supplemental feeding at an arid site contaminated 16 y previously with Pu oxide. The estimated (geometric mean [GM]) fraction of Pu transferred from the gastrointestinal tract to blood serum was about 5 x 10(-6) (geometric standard error [GSE] = 1.4) with an approximate upper bound of about 2 x 10(-5). These results are in reasonable agreement with the value of 1 x 10(-5) recommended for human radiation protection purposes by the International Commission on Radiological Protection (ICRP) for insoluble Pu oxides that are free of very small particles. Also, results from a laboratory study by Stanley (St75), in which large doses of 238Pu were orally administered daily to dairy cattle for 19 consecutive days, suggest that aged 239+240Pu at this arid grazing site may not be more biologically available to blood serum than fresh 239+240Pu oxide. The estimated fractions of 239+240Pu transferred from blood serum to tissues of adult grazing cattle were: femur (3.2 X 10(-2), 1.8; GM, GSE), vertebra (1.4 X 10(-1), 1.6), liver (2.3 X 10(-1), 2.0), muscle (1.3 X 10(-1), 1.9), female gonads (7.9 X 10(-5), 1.5), and kidney (1.4 X 10(-3), 1.7). The blood-to-tissue fractional transfers for cattle initially exposed in utero were greater than those exposed only as adults by a factor of about 4 for femur (statistically significant) and of about 2 for other tissues (not significant). The estimated (GM) fraction of inhaled Pu initially deposited in the pulmonary lung was 0.34 (GSE = 1.3) for adults and 0.15 (GSE = 1.3) for cattle initially exposed in utero (a statistically significant difference), which may be compared with the expected fraction of 0.11 at the study site using the ICRP lung model for humans.

Administration, Inhalation↗