The Chernobyl nuclear power plant accident happened on April 26, 1986. We investigated the cause of the striking increase in frequency of thyroid cancer in children who lived within a 150 km radius of Chernobyl and who were born before and after the accident. No thyroid cancer was seen in 9472 children born in 1987-89, whereas one and 31 thyroid cancers were recorded in 2409 children born April 27, 1986, to Dec 31, 1986, and 9720 born Jan 1, 1983, to April 26, 1986, respectively. Short-lived radioactive fallout caused by the Chernobyl accident probably induced thyroid cancer in children living near Chernobyl.
The 131I activity was measured in 30 human fetal thyroids in Zagreb district after the Chernobyl accident. A model of radioiodine metabolism in the mother and human fetus which takes into account the age dependence of the uptake and retention of radioiodine in the fetal thyroid was developed. Having assessed that the total intake by the average mother was about 1330 Bq, a good correlation between calculated and measured fetal thyroid activities was found (r = 0.77, P less than 0.001). The fetal thyroid dose reached the maximum of 0.43 micro Gy/Bq intake at about the fifth month of gestation. It was concluded that the risk of having a child with a harmful trait due to 131I absorbed by the mother was negligible.
Mice which were alive in Durham at the time of the Chernobyl nuclear accident presented a highly significant increase in the incidence of those which bore tumours. The comparison is based upon mice which were studied over the previous 4 years. In males and females the increase amounted to 19 and 100 per cent respectively. The most frequent neoplasms to increase were malignant tumours of the reticuloendothelial system and of the reticuloses, lymphosarcoma and reticulum cell sarcoma were prevalent in mice kept after Chernobyl. The incidence of reticuloses increased by 24 and 18 per cent in males and females respectively.
Residents of Vienna, Austria were whole-body counted for radiocesium content due to fallout deposited after the Chernobyl accident. Data for a 2-y period were compared with prior estimates of radiocesium body burden based on food consumption. Our results suggest that the prior estimates be revised and the rejection limit be increased by a factor of 2 for contaminated food.
1) Two Jersey cows were fed during 90 days with contaminated hay harvested in the South-East of France and containing about 5500 Bq/kg of dry matter (134 Cs + 137 Cs). A plateau was observed in milk 15 days and in meat 50-60 days after the beginning of the contamination. The transfer coefficients were at that time 1.1% for the milk and 2-2.7% for the meat. A calf was fed from the 8th day after birth until the 80th day solely with the contaminated milk from the two cows. At that time and weighing 130 kg it retained more than 40% of the ingested caesium. From the 44th till the 80th day the daily intake of milk was constant: in these conditions the transfer coefficient to meat was 16%. 2) Transfer coefficients to milk and thyroid were determinated in three Friesian cows contaminated daily with Na131I in pellets, one month before and two months after calving; one more lactating cow was contaminated for one month, 5 months after calving. The parturition provokes a fall of about 40% in the thyroid burden of the cows followed by a return near the initial equilibrium level (2-3 times the daily uptake in summer and 1 time in winter). At birth the ratio between the specific radioactivity of the calf thyroid and the cow thyroid was about 3. Transfer coefficients in milk at the equilibrium (one month after calving) were 0.35-0.50% in summer and 0.75-1.25 in winter.
A study on caesium contamination in human milk, as a consequence of the Chernobyl fallout, was conducted in 1989 on a group of women from one of the areas of northern Italy most heavily affected by the radioactive fallout. Their diet was studied, and the caesium intake was calculated by using the mean food activity concentration in that area. The caesium transfer factor was evaluated both as the ratio of caesium concentration in mother's milk to the daily intake, and by using a simplified milk compartment model.
Following the Chernobyl accident many activities were conducted in Ukraine in order to define the radiological impact. Considered here are gamma spectrometric analyses of soil-depth-profile samples taken in the years 1988-1999, gamma spectrometric measurements of radionuclide concentration in soil samples taken in 1986, and measurements of external gamma-exposure rate in air. These data are analyzed in this paper to derive a "reference" radionuclide composition and an attenuation function for the time-dependent rate of external gamma exposure that changes due to the migration of radiocesium into the soil column. An attenuation function for cesium is derived that consists of two exponential functions with half lives of 1.5 and 50 y. The dependencies of attenuation on direction and distance from the Chernobyl Nuclear Power Plant are also demonstrated. On the basis of these analyses the average individual and collective external gamma doses for the population of Ukraine are derived for 1986, 1986-2000, and 1986-2055. For the 1.4 million persons living in rural areas with 137Cs contamination of >37 kBq m(-2), the collective effective dose from external exposure is estimated to be 7,500 person-Sv by the end of 2000. A critical group of 22,500 persons who received individual doses of >20 mSv is identified for consideration of increased social and medical attention.
Dietary studies and whole-body measurements were used to estimate the intake of radiocesium and the radiation dose received by different groups of people in Norway after the Chernobyl accident. Freshwater fish, milk, and reindeer meat were the major sources for radiocesium intake. Dietary advice, together with agricultural decontamination measures, resulted in a considerable reduction in the exposure level of the population. A majority (40-80%) of the specially selected groups (farmers-hunters and Sami reindeer herdsman) changed its diet significantly after the accident. Without dietary changes, specifically a reduction in the consumption of freshwater fish and reindeer meat, the Sami group would have had a 400-700% higher radiocesium intake, and the farmers-hunters' intake would have been up to 50% higher than what they actually had experienced.