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Possible effects of Chernobyl fallout on outcome of pregnancy in Finland were evaluated in a nationwide follow-up study. The outcomes were the rate of live births and stillbirths, pregnancy loss, and induced abortions by municipality. Exposure was assessed based on nationwide surveys of radiation dose rate from the Chernobyl fallout, from both external and internal exposures. Using these measurements, we estimated the monthly dose rate for each of the 455 Finnish municipalities. On average, the dose rate from Chernobyl fallout reached 50 microSv per month in May 1986--a doubling of the natural background radiation. In the most heavily affected area, 4 times the normal background dose rates were recorded. Given the underlying regional differences in live birth, stillbirth, and abortion rates, we used longitudinal analysis comparing changes over time within municipalities. A temporary decline in the live birth rate had already begun before 1986, with no clear relationship to the level of fallout. A statistically significant increase in spontaneous abortions with dose of radiation was observed. No marked changes in induced abortions or stillbirths were observed. The decrease in the live birth rate is probably not a biological effect of radiation, but more likely related to public concerns of the fallout. The effect on spontaneous abortions should be interpreted with caution, because of potential bias or confounding. Further, there is little support in the epidemiologic literature on effects of very low doses of radiation on pregnancy outcome.

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The aim of the present study was to determine the forms of 137Cs, 90Sr and 239,240Pu occurring in different soil horizons using sequential extraction of samples taken from four sites located along a pollution gradient from the copper-nickel smelter at Monchegorsk in the Kola Peninsula, Russia, and from a reference site in Finnish Lapland in 1997. A selective sequential-leaching procedure was employed using a modification of the method of Tessier, Cambell and Bisson ((1979). Analytical Chemistry, 51, 844-851). For 137Cs the organic (O) and uppermost mineral (E1) layer were studied, for 90Sr and 239,240Pu only the uppermost organic layer (Of). The fraction of 137Cs occurring in readily exchangeable form in the organic layer was about 50% at the reference site and decreased as a function of pollution, being 15% at the most polluted site in the Kola Peninsula. There was a clear positive correlation in the O layer between the distance from the smelter and the percentage of 137Cs extracted in the readily exchangeable fraction (Spearman correlation rsp = 0.7805, p = 0.0001), whereas in the E1 layer no correlation was evident. The distribution of 90Sr in the Of layer was similar at all sites, with the highest amounts occurring in exchangeable form and bound to organic matter, whereas stable Sr showed a somewhat different distribution with the highest amount in the oxide fraction. Most of the 239,240Pu was bound to organic matter. Chemical pollution affected the exchangeable fraction of 239,240Pu, which was about 1% at the most polluted site and 4-6% at the other sites.

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To study the impact of industrial pollution on the soil-to-plant uptake of fallout-radiocesium in a boreal forest ecosystem, four study sites were selected at distances of 7, 16, 21 and 28 km from the large copper-nickel smelter at Monchegorsk on the Kola Peninsula (Russia). At each site, soil and selected plant species were sampled from five plots and analysed separately for 137Cs and 40K. The data show that the root-uptake of 137Cs, as characterised by the median aggregated transfer-factor T(ag), decreased significantly (P < 0.05) with decreasing distance from the smelter for the plants Vaccinium myrtillus (from 0.023 to 0.007 m2 kg-1) and Empetrum nigrum (from 0.015 to 0.007 m2 kg-1), but increased for Deschampsia flexuosa (from 0.013 to 0.031 m2 kg-1). For Vaccinium vitis-idaea a significant trend for the T(ag) was not observed. The median 40K activity concentrations in these plants also decreased significantly (P < 0.001) with decreasing distance from the smelter for Vaccinium myrtillus (from approx. 140 to 20 Bq kg-1 dry wt.), Empetrum nigrum (from approx. 90 to 40 Bq kg-1 dry wt.), and also for Deschampsia flexuosa (from approx. 270 to 40 Bq kg-1 dry wt.). For Vaccinium vitis-idaea such a continuous significant trend was not observed. The results for the Cu-Ni polluted soils thus show: (1) that the soil-to-plant transfer of radiocesium can be significantly modified; (2) that these modifications are quite specific; and (3) that modifications of the uptake of potassium do not always correspond to those of radiocesium.

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OBJECTIVE: To assess effects of fallout from Chernobyl on incidence of childhood leukaemia in Finland. DESIGN: Nationwide cohort study. External exposure measured for 455 Finnish municipalities with instruments driven 19,000 km throughout the country. Values specific to municipalities corrected for shielding due to houses and fallout from A bomb testing. Internal exposure estimated from whole body measurements on a random sample of 81 children. Mean effective dose for two years after incident calculated from these measurements. Data on childhood leukaemia obtained from Finnish cancer registry and verified through hospitals treating childhood cancers. SETTING: Finland, one of the countries most heavily contaminated by the Chernobyl accident; the population was divided into fifths by exposure. SUBJECTS: Children aged 0-14 years in 1976-92. MAIN OUTCOME MEASURES: Standardised incidence ratio of childhood leukaemia and relative excess risk of childhood leukaemia per mSv. From incidence data of Finnish cancer registry for 1976-85, expected numbers specific to sex and age group (0-4, 5-9, and 10-14 years) were calculated for each municipality for three periods (1976-85, 1986-8, and 1989-92) and pooled as exposure fifths. Dose response was estimated as regression slope of standardised incidence ratios on mean doses for fifths for each period. RESULTS: Population weighted mean effective doses for first two years after the accident were 410 microSv for the whole country and 970 microSv for the population fifth with the highest dose. In all Finland the incidence of childhood leukaemia did not increase 1976-92. The relative excess risk 1989-92 was not significantly different from zero (7% per mSv; 95% confidence interval -27% to 41%). CONCLUSIONS: An important increase in childhood leukaemia can be excluded. Any effect is smaller than eight extra cases per million children per year in Finland. The results are consistent with the magnitude of effect expected.

PIP: The objective of a nationwide cohort study was to assess the effects of fallout from Chernobyl on the incidence of childhood leukemia in Finland, one of the countries most heavily contaminated by the Chernobyl accident. External exposure was measured with instruments driven by car 19,000 km throughout 455 Finnish municipalities, where the population was divided into fifths by exposure. Values specific to municipalities were corrected for shielding due to houses and fallout from A-bomb testing. Internal exposure estimated from whole body measurements on a random sample of 81 children aged 0-14 years during 1976-1992 and 5-15 in June, 1986, and April, 1988. Mean effective doses from cesium-134 and cesium-137 for 2 years after the incident were calculated from these measurements. Data on childhood leukemia cases that had occurred in children aged 0-14 years during 1975-1992 were obtained from the Finnish cancer registry and verified through each of the 5 university hospitals treating childhood leukemia. Standardized incidence ratio of childhood leukemia and relative excess risk of childhood leukemia per milli sievert (mSv) was measured. From incidence data of the Finnish cancer registry for 1976-1985, expected numbers specific to sex and age group (0-4, 5-9, and 10-14 years) were calculated for each municipality for 3 periods (1976-85, 1986-8, and 1989-92) and pooled as exposure fifths. Dose response was estimated as regression slope of standardized incidence ratios on mean doses for fifths for each period. Population-weighted mean effective doses for first 2 years after the accident were 410 micro Sv for the whole country and 970 micro Sv for the population fifth with the highest dose. In all Finland, the incidence of childhood leukemia did not increase during 1976-1992. The relative excess risk 1989-1992 was not significantly different from zero (7% per mSv; 95% confidence interval -27% to 41%). An important increase in childhood leukemia can be excluded. Any effect is smaller than 8 extra cases per million children per year in Finland.

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The explosion at the Chernobyl nuclear power plant caused radioactive fallout in Finland in April-May 1986. The fallout was unevenly distributed geographically, and, accordingly, the country was divided into 3 fallout zones. Whole-body radioactivity measurements of randomly chosen persons showed that the regional differences prevailed throughout the following 2 years. Data for legal abortions, registered congenital malformations as well as preterm births and stillbirths of malformed children were collected. The corresponding expected figures were obtained from statistics from 1984 and 1985. No differences in the expected/observed rates of the above parameters were detected.

PIP: The effects of the 1986 Chernobyl accident on Finland are reported. Legal abortions, registered congenital malformations, preterm births, and stillbirths showed no differences in observed vs. expected rates after the accident. The limitations are that the population base is small, the detection system is incomplete, no reliable data are available on early abortions, and germinal mutations were not presently analyzed. Measurement of radiocesium (Cs 134 and 137) was accomplished by the Research Institute for Social Security with a stratified random sample of 380 people. 5 fallout zones differentiated groups, which were then collapsed into 3 groups. Regional differences in levels persisted into 1988. The Finnish Register of Congenital Malformations provided the compulsory data on congenital malformations. The 3 groups (children born before the accident in 1984-85, in the latter half of 1986, and in 1987) were analyzed in the 3 zones during 2 study periods (August-December 1986 and January-December 1987). Monthly analysis of induced abortions showed no increase following the accident. There was a slight decrease in births between January and March 1987, which is believed to be related to anxiety reinforced by public advice. There were no differences between expected and observed congenital defects in the 2 study periods. Preterm and stillbirths followed a similar pattern. The analysis showed no association between the temporal and spatial variations in radioactivity and variable incidence of congenital malformations.

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The highly sensitive whole-body counting technique makes quantitative determinations of nanocurie amounts of gamma-emitters within the body possible. So such counters are especially suitable for the long-term measurement of tracer retention and excretion rates. In the present study, the biological half-life of body potassium in ten male volunteers was determined using 42K as tracer. The group was measured using two different types of whole-body counters. A 43-cm standard chair technique was used with counter A and a multidetector linear scanning technique with counter B. The oral tracer dose of 12-15 muCi 42K to volunteers made it possible to estimate the biological half-life of potassium, which varied from 10 to 28 days, the mean being 16 days. The total body potassium determinations were carried out with the 42K- and 40K-methods. The results of the parallel determinations performed with Counter A agreed well with those of Counter B. A good consistency was also found in the body potassium values of individual subjects, obtained using both the methods separately for each counter.

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