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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.

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.

The distribution and biological half-life of 203Hg in the human body was investigated using 203Hg-labeled compounds and a regional whole-body counting technique. Fifteen volunteers were administered methylmercury as a labeled fish proteinate. A single serving of the proteinate contained an average of 1.8 uCi of 203Hg-activity and 22 mug of total mercury. Inorganic mercury was given to eight volunteers as labeled calf liver paste containing 4-8 muCi of inorganic 203Hg-activity and 6 mug of total mercury. The radiomercury determinations were performed in a steel room equipped with the standard chair geometry and one 4 inch x 8 inch NaI(Tl) crystal. For determinations of 203Hg-activity in the head a 3 inch x 3 inch NaI(Tl) crystal was used. A lead collar was utilized as a shield in order to absorb any disturbing radiation that might originate in the stomach region. The effectiveness of the Pb collar was determined using phantoms. The activities in the whole-body, the head, the legs and the liver were determined. About 20% of the methylmercury activity in the whole-body was found to be localized in the head 30 d after administration. No significant amounts of 203Hg-activity were found in the head during the first 58 d after administration of inorganic mercury. An average value of 10-15% methylmercury activity was found in the legs 30 d after administration. A control mean value of 13% was determined by measuring five of the same volunteers the next day in Sweden. Not more than 1% of inorganic mercury was found in leg muscle after 39 d in one male volunteer. The biological half-life of protein-bound inorganic mercury in the liver region, studied in one male volunteer, was estimated at 53 +/- 15 d.

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.