The incidence of neoplasms in childhood and adolescence in northern and central Sweden before and after the radioactive fallout from the Chernobyl accident was investigated in an ecologic study, 1978 to 1992. The study included all parishes in the six most contaminated counties classified after aerial mapping of ground radiation from 137Cs and investigated 746 cases of neoplasms in ages 0-19 y, diagnosed in the six counties. Incidence and relative risks of neoplasms were compared in areas with high, intermediate, and low contamination after versus before the Chernobyl accident in 1986. A continuous increase of brain tumor incidence in the ages 0-19 y during the period 1978-92 without clear relationship to the Chernobyl fallout was discovered. No clear relationship between the incidence of brain tumor and the exposure to varying levels of radiation from 137Cs was apparent. A somewhat decreased relative risk of acute lymphatic leukemia appeared in areas with increased exposure. Other neoplasms showed no changes in incidence over time or with regard to exposure. Until now, there is no indication that the Chernobyl accident has affected the incidence of childhood and adolescence neoplasms in Sweden, but it is still too early for any final conclusion about the effect of this event.

Study objective: Is there any epidemiologically visible influence on the cancer incidence after the Chernobyl fallout in Sweden?

Design: A cohort study was focused on the fallout of caesium-137 in relation to cancer incidence 1988–1996.

Setting: In northern Sweden, affected by the Chernobyl accident in 1986, 450 parishes were categorised by caesium-137 deposition: <3 (reference), 3–29, 30–39, 40–59, 60–79, and 80–120 kiloBecquerel/m².

Participants: All people 0–60 years living in these parishes in 1986 to 1987 were identified and enrolled in a cohort of 1 143 182 persons. In the follow up 22 409 incident cancer cases were retrieved in 1988–1996. A further analysis focused on the secular trend.

Main results: Taking age and population density as confounding factors, and lung cancer incidence in 1988–1996 and total cancer incidence in 1986–1987 by municipality as proxy confounders for smoking and time trends, respectively, the adjusted relative risks for the deposition categories were 1.00 (reference <3 kiloBecquerel/m²), 1.05, 1.03, 1.08, 1.10, and 1.21. The excess relative risk was 0.11 per 100 kiloBecquerel/m² (95% CI 0.03 to 0.20). Considering the secular trend, directly age standardised cancer incidence rate differences per 100 000 person years between 1988 to 1996 and the reference period 1986–1987, were 30.3 (indicating a time trend in the reference category), 36.8, 42.0, 45.8, 50.1, and 56.4. No clear excess occurred for leukaemia or thyroid cancer.

Conclusions: Unless attributable to chance or remaining uncontrolled confounding, a slight exposure related increase in total cancer incidence has occurred in northern Sweden after the Chernobyl accident.

Background After the Chernobyl accident in 1986, as much as 5% of the released caesium-137 was deposited in Sweden due to a heavy rainfall 2 days after the event. A study of increased incidence of malignancies was initiated after the accident.

Methods The cohort included 1,137,106 inhabitants who were 0-60 years old in 1986 and lived in 8 counties of Sweden with the highest fallout of caesium-137. With the dwelling coordinate, GIS-technique and a digital map on caesium-137, each individual was matched for the exposure. Adjustments were made for several potential confounding factors. During the follow-up 33,851 malignancies was recorded 1988-1999.

Results Exposure categories were: 0-8 (reference), 9-23, 24-43, 44-66, 67-84, and 85 nGy/hr. The corresponding adjusted Mantel-Haenszel incidence rate ratios for total malignancies during follow-up amounted to 1.000, 0.997, 1.072, 1.114, 1.068, 1.125, respectively. The excess relative risk per 100 nGy/hr with the same adjustments and time period was 0.042 95% confidence limit 0.001;0.084. An excess for thyroid cancer or leukemia could not be ruled out.

Conclusion Increased incidence of total malignancies possibly related to the fallout from the Chernobyl accident is seen.

Background: Two previous epidemiological studies on the incidence of total malignancies in Sweden after the Chernobyl accident have shown consistently increased risks. The first study used an analogue map on (CS)-C-137 from 1986 to classify individuals in terms of the parish they lived in. In the second study, dwelling coordinates were matched to a digital map from the year 2000 to assess the individual exposure. To establish the accuracy of the exposure assessment using the larger unit of parish, instead of coordinates, we decided to compare the methods.

Methods: On the analogue map eleven isolines on the deposition of Cs-137 (kBq/m(2)) were used to classify all individuals in each of the 450 parishes. Using the digital map, by contrast, each dwelling with its inhabitants could be matched to Cs-137 deposition at a coordinate level. A population-weighted average of Cs-137 deposition was calculated for each parish. In total, 1,126,960 individuals and 450 parishes were included and analysed into six different exposure categories.

Results: Using the new parish exposure index, 111 out of the 450 parishes were reclassified as a result of the increased resolution of the digital map (86 parishes) or unequal distribution of the population compared with the deposition (25 parishes). Seventy-five per cent of the parishes remained in the same exposure category as on the analogue map.

Conclusion: Using dwelling coordinates for exposure assessment may not always be superior to parish classification. Nor is it always a cost-effective way of estimating the exposure, especially if the exposure in a parish is relatively homogenous or if parishes can be merged into broader categories with little intra-parish difference.

As a result of the Chernobyl accident in 1986, exposure to radioactive cesium is still a concern in the contaminated regions of Belarus. We tested the hypothesis that long-term radiation exposure from the Chernobyl accident might increase the urinary excretion of the oxidative stress marker, 8-hydroxydeoxyguanosine (8-OHdG), in Belarussian children. Urinary 8-OHdG was determined in two groups of children (—n = 31 and n = 46) —living in contaminated and uncontaminated areas of Belarus, respectively (the majority of the unexposed children lived in the capital Minsk). The children from the contaminated areas had a significantly higher annual summary effective dose but significantly lower urinary 8-OHdG levels than the children from the uncontaminated areas. Unexpectedly, children living in uncontaminated urban areas had significantly higher urinary 8-OHdG levels than children living in uncontaminated rural areas. There was no statistically significant effect of sex or body mass index on urinary 8-OHdG, but there was a weak significant inverse correlation to age as well as to the annual summary effective dose. These findings suggest that radiation from the Chernobyl accident is now a less important contributor to oxidative stress in Belarussian children than urban living.