OBJECTIVE--To evaluate the outcome of pregnancy in Finnish women after the accident at the Chernobyl nuclear power plant on 26 April 1986. DESIGN--Geographic and temporal cohort study. SETTING--Finland divided into three zones according to amount of radioactive fallout. SUBJECTS--All children who were exposed to radiation during their fetal development. Children born before any effects of the accident could be postulated--that is, between 1 January 1984 and 30 June 1986--served as controls. INTERVENTIONS--Children were divided into three temporal groups: controls, children who were expected to be born in August to December 1986, and children who were expected to be born in February to December 1987. They were also divided, separately, into three groups according to the three geographic zones. END POINT--Incidence of congenital malformations, preterm births, and perinatal deaths. MEASUREMENTS AND MAIN RESULTS--There were no significant differences in the incidence of malformations or perinatal deaths among the three temporal and three geographic groups. A significant increase in preterm births occurred among children who were exposed to radiation during the first trimester whose mothers lived in zones 2 and 3, where the external dose rate and estimated surface activity of caesium-137 were highest. CONCLUSIONS--The results suggest that the amount of radioactive fallout that Finnish people were exposed to after the accident at Chernobyl was not high enough to cause fetal damage in children born at term. The higher incidence of premature births among malformed children in the most heavily polluted areas, however, remains unexplained.
Comment In: BMJ. 1989 May 20;298(6684):13842502266
Our objective was to explore whether the radiation fallout in Finland after the accident at the Chernobyl nuclear power plant in April 1986 led to an increased incidence of trisomy 21. In this geographic and temporal cohort study, the country was divided into three zones according to the amounts of radioactive fallout and internal radiation caused by two cesium isotopes. The 518 cytologically verified cases of trisomy 21 were divided into a control group (conceived before the accident), and a study group of children whose expected dates of birth were in the post-accident years 1987-1988, i.e., pregnancies commenced after May 1986. The cases were also divided into three subgroups according to the zones of radiation. There were no significant differences in prevalence of trisomy 21 between the control and study groups nor between the three zones in spite of the significant differences in the levels of radiation and in the body burden that prevailed throughout the study period. Power estimates showed that in the two zones of lower radiation, an increase of 0.5% in the prevalence would have been detected with a power of 0.85, and in the somewhat smaller zone of the highest radiation, with a power of 0.70. The study lends no further support to the view that the low radiation fallout in western Europe would have been causally associated with trisomy 21.
This report examines the claim that Irish mortality in the second quarter (April-June) of 1986 increased due to the cloud of radioactive material released by the damaged reactor in Chernobyl. Over the period 1971-1987, based on date of registration, the death rates in the second quarter showed marked year to year variation often exceeding that expected on the basis of chance alone. In 1986 the percentage of annual deaths occurring between April and June, and the death rate itself, were both significantly higher than in most other years between 1981 and 1987. The 1986 figures were not however, significantly higher than those observed in years prior to 1981. Since the distribution of mortality by cause was not consistent with the hypothesis relating low level radiation to immediate mortality, and since causality cannot be inferred from a temporal association per se, the Chernobyl accident cannot be implicated in the excess mortality observed in the second quarter of 1986.
An analysis was carried out of multiaberrant ("rogue") cells in lymphocytes of persons living in unpolluted areas (controls), and in areas chemically or radioactively (Chernobyl fall-out) polluted. The total number of analysed cells was 102,391, among these 10 cells with three and more aberrations were found. These multiaberrant cells occur in persons of both sexes and various ages living in regions with a moderate degree of mutagenic exposure. The main types of aberrations in multiaberrant cells were chromosome exchanges, accompanied by double fragments.
It was attempted to assess the incidence of thyroid diseases in Polish children born between 1980-1986, who at the time of the Chernobyl nuclear disaster were 0-6 years old, or whose mothers were in the third trimester of pregnancy. 3071 children have been examined, 1772 girls and 1299 boys. The following were assessed in each child: the health status, the developmental level, the thyroid ultrasound examination, and the level of TSH, FT4, antithyroid antibodies ATM and ATGL in the blood serum. Disorders in thyroid morphology (abnormal echogenicity) have been found in 462 children (15%), almost twice as much in girls than in boys. Goiter has been recognized in 4.6% of all children, an abnormal echogenity in 5.4% and focal changes in 4.8%. 3.9% of children have been found to have a high level of ATM antibodies, and 8.7%--a high level of ATGL antibodies. Among 6 children, who had thyroidectomy, 2 children have been diagnosed to have ca papillary and 4 children--adenoma.
The results of experimental studies on the repeated exposure to radioiodine (131I) and nuclear fission products (NFP) are presented, the doses used being equal to those resulted in radiation disease under first and second input. The animals satisfactory withstood the repeated exposure. The residual injuries appeared slightly. The animals' state was satisfactory during 5 years. Blastomogenic effect of NFP was revealed in remote periods.
In Norway, external doses of radiation resulting from fallout from the Chernobyl nuclear accident were estimated from detailed measurements, including soil deposition patterns. Internal doses were estimated from measurements of radioactive cesium in meat and milk supplies. The doses were calculated as average monthly doses for each of 454 municipalities during 36 consecutive months after the accident in spring 1986. Prospectively collected data on all newborns listed in the Medical Birth Registry of Norway who were conceived in the period May 1983-April 1989 were used to assess possible dose-response relations between estimated external and food-based exposures and congenital malformations and some other conditions. A positive association was observed between total radiation dose (external plus food-based) and hydrocephaly, while a negative association was observed for Down's syndrome. However, an important conclusion of the study was that no associations were found for conditions previously reported to be associated with radiation, i.e., small head circumference, congenital cataracts, anencephaly, spina bifida, and low birth weight. Potential sources of bias, including exposure misclassification and incomplete ascertainment of cases, are discussed.