DOWN-SYNDROME CLUSTERS IN GERMANY AFTER THE CHERNOBYL ACCIDENT

In two independent studies using different approaches and covering Wes t Berlin and Bavaria, respectively, highly significant temporal cluste rs of Down syndrome were found. Both sharp increases occurred in areas receiving relatively low Chernobyl fallout and concomitant radiation exposures. Only for the Berlin cluster was fallout present at the time of the affected meioses, whereas the Nuremberg cluster preceded the r adioactive contamination by 1 month. Hypotheses on possible causal rel ationships are compared. Radiation from the Chernobyl accident is an u nlikely factor, because the associated cumulative dose was so low in c omparison with natural background. Microdosimetric considerations woul d indicate that fewer than 1 in 200 oocyte nuclei would have experienc ed an ionizing event from Chernobyl radioactivity. Given the lack of u nderstanding of what causes Down syndrome, other than factors associat ed with increased maternal age, additional research into environmental and infectious risk factors is warranted. (C) 1997 by Radiation Resea rch Society.