Radiological consequences of the Chernobyl accident for Switzerland

The Chernobyl accident has led to the first full scale operation of the Swiss Radiological Emergency Organisation. The deposition of radioactive substances in Switzerland took place in three different time periods, affecting mainly three different parts of the country. Highest levels were found in the southern part where heavy rainfall occurred in early May. External dose rates reached values of 180 μR.h-1 and the maximum surface depositions of 137Cs and 131I were 26 and 180 kBq.m-2 respectively. Average values for Switzerland remained more than one order of magnitude lower. Activity concentrations in vegetables, milk, and meat reached high values in some regions (maximum for 131I or 137Cs close to 5 kBq.kg-1). Consumption of certain products was not recommended in these regions, especially by the critical group, i.e. small children and pregnant women. No food was banned in Switzerland. The resulting effective dose equivalent to the most exposed group was estimated to be about 1.5-2 mSv in 1986. The average for the Swiss population is about one order of magnitude lower. The average annual effective dose equivalent due to all sources (except Chernobyl) in Switzerland is around 4 mSv.y-1. (author)