**1. Introduction**

In the 1950s, Otto Huber and his team from the University of Fribourg started the regular monitoring of radioactivity in Switzerland [1]. Some years later, the federal government

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initiated a countrywide monitoring programme. In 1969, the first nuclear power plant (NPP) of Beznau came on line to produce electric power. Today, five NPPs are producing about 38% of the electric powerin Switzerland. In addition to the emission controls of the NPPs and other radiation-producing facilities, the monitoring of radioactive fallout from the atmospheric, nuclear bomb tests is of special concern. Over 600 bomb tests in the atmosphere led to a contamination of the Northern Hemisphere with long-lived radionuclides, such as radiocae‐ sium, radiostrontium, and plutonium. The contamination situation was then aggravated by the reactor fire of the NPP of Chernobyl in late April of 1986. In Switzerland, the southern and eastern parts were more affected (in southern Switzerland, it rained on 3–5 May over 350 mm precipitation). On 5 May, the National Emergency Operations Centre (NAZ) started a monitoring programme for food with the help of the specialised laboratories in Dübendorf, Freiburg, Lausanne, Spiez, Würenlingen, and the State Laboratory Basel-City. In October 1986, a symposium on the measurements and their interpretation was held in Berne [2]. In 1987, other state laboratories took part in the monitoring programme. Five years later, when radiation levels were reduced considerably, most of the state laboratories reduced their monitoring programmes again; many state laboratories even cut off their survey activities. Until 2011, the radioactivity survey was mainly supported by the specialised laboratories. The core meltings of the Fukushima-Daiji NPPs gave a short increase in the survey activities for the years 2011/2012 in Switzerland.
