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INDOOR RADON MAPPING IN FINLAND

Anne Voutilainen and Ilona Mäkeläinen
STUK (Radiation and Nuclear Safety Authority) P.O. Box 14, FIN-00881 Finland
Tel. +358 9 759 881, fax +358 9 7598 8556
Email: anne.voutilainen@stuk.fi and ilona.makelainen@stuk.fi

For over ten years STUK (The Radiation and Nuclear Safety Authority, Finland) has performed
systematic indoor radon mapping with municipal health authorities. In the most radon-prone
provinces (Uusimaa, Kymi and Häme) there are about 480,000 low-rise dwellings. It is expected
that in 51,000 homes the action level of 400 Bq/m 3 is exceeded, of which about 6,000 have been
detected. In the rest of Finland the numbers are: 820,000 low-rise dwellings, 17,000 expected
cases of exceeding the limit, of which 800 were detected, respectively. In the three
abovementioned provinces 20% of the houses investigated exceed the level of 400 Bq/m 3 and 40-
50% exceed the level of 200 Bq/m 3 . In the rest of Finland the figures are 4% and 13%,
respectively. The most powerful search for radon should be focused on the provinces of Uusimaa,
Kymi and Häme, where almost 80% of the houses exceeding the action level are situated. The
search for high concentrations is worthwhile everywhere in Finland in areas where they have
already been found. The search is easiest in esker areas and other sand and gravel deposits because
they are easy to locate from geological maps.
Key words: indoor radon, geology, mapping, esker, soil type