English Abstract The document contains a critical risk-evaluation of
Radon to humans and the environment. Radon is an inert gas of which the
main risk is induction of lung cancer. Considering the nature of its
effects and its presence only the by-products of Rn-222 are important for
man in the indoor environment. In the indoor environment the average Rn-222
concentration is about 10 times higher than in the outdoor air. The average
exposure to Radon in the Netherlands results in an estimated risk of 60
cases of fatal lung cancer per million people per year, of which 80% as a
result of Rn-222 and 20% as a result of Rn-200. This risk is partly present
by nature (the emission is determined by the soil for about 95%) and is
therefore not always controlable. Without taking measures the risk will
increase as a result of building new houses. By taking measures in all
houses that will be built in future (increased ventilation of crawl space,
sealing the ground floor) an annual decrease of the average individual risk
of o.6% seems attainable. The spread of the exposure level is large and
restriction of the individual risks can only be reached by organizing the
problems.