Indoor radon concentrations in Athens and neighborhooding areas are relatively low compared withvalues in the northern part of Greece [1,2]. Nevertheless, we have localized a dwelling near Athens(N. Makri), with an elevated radon concentration. We attained this result from the integrative sampling etched track detector placed in open mode (nitrated type film Kodak) for one year long.The etching procedure and estimation of concentration (Bq/m3 with an uncertainty of 20%) wereconducted by the radon facilities of the Institute for Testing and Disaster Medicine, Milin, CzechRepublic [3].
In accordance with the Basic Standards of Radiation Protection issued by EURATOM and the recommendations of the Federal Commission of Radiation Protection (SSK), radon measurements were carried out at 80 of a total of 240 waterworks in the state of Baden-Wrttemberg from the end of 1994 to mid-1997. The measurements covered more than 1000 working places. The waterworks were selected among others on the basis of the number of employees, the size of the supply area, the geological and hydrological parameters, and the surface coverage.
Radon-reduction in private and public buildings is a current issue. Research has opened our eyes for the enormous fluctuation of the indoor radon level over longer observation periods. Normally, the time sequence of the radon concentration can be characterized as a mixture of (periodic) circadian variations overlayed with (aperiodic) seasonal fluctuations. Other factors may be attributed to the activities of the inhabitants. Today, different expert groups are proposing mathematical models to describe the radon level in a building.
In the indoor environment short-lived radon decay products deposit onto surfaces. Alpha decaying atoms obtain recoil energy enough to implant into the substrate. This hideaway phenomenon permits the use of implanted long-lived radon decay products as a measure of past radon exposures. Specifically flat glass surfaces has been used as radon retrospective monitors and thanks to the development of special track-etch devices (retro detectors) the implanted surface activity can be measured in-situ.
In the Bihor uranium district there are an operating underground mine and the closed down open pit mine. The open pit mine was operated by the Soviets between 1952-1964, the ore being "exported" to the Soviet Union. The mean content of the uranium ore was 2%. The "waste rocks" from the open pit mine were used by the natives in the foundations of detached houses in rural areas. The goal of the survey was to identify this houses and to make radon and gamma dose rate measurements to assess the annual effective doses incured by the public.
The Nuclear Engineering Section of the National Technical University of Athens undertook the organisation of a European building material radon exhalation rate intercomparison exercise in the framework of the European Research into Radon In Construction Concerted Action (ERRICCA). The intercomparison started in June 1998 and it was concluded in February 1999. Twenty participants from 13 countries took part. The exercise focused on the radon exhalation rate determination from a concrete slab, specially constructed to produce radon surface flux well below 10 mBqm-2s-1.
Four commercially available integrated radon concentration measurement instruments, produced by the same manufacturer in the period between 1996 to 1998, have been tested to study the effect of absolute humidity on the radon counting efficiency. All four devices use high efficiency dRAM cells semiconductor sensor chips for alpha particle detection. The chips are located inside a measurement chamber, which is separated from the ambient air by a filter.
Radon and thoron and their decay products are the most important sources of radiation exposure to thegeneral public, contributing on average about half of the total effective dose equivalent received fromnatural and man-made radioactivity, such situation is encountered also in Poland. The short-liveddecay products of 222Rn decay to 210Pb with half-life of 22 years contribute to the inhaled effectivedose of man.The estimation of radon risk in Poland is made on the basis of radon concentration in soil gas.
^ Department of Experimental Physics, University College Dublin, Dublin 4, IrelandCase-control studies on lung cancer and radon in dwellings have been conducted in North Americaand Europe, including one study in Lazio region, in Central Italy. Great attention is generally devotedto the reduction in the uncertainty in radon exposure assessment because it can give rise to relevantuncertainty in the estimated risk. One of the main potential sources of uncertainty is the use ofcontemporary radon concentration measurements as estimators of past concentration values.
Many retrospective studies regarding the long time exposure to radon (222Rn) are based on theaccumulation of 210Pb (T1/2=22.3y) on the surface of glass objects or other materials and measuring thespecific alpha activity of 210Po (T1/2=138 d, E?=5.3 MeV) resulted by implanting of radon daughters,due to the alpha recoil. In the case of thoron (22oRn) this method is not applicable because there is nota long life time isotope to allow a signifficant accumulation of any descendant. The longest life timeof the thoron descendants is 212Pb with a live time of T1/2= 10.6 hours.
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