English

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.

The National Survey on Radon Indoors was designed to estimate the distribution of annual radonconcentration in Italian dwellings, on the basis of a representative sample of about 5000 dwellings. Itstarted in 1989 and ended in 1994, involving all Italian Regions except Sicilia and Calabria, due toorganizational problems in these two regions of Southern Italy. After the official conclusion, tworegional surveys were also carried out in Sicilia and Calabria, using the same experimental apparatusand protocols as in the other Regions.

A first review of the numerous data on the areas in Italy where high radon concentration in dwellingshave been found is presented here. The data were obtained from the national survey and from severallocal surveys carried out in areas where high radon concentration values were expected, on the basis ofthe national survey results or of geological considerations. The analysis is restricted to data obtainedwith long-term measurements.

A convenient, low-cost, time-integrating monitor based on the track-etching technique wasdeveloped for measuring the deposition rate of attached 220Rn progeny indoors. Simultaneousmeasurements for deposition rates and concentrations of 220Rn progeny were performed in 13 housesduring 12 months. Various values were observed among those houses, but seasonal variations werenot clearly observed. The deposition velocity of attached 220Rn progeny was estimated to be(0.53?0.11)?10-2 cm?s-1, in fair agreement with most of the values of attached 222Rn progeny indwellings in the literature.

The purpose of this contribution is to situate the radon issue within the whole field of radiationprotection. There is among health physicists a fairly general consensus that exposure to radon decayproducts constitutes the largest and most variable contribution to the population exposure. It istherefore ironical that precisely this exposure is the subject of constant disputes with regard to thevalidity of the risk estimates and to the desirability of inciting the population living in radon proneareas to take action.

About two hundred volume traps were retrieved from dwellings in various radon prone areas inEurope. They were analysed for the purpose of retrospective radon assessment. Emphasis is put onspecific problems encountered when using field samples as opposed to laboratory exposed samples. Itwas seen that in very dusty circumstances, direct penetration of radon decay products from the outsideto the centre of the volume traps calls for extra caution. Rinsing the samples is proposed as a solutionand was tested in field and laboratory conditions, showing good results.

A simple intercomparison of natural radioactivity and radon emanation factor measurementscoordinated by the Medical Physics Department of the University of Cantabria UC, Spain, has beencarried out during 1998 in the framework of the EU Concerted Action ERRICCA (European Researchinto Radon in Construction Concerted Actio). All the measurements have been made on a "blueconcrete" sample friendly delivered by Dr. G.