Zdravko Faj

Radon equilibrium factor and aerosols

Equilibrium factor values (F) were measured in the NRPB radon chamber and corresponding track densities of the bare (D) and diffusion (D0) LR-115 nuclear track detectors were determined. The obtained empirical function, F(DD0), has agreed with the theoretical one, that had been derived by using concentration equations for the radon and its short-lived decay products. Measurements of the detector track densities and aerosol concentrations (ca) made possible a fitting of the DD0(ca) function, that after introducing into the F(DD0) gave a relationship for aerosol concentration, F(ca). So, it was possible to assess a radon dose equivalent if concentrations of radon and aerosols in the air were known (measured).

The equilibrium factor F between radon and its daughters

The theoretical relationship between the equilibrium factor F of radon and its daughters and the air exchange rate as well as the relationship between F and the track density ratio of the open (D) and filtered (D0) SSNT detector were examined. method of determining the factor F by means of the measured or given ratio DD0 was derived and an equation for the function F(DD0) was obtained. Application of the function F(DD0) to the track density measured by the detector LR-115 has given equilibrium factor values in the range from 0.14 to 0.78.

Radon in schools and dwellings of Osijek

Indoor radon concentrations were measured in 10 821 pupils primary schools of Osijek by means of the Radhome silicon detector. The values ranged from 15 to 300 Bq/m3 with the arithmetic and geometric means of 93.4 and 70.6 Bq/m3, respectively. Ten years continuous radon measurements performed with the LR-115 nuclear track detector in three houses of different construction and town area gave means of 27, 96 and 23 Bq/m3; the indoor Rn concentration for a heating period was a factor of 1.5 higher than for the warm season. The average effective dose equivalent for the primary school pupils was 2.8 mSv/y (with occupancy factors of 0.6, 0.2 and 0.2 for home, school and outdoors, respectively). For citizens of Osijek it was 1.7 mSv/y.

Radon in the spa of Bizovac

The radon concentration in the air and water of the Bizovac spa was measured by the Radhome silicon detector and the average values were obtained as 70 Bq/m3 in the indoor pool, 40 Bq/m3 in the hotel room, 135 Bq/m3 in the closed therapeutic bathroom, but the geothermal water had a Rn concentration of 25.3 kBq/m3 and the potable one 2.7 kBq/m3. The Rn transfer factor (f) from water to air in the indoor pool and therapeutic bathroom was 10 and 40 times higher than for normal dwellings (fn=10−4), respectively. The effective equivalent dose of inhaled radon for permanent personnel under the worst conditions in the spa was 5.4 mSv/y, but visitors spending two weeks in the spa could receive the dose of 77 μSv.

Radon exposure and lung cancer

Although studies of radon exposure have established that Rn decay products are a cause of lung cancer among miners, the lung cancer risk to the general population from indoor radon remains unclear and controversial. Our epidemiological investigation of indoor radon influence on lung cancer incidence was carried out for 201 patients from the Osijek town. Ecological method was applied by using the town map with square fields of 1 km2 and the town was divided into 24 fields. Multiple regression study for the lung cancer rate on field, average indoor radon exposure and smoking showed a positive linear double regression for the mentioned variables. Case-control study showed that patients, diseased of lung cancer, dwelt in homes with significantly higher radon concentrations, by comparison to the average indoor radon level of control sample.

Indoor Radon Concentrations in Kindergartens from Different Regions of Yugoslavia

In the winter period of 1990-1991 instantaneous radon concentrations in air were measured in around 450 kindergartens from different regions from Yugoslavia. Alpha scintillation counting was used as a screening method, and the measurements, were carried out in the rooms where the children spent the majority of their time. All of the air grab samples were taken under the same conditions which excluded ventilation of the interior 12 hours prior to sampling. In addition to indoor radon concentrations, gamma dose rate was measured using portable equipment. The indoor radon concentrations were generally low, in the range from 10 to 180 Bq.m-3 of air, with an overall average of about 100 Bq.m-3. There were a few exceptions where indoor radon levels exceeded 150 Bq.m-3, mainly in old buildings containing higher contents of natural radionuclides in the building materials, and in the cellars or basements of the buildings. In all rooms with a level exceeding 150 Bq of 222Rn per m3, solid-state nuclear track detectors were applied for long-term measurements. In order to investigate the equilibrium between radon and its short-lived daughters, mainly with respect to their contribution to the effective dose, alpha spectrometry is also being introduced in selected kindergartens with elevated radon concentrations.

Radon dose assessment by the LR-115 detector

The theoretical relationship between the equilibrium factor F of Rn and its daughters and the track densities of the open (D) and filtered (D0) solid-state nuclear track detector was examined. A method for determining the factor F as well as the dose equivalent for the measured values D and D0 was derived. Measurements of that rack densities by the LR-115 detector gave an annual effective dose equivalent of 1.03 mSv y−1 for radon and its progeny in the town of Osijek (Visnjevac) during the year 1988.

Radon dose and aerosols

The equilibrium factor value (F) was measured in the NRPB radon chamber and the corresponding track density ratio (r = D/D0) of bare (D) and diffusion (D0) LR-115 nuclear track detectors was determined, as well as the regression equation F(r). Experiments with LR-115 nuclear track detectors and aerosol sources (burning candle and cigarette) were carried out in the Osijek University radon chamber and afterwards an empirical relationship between the equilibrium factor and aerosol concentration was derived. For the purpose of radon dose equivalent assessment, procedures for determining the unattached fraction of radon progeny were introduced using two nuclear track detectors.