O. Ennemoser

Unusually high indoor radon concentrations from a giant rock slide

In a village in western Tyrol, Austria (Umhausen, approximately 2600 inhabitants) unusually high indoor radon concentrations were measured. The medians were found to be 3750 Bq/m3 (basements) and 1160 Bq/m3 (ground floors) in winter, and 361 Bq/m3 (basements) and 210 Bq/m3 (ground floors) in summer. Maximum radon concentrations of up to 274,000 Bq/m3 were registered. The unusually high radon concentrations are due to the geology of the locality. The part of Umhausen with the highest radon concentrations is built on an alluvial fan of a giant rock slide (granitic gneiss). Measurements of the radon exhalation rate from soil showed a median of 0.4 Bq/m2/s, measurements of the radium content of rock samples yielded a median of 125 Bq/kg. The material of the rock slide is heavily fractured so that an elevated emanating power and an increased diffusion coefficient for radon in soil must be assumed. Given a diffusion coefficient of 8 x 10(-6) m2/s and an emanating power of 0.3, the median exhalation rate of 0.4 Bq/m2/s is obtained at a radium concentration of 125 Bq/kg. The rock slide is therefore considered to be the main source of radon. The abnormally high radon concentrations in Umhausen coincide with a statistically significant increase in lung cancer mortality (age and sex standardized mortality rate = 3.9, 95% C.I.: 2.9-5.1); the control population is the population of the entire Tyrol (630,000 inhabitants).

Radon measurements in soil to predict indoor radon concentrations in new buildings in an area with unusually high radon levels

Abstract We investigated the possible correlation between measurements of radon concentrations in soil and indoor radon concentrations. Such a correlation could be used to estimate the radon concentrations to be expected in new buildings, which is important for the evaluation of building plots. For this purpose, we measured the seasonal course of radon concentrations in 41 tubes along two profiles in an area with unusually high radon levels (Umhausen, 2600 inhabitants, Tyrol, Austria). Parallel to the measurements in the tubes, radon concentrations were measured in the basements of 30 houses located within a radius of 15 m around the tubes in July 1992 and in February 1993. Linear correlation analysis was performed to establish the correlation between the indoor measurements and the measurements in the tubes. Measurements of radon concentrations in soil give only limited information about the radon concentrations to be expected in new buildings, and seasonal and local variations make predictions based on spot measurements unreliable.

Increased radon concentrations in classrooms used for pottery workshops

In a pilot study of nine schools the radon (Rn) concentrations were measured systematically. The mean radon concentrations in the classrooms on the ground-floor and on higher floors was 52 Bq/m3, which is equivalent to the mean values in Central Europe. Several of the basement rooms used for handicraft lessons had significantly increased Rn levels with a mean concentration of 617 Bq/m3. In all other parts of the basement Rn levels were clearly lower with a mean concentration of 136 Bq/m3. In the rooms used for handicraft lessons numerous articles of pottery were on display. After removing these the Rn in air concentration was reduced to a mean value of 83 Bq/m3.

Unusually high indoor radon concentrations

Abstract Measurements of indoor radon concentrations in the village Umhausen (2600 inhabitants, Otztal valley, Tyrol, Austria) revealed unusually high indoor radon concentrations up to 274,000 Bq m −3 . The medians measured on the basements were 3750 Bq m −3 in winter and 361 Bq m −3 in summer, those on the ground floors were 1180 Bq m −3 and 210 Bq m −3 , respectively. Seventy-one per cent of the houses showed basement radon concentrations above the Austrian action level of 400 Bq m −3 in winter, 33% in summer. There are indications that the high radon concentrations are due to a giant rock slide about 8700 years ago. The unusually high radon concentrations in Umhausen coincide with a statistically significant increase in lung cancer mortality. For the period 1970–1991 the age and sex standardized mortality rate is 3.85 (95% confidence interval: 2.9 to 5.1). The control population is the total population of Tyrol (630,000 inhabitants).