IN THE LAST 10 YEARS SOIL RADON MEASUREMENTS HAVE BEEN SUCCESSFULLY APPLIED TO EVALUATE RADON RISK OF FUTURE BUIDING SITES IN MANY COUNTRIES SUCH AS CHECK REPUBLIC, GERMANY, SWITZERLAND AND ITALY.
WE BELIEVE THAT THIS COMPREHENSIVE REPORT ON RADIOLOGICAL PROTECTION AGAINST RADON EXPOSURE CANNOT DISREGARD THIS ISSUE.
IN THE FOLLOWING, WE EXPLAIN WHY, ON THE BASIS OF OUR EXPERIENCE AND PUBBLICATIONS.
Paola Tuccimei 1, *, Mauro Castelluccio 1, Carlo Lucchetti 1 and Massimo Moroni 2
1 Università “Roma Tre”, Largo San Leonardo Murialdo 1, 00146 Roma
2 GEOEX s.a.s., Via Colli del Vivaro 1, 00040 Rocca di Papa, Roma, Italia
* Corresponding author e-mail: tuccimei@uniroma3.it
Comments on ICRP, ref 4829-9671-6554 dated 6-DEC-2011
Importance of preventive actions based on the classification of radon risk in urban planning
As listed in the “Main Points” section, the radon strategy should include both preventive (new buildings) and corrective (existing buildings) actions. A national radon protection strategy should then take into account the issue of radon exposures during the planning, design and construction phase of a building. Actions plan should also deal with radon measurement techniques and protocols, national radon surveys to identify radon prone areas, methods for mitigating the radon exposure and their applicability in different situations.
Most screening actions on environmental radioactivity takes place in indoor environment. It should be emphasized that these kind of measurements, widely and successfully performed worldwide for epidemiological investigations, are affected by several variables such as life style of residents, types of construction (building and its foundation), window frames sealing, presence of heating, ventilation and air conditioning, the exposure season (summer/winter), rooms orientation, local climate, etc. It can therefore be argued that buildings constructed with different materials and techniques, inhabited by families with different life styles, may be characterised by very different indoor radon levels even if located in the same area. It follows that a preliminary screening aimed at evaluating the general risk of a given territory cannot be based only on indoor radon surveys, without considering the above-mentioned parameters. In order to define correctly the risk, it is necessary to acquire knowledge on radon-prone areas. Radon risk mapping must rely on the study of local geology and, in particular, on lithology, permeability, karst phenomena, backfills thickness and nature and finally tectonic unconformities occurrence that may favour the transfer of large amounts of deep-seated gases.
The classification of radon risk should follow two different paths according to the scale of the survey: first and second level studies, respectively focused on general zoning of the territory in the frame of regional and municipal master plans and evaluation of soil radon exhalation and concentration at local-scale executive urban planning.
In the first case, the classification should be geologically-based and rely on a subdivision according to “Rock Units” to which specific rates are assigned. This scoring approach, see for example the PERS (Soil Radon Exhalation Potential) method originally developed in Italy (ANPA, 2000) for studies at national scale, could be successfully employed in more detailed investigations for the definition of radon-prone areas. The “Rock Unit” is a three-dimensional homogeneous rock body, identified on the basis of its lithology and geometry (areal extension and tickness). It is often bordered by tectonic features (faults), but is also described and rated according to petrographical, structural and textural characteristics: radioactive elements concentrations (see in particular 226Ra), cracks distribution, porosity, permeability and idrogeological setting. Specific scores are assigned to each indicator and processed to get the PERS value. A complementary monitoring and testing phase is scheduled to check radon concentration and exhalation characterising territories with given PERS.
Second level studies apply to urban planning in areas classified as potentially at risk according to first level investigations (CASTELLUCCIO, 2010; CASTELLUCCIO et alii, 2010). They allow estimating the radon index (IR), a parameter that defines the level of local risk linked to radon emission. It depends on soil radon concentration and intrinsic permeability, measured at a depth of 80 cm. The value of these parameters allow quantifying the strength of the radon source and describing the gas ability to flow in the subsoil and build up in closed spaces. Building protection practices and other infrastructure works corresponding to different values of the indices are also provided.
This method (CASTELLUCCIO et alii, 2011; 2012) was developed from the pioneering procedure proposed in the Check Republic (NEZNAL et alii, 2004). It provides advantages over a posteriori actions (NEZNAL et alii, 2004), either in terms of costs or in terms of technical efficiency. Finally, it is worth emphasizing that also the Joint Research Centre of the European Commission (JRS) which is developing the European Geogenic Radon Map within the long-term project of a European Atlas of Natural Radiation is taking into consideration this approach (https://rem.jrc.ec.europa.eu/RemWeb). The working group is now evaluating the “transfer function” approach (based on equilibrium concentration of 222Rn in soil air and soil effective permeability). As alternative option, the US classification scheme (based on a combination of indoor measurements, geological characteristics, aerial radioactivity, soil permeability and foundation type, USEPA, 1993) is under consideration.
References
ANPA, Agenzia Nazionale per l’Ambiente, (2000) – Il Sistema Informativo Territoriale per la valutazione del Potenziale di Esalazione di Radon dal Suolo. Rapporto ANPA, serie Stato dell’Ambiente 9/2000.
CASTELLUCCIO M. (2010) Soil radon concentration survey in Caffarella Valley test site (Rome) Ph.D. Thesis in Geodynamics at the “Roma Tre” University
CASTELLUCCIO M., GIANNELLA G., LUCCHETTI C., MORONI M. & TUCCIMEI P. (2011) - Il rischio radon in edilizia. Proposta di codifica di un protocollo per la classificazione del rischio. Professione Geologo, Notiziario dell’Ordine dei Geologi del Lazio, 27: 8-13.
CASTELLUCCIO M., GIANNELLA G., LUCCHETTI C., MORONI M. & TUCCIMEI P. (2012) - Evaluation and classification of radon risk in urban planning, submitted to the Italian Journal of Engineering Geology and Environment.
NEZNAL M., NEZNAL M., MATOLÌN M., BARNET I. & MIKSOVA J. (2004) - The new method for assessing the radon risk of building sites Czech Geological Survey Special Papers, CGS Prague
USEPA, United States Environmental Protection Agency (1993). Protocols for Radon and Radon Decay Product Measurement in Homes. USEPA Publication 402-R-92-003. Washington, D.C