Programas de radón en Irlanda David Fenton Radiological

Programas de radón en Irlanda David Fenton Radiological Protection Institute of Ireland Universidade de Santiago de Compostela 26 June 2003

Programas de radón en Irlanda • Vivienas / La Encuesta Nacional Irlandesa • Colegios • Puestos de Trabjo

Structure of Presentation • Review of RPII • Historical Notes • National Survey • Workplaces • Homes • Schools

THE RADIOLOGICAL PROTECTION INSTITUTE OF IRELAND • Regulatory Authority • Advisory Body • Licensing Authority • Dosimetry Service • Radon Monitoring Service • Environmental Monitoring • Certification Service • Information & Library Service

Annual Effective Dose to Irish Public from All Sources Thoron (160 µSv) Medical (300 µSv) Artificial (10 µSv) Internal (300 µSv) Terrestrial (300 µSv) Cosmic (300 µSv) Radon (2250 µSv) Total = 3. 62 m. Sv

Evolution of the Radon Issue in Ireland

• 1985 -1989: • 1989 -1992: • 1990: First Survey UCD RPII Follow-Up Surveys Domestic Reference Level adopted 200 Bqm-3 – long term whole house average. Level at Which Householders are Advised to Consider Remedial Action • 1992: National Geographically based Radon Survey Commenced

La Encuesta Nacional Irlandesa

La Encuesta Nacional Irlandesa • Survey Carried out 1990’s • Identify Areas at Greatest Risk • Survey Results incorporated into Building Regulation-Technical Guidance Documents (Dept of Environment) • Included in legislation implementing BSS directive • Survey Published in 2002

Radon Mapping Technique Used in Ireland A Radon Prediction Map was produced by the RPII by Modelling the Distribution of Indoor Radon Concentrations

Determination of the Indoor Radon Distribution in Ireland • National Geographical Based Radon Survey Was Conducted over 7 Years • Houses Selected at Random From Every 10 km Grid Square in the Country • A minimum of 5 houses per 10 km Grid Square was Required

• Land mass of Ireland covers Eight Hundred and Thirty Two 10 km Grid Squares • Radon Measurements Over 12 Months were carried out in 11, 319 Houses • Indoor Radon Levels in Irish Houses Follow a Log-Normal Distribution

Methodology Used for Estimating the Proportion of Houses in Excess of a Given Reference Level • Calculate the Geometric Mean (GM) and the Geometric Standard Deviation (GSD) for Each 10 Km Grid Square • Estimate the Proportion of Houses in Each 10 Km Grid Square using the Formula k = ln(200 ref)-ln(GM)/ln(GSD) where k is a transformed threshold for use with the standard normal distribution

• Once k is Known, the Proportion of Houses in Excess of the Stated Reference Level is Obtained from Statistical Tables of the Area Under the Standardised Curve

Methodology Adopted in Situations Where Insufficient Data Was Obtained in 10 Km Grid Squares • Used a Smoothing Technique to Obtain representative Values of both GM and GSD • This Smoothing Technique Uses the Available Data in the 10 Km Grid Square and the Data in Surrounding Grid Squares

Missing Grid Squares Interpolation / Smoothing Y X Y 10 km X T Y X X Y 10 km Require: GM and GSD • Data in square • Data in neighbouring squares - amount - quality

• A Weighting Matrix was Generated for Each Grid Square which Took into Account the Data in Each Grid Square and the Variance of the Data • The Weighting Matrix was Applied to the Radon Measurements in Surrounding Grid Squares

• For Grid Squares along the Coast the Weighting Matrix was adjusted to take account of Neighbouring Grid Squares being Off-Shore or at Sea • Based on the Approach of Breslow and Clayton -American Statistical Journal, June 1993

Survey Details • Geographically Based Survey - Default Unit Area: 10 Km Grid-Squares of Irish National Grid System • Requirement: 5 houses per 10 Km Grid Square • 53000 Householders Contacted over 7 years • Measurements were Completed in 11319 Houses (1 in 93 Houses throughout the Country)

• Names and Addresses of Householders were Randomly Selected from the Register of Electors • Householders Invited by Letter to Participate • Radon Detectors Issued/Returned by National Postal System

Measurement Procedure • Passive Track Etch Radon Detectors • Two Detectors Issued per Household 1 in Principal Bedroom 1 in Main Living Area Measurement Period: 12 Months • Annual Average Whole-House Radon Concentration Determined • Results Issued by Post-Included Recommendations Regarding the Necessity for Remedial Action

Track-Etch Passive Radon Detectors

National Survey Summary Results • Average Radon Concentration = 89 Bqm-3 • Min value: 10 Bqm-3 • Max value: 1924 Bqm-3 • Number Predicted as greater than 200 Bqm-3: 91, 000 Houses (7% of National Housing Stock)

End-Use of the Radon Prediction Map • The Department of the Environment and Local Government has issued Building Regulations (1998) and Technical Guidance Documents on Radon preventative measures to be followed when Constructing New Buildings • The Prediction Radon Map of Ireland is Incorporated into national regulations • Indicated a need to survey schools

Regulatory Position in Ireland