Introduction NEHA RRNC March 2010

Transcription

1 Radon Resistant New Construction Workshop National Environmental Health Association Washington DC, March 23-25, 25, 2010 What Is Radon? Radon Radium Uranium Radon is a gas. It is naturally occurring. It cannot be seen or smelled. It enters buildings from the soil beneath them. How Is Radon Drawn Into A Building? Vacuum Exhaust systems Thermal stack effects Radon pci/l Vacuum (pa.) Days 1

2 Why Is Radon A Concern? Radon Decay Products Radon Radon Radon decays into radioactive particles known as radon decay products. These particles are easily inhaled and deposited in the lungs where they can damage sensitive lung tissue. Let s s get technical, for a moment Radioactive Decay Radon-222 Alpha Radiation Gamma Radiation Polonium-218 Alpha Radiation Gamma Radiation Spontaneous Radiation is released in the process Alpha - very damaging Beta - little damage per impact Gamma - little damage per impact 2

3 Half lives 3.8 days 3 minutes Radon and Its Short-Lived Radon Decay products 27 minutes 19.7 minutes minutes 19.4 years Radon-222 α,γ Polonium-218 α,γ Lead-214 β,γ Bismuth-214 β,γ Polonium-214 α,γ Lead-210 β,γ Radon Gas Measured in pci/l Short-lived decay products Solids Inhaled & stick to lungs Create health concerns Adhere to solid objects Measured in terms of Working Levels Recoil from Alpha Release Strips Electrons Causing Resultant Decay Product to be Charged + Ion Stripped Electrons Alpha particle Radon Decay Product Radon Atom Alpha Particles Are Strong Enough To Pit Plastic Photo: Dr. J.F. Burkhart Plastic chip from passive radon test (alpha track) Magnified only 100 times 3 months at EPA Action Level of 4 pci/l 3

4 Effect of Alpha Particle Release in Lungs OH - H + H 2 O Chromosome 6, P53 gene impacted Random in direction May kill cell Preferred result Chemical reactions Direct strike of DNA Can impair cancer suppressant genes P53 & others Cell loses ability to defend against cancer. Radon Induced Lung Cancer Equal weight of time and dose creates liner model of risk. One dart could be enough, hence no threshold in risk model Risk increased equally by both duration and concentration of exposure One dart at a time for a long time, or handfuls of darts over a short time Radon Is A Lung Cancer Causing Gas Radon decay products inhaled. While in the lungs they can decay. Alpha particles released Like small bullets Lung cells do not have covering to shield themselves Can kill or cause damage to cells that leads to increased potential of lung cancer. 4

5 EPA & Surgeon General Recommend That People Not Have Exposures Above 4 pci/l On A Long-Term Basis One is advised to take action if a home is at or above 4.0 pci/l (or WL) Curie: the amount of radiation generated from 1 gram of radium One pico Curie: one trillionth of a curie Average indoor: 1.3 pci/l Average outdoor: 0.4 pci/l Equilibrium Factor (EF) Plated out RDPs Suspended RDPs The equilibrium ratio is the fraction (or percentage) of RDPs suspended in the air relative to the total RDPs created. EF = Suspended RDPs Total RDPs Current EPA risk Assessments assume 40% of radon decay products remain airborne Working Level Month (WLM) Risk is equally weighted to exposure and duration of exposure. Exposure: Radon decay products in air (measured in working levels (WL) Duration: Time Typically expressed in months) Risk compared to Working Level Months (WLM) WLM = WL x hours 170 hours/month For example WL (4.0 pci/l) for 70 years at 75% occupancy: WLM = x 24 hr/day x 365 day/year x 70 years x 75% = 43 WLM 170 hours/month Increased risk in miner studies was seen as low as 40 WLM accum.. exposure (Australia) 5

6 Radon Distribution Radon enters from beneath foundation and travels upward. Diluted with outdoor air infiltrating building. If radon is less than 4 pci/l in lower level, one can say with reasonable confidence that upper floors are also less than 4 pci/l. Overall Radon Entry Is Seasonal Long-Term Radon (pci/l) House 1 House 2 Seasonal Changes (Cold Climate) House 3 House 4 House 5 Winter Summer Entry rates can be higher in: Cold climates during winter Hot climates during summer (no evaporative coolers) Tropical climates during rainy season Test Purpose Dictates Conditions Radon Potential: Short-term term test Typically days Closed building conditions 12 hours prior to and all during test Device deployed on lowest occupiable level of home. Commonly used at time of resale. Occupant Exposure: Long-term test Typically 91 days to year Normal lived in conditions without special closed building conditions. Device deployed on lowest occupied level of home. Commonly used outside of resale, or used as basis of escrow fund release. 6

7 Common Short-Term Test Devices Activated charcoal devices from certified laboratories Placed by: Measurement Providers offering Standard Services Analyzed by third-party labs Results not available on site. Deployed for days Continuous Monitor Use in Real Estate Testing Single device Variations can detect tampering Must measure and report in hourly increments and be calibrated If average is equal to, or greater than 4 pci/l, mitigation is recommended. 0 Alpha track detector shown Long-term Tests Indicate Occupant Exposure Placed for a minimum of 91 days No special closed building conditions Can be used for release of escrow funds If result is equal to, or greater than 4 pci/l, mitigation is recommended. 7

8 Successive 2-Day, 2 Short-Term Measurement Results in Same House Over a three-month period, short-term term real estate style tests varied 7 from 1.9 to 6.0 pci/l. 6 2-Day Averages (pci/l) Average for entire period was 3.8 pci/l Source: Dr. Dan Steck,, Minnesota Radon Project Jan-March 1995 Radon Zone Map by County Used for determining where radon control techniques in new home construction would be of the greatest benefit. Not for determining where to test! Radon entry primarily a function of source. Based on geology and survey results Expected short term radon (pci/l): Zone 1 > 4.0 Zone 2 > 2 < 4.0 Zone 3 < 2.0 So if there is a risk, how can we reduce it? Lets review Radon Resistant New Construction RRNC 8

9 HIGH LOW Reducing Radon in Existing Homes Any Ideas? Removal Lots of Uranium of Ventilation? Bearing Soils? New Homes Can Be Built With Radon Control Systems FAN 9