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Evaluation of Percentage-based Radon Testing Recommendations for Multi-family Housing

Evaluation of Percentage-based Radon Testing Recommendations for Multi-family Housing. CDR Antonio Neri, MD, MPH. Medical Epidemiologist Comprehensive Cancer Control Branch 28 th International Radon Symposium Charleston , SC Sept. 30, 2014.

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Evaluation of Percentage-based Radon Testing Recommendations for Multi-family Housing

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  1. Evaluation of Percentage-based Radon Testing Recommendations for Multi-family Housing CDR Antonio Neri, MD, MPH Medical Epidemiologist Comprehensive Cancer Control Branch 28th International Radon Symposium Charleston, SC Sept. 30, 2014 National Center for Chronic Disease Prevention and Health Promotion Division of Cancer Prevention and Control

  2. Probability of Detecting ≥1 Unit With Radon ≥ 4.0 pCi/L When Testing 10% of All Units

  3. Probability of Detecting ≥1 Unit With Radon ≥ 4.0 pCi/L When Testing 25% of All Units

  4. Background

  5. Freddie-Mac / Fannie Mae Section 13.15(b) (May 2007) “The number of units on the lowest habitable floor tested must be the greater of • A minimum of 10 percent of the units on the lowest habitable floor, or • One unit per building”

  6. ANSI-AARST MAMF-2010 (July 2010) “3.1 Conduct a measurement in each ground contact apartment, dwelling and those rooms that are used as office space.” ANSI-AARST Guideines Website: http://www.aarst.org/standards/messages/296/296.html?1284208255

  7. HUD Mortgagee Letter 2013-07 (Jan. 2013) “Exception: With reference to Section III.3.1 of ANSI-AARST MAMF-2010 (or similar section in the most recent edition), the minimum number of apartments to be tested shall be at least twenty-five percent of randomly selected ground level units.” HUD Guidelines Website: http://portal.hud.gov/hudportal/documents/huddoc?id=13-07ml.pdf

  8. Confusing Signs

  9. Ohio Dept. of Health Clarification “IN ADDITION - We have received numerous licensee inquiries about the January 1, 2013 HUD notice about multifamily testing. The HUD Notice H 2013-03 Section IV (A)(4)(a)(1) Exception, says that “the minimum number of apartments to be tested shall be at least twenty-five percent of randomly selected ground level units.” It’s important to understand that that the HUD exception does not limit the number of apartments tested to 25%, it simply states what HUD believes is their minimum acceptable requirements.” Ohio DOH Website: http://www.odh.ohio.gov/~/media/ODH/ASSETS/Files/rp/radon%20licensing/RN2013%2001%20Multi-Family%20Testing.ashx

  10. What does this all mean? • There are many percentage-based recommendations • It is unclear whether these are effective in finding radon in multifamily homes if it exists • Statistical methods exist to evaluate these approaches • Evaluation can provide information for policy-makers

  11. Study questions Assuming a given number of units are ≥ 4.0 pCi/L • What is the probability of finding a ground-floor unit with radon ≥ 4.0 pCi/L if you: • Test 10% or 25% of ground-floor units in various size structures? • Vary the % of ground-floor units tested in a given-size structure? • How many ground-floor units do you have to test over a range of structure sizes in order to be 95% sure you find at least one ground-floor unit with radon ≥ 4.0 pCi/L, if one exists?

  12. Methods

  13. Statistical Approach • Hypergeometric distribution • Determines the probability of identifying at least one “object,” assuming a certain # of “objects” are present in a sample population • Really just an elegant test for “probability” Web link for hypergeometric distribution: http://stattrek.com/probability-distributions/hypergeometric.aspx

  14. Probability – Example Radon ≥ 4.0 pCi/L Radon < 4.0 pCi/L

  15. Probability – Example Radon ≥ 4.0 pCi/L Radon < 4.0 pCi/L Question: What is the probability of finding ONE unit with radon ≥ 4.0 pCi/L if we randomly test one unit?

  16. Probability – Example Radon ≥ 4.0 pCi/L Radon < 4.0 pCi/L Question: What is the probability of finding ONE unit with radon ≥ 4.0 pCi/L if we randomly test one unit? Answer: 5 homes with radon / 10 total homes 50% probability

  17. Probability – Example Radon ≥ 4.0 pCi/L Radon < 4.0 pCi/L Unit already tested so not available Question: Yet, if we get a < 4.0 on the first unit tested, what is the probability of finding a unit with radon ≥ 4.0 pCi/L if we randomly test again?

  18. Probability – Example Radon ≥ 4.0 pCi/L Radon < 4.0 pCi/L Question: Yet, if we get a < 4.0 on the first unit tested, what is the probability of finding a unit with radon ≥ 4.0 pCi/L if we randomly test again? Answer: 5 homes with radon / 9 total homes 56% probability

  19. Probability – Example Radon ≥ 4.0 pCi/L Radon < 4.0 pCi/L Unit already tested so not available Question: Yet, if we get a < 4.0 on the second unit tested, what is the probability of finding a unit with radon ≥ 4.0 pCi/L if we randomly test again?

  20. Probability – Example Radon ≥ 4.0 pCi/L Radon < 4.0 pCi/L Question: Yet, if we get a < 4.0 on the second unit tested, what is the probability of finding a unit with radon ≥ 4.0 pCi/L if we randomly test again? Answer: 5 homes with radon / 8 total homes 63% probability

  21. Probability – Example Radon ≥ 4.0 pCi/L Radon < 4.0 pCi/L Question: How many units do we need to test in order to have 95% probability of finding a unit with radon ≥ 4.0 pCi/L?

  22. Probability – Example Radon ≥ 4.0 pCi/L Radon < 4.0 pCi/L Question: How many units do we need to test in order to have 95% probability of finding a unit with radon ≥ 4.0 pCi/L? Answer: 5 homes with radon / 5 total homes left (if other units tested were < 4.0 pCi/L) 100% probability

  23. Study Assumptions • Number of units with radon ≥ 4.0 is either: • 1 in 15 (EPA National Average for single-family homes) • 1 in 3 (Average for states with high-prevalence of radon) • Ground-floor units most often have the highest radon concentrations • Units are “independent” • Radon levels in one unit do not relate to radon levels in other units

  24. Results

  25. Probability of Detecting ≥1 Unit With Radon ≥ 4.0 pCi/L When Testing 10% of All Units

  26. Probability of Detecting ≥1 Unit With Radon ≥ 4.0 pCi/L When Testing 25% of All Units

  27. Probability of Detecting ≥1 Unit With Radon ≥ 4.0 pCi/L When Testing a Percentage of Units in 10-Unit Structure

  28. Probability of Detecting ≥1 Unit With Radon ≥ 4.0 pCi/L When Testing a Percentage of Units in 20-Unit Structure

  29. Probability of Detecting ≥1 Unit With Radon ≥ 4.0 pCi/L When Testing a Percentage of Units in 30-Unit Structure

  30. Number of Ground-floor Units to be Tested to Obtain 95% Probability of Identifying ≥1 Unit With Radon ≥ 4.0 pCi/L at Prevalence of 1:3

  31. Number of Ground-floor Units to be Tested to Obtain 95% Probability of Identifying ≥1 Unit With Radon ≥ 4.0 pCi/L at Prevalence of 1:15

  32. Discussion

  33. Discussion • Recommendations for testing to identify radon in multi-family homes could be improved • Especially with smaller numbers of units • The hypergeometric distribution allowed us to identify appropriate cutoffs for the # of units to be tested to achieve 95% probability of finding at least 1 unit with radon ≥ 4.0 pCi/L

  34. Discussion (2) • Future directions • Randomly sample from actual test results for 100% of ground-floor units to test study questions about percentage-based testing using real data • Evaluate appropriate cutoffs for probability to determine how many units need to be tested • Evaluate costs associated with testing • Evaluate assumptions • Ground-floor units being the highest concentrations • Prevalence of radon ≥ 4.0 pCi/L in multifamily homes • Correlation between test results from units next to each other • Clarify what needs to be done once you find a high test result

  35. Acknowledgements EPA • Mike Flynn • David Rowson • Bill Long CDC • Sherri L. Stewart • Mary Puckett • Harlan Austin AARST • Shawn Price • Kyle Hoylman HUD • Warren Friedman • Hilary Atkin

  36. Questions?Antonio Neri, MD, MPHMedical EpidemiologistComprehensive Cancer Control BranchANeri@cdc.gov770-488-3288 For more information please contact Centers for Disease Control and Prevention 1600 Clifton Road NE, Atlanta, GA 30333 Telephone: 1-800-CDC-INFO (232-4636)/TTY: 1-888-232-6348 Visit: www.cdc.gov | Contact CDC at: 1-800-CDC-INFO or www.cdc.gov/info The findings and conclusions in this report are those of the authors and do not necessarily represent the official position of the Centers for Disease Control and Prevention. National Center for Chronic Disease Prevention and Health Promotion Division of Cancer Prevention and Control

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