FSN 1500 Week 10

1. FSN 1500 Week 10 Indoor Air Quality

2. Foreword • The quality of the air we breathe is both a personal health and a major economic issue • Most people don’t consider how vital the quality of their indoor air is to their health, so today we’ll focus on some important indoor air quality concerns

3. Indoor Air Quality • The average Westerner spends about 90% of their life indoors! • Studies have shown that indoor air may be 10 - 100 times more polluted than outdoor air!

4. Indoor Air Quality • Some indoor air quality concerns include: radon, the combustion pollutants and asbestos.

5. Indoor Air Quality (Radon) • Radon - colorless, odorless, radioactive gas formed by the radioactive transformation of uranium in soil and rock. • 238U ---> 222Rn + heat + 4 4 He (alpha particles) (see next slide)

6. Example of Radioactive Decay http://www.ndt-ed.org/EducationResources/HighSchool/Radiography/radioactivedecay.htm

7. Indoor Air Quality (Radon) • Radon gas has a natural tendency to seep upward through cracks in rocks and soil pore spaces; it may even rise as a dissolved gas in groundwater • Radon enters a dwelling through cracks in the foundation or concrete slab, through porous construction materials (e.g., concrete), through uncapped sumps and floor drains and through gaps between utilities and the structure’s walls and floors (see figure) • The uranium content in soils and rocks and the amount of radon released does vary

9. Indoor Air Quality (Radon) • However, nearly every rock and soil type emits some level of radon so every structure contains some level of radon • The U.S. Environmental Protection Agency (EPA) and the American Lung Association contend that moderate to long-term exposure to elevated levels of indoor radon and its radioactive byproducts is the second-leading cause of lung cancer

10. Indoor Air Quality (Radon) • According to the EPA and the U.S. National Cancer Institute, cigarette smoking is responsible for approximately 85% of lung cancer cases and prolonged exposure to radon and its byproducts is responsible for approximately 10% of lung cancer cases

11. Indoor Air Quality (Radon) • How could radon or its byproducts induce lung cancer? The key concern is the alpha particles and their potential to mutate the DNA of the lung wall cells. • The alpha particle is not very energetic; its penetration power is not great - even a few centimeters of air dampens its energy significantly (see figure)

12. Penetration energies of different types of nuclear radiation

13. Indoor Air Quality (Radon) • However, if the alpha particle gets released into our lung cavity, some alpha particles may have enough energy to penetrate the first few millimeters of the lung wall and cause mutations in these cells • When the radon gas enters our dwellings it mixes well with the other air gases; when you inhale you could be inhaling some radon atoms

14. Indoor Air Quality (Radon) • What’s the chance of a radon atom undergoing radioactive decomposition and releasing an alpha particle while in your lungs? For the average adult only about a 1 in 15,000 chance! • Why so low a chance? We need to examine the residence time of the radon in the lungs and its half-life.

15. Indoor Air Quality (Radon) • Most of any adult’s inhalation gases only reside in the lungs about 30 seconds before they’re exhaled or absorbed • Half-life: the time it takes one half of a substance’s atoms to radioactively transform • The measured half-life of radon is about 3.8 days

16. Indoor Air Quality (Radon) • The 1 in 15,000 chance I mentioned earlier results from the short residence time of the radon in the lungs compared to the significantly longer radon half-life • So why the concern over radon exposure possibly inducing lung cancer? • The key: radon decomposes to two radioactive solids - polonium-218 and polonium-214

17. Indoor Air Quality (Radon) • Polonium-218 and polonium-214 have a tendency to adhere to aerosols (e.g., dust and smoke particles) and be drawn into the lungs • Polonium-218 has a half-life of about 3 minutes, polonium-214 half-life is even shorter; these elements decompose by emitting an alpha particle

18. Indoor Air Quality (Radon) • The lung residence time for aerosols in the average adult is 30 minutes. Comparing the residence time and polonium half-lives, is it likely that alpha particles will be released into the lung wall? • Inexpensive, fairly accurate tests have been developed to measure air radon levels but not polonium levels; we assume the higher the air radon level the higher the polonium levels

19. Indoor Air Quality (Radon) • Indoor air radon levels are typically measured in units of picoCuries per liter (pCi/L); the picoCurie is a measure of radioactivity, the liter a measure of air volume • 1 pCi/L corresponds to 133 radon atom disintegrations in 1 liter of air in 1 hour

20. Indoor Air Quality (Radon) • The U.S. EPA and other health agencies suggest that structures with levels at 4 pCi/L or greater have remediation work conducted • The World Health Organization’s action level for remediation is 2 pCi/L • The following tables illustrate the relative death risks for nonsmokers and smokers from long-term radon exposure

23. Indoor Air Quality (Radon) • Indoor air radon levels as high as 3500 pCi/L have been measured; the outdoor average level is 0.2 – 0.4 pCi/L • All indoor air pollution risks (not just radon) are increased when we live under “closed house” (windows and doors sealed tightly and doors infrequently opened) conditions (i.e., winter, portions of spring and fall)

24. Indoor Air Quality (Radon) • The radon lung cancer risk is further enhanced if significant aerosol production occurs within the dwelling • If your structure contained elevated radon levels, how could you possibly reduce these levels? • Two broad approaches: 1) improve cross-ventilation by natural or artificial means (e.g., sub-slab suction)

25. Indoor Air Quality (Radon) • 2) Seal or cover the radon entryways as effectively as possible (e.g., caulking, application of gas-impermeable paints, installation of water permeable/gas impermeable sump and floor drains) • There are also preconstruction radon mitigation techniques which can be employed (see figure for summary)

26. A = bed of permeable gravel (preconstruction) B = gas impermeable sheeting (preconstruction) C = caulk cracks and utility openings (usually post construction) D = Sub-slab ventilation pipe (usually post construction) E = ventilation fan

27. Indoor Air Quality (Radon) • A dozen or so states now require indoor air radon testing to be conducted before any commercial or residential structure is sold. • How is this issue affected by Michigan's (mid-1990s) enacted real estate transfer disclosure statement? • Be forewarned: there is still much controversy, perhaps unresolvable, concerning what radon and radon byproduct exposure levels are necessary to significantly increase lung cancer risk.

28. Indoor Air Quality (Radon) • Why the controversy? The only actual human data we have is from studies of underground uranium miners, typically exposed to higher radon and radon byproduct levels for longer periods than the average adult • There is definitely a linear (positive) relationship between radon exposure and lung cancer incidence for underground uranium miners

29. Indoor Air Quality (Radon) • Can the risk relationship be linearly extrapolated to lower exposure levels and times to establish the lung cancer risk for the general population? The U.S. EPA thinks this is a valid approach - it employs what is called a “linear” dose-response model (see figure)

30. Actual Data Response Linear Model (Lung Cancer Incidence) Threshold Model Dose (Radon/Byproduct Exposure)

31. Indoor Air Quality (Radon) • Some groups have argued that the appropriate dose-response model is the “threshold” model (see previous figure); this suggests the lung cancer risk wouldn’t increase until a certain, somewhat elevated combination of radon level and exposure time was exceeded. • Why may we never be able to answer which model is more appropriate? Why should we care?

32. Indoor Air Quality (Radon) • Broadly: we will likely never have the clinical data to conclusively decide whether the linear or threshold dose-response model is more appropriate - yet we must try to make risk assessments for substance exposures! • This issue illustrates the political and economic aspects of science and how the layperson could be mislead (see figures)

33. Detroit News 3/19/93

35. Indoor Air Quality (Radon) • In 1998 the U.S. National Cancer Institute scientists published a report that evaluated eight previous studies on over 10,000 people in five countries • Using a linear model approach, they estimated a 14% increased chance of lung cancer for a person living in a residence for 30 years that has air radon levels of 4 pCi/L

36. Indoor Air Quality (Radon) • What’s the status of the indoor air radon problem in Michigan? There are definitely “geographic hot spots” where elevated levels of indoor radon have been measured • See the following figures - more detailed information is available from the state (Department of Natural Resources), federal government (EPA) and the American Lung Association

38. Michigan Radon Potential Map High Potential > 4 pCi/L Moderate Potential 2-4 pCi/L < 2 pCi/L Low Potential Source: U.S. EPA, 2005

39. Indoor Air Quality (Radon) • While the U.S. EPA and U.S. Geological Survey suggest that only 6% of U.S. households host air radon levels > 4 pCi/L; note from the previous slides and your handout that some geographic regions may have a much higher percentage of households whose air radon levels exceed 4 pCi/L

40. Indoor Air Quality (Radon) • Short-term (days) and long-term (months) air radon test kits are available; make sure the kits are EPA approved • A very good long-term (90 days to year) test kit: Accustar Alpha Track AT 100 (~$20 and available at Amazon.com)

41. Indoor Air Quality (Combustion Pollutants) • Combustion Pollutants - air pollutants resulting when fossil fuels or other carbon-containing fuels, or volatile organic compounds, are inadequately combusted (e.g., not enough oxygen present) or the combustion gases are insufficiently vented • Major sources: wood stoves, fireplaces, coal stoves, gas appliances (water heaters, cooking ranges, clothes dryers, kerosene heaters, camping cook stoves) • Example: 2 C(s) + O2(g)  2 CO(9) (carbon monoxide)

42. Indoor Air Quality (Combustion Pollutants) • Carbon monoxide (CO) - short term, the most dangerous of the combustion pollutants; about 1100 people in the U.S., on the average, die each year from accidental CO poisoning (early 1990’s Journal of the American Medical Association report) • CO bonds about 250 times more effectively than oxygen to the hemoglobin molecule in your blood; the oxygen starvation to your organs can result in death!

43. Indoor Air Quality (Combustion Pollutants) • CO is a colorless, odorless gas; for the average adult, exposure to 400 ppm (parts per million) concentrations of CO for two hours results in death • Be aware of low-level CO exposure symptoms: flu-like symptoms, disorientation, headaches, fatigue • The early March 2002 deaths of five people in a Lapeer County residence should illustrate the importance of this topic

44. Indoor Air Quality (Combustion Pollutants) • Health agencies suggest each home have one or more CO monitors; the monitors are available in two types: passive and active • Passive monitors require no power source (battery or electrical cord) and typically consist of a small, mountable disk whose surface changes color as CO gases of different concentrations pass over the disk (see figure)

46. Indoor Air Quality (Combustion Pollutants) • Although passive monitors are cheap, they are useless unless you are visually monitoring them • Active monitors are available that use a battery, electrical cord, or both, power source • See handout (and figures), some very good active monitors are now available for sale

48. Indoor Air Quality (Combustion Pollutants) • The most versatile active CO monitors have two power sources (electrical and battery backup) and provide a digital readout of CO levels (see figure)

49. Indoor Air Quality (Combustion Pollutants) • Why would health and safety officials urge that all electrically powered CO detectors be equipped with a backup battery? (see figure)

50. 12/18/2006