Geological Influences on Indoor Air Quality and Human Health

Transcription

1 Geological Influences on Indoor Air Quality and Human Health Assoc. Environmental & Engineering Geologists Vapor Intrusion: The Conference Cary, NC, Jan , 2014 Henry Schuver, MS (Geology), DrPH Presented by (does not represent Agency policy): USEPA Office of Resource Conservation & Recovery (ORCR) Wash. DC See: and 1

2 Simple EPA (SF Res.) 1-D CSM Soil-gas/vapor intrusion: Inevitable & Observable* Typical Rn-VI source area Stack effects 4 Mixing in indoor air and inhalation Indoor Air Wind effects Samples: Outdoor Indoor Sub-slab Soil-Gas Groundwater Air streamlines Top of capillary zone Convection Q soil Cracks Contamination L T Contamination 3 2 Building zone of influence Vadose zone Diffusion Advection Diffusion Vapor Source Term Water Table Dissolved chemical Contamination Mod. from slide by M. Bolas, Ohio EPA, presented Jan *Observed exposures are not health protective 1 Phase partitioning C gw to C soil gas 2

3 Intro to Radon (Rn) Agenda Lessons from Rn Research Soil Gas/Vapor Entry & Retention Rn Assessment/Decision making 4 Uses of Radon in Chemical VI (CVI) Relative Tracer of SG/VI (spatial & temporal) N = 86 Key Indicator of Pathway Susceptibility (probability complete ) Risk Driving Co-contaminant Risk Surrogate for Action Health pro-active, Rn-responsive (CVI preemptive ) measures 3

4 Radon (Rn) Rn is a radioactive, colorless, odorless, tasteless (& dense) noble gas, occurring naturally as an indirect decay product of uranium or thorium. Its most stable isotope, 222 Rn, has a half-life of 3.8 days Rn is (the/a*) primary source of ionizing radiation to most people Alpha particles - heavy and limited penetration but High Linear Energy Transfer (e.g., DNA bonds) Rn is in a gaseous form (mobile source of radiation) It is from the radioactive decay of Uranium to Radium (solids) Present in most soil/rock Effective migration distance of Rn is limited by ½-life of 3.8 days (~0.1 in 13 d) Typically Rn-VI source is within a few meters of ground surface Decay of Rn produces a series of relatively short-lived daughters/progeny (solids) ~97% of radiation is from decay of Rn progeny (e.g., from Polonium ( 218 Po) to Lead ( 206 Pb)) These can rapidly attach to particulates in air (e.g., smoke) Rn is easier to measure than the progeny solids & is commonly used as an indicator of all Rnrelated radiation Rn is a constituent found in measurable levels in: Soil gas, Indoor & outdoor air Lungs, blood/bone marrow *due to increasing use of radiation in medical diagnostics 4

5 Lessons from Radon Studies* Observations from 30 years of Radon Study Major institutional research efforts ~ Academics & health scientists continue research to-date Three Approaches to understand Rn intrusion 1-Using Source/Exterior conc. in near-building soil/soil gas to assoc./estimate indoor Rn conc. 2-Using Direct Measurements of Indoor Rn Spatial variability Temporal variability 3 Using Health Effects from Rn Exposures *Draft USEPA technical paper by Dr. Dan Steck (w/ Chris Lutes) 5

6 Source Conc. (> 100x Variation in Rn Exterior Soil Gas to IA Attenuation) Number of observations Soil gas radon (1 m deep) to Indoor Air Attenuation Factor Figure from Rn Lessons. Attenuation factors based on the ratio of long-term basement radon concentration to 1 m deep soil gas radon grab sample concentrations taken next to basements (Steck, 1993, 1996, 2011). 6

7 Source Conc. (> 10,000x Variation in CVI Exterior Sub-Slab to IA Attenuation) Figure A. Box-and-whisker plot showing subslab soil gas CVOC attenuation factor distributions from EPA s vapor intrusion database for individual sites with several buildings per site and subslab soil gas concentrations over 50 times background (U.S. EPA, 2012a) 7

8 Observed Spatial-Variation in Rn Indoor Air (Between Buildings) Median Annual-Average Indoor Radon Conc. & Geometric Std Deviations (GSD) Location Med. Conc. pci/l Numb er - n GSD 68% data range (pci/l) 95% data range (pci/l) US ( ) ~ 10x ( ) = 100x MN ( ) ~ 6x ( ) = 33x County(s) (MN) x 2.9x Town(s) (MN) x 5x Chemical VI site data LAFB, Colo x 7 Indianapolis, IN 4 10 >10x simultaneously Moffett Field, CA 5 20 >10x simultaneously Endicott, NY 6 ~ x 1 Marcinowski et al., 1994; 2 Steck et al., 1996; 3 USEPA, 2012 (VI database); 4 Lutes, 2010; 5 Lee, 2005, 2010; 6 McDonald and Wertz, These are the ranges observed for the limited data available - may not ~95% 8

9 House-to-house Indoor Air Rn conc. distribution in a typical small MN town Figure from EPA s draft Lessons from Radon for Vapor Intrusion Research & Programs by Dr. D. Steck (w/ C. Lutes) Dashed lines show nearly equal probability that individual homes, likely overlying similar Rn sources (in small town), can have ~1 or ~5 pci/l in indoor air. 9

10 Radon workers know Rn-VI is largely about the building 10

11 Radon Studies illustrate the importance of building factors, via changes through time Both man-made + natural changes: Earthquakes, Settling, Drying soils, Burrowing 1-yr samples ~ 1/4x change for Stairwell ~ 5x change for both locations Note, the difficulty of estimating changes in heating or air condition or adding porches; and also impacts to VI. Steck 2007, see: 11

12 * ~100x more atten. in building than in subsurface (Lowry Air Force Base, Colo.) * Extended analysis for rest of EPA VI db showed similar results (by Dr. Wertz) Red & blue added to original slide by Dr. Helen Dawson, from AEHS March

13 Temporal Variation in Indoor Air Hourly (Rn) Windows: Closed, Open Radon (pci/l) Hours Fig. from Lessons from Radon Studies 13

14 Daily Rn Variation Rn (pci/l) Days since 30 June 2003 Fig. from Lessons from Radon Studies 14

15 Seasonal Rn Variation Radon (pci/l) Fall-87 Win-88 Spr-88 Sum-88 Fall-88 Win-89 Spr-89 Sum-89 Fall-89 Win-90 Spr-90 Sum-90 Fall-90 Win-91 Spr-91 Sum-91 Fall-91 Win-92 Spr-92 Sum-92 Season-Year Fig. from Lessons from Radon Studies 15

16 Yearly Rn Variation 8 7 ~ Decade Avg. Radon (pci/l) Year After Construction Fig. from Lessons from Radon Studies 16

17 Rn as Analogy Indoor Air Samples Typical VOC sample duration ~ 4pCi/L Note, highest in spring & fall Rightslink Copyright Clearance License No

18 Continuous Monitoring (ASU) Shows Episodic Peaks Drive CVI Exposure 25 days (3.5%) present more exposure than the other 698 days Dr. Paul Johnson s slide 20/48 - Note audio recording of presentation also available at: 18

19 Summary & EPA-ORD Duplex Summary of ASU & ORD houses Measurement Periods that Contribute to the majority (>50%) of the Total Exposure Sampling Interval ASU (%) ORD 420 (%) ORD 422 (%) 1-day 3 na na 1-week weeks Seasonal Heated side of duplex Date taken from slides AEHS sandconferences/06_truesdale_ pdf Slide 7 of 22, audio also available at: 19

20 Scientific Evidence for the Validity of (short-term) Assessment/Screening Given the high level of temporal variability In a High radon region ~analogous to CVI study areas High prevalence of intrusion near the std FP TP TN FN Appears - Grab sample from log-normal dist. is biased to underestimate long-term risks 20

21 Some Recent Evidence from ASU s Sun Devil Manor house - Radon intrudes in Soil Gas Cautious Conclusions While not a strong indicator of when VI is occurring at this site Note: Log & Linear Scales With a lot of data, radon may tell us that VI can occur at this site 21

22 Some reasons why CVI & Rn Attenuation is not likely to be identical Diff. distribution of chemical & Rn conc. in Sub-Slab (SS) Due to either Differential location of original/primary sources, or Migration to the SS Access to bldg-specific openings Flow/flux through the openings each has access to Mixing in indoor air (at the location & time of sample) Higher Baseline/ background (outdoor) levels/conc. for Rn These are some of the reasons why Rn is not likely to be a precise simultaneous quantitative predictor of Chemical VI (attenuation) 22

23 Slide by Dr. Paul Johnson presented in AEHS March 20, 2012 blue text added Shows variability in SS conc. in both: Space & Time Note, no SS conc.> 5 ppbv; (NJDEP SS matrix level = No Further Action) See 23

24 Summary Observations from Rn & CVI Soil Gas/Vapor Intrusion Studies: 1 - External Source-based est. are unlikely to predict indoor level Only Indoor Air integrates all factors influencing the VI pathway 2 - Indoor measures Vary across Space (e.g., between buildings) Relative to a constant source Primarily due to building-specific-soil interface/contact features 3 - Indoor measures Vary across Time In a given location/building Radom (grab) short-term samples likely to under-est. Long-term avg. conc. without considering Confidence Intervals as safety factors 4 - Rn is unlikely to be quantitatively predictive of CVI For a number of reasons (& CVI is likely to be more variable) But elevated indoor Rn may be useful 24

25 Part 2 How Indoor Rn could be used for CVI Four Uses of indoor Radon in Chemical VI (CVI) 1 - Relative Tracer of SG/VI (spatial & temporal) 2 - Key Indicator of Building-Susceptibility to VI* 3 - Risk Driving Co-contaminant 4 - Risk Surrogate for Action Mitigation responsive to Rn (& preemptive for chemicals) *Elevated Rn is a one-way indicator (showing susceptibility), But: Low indoor Rn (may be due to low Rn source term and) does not provide information regarding a buildings susceptibility to VI

26 Radon as a Relative Tracer for CVI If Radon monitoring is conducted in in multiple buildings and frequently/continuously, it could: Show relative magnitude & pattern of Spatial (& Temporal) variation (across & w/n spec. buildings) Provide a signature of building-specific responses to environmental changes temperature diff., wind, precipitation, barometric pressures,... Could help identify the: Most appropriate (1 st priority) buildings & Best times/conditions» for limited-duration (more-expensive) chemical IA testing 26

27 Indoor-Rn as a Key (3 rd ) step (susceptibility) in Evidence-Basis for Documented Probability of CVI For buildings: 1) Overlying a verified source w/potential for VI Has a VI source term (e.g., GW) > generic screening conc. 2) CVI-COCs detected* in near-surface soil-gas i.e., migrated to near-bldg area & has Possibility to intrude 3) Indoor Rn is elevated (> outdoor) Building(s) are Documented to be permeable/susceptible to nearby soil gas/vapor Intrusion = Documented Probability for a complete CVI pathway Occupants could be expected to reasonably anticipate a more likely than not/probable complete CVI exposure pathway (at some level) Rn can support OSWER public-draft FVIG criteria ( complete ** & PEM) *External conc. are poorly (non-quant.) predictive of indoor conc. **Does not confirm site-cocs in indoor air 27

28 Building-specific Potential & Susceptibility for Chemical VI Overlie Chem- VI source? VI Contam. in Near-Surface Soil-Gas? Documented Rn- VI Permeable building? Y N N Low Y Y N Med. Relative 1 Potential for Chem-VI Y Y Y 3 High 2 1 Relative to the given general source term (e.g., conc.) and subsurface migration potential 2 Documented [Radon &] Possibility & Susceptibility for CVI 28

29 Rn as a Risk-Driving Co-Contaminant: The #1 VI Hazard - Worldwide - Rn There is no known threshold below which radon exposure carries no risk. The lower the radon concentration in a home, the lower the risk. (WHO, 2009) 29

30 Why would WHO, EPA, recommend all homes be tested* for Radon Deaths/yr I was told by the EPA our area levels average 1.8; we tested at 57.2! Designed for homeowner use - 2 channel: 7-d avg. & Up to 5 yr. 8x CanSAR Radon The Voices (2011) Radon (~21,000) Smoke/Fire (~2,580) Carbon Monoxide (~300) Chemical VI (<2**) *Every two years **Personal estimate, assuming no interaction; <0.01 risk of Rn & <0.01 as prevalent as Rn Annual Deaths related to selected Toxic Gases (in US Homes) 70x 30

31 Rn as a Risk-Surrogate for CVI Risk Management Decisions Elevated indoor Rn is a bad sign (3x) for occupants: Rn related cancer(s) risk is elevated beyond avoidable levels Occupants probably subject to avoidable CVI exposures/risks Occupants likely subject to avoidable combined additive/ synergistic risks/effects from both types of toxicants/carcinogens (Rn & COC(s)) Concerns for each increase w/ increasing Rn Rn is used as surrogate for all Rn-related radiation risk 97% of the radiation from is Rn s short-lived progeny (solids/metals) But Rn (gas) levels are easier to measure & shown to be useful enough for estimating Rn-related health outcomes: Rn levels could be a naturally-occurring risk-surrogate CVI 31

32 Bldg-specific Responses for Rn+CVI Combined two(+) contaminant cumulative risk management matrix Building Overlying Chem-VI source? CVI COCs in Near- Surface Soil-Gas? Indoor Rn Conc. in (pci/l) SG/Rn-VI Permeable building? Relative Potential for CVI Y N Low Y Y < 1 Not clear 2 Med. Y Y > 1 (Median US Outdoor = 0.4) Y 3x bad news: 1-Rn exposure 2-Probable CVI 3-Additive / Synergistic? High reasonably anticipated complete pathway of exposure Response Even If Not over CVI Source Goal 3 is Not > Outdoor Rn + CVI Health Beneficial Response Offer SG/VI preventive controls to meet Rn Goal +sidebenefits 1 w/ on-going monitoring 2 Insufficient Rn source? In. Radon Abate. Act >2.0 Consider 4 Mitigation Rn risks >~ 2% 5 >2.7 Mitigate 6 Rn risks >~ 2.7% 4 USEPA 5 Estimated from sub-studies >4 Mitigate Rn risks 6 World Health Organization (USEPA) >~ 4% 32

33 & The Sooner the Better* Removal from Exposure Today Reduces Risks Compared to Continued Exposures Exposure cessation at age 50 halved the hazard, and cessation at age 30 avoided almost all of it Example: Mortality in relation to smoking: 50 years' observations on male British doctors BMJ June 26; 328(7455): Richard Doll, Richard Peto, Jillian Boreham, and Isabelle Sutherland *For disease (and liability) Age Chronic disease, like cancer (shown here) Shorter-term non-cancer disease is even more urgent 33

34 Collateral Benefits of using VI Controls to manage CVI risk Reducing Risk-Driving Cancer* Risks (%) Hypothetical example; Assumed 99% efficiency & 2** pci/l Radon Post mitigation monitoring easier for dominant risk vs. Chem-VI Radon-VI 0 Monitoring Chem-VI Post-Mitigation *Only considering Lung cancer (increasing evidence for leukemia & other diseases) **Assumed typical 2 pci/l level, & general population risk (based on sub-studies, ~2x bulk) 34 Assumed (even though atypical) chemical VI cancer risk = 1x10-4

35 Summary Soil gas/vapor intrusion (into indoor air) is: Inevitable (under natural, un-mitigated conditions) Radon is a naturally-occurring Geologic Risk & general tracer of all soil gas intrusion Four Uses of indoor Radon in Chemical VI (CVI) 1 - Relative Tracer of SG/VI (spatial & temporal) 2 - Key Indicator of VI Susceptibility (Prob. of complete ) 3 - Risk Driving Co-contaminant 4 - Risk Surrogate for Action Mitigation responsive to Rn (& preemptive for chemicals) 35