Indoor Radon as an Option for Sustainable On going Screening/Monitoring of Short Term Risks from Low/Episodic Chlorinated Vapor Intrusion

Transcription

1 Indoor Radon as an Option for Sustainable On going Screening/Monitoring of Short Term Risks from Low/Episodic Chlorinated Vapor Intrusion Battelle 2015 Bioremediation & Sustainable Tech. Vapor Intrusion Session Miami, FL May 19, 2015 Presented by Henry Schuver*, DrPH (Epi), MS (Geology) & D. Steck, B. Schumacher, C. Lutes, & R. Truesdale *USEPA Office of Resource Conservation & Recovery (ORCR) Wash. DC *Personal Perspective Does not represent Agency policy See: and The views expressed in this presentation are those of the author and do not necessarily reflect the views or policies of the U.S. Environmental Protection Agency. 1

2 If you sample indoor air for chemicals; How do know if you sampled the right: Building Time & Not getting chemicals from indoor sources? Growing evidence that Radon is a Tool: To help address these questions & Reduces the need for indoor chemical sampling & Can provide lower cost evidence of protection 2

3 Radon is a small but most important part of this Conceptual Site Model of Soil Gas Intrusion [w/ Categories of variables 1 6 for Chlorinated VOC VI (CVI)] Typical chemical Samples: Outdoor Indoor Sub-slab Soil-Gas Groundwater Air streamlines Top of capillary zone Wind effects Convection Q soil 4 Indoor Air 3 Cracks Rn & CVOC 3 CVOC contamination L T CVOC contamination Stack effects 2b Radon (Rn) Source Building zone of influence Vadose zone Diffusion Mixing in indoor air and inhalation Advection Diffusion CVOC Source Term Water Table Dissolved CVOC contamination 2a Mod. from slide by M. Bolas, Ohio EPA, presented Jan Phase partitioning C gw to C soil gas 5 Improving Assess. Methods. 6 Changing Tox., Exposure Durations of Concern 3

4 Fundamental Challenge for Chlorinated Vapor Intrusion (CVI) Assessment Unpredictable Variation across: Space (buildings) Time* Challenge enough for long term chronic risks Only heightened by (now recognized) Short term exposure risks (e.g., for TCE) The interval for averaging peaks is now shorter and Peak avg. can more easily exceed thresholds of concern Period of concern for short term events is Long term* * for As Long as (vapor) Source Remains (ALSR), ~similar to GW ingestion risks (NRC 2012) 4

5 Some new Options are Needed Particularly for more Fully addressing Spatial & Temporal variation Current Conventional CVI assessments take limited, but typically extended* amounts of time Seeking permanent walk away decisions ( SAM **) Based on high certainty samples looking for worst case conditions to allow Predictions [for all future cond.] 1) Predictions are impractical for the simpler and more constant Radon pathway (even for long term risks) 2) 2) For short term*** effects extended study can be a public health issue [ORCR Immediate Office comment] *Relative to the (short term) exposure periods of concern **Stopping All Monitoring (SAM) see Schuver AWMA 2014 at ***e.g., Developmental effects on fetus from TCE (heart, 2 weeks 1 day?) 5

6 Screening Option 1. Result Exposed Ideal Screening. Media/Location Indoor Air (exposure point) % of Exposure Pt. (Bldg.) covered 100% of occupied buildings Parameters/Analytes Site specific CVOC COCs % time covered by samples 100% / Continuous Duration of samples Frequency (/intervals between samples) Time to results (for responses) Immediate Real time Confidence Positive Screen In (c/st)* 100% / 100% Catch all problems as Positives & no errors (0 False Positives) Confidence Negative Screen Out* 100% / 100% ID all non problems as Negatives & no errors (0 False Negatives) Overall duration of Monitoring As Long As Source Remains (ALSR) Cost 0$ (currently High ($$$$$$$$$)) Not Exposed Positive 0 100% Negative 100% 0 * (c/st) = for Chronic/Short Term risks 6

7 Ideal & Conventional Options & their Downsides Characteristic #1 Ideal Downsides of Ideal #2 Conventional Downsides Of Conventional Media/Location Indoor Air Backg.& access Indoor Air Background &access % Building tested 100% Costs & access 15% Too few Bldgs. Para./Analytes Site COCs Analysis cost Site COCs Analysis cost % time sampled 100% Not practical 1% Missing peaks Sample Duration & Frequency Continuous Not Practical 1out of 90 days Unlikely to catch episodic peaks Time b4 results Real time (0 d) Not Practical ~90 days > Exposure duration Screen In*(c st) 100% 100% Not feasible <40%** <<40% Too Ineffective Screen Out*(c st) 100% 100% Not feasible >95%? 99% High False Neg. %? Total Duration of monitoring As Long as Source Remain High Costs 1 year (Four 1 d samples) Must predict future & no evidence it can Cost/bldg. $$$$$$$$$ Too High/bldg. Not Realistic $$$$$$ Moderated cost by adj. # Bldgs. & Freq. *Sensitivity (TP/(TP+FN)), Specificity (TN/(TN+FP)) per bldg. for Chronic &Short Term risks (c st) 7 **Interpretation from Holton et al., 2013 for chronic risk (for long term avg. exposures)

8 Objective for Option #3 (Hybrid) Decreasing the Downsides Characteristic Downsides of #1 (Ideal) Downsides of #2 (Conventional) Objectives for Option #3 (Hybrid of #1 & #2) Media/Location Backg. & access Background & access No Backg./access issue % Bldgs. Costs & access Too few Bldgs. but still cost & access ~100% possible w/ Lower costs & access? Para./Analytes Analysis cost Analysis cost Lower Analysis Cost* % Time sampled Not practical Missing peaks ~100% if feasible/pract. Sample Duration & Frequency Not Practical May not catch episodic peaks ~Continuous to catch episodic peaks Time b4 results Not Practical > Exposure duration ~ Real time (0 days) Sensitivity*(c/nc) Not feasible Too low/ineffective Higher e.g., >95%/>95% Specificity*(c/nc) Not feasible High False Neg. % Retain High level Total Duration of monitoring High Costs Needs to predict future no evidence Make As Long as (VI) Source Remains possible Cost/bldg. Too High & Not Realistic Moderate by adjusting # Bldgs. & Frequency Lowest over all possible *e.g., by fewer samples analyzed for PRP/source specific (& high cost) CVOCs 8

9 How can the Hybrid meet such Objectives? Make On Going Screening/Monitoring practical by: Only screening/monitoring for now (current conditions) Not needing to make predictions for all future time Not intended for screening out forever (all future conditions)* Approach the Ideal option while still being practical by: Breaking into Two ( rapid & practical/sustainable) Steps*: 1) Initial Priority Screening to ID more likely CVI Not Certainty* Basic physical indicator parameters/metrics of Soil Gas Intrusion (e.g., pressures, Radon, etc.) High coverage across both Space (buildings) & Time 2) Focus More confident Monitoring for more likely CVI *(i.e., more realistic, not trying to go directly from Potential to high Certainty ) 9

10 These Concepts are Based On Decades of Observations & Studies Intrusion of Chemical Vapors Naturally occurring tracers of soil gas movement [Radon (Rn)] Recent simultaneous Radon (Rn) and Chemical Vapors* Despite their many similarities/relationships Radon has not been well integrated into CVI work Has seen limited application in a wide variety of buildings Further testing and verification of these methods is warranted Intent here is to raise awareness of opportunities to Use these methods (Option #3 Hybrid) Def. of Hybrid Elements from both but closer to Ideal than Conventional *ASU Manor, EPA ORD Indy, Wheeler Bldg., EPA R9 studies 10

11 Radon (Rn) is component of soil gas: Widespread, at some level, in ~all soils From a solid, non mobile source (radium cont. minerals) A~ constant source concentration & release rate Intrudes from soils near (typically w/n ~1m of) the building Not complicated/made more variable by factors at > depths Acknowledged to be analogous to CVI near building* Some differences, e.g., source, depth, distribution entry listed** Easily measured in indoor air, & at a low cost Even ~ continuously, & by the occupants themselves Lower concerns for indoor background for Rn (than for chemicals) Much higher risk for (adult) cancer than from CVI But is less threatening to occupants than CVI *Mosley 2004; 2007; McHugh 2008 **Schuver & Mosley

12 Unlike CVOCs: Radon has a ~constant source rate & (short) half life. Not produced or removed at same rate as CVOCs; Can behave similarly, but: Do Not expect to see a Simple exact quantitative magnitude of concentrations (surrogate) relationship between Rn & CVOCs Atomic Decay Radon is only an Indicator* of most (lung cancer) risk (97%) from particulates *Easier to Measure & Cost Effective Analogy for CVOC risk 12 From: Samet JM: Indoor radon and lung cancer Estimating the risks. West J Med 1992 Jan; 156:25 29

13 Very Importantly (1) Rn & CV share the most important portions of the intrusion pathway Building factors As influenced by Intrusion Driving Forces/Climate Including nearby Soils & Soil Gas behavior Suggested use of Indoor Radon (Rn): Tracer of soil gas intrusion Indicator* for possible similar behavior by chemical vapors * Cost Effective 13

14 Attenuation & Importance of Building (using Chemical data) Building Attenuation (incl. Driving Forces & adj. Soils) SS IA (1000) Subsurface Attenuation GW SS (10) median (Dawson 2011)* In the Building In the Subsurface *Also observable in EPA s entire VI database where range of Atten. from GW IA is 10 5 and from SS IA (in the building) is 10 4 [i.e., 4/5 OOM due to attenuation in the Building]

15 Do differences & changes in Buildings support Stopping All Monitoring? 1) Design Ground contact Heating type, HVAC Height, elevation, orientation Vegetation surrounding? 2) Construction 3) Condition Radon reflects ALL pathways, including alt. / anthropogenic 4) Occupants/Operation 5) Natural changes 6) Man made changes See: What is the Evidence for Stopping All Monitoring for VI? (Sept. 10) What is the Evidence for LTS vs. Stopping All Monitoring (SAM)? (Nov. 19) 15

16 Proposal: Elevated* Indoor Rn levels can be used to: Address Spatial variability Can Illustrate if soil gas is intruding into a Building* i.e., If the Building is susceptible to intrusion, by: Soil Gas (as indicated by the Radon tracer) & By possibly similar behavior by Chemical vapors e.g., If CVOCs were present in the near building soil gas Could help decide Where to collect CVOC samples Which Buildings to prioritize/focus on *Radon evident, clearest if indoor Rn is elevated; However, if indoor Rn levels are NOT elevated, but Rn in soil gas is could show building is not susceptible to intrusion (an evolving possible screen out (for now) concept) to be discussed further 16

17 Scientific evidence for Radon as indicator for Spatial variability in CVI Randomized Experiment on Radon Tracer Screening for Vapor Intrusion in a Renovated Historical Building Complex (internal EPA draft) C. Lutes, R. Uppencamp, L. Abreu, R. Mosley, D. Greenwell 50 locations screened for radon Two subsets Randomly selected units Higher radon guided units The upstairs radon guided samples were significantly higher in trichloroethene (TCE) than the randomly selected locations. 17

18 Some Temporal Evidence from ASU s Sun Devil Manor Radon intrudes in Soil Gas ~~ w/ TCE Differences; but similar behavior under natural conditions Different Units, Scales, & Baselines, but: data from under Naturally varying conditions Visually apparent general relationship Not simply magnitude of concentrations General assoc. of behavior Consistent w/ two components of same soil gas (not in identical conc. or distributions) but behaving similarly to VI pathway forces Temporal Variation pdf 18

19 ASU s Sun Devil Manor house But TCE & Rn also appear to change together 2015 EPA Workshop (slides & audio Available at: Under Controlled conditions 19

20 EPA ORD Indy house (~20 days w/o active or passive mitigation, over 4 months) Chloroform & Radon (Rn) appearing to change together Under mixed natural & controlled conditions Some evidence from EPA ORD Indy house (Schumacher et al., 2015 internal draft) 20

21 Change in Rn as Predictor of CVOCs in Time Series Regression (over ~28 weeks*) Basement Office In both locations Change in Rn *Weekly samples including the time covered by those from every 2 hrs. in previous slide 21 From EPA ORD Indy house (U.S. EPA (2015) EPA/600/R 14/397)

22 Proposed Options for Initial Screening (& On going) Monitoring for Potential CVI st Ideal Conventional Hybrid Screening More Ideal than Conventional CVOCs Indoors 100% bldgs & 100% time Under natural or controlled conditions? CVOCs Indoors Few bldgs. & Few times ~100% Bldgs & ~100% Time, but for only a: Tracer of Soil Gas (Indoor Radon) intrusion & Indicator for elevated potential for complete pathway for CVI exposure No* No Is nearby Soil Gas [Rn] Intruding? Yes (if indoor Rn is > 3 5x outdoor levels)* Are CVOCs in** near bldg. Soil Gas? Yes = Potentially Compete CVI st Pathway (bldg) To know more; CVI specific Monitoring is needed (& Rn) * If Rn Not elevated in Indoor Air, but Is in Soil Gas, then building ~not susceptible at this time Could continue to use radon to Monitor building s susceptibility to SG intrusion? **Detection (w/ MDL ~ IA targets) as there is No evidence for a quantitative relationship 22 between exterior soil gas & indoor air conc. (at this time)

23 Benefits of Measuring Radon Baseline understanding of buildings intrusion susceptibility and range of variation To select higher priority buildings for chemical sampling To select higher priority times for chemical sampling (by increasing Rn just prior to, & predicted weather?) If simultaneous with chemical sampling Can interpret chemical results as: Being from building s higher, or lower, intrusion period Evidence of being due to background (if low Rn intrusion) In summary, we are Developing the evidence base to reduce the need for chemical sampling (while providing lower cost evidence of protection) 23

24 Acknowledgements To those who have designed &/or collected some of the most important (& highest quality) evidence for assessing/managing VI risks: D. Steck & R. Mosely P. Johnson & C. Holton B. Schumacher, C. Lutes, B. Cosky, & R. Norberg H. Dawson & W. Wertz 24