What is the Evidence for Long Term Stewardship (LTS)

Transcription

1 What is the Evidence for Long Term Stewardship (LTS) (vs. Stopping All Monitoring (SAM)) for the Vapor Intrusion Pathway?* For EnviroForensics & Barnes and Thornburg Webinar Nov. 19, 2014 by Henry J. Schuver, MS (Geology) DrPH (Epi) USEPA, ORCR, Wash. DC A Personal Public Health Perspective Does not Imply Agency Policy See: and *Follows and evolved from: AWMA VI 2012 (MNA); AEHS EPA Workshop 2014 (LTS as context); Battelle 2014 (comparison to other pathways/policies LTS) & AWMA VI

2 Agenda Introduction Definitions Threshold criteria for LTS Data/evidence from: Chemical VI Radon VI Analogous (evidence based) Polices Conclusions 2

3 Does this (simple) Conceptual Site Model [w/ variable categories 1 6] support LTS or Stopping All Monitoring (SAM)? Wind effects 4 3 Stack effects Rn source Mixing in indoor air and inhalation Indoor Air Low Chlorin. Chem. Vapor Source Term Air streamlines Top of capillary zone Water Table Convection Q soil Cracks 3 Contamination 2c L T Contamination Dissolved Contamination 2b 2a Building zone of influence Vadose zone Mod. from slide by M. Bolas, Ohio EPA, presented Jan Diffusion Advection Diffusion Phase partitioning C gw to C soil gas 5 Improving Assess. Methods & RE Sales 6 Changing Tox., Exposure Durations & Conc.

4 What is Long Term Stewardship (LTS)? 1 LTS applies to sites where long term management of contaminated environmental media is necessary to protect human health 1, Long Term Stewardship: Ensuring Environmental Site cleanup Remain Protective Over Time 4

5 What is SAM? Stop All Monitoring * Most conventional VI monitoring is for an: Anticipated Limited duration Assessment i.e., That can be used to Predict the future VI & if Predict < std Screen out (& never look back) Does evidence support the presumed goal of Stopping All* Monitoring (while VI source remains)? *All = across All buildings (space) and All time 5

6 LTS Threshold Criteria #1 1) Do VI sites have contamination remaining YES VI sites are defined by the extent of contamination Buildings of concern for VI, are: Overlying/proximate to vapor forming contamination i.e., VI Source Media Conc. > generic screening values* So there is a Potential for inappropriate (VI) exposures *e.g., > USEPA Regional Screening Levels (aka PRGs) based on empirical atten. data 6

7 Vapor Intrusion Defined by Source Source definition is a challenge most of this plume found by indoor air DCE Dichloroethylene Growing Awareness of Subsurface Vapor Sources Especially in Non Drinking Water Areas If you look for low enough concentrations (DCE is unique tracer of Groundwater) Proximity to a source appears to determine its presence in indoor air ( complete VI pathway)

8 LTS Threshold Criteria #2 2) Is the management of contaminated environmental media necessary to protect human health? YES Exposure factors (~10:1) Levels measured (e.g., up to ~2,000 ug/m3); Combined with: Typical toxicology (lab animal) based estimates of Risks Correlations with human disease patterns 8

9 Do Disease Assoc. Support LTS or SAM?.. TCE plume (70 block) area: ~2615 residents, 1090 births ( 78 02) 248 effects ~ ~ 1/4 117 Small for gestational age RR = 1.23 (95% CI = ) 76 Low birth weight RR = 1.36 (95% CI = ) Conclusions: Maternal residence in both areas was associated with cardiac defects. Residence in the TCE area, but not the PCE area, was associated with low birth weight and fetal growth restriction. 37 Term low birth weight RR = 1.68 (95% CI = ) 15 Cardiac defects RR = 2.15 (95% CI = ) 1. How many other comm. (< #)? 2. Short term exp. concerns are real 3 Conotruncal** defects RR = 4.91 (95% CI = ) * Also a similar paper on increases in adult cancers Week 3: days from fertilization Primitive heart tube is forming ** abnormal formation of the outflow tracts of the heart and begins to beat in a regular rhythm. (RR) Rate Ratios relative to the rest of NY state (excluding NYC) Week 4: days from fertilization The heart bulges, further develops,

10 LTS Threshold Criteria #3 3) Are LTS activities necessary to ensure that these sites remain [over the long term ] protective of human health and the environment. YES VI sources are often long lasting (GW plumes) VI is unpredictably variable over time* both w/n: Short term (~current conditions [say < 90 days]) Long term (future conditions [say >90 days to 30 years] 10

11 Episodic Peaks Drive Exposure Support SAM? 25 days (3.5%) present more exposure than the other 698 days Chemical VI (TCE) at ASU s Sun Devil Manor 1. VI is variable in this house 2. Peaks drive (chronic) exposure Dr. Paul Johnson s slide 20/48 Note audio recording of presentation also available at: pdf 11

12 Some data from USEPA ORD s VI Research House with ~similarly Episodic behavior support SAM? Heated side of duplex 1. VI is variable in this house 2. Peaks drive (chronic) exposure Slide 7 of 22, audio also available at: pdf 12

13 Is (simpler )* Radon Intrusion Episodic? Looks to be in this Swedish home w/ unusual 1 day samples 1. Rn VI is variable in this house * w/ a more constant & closer source, than most Chemical VI (e.g. ASU & ORD) Do these daily samples support SAM? Note, highest often not in winter 13

14 Is Radon* Intrusion Episodic? Same MN home w/ Hourly, 2, 7, & 90 day (& yearly) samples * w/ a simpler, more constant & closer source, than most Chemical VI) 1. Rn VI is variable in this house Do these samples support Stopping all Monitoring? Would two samples from Winter help? 14

15 Do these 1 yr samples support Stopping all Monitoring, after _ yrs? 8 7 >4x variation in 17 years Radon (pci/l) Even 1 yr. long sample Year After Construction results are variable Fig. from Steck in draft Lessons from Radon Studies 15

16 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 4) Occupants/Operation 5) Natural changes 6) Man made changes 16

17 Who thinks EPA s VI db (GW) supports Stopping All Monitoring? >100,000x variability, Includes both: Space (24 sites) & Time** **Using a few (short term) Indoor Air samples per building 17

18 Does >10,000x* Variation in Sub Slab to Indoor Air (w/n building) Attenuation supports SAM? *Variability, Includes both: Space (12 sites) & Time** 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) **Using a few (short term) Indoor Air samples per building 18

19 * ~100x More atten. in building than in subsurface Does this Support SAM? (Lowry Air Force Base, Colo.) * Extended medians 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

20 Occupant Operations Hourly Rn Variation Windows: Closed, Open Does this Support SAM? Radon (pci/l) ~ 5x factor Hours Fig. from Lessons from Radon Studies EPA Rn testing procedures recommend Closed house conditions How many Chem. VI investigations/datasets do? 20

21 Do Radon Studies illustrating effects of changes in building structural factors Support SAM? 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: 21

22 Do evidence based Policies for (simpler ) Radon support SAM? NO USEPA (NAS based) policy (1993) recommends: Sample every home (across space) Re sample every 2 years (across time) Sample for a minimum of 2 diurnal cycles 48 hours 22

23 Policy Allowing Natural Attenuation to be part of (GW & Soil) Remedies Monitored Natural Attenuation (MNA, EPA 1999)* A major policy to allow & ensure natural processes are safe With adequate monitoring of a natural attenuation remedy to ensure with a high degree of confidence that potential receptors will not be impacted Is not a no action or walk away remedy MNA is effectively: On going assessment to ensure on going protection *OSWER Dir P for CERCLA, RCRA, UST

24 NRC panel/report on managing complex GW sites* support SAM? Panel reported increasing use of controls that would of course include continued groundwater monitoring to be sure there would be no inappropriate exposures And when asked (in Q/A**) If that included on going monitoring for VI it was Agreed it would So: No, NRC does Not support SAM for VI» i.e., VI is one pathway assoc. w/ GW plumes & needs LTS 24 * Alternatives for Managing the Nation s Complex Contaminated Groundwater Sites, NRC 2012 ( ** Battelle Chlorinated Remed. Conf. 2014

25 In Summary Vapor Intrusion meets: The three threshold criteria for Long Term Stewardship Contamination remains (proximate to receptors) Management is needed to Protect human health Management/activities are needed over the long term Given the nature & scale of changes possible: LTS is as appropriate (for VI), or even more so Than for any other (current) pathway for exposure 25

26 While VI Contamination Remains & for GW plume sources could be 20, 30, even 50 +? years Be a Good Steward Ensuring no* (VI) Exposures e.g.,» On Going Monitoring at an frequency appropriate for the: Shortest exposure durations of concern Variability of intrusion (incl. episodic peaks) Concentration & Mass of Contamination remaining; Or» Ongoing Prevention/Control of exposures [needs separate discussion] Not acting as if the goal is to Stop All Monitoring** which: Relies on Un Monitored Natural (vapor) Attenuation As the only protection *inappropriate **Is there any, or a even a simple majority, or 95% of, evidence to support that? 26

27 Acknowledgements To those who have designed &/or collected some of the most important (& highest quality) evidence for assessing/managing VI risks: D. Steck P. Johnson B. Schumacher C. Lutes C. Holton T. McAlary, H. Dawson, W. Wertz, I. Hers 27