Developing-Draft … Still Learning from Rn, & now we’d like to use it Indoor Radon as an Option

for On-going Screening/Monitoring of Short-Term Risks from Episodic Chemical Vapor Intrusion*

2014 International Radon Symposium (AARST) Charleston, SC – Sept. 30

Presented by Henry Schuver, DrPH (Epi), MS (Geology) USEPA – Office of Resource Conservation & Recovery (ORCR) Wash. DC

Personal perspective by (does not represent Agency policy)

See: http://iavi.rti.org and http://epa.gov/oswer/vaporintrusion

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*Follows & evolved from: AWMA VI 2012 (MNA); AEHS EPA-Workshop 2014 (LTS as context); Battelle 2014 (LTS comparison to other pathways/policies); & AWMA VI 2014 – What is the Evidence for Stopping All Monitoring – of the VI pathway? - [for Recalcitrant vapors]

Chemical Vapor Intrusion ‘Potential’ Defined by Source Area

Growing Awareness of Subsurface Vapor Sources - Especially in Non Drinking Water Aquifers 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 (‘completeness’)

DCE – Dichloroethylene

Source definition can be a challenge - most of this plume found by indoor air

Indoor Radon is the ‘simplest’ part of this Conceptual Site Model of Soil-Gas Intrusion

[as an Outline of categories of variables 1-6]

Dissolved Contamination

LT Diffusion

Vadose zone

Building zone of influence

Wind effects

Indoor Air

CracksQsoil

Air streamlines

Convection

Top of capillary zone

Water Table

Stack effects

Mixing in indoor air and inhalation

Advection

Diffusion

Phase partitioningCgw to Csoil gas

Mod. from slide by M. Bolas, Ohio EPA, presented Jan. 2006

Vapor Source Term

Contamination

Contamination

Typical Samples:

Outdoor

Indoor

Sub-slab

Soil-Gas

Groundwater

1

2b

2a

2c

3

4

5 Improving Assess. Methods. 6 Changing Tox., Exposure Durations & Conc.

Rn source

3

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Is Radon* Intrusion Episodic?Same MN home w/ Hourly, 2-, 7-, & 90-day & yearly samples

Do these samples support Stopping all Monitoring?

* w/ a simpler, more constant & closer source, than most Chemical VI)

Would two samples from Winter help?

Do these 1-yr samples supportStopping All Monitoring, after _ yrs?

5

0

1

2

3

4

5

6

7

8

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22

Rado

n (p

Ci/L

)

Year After Construction

Fig. from Steck in draft Lessons from Radon Studies …

>4x variation in 17 years

Episodic Peaks Drive Exposure – Support SAM*?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:https://iavi.rti.org/attachments/WorkshopsAndConferences/05_Johnson_03-19-13.pdf

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Chemical VI(TCE) at ASU’s ‘Sun Devil Manor’

* Stopping All Monitoring (see Schuver AWMA VI 2014)

**for Chronic avg. values

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Some Evidence from ASU’s “Sun Devil Manor” Radon intrudes in Soil Gas ~~ w/ TCE

Differences in Baselines; but similar Directions of change

https://iavi.rti.org/attachments/WorkshopsAndConferences/02_Holton_Weather-Temporal-Variation-3-22-2012.pdf

ASU’s Cautious Conclusions

While “not … a strong indicator of when VI is occurring at this site ”

“With a lot of data, radon may tell us that VI can occur at this site”

Spoiler Alert! – Preview Can we use Radon as a tracer/surrogate/indicator?

• … of soil gas migration and more specifically:• Indoor-radon levels (relative to outdoor) as a tracer/surrogate/indicator of

building-specific susceptibility to the intrusion of nearby soil-gas

• Not just the absolute Magnitude-# of Rn conc.– as predictor of the magnitude of CVOC conc. in indoor air

• Too many additional CVOC variables (e.g., Schuver & Mosely 2009)

• Yes - Magnitude of Indoor Rn - relative to outdoor

• Yes - Direction of change – Increasing Rn & CVOCs

– “strong statistical relationship … statistically significant at the 1% level and … predict 40 to 60% of the variability … indoor air VOC”*

*Internal EPA-ORD draft report text based on Indy house (Schumacher et al., 2014)

Summary of the Need for CVIOn-going Screening/Monitoring

• All existing intensive-(data-rich)-monitoring evidence from both CVI & Radon studies*

• As well as

– Rn, GW-MNA, LTS, Pub-water, NAS evidence-based policies (Schuver, Battelle 2014)• Most/all Rn & CVOC VI appears to be episodic (Re: ‘stds’)

– Most CVI cases with source conc. w/n 100x of screening levels

• Small % of sites w/ more obvious (high- or low-baselines)

– On-going (across time) & Source-wide (all bldgs.) monitoring (LTS) is as, or more, appropriate• Than for any other (chemical) pathway for exposure

– Traditionally primarily-considering Chronic Exposure durations *see (Schuver AWMA VI 2014)

TCE toxicity in IRIS Sept. 2011* Changing Tox. help SAM?

“Based on a weight-of-evidence evaluation …– Including

• Human epidemiologic studies, [primarily occupational]• Animal dosing studies, and• Experimental mechanistic studies

– The assessment concluded that TCE poses …• Non-cancer toxicity [can be sub-chronic] to the

– Central nervous system,– Kidney,– Liver,– Immune system, – Male reproductive system, and the– Developing fetus, and is

• “Carcinogenic to humans” by all routes of exposure.”*10

*Aug. 27, 2014; OSRTI Memo: Compilation of Information Relating to Early/Interim Actions at Superfund Sites and the TCE IRIS Assessment

Listed last & perhaps w/ least evidence, but notable

• 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 = 1.03-1.48)

– 76 Low birth weight• RR = 1.36 (95% CI = 1.07-1.73)

– 37 Term low birth weight• RR = 1.68 (95% CI = 1.20-2.34)

– 15 Cardiac defects• RR = 2.15 (95% CI = 1.27-3.62)

– 3 Conotruncal** defects• RR = 4.91 (95% CI = 1.58-15.24)* Also a similar paper on increases in adult cancers

** “abnormal formation of the outflow tracts of the heart”(RR) Rate Ratios relative to the rest of NY state (excluding NYC) http://ehp03.niehs.nih.gov/article/fetchArticle.action?articleURI=info%3Adoi%2F10.1289%2Fehp.1103884

“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.”

3 mos. after TCE in IRIS

Week 3: 15-21 days from fertilization - “Primitive heart tube is forming” Week 4: 22-28 days from fertilization - “The heart bulges, further develops, and begins to beat in a regular rhythm.”

Short-Term RisksSome (assoc.) examples*

Some [CVI] Options are Needed(and some Lessons from Radon would help)

• Current-Conventional CVI assessments take limited, but typically extended* amounts of time – Seeking permanent ‘walk-away’ decisions

• Based on ‘high-certainty’ samples for Predictions [for all future cond.]

– Leaving Un-Monitored Natural Attenuation as the only protection for all future conditions [not ok for GW]

1) Predictions are incompatible objective for the Radon (simpler) pathway (Schuver, Battelle 2014)

2) For short-term** effects extended study can be “a public health issue” [ORCR-Immediate-Office comment]

• Is it “Only a matter of time” … ?– i.e., Plausibly assoc. short-term health effects in home(s) under study for

‘potential’ VI• Plausible scenario since most time (under study) is un-sampled?

*Relative to the (short-term) exposure periods of concern**For example some effects (e.g., TCE in IRIS) plausibly assoc. with exposures as short as 1 to 21 days.

Option 1 .‘Ideal’ .

• Media/Location Indoor Air (exposure point) • % of Exposure Pt. (Bldg.) 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%

• Didn’t miss any problems & no errors (0 False-Positives)

• Confidence Negative Screen-Out* 100% / 100%• Didn’t miss any non-exposed & no errors (0 False-Negatives)

• Overall duration of Monitoring As Long As VI Source Remains• Cost High ($$$$$$$$$)

Screening Result

Not Exposed

Exposed

Positive 0 100%

Negative 100% 0

* (c/st) = for Chronic / Short-Term risks

Comparison of Options 1 & 2, & their DownsidesCharacteristic Ideal Downsides

of IdealConventional Downsides

Of Conventional

Media/Location Indoor Air Background Indoor Air Background

% 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 1 day/3 mos. Unlikely to catch episodic peaks

Time b4 results Real time (0 d) Not Practical ~90 days > Exposure duration

Sensitivity*(c/nc) 100%/100% Not feasible <40%**/<<40% Too Ineffective ?

Specificity*(c/nc) 100%/100% Not feasible >95%?/99% High False-Neg. % ?

Total Duration of monitoring

As Long as Source Remain

High Costs 1 year Must predict future & no evidence it can

Cost/bldg. $$$$$$$$$ Too High/bldg.Not Realistic

$$$$$$ Moderate cost by adj. # Bldgs. & Freq.

*Sensitivity (TP/(TP+FN)) & Specificity (TN/(TN+FP)) per bldg. for Chronic / Short-Term risks**Interpretation from Holton et al., 2013 for chronic risk (for long-term avg. exposures)

Objectives for Hybrid – Decreasing the Downsides of Options 1 & 2Characteristic Downsides

of IdealDownsidesof Conventional

Objectives for Hybrid

Media/Location Background Background ‘No’ Background issues

% 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

Sensitivity*(c/nc) Not feasible Too low/Ineffective Higher e.g., >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

*fewer high-certainty (& -cost) CVOCs

How can the Hybrid Option meet such Objectives?

• Make On-Going Screening/Monitoring practical by:– Only screening/monitoring for now (current conditions)

–Not intended for screening-out forever (all future cond.)

• Approach the Ideal option while still being practical by:– Breaking into Two (‘rapid’ & practical/sustainable) Steps:

1) Priority-Screening based on Probability of CVI • Not Certainty*

2) More-confident methods for ‘Probable’ CVI

*(i.e., more realistic, not trying to go directly from “Potential” to “Certainty”)

Hybrid – Step 1 ConclusionsProbability for a ‘complete’ VI Pathway?

• Finding Buildings (with all three conditions):– 1) Overlie VI source, & [VI Potential]

– 2) VI-COCs detected in near-foundation soil gas; [VI Possible]

– 3) Indoor Radon conc. >3-5x outdoor [VI Susceptible]

• Intrusion of near-building soil gas is occurring* &– Probably including the VI-COCs in nearby soil gas

• CVI exposure pathway appears to be ‘probably complete’**• Not confirming ‘complete’ or unacceptable exposures • But Informative (evidence-based) priority-screening

*Note, indoor Rn is a ‘one-way’ indicator of SG/VI - Low indoor Rn is not as meaningful**At some conc. level (not necessarily at unacceptable conc.) 17

Hybrid Option – Step 2The Decision

• Finding Probable (‘low’/episodic) CVI conditions; – Further on-going-screening/monitoring could involve: – High-quality/confidence indoor air samples analyzed for

CVI-chemicals* and collected: • At an on-going-frequency appropriate for the shortest

exposure period of concern, [e.g., possibly 1/every day]– ~ ~Conventional assessment methods, amplified [both +/-]

• or

• Less frequently, when combined with intrusion-reducing Controls (of ~1/100x reduction factor)** & with ‘continuous’ Indoor-Radon (verification) monitoring =

A radon-monitored ‘Soil Gas Safe’ Option* Including addressing ‘Background’ concerns**Controls also allows further stress-testing of CVI source term, for confident ‘exit’ strategy

Comparison of Options 1, 2 & 3Characteristic Ideal Conventional Hybrid Step 1 Hybrid Step 2

Using Radon- SGS

Media/Location Indoor Air Indoor Air Soil Gas nearby Indoor Air

% Bldgs. 100% 15% 100% outside 100%

Para./Analytes Site-CVOCs Site-CVOCs Site-CVOCs Radon (+CVOC)

% time sampled 100% 1% 15% 100%

Sample Duration & Frequency

Continuous 1 day/3 mos. Qtrly- 14 days per 3 mos.

Continuous

Time b4 results Real time 0 day ~90 days ~30 days 7 days

Sensitivity*(c/nc) 100%/100% <40%**/<<40%(1% x 3% peaks)

>95%?/>95%?Research needed

>95%?/>95%?Research needed

Specificity*(c/nc) 100%/100% >95%?/99% >95%?/>95%? >95%?/>95%?

Total Duration of monitoring

ALVISR*** 1 year – typical but adequate?

ALVISR*** or until controls

ALVISR*** w/ SG controls

Cost/building $$$$$$$$$ $$$$$$ $$ $$ (Res.)****

*Sensitivity& Specificity per building for Chronic and Non-Chronic risks (c/nc) **Interpretation from Holton et al., 2013 for chronic risk (long-term avg. exposures) ONLY***As Long as VI Source Remains (ALVISR); ****Incl. typical Res. Mitigation & some CVOCs

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EPA-ORCR requested slide, by Dr. Hers from EPA VI workshop at AEHS 2014

Qualificationsfor this use:-Not incl. Step1 soil-gas-Not incl. LessFreq. IA CVOC samples w/ mitigation;- Assumes same Freq. of non-Mitigation samples over long periods; Decreases likely appropriate (as per CSM)

Unlikely true for short-term events

Only option providing continuous (short-term) protection is Lowest Cost

In Closing: Evidence Indicates:• Long-Term/On-going Monitoring/management – of ‘Low/episodic’ Chemical Vapor Intrusion • Is Appropriate/Needed (ALVISR)*

• Short-term exposure risk scenarios suggest:– Exposure-point monitoring on a frequency:• More frequent than shortest period of concern

• Less frequent chemical monitoring can be appropriate IF:– Soil-gas Intrusion is Prevented – Significantly-Reduced

• w/ ‘continuous’ validation of effectiveness (e.g., Rn tracer)

– Cost/Benefit Ratio << % by being ‘Soil Gas Safe’

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

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