Vapor Intrusion:Regulatory Priorities and Toxicological

Complexities

Robert P. DeMott, Ph.D., DABT

ENVIRON International rdemott@environcorp.com

Florida Section – AIHA Conference 24 March 2006

Presentation Outline

Introduction

Rise of Regulatory / Risk Assessment approaches

Toxicological Complexities

Case Study – Inhalation Toxicity

Inhalation Exposures – New Tricks for an Old Dog

Early “environmental” controls focused on vapor inhalation- Industrial hygienists, ACGIH, OSHA

- In workplace – direct, obvious pathway

Ambient air also early focus – Clean Air Act, Ambient Air Quality Standards

For “contaminated sites” – inhalation exposures more complex, indirect

In a Distant Time….

Facing workplace needs, scientists with names like Patty, Zenz, and Hayes invented tools, approaches, and ultimately set safe limits for workers…

Highly Empirical

Tightly Linked to Human Reactions / Responses

Golden Age

Industrial hygiene viewdominates inhalationcontrol / risk evaluations

Progress to the “Part-Per-Million Era”

Workplace safety leaps forward

Toxicologists Serve As Trusted Advisors

Dark Ages --

Love Canal and the rise of “Sites”

Soil and groundwaterbecome focus

Direct contact pathwaysfirst addressed

Inhalation involves transport – more complex, later emerging

New Age

New type of scientists/technocrats bring new approach

“Risk Assessment”

Re-derivation of toxicity values / level of safety

New Age

Modeling andextrapolationused to protectagainst uncertainties

Toxicologists relegated to new role…

“The Future is Now…”

Risk assessors/regulators stopped downplaying inhalation exposures

Limitation was always getting vapor concentration to assign- Soil – “volatilization factor”

- Groundwater – Andelman shower model

Tools and approaches emerged to consider “Vapor Intrusion” and resultant pathways

Soil Vapor Intrusion Pathway

Migration from subsurface into overlying buildings

Increased attention as a potentially significant indoor air exposure

EPA and many states provide target screening levels derived via “Risk Assessment” approach

Conceptual Model

Pressure-driven flow- Building

underpressurization- Stack Effect- Wind loading- Ventilation systems- Barometric pressure

- Diffusion through cracks

Factors Affecting Soil Vapor Intrusion

Source Characteristics- Soil or groundwater

- Concentration and location

- Biodegradability

Soil Characteristics- Air permeability, moisture content, surface cover

Building Construction- Foundation type (basement, slab-on-grade, etc.)

- Foundation openings (crack size)

- HVAC system, air exchange rate

- Depressurization

Florida Factors

Conditions can enhance groundwater vapor transport- Highly transmissive soils (sands)

- Shallow water table

- High temperatures

Several FDEP GCTLs exceed EPA groundwater targets protective of indoor air

Florida-specific targets would be lower than current groundwater targets for numerous chemicals

Technological Tipping Point

Johnson & Ettinger Model (1991):

Steady-state upward diffusion

Intrusion through a perimeter crack

Source can be soil, soil gas, groundwater, or NAPL

Generically conservative but beware of misapplication

Can be customized to site conditions

Science Regulation Recognition

OSWER GuidanceRCRA, CERCLAAnd BrownfieldsJ&E Model

Publication

1991

ASTM RBCAGuidance

1995

2001

Draft RCRA EISupplemental Guidance

2002

MA State Guidance

199320

02

EPA OSWERGuidance

MI StateGuidance

1998

1994

Redfield RifleRegulatory Invest.

EPA OSWERGuidance

Denver Post/Redfield Rifle

2000

Moffett FieldRegulatory Invest.

2004

Mt. View,Tallevast.

15 Years from Concept to Cause

EPA Creates Guidance

Consolidated, Multi-program Guidance (Superfund, Brownfields RCRA)

States conforming

Tiered Approach

- Common in modern risk-based guidance

- Intended to promote efficiency

- Simplified tiers rely on intentional protective bias

2002 OSWER Guidance

- Primary Screening

- Volatile and toxic compounds present?

- Buildings present?

- Immediate response required? (health effects,noxious odor, explosive levels)

2002 OSWER Guidance

- Secondary Screening- generic risk-based screening tables (groundwater, soil gas)

- Site-specific screening values (modify eqn inputs)

- Site-Specific Assessment- Field investigations- Soil gas, indoor air monitoring

State Initiatives

Groundbreakers:Massachusetts – 1992

Groundwater standards based on vapor intrusion

Connecticut – 1996 Michigan – 1998Default numerical criteria

Following Suit:NY, PA, CA, IL, LA, TX, VA, others

Florida - Wait and See

Regulatory Pressures

Regulatory prioritiesoften controlled by inertia

Perceived regulatory gap is a motivator

- Indoor air “discoveries”

- Media attention

New guidance breaks the logjam

Redfield Rifle Site

TCA plume beneath Denver neighborhood

“Site” work and recognition of potentially affected neighbors -- mid-90s

Actually incorporated residential mitigation into site remedy

2002 – Denver Post runs acclaimed series of stories

Media HelpsFocuses Attention

Moffett Field – Silicon Valley

TCE Plume

Dates back to DoD days

Semiconductor manufacturing

Local hydrogeology creates far reaching plume

Public awareness fueled by media buzz

Recalibrating Risk

Risk assessment based approach applies protective bias for uncertainties

Substantially lower than occupational limits

Do NOT account for ambient background !

“Screening” means “Standard”

“Won’t Hurt You” vs. “Safe”

Chemical C / NCEPA Generic

Screening Values (ppb)

OSHA PEL TWA(ppb)

ACGIH TLV TWA

(ppb)

Tetrachloroethene C 12 100,000 25,000

Trichloroethene C 0.41 100,000 50,000

Vinyl Chloride C 11 100,000 5,000

Benzene C 9.8 10,000 500

Carbon Tetrachloride C 2.6 10,000 5,000

Chloroform C 2.2 -- 10,000

1,1,1-Trichloroethane NC 400 350,000 350,000

1,2-Dichloroethene (cis) NC 8.8 200,000 200,000

1,2-Dichloroethene (trans)

NC 18 200,000 200,000

Naphthalene NC 0.57 10,000 10,000

Toxicological Complexities

TCE- Just what exactly is the toxicity of this stuff??

Napthalene- Non-carcinogen yesterday, carcinogen today

1,4-Dichlorobenzene- It’s OK here, but not there?

Trichloroethylene

Cancer potency estimate withdrawn in 1989 – still used

New EPA value -- 2002- ~ 65-times more potent- Much comment/debate ensued

Doesn’t use latest EPA approach for dealing with cancer mechanisms

Last NAS review -- 2005… no resolution expected for years

Science Continues to Emerge

Crit. Rev. Toxicol. 34: 386-445, 2004.

Cancer vs. Non-Cancer

Napthalene

PAH (MGP) plumes

Reference dose- Threshold for response- Apply uncertainty factors (margin of safety)

Cancer slope factor – linear, no-threshold assumption

New screening level 3-300 fold lower (depending on state/region)

Paradox Wrapped Inside a Conundrum…

1,4-dichlorobenzene- Common ambient levels (sanitizer)

- EPA carcinogen …. Or Not…

PPM levels OK in the “lounge”

10-fold (or more) lower CLEANUP Target for environment

“Imagine a plant…”

Risk-Based Wrap Up

Train has left the station

Can’t argue against protection

Complexities left for scientists to work out

•Role for industrial hygienists…

Just remember your trusted advisors … toxicologists

CSI: Tampa….

Vapor Exposure Case Study

Workplace vs. Environmental Vapors

Liver Damage in Haz Waste Workers

Investigation after multiplecomplaints of illness

Survey of self-reportedindications (symptoms)

Clinical testing (ALT, AST) indicated numerous abnormal results

Chronic, ongoing problem or discrete event?

Haz. Waste Facility Events

Liquid wastes being incinerated

Soil being chemically treated and incinerated

Flash fire occurs while processing drums, fire extinguisher system discharges

Employees cleanup fire suppressant foam

Several employees acutely, observably ill over next two weeks

Many employees with complaints

Good Hypothesis – Partial Fit

Tennessee Dept. of Health concluded- Workplace exposure caused effects

- Detection was confounded by background incidence of hepatitis and other challenges to liver function

- Liquid wastes being processed at time of fire not liver toxicants

- “Unknown compound” formed mixing solvents and fire suppressant (baking soda)

Median ALT By Date Drawn

0

200

400

600

800

1000

1200

1400

1600

1800

Pre-empl 10/31 11/30 1/18 1/22 1/30 2/1 2/6 3/7-Pre

Date

Medi

an A

LT

Spike In Liver Enzymes Defines Critical Time Point

Clinical Chemistry Supports Discrete Event (S!)

Patients with ALT > 1000, By Date

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

Pre-empl 10/31 11/30 1/18 1/22 1/30 2/1 2/6 3/7-Pre

Range of Dates

Lev

el o

f A

LT

Patient A

Patient B

Patient C

Patient D

Patient E

Patient F

Patient G

Patient H

Soil Chemistry

Tentatively Identified Compounds

Obscure sulfur mustard-related compounds

Breakdown products from chemical warfare agents

Remediation at nearby arsenal for this type of compound ongoing

Refined Timeline Refines Possibilities

Key uncertainty – employee with obvious signs a week too late – lead to reconsideration

Overlap between:Soil processing (18 Jan, 19 Jan)Tower fire (16 Jan)

But –- Also processed soil (25 Jan, 26 Jan)- Arrival and staging of soil rolloffs (15 Jan)

Second Source Unfolds

Rolloffs were from munitions depot cleanup

Chemical-warfare agent containing soil supposedly segregated, sent elsewhere

Sampling of containers documents low levels of known components/breakdown products

Case Study Lessons

Look for “gators in the weeds”

Force-fitting hypothesisshuts out search for answer

Data that “don’t fit”- Noise or Hint?

Conclusions

New Approaches, New Regulatory Priorities

Challenge to Occupational Exposure Paradigm

Industrial Hygienists – role in bridging workplace and contaminated site regulation

Need for “old skills” never ends…