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Vapor Intrusion: Regulatory Priorities and Toxicological Complexities

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

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Vapor Intrusion: Regulatory Priorities and Toxicological Complexities

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  1. Vapor Intrusion:Regulatory Priorities and Toxicological Complexities Robert P. DeMott, Ph.D., DABT ENVIRON Internationalrdemott@environcorp.com Florida Section – AIHA Conference 24 March 2006

  2. Presentation Outline • Introduction • Rise of Regulatory / Risk Assessment approaches • Toxicological Complexities • Case Study – Inhalation Toxicity

  3. 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

  4. 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

  5. Golden Age • Industrial hygiene viewdominates inhalationcontrol / risk evaluations • Progress to the “Part-Per-Million Era” • Workplace safety leaps forward Toxicologists Serve As Trusted Advisors

  6. Dark Ages -- • Love Canal and the rise of “Sites” • Soil and groundwaterbecome focus • Direct contact pathwaysfirst addressed • Inhalation involves transport – more complex, later emerging

  7. New Age • New type of scientists/technocrats bring new approach • “Risk Assessment” • Re-derivation of toxicity values / level of safety

  8. New Age • Modeling andextrapolationused to protectagainst uncertainties Toxicologists relegated to new role…

  9. “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

  10. 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

  11. Conceptual Model Pressure-driven flow • Building underpressurization • Stack Effect • Wind loading • Ventilation systems • Barometric pressure • Diffusion through cracks

  12. 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

  13. 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

  14. 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

  15. MA State Guidance ASTM RBCA Guidance MI State Guidance J&E Model Publication EPA OSWER Guidance EPA OSWER Guidance Draft RCRA EI Supplemental Guidance 1991 1993 1995 1998 2002 2002 2000 1994 2004 Denver Post/Redfield Rifle Moffett FieldRegulatory Invest. Redfield RifleRegulatory Invest. 2001 Mt. View,Tallevast. Science Regulation Recognition 15 Years from Concept to Cause OSWER Guidance RCRA, CERCLA And Brownfields

  16. EPA Creates Guidance • Consolidated, Multi-program Guidance (Superfund, Brownfields RCRA) • States conforming

  17. Tiered Approach • Common in modern risk-based guidance • Intended to promote efficiency • Simplified tiers rely on intentional protective bias

  18. 2002 OSWER Guidance • Primary Screening • Volatile and toxic compounds present? • Buildings present? • Immediate response required? (health effects,noxious odor, explosive levels)

  19. 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

  20. State Initiatives Groundbreakers: Massachusetts – 1992 Groundwater standards based on vapor intrusion Connecticut – 1996 Michigan – 1998 Default numerical criteria Following Suit: NY, PA, CA, IL, LA, TX, VA, others Florida - Wait and See

  21. Regulatory Pressures • Regulatory prioritiesoften controlled by inertia • Perceived regulatory gap is a motivator • Indoor air “discoveries” • Media attention • New guidance breaks the logjam

  22. 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

  23. 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

  24. 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”

  25. “Won’t Hurt You” vs. “Safe”

  26. 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?

  27. 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

  28. Science Continues to Emerge Crit. Rev. Toxicol. 34: 386-445, 2004.

  29. 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)

  30. 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…”

  31. 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

  32. CSI: Tampa…. • Vapor Exposure Case Study • Workplace vs. Environmental Vapors

  33. 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?

  34. 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

  35. 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)

  36. Spike In Liver Enzymes Defines Critical Time Point

  37. Clinical Chemistry Supports Discrete Event (S!)

  38. 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

  39. 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)

  40. 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

  41. Case Study Lessons • Look for “gators in the weeds” • Force-fitting hypothesisshuts out search for answer • Data that “don’t fit” • Noise or Hint?

  42. 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…

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