TCE Update

Former NAS Moffett Field Restoration Advisory Board Meeting

January 14, 2010

Dan StralkaRegional Toxicologist

EPA Region 9

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TCE Update

• Significance of TCE at Superfund sites• EPA drinking water standard for TCE is 5 ppb• No similar EPA standard for vapor intrusion pathway and indoor air

• EPA currently reassessing TCE toxicity• Integrated Risk Information System (IRIS) process• Chronology of TCE Toxicological Assessment• What’s New in the Draft 2009 TCE Toxicological Review

• Questions

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Why is IRIS Important? Risk Assessment and Risk-Based Cleanup Levels (PRGs)

1. Hazard Identification(What type(s) of toxicity?)

2. Dose-Response(How much exposure produces toxicity?)

3. Exposure Assessment(How much are people exposed?)

Risk Assessment Risk Management

4. Risk Characterization(How much risk?)

Identify Regulatory Options

Evaluate public health, economic, social & politicalconsequences

Agency Decisions& Actions

IRIS

Integrated Risk Information System - IRIS

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What is Involved in an IRIS Assessment?

• Review scientific literature for toxicity data– identify useful (scientifically valid) studies

• Analyze the relevant data– identify critical studies, toxicities– quantitative modeling of dose-response

• Write a toxicological review• Calculate toxicity values for risk assessment

– cancer potency factors– non-cancer reference doses

• Publish on IRIS database

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Current IRIS Development Process

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Steps of Risk Assessment

• Hazard Identification – what type(s) of toxicity can the contaminant cause?

• Dose-Response Assessment – what amounts of exposure (doses) produce toxicity?

• Exposure Assessment – to how much are people exposed?

• Risk Characterization – how much risk are people experiencing?

The first 2 steps are the main focus of IRIS.

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Hazard Assessment

Health Effects associated with TCE

• Non-cancer– Acute effects-neurological– Various organ systems

• Liver • Kidney

– Immunological– Reproductive– Developmental

• Cancer– Kidney– Liver– Lymphoma

• Mode of Action– Mutagenic – through metabolites

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TCE Toxicity Assessment Chronology

• Purpose: Identify potential health effects of TCE and how much exposure to TCE causes harmful effects

• 1985-87: 1st EPA TCE Health Assessment & Addendum• 1989: withdrawn from IRIS• 2000: “State of the science” papers published• Aug 2001: Draft EPA TCE assessment update - pubic comment

and external peer review• Dec 2002: EPA Science Advisory Board (SAB) independent peer

review report• Feb 2004: EPA hosts Symposium on New Science• Sep 2004: National Research Council (NRC) consultation on

“Key Scientific Issues”• Jul 2006: NRC issues report “Assessing the Human Health

Risks from TCE”

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TCE Timeline (continued)

• 2009: EPA interagency consultation• Oct 2009: EPA Federal Register Notice soliciting EPA SAB

review panel nominations • Nov 2009: EPA releases updated Draft TCE Tox Review

Assessment - external review draft• Jan 2010: IRIS TCE Tox Review Listening session on Jan 26• Feb 1, 2010: 90-day comment period ends• Apr 2010: EPA SAB peer review on specific issues• 2010 -11: EPA SAB review report, revisions, final EPA review,

other federal agencies, and White House discussion• 2011 & beyond?: Final TCE Toxicity Assessment on IRIS

• Where to go for more information:http://www.epa.gov/ncea/ and click on the TCE link

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What’s New in the Draft 2009 TCE Toxicological Review

• Cancer and Non-cancer values• Values for both oral and inhalation • Account for multiple sites of cancer• Mutagenic mode of action for kidney cancer

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Possible TCE Indoor Air Screening Levels DRAFT – For Discussion Only

Indoor Air Screening Level

(micrograms per cubic meter)

2009 EPA Proposed Plan

(MEW/Moffett Field)

EPA Draft 2009 Tox Review(subject to change)

Endpoint Cancer(10-6)

Cancer(10-6) non-cancer

ResidentialScreening Level

(24 hrs/day)1 0.24 - 0.96 5.2

CommercialScreening Level

(10 hrs/day)5 2.5 - 9.8 17.5

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TCE Update: Take Home

• There are still several outstanding scientific and policy questions to resolve on TCE toxicity reassessment.

• Finalization of TCE toxicity reassessment is still over a year or more away.

• EPA has Five-Year Review process and will assess impact of any changes that revised TCE toxicity values have on health-based screening values and risk management decisions at each Superfund Site.

Questions?

Dan StralkaRegional Toxicologist 415.972.3048Stralka.Daniel@epa.gov

Where to go for more information on TCE:www.epa.gov/ncea/ and click on TCE link