TCE UpdateTCE Update

Former NAS Moffett FieldFormer NAS Moffett FieldRestoration Advisory Board Restoration Advisory Board

MeetingMeeting

July 17, 2008 July 17, 2008

Stan Smucker - ToxicologistStan Smucker - Toxicologist

U.S. EPA Region 9U.S. EPA Region 9

Tonight’s TopicsTonight’s Topics

• TCE Toxicity and EPA’s Health Risk TCE Toxicity and EPA’s Health Risk AssessmentAssessment

• Update to the Region 9 PRG Screening Update to the Region 9 PRG Screening Table and New Inhalation GuidanceTable and New Inhalation Guidance

• Breakdown Products of TCE in the Breakdown Products of TCE in the EnvironmentEnvironment

What is TCE?What is TCE?

• Trichloroethylene (TCE) is a solvent Trichloroethylene (TCE) is a solvent that has been widely used by that has been widely used by industry as a cleaning and industry as a cleaning and degreasing agent. TCE is a volatile degreasing agent. TCE is a volatile organic chemical (VOC) which means organic chemical (VOC) which means it evaporates readily in air.it evaporates readily in air.

TCE - Current EPA PracticesTCE - Current EPA Practices

• Maximum Contaminant Level (MCL) of Maximum Contaminant Level (MCL) of 5 parts per billion (ppb) TCE is the 5 parts per billion (ppb) TCE is the drinking water standard drinking water standard

• No similar EPA standard for vapor No similar EPA standard for vapor

intrusion pathway and indoor airintrusion pathway and indoor air

• EPA is currently reassessing TCE toxicityEPA is currently reassessing TCE toxicity

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

• Where we are at:Where we are at:- 1- 1stst EPA Toxicity Assessment in the 1980’s EPA Toxicity Assessment in the 1980’s- 1- 1stst EPA draft Assessment Update 2001 EPA draft Assessment Update 2001- 2- 2ndnd EPA draft Assessment Update 2008/2009 EPA draft Assessment Update 2008/2009- Final Update expected sometime in 2010 or - Final Update expected sometime in 2010 or beyondbeyond

• Where to go for more information:Where to go for more information: Go to http://www.epa.gov/ncea/

and click on the "TCE" link under "Risk Assessments“

TCE Toxicity Assessment TCE Toxicity Assessment UpdateUpdate

What Type of Adverse Health Effects What Type of Adverse Health Effects

are Associated with TCE?are Associated with TCE? What Type of Adverse Health Effects What Type of Adverse Health Effects

are Associated with TCE?are Associated with TCE?

• Kidney, liver, lymphomaKidney, liver, lymphomaOther?Other?

• Mechanism of ActionMechanism of Action- initiator?- initiator?- promoter?- promoter?

• Acute effects (CNS depression)Acute effects (CNS depression)• Various other systemic effects Various other systemic effects

(e.g., liver, kidney)(e.g., liver, kidney)• Reproductive, developmental, Reproductive, developmental,

neurological disordersneurological disorders• Immunologic effectsImmunologic effects

Non-Cancer Cancer

Multiple Adverse Endpoints

Uncontrolled Growth of

Cells

NASA Graphic

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TCE Exposure GuidelinesTCE Exposure Guidelines

• Set at protective levels to provide a Set at protective levels to provide a sufficient margin of safety for everyone, sufficient margin of safety for everyone, including “sensitive” individuals (diabetics, including “sensitive” individuals (diabetics, people taking drugs that affect the liver, people taking drugs that affect the liver, infants and pregnant women)infants and pregnant women)

• Because guidelines are developed with a Because guidelines are developed with a margin of safety, the possibility of health margin of safety, the possibility of health effects occurring is low even if slightly effects occurring is low even if slightly above the guidelineabove the guideline

Preliminary Remediation GoalPreliminary Remediation GoalTCE in Indoor Air (Residential)TCE in Indoor Air (Residential)

• Health-Based CriteriaHealth-Based Criteria

-- Protective of Cancer EffectsProtective of Cancer Effects -- Protective of Non-Cancer EffectsProtective of Non-Cancer Effects - Protective of both Short-Term - Protective of both Short-Term

and Long-Term Exposuresand Long-Term Exposures

• Margin of SafetyMargin of Safety

-- Accounts for Sensitive Groups Accounts for Sensitive Groups - - Data Gaps in the ScienceData Gaps in the Science

• Other ConsiderationsOther Considerations

- - Can be Reliably Can be Reliably Measured using Current Measured using Current Laboratory Methods Laboratory Methods (Detection Limit = 0.14 (Detection Limit = 0.14 ug/mug/m33))

- - Typically Above Typically Above

“Background” TCE Levels “Background” TCE Levels Measured in Mountain View Measured in Mountain View AirAir

Interim Guideline = 1 ug/m3 TCE

2008 Update to EPA Region 92008 Update to EPA Region 9Preliminary Remediation Preliminary Remediation

Goals (PRG) TableGoals (PRG) Table

• The Region 9 PRGs have been harmonized The Region 9 PRGs have been harmonized with similar risk-based screening levels used with similar risk-based screening levels used by Regions 3 and 6 into a single tableby Regions 3 and 6 into a single table

• Incorporates the latest Risk Assessment Incorporates the latest Risk Assessment Guidance and Agency Toxicity ValuesGuidance and Agency Toxicity Values

• The updated PRG screening table is available The updated PRG screening table is available at:at:http://epa-prgs.ornl.gov/chemicals/index.shtmlhttp://epa-prgs.ornl.gov/chemicals/index.shtml

What’s New in the 2008 PRG What’s New in the 2008 PRG TableTable

• Per EPA’s updated Cancer Guidelines an Per EPA’s updated Cancer Guidelines an additional safety factor for children (0 – 16 additional safety factor for children (0 – 16 years) is included for cancer-causing years) is included for cancer-causing substances that are determined to damage DNA substances that are determined to damage DNA through a mutagenic mechanism of action through a mutagenic mechanism of action

• Incorporates new inhalation exposure equations Incorporates new inhalation exposure equations from Risk Assessment Guidance for Superfund from Risk Assessment Guidance for Superfund (RAGS Part F) in anticipation of the release of (RAGS Part F) in anticipation of the release of this new EPA guidance later this year this new EPA guidance later this year

• A new column has been added to the PRG Table A new column has been added to the PRG Table that presents indoor air screening values for that presents indoor air screening values for workers in addition to residents workers in addition to residents

Impact of new EPA Inhalation Impact of new EPA Inhalation Guidance on Decision-making at Guidance on Decision-making at MEW and MoffettMEW and Moffett

• Residential TCE numbers for the MEW site do not Residential TCE numbers for the MEW site do not change since indoor air criteria using both the change since indoor air criteria using both the “old” and “new” equations round to 1 ug/m“old” and “new” equations round to 1 ug/m33 TCE TCE that EPA Region 9 is currently usingthat EPA Region 9 is currently using

• The updated PRG screening table presents a The updated PRG screening table presents a generic PRG of 6.1 ug/mgeneric PRG of 6.1 ug/m33 TCE for workers based TCE for workers based on an 8 hour exposure timeon an 8 hour exposure time

• The draft RI report for vapor intrusion for The draft RI report for vapor intrusion for MEW/Moffett describes a worker exposure time MEW/Moffett describes a worker exposure time of 9.5 hours per day. This site-specific exposure of 9.5 hours per day. This site-specific exposure time results in a PRG of about 5 ug/mtime results in a PRG of about 5 ug/m33 TCE (up TCE (up from 2.7 ug/mfrom 2.7 ug/m33 TCE that Region 9 calculated TCE that Region 9 calculated using the “old” exposure equation)using the “old” exposure equation)

“Old” Equation (RAGS 1989)

Target Risk x Body Weight x Averaging Time x 1000 ug/mg Inhalation SF x Inhalation Rate x Exposure Frequency x Exposure

Duration

= 2.7 micrograms per cubic meter TCE

New vs. Old PRG Equation for Indoor Workers

“New” Equation (RAGS 2008)

Target Risk x Averaging Time Inhalation UR x Exposure Time x Exposure Frequency x Exposure

Duration

= 5.2 micrograms per cubic meter TCE

Questions / Comments?Questions / Comments?

TCE Breakdown Products in TCE Breakdown Products in Subsurface (Anaerobic Subsurface (Anaerobic

Conditions)Conditions)TCE

cis-1,2-DCE trans-1,2-DCE

Vinyl Chloride

Ethene

TCE is transformed in the atmosphere by the action of sunlight and the main degradation products are represented by dichloroacetyl chloride, formyl chloride and phosgene. Other, but less important reactions, are direct photolysis and reaction with ozone.

ATSDR Tox Profile for TCE 1997

TCE Breakdown Products in Air

More Questions / More Questions / Comments?Comments?