U.S. ENVIRONMENTAL PROTECTION AGENCY 

OFFICE OF INSPECTOR GENERAL 

Catalyst for Improving the Environment 

 Evaluation Report 

Lack of Final Guidance on 

Vapor Intrusion Impedes Efforts 

to Address Indoor Air Risks 

 Report No. 10-P-0042 

 December 14, 2009 
 

Report Contributors: Carolyn Copper 

 Tina Lovingood 

 Dave Goodman 

 Jee Kim

 Barry Parker

 Angela Bennett 

 Heather Drayton 

Abbreviations 

EPA U.S. Environmental Protection Agency 

IRIS Integrated Risk Information System 

ITRC Interstate Technology Regulatory Council 

OIG Office of Inspector General 

ORD Office of Research and Development 

OSWER Office of Solid Waste and Emergency Response 

PCE Perchloroethylene 

RCRA Resource Conservation and Recovery Act 

TCE Trichloroethylene 

UST Underground Storage Tanks 
 

 

U.S. Environmental Protection Agency 10-P-0042 

December 14, 2009 Office of Inspector General 

At a Glance 

Catalyst for Improving the Environment 

Why We Did This Review	 Lack of Final Guidance on Vapor Intrusion 

We conducted this review to Impedes Efforts to Address Indoor Air Risks

determine what actions the U.S. 

Environmental Protection Agency 

(EPA) has taken, both general 

and site-specific, to identify and 

mitigate human health risks from 

chemical vapor intrusion that can 

be associated with contaminated 

sites. When EPA had not taken 

site-specific actions, we 

examined the reasons why. 

Background 

Vapor intrusion is the migration 

of volatile chemicals from the 

subsurface into overlying 

buildings. EPA has 

acknowledged that current and 

former contaminated sites could 

have extensive vapor intrusion 

issues and pose a significant risk 

to the public. In 2002, based on 

its current understanding of 

subsurface vapor intrusion, EPA 

issued draft guidance. The 

guidance included technical and 

policy recommendations for 

determining whether vapor 

intrusion posed a risk at sites. 

The 2002 guidance remains in 

draft form and has not been 

finalized since it was issued. 

For further information, 

contact our Office of 

Congressional, Public Affairs and 

Management at (202) 566-2391. 

To view the full report, 

click on the following link: 

www.epa.gov/oig/reports/2010/ 

20091214-10-P-0042.pdf 

What We Found 

EPA’s efforts to protect human health at sites where vapor intrusion risks may 

occur have been impeded by the lack of final Agency guidance on vapor intrusion 

risks. EPA’s 2002 draft vapor intrusion guidance has limited purpose and scope, 

and the science and technology associated with evaluating and addressing risk from 

vapor intrusion is evolving. EPA’s draft also contains outdated toxicity values for 

assessing risk to humans from chemical vapors in indoor air. 

EPA’s draft guidance does not address mitigating vapor intrusion risks or 

monitoring the effectiveness of mitigation efforts. The draft guidance also does not 

clearly recommend that multiple lines of evidence be used in evaluating and 

making decisions about risks from vapor intrusion. The draft guidance is not 

recommended for assessing vapor intrusion risks associated with petroleum 

releases at Underground Storage Tank sites. EPA’s outdated toxicity values allow 

for the use of widely different, nonfederal toxicity values and have caused delays in 

work to address possible risks. 

EPA has not finalized its guidance, according to EPA managers and staff, because 

the 2007 Interstate Technology Regulatory Council guidance addressed many 

issues that EPA would have addressed in a final guidance, and because finalizing 

EPA’s guidance would take a long time in light of the emerging scientific issues in 

the field. Also, previous administrative review requirements for Agency guidance 

were perceived as barriers to issuing timely guidance in a rapidly changing 

environment. These requirements were revoked by the current Administration, but 

significant guidance remains subject to some administrative review. 

Seven years later, EPA is developing a roadmap of technical documents that will 

update its draft guidance. However, technical documents may not be effective for 

conveying and representing Agency policy. EPA has also made some progress in 

updating toxicity values for some contaminants most frequently associated with 

vapor intrusion. 

What We Recommend 

We recommend that EPA issue final guidance to establish current Agency policy 

on the evaluation and mitigation of vapor intrusion risks. The Agency should also 

finalize toxicity values for trichloroethylene and perchloroethylene – common 

contaminants associated with vapor intrusion. The Agency agreed with our 

recommendations and provided milestones. 
 

 

 

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON, D.C. 20460 

OFFICE OF 

INSPECTOR GENERAL 

December 14, 2009 

MEMORANDUM 

SUBJECT: Lack of Final Guidance on Vapor Intrusion Impedes Efforts 

to Address Indoor Air Risks 

 Report No. 10-P-0042 

FROM: Wade T. Najjum

 Assistant Inspector General 

 Office of Program Evaluation 

TO: Mathy Stanislaus 

 Assistant Administrator 

Office of Solid Waste and Emergency Response 

 Lek Kadeli 

 Acting Assistant Administrator 

 Office of Research and Development 

This is our report on the subject evaluation conducted by the Office of Inspector General (OIG) 

of the U.S. Environmental Protection Agency (EPA). This report contains findings that describe 

the problems the OIG has identified and corrective actions the OIG recommends. This report 

represents the opinion of the OIG and does not necessarily represent the final EPA position. 

Final determinations on matters in this report will be made by EPA managers in accordance with 

established resolution procedures. 

The estimated cost of this report – calculated by multiplying the project’s staff days by the 

applicable daily full cost billing rates in effect at the time – is $454,233. 

Action Required 

Based on the Agency’s planned actions and milestones provided, the OIG will close the 

recommendations in the OIG tracking system. No further action is required, except that, within 

90 days of this report date, the OIG requires that the Assistant Administrator, Office of Solid 

Waste and Emergency Response, provide interim corrective actions and milestones for its 

planned actions related to Recommendation 2 because the planned completion date for 
Recommendation 2 is nearly 3 years from this final report date. We have no objections to the 

further release of this report to the public. This report will be available at www.epa.gov/oig. 

If you or your staff have any questions regarding this report, please contact Carolyn Copper at 

(202) 566-0829 or copper.carolyn@epa.gov, or Tina Lovingood at (202) 566-2906 or 

lovingood.tina@epa.gov. 
 

 

Lack of Final Guidance on Vapor Intrusion 10-P-0042 

Impedes Efforts to Address Indoor Air Risks 

Table of Contents 

Purpose ................................................................................................................................ 1 

Background .......................................................................................................................... 1 

Noteworthy Achievements.................................................................................................. 2 

Scope and Methodology ..................................................................................................... 3 

Results of Review: EPA Lacks Final Guidance on Vapor Intrusion............................... 4 

Purpose and Scope of EPA’s Draft Vapor Intrusion Guidance Is Limited............... 4 

Lack of Current EPA Toxicity Values Allows for Use of Disparate 

Nonfederal Toxicity Values and Delays Work to Address Possible Risks............... 6 

Scientific and Administrative Issues Are Perceived as Barriers to Issuing 

Final Vapor Intrusion Guidance............................................................................... 8 

Conclusions ......................................................................................................................... 8 

Recommendations............................................................................................................... 9 

Agency Comments and OIG Evaluation ............................................................................ 9 

Status of Recommendations and Potential Monetary Benefits....................................... 10 

Appendices 

A EPA and Other Regulatory Guidance on Vapor Intrusion................................. 11 

B OSWER Response to OIG Draft Report............................................................... 12 

C ORD Response to OIG Draft Report .................................................................... 14 

D Distribution ............................................................................................................ 17 
 

 

10-P-0042 

Purpose 

The purpose of our review was to determine what actions the U.S. Environmental Protection 

Agency (EPA) has taken to identify and mitigate human health risks from chemical vapor 

intrusion that can be associated with contaminated sites. We addressed the following questions: 

1. What steps has EPA taken to identify the potential risks of vapor intrusion from 

contaminated sites? 

2. What actions has EPA taken to ensure that vapor intrusion is being sitespecifically identified and addressed within in its various programs, including 

Resource Conservation and Recovery Act (RCRA), Superfund, Brownfields, and 

Underground Storage Tanks (UST)? Where EPA has not taken actions to sitespecifically identify and address vapor intrusion, why not? 

This assignment is included in the Office of Inspector General (OIG) Fiscal Year 2009 annual 

plan. 

Background 

Vapor intrusion is the migration of volatile chemicals from the subsurface into overlying 

buildings. Volatile chemicals in buried wastes and/or contaminated groundwater can emit 

vapors that may migrate through subsurface soils and into indoor air spaces of overlying 

buildings in ways similar to those of radon gas seeping into homes, as shown in Figure 1. 

According to EPA, in extreme cases, the vapors may accumulate in dwellings or occupied 

buildings to levels that may pose near-term safety hazards (e.g., explosion), acute health effects, 

or aesthetic problems (e.g., odors). 

Figure 1: Vapor Intrusion Migration Graphic 

Note: NAPL is non-aqueous phase liquid.
 

Source: OSWER 2002 Draft Guidance for Evaluating the Vapor Intrusion to Indoor Air 

Pathway from Groundwater and Soils (Subsurface Vapor Intrusion Guidance).
 

1 
 

 

 

 

 

 

10-P-0042 

According to an EPA scientist, the four chlorinated chemicals that pose the highest risks from 

vapor intrusion are the ones that are most frequently found at contaminated sites. These 

chemicals are perchloroethylene (PCE), trichloroethylene (TCE), dichloroethylene, and vinyl 

chloride. 

EPA’s Integrated Risk Information System (IRIS) is an electronic database containing 

information on human health effects that may result from exposure to various chemicals in the 

environment. IRIS contains toxicity values for cancer and/or noncancer effects from oral and/or 

inhalation exposures for more than 540 chemicals, including dichloroethylene and vinyl chloride. 

In November 2002, EPA issued draft guidance titled OSWER Draft Guidance for Evaluating the 

Vapor Intrusion to Indoor Air Pathway from Groundwater and Soils (Subsurface Vapor 

Intrusion Guidance). This guidance provides a tool for evaluating vapor intrusion at RCRA 

sites, some Superfund sites,1

 and Brownfields sites. Since issuing the draft guidance, EPA has 

neither updated nor finalized it. Separately, States, other federal agencies, and stakeholder 

groups have issued vapor intrusion guidance or technical documents. According to the Interstate 

Technology Regulatory Council (ITRC), as of 2008, 26 States have issued their own vapor 

intrusion guidance.2 

Noteworthy Achievements 

EPA has issued a number of guidance and technical documents to help regions and States 

address vapor intrusion. In 1999, EPA’s Office of Solid Waste developed human health 

environmental indicators for the RCRA program that required regulators to consider vapor 

intrusion and issued draft vapor intrusion guidance for use in environmental indicators in 2001. 

EPA’s Office of Solid Waste and Emergency Response (OSWER) issued draft vapor intrusion 

guidance in 2002. To help address the Agency’s concern that the science and technology 

associated with evaluating and addressing risk from vapor intrusion is complex and evolving, it 

issued a fact sheet and other documents. Specifically, in 2004, OSWER developed a 

Brownfields fact sheet, “Design Solutions for Vapor Intrusion and Indoor Air Quality.” OSWER 

also partly funded the 2007 ITRC vapor intrusion guidance, and in 2008, OSWER issued a 

Brownfields Vapor Intrusion Primer. In 2008, EPA also developed the Superfund 

Environmental Indicator Guidance Human Health Revision, which includes consideration of 

vapor intrusion into indoor air. EPA is in the process of creating a roadmap of technical 

documents that update the draft guidance and the ITRC guidance. EPA’s Office of Research and 

Development (ORD) has issued a number of research papers on sampling and modeling for 

1

 According to the 2002 draft guidance, the guidance applies to the Comprehensive Environmental Response, 

Compensation, and Liability Act (National Priorities List and Superfund Alternative Sites). The guidance does not 

mention non-National Priorities List sites such as removal-action-only sites. 2

 Subsequent to our field work, we learned that on September 18, 2009, the U.S. Department of Housing and Urban 

Development updated its 2002 Multi-Family Accelerated Processing Guide, Environmental Review (Chapter 9). 

The update requires a vapor intrusion screen to determine whether there is a potential for vapors to occur in the 

subsurface below existing and/or proposed on-site structures from those hazardous substances, petroleum, and 

petroleum products that consist of volatile organic compounds and semivolatile organic compounds and inorganic 

volatile compounds. 

2 
 

 

10-P-0042 

specific contaminants in soil and groundwater. EPA has engaged in vapor intrusion educational 

activities such as training events and symposiums. 

The Agency has begun the process of drafting policy on vapor intrusion in nonresidential 

settings. It has also progressed in developing IRIS toxicity values for PCE and TCE. EPA has 

also evaluated the presence of vapor intrusion in some Superfund Five-Year Reviews (or 

“protectiveness reviews”). It is planning to issue its Five-Year Review guidance to specifically 

address evaluation of vapor intrusion. 

EPA Region 3 has made the review of indoor air pollutants, including vapor intrusion, a regional 

priority. As part of the Region’s work in this area, it began evaluating Superfund National 

Priority List sites and RCRA sites for vapor intrusion. Where appropriate, it is mitigating the 

risk and also educating the public about the risks from vapor intrusion. 

Scope and Methodology 

We conducted our review in accordance with generally accepted government auditing standards. 

Those standards require that we plan and perform the evaluation to obtain sufficient, appropriate 

evidence to provide a reasonable basis for our findings and conclusions based on our evaluation 

objectives. We believe that the evidence obtained provides a reasonable basis for our findings 

and conclusions based on our evaluation objectives. We performed our review from December 

2008 through September 2009. 

To gain an understanding of vapor intrusion, we attended two vapor intrusion conferences in 

Philadelphia and San Diego and reviewed various online training materials. In addition, we 

researched prior reports by EPA, Government Accountability Office, and ITRC. We identified 

and interviewed EPA vapor intrusion contacts or managers. 

To identify potential internal control weaknesses, we reviewed EPA’s Risk/Vulnerability 

Assessments and Fiscal Year 2008 Agency Assurance Letters. We also reviewed EPA’s Key 

Management Challenges for Fiscal Year 2008, and related Federal Managers Financial Integrity 

Act documents. 

We conducted our work in OSWER, ORD, and EPA Regions 1-10. 

To address our first question, we reviewed documents and information and interviewed EPA 

staff. To address our second question, we analyzed EPA, ITRC, selected State guidance 

documents, and EPA technical/policy documents. (See Appendix A for a sample of these 

documents.) We reviewed existing controls that would trigger review of vapor intrusion at 

contaminated sites, such as environmental indicators, ready-for-reuse indicators, and 

protectiveness reviews. We also reviewed the hazard ranking system for specific mention of 

evaluating vapor intrusion, but found none. 

We visited Region 3 and met with representatives and managers from various programs that 

address vapor intrusion. We discussed the Region 3 draft framework, vapor intrusion priorities, 

and how the programs are managing vapor intrusion. 

3 
 

 

 

 

10-P-0042 

To assess how the remaining regions address vapor intrusion, we sent an online survey to EPA’s 

Vapor Intrusion Forum on February 26, 2009, and analyzed the results. We also reviewed 

supplementary data that were provided as part of the survey. 

Results of Review: EPA Lacks Final Guidance on Vapor Intrusion 

EPA does not have final guidance to establish current Agency policy on the evaluation and 

mitigation of vapor intrusion risks. EPA has taken some steps to identify potential vapor 

intrusion risks, developed plans to address risks, and taken actions to mitigate site-specific risks. 

However, due to perceived administrative and scientific barriers, EPA has not finalized its draft 

2002 vapor intrusion guidance. The draft guidance is limited in scope and purpose. It also lacks 

current toxicity values, or values that estimate the risk of exposure and where action may need to 

be taken. The lack of final EPA guidance has impeded Agency efforts to protect human health 

and the environment at sites where vapor intrusion risks may occur. 

In the absence of final and current guidance (including up-to-date toxicity values), EPA, States, 

and other parties may continue to use widely different toxicity values for determining human 

health risks from vapor intrusion. Some enforcement staff believe draft vapor intrusion toxicity 

values and requirements may limit the Agency’s ability to enforce compliance with those 

standards and may encourage compliance with toxicity values that may not be universally 

viewed as safe. Incomplete evaluations or actions to address vapor intrusion risks may also 

continue, and vapor intrusion risk assessments at petroleum-contaminated sites may not be 

conducted. According to some EPA enforcement staff, the uncertainties created by draft EPA 

vapor intrusion guidance could also limit some EPA efforts to enforce responsible party clean-up 

actions. 

Purpose and Scope of EPA’s Draft Vapor Intrusion Guidance Is Limited 

EPA’s draft guidance focuses on the important issue of assessing whether unacceptable risks to 

human health may occur from chemical vapor exposures. However, the guidance does not 

address actions to mitigate chemical vapor risks. More recently, some States’ and ITRC 

guidance, as well as EPA’s Brownfields Primer and the U.S. Air Force, U.S. Navy, and U.S. 

Army Tri-Services Guidance, include vapor intrusion risk mitigation procedures or information. 

EPA’s draft guidance also does not strongly recommend the use of multiple lines of evidence in 

evaluating and making decisions about vapor intrusion. Use of multiple lines of evidence is 

considered the current state of the science. EPA does not recommend its draft guidance be used 

to assess vapor intrusion risks associated with petroleum releases at UST sites. According to 

EPA, applying the draft guidance to petroleum compounds may overestimate the impact of vapor 

intrusion. EPA’s draft guidance refers the public to UST guidance from 1995,3

 but the 1995 

guidance does not discuss vapor intrusion. More recent guidances address a broader scope of 

relevant vapor issues. 

3

 U.S. Environmental Protection Agency, Use of Risk-Based Decision Making in UST Corrective Action Programs, 

1995. 

4 
 

 

 

10-P-0042 

The recent EPA technical paper addresses some aspects of mitigation, but it is not 

guidance. In October 2008, EPA issued a technical document titled Indoor Air Vapor Intrusion 

Mitigation Approaches. It focuses on “interim remedial measures” to address vapor intrusion. 

Some of the strengths of this document are that it provides an overview of vapor intrusion 

mitigation methods, estimated mitigation costs, discussion of long-term monitoring to assess 

mitigation performance, and development of operations and maintenance plans. However, the 

document provides few details on when to terminate vapor intrusion mitigation systems. It also 

does not include operations and maintenance plan requirements, and it does not convey Agency 

policy or guidance. The document refers readers to New York and New Jersey vapor intrusion 

guidance for further information on operations and maintenance and termination of the systems. 

The draft guidance does not clearly address the multiple lines of evidence approach. EPA’s 

2002 guidance begins to discuss, but does not clearly and strongly recommend, that multiple 

lines of evidence4

 are needed in evaluating and making decisions about vapor intrusion. In two 

places, the draft guidance refers to using more than one line of evidence, and where it does, the 

guidance discusses using evidence in a sequential order to screen out sites. The 2002 draft 

guidance also does not explain the many variables that can affect the evaluation of vapor 

intrusion as a pathway of concern. 

According to the 2008 Tri-Services Guidance for assessing vapor intrusion, using multiple lines 

of evidence in evaluating vapor intrusion has become the “state of the science.” If only one line 

of evidence is used, it could lead to incorrect conclusions about vapor intrusion risks. ITRC 

states that it is important to use multiple lines of evidence to reach decisions based on 

professional judgment. In a January 2009 memo for an interim TCE toxicity value, EPA 

strongly suggested the importance of using multiple lines of evidence and explained the many 

variables affecting the evaluation of vapor intrusion as a pathway of concern. However, due to 

other issues regarding the content of the memo, EPA withdrew the memo in April 2009. 

The draft guidance does not address vapor intrusion at petroleum sites. EPA does not 

recommend use of the 2002 draft vapor intrusion guidance for assessing vapor intrusion risks 

from petroleum releases at UST sites. EPA states in its guidance that this is due to “certain 

conservative assumptions” (i.e., no biodegradation), and the draft guidance is unlikely to provide 

an appropriate mechanism for screening the vapor pathway at UST sites that involve petroleum 

releases. However, other EPA documents state that semivolatile chemicals, such as gasoline and 

petroleum, can pose a vapor intrusion problem. In addition, the draft vapor intrusion guidance 

does include toxicity values for petroleum chemicals that may be a component at non-UST sites. 

Nonetheless, EPA does not recommend the use of the draft guidance at UST sites. 

The 2002 draft vapor intrusion guidance refers readers to the Agency’s 1995 guidance, Use of 

Risk-Based Decision Making in UST Corrective Action Programs. However, this guidance does 

not address vapor intrusion, and the UST program does not have specific vapor intrusion 

guidance. According to a UST program manager, this is because mitigating vapor intrusion at 

petroleum sites is an evolving area that lacks consensus. 

4

 Some examples of multiple lines of evidence ITRC suggests using include soil gas data, groundwater spatial data, 

indoor and outdoor air data, background sources, and building construction and current conditions. 

5 
 

 

 

 

10-P-0042 

EPA’s UST program delegates vapor intrusion assessments to States. However, States do not 

report information to EPA about whether vapor intrusion has been evaluated, is a risk, or needs 

to be mitigated at UST sites. Therefore, EPA lacks the information. In January 2009, the 

Association of State and Territorial Solid Waste Management Officials requested assistance from 

the EPA Office of Underground Storage Tanks to develop vapor intrusion guidance for 

petroleum. 

ITRC’s vapor intrusion guidance acknowledges risk from petroleum vapors. It provides an 

example of a site where petroleum vapors have caused human health concerns. For example, 

“ . . . at a petroleum hydrocarbon site in Colorado, vapor intrusion caused the evacuation of two 

schools. Indoor air samples were collected in another school located outside of the influence of 

the contaminated plume. Following mitigation activities, the students were allowed to return to 

the formerly impacted school when contaminant concentrations in indoor air were in the range of 

concentrations detected in the unaffected school.” 

Although EPA does not recommend its broad 2002 vapor intrusion guidance for UST sites, 

EPA’s 2008 Brownfields Primer does address petroleum. 

Other guidances address a broader scope of relevant vapor intrusion issues. The purpose of 

EPA’s 2002 draft guidance is to help the user conduct a screening evaluation to determine 

whether subsurface chemicals are entering indoor air and, if so, whether they pose an 

unacceptable risk to human health. More recent guidance documents5

 are broader and go beyond 

evaluation of the risk posed by vapor intrusion. Some of these documents provide information 

regarding when or whether preemptive mitigation may be appropriate. Some discuss the 

selection, design, installation, and/or sustainability over the long term of a vapor intrusion 

mitigation system. Some documents also discuss long-term monitoring, when institutional 

controls and deed restrictions are appropriate, and/or when to terminate the mitigation systems. 

EPA also issued guidance in April 2009 on transferring fund-lead vapor intrusion systems to 

States.6 However, this guidance does not detail an operations and maintenance plan or the types 

of operation and maintenance activities that may be required. The April 2009 directive is also 

not included in a comprehensive vapor intrusion guidance. 

Lack of Current EPA Toxicity Values Allows for Use of Disparate Nonfederal 

Toxicity Values and Delays Work to Address Possible Risks 

EPA survey respondents said that EPA’s guidance was outdated because it did not include 

current toxicity values for some chemicals of concern in vapor intrusion assessments. As a 

result, EPA, States, and other parties use alternative toxicity values that vary widely in their 

definition of levels that are considered safe. Lack of some toxicity values has also delayed work 

at Superfund sites with potential risks from vapor intrusion. 

5

EPA’s Brownfields Primer (2008), ITRC guidance (2007), Tri-Services Handbook (2008), and guidance from the 

States of California (2005 and draft 2008), New Jersey (2005), and New York (2006). See Appendix A for 

complete bibliographical information on these documents. 

6

 U.S. Environmental Protection Agency, Operational and Functional Determination and the Transfer of Fund-lead 

Vapor Intrusion Mitigation Systems to the State, April 9, 2009. 

6 
 

 

 

 

 

 

10-P-0042 

Our survey results show that one reason explaining outdated toxicity values is that the values 

were based on oral exposure. These toxicity values assume a default inhalation rate and body 

weight.7

 However, according to the Agency’s January 2009 risk assessment guidance,8 “risk 

assessors are discouraged” from basing toxicity values on oral data, especially when default 

assumptions about inhalation rate and body weight are used. 

The toxicity value for TCE is one of the key values that is outdated. In early 2009, EPA issued 

interim toxicity values to address risks due to TCE exposure. Specifically, EPA recommended 

the use of California’s inhalation risk value for evaluating the cancer effects of TCE in sitespecific risk assessments. For noncancer effects of TCE, EPA recommended two values that 

could be considered in evaluating systemic toxicity at sites. One value was developed by the 

New York State Department of Health, and the other was developed by California’s EPA. 

However, in April 2009, EPA withdrew the interim toxicity values. It believed that the two 

different values for assessing noncancer risks may have led to inconsistency in the development 

of preliminary remediation goals for TCE and site-specific risk assessments. In November 2009, 

EPA released its draft toxicological review for TCE for public review and comment. 

In the absence of current and final EPA toxicity values, regulators and others may use “other 

values” such as nonfederal or State toxicity values.9 These toxicity values can sometimes vary 

widely. One example is PCE in groundwater. The standard in micrograms per liter for New 

Jersey is 1; for Michigan, 25,000; and for Pennsylvania, 42,000. For PCE in indoor air, the 

toxicity value in micrograms per cubic meter for California is 0.41; for New Jersey, 3; for 

Pennsylvania, 36; and for Michigan, 42.10 Differing State toxicity values, and EPA’s lack of 

some toxicity values and final guidance, have raised concerns for a regional enforcement 

manager and staff. They believe that national consistency in screening standards is necessary. 

However, they also stated that they have not experienced any problems yet based on existing 

differing toxicity values. Enforcement staff have concerns about obtaining private party 

commitments to clean up sites to levels that are specified in a draft EPA guidance. 

EPA reports that document the protectiveness of Superfund site remedies (Five-Year Reviews) 

show that the regions were waiting for final guidance or toxicity values before an evaluation or a 

complete evaluation of vapor intrusion would be done. For example, 

7

 U.S. Environmental Protection Agency, OSWER Draft Guidance for Evaluating the Vapor Intrusion to Indoor Air 

Pathway from Groundwater and Soils (Subsurface Vapor Intrusion Guidance), November 2002, Tables 2 and 3, 

third column, where the draft guidance indicates the toxicity values were extrapolated from oral sources. 8

 U.S. Environmental Protection Agency, Risk Assessment Guidance for Superfund Volume I: Human Health 

Evaluation Manual (Part F, “Supplemental Guidance for Inhalation Risk Assessment”), EPA-540-R-070-002, 

OSWER 9285.7-82, January 2009.

9

 In the absence of IRIS or ORD-developed toxicity values, EPA’s guidance directs the evaluator to use “other 

toxicity values.” U.S. Environmental Protection Agency, Human Health Toxicity Values in Superfund Risk 

Assessments, OSWER Directive 9285.7-53, December 5, 2003. The Directive contains a hierarchy for human health 

toxicity values. The first tier is EPA’s IRIS, the second is EPA’s Provisional Peer Reviewed Toxicity Values 

developed by ORD, and the third is other toxicity values. Priority is recommended for sources of information that 

are the most current, the basis of which is transparent and publicly available, and which have been peer reviewed. 10 Eklund, B. et al., “An Overview of State Approaches to Vapor Intrusion,” EM, February 2007. 

7 
 

 

 

 

10-P-0042 

•	 The 2005 protectiveness review for a Region 3 site stated, “Due to the proximity of 

residential homes to the contaminated ground water plume, the potential for vapor 

intrusion into basements will need to be addressed in the future, once . . . EPA 

policy/guidance regarding investigation of vapor intrusion is established.” 

•	 The 2006 protectiveness review for a Region 9 site stated, “Once the guidance for 

evaluating the vapor intrusion to indoor air pathway is finalized or EPA and [the state 

regulatory agency] can agree to the process for evaluating the pathway, an indoor air risk 

evaluation should be conducted at the Site.” 

•	 The 2007 protectiveness review for a Region 7 site stated, “Revise the vapor intrusion 

risk evaluation after the new TCE toxicity factor is approved by EPA.” 

The protectiveness statements for the three sites were either qualified or limited. The Region 3 

and Region 7 protectiveness reviews stated that the remedies for those sites were protective but 

had qualifications regarding vapor intrusion. The Region 9 protectiveness review could not 

make a protectiveness statement and recommends, among other actions, a vapor intrusion risk 

assessment. 

EPA delays in conducting vapor intrusion risk assessments result in limited assurance that site 

clean-up actions have addressed these potential risks to humans and the environment. 

Scientific and Administrative Issues Are Perceived as Barriers to Issuing 

Final Vapor Intrusion Guidance 

According to Headquarters managers and staff, EPA has not finalized its guidance because the 

2007 ITRC guidance, partly funded and supported by EPA, addressed many issues EPA would 

have included in a final guidance. They also believe finalizing EPA’s guidance would take a 

long time in light of the emerging scientific issues in the field. In addition, if EPA issued vapor 

intrusion guidance, it would have been considered “significant guidance” under Executive Order 

13422. The administrative review process triggered by Executive Order 13422 could be more 

detailed and lengthy.11 However, in January 2009, Executive Order 13422 was revoked.12 

Conclusions 

EPA’s efforts to address vapor intrusion and demonstrate policy positions and environmental 

leadership could be strengthened by updating, finalizing, and broadening the scope of one of its 

primary management controls – its guidance. Final guidance and toxicity values can promote 

effective and transparent enforcement of clean-up standards and requirements. They can also 

11 Executive Order 13422 created the term “significant guidance.” When a guidance document is determined to be 

significant, an administrative review process is triggered. This process includes review by the Office of 

Management and Budget’s Office of Information and Regulatory Affairs. 

12 All significant policy and guidance documents remain subject to review by the Office of Management and 

Budget, Office of Information and Regulatory Affairs under Executive Order 12866. See Office of Management 

and Budget, Memorandum for the Heads and Acting Heads of Executive Departments and Agencies, Guidance for 

Regulatory Review, M-09-13, March 4, 2009. 

8 
 

 

 

10-P-0042 

promote recovery of the government’s clean-up costs, where applicable. Technical papers may 

not be effective for conveying and representing Agency policy. 

Recommendations 

We recommend that the Assistant Administrator for Solid Waste and Emergency Response: 

1. Identify and publicly report the portions of OSWER’s November 2002 draft vapor 

 intrusion guidance that remain valid and the portions that should be updated. 

2. Issue final vapor intrusion guidance(s) that incorporates information on: 

a.	 Updated toxicity values. 

b.	 A recommendation(s) to use multiple lines of evidence in evaluating and 

making decisions about risks from vapor intrusion. 

c.	 How risks from petroleum hydrocarbon vapors should be addressed. 

d.	 How the guidance applies to Superfund Five-Year Reviews. 

e.	 When or whether preemptive mitigation is appropriate. 

f.	 Operations and maintenance, the termination of the systems, and when 

institutional controls and deed restrictions are appropriate. 

3.	 Train EPA and State staff and managers and other parties on the newly updated, 

 revised, and finalized guidance document(s). 

We recommend that the Assistant Administrator for Research and Development: 

4. Finalize toxicity values for TCE and PCE in the IRIS database. 

Agency Comments and OIG Evaluation 

The OIG made changes to the report based on the Agency’s comments where appropriate. 

Appendices B and C provide the Agency comments. 

OSWER agreed with Recommendations 1 through 3, but was unclear about the milestones for 

Recommendations 1 and 2. Based on our follow-up, OSWER provided the milestones of August 

2010 for Recommendation 1 and November 2012 for Recommendation 2. The milestone for 

Recommendation 3 will be May 2013. The recommendations will remain open with agreed-to 

actions pending. 

ORD agreed with Recommendation 4, but was unclear about the milestones for each of the 

toxicity values. Based on our follow-up, ORD provided the milestones of December 2010 for 

the TCE toxicity value and July 2010 for PCE. The recommendation will remain open with 

agreed-to actions pending. 

9 
 

 

 

 

 

 

 

 

 

10-P-0042 

Status of Recommendations and 

Potential Monetary Benefits 

POTENTIAL MONETARY 

RECOMMENDATIONS BENEFITS (in $000s) 

Rec. 

No. 

Page 

No. Subject Status1 Action Official 

Planned 

Completion 

Date 

Claimed 

Amount 

Agreed To 

Amount 

1 

2 

3 

4 

9 

9 

9 

9 

Identify and publicly report the portions of 

OSWER’s November 2002 draft vapor intrusion 

guidance that remain valid and the portions that 

should be updated. 

Issue final vapor intrusion guidance(s) that 

incorporates information on: 

a. Updated toxicity values. 

b. A recommendation(s) to use multiple lines of 

evidence in evaluating and making decisions 

about risks from vapor intrusion. 

c. How risks from petroleum hydrocarbon 

vapors should be addressed. 

d. How the guidance applies to Superfund FiveYear Reviews. 

e. When or whether preemptive mitigation is 

appropriate. 

f. Operations and maintenance, the termination 

of the systems, and when institutional 

controls and deed restrictions are 

appropriate. 

Train EPA and State staff and managers and other 

parties on the newly updated, revised, and finalized 

guidance document(s). 

Finalize toxicity values for TCE and PCE in the 

IRIS database. 

O 

O 

O 

O 

Assistant Administrator, 

Office of Solid Waste and 

Emergency Response 

Assistant Administrator, 

Office of Solid Waste and 

Emergency Response 

Assistant Administrator, 

Office of Solid Waste and 

Emergency Response 

Assistant Administrator, 

Office of Research and 

Development 

August 

2010 

November 

2012 

May 2013 

December 

2010 (TCE) 

and July 

2010 (PCE) 

O = recommendation is open with agreed-to corrective actions pending 

C = recommendation is closed with all agreed-to actions completed 

U = recommendation is undecided with resolution efforts in progress 

10 

1 
 

10-P-0042 

Appendix A 

EPA and Other Regulatory Guidance on 

Vapor Intrusion 

U.S. Environmental Protection Agency. OSWER Draft Guidance for Evaluating the Vapor 

Intrusion to Indoor Air Pathway from Groundwater and Soils (Subsurface Vapor Intrusion 

Guidance). EPA 530-D-02-004, November 2002. 

U.S. Environmental Protection Agency. Office of Solid Waste and Emergency Response. 

Brownfields Technology Primer: Vapor Intrusion Considerations for Redevelopment. EPA 542-

R-08-001, March 2008. 

U.S. Environmental Protection Agency. Office of Solid Waste and Emergency Response. 

Design Solutions for Vapor Intrusion and Indoor Air Quality. EPA 500-F-04-004, March 2004. 

U.S. Environmental Protection Agency. Office of Solid Waste and Emergency Response. 

Superfund Environmental Indicator Guidance Human Health Revisions, March 2008. 

http://www.epa.gov/superfund/accomp/ei/pdfs/final_ei_guidance_march_2008.pdf. 

California Environmental Protection Agency. Department of Toxic Substances Control. Interim 

Final Guidance for the Evaluation and Mitigation of Subsurface Vapor Intrusion to Indoor Air, 

December 15, 2004 (revised February 7, 2005). 

California Environmental Protection Agency. Department of Toxic Substances Control. Vapor 

Intrusion Mitigation Advisory. Draft, December 10, 2008. 

Interstate Technology Regulatory Council. Vapor Intrusion Pathway: A Practical Guideline. 

Technical and Regulatory Guidance, January 2007. 

New Jersey Department of Environmental Protection. Vapor Intrusion Guidance, October 2005. 

Also see 2009 updates at: 

http://www.nj.gov/dep/srp/guidance/vaporintrusion/whatsnew.htm#20090821. 

New York State Department of Health. Center for Environmental Health. Bureau for 

Environmental Exposure Investigation. Guidance for Evaluating Soil Vapor Intrusion in the 

State of New York, October 2006. 

U.S. Air Force, U.S. Navy, U.S. Army. Tri-Services Handbook for the Assessment of the Vapor 

Intrusion Pathway. Rev 4.0. Draft Final, February 15, 2008. 

11 
 

 

10-P-0042 

Appendix B 

OSWER Response to OIG Draft Report 

10/29/09 

MEMORANDUM 

SUBJECT: Response to Draft Evaluation Report: Lack of Final Guidance on Vapor Intrusion 

Impedes Efforts to Address Indoor Air Risks (Project No. 2009-0733). 

FROM: Mathy Stanislaus /s/ 

Assistant Administrator 

TO: Wade Najjum 

Assistant Inspector General 

Office of Program Evaluation 

 Thank you for the draft evaluation report of September 29, 2009, Lack of Final Guidance 

on Vapor Intrusion Impedes Efforts to Address Indoor Air Risks (Project No. 2009-0733). In 

general, we concur with your recommendations, and we are providing schedules for completing 

the various activities. We will seek input from the public on our efforts, and the schedules 

reflect this important step. 

We appreciate the important role of EPA guidance in addressing risks from vapor 

intrusion and understand that final guidance will be beneficial. We also recognize the important 

role of our State and Tribal co-regulators who have the authority to establish and enforce 

standards in their jurisdiction. Likewise, we believe it is important to acknowledge that the EPA 

regions and OSWER program offices have continually taken steps to address risk from vapor 

intrusion using draft guidance. 

The science and technology associated with evaluating and addressing risk from vapor 

intrusion is complex and evolving. A considerable amount of new information has become 

available since the draft 2002 OSWER Guidance for Evaluating the Vapor Intrusion to Indoor 

Air Pathway from Groundwater and Soil (Subsurface Vapor Intrusion Guidance) EPA 530-D-02-

004 was prepared. We concur with the recommendation (#1) to identify the portions of 

OSWER’s November 2002 draft vapor intrusion guidance that remain valid and the portions that 

may need to be updated. OSWER will release the results of this review by the summer of 2010. 

We also concur with the recommendation (#2) to issue final vapor intrusion guidance(s) 

that incorporates information on: 

•	 sustainable vapor intrusion mitigation, operations and maintenance, the termination of the 

systems, and when institutional controls and deed restrictions are appropriate, 

12 
 

 

10-P-0042 

•	 when, or if, preemptive mitigation is appropriate, 

•	 a recommendation(s) to use multiple lines of evidence in evaluating and making decisions 

about risks from vapor intrusion, 

•	 how risks from petroleum hydrocarbon vapors should be addressed, 

•	 updated toxicity values, including TCE and PCE, and 

•	 how the guidance applies to Superfund Five-Year reviews. 

In addition to these recommendations, OSWER plans to address other relevant topics 

(e.g., monitoring effectiveness of mitigation systems). Multiple guidance documents may be 

needed to update parts of the 2002 draft guidance and to address the issues raised in 

recommendation #2. We will seek public input early in the development of each document, 

interagency review, and external peer review. If multiple documents are developed they will be 

released as soon as possible with the final document being completed by the fall of 2012. 

We concur with the recommendation (#3) to train EPA and State staff and managers, and 

other parties, on the newly updated, revised, and finalized guidance document(s). We also intend 

to provide outreach information that is appropriate for individuals that are not environmental 

professionals, for example members of the public. We will develop training materials within six 

months from the release of the guidance document(s). 

We have attached a marked-up version of the draft report with suggestions to improve 

technical accuracy. One comment that we would like to highlight is interchangeable use of the 

terms toxicity values and exposure levels. We would also like to note that “standards” are 

typically considered to be values that have been promulgated and enforceable values. In closing, 

we would like thank you again for the draft evaluation report. 

Attachment 

13 
 

 

 

 

 

10-P-0042 

Appendix C 

ORD Response to OIG Draft Report 

10/29/09 

MEMORANDUM 

SUBJECT: ORD Response to Draft OIG Report, Lack of Final Guidance on 

Vapor Intrusion Impedes Efforts to Address Indoor Air Risks, 

Project No. 2009-0733 

FROM: Lek G. Kadeli /s/ Kevin Teichman for

Acting Assistant Administrator (8101R) 

TO: Wade Najjum 

 Assistant Inspector General 

Office of Program Evaluation (2460T) 

Thank you for the opportunity to comment on the Draft OIG Report, Lack of Final Guidance 

on Vapor Intrusion Impedes Efforts to Address Indoor Air Risks, dated September 29, 2009. We 

have reviewed the draft report and generally concur with the findings as well as the one 

recommendation addressed to our office. Our comments are as follows: 

ORD understands the importance of being able to provide updated vapor intrusion guidance 

to the public and is moving ahead to complete the Agency's toxicological reviews for the two 

compounds identified in subject draft report under Recommendation 4 and enter them into the 

IRIS database. Both are high priorities for ORD and are in varying stages of completion. 

Predicting schedules for the completion and final posting of the assessments for these 

chemicals is difficult due to the variations in duration that may be experienced at different steps 

in the development, review and finalization process. Below, we present a synopsis of where the

chemicals are in the review cycle, offer an anticipated completion date for the next milestone in 

the process, and projected completion dates. 

Trichloroethylene (TCE)

The Interagency Science Consultation on the Draft Toxicological Review of 

Trichloroethylene (TCE) was held on Tuesday, September 22, 2009. Comments from the 

review are being considered, and it is expected that the draft document will be released for 

External Peer Review and public comment in early November 2009. Projected completion

date for TCE is winter 2010. 

Tetrachloroethylene (PERC)

The draft Toxicological Review of Tetrachloroethylene /Perchloroethylene(PERC) is 

currently undergoing External Peer Review by the National Academy of Sciences (NAS), 

and a prepublication draft of their final report is expected in late December 2009. 

Publication of the final NAS peer review report is expected by the end of March 2010. 

Projected completion date for PERC is summer 2010. 

14 
 

 

 

 

 

 

10-P-0042 

For both chemicals, it is very difficult to predict how long subsequent revisions and editing 

of the Toxicological Reviews may take until we understand the nature and extent of the 

comments and recommendations made by the reviewers. Finalization dates provided here

represent our current best projection for completing these assessments. Updated schedules for

both of these chemicals and many others are always available on the IRISTrack website at: 

https://cfint.rtpnc.epa.gov/ncea/iristrac/index.cfm?fuseaction=listChemicals.showList 

Finally, we would like to clarify the purpose of these assessments and the information they 

provide. A toxicity assessment for IRIS provides an “inhalation unit risk” or an “oral cancer 

slope factor” for cancer that allows the risk to be calculated for various exposure scenarios. For 

non-cancer effects, the quantitative aspect is usually represented by a value (a concentration in 

air or an oral dose) such that if exposure is continuously below that value it is likely there will be 

no appreciable risk of deleterious effects. These toxicity values are not estimates of the current 

risk in any particular population because they do not include analysis of current exposure 

patterns. These are also not regulatory standards, although they may be used by EPA and others 

to decide upon regulatory standards appropriate to various situations. The term “exposure level” 

is used in the draft OIG report in several places where the term “toxicity value” should be used: 

•	 In the “At A Glance” summary in the last two paragraphs 

•	 Page 2, last sentence of the first paragraph 

•	 Page 2, second to last paragraph, second sentence 

•	 Page 8, “Conclusions” section, second sentence 

•	 Page 9, Recommendation #4, “exposure levels” should be either “toxicological reviews” 

or “toxicity values” 

ORD Corrective Action plan for Recommendation 4 

Recommendation Action Official Corrective Action Anticipated Completion Date 

4. Finalize exposure levels 

for TCE and PCE in the 

IRIS database. 

Assistant Administrator, 

Office of Research and 

Development 

ORD will finalize the 

toxicological reviews for 

TCE and PCE by 

completing the following 

steps for each chemical 

1. Draft Development 

2.Agency Review 

3.Interagency Review 

4. External Peer Review 

5. Final Assessment 

TCE-winter 2010 

PCE-summer 2010 

For both chemicals, it is very 

difficult to predict how long 

subsequent revisions and 

editing of the Toxicological 

Reviews may take until we 

understand the nature and 

extent of the comments and 

recommendations made by 

the reviewers. Finalization 

dates provided here represent 

our current best projection for 

completing these assessments. 

Should you or your staff have questions or require further information, please have them 

contact David Bussard at (703) 347-8647. 

15 
 

10-P-0042 

cc: Kevin Teichman 

 Donna Vizian 

 Amy Bataglia 

 Deborah Heckman 

 Jorge Rangel 

 Peter Preuss 

 Kathleen Deener 

 Ardra Morgan-Kelly 

 David Bussard 

 Gina Perovich 

16 
 

 

 

10-P-0042 

Appendix D 

Distribution 

Office of the Administrator 

Assistant Administrator, Office of Solid Waste and Emergency Response 

Acting Assistant Administrator, Office of Research and Development 

Regional Administrators, Regions 1-10 

Agency Follow-up Official (the CFO) 

Agency Follow-up Coordinator 

Principal Deputy Assistant Administrator, Office of Solid Waste and Emergency Response 

Deputy Assistant Administrator for Science, Office of Research and Development 

Acting Deputy Assistant Administrator for Management, Office of Research and Development 

General Counsel 

Associate Administrator for Congressional and Intergovernmental Relations 

Associate Administrator for Public Affairs 

Director, Office of Superfund Remediation and Technology Innovation, 

 Office of Solid Waste and Emergency Response 

Deputy Director, Office of Superfund Remediation and Technology Innovation, 

 Office of Solid Waste and Emergency Response 

Director, Office of Resource Conservation and Recovery, Office of Solid Waste and 

 Emergency Response 

Deputy Director, Office of Resource Conservation and Recovery, Office of Solid Waste and 

 Emergency Response 

Director, Office of Brownfields and Land Revitalization, Office of Solid Waste and 

 Emergency Response 

Deputy Director, Office of Brownfields and Land Revitalization, Office of Solid Waste and 

 Emergency Response 

Director, Office of Underground Storage Tanks, Office of Solid Waste and Emergency Response 

Director, National Center for Environmental Assessment, Office of Research and Development 

Deputy Director, National Center for Environmental Assessment, Office of Research and 

 Development 

Audit Follow-up Coordinator, Office of Solid Waste and Emergency Response 

Audit Follow-up Coordinator, Office of Research and Development 

Audit Follow-up Coordinators, Regions 1-10 

Acting Inspector General 

17