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U.S. Environmental Protection Agency	10-P-0042
December 14, 2009
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Office of Inspector General
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At a Glance
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Why We Did This Review
We conducted this review to
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issued draft guidance.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.aov/oia/reports/2010/
20091214-10-P-0042.pdf
Catalyst for Improving the Environment\
Lack of Final Guidance on Vapor Intrusion
Impedes Efforts to Address Indoor Air Risks
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 EPA's draft also contains outdated toxicity values for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EPA's draft guidance does not address mitigating vapor intrusion risks or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 The draft guidance also does not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 The draft guidance is not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.

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