[CPEO-BIF] Indoor Air Pathway

[Lenny Siegel <lsiegel@cpeo.org>]

United States: Increased Scrutiny of Indoor Air Pathway Shifts Standards
for Investigation and Clean-Up

Gregory A. Bibler and Elizabeth F. Mason 
Goodwin Procter LLC (via Mondaq)
November 10, 2004
Originally published October 2004

Recent technical guidance from the U.S. Environmental Protection Agency
("EPA") and emerging new standards and regulations from state
environmental agencies target inhalation of vapors migrating from
contaminated soil and groundwater into buildings as an exposure pathway
that must be addressed in risk assessments and clean-up plans. This
increased regulatory attention to the potential for particular
chemicals, volatile organic compounds ("VOCs"), detected in the
subsurface to migrate into buildings poses the prospect for more
rigorous clean-up standards for soil and groundwater, and for additional
monitoring and controls for indoor air. In its five-year reviews of
Superfund sites where VOCs remain in concentrations above levels that
allow for unlimited use and unrestricted exposure, in fact, EPA is
reevaluating remedies to determine whether vapor intrusion poses an
unacceptable risk to human health.

Companies charged with managing the investigation and clean-up of sites
that have VOCs in soil or groundwater not only need to be aware that
agencies may demand data demonstrating that the indoor air pathway has
been adequately addressed; they also should take steps early in the
assessment process to control both the measurement and the perception of
this potential exposure. A thoughtful conceptual model must be developed
for characterizing the potential interaction between subsurface
conditions ? including geology, utility corridors, depth to groundwater
surface, and chemical concentrations in soil and groundwater ? and
existing or future structures on the surface. Based on that model,
information should be collected in a logical sequence calculated to
control both the costs of the investigation and the impact of any data
collected on public perception, including that of workers, tenants, and
adjoining landowners.

In scoping the investigation of a site where vapor intrusion may be an
issue, companies should be mindful that mathematical models and
regulatory standards which EPA and state agencies now use to measure
risk depend heavily on conservative default values. Initially, these
models and standards may be used as a screening tool to determine
whether site conditions warrant closer examination. Where these
screening levels are exceeded, collecting additional soil vapor or
indoor air data to substitute for regulatory default values, and
conducting a more rigorous risk assessment using site-specific data,
typically will produce more representative and reliable calculations of
exposures, risks, and remedial objectives.

...

For the entire article, link to http://www.mondaq.com/i_article.asp?articleid=29487&ASIMPR=128&ASTAGS=ad.size.Banner+product.9+type.article
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Lenny Siegel
Director, Center for Public Environmental Oversight
c/o PSC, 278-A Hope St., Mountain View, CA 94041
Voice: 650/961-8918 or 650/969-1545
Fax: 650/961-8918
<lsiegel@cpeo.org>
http://www.cpeo.org
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