Implications of Incorporating Residential and non-Residential Indoor Air Background Concentrations


Implications of Incorporating Residential and non-Residential Indoor Air Background Concentrations

Gina Plantz, Richard Rago and Jay Peters (Haley & Aldrich, Inc.)


Gina Plantz

Haley & Aldrich, Inc.

Speaker Bio:

Gina Plantz is a Principal Consultant with Haley & Aldrich, Inc. and holds a Bachelor of Science degree in Chemistry from Widener University. Gina has over 20 years experience in leading complex, multi-stakeholder investigation and remediation programs and management and oversight of vapor intrusion investigations at sites contaminated with chlorinated solvents, manufactured gas plant residues and petroleum hydrocarbons. For the past 8 years, Gina has been directing a large investigation and remediation program for a California utility company which includes evaluating soil, groundwater, the vapor intrusion pathway and sediments at multiple sites.  Gina has lectured on the topics of MGP investigations and remediations, vapor intrusion pathway evaluation, forensic chemistry, stakeholder engagement and risk communication.


The presence of volatile organic compounds (VOCs) as a background condition in residential and non-residential indoor air has been well documented. Although consumer product formulations and building materials have changed, recent studies confirm that many volatile compounds, including benzene and naphthalene, are still commonly encountered in indoor air background. Buildings located near former MGP sites can be particularly vulnerable to conventional predictions for vapor intrusion evaluations, which can lead to unnecessary investigations including multiple rounds of indoor air samples. While the identification of consumer products containing these ubiquitous VOCs are typically considered as a line of evidence in evaluating vapor intrusion from subsurface VOC sources to indoor air, the health risks that may be associated with indoor air background concentrations are often not examined. Yet, risks associated with indoor air background conditions may substantially contribute toward or exceed risk management thresholds used by various states and the EPA. Consequently, the implications of indoor air background on health risks should be understood and acknowledged in risk management decision-making. This presentation will provide a characterization of health risks associated with residential and non-residential indoor air background VOC concentrations. Risks will be presented for a range of statistically-based background concentrations obtained from over three thousand samples collected as part of previous and recent indoor air background studies conducted across the United States. Our findings support that background indoor air concentrations of several VOCs, including benzene and naphthalene, are above risk-based screening levels and are associated with health risks above risk management thresholds commonly used by regulatory agencies. Furthermore, our results imply that groundwater, soil vapor, and indoor air vapor intrusion screening levels for several commonly detected VOCs, including benzene and naphthalene, are correlated with indoor air concentrations that are in the range of typical background levels. The implications of these findings on vapor intrusion investigations and response action decisions will be discussed.

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