Regulatory Guidance and Legislative Issues
As of December 2009, more than half of U.S. states had issued
regulations or developed guidance documents to assist in VI investigations. Table 1 summarizes the key legal and technical
guidance for VI. Other groups that have developed VI guidance
include the Department of Defense, U.S. Postal Service, American
Petroleum Institute and Canadian Government.
EPA intends to update and finalize its 2002 draft guidance
on VI by 2012. The agency has been criticized for outdated toxicity values for several chlorinated compounds and delays in
conducting vapor intrusion risk assessments at Superfund sites.
The New Jersey Department of Environmental Protection
(NJDEP) Vapor Intrusion Guidance document is undergoing
major revisions to reflect policy changes associated with the
Licensed Site Remediation Professional program. These include
changes in indoor air and sub-slab soil gas sampling requirements for VI investigations involving sensitive populations, such
as child-care centers, schools and residential properties, and initial triggers, such as exceedance of a groundwater screening
level. The revisions also introduce a new concept, “immediate
environmental concern” (IEC), which applies to sites where indoor air contaminant concentrations exceed residential or non-residential indoor air screening levels. The IEC guidance includes
requirements for public notification on a rigorous timeframe.
The NJDEP website includes frequently asked questions
( www.state.nj.us/dep/srp/guidance/vaporintrusion/faqs.htm) and
updates of the Evaluating Indoor Air Near VOC Contaminated
Sites document and screening levels ( www.state.nj.us/dep/
The NJDEP also issued modifications to the EPA TO- 15 sampling and analytical method for VOCs, which call for a lower
reporting limit (less than 0.20 ppbv for 15 target analytes) and
additional quality control requirements. The state certifies laboratories in this new modified Low Level TO- 15 method.
In September 2008, the governor of New York signed legislation that requires residential and non-residential property owners and landlords to notify their tenants and occupants of any
test results related to indoor air contamination associated with
vapor intrusion if the results exceed either a New York State
Department of Health guideline or an OSHA guideline for indoor air quality.
Indoor Air and Background VOC Levels
The goal of VI investigations is to evaluate the potential or actual presence of subsurface chemical contaminants in the indoor environment and the long-term exposure risk of building
occupants. The EPA’s Johnson and Ettinger model has been
shown to predict higher attenuation factors than those actually
measured at sites; that is, indoor air concentrations have been
higher than the model has predicted.
Industrial hygienists can apply their experience in indoor air
quality investigations to VI indoor air investigations. Preliminary walk-though building surveys can identify potential background VOC sources, vapor infiltration pathways and entry
points, and evidence of wet basements or groundwater infiltration. Reviews of chemical inventories, product labels and material safety data sheets can help determine whether the chemical
components are identical to known subsurface contaminants.
Interviews with procurement or EHS staff can indicate whether
Indoor air quality sampling with a Summa canister
in a commercial office building.
the facility has prohibited the use of products with specific
chemicals. Interviews with building occupants may reveal details regarding odor or health complaints and recent renovation
or maintenance activities.
The NJDEP does not require indoor air samples in buildings
where active operations use, handle or store the same contaminants
of concern. But NJDEP recognizes that such sampling may help
identify the relative contribution to indoor air from background
sources (including site processes) and vapor intrusion. Sampling is
also useful in facilities where use of contaminants is limited.
Indoor air sampling is the most direct method of determining
whether the vapor intrusion pathway is complete and whether
building occupants face a long-term health risk. Indoor air data
integrates all contributing factors from the subsurface, above
the ground, and the building itself. Indoor air samples and concurrent sub-slab soil gas data can help industrial hygienists select appropriate responses to protect occupants, such as
additional air sampling, mitigation or other measures.
The EPA and several state websites provide tables of indoor air,
background/ambient VOC, and soil gas data from their remedial
program VI investigations. Additionally, indoor air quality studies
at residences not impacted by subsurface contamination are being
conducted by several states to provide a statistical basis for assessing background air quality. According to the EPA Indoor Air
Vapor Intrusion Database ( http://iavi.rti.org/), the predominant vapors found in indoor air are chlorinated hydrocarbons and petroleum hydrocarbons.
California guidance allows comparisons of indoor air sampling
data to either state VI screening levels or occupational exposure
limits for nonresidential facilities that use the same chemicals as
the subsurface contaminants. Colorado guidance applies risk-based
screening levels to all buildings where employees “have not volun-