Academic journal article Journal of Environmental Health

Community Exposures to Chemicals through Vapor Intrusion: A Review of Past Agency for Toxic Substances and Disease Registry Public Health Evaluations

Academic journal article Journal of Environmental Health

Community Exposures to Chemicals through Vapor Intrusion: A Review of Past Agency for Toxic Substances and Disease Registry Public Health Evaluations

Article excerpt

Introduction

Volatile contaminants in subsurface soil or groundwater can migrate up into buildings--vapor intrusion--and present a unique inhalation exposure pathway. As U.S. Environmental Protection Agency (U.S. EPA) and Agency for Toxic Substances and Disease Registry (ATSDR) awareness of this phenomenon increases, the large number of historical solvent and petroleum releases is resulting in an ever-increasing number of sites with a vapor intrusion component. This column summarizes information showing which chemicals occur most frequently above screening values at sites ATSDR has reviewed and how many of the sites with these contaminants were classified as a public health hazard. The potential for vapor intrusion and possible adverse health effects to building occupants are important pieces of information for communities to be aware of, especially during redevelopment activities and land use decision making.

Background

Volatile organic chemicals (VOCs) are among the most common contaminants released into the environment from hazardous waste sites. In addition to contaminating groundwater and soil, these chemicals may off-gas from these two media and migrate up into the air of homes and commercial buildings. Figure 1 illustrates the potential vapor intrusion conduits into buildings. If vapors build up indoors levels may lead to the following health and safety issues: fire; explosion; and acute, intermediate, and chronic health effects (Agency for Toxic Substances and Disease Registry [ATSDR], 2008).

Methods

In 2009, an ATSDR intern reviewed 135 vapor intrusion public health assessments and consultations on 121 sites published on ATSDR's Web site between 1994 and 2009. Here we report the following: contaminant(s), maximum indoor air concentration, and health hazard category. ATSDR assigns one of five health hazard categories to summarize the risks of particular chemical exposures at a site. The categories range from "urgent public health hazard" to "no public health hazard (ATSDR, 2005)." Information on the source of indoor air contamination was also collected (e.g., groundwater, soil gas, crawl space gas, and outdoor air data).

We ranked chemicals detected in indoor air according to the frequency that they were found and the frequency in which they exceeded ATSDR comparison values (CVs). Our CVs are chemical and media-specific concentrations used by ATSDR health assessors and others to identify environmental contaminants at hazardous waste sites that require further evaluation. Evaluating chemicals present above CVs involves analysis of site-specific exposure factors and toxicologic studies (ATDSR, 2005). Lastly, we examined which chemicals resulted in sites being declared a health hazard.

Results

Of the 135 reports evaluated (121 sites), 119 (88%) were written after U.S. EPA's 2002 draft guidance for evaluating vapor intrusion was published (U.S. Environmental Protection Agency [U.S. EPA], 2002). Figure 2 shows the increasing number of vapor intrusion site reports published each year since 1994.

Figure 3 shows these site locations and highlights those where ATSDR determined a public health hazard existed. As with many other types of ATSDR evaluations, the locations are highly concentrated in densely populated cities and areas historically associated with heavy industry. In addition, vapor intrusion sites have historically been more focused in the colder northern regions where the stack effect is considered more pronounced. In the stack effect, heated building interiors and higher winds at rooftops draw air out near the roof creating negative pressure inside the building and drawing in subsurface vapors.

Our review identified 119 VOCs and semivolatile organic compounds in indoor air, groundwater, ambient air, and soil gas. Ninety-five (80%) of the chemicals were detected in indoor air. Fifteen of these exceeded a CV or combustible hazard criteria and only five were responsible for declaring public health hazards (Table 1). …

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