(VCCEP) Tier 1 Pilot Submission for BENZENE - Tera

7.2 Sources of Benzene Exposure
Childrens’ exposures to benzene were quantified based on information provided in the scientific
peer-reviewed literature or through exposure modeling using various EPA exposure models.
The sources of benzene have been defined in terms of two general source categories: ambient
sources of exposures and exposures resulting from specific sources.
7.2.1 Ambient Environmental Exposures
Ambient childhood exposures to benzene could occur from four general sources: 1) ambient air,
2) food, 3) drinking water, and 4) human milk. Potential exposures to each source are described
further below.
7.2.1.1 Ambient Air
During the 1980s and early 1990s the EPA funded and provided oversight for human exposure
research with the objective of directly measuring exposure to VOCs using personal air
samplers. The conclusion of this extensive research project, known as the EPA Total Exposure
Assessment Methodology (TEAM) Studies, was that the most important sources of exposure
are small and originate close to the person (Wallace, 2001). The presence of major point
sources, such as refineries and chemical facilities, was not correlated with increased personal
exposure to organic chemicals. For many chemicals, including benzene, distant sources of air
releases play a smaller part in the determination of total exposure than localized sources such
as use of petroleum products, time spent in vehicles, and use of tobacco products.
The Clean Air Act Amendments of 1990 provided for creation of the National Urban Air Toxics
Research Center (NUATRC). The goal of this organization is to promote, develop and support
research related to human health risks from air toxics. As part of the NUATRC mission, several
studies were conducted where VOC exposures to children were evaluated. The Health Effects
Institute (HEI) and the Mickey Leland National Urban Air Toxics Research Center (NUATRC)
jointly funded a project called the Relationship between Indoor, Outdoor and Personal Air
(RIOPA); a large urban air toxics project that was comprised of three studies. The RIOPA
project tested the hypothesis that personal exposure to air toxics is influenced by outdoor
sources of these air toxics. It involved 3 cities with different air pollution source profiles: Los
Angeles, California is dominated by mobile sources; Houston, Texas is dominated by industrial
point sources; and Elizabeth, New Jersey includes a mixture of mobile and point sources. In
each city, 100 homes were monitored for 48 hours in each of 2 seasons. The homes were
monitored indoors and outdoors for particulate matter smaller than 2.5 microns (PM2.5), VOCs,
and aldehydes. In addition, personal exposure to PM2.5, VOCs, and aldehydes, and in-vehicle
exposure to aldehydes were measured for residents of these homes. In general it was found
that indoor air benzene concentrations were higher than outdoor air, but lower than the personal
benzene concentrations.
A community based study conducted by Buckley et al., (2005) in Baltimore also evaluated the
impact of industry on community air quality and individual resident exposure to15 VOCs. The
study was designed to examine the potential industry effect by comparing indoor, outdoor, and
personal air concentrations in South Baltimore to those in Hampden, an urban Baltimore
community with a less intense industrial presence. Buckley et al. concluded that except for
ethylbenzene and m,p-xylene, the VOC concentrations at all three levels of monitoring (outdoor,
indoor, and personal) were comparable in the two communities, suggesting no industrial impact
or an impact smaller than that detectable with the sample size of the study. For the two
Benzene VCCEP Submission
March 2006
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