Quantifying the Air Pollution Exposure Consequences of - Houston ...

generated (SB 1298, 1999). All new DG units installed after 2003 are required to meet
the best performance achieved in practice by any DG technology. By 2007, CARB will
require that all new DG units achieve parity with central stations equipped with the best
available control technology (BACT 6 ) (CARB, 2002). In this way, CARB is seeking to
make newly installed DG no worse for air quality in terms of emission factors than would
be a new central station plant.
Most prior research related to the environmental impact of DG has been aligned
with CARB’s approach, focused on assessing the potential for increased air pollutant
mass emissions into particular air basins or states from widespread deployment of DG
(California: Iannucci et al., 2000; Allison and Lents, 2002. Texas: Hadley and Van Dyke,
2003. Mid-Atlantic states: Hadley et al., 2003a; Hadley et al., 2003b. New York:
Williams et al., 2003). The implicit assumption is that a given mass emitted from DG
sources poses the same potential for adverse health consequences as an equal mass from
central stations, an assumption our preliminary research has suggested is invalid (Heath
et al., 2003). Other recent research has been motivated by a concern for the ability of
localities, air basins and states to meet the National Ambient Air Quality Standards
(NAAQS) and other mandates with increased use of DG. Medrano et al., (2003) used an
Eulerian airshed model to predict primary and secondary criteria pollutant concentrations
under different scenarios of widespread DG deployment in the South Coast Air Basin
(SoCAB). Based on preliminary modeling, they found that criteria pollutant
concentrations could change both nonuniformly and nonintuitively throughout the
SoCAB, and could lead to significant concentration increases under certain deployment
scenarios (Medrano et al., 2003; Samuelsen et al., 2003).
An important factor in any assessment of the environmental impacts of DG is the
potential effects of DG emissions on population exposure to air pollutants. Central-station
power plants emit pollutants from tall stacks, often remotely located from population
centers. DG technologies emit their pollutants closer to the ground, typically in more
densely populated regions. Closer proximity between emissions and people can cause
greater exposures and therefore greater health risk from pollutant emissions, even if the
total mass emitted is unchanged.
The aim of this report is to explore the effects of a shift in release location on
human inhalation intake of pollutants emitted from baseload electricity generation
facilities. We use this information to provide an estimate of the emission factors
necessary for DG technologies to equalize the exposure burden of comparable central
station facilities. To accomplish these objectives, we use a common air dispersion
modeling method to compare estimates of the annual-average population intake of
pollutants emitted from the two paradigms of electricity generation: distributed
generation and central station. This study contributes to a better understanding of the
implications of a fundamental shift in the range and scale of technologies used to
generate electricity. The results will also suggest fruitful directions for future research to
substantiate and refine our findings. This research builds on the work of others who have
looked at the question of population intake from central stations (Levy et al., 2003; Li
and Hao, 2003; Zhou et al., 2003; Evans et al., 2002; Levy et al., 2002a; Levy et al.,
2003; Nigge, 2001; Smith, 1993). This report substantially extends their analyses by
6 The same acronym, BACT, is used in the context of California and US regulations. Throughout this
report, “BACT” refers to the California BACT standard.
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