&EPA
United Sates
EirvirofimnU Protection
Agency
Survey of New Findings in Scientific
Literature Related to Atmospheric Deposition
to the Great Waters:
Polycyclic Aromatic Hydrocarbons (PAH)
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EPA-452/R-07-011
December 2007
Survey of New Findings in Scientific Literature
Related to Atmospheric Deposition to the Great Waters:
Polycyclic Aromatic Hydrocarbons (PAH)
U.S. Environmental Protection Agency
Office of Air Quality Planning and Standards
Health and Environmental Impacts Division
Climate, International and Multimedia Group
Research Triangle Park, North Carolina
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Cover Photograph Credits:
Photo by Eric Vance, U.S. EPA
Photo by
Eric Vance,
U.S. EPA
Photo by Eric Vance, U.S. EPA
Photo by S.C. Delaney, U.S. EPA
Photo Courtesy of National
Oceanic and Atmospheric
Administration/ Department of
Commerce
Photo Courtesy of National
Oceanic and Atmospheric
Administration/ Department
of Commerce
11
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Survey of New Findings in Scientific Literature Related to Atmospheric
Deposition to the Great Waters:
Polycyclic Aromatic Hydrocarbons
1.0 Introduction and Highlights
Atmospheric deposition of pollutants,
including polycyclic aromatic
hydrocarbons (PAH), is recognized as
a significant contributor in many
locations to water quality problems,
including toxic contamination of the
fish and shellfish living in the waters.
PAH are a subset of a set of
compounds known as polycyclic
organic matter (POM), which are
organic compounds primarily formed
from the incomplete combustion of
organic materials, such as coal and
wood. Several PAH compounds have
been classified as probable human
carcinogens (ATSDR 1995).
The U.S. Environmental Protection
Agency (U.S. EPA) has been directed
by the Clean Air Act to consider the
contribution of atmospheric deposition
to pollution in the "Great Waters,"
which comprise the Great Lakes, Lake
Champlain, Chesapeake Bay, and
many of the estuaries of the coastal
United States.1 POM are included in
the group of pollutants of concern for
the Great Waters.2 Background
information on the sources, deposition,
and environmental concentrations of
the pollutants of concern is
summarized in detail in a series of
reports, the most recent of which is
HIGHLIGHTS
Polycyclic Aromatic Hydrocarbons
> Long-term Temporal Trends. No consistent long-term
trends in PAH deposition are reported for the Great Lakes
region. In Chicago, however, PAH concentrations in
precipitation and ambient air are decreasing. In mollusks, a
decreasing trend in the national median concentration is
becoming apparent, although at most of the individual sites,
no trends are evident. In lake sediments in several urban
areas, PAH concentrations have been increasing over the past
20 to 40 years.
> Seasonal Trends. Studies in multiple areas found higher PAH
air concentrations and deposition during winter. This trend
was attributed in part to domestic heating. No seasonal trends
were found in PAH concentrations in surface water and
zooplankton in southern Lake Michigan, near Chicago,
indicating relatively constant PAH deposition.
> Spatial Trends. The new studies echo the findings in the
Third Report to Congress that PAH air concentrations and
deposition are greater in urban and industrial areas than in
rural areas. There are several newly-studied geographic areas,
including Tampa Bay, San Francisco Bay, and the New Jersey
coast. A variety of statistical modeling techniques were used
to examine the source regions that influence the Great Lakes.
Two studies demonstrated passive sampling techniques to
look at spatial trends.
^ Emissions and Source Profiles. The dominant sources of
emissions of 15 PAH compounds nationally are related to
residential, wood-fired boilers, and open burning. The
distribution of sources varies by region, with significant
sources including vehicular traffic, coal combustion, coke
ovens, jet exhaust, and natural gas combustion.
The estuaries that are part of the Great Waters are those that part of the National Estuary Program (NEP) administered
by EPA or the National Estuarine Research Reserves (NERR) Program administered by the National Oceanic and
Atmospheric Administration (NOAA).
2 The Great Waters pollutants of concern include POM, mercury, cadmium and lead (and their compounds), several
banned or restricted pesticides, polychlorinated biphenyls (PCB), nitrogen compounds, tetrachlorodibenzo-p-dioxin,
and tetrachlorodibenzofuran. More specific information is at http://www.epa.gov/oar/oaqps/gr8water.
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"Deposition of Air Pollutants to the Great Waters Third Report to Congress" (U.S. EPA 2000),
hereafter referred to as "the Third Report to Congress."
U.S. EPA is no longer required to submit reports to Congress on deposition of air pollutants to the
Great Waters. However, much new information related to environmental concentrations, deposition
trends, and sources of PAH in the Great Waters has been published since the Third Report to
Congress, and is compiled here. The recent research also is compared to findings described in the
Third Report to Congress. Much of the information in this survey report relates to recent findings
in temporal and spatial trends in both the Great Lakes and Chesapeake Bay regions. Other studies
address the creation of new source profiles in different areas. For example, studies for Galveston
Bay and the city of Miami have recently been completed, which detail sources of PAH to these
regions. Highlights of long-term temporal and seasonal trends, findings and spatial trends in
various locations, and sources and emissions from the newly published scientific literature are
presented in the textbox in this section.
References are provided at the end of this
summary.
2.0 Temporal Trends
One area of new research since the Third
Report to Congress concerns temporal
trends of PAH associated with deposition
and concentrations in environmental
media. Findings relating to long-term
temporal and seasonal PAH trends are
discussed below.
2.1 Long-term Trends
2.1.1 Ambient Air and Deposition
All recent literature regarding long-term
temporal trends in ambient air and
deposition for PAH pertains to the Great
Lakes region. The trends analyses are
based on data measured at sites in the
Integrated Atmospheric Deposition
Network (IADN). The IADN consists of
monitoring stations located on each of the
Great Lakes since 1990 and at several
satellite locations in the surrounding areas
in both the United States and Canada. Gas
and particle-phase air samples and
precipitation data are collected throughout
the year for several pollutants, including 13
PAH compounds (Buehler and Kites
2002). This new data demonstrates that
DEFINITIONS OF COMMON TERMS
Direct deposition: The process of deposition of air
pollution directly into a body of water (e.g., a large
body of water like an estuary or large lake). The
amount of pollution reaching the water in this way
is called the direct load from atmospheric
deposition.
Indirect deposition: The process of deposition of
air pollution to the rest of the watershed (both the
land and the water). Once pollutants are deposited
in the watershed, some portion is transported
through runoff, rivers, streams, and ground water to
the waterbody of concern. The portion that reaches
the waterbody by passing through the watershed is
called the indirect load from atmospheric
deposition.
Wet deposition: Pollutants deposited in rain, snow,
clouds, or fog. Acid rain, which has been
recognized as a problem in Europe, eastern
Canada, Asia, and areas of the United States, is an
example of wet deposition of sulfur and nitrogen
compounds.
Dry deposition: Pollutants deposited during
periods of no precipitation. This is a complicated
process that happens in different ways depending
on the size and chemical nature of the particle or
gas being deposited and the "stickiness" of the
surface. Dry deposition of particles can be thought
of as similar to dust collecting on a table.
Source: U.S. EPA 2001
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heavier PAH compounds (e.g., benzo(a)pyrene) enter the lakes from the atmosphere through wet
deposition and dry deposition of particles, whereas the lighter PAH compounds (e.g.,
phenanthrene) enter through gas absorption (EC and U.S. EPA 2004).
There are consistent long-term trends neither in PAH measurements in ambient air nor in PAH
deposition loading throughout the Great Lakes region. This lack of consistent trends echoes the
Third Report to Congress, and is congruous with the fact that PAH compounds continue to be
emitted to the atmosphere, largely as the byproduct of incomplete combustion (Buehler and Kites
2002, EC and U.S. EPA 2004). Once in the atmosphere, PAH are transferred continuously between
air, water, and soil by natural chemical and physical processes such as weathering, runoff,
precipitation, dry deposition of dust, and stream/river flow (see Figure 1).
Figure 1. Atmospheric Release, Transport, and Deposition Processes
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located
Source: U.S. EPA 2000
Several studies reported trends analyses of IADN data for total PAH concentrations in
precipitation, the particle phase in ambient air, and the gas phase in ambient air as shown on
Table 1. Results are reported for three U.S. sites: Eagle Harbor site near Lake Superior, the
Sleeping Bear Dunes site near Lake Michigan, and the Sturgeon Point site near Lake Erie. These
sites are situated to measure regional background levels of pollutants.
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Table 1. Long-Term Atmospheric Trends in Total PAH Concentrations
in the Great Lakes Region between 1991 and 2003
PAH
Measurement
Precipitation
Ambient particle phase
Ambient gas phase
Years
1991-1997
1997-2003
1991-1997
1996-2003
1991-1997
1996-2003
Lake
Superior
<->
<->
<— >
<— >
4
4
Lake
Michigan
<->
<->
4
<->
4
4
Lake
Erie
<->
<->
<— >
4
4
4
Source
Simcik et al. 2000
Sun et al. 2006a
Cortes et al. 2000a
Sun et al. 2006b
Cortes et al. 2000a
Sun et al. 2006b
J, = decreasing trend
<-> = no trend
aTrends for Lake Superior (Eagle Harbor) and Lake Erie (Sturgeon Point) are based on the majority of reported
compounds, not total PAH.
The studies of the gas-phase PAH estimated half-lives3 for these compounds. Based on the data
through 1997, the half lives for gas-phase PAH compounds ranged from two to nine years. The
more recent data showed a slower rate of decline. Based on the data through 2000, the half-lives
ranged from four to 18 years, and over the most recent period (1996-2003), half lives were greater
than 15 years. Sun et al. (2006b) note that a slower rate of decline in recent years is reasonable if
atmospheric PAH concentrations are approaching a nonzero steady state.
At the IADN site in Chicago, concentrations of all the PAH compounds measured in precipitation
decreased significantly between 1997 and 2003. Similarly, PAH compounds in the gas- and
particle-phases in the ambient air also decreased over this period; significant trends were found for
total PAH, as well as for most of the individual PAH compounds. Efforts to improve the air quality
in Chicago, such as reductions in pollution from motor vehicles, may explain the decreasing trends
(Sun et al. 2006a, Sun et al. 2006b).
The deposition information measured by IADN can be supplemented by measurements of PAH
compounds in the ambient air in the Ontario Great Lakes Basin by Environment Canada. These
sites include rural areas and three classes of urban areas: residential, commercial, and industrial.
For the period from 1996 to 2002, total PAH concentrations in air decreased at urban commercial
sites near Lake Ontario in Toronto and Hamilton, and at an urban residential site in Windsor near
Lake Erie. The authors did not hypothesize as to why these trends exist. At rural sites, there were
no significant trends (Environment Canada 2004).
2.7.2 Biota and Sediments
The National Oceanic and Atmospheric Administration (NOAA) National Status and Trends
(NS&T) Mussel Watch Program has monitored concentrations of trace chemicals in mussels and
The half-life is the number of years for the concentration to decrease by a factor of two, and therefore is an indication
of the rate of decline.
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oysters in the coastal U.S. since 1986. The sites were selected to be representative of large areas,
rather than smaller-scale areas that would be influenced directly by particular local sources of
contaminants. Since mollusks concentrate chemicals from their surrounding waters in their tissues,
they provide an integrated measurement of contamination over time. For PAH compounds, the
Mussel Watch Program groups low-molecular-weight (LMW) PAH (two- and three-ring
compounds) separately from high-molecular-weight (HMW) PAH (four- and five-ring
compounds), because the LMW compounds are relatively more concentrated in oil than in
combustion products (O'Connor 2002).
Data from the Mussel Watch Program
from 1986-1996 were discussed in the
Third Report to Congress, and showed
no trends for PAH. By contrast, a new
national-scale analysis of Mussel Watch
Program data showed that the median
concentration in mollusks decreased
between 1986 and 2002 for both total
LMW and total HMW PAH (U.S. EPA
2004).
UNAVAILABILITY OF PAH IN BENTHIC ORGANISMS
What is bioavailability? Bioavailability is a measure
of the extent and rate that a substance is absorbed into
an organism and how much of it becomes available
within various physiological systems. Bioavailability
is an important component that should be taken into
account when chemical exposures are assessed.
Are PAH compounds readily bioavailable to
benthic organisms? The total concentration of PAH
in sediment is not the only factor involved in how
much of the PAH can enter a benthic organism. In
sediment, several factors influence bioavailability. For
example, the organic carbon content is important
because carbon soot content reduces the
bioavailability, amount, and quality of organic
material present in sediment (Burgess et al. 2003).
Rust et al. (2004) provides some examples of particle-
derived PAH and their level of bioavailability to
benthic organisms; low-bioavailable PAH compounds
include those in coal dust, those with medium
bioavailability are associated with diesel soot and tire
rubber powder, and PAH with high bioavailability
include those associated with fuel oil, creosote, and
crude oil.
Are all benthic organisms equally susceptible? PAH
bioavailability depends not only on environmental
conditions and the type of PAH but also on organism
properties. In organisms, some of the properties
influencing tissue PAH concentrations include the
lipid concentration of an organism (PAH are attracted
to fat), their lifestyle and feeding habits, and gut
chemistry. For example, deposit feeders have greater
ingestion rates than suspension feeders and therefore
tend to accumulate more PAH. And the conditions in
the gut of some benthic organisms make it more likely
that PAH compounds will desorb from the sediments,
increasing bioavailability (Burgess et al. 2003). All of
these factors should be considered when determining
potential effects.
At 206 individual Mussel Watch sites,
trends in total PAH in mollusk tissue
vary. Between 1986 and 1999, 162
sites showed no trends, 26 sites
showed decreasing trends, and 18 sites
showed increasing trends. This
analysis also examined specifically the
trends at National Estuarine Research
Reserves (NERR) designated by
NOAA. Three of the NERR had a
Mussel Watch site showing an
increasing trend for total PAH: North
Inlet - Winyah Bay, SC; Rookery
Bay, FL; and Tijuana River, CA. One
NERR site (Wells, ME) had a Mussel
Watch site showing a decreasing
trend. Some of the increasing trends
may be explained by changes in the
analytical methods for PAH over this
period. Early in the program, the
laboratory analytical method was less
sensitive, so values now recorded as
low PAH concentrations were
originally recorded as zero (NOAA
2002). Higher values of total HMW
PAH were correlated with sites in
close proximity to urban areas,
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indicating that levels are likely due to human activity. Levels of PAH in urban areas are in a
range that may have detrimental effects to the mollusks by causing alterations in lysosomes of
digestive cells (O'Connor 2002).
Long-term trends of PAH concentrations in lake sediments show recent increases related to urban
pollution. While the 38 lakes studied are not Great Waters, they do indicate possible effects of
urbanization on a watershed. The lakes represent a diverse group of geographic regions and
ecoregions, and were categorized by land use: densely urban, light urban, and reference (less than
1.5 percent urban land use). Between 1970 and 2001, concentrations of total PAH in sediment
increased at 42 percent, decreased at five percent, and showed no trend at 53 percent of all the
lakes. None of the reference lakes showed a trend in total PAH concentrations in this period. To
evaluate the potential impact to the aquatic biota, the researchers compared the mean
concentrations in the sediment in the decades from 1965 to 1975 and the 1990s to a consensus-
derived probable effect concentration (PEC). For PAH, the frequency of exceedances of the PEC
approximately doubled in the 1990s compared to the decade from 1965 to 1975. The highest
frequency of exceedances occurred in densely urban lakes (Van Metre and Mahler 2005).
An analysis of trends for individual PAH compounds in these 38 lakes found that more of the lakes
had increasing trends of compounds with higher molecular weight than those with lower molecular
weight. As noted above, the higher molecular weight compounds are more typical of combustion
by-products (Van Metre and Mahler 2005). In an earlier analysis for 10 urban lakes (a subset of the
38), the researchers found that increases in PAH concentration in the sediment cores outpaced the
increase in urbanization since the mid-1970s at nine of the sites. They also found that the increases
in PAH concentration followed closely with increases in automobile use, even in urban areas where
there was a relatively minor increase in the degree of urbanization over the same time period. The
authors noted that there are several sources of vehicle-related PAH in addition to exhaust, including
asphalt wear, tire wear, and leaks and spills of engine oil (Van Metre et al. 2000). Other possible
sources of the PAH are being considered as well, including parking lot sealants, many of which
contain coal tar (Van Metre and Mahler 2005).
2.2 Seasonal Trends
Several studies found seasonal differences in PAH concentrations in air and deposition. Higher
ambient air concentrations or dry deposition during late fall or winter have been observed in coastal
New Jersey (Gigliotti et al. 2000), San Francisco Bay (Tsai et al. 2002), the Great Lakes (EC and
U.S. EPA 2004, Sun et al. 2006b) and the New England coast (Golomb et al. 2001). Similar trends
were found in wet deposition in the Great Lakes (Sun et al. 2006a) and New England (Golomb et
al. 2001). The researchers believe these observations are likely due to fuel combustion for domestic
heating, based on which PAH compounds are most prevalent. In addition, semi-volatile PAH
compounds have a tendency to be in the paniculate phase in colder temperatures.
In New Jersey, Gigliotti et al. (2000) found that during the winter months, the contribution to total
PAH by methylated-phenanthrenes was greater than the contributions of phenanthrenes. During the
summer months, the opposite was true, indicating that dominant sources differ between the two
seasons. These results are based on the first year of sampling (October 1997 through October 1998)
at the New Jersey Atmospheric Deposition Network (NJDAN) suburban site near New Brunswick
and a coastal site in Sandy Hook. Based on an analysis of all the NJDAN sites across the state over
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the approximately four years of sampling, there were no clear seasonal trends in gas-phase
concentrations of PAH. However, increased particle-phase concentrations in winter were found to
be driven by higher emissions from fossil fuel combustion at most of the NJDAN sites (Reinfelder
et al. 2004).
In studies of the ambient air near Galveston Bay, Texas, higher concentrations were found in the
winter and summer compared to the spring and fall, although these were not strong seasonal trends.
Furthermore, no seasonal trends were found in a similar study at Corpus Christi Bay in Texas. The
researchers speculated that the lack of seasonal trends in coastal Texas may be due to the temperate
climate, and smaller seasonal variations in emissions sources than in more northern areas where
seasonal trends are apparent (Park et al. 2001, Park et al. 2002).
Another study examined PAH concentrations in near-shore surface water and in zooplankton in
southern Lake Michigan, near the greater Chicago area. The study was conducted in 1994 and
1995. Concentrations of PAH in surface water measured during the months of January, May, and
July did not vary significantly according to season or wind direction. Based on these data, the study
authors concluded that PAH levels in surface water remained relatively constant. The researchers
also found that lipid-normalized PAH concentrations in zooplankton did not vary with season;
concentrations in January and July were nearly identical. These findings suggest relatively constant
deposition of PAH from urban sources throughout the year (Offenberg and Baker 2000).
3.0 Spatial Trends and Deposition Studies in Various Geographic Areas
A second major area of newly published PAH research addresses ambient air and deposition
studies and analyses in several geographic areas, including the Great Lakes and multiple coastal
locations. In the Third Report to Congress, the spatial trends in PAH concentrations in air and
deposition between urban and rural locations were discussed at length. The newly published
research details the urban influence even further. In general, studies show that PAH are largely
urban pollutants that can travel tens of kilometers (km) through the atmosphere.
One study examined monitoring studies throughout the world, and statistically compared PAH air
concentrations to the human population density within 25 km of the PAH measurements. As
expected, the authors found a strong positive correlation between PAH concentrations and
population density. In addition, spatial differences were seen. Sites located within 25 km of a coast
had lower PAH concentrations than predicted by the regression analysis, due to dilution from
cleaner ocean air, whereas sites near industrial areas had higher PAH concentrations than predicted
(Hafner et al. 2005). The studies below are specific to Great Waters.
3.1 Great Lakes
3.1.1 IADNMaster Stations
In a study of IADN data, dry deposition levels of PAH increased from west to east based on
spatially comparable data for Lakes Superior, Michigan, and Erie (EC and U.S. EPA 2000). This
trend also held true for Lakes Huron and Ontario. Wet deposition fluxes also tended to increase
from west to east when looking at spatially comparable data for the Great Lakes Basin. It is not
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clear whether this spatial trend is due to increasing urbanization in the east or to other aspects of the
monitoring site locations (EC and U.S. EPA 2002a).
Multiple analyses have been performed to examine how well the master stations of IADN on each
of the Great Lakes represent background concentrations and to determine what source regions may
be influencing them. Cortes et al. (2000) considered how well the sites at Eagle Harbor, Sleeping
Bear Dunes, and Sturgeon Point represent background concentrations. The authors concluded that
for Eagle Harbor and Sleeping Bear Dunes, the measured PAH gas-phase concentrations represent
regional background. However, at the Sturgeon Point site near Lake Erie, PAH gas-phase
concentrations decreased when wind blew cleaner air from over Lake Erie. Conversely,
concentrations increased when winds blew from the Buffalo, New York area, which is about 20 km
to the northeast. Buehler and Kites (2002) had similar findings for particle-phase PAH
concentrations, which also were elevated at Sturgeon Point when winds were blowing from
Buffalo. Therefore, both studies concluded that Sturgeon Point does not represent PAH
concentrations for the entire Lake Erie region, as PAH concentrations are strongly influenced by
northeasterly winds from the Buffalo region. Another study compared PAH concentrations in air at
Eagle Harbor and Brule River (a rural site on Lake Superior). Although concentration ranges were
within global background concentrations at both sites, PAH concentrations were higher at Brule
River, indicating that pollution from Duluth may be influencing this site (Buehler et al. 2001).
Further analysis of the IADN data was done by Hafner and Kites (2003) using the Potential Source
Contribution Function (PSCF) model, a probabilistic back-trajectory modeling technique. The
researchers found similar urban influences as found in the studies described above for the influence
of Buffalo on Sturgeon Point and Duluth on Brule River. Across the four PAH compounds studied,
the authors found that the source regions became less distinct as the molecular weight of the
compound increased. They hypothesized that all four PAH compounds originated from the same
source regions, and then the higher molecular weight PAH degraded over distance, due to greater
gas-phase atmospheric reactivity with increased PAH molecular weight.
Another analysis of IADN data from sites in the U.S. compared a variety of methods for including
direction into classic regression equations used to model the atmospheric concentration of a semi-
volatile organic pollutant, like PAH, at a given sampling site. The typical regression model
includes a factor for air temperature at the site, and a factor representing the change in emission
rate as a function of time. This analysis examined three ways to incorporate a factor to represent
direction from which the pollutant came: local wind direction; average backward trajectory of air
coming to the site; and a nonparametric air trajectory based on hypothesized source regions
determined by the PSCF model. For PAH, the source direction factors in the regression analyses
were very important in helping to explain the variability of the atmospheric concentrations at all of
these IADN sites. For example, the local wind direction explained much of the variability at each
of these sites, ranging from about 10 percent of the variability at Eagle Harbor and Chicago to
about 46 percent at Brule River on Lake Superior. The analysis also complemented the findings of
Cortes et al. (2000) that PAH sources are located to the east of the Sturgeon Point site on Lake
Erie, probably in the greater Buffalo, NY area (Hafner and Kites 2005).
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3.1.2 Urban Areas near the Great Lakes
Another group of studies specifically examined gradients of concentrations in and around urban
areas in the Great Lakes region. These studies consistently found that PAH concentrations were
higher around urban areas than in the suburban and rural areas.
Chicago has significantly higher concentrations of PAH compounds in the atmosphere and
deposition than at the IADN master stations. The overall mean concentration of total PAH in
Chicago ambient air between 1996 and 2003 was 70 nanograms per cubic meter (ng/m3) and
12 ng/m3 for the gas and particle phases, respectively. This is over 10 times higher than those
measured at the other IADN sites (Sun et al. 2006b). Over the same period, total PAH in
precipitation in Chicago was 2,300 nanograms per liter (ng/L), compared to a range of 26 to
90 ng/L over the other IADN sites (Sun et al. 2006a).
Figure 2. Net Downward Flux of
Benzo(a)pyrene at IADN Stations on Lake
Michigan in 1999-2000 (EC and U.S. EPA 2004)
Chicago
Sleeping Bear
Dunes
The net deposition downward flux of PAH
to Lake Michigan is generally about 20-75
times higher at Chicago than at Sleeping
Bear Dunes (Figure 2). This is based on
data from IADN stations at both
locations for 1999 and 2000 (EC and
U.S. EPA 2004).
A study of winter snow packs in
Minnesota and around Lake Superior
discovered significantly higher
concentrations of PAH at sites nearer to
urban areas (Franz and Eisenreich 2000).
The Cedar Creek Natural History Area
and the Gray Freshwater Biological
Institute are both sampling locations
within approximately 50 km of the urban Minneapolis/St. Paul region. The study authors found
that, between 1989 and 1992, these urban sampling locations had higher PAH concentrations than
the more rural sampling locations at the Lake Itasca State Forest, the Marcell State Forest, and at
the IADN Eagle Harbor site.
Ambient air monitoring in the Ontario Great Lakes Basin also found that urban sites had much
higher concentrations than rural sites, indicating significant local releases. Over the years 1999 to
2003, the median concentrations of benzo-a-pyrene at most urban sites were generally an order of
magnitude higher than at rural sites. The median concentrations of total PAH over this time period
ranged from 0.59 ng/m3 at the rural site of Burnt Island on Lake Huron to 28.6 ng/m3 at an urban
location in Toronto (Environment Canada 2004).
Several researchers demonstrated how passive air samplers could be used to examine the urban-to-
rural changes in PAH concentration, as well as the vertical distribution of PAH in the urban
atmosphere. Motelay-Massei et al. (2005) deployed passive air samplers for three 4-month
integration periods from June 2000 to July 2001 along a transect from urban sites in Toronto to a
rural site to the north, in Egbert. These samplers were polyurethane foam disks in a stainless steel
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domed chamber. Urban concentrations were roughly five times rural concentrations.
Concentrations were highest in summer, which the researchers attributed to increases in the
evaporative emission from petroleum products such as asphalt. As expected, the relative
proportions of the various PAH compounds were different at the urban and rural sites. The
compounds with lower molecular weight tended to travel farther, whereas those with higher
molecular weight are associated with particles that tended to be deposited closer to the source. The
significant finding was that this effect occurred over a relatively short distance (about 75 km).
The vertical distribution of PAH in the Toronto urban atmosphere was studied by Farrar et al.
(2005) by deploying passive air samplers at various heights on a tower. They found that PAH
concentrations declined sharply with height, indicating that ground-level emissions in urban areas
are sources of these compounds. The study also demonstrated how a new design of passive air
samplers could be used. These samplers consist of a thin film of polymer coating on a glass
cylinder and are designed to equilibrate rapidly under ambient conditions.
3.2 New England Region
In New England, results from deposition monitoring of PAH to coastal waters from March 1998
through May 2000 (Golomb et al. 2001) indicated that the sampling location closer to the Boston
metropolitan area and Logan International Airport (Nahant, Massachusetts) had a higher dry
deposition rate of PAH than the more rural location (Wolf Neck, Maine). The urban sampling
location averaged 95 nanograms per square meter per hour (ng/m2 /hr), while the rural site averaged
9.3 ng/m2 /hr. Conversely, the rural location experienced greater wet deposition of PAH, because
the air masses that brought precipitation to this site carried more PAH from regional sources.
3.3 Mid-Atlantic Region
In Baltimore, Maryland, higher concentrations of PAH were found in films on the exterior window
surfaces located in downtown areas than on those located in suburban areas. PAH samples were
collected from one suburban and three
urban sites in the summer of 1998 (Liu et Figure 3. Total PAH Concentrations
al. 2003). Figure 3 shows the relative Accumulated on Baltimore Windows
concentrations found in the suburban, as (Liu et al. 2003)
well as the urban areas. PAH
concentrations were much higher in the
urban areas, suggesting greater deposition
of PAH in the urban areas, apparently from
vehicle emissions. This is significant
because the PAH that accumulate on
window films are likely to be washed off
into nearby surface waters during
precipitation events.
Also in the Baltimore region, Dachs et al.
(2002) determined that atmospheric gas-
and particulate-phase PAH concentrations
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=; 17Q
78
'
_ 9,453 „„
1,593
Suburban Urban 1 Urban 2 Urban 3
Location
10
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were approximately two- to three-fold higher in the Baltimore urban area than over the Chesapeake
Bay. Additionally, the study authors found that total suspended particulate concentrations in the
Baltimore area (23 to 95 micrograms per cubic meter [|j,g/m3]) were similar to concentrations
observed over the Chesapeake Bay (40 to 84 ng/rn3) when the wind blew from Baltimore.
Concentrations were lower over the Chesapeake Bay (4.5 to 40 ng/m3) when the wind blew from
other areas. This study, conducted in July 1997, demonstrates the influence of urban areas as a
source of pollution to adjacent waterbodies.
In New Jersey, the concentrations of total PAH in ambient air and precipitation vary across the
state. In the first year of sampling (October 1997 to October 1998) at NJADN, researchers found
that the PAH concentrations in the atmosphere were about two times higher at the suburban New
Brunswick site than at the coastal Sandy Hook site, which is consistent with the fact that New
Brunswick is in closer proximity to urban and industrial areas. The Sandy Hook site results were
two to 10 times higher than those at the remote Eagle Harbor on Lake Superior, indicating that
Sandy Hook should not be classified as a remote site (Gigliotti et al. 2000). Over the full NJDAN
study period (about 1997 to 2001), PAH concentrations in the atmosphere and precipitation at the
most urban/industrial sites (Jersey City and Camden) were four to six times greater than at the
NJADN sites representing regional background. However, there was little spatial variation in the
PAH profiles (i.e., the relative amounts of individual compounds to the total PAH), indicating that
the mix of sources is similar throughout the state. Annual average deposition fluxes ranged from
540 to 7,300 |j,g/m2/yr. The most prevalent component of the deposition flux was gas absorption
(55 to 92 percent), followed by dry particle deposition (four to 31 percent), and wet deposition
(three to 16 percent) (Reinfelder et al. 2004).
3.4 Southeast and Gulf Region
A study conducted in Miami, Florida, between June 1994 and March 1995 found that air mass
movement (i.e., wind direction and frequency) is the dominant factor in determining PAH levels in
dry deposition and total suspended particulates (Lang et al. 2002). Winds from the north-northwest
and east-northeast come from inland directions and carry more PAH into the city. PAH are most
likely being carried from the downtown area by these winds, and are transporting PAH from Miami
International airport, automobile exhaust, waste incineration, and natural gas usage areas. These
winds increase the PAH concentration in the air over the most densely populated areas of Miami.
Conversely, winds from the east and south are coming from the Atlantic Ocean and carry cleaner
air. The study authors showed that PAH concentrations were lower when oceanic air was coming
from the east and south, as it flushed anthropogenic aerosols out of the metropolitan area. Note that
this analysis was based on monthly-averaged data, and therefore should be viewed as general
trends, not as quantitative results.
Deposition of PAH compounds directly to Tampa Bay was studied by Poor (2002) and Poor et al.
(2004). In the earlier study, measurements were made from March to October 2001. The average
concentration for the total PAH in the ambient air was 14 ng/m3. Dry deposition of gas and
r\
particles was estimated to be about two |J,g/m /day, and wet deposition of gas and particles was
estimated to be about 0.1 |j,g/m2/day, assuming no flux of PAH from the water to the air. A
comparison of these rates with others reported in the literature indicated that the rates in Tampa
Bay are in the range of deposition rates at both rural and urban sites in the eastern coastal U.S.
11
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(Poor 2002). The latter study used a different sampling method, which improved capture of gas-
and particle-phase PAH compounds with lower molecular weights. Based on sampling between
May and August 2002, the concentrations of total PAH were between 80 and 190 ng/m3, and dry
r\
deposition flux of gas and particles was estimated to be 11.5 ng/m /day, assuming no flux of PAH
from the water to the air. Differences in sampling methodologies are discussed further in Poor et al.
(2004).
Deposition of PAH to Galveston and Corpus Christi Bays in Texas was studied by Park et al.
(2001, 2002). In Galveston Bay, PAH in ambient air and precipitation was measured between
February 1995 and August 1996. Total PAH concentrations ranged from 4 to 161 ng/m3 in air
samples, and from 50 to 312 ng/L in rain samples. The annual wet deposition flux was estimated to
9 9
be 130 ng/m /yr, and dry particle deposition flux to be 99 |J,g/m /yr. The net gas exchange from the
air to the surface water was estimated to be 1,21 I|j,g/m2/yr, although the authors noted that this
estimate should be considered preliminary (Park et al. 2001).
In Corpus Christi Bay, PAH in ambient air and precipitation were measured between August 1998
and September 1999. Concurrently, water samples were taken to calculate air-water gas exchange.
Total PAH concentrations ranged from about two to 57 ng/m3 in air samples. The annual wet
9 9
deposition flux was estimated to be 182 ng/m /yr, the dry particle deposition flux to be 68 ng/m /yr,
r\
and the net gas exchange was -38.4 ng/m /Yr (the negative number indicating net exchange from the
water to the air) (Park et al. 2002).
3.5 West Coast Region
For the northern San Francisco Estuary, PAH concentrations in the ambient air were studied, and
fluxes between air and water were estimated by Tsai et al. (2002). Measurements were made at a
single sampling site from June to November 2000. Average monthly concentrations ranged from
eight to 37 ng/m3, and were predominantly in the vapor phase. The researchers noted that these
concentrations were 10 times lower than in Chicago, and comparable to those found around
urbanized areas in Baltimore and New Jersey. Dry deposition of particles ranged from 0.04 to 0.96
ng/m2/day. Gaseous PAH fluxes ranged from about 0.1 |j,g/m2/day efflux from the estuary to the air
r\
in August to about one ng/m /day influx to the estuary from the air in November. Wet deposition
was not measured.
4.0 Emissions and Source Profiles
The third major area of new information on PAH addresses source profiles in various regions as
well as trends in PAH emissions from these sources. Many of the recent studies on sources of PAH
are consistent with, and in some cases expand upon, the findings in the Third Report to Congress
for the Great Lakes region. Furthermore, new information regarding sources of PAH nationally, as
well as in Galveston Bay and Corpus Christi Bay, Texas, and the city of Miami has been reported.
12
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4.1 National Emissions Inventory
U.S. EPA's 2002 national emissions inventory (NEI) lists aggregated emissions for 15 individual
PAH compounds (15-PAH).4 Table 2 shows that the dominant 15-PAH emission sources are
residential wood heating and open burning due to forest and wildfires. Comparisons with the
National Toxics Inventory for 1990-1993, shown in the Third Report to Congress, reflect changes
due to regulations, changes in industry, and changes in knowledge and information on the part of
the organizations submitting data that are included in these national emission inventories. In the
Third Report to Congress, consumer products usage was listed as the major source for 16-PAH;
however, this category is almost completely attributed to naphthalene, which is no longer included
in the aggregated list of 15 PAH for the NEI.
4 In the Third Report to Congress, naphthalene was included in the list of aggregated compounds (16-PAH); however,
EPA is not using 16-PAH in the 1999 NEI for hazardous air pollutants (HAP), because naphthalene is one of the 188
HAP compounds. The chemicals that comprise the 15-PAH group are the ones that can be measured using EPA test
method 610 and consist of: benzo(a)anthracene, benzo(b)fluoranthene, benzo(k)fluoranthene, benzo(a)pyrene,
chrysene, dibenzo(a,h)anthracene, indeno(l,2,3-c,d)pyrene, fluorene, acenaphthylene, acenaphthene, anthracene,
benzo(g,h,i)perylene, fluoranthene, phenanthrene, and pyrene.
13
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Table 2. National Anthropogenic 15-PAH Air Emissions
(Based on U.S. EPA's 2002 National Emissions Inventory)
Source Category
Residential Boilers - Wood/Wood Residue
Combustion
Open Burning - Forest and Wildfires
Mobile Sources - Onroad
Open Burning - Residential, Household Waste
Open Burning - Prescribed Burning
Coke Ovens - Pushing, Quenching, & Battery
Stacks3
Mobile Sources - Nonroad
Commercial Cooking - Charbroiling
Catastrophic/Accidental Releases
Mobile Sources - Aircraft Locomotive Marine
Industrial/Commercial/ Institutional Boilers &
Process Heaters3
Others (<1 percent each)b
Total U.S. Anthropogenic 15-PAH Air Emissions
(290 Categories)
Anthropogenic
Air Emissions
(tons/year)
5,899
2,300
439
426
359
319
253
221
146
133
111
793
11,400
Percent Contribution to
Total U.S.
Anthropogenic Air
Emissions
52
20
4
4
3
3
2
2
1
1
1
7
100
aThese source categories are associated with maximum achievable control technology (MACT) rules.
bA list of the source categories that contribute less than one percent to total U.S. air emissions is provided in
Appendix A.
Source: U.S. EPA 2007
Although it is not within the scope of this report to describe in detail the efforts to reduce current
emissions of PAH, it is important to note that many are ongoing. U.S. EPA, other federal
agencies, and state/local/tribal governments are involved in reducing emissions from burning
through smoke management programs, regulations, and education/outreach activities. For
residential wood combustion, U.S. EPA, state/local/tribal governments, and non-governmental
partners are working to reduce emissions through voluntary programs, ordinances and
education/outreach activities. U.S. EPA also has finalized several rules that will reduce air
emissions of POM (of which PAH are a subset) from stationary sources; these rules are based on
maximum achievable control technology (MACT). The Third Report to Congress noted the
MACT standard for the primary aluminum production industry. Several other industries for
which recent MACT standards will reduce POM emissions include asphalt processing and
roofing, iron and steel foundries, and refractory products. U.S. EPA has also issued regulations
to reduce the residual risk due to coke oven emissions remaining after implementation of the
14
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MACT rule for coke ovens; constituents of coke oven emissions include POM compounds. In
addition, in 2007, U.S. EPA published final rules to control hazardous air pollutants from mobile
sources (72 FR 8427, February 27, 2007). The vehicle controls included in the rule may help to
reduce deposition of POM.
Figure 4. Source Apportionment of Atmospheric
PAH in the Coastal Atmosphere of Chicago and
Lake Michigan in 1994-1995 (Simcik et al. 1999)
Vehicle
Emissions
(9 ± 4%
Coke
Ovens (14
±3%)
Natural
Gas
Combus-
tion (26 ±
2%)
Coal
Combus-
tion (48 ±
5%)
4.2 Great Lakes Region
Numerous new studies examined the
sources of PAH to the Great Lakes
region. Simcik et al. (1999) applied
multivariate statistical techniques to
PAH concentrations to investigate
source apportionment and source/sink
relationships in the coastal atmosphere
of Chicago and Lake Michigan over
1994 -1995. Figure 4 depicts the
percentages of the various sources of
PAH based on this analysis.
These sources are consistent with the
sources for the region that were
identified in the Third Report to
Congress. Simcik et al. (1999) also
determined that atmospheric deposition
is the major source of PAH to the
sediments and water column particulate phase of Lake Michigan. Offenberg and Baker (2002)
determined that particle scavenging (as opposed to gas scavenging) during storms is the
dominant method for removal of PAH from the atmosphere sampled around southern Lake
Michigan along the urban to over-water transect. A study of soot (e.g., partially combusted
and/or pyrolized carbon) that had been deposited in the Great Lakes found a strong correlation
between soot carbon and PAH sediment accumulation at a site in southern Lake Michigan,
particularly for high molecular weight PAH. This finding provides additional evidence to the
theory that soot is a major vector for deposition of PAH compounds. Furthermore, soot
accumulation throughout the Great Lakes was found to be higher closer to large industrial areas,
as might be expected due to the proximity of combustion sources (Buckley et al. 2004).
In another study, the chemical mass balance model CMB8.2 was used to determine the major
sources of PAH to Lake Calumet and surrounding wetlands in southeastern Chicago (Li et al.
2003). The model, developed by U.S. EPA, has been used primarily to estimate source
contributions to ambient air concentrations. In this study, the researchers applied the model to
PAH found in aquatic sediment cores. They examined six source categories (coke oven,
residential coal burning, coal combustion in power generation, gasoline engine exhaust, diesel
engine exhaust, and traffic tunnel air) by establishing fingerprints based on the relative
contribution of various PAH compounds for each category. The major sources of PAH to Lake
Calumet were determined to be coke ovens and vehicular traffic.
5 See http://www.epa.gov/ttn/atw/ for more information on the MACT and residual risk standards.
15
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Su et al. (2000) examined sediment cores from the lower Fox River, near Green Bay,
Wisconsin. The researchers used a chemical mass balance approach, along with an analysis of
the carbon particles in the sediments, to evaluate source trends over time. They determined that
the major PAH sources for this area were coke ovens, highway dust, coal gasification, and wood
burning. Since 1896, the major source of PAH in the area has been coke ovens, contributing
between 40 and 90 percent of the total PAH concentration. Highway dust contributes between
10 and 75 percent of the total PAH concentration. The contribution from coke ovens generally
decreased between 1930 and 1990, while the contribution from highway dust has increased
since 1930. The percentage of PAH from wood burning has been generally smaller than coke
ovens and highway dust; it was estimated to be between three and 10 percent in 1995.
Wood burning is found to be more prevalent in northern and more rural areas around the Great
Lakes. The contribution of retene, an indicator of wood combustion, to total PAH concentrations
in ambient air was found to be higher in rural sites in Canada (Environment Canada 2004).
Similarly, the ratios of retene concentrations to total PAH concentrations in precipitation and
ambient air measured at rural IADN sites were significantly higher at the rural sites than in
Chicago. The highest ratios in precipitation were found at the sites near Lake Superior (Brule
River and Eagle Harbor) (Sun et al. 2006a, Sun et al. 2006b)
4.3 New England Region
The chemical mass balance model CMB8.0 was applied by Golomb et al. (2001) to examine
source apportionment in two locations in New England: Nahant, Massachusetts, which is near
the Boston metropolitan area and Logan International Airport, and Wolf Neck, Maine, which is
more rural. These sites were chosen to represent deposition to Massachusetts Bay and Casco
Bay, respectively. The researchers applied the model to samples from dry deposition monitoring
of PAH in these locations from March 1998 through May 2000. Four source categories expected
to be significant contributors in this region were chosen for the modeling analysis. Figure 5
depicts the source profiles of the two sites. It is interesting to note the differences in the source
profiles at these locations, as compared to the Great Lakes site depicted in Figure 4. In the Great
Lakes area, coal and natural gas combustion are the two largest sources of PAH, whereas in the
New England area, jet exhaust and gasoline fueled vehicles are the two largest sources.
16
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Figure 5. Source Contributions to PAH Dry Deposition at the
Nahant, MA and Wolf Neck, ME Sampling Locations (Golomb et al. 2001)
Wood
Combus-
tion (13%)
Diesel
Fueled
Vehicles
(17%)
Gasoline
Fueled
Vehicles
(32%)
Nahant, MA
Others
(3%)
Jet Exhaust
(35%)
Wood
Combus-
tion (16%)
Diesel
Fueled
Vehicles
(18%)
Wolf Neck, ME
Others
(8%
Jet Exhaust
(30%)
Gasoline
Fueled
Vehicles
(28%)
4.4 Baltimore/Chesapeake Bay Region
Larsen and Baker (2003) applied three statistical techniques for source apportionment to PAH
concentrations in the Baltimore urban atmosphere, over the period from March 1997 through
December 1998. Use of three methods allows for comparison and mitigates the weaknesses of
each method. In general, the results from the methods agreed well with one another. Coal
combustion contributed 28 to 36 percent of the PAH in ambient air. Vehicles, both gasoline and
diesel, contributed 16 to 26 percent. Oil combustion contributed 15 to 23 percent. Wood
combustion and other unidentified sources accounted for 23 to 35 percent of the total. During the
summer, coal was the dominant source, while during the winter, oil dominated.
Dachs et al. (2002) conducted a study of atmospheric concentrations of PAH in Baltimore and
the adjacent Chesapeake Bay in the summer of 1997 to examine short-term variability. Over the
long term, the Bay is a receptor of PAH deposition due to regional urban and industrial
influences (such as Baltimore). However, depending on certain meteorological conditions, such
as wind speed and temperature, the Chesapeake Bay can act as a short-term source of PAH to the
atmosphere when there is a relatively clean air mass above it.
Another study (Arzayus et al. 2001) indicated that the dominant mode of entry of PAH from the
atmosphere to the southern part of the Chesapeake Bay is indirect atmospheric deposition (i.e.,
deposition to the surrounding watershed and subsequent runoff). Surface sediment samples were
collected in various seasons from five sites in the southern Chesapeake Bay. For all sampling
locations and times, increases in PAH concentrations were found to be similar, indicating that a
single source or mode of entry controls the distribution of PAH to the Chesapeake Bay
sediments. Due to the fact that most of the sampling locations were removed from point sources,
the study authors determined that the atmosphere was the dominant source of PAH to the
sediments in that region of the bay. Furthermore, the study authors concluded that PAH in the
Chesapeake Bay sediments are from airborne soot particles, as the atmospheric soot signal is
retained in the sediments.
17
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4.5 Galveston/Corpus Christi Bay Region
In Galveston Bay, Texas, sediment and American oyster samples were analyzed to determine
PAH sources and historical trends (Qian et al. 2001). Samples were collected at six sites in
Galveston Bay between November and January, in selected years from 1986 to 1998. The
primary source of PAH to the bay was determined to be from combustion products, followed by
spilled or released petroleum products. There were no temporal trends, so these PAH sources
were likely unchanged over the 13-year study. During some years, there was an increase in PAH
that the study authors attributed to documented or suspected oil spills. Additionally, Qian et al.
(2001) indicated that the bioavailability of the PAH sources determines the concentrations and
composition of PAH in oysters. PAH concentrations in Galveston Bay oysters were high
compared to national levels, although the authors did not explore the severity of the PAH
contamination in this region.
In a study conducted at Galveston Bay between February 2005 and August 1996, PAH sampled
in the air were found to be primarily from combustion and petroleum vaporization (Park et al.
2001). These sources are similar to those identified in Corpus Christi Bay, which acts as a sink
for PAH. In a similar study conducted between August 1998 and September 1999 (Park et al.
2002), the majority of PAH found on parti culates in air and rain were determined to be from
combustion sources. This study also indicated that direct atmospheric inputs of PAH were not as
large as inputs from land runoff or periodic oil spills. The researchers anticipate that as the
population and industrial activity in the Bay increases, atmospheric input of PAH will also
increase.
4.6 Miami Region
A study conducted in Miami between June 1994 and March 1995 determined that the main
source of atmospheric PAH in that area was determined to be automobile exhaust, due to the
elevated levels of benzo(ghi)perylene and coronene found in total suspended parti culates
analyzed (Lang et al. 2002). Other sources that contributed to the elevated PAH levels for dry
deposition included waste incineration, power plants, and biomass accumulation. The authors
also concluded that the air in the Miami area should be considered moderately polluted.
5.0 Summary and Some Future Directions for Research
A large amount of new research has been conducted since the publication of the Third Report to
Congress on temporal and spatial trends in PAH concentrations and deposition in the Great
Lakes region as well as in other Great Waters locations. In addition, several studies focused on
PAH source profiling in new regions of interest (e.g., Miami, Galveston Bay). Most studies
generally agree with or expand upon information that was provided in the Third Great Waters
Report to Congress.
The Great Lakes region is the only Great Waters for which there are long-term data for PAH in
the atmosphere and precipitation. There, trends are mixed; either no trends or decreasing trends
have been found. In Chicago, decreases in concentrations in the atmosphere and deposition have
been observed recently, perhaps due to reductions in sources in the city.
18
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In coastal waters, Mussel Watch provides long-term information about PAH in the environment
via concentrations in bivalves. At most of the over 200 sites, there is no trend in PAH
concentration. However, the median PAH concentration across all sites nationally decreased
between 1986 and 2002.
The greatest concentrations of PAH near the Great Waters are in urban and industrial areas. For
example, in the coastal areas of New Jersey, PAH deposition was four to six times higher than at
the most urban/industrial sites than at the more rural sites, representative of the regional
background levels. Similarly, researchers in the Great Lakes have been determining ways to
incorporate the effects of significant urban centers, like Chicago, into estimates of total loadings
to the Lakes. Studies of lakes in growing urban areas are showing increasing trends in PAH
concentrations in sediments. The urbanization brings increased vehicular traffic, which
contributes to PAH from exhaust, asphalt wear, tire wear, and leaks and spills of oil. The
findings from these areas may be transferable to urban areas near the Great Waters.
Seasonal trends in the PAH compounds in the ambient air and deposition were found in several
areas, particularly those in more northern latitudes. Semi-volatile compounds tend to be more in
a paniculate state in cooler temperatures. In addition, more combustion-derived PAH emissions
due to heating in the colder months add to the seasonality. No seasonal trends were found in
PAH concentrations in surface water or in zooplankton in southern Lake Michigan; researchers'
interpretation of this finding was that the deposition from the Chicago urban area was relatively
constant throughout the year.
Since the Third Report to Congress, deposition studies have been done in several Great Waters
areas not previously studied, including the Gulf coast areas of Tampa Bay, Galveston Bay and
Corpus Christi Bay, and San Francisco Bay on the West coast. Furthermore, in New Jersey,
where there are several Great Waters estuaries, the New Jersey Atmospheric Deposition Network
provides a four-year monitoring study of multiple sites throughout the state.
The Third Report to Congress found that both local and regional sources can play a role in
deposition of PAH to waterbodies. A new study in New England illustrates that finding. Dry
deposition was higher near the urban area of Boston and Logan International Airport than in a
rural area in Maine, likely due to local urban sources. However, wet deposition was higher at the
rural Maine location because the air masses that brought precipitation to the site in Maine carried
more PAH from regional sources than air masses that brought precipitation to the location near
Boston.
On a national basis, emissions of PAH are dominated by residential wood burning and open
burning. Regionally, however, other sources may dominate, depending on particular industrial or
urban activities. Various statistical techniques have been applied to trace the sources in several
geographic areas. Depending on the location, other dominant sources include coal combustion,
coke ovens, jet exhaust, and vehicles.
Several of the articles in the recent literature recommend continued research to improve
knowledge related to PAH trends and sources, and to assess the effects of recent programs to
19
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reduce PAH emissions. Investigators' specific recommendations for future research are as
follows.
• There is a need to better understand the effect of population and industrial activity on
atmospheric PAH (Park et al. 2002).
• Volatilization from surface water is an important removal process of PAH from
Corpus Christi Bay. However, despite technological advances over the past decade,
further reliable estimates of physical-chemical parameters like Henry's Law constant
and mass transfer coefficient, as well as deposition velocity and loadings from other
sources are needed to improve the accuracy of atmospheric loading estimates for
semi-volatile organic contaminants (Park et al. 2002).
• Because particle scavenging dominates washout mechanisms for PAH compounds in
a wide range of precipitation events, more research is needed on the importance of in-
cloud processing to overall scavenging. Direct measurement of in-cloud processing of
these compounds would greatly improve the ability to interpret the scavenging and
atmospheric processing of these compounds. Furthermore, such an investigation
would allow for better explanation of the occurrence of the differing magnitudes of
precipitation scavenging found over the course of more than 100 kilometers
(Offenberg and Baker 2002).
• Future research and monitoring efforts should strive to include compounds that have
been identified as key PAH source markers in models to more accurately identify the
source origins of PAH (Larsen and Baker 2003).
20
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6.0 References
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polycyclic aromatic hydrocarbons (PAHs). Public Health Service, U.S. Department of
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Arzayus, K.M., R.M. Dickhut, and E.A. Canuel. 2001. Fate of atmospheric deposited polycyclic
aromatic hydrocarbons (PAH) in Chesapeake Bay. Environ. Sci. Technol. 35: 2178-2183.
Buckley, D.R, KJ. Rockne, A. Li, and WJ. Mills. 2004. Soot deposition in the Great Lakes:
implications for semi-volatile hydrophobic organic pollutant deposition. Environ. Sci.
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Buehler, S.S., I. Basu, R.A. Kites. 2001. A comparison of PAH, PCB, and pesticide
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Buehler, S.S., and R.A. Kites. 2002. The Great Lakes' Integrated Atmospheric Deposition
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Dachs, I, T.R. Glenn IV, C.L. Gigliotti, P. Brunciak, L.A. Totten, E.D. Nelson, T.P. Franz, and
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toxic substances to the Great Lakes: IADN results through 2000. Environment Canada
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Environmental Protection Agency (EPA 905-R-0 1-007). Available at
^
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EC and U.S. EPA. 2002b. Cooperating to Implement the Great Lakes Water Quality Agreement:
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atmosphere boundary layer. Environ. Sci. Technol. 39(1): 42-48.
Franz, T.P., and SJ. Eisenreich. 2000. Accumulation of polychlorinated biphenyls and
polycyclic aromatic hydrocarbons in the snowpack of Minnesota and Lake Superior. J.
Great Lakes Res. 26(2): 220-234.
Gigliotti, C. L., J. Dachs, E.D. Nelson, P. A. Brunciak, and SJ. Eisenreich. 2000. Polycyclic
aromatic hydrocarbons in the New Jersey coastal atmosphere. Environ. Sci. Technol.
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Golomb, D., E. Barry, G. Fisher, P. Varanusupakul, M. Koleda, and T. Rooney. 2001.
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waters. Atmos. Environ. 35: 6245-6258.
Hafner, W.D., D. Carlson, and R. Kites. 2005. Influence of local human population on
atmospheric polycyclic aromatic hydrocarbon concentrations. Environ. Sci. Technol.
39:7374-7379.
Hafner, W.D., and R. Kites. 2005. Effects of wind and air trajectory directions on atmospheric
concentration of persistent organic pollutants near the Great Lakes. Environ. Sci.
Technol. 39:7817-7825.
Hafner, W.D., and R. Kites. 2003. Potential sources of pesticides, PCBs, and PAH to the
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Appendix A. Detailed Breakdown of Air Emissions Inventory
by Pollutant for Source Categories Emitting
Less than One Percent of Total U.S. Emissions
POLY CYCLIC AROMATIC HYDROCARBONS (MEASURED AS 15-PAH)
Acrylic/Modacrylic Fibers Production3
Aerospace Industries3
Agricultural Chemicals and Pesticides
Manufacturing3
Agricultural Field Burning
Agriculture Production - Orchard Heaters
Amino/Phenolic Resins Production3
Asphalt Paving,Block and Roofing Manufacturing
Asphalt Paving: Cutback Asphalt
Asphalt Paving: Emulsified Asphalt
Asphalt Processing and Asphalt Roofing
Manufacturing3
Auto & Light Duty Truck (Surface Coating)3
Autobody Refinishing Paint Shops3
Boat Manufacturing3
Carbon Black Production3
Chemical Manufacturing
Chemical Preparations3
Chemicals and Allied Products Storage
Clay Ceramics Manufacturing3
Coal Mining, Cleaning, and Material Handling
Coke Ovens: Charging, Top Side, and Door Leaks3
Commercial and Industrial Solid Waste Incineration3
Commercial Cooking: Frying
Commercial Sterilization Facilities3
Cremation
Crude Petroleum Pipelines
Cyclic Crude and Intermediate Production3
Electrical and Electronics Equipment Manufacturing
Electrical and Electronics Equipment: Finishing
Operations3
Engine Test Facilities3
Ethylene Processes3
Fabricated Metal Products Manufacturing
Fabricated Plate Work3
Fabricated Structural Metal Manufacturing3
Ferroalloys Production3
Food and Agriculture
Food Manufacturing
Friction Materials Manufacturing3
Gasoline Distribution (Stage I)3
General Laboratory Activities
General Laboratory Activities: Commercial Physical
and Biological Research
General Laboratory Activities: Noncommercial
Physical and Biological Research
Glass Manufacturing: Flat Glass
Glass Products Manufacturing
Hospital Sterilizers3
Incineration
Industrial Cooling Towers3
Industrial Inorganic Chemical Manufacturing3
Industrial Machinery and Equipment: Finishing
Operations3
Industrial Machinery Manufacturing
Industrial Organic Chemical Manufacturing
Industrial Organic Chemical Manufacturing3
Industrial Processes
Inorganic Pigments Manufacturing3
Instruments Manufacturing: Photographic and
Photocopying Equipment
Instruments Manufacturing: Surgical and Medical
Instruments
Integrated Iron & Steel Manufacturing3
Iron and Steel Forging3
Iron and Steel Foundries3
Iron Foundries
Landfills - Commercial/Institutional
Landfills - Industrial
Large Appliance (Surface Coating)3
Lead Acid Battery Manufacturing3
Leather Tanning & Finishing Operations3
Lime Manufacturing3
Medical Waste Incinerators3
Metal Can (Surface Coating)3
Metal Furniture (Surface Coating3
Mineral Products
Mining
Mining and Quarrying: Construction Sand and
Gravel
Miscellaneous Coating Manufacturing3
Miscellaneous Metal Parts & Products (Surface
Coating)3
Miscellaneous Organic Chemical Manufacturing3
Municipal Landfills3
Municipal Waste Combustors: Large3
Municipal Waste Combustors: Small3
Natural Gas Distribution
Natural Gas Transmission
Nonferrous Foundries, Not Elsewhere Classified3
Off-Site Waste and Recovery Operations3
Oil & Natural Gas Production: Crude Petroleum and
Natural Gas Extraction
Oil & Natural Gas Production: Natural Gas
Extraction
A-l
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Oil & Natural Gas Production3
Open Burning - Managed Burning, Slash (Logging
Debris)
Open Burning - Commercial/Institutional
Open Burning - Firefighting Training
Open Burning - Industrial
Open Burning - Municipal Yard Waste
Open Burning - Yard Waste
Organic Liquids Distribution (Non-Gasoline)3
Other Solid Waste Incineration3
Paper & Other Webs (Surface Coating)3
Petroleum and Coal Products Manufacturing
Petroleum Lubricating Oil and Grease Manufacturing
Petroleum Product Storage Tanks
Petroleum Product Storage Tanks: Airports: Aviation
Gasoline
Petroleum Product Transportation
Petroleum Product Transportation and Marketing:
Bulk Stations and Terminals
Petroleum Refineries
Petroleum Refineries - Catalytic Cracking, Catalytic
Reforming, & Sulfur Plant Units3
Petroleum Refineries - Other Sources Not Distinctly
Listed3
Pharmaceutical Production3
Phosphate Fertilizers Production3
Phosphoric Acid Manufacturing3
Plastic Materials and Resins Manufacturing3
Plastic Parts & Products (Surface Coating)3
Plastics Products: Custom Compounding of
Purchased Resins
Plastics Products: Fiberglassing
Plastics Products: Polystyrene Foam Product
Manufacturing
Plastics Products: Unlaminated Plastics Plate, Sheet,
and Profile Shapes Manufacturing
Plating and Polishing3
Plywood and Composite Wood Products
Plywood and Composite Wood Products3
Polyether Polyols Production3
Polyethylene Terephthalate Production3
Polymers and Resins - NonMACT
Portland Cement Manufacturing3
Prepared Feeds Manufacturing
Prepared Feeds Manufacturing3
Pressed and Blown Glass and Glassware
Manufacturing3
Primary Aluminum Production3
Primary Magnesium Refining3
Primary Metal Production
3These source categories are associated with MACT rules.
Note: NEC indicates "not elsewhere classified."
Primary Metal Products Manufacturing3
Printed Circuit Board Manufacturing
Printing, Coating & Dyeing Of Fabrics3
Printing/Publishing (Surface Coating)3
Publicly Owned Treatment Works (POTWs)3
Pulp and Paper Production - NonMACT Facilities
Pulp and Paper Production3
Refractory Products Manufacturing3
Reinforced Plastic Composites Production3
Residential Heating, NEC
Rocket Engine Test Firing3
Rubber Tire Production3
Sawmills
Secondary Aluminum Production3
Secondary Copper Smelting3
Secondary Lead Smelting3
Secondary Nonferrous Metals3
Semiconductor Manufacturing3
Sewage Sludge Incineration3
Shipbuilding & Ship Repair (Surface Coating)3
Site Remediation3
Solvent Extraction for Vegetable Oil Production
Solvent Extraction for Vegetable Oil Production3
Solvent Use
Stainless and Nonstainless Steel Manufacturing:
Electric Arc Furnaces (EAF)3
Stationary Combustion Turbines - Gasified Coal
Stationary Combustion Turbines - Natural Gas3
Stationary Combustion Turbines - Oil3
Stationary Reciprocating Internal Combustion
Engines - Geothermal
Stationary Reciprocating Internal Combustion
Engines - Natural Gas3
Stationary Reciprocating Internal Combustion
Engines - Oil3
Stationary Reciprocating Internal Combustion
Engines3
Synthetic Organic Chemical Manufacturing (HON)'
Synthetic Rubber Manufacturing3
Utility Boilers
Valves and Pipe Fittings Manufacturing3
Waste Disposal, Treatment, and Recovery: TSDF
Waste Disposal: Industrial
Wastewater Treatment: Industrial
Wood Building Products (Surface Coating)3
Wood Furniture (Surface Coating)3
Wood Preserving3
Wool Fiberglass Manufacturing3
A-2
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United States Office of Air Quality Planning and Standards Publication No. EPA-452/R-07-011
Environmental Protection Health and Environmental Impacts Division December 2007
Agency Research Triangle Park, NC
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