Emissions from an International Airport Increase Particle Number
Concentrations 4‑fold at 10 km Downwind
Timothy V. Larson,
and Scott A. Fruin*
Keck School of Medicine, Department of Preventive Medicine, University of Southern California, Los Angeles, California 90089,
Department of Civil and Environmental Engineering, University of Washington, Seattle, Washington 98195, United States
Department of Environmental and Occupational Health Sciences, University of Washington, Seattle, Washington 98195, United
ABSTRACT: We measured the spatial pattern of particle number (PN)
concentrations downwind from the Los Angeles International Airport
(LAX) with an instrumented vehicle that enabled us to cover larger areas
than allowed by traditional stationary measurements. LAX emissions
adversely impacted air quality much farther than reported in previous
airport studies. We measured at least a 2-fold increase in PN
concentrations over unimpacted baseline PN concentrations during
most hours of the day in an area of about 60 km2that extended to 16 km
(10 miles) downwind and a 4- to 5-fold increase to 8−10 km (5−6
miles) downwind. Locations of maximum PN concentrations were
aligned to eastern, downwind jet trajectories during prevailing westerly
winds and to 8 km downwind concentrations exceeded 75 000 particles/
cm3, more than the average freeway PN concentration in Los Angeles.
During infrequent northerly winds, the impact area remained large but shifted to south of the airport. The freeway length that
would cause an impact equivalent to that measured in this study (i.e., PN concentration increases weighted by the area impacted)
was estimated to be 280−790 km. The total freeway length in Los Angeles is 1500 km. These results suggest that airport
emissions are a major source of PN in Los Angeles that are of the same general magnitude as the entire urban freeway network.
They also indicate that the air quality impact areas of major airports may have been seriously underestimated.
Previous studies that directly measured the impact of aviation
activity on air quality have mostly conducted measurements in
close proximity of airports. Few studies have reported
signiﬁcant air quality impacts extending beyond a
Carslaw et al. 2006
analyzed diﬀerences in
pollutant concentrations by wind speed and direction along
with diﬀerences in aircraft and ground traﬃc activity at
Heathrow Airport in London. They found airport contributions
of up to 15% of total oxides of nitrogen (NOx) at a site 1.5 km
downwind of the nearest runway. At Hong Kong International
Airport, Yu et al. 2004
used nonparametric regression analysis
on pollutant concentrations by wind speed and direction. They
calculated that aircraft nearly doubled sulfur dioxide concen-
trations 3 km away and also increased concentrations of carbon
monoxide and respirable suspended particles under similar
wind speeds and directions. Fanning et al. 2007
particle numbers concentrations in the 10−100 nm range and
found signiﬁcant increases above background at 1.9, 2.7, and 3.3
km downwind of the Los Angeles International Airport (LAX)
blast fence. Although measurements were stationary and not
concurrent, they also noted that takeoﬀs produced high
concentrations and downwind gradients within 600 m of the
blast fence. Dodson et al. 2009
found that aircraft activity at a
regional airport in Warwick, RI contributed 24−28% of the
total black carbon (BC) measured at ﬁve sites 0.16−3.7 km
from the airport.
Several other airport and aviation emissions studies focused
on quantifying the air quality impacts from jet takeoﬀs
measured air pollutant concentrations very close to runways. Of
particular relevance to this study, Hsu et al. 2013
activity at LAX with 1 min average PN concentrations. Their
models suggested that aircraft produced a median PN
concentration of nearly 150 000 particles/cm3at the end of
the departure runway. PN concentrations decreased rapidly
with distance to 19 000 particles/cm3at a location 250 m
downwind and to 17 000 particles/cm3at a location 500 m
further downwind. The rapid drop-oﬀin concentration,
however, may have reﬂected an increasing oﬀset from the
centerline of impacts with greater downwind measurement
distance. Similar magnitude PN concentrations and correlations
Received: January 22, 2014
Revised: May 12, 2014
Accepted: May 14, 2014
Published: May 29, 2014
© 2014 American Chemical Society 6628 dx.doi.org/10.1021/es5001566 |Environ. Sci. Technol. 2014, 48, 6628−6635
with departures were reported by Westerdahl et al. 2008
Zhu et al. 2011
at sites located within 100−200 m of the Hsu
et al. 2013
Our study was motivated by mobile monitoring platform
(MMP) based observations of large but gradual increases in PN
concentrations as we approached locations under LAX jet
landing trajectories on multiple transects up to 10 km
downwind of LAX. We hypothesized that emissions from
LAX activities were increasing PN concentrations over much
larger areas and longer downwind distances than previously
observed in studies that focused on near freeway and jet takeoﬀ
impacts to air quality. An extensive monitoring campaign
conﬁrmed that LAX-related emissions increased PN concen-
trations downwind at least 2-fold to 16 km. This large,
previously undiscovered spatial extent of the air quality impacts
downwind of major airports may mean a signiﬁcant fraction of
urban dwellers living near airports likely receive most of their
outdoor PN exposure from airports rather than roadway traﬃc.
■MATERIALS AND METHODS
Monitoring Area. LAX is the sixth busiest airport in the
world and third busiest in the United States. About 95% of
ﬂights take oﬀand land into the prevailing westerly/west-
southwesterly (W/WSW) onshore winds
(i.e., 263 degrees,
the direction of runway alignment
) using two sets of parallel
runways separated by about 1.5 km. In the busiest hours, 40−
60 jets per hour arrive during hours 0700−1900 and depart
during hours 0800−2100. Reduced activity is typical for the
early morning and late evening hours. 20−40 jets per hour
arrive during hours 0600 and 1000−0100 and depart during
hours 0700 and 2200−2300. During other hours typically fewer
than ﬁve jets per hour arrive or depart.
The airport complex is about 4.5 km east to west (E-W) and
about 2.5 km north to south (N−S) and is surrounded by
major roadways and freeways, as highlighted in Figure 1 (Figure
S.1 in Supporting Information (SI) shows a map of this area
with street name labels). The Federal Aviation Administration
noise contours of the modeled annual 65 dB A-weighted
equivalent (LAeq) noise threshold are shown
eastward along the predominant downwind direction and
reﬂect the jet trajectories used for landing. They also extend
west of the airport over the Paciﬁc Ocean (not shown).
Mobile Monitoring. Monitoring consisted of transects 4−
16 km in length, nearly perpendicular (i.e., N−S) to the
direction of the prevailing winds, at varying downwind
distances. Diﬀerent monitoring routes were required to fully
capture the changes in impact locations due to shifts in wind
direction. A general downwind direction was chosen based on
meteorological predictions but transect lengths and locations
were determined during the monitoring run based on
observations of the rate of change of PN concentrations. For
each transect, monitoring was extended several hundred meters
beyond the location where baseline PN concentrations
Measurements were conducted over 29 days with the
University of Southern California (USC) MMP, a gasoline-
powered hybrid vehicle. A second MMP, the University of
Washington (UW) MMP, a gasoline-powered minivan, joined
the monitoring on 3 days (June 22, 27 and July 1, 2013). Table
1 gives monitoring dates and times.
Most measurements were conducted during times of onshore
westerly winds, typically strongest during 1100−1600, but we
also conducted measurements during early morning and late
night hours when air traﬃc was low and onshore winds were
reduced (August 13, 16, 23, 24 and 25, December 03, 09, 15
and 16, 2013). Monitoring focused on the area east of LAX
(i.e., the predominant downwind direction) but included
several runs along the boundary of the airport in the upwind
direction and south of the airport complex during occasions of
northerly winds in winter months.
Instrumentation. Concentration measurements included
PN, BC, NO, NO2, NOx,and particle surface UV-photo-
ionization potential (measured using Ecochem Photoelectric
Aerosol Sensor [PAS] that responds to elemental carbon and
particle-bound polycyclic aromatic hydrocarbons [PB−PAH]).
Instrument details are provided in SI (Table S.1 and S.2).
Instruments were powered by two deep-cycle marine batteries
via DC-to-AC inverter. Our power arrangement allowed for 5 h
of run time if all instruments were running. For sampling runs
that were anticipated to exceed 5 h, several instruments were
shut down to extend battery life and the Condensation Particle
Counter (CPC) was run on the vehicle’s 12 V cell phone power
outlet. If other instruments were turned on later, the required
warm-up time was 25 min.
Instrument clock times were regularly synchronized to be
within 1 s of the global positioning system device time, which
also recorded speed and location. Measurements from
instruments with a delayed response time were advanced to
match the instantaneous instruments and the GPS time and
location recorded at 1 s intervals. For pollutant measurements
recorded at 10 s intervals, all locations within the recording
interval were assigned the pollutant value reported for that
Meteorological Data. Minute and hourly wind speed and
wind direction data were obtained from the Automated Surface
Observing Systems monitor at LAX airport (latitude 33.943
and longitude −118.407). Due to the 16 km distance between
eastern edge of the study area and the meteorological station
located at LAX, we could not assume that wind speed and
direction were identical to those measured at LAX, but wind
direction in this region of Los Angeles tends to be similar over
large areas during daytime.
The average wind direction at LAX is WSW (252°).
Daytime southwesterly sea breezes typically occur 16 h per day
in the summer (0900−0100 for June−August), decreasing to 6
Figure 1. Los Angeles International Airport and 65 dB noise contours
indicating eastern jet trajectories.
Environmental Science & Technology Article
dx.doi.org/10.1021/es5001566 |Environ. Sci. Technol. 2014, 48, 6628−66356629
h in the winter (1200−1800 in December). Only during the
winter months (November−February, 0000−0900) are light
easterly oﬀ-shore winds common.
Wind speed and direction
during the monitoring periods are summarized in Table 1.
Wind roses based on 1 min data are shown in Figure S.2 and
S.3 of the SI.
Data Processing. MMP measurements included a localized
traﬃc emissions signal representing microscale and middle scale
variations (10−100 m and 100−500 m, respectively) and an
underlying “baseline”pollutant concentration that varied
gradually over the neighborhood scale (500 m−4 km).
Watson et al. 1997
derived these categories by considering
the spatial scales of impact of various types of air pollution
sources. We adopted a smoothing methodology to estimate
baseline PN concentrations that excluded the microscale and
middle scale impacts due to local sources, usually speciﬁc
Baseline PN concentrations were derived from our mobile
measurements by taking a rolling 30-s ﬁfth percentile value of
the 1-s concentration time series, and assigning that value to the
measured location. This removed the microscale and middle
scale impacts from traﬃc sources such as speciﬁc vehicle
plumes. Baseline concentrations for a run were relatively
spatially uniform outside of the LAX impact areas, with
coeﬃcients of variation (CV) of less than 5%. In comparison,
the raw PN concentrations on roadways outside the LAX
impact areas had CVs on the order of 40%. On rare occasions,
the MMP was behind a high emitter for longer than 30 s. Such
events, only if veriﬁable by video and ﬁeld notes, were censored.
However, less than 0.5% of data were censored in this manner,
generated from about a dozen instances of prolonged inﬂuence
from high emitting vehicles. An illustration of both raw and
smoothed concentration time series is presented in the SI
(Figures S.4−S.7). The ﬁgures in this text are based on
■RESULTS AND DISCUSSION
Spatial Pattern and Extent of Elevated PN Concen-
trations. Downwind of LAX we observed gradual but large
increases in baseline PN concentrations occurring over transect
distances of multiple kilometers. PN concentrations were
elevated 4-fold or more above nearby unimpacted baseline
concentrations up to 10 km in the downwind direction from
Table 1. Sampling Days, Time Periods and Meteorological Conditions during Sampling
time sampling distance
from LAX (km) WD
ratio of impacted to unimpacted
baseline PN, 10 km downwind
4/6/2011 14:30−16:45 8−12 WSW, W5.0 ±1.8 15 000 2.0
4/10/2011 15:00−17:30 8−12 W6.9 ±1.2 10 000 4.5
5/24/2011 09:00−11:00 8−12 Calm, W 1.0 ±2.5 10 000 3.0
5/27/2011 12:15−14:45 8−12 WSW, W6.3 ±1.3 10 000 4.7
1/26/2012 17:28−20:22 8−12 WSW, W2.9 ±2.1 20 000 6.0
9/29/2012 13:30−17:30 0−8W6.1 ±1.1 10 000 3.7
9/30/2012 15:45−18:30 0−8W6.1 ±0.4 5000 5.2
6/11/2013 14:14−15:14 2.5−8.5 WSW, W 6.7 ±0.0 15 000 5.0
6/12/2013 13:30−16:30 2.5−10.5 W4.0 ±0.4 15 000 4.0
0−8 WSW, W5.7 ±0.4 10 000 4.4
0−8 WSW, W5.3 ±0.7 10 000 4.0
0−8W, ESE 3.8 ±1.0 15 000 3.8
8/6,7/2013 23:56−02:45 0−8 WSW, W, S 3.3 ±0.7 10 000 3.3
8/13/2013 06:30−15:00 0−8 Calm, WSW, W, NNE, NE,
ENE, E, ESE
3.0 ±2.0 10 000 4.0
8/15/2013 08:30−15:30 0−16 Calm, WSW,W2.5 ±2.1 20 000 3.8
8/16/2013 09:45−20:50 0−16 SW, WSW,W, WNW 4.4 ±1.3 10 000 3.0
8/23,24/2013 12:00−01:30 0−16 SSW, WSW,W4.4 ±2.2 20 000 4.0, 5.0
17:30−01:00 0−16 Calm, SSW, SW, WSW,W,
ESE 3.1 ±2.1 15 000 6.0
11/1/2013 16:00−19:50 0−12 SSE, W, WSW 3.7 ±0.7 10 000 3.8
12/3/2013 19:45−00:20 0−12 WSW, W, WNW 8.8 ±1.4 5000 6.0
12/5/2013 13:00−18:30 0−12 WSW, W, WNW 5.5 ±0.6 10 000 2.8
12/9/2013 16:00−00:00 0−10 N, NNE 2.7 ±0.6 20 000 n/a
12/10/2013 15:30−21:30 0−10 WNW,N, NW 3.1 ±1.1 20 000 5.0
12/14/2013 17:00−20:30 0−10 W, Calm 2.1 ±0.5 20 000 data lost
12/15,16/2013 22:00−02:00 0−10 N, NE, ESE 2.9 ±1.0 17 500 n/a
12/16/2013 10:00−16:00 0−12 N, W 2.8 ±1.6 10 000 4.5
12/18/2013 17:30−20:30 0−10 WSW, SSW, SSE 3.3 ±1.3 10 000 6.0
12/20/2013 16:30−20:00 0−10 WSW, Calm, E 2.6 ±1.3 15 000 4.0
12/23/2013 15:15−19:00 0−12 W, Calm, E 2.8 ±1.3 10 000 11.0
The runs for which maps are presented are formatted in bold.
Predominant wind direction is formatted as bold.
Urban background value
concentrations are reported to nearest 2500 particles/cm3and are the average baseline values in the unimpacted areas away from local traﬃc sources
Concurrent MMP sampling times: June 22:1320−1720, June 27:1325−1510, July 1:1240−1640.
Monitoring route did not cover the full N−S
extent of the impact on Western Av (10 km downwind) on these days, values have been reported for Crenshaw Blvd. (8 km downwind).
ﬂow was recorded in morning hours (until 1000) and westerly later morning to afternoon
08/25/2013 was not counted as an additional monitoring
day because only 1 h of monitoring (0000−0100) was conducted on this date
Environmental Science & Technology Article
dx.doi.org/10.1021/es5001566 |Environ. Sci. Technol. 2014, 48, 6628−66356630
LAX. Figure 2 shows an example of the spatial pattern of the
elevated PN concentrations.
The size of the impacted areas with high PN concentration
increases was remarkable. At 16 km downwind, a 2-fold
increase in PN concentration over baseline concentrations was
measured across 6.5 km. Assuming a trapezoidal shaped plume
with parallel edges of length 1.5 and 6.5 km, PN concentrations
were at least doubled over an area of 60 km2. Eight km
downwind, a 5-fold increase in PN concentrations over baseline
concentrations extended across 3 km and covered a total area of
24 km2. (Concentrations in this large area exceeded 71 000
particles/cm3, the average concentration on Los Angeles
) Within 3 km of the airport boundary, concen-
trations were elevated nearly 10-fold, exceeding 100 000
particles/cm3, with concentrations of 150 000 particles/cm3
occurring over a several km2area.
This pattern of elevated PN concentrations over large areas
east of LAX was consistently observed during periods when
there were both westerly winds and high air traﬃc volumes,
typically all daylight hours and well into the night. Figure 3
Figure 2. Spatial pattern of PN concentration (colored by deciles) for
the afternoon and evening hours of August 23, 2013.
Figure 3. Spatial pattern of impact during diﬀerent monitoring events. Wind direction during monitoring is shown in insets on bottom left. PN
concentrations are classiﬁed and colored by deciles.
Environmental Science & Technology Article
dx.doi.org/10.1021/es5001566 |Environ. Sci. Technol. 2014, 48, 6628−66356631
shows the consistency of the patterns over eight monitoring
runs at various times of day, displayed in each row by similarity
of spatial scale.
In directions other than the downwind direction, no large
areas of elevated PN concentrations were observed. Figures
3(c)−(e) include concentrations measured upwind of the LAX
boundary (these are indicated by faint yellow lines within the
noise contour); the concentrations recorded were typical of the
coastal baseline concentrations, less than 10 000 particles per
cm3(also see Figure S.8 in SI). Of possible other PN sources, a
large reﬁnery is located south of the airport but we did not
observe elevated PN or other pollutant concentrations directly
downwind of this source. In general, industrial point sources of
pollution in the Los Angeles Air Basin are very tightly regulated
by the South Coast Air Quality Management District.
We did not observe distinct day versus night diﬀerences, as
might be expected based on the large change in meteorolog-
ically driven dilution between day and night for ground level
sources. It appeared that the distant impacts we observed
downwind of LAX required suﬃcient wind speeds for the jet
climbing and landing emissions to reach the ground, as
observed in Yu et al., 2004
at LAX and Hong Kong
International Airports and Carslaw et al. 2006
Airport. At LAX, this probably corresponded to the develop-
ment of the on-shore sea breezes that typically started 4−6h
after sunrise and lasted until 3−6 h after sunset.
We also did not see the impacts of individual jets at the
distances monitored, but the merging of individual jet impacts
is not unexpected at distances of multiple km. Considering the
frequency of landings and takeoﬀs (>90 per hour from 0900−
), at an average wind speed of 4 m/s, for example, an
incoming parcel of air will travel only about 160 m before
another jet landing or takeoﬀoccurs. Under normal daytime air
turbulence and the enhanced turbulence produced by jets,
signiﬁcant mixing is expected over a 5−10 km distance (20−40
min). The generally smooth increases and decreases observed
across the length of transects at such distances are additional
evidence that mixing of plumes occurs. Examples of these
smooth concentration increases for individual transects are
shown in Figures S.6 and S.7 in the SI.
The consistent and distinctive spatial pattern of elevated
concentrations was aligned to prevailing westerly winds and
landing jet trajectories, and roughly followed the shape of the
contours of noise from landing jets, indicating that landing jets
probably are an important contributor to the large downwind
spatial extent of elevated PN concentrations. As deﬁned by the
International Civil Aviation Organization, typical engine thrust
during landing is 30%, as compared to 100% for takeoﬀand
85% for the climbing phase.
Stettler et al. 2011
18% of total NOxemissions from landings, with 12% from
taxiing and holding, 18% from takeoﬀ, and 52% from the climb
and climb out phases, respectively. When the extra upwind
distance of the climb and climb out phases are taken into
account, the landing approach emissions likely produce a
signiﬁcant fraction of the increased PN concentrations observed
Inﬂuence of Wind Direction on Location of Impact.
The downwind location of the impact changed with shifts in
the prevailing wind direction, although signiﬁcant shifts in wind
direction during the daytime are not typical of this area of Los
Figure 4(a) and (b) illustrate one such change in
impacted locations due to a shift in wind direction on a gusty
day with frontal weather that also resulted in cleaner upwind
baseline PN concentrations of less than 5000 particles/cm3.
The impacted locations were aligned along the NE direction
during 2000−2220 h when winds were from W to WSW (250−
280°). The impact then moved southwards between 2220−
0000 h as winds turned more W to WNW (280−330°). During
this shift, the impact centerline moved by 5.5 km on transects
8−10 km east of LAX.
Monitoring was also conducted during N to NE prevailing
winds that tend to occur late at night in November and
This N to NE wind direction
resulted in impacts that were centered south of the airport
(Figure 4(c)). The PN concentrations in this southerly impact
were roughly twice as high as on other days, in part because the
baseline PN concentrations reﬂected urban air from northerly
winds instead of marine air from westerly winds.
Diurnal wind patterns change little by season in Los Angeles
Onshore westerly winds are common during midday
hours, even in winter. As a result, areas of elevated PN
Figure 4. Change in location of impact due to shift in wind direction. Wind direction during monitoring is shown in insets on bottom left. PN
concentrations are classiﬁed and colored by deciles.
Environmental Science & Technology Article
dx.doi.org/10.1021/es5001566 |Environ. Sci. Technol. 2014, 48, 6628−66356632
concentrations downwind and east of LAX likely occur in all
seasons. Monitoring in diﬀerent seasons demonstrated the
consistent year round presence of this impact. Examples of
similarly extensive impacts in non-summer months are shown
in the SI (Figures S.8 and S.9).
Other Pollutants. Over large areas downwind of LAX,
concentrations of pollutants other than PN were also elevated.
Figure 5(a)−(c) show nearly indistinguishable spatial patterns
for PN, BC, and NO2concentration measured simultaneously
at distances of 9.5−12 km from LAX. This suggests a common
source for these pollutants, although the BC concentration
increases were not large when compared to PN and NOx, about
0.5−1μg/m3at 8−10 km downwind. While jet aircraft are not
known to produce large amounts of BC, two studies found
elevated BC from plane takeoﬀs at LAX. Zhu et al. 2011
measured an increase of about 1 μg/m3of BC due to plane
activity 140 m downwind of the runway. Westerdahl et al.
measured increases in BC concentration of several μg/
m3during takeoﬀevents near the eastern LAX boundary, but
also observed elevated BC concentrations at all times. At a
smaller airport, Dodson et al. 2009
found median contribu-
tions of about 0.1 μg/m3, about one-quarter of total BC
measured at ﬁve sites ranging in downwind distance from
0.3−3.7 km, and also observed departures producing about
twice the impact as arrivals. Therefore, it appears some jets at
LAX are capable of producing measurable increases in BC,
particularly at takeoﬀs.
Spatial patterns of simultaneously measured PN and PAS
response (PB−PAH and EC) were also similar on transects
4.5−7.5 km from LAX (Figure 5(d)−(e)). The NOXelevation
pattern was less regular (Figure 5(f)). This was likely due to
smaller LAX related contributions compared to baseline
concentrations, thus reducing the signal-to-noise ratio.
Figure 5. Spatial pattern of simultaneously measured pollutants during 1400−1530 on June 27, 2013. Concentrations are classiﬁed and colored by
deciles. Panels (a)−(c) show data measured by the UW MMP and (d)−(f) show data measured by the USC MMP.
Figure 6. Comparison of the spatial scale of freeway impacts compared to airport impacts for monitoring during nighttime on August 23−24, 2013.
Environmental Science & Technology Article
dx.doi.org/10.1021/es5001566 |Environ. Sci. Technol. 2014, 48, 6628−66356633
Overall, the top quartile concentrations (highly impacted) of
all pollutants were about three times higher than the lowest
quartile within 7.5 km from LAX and two times higher at 12 km
distance. In addition, concurrent sampling with the two mobile
platforms demonstrated high temporal (SI Figure S.10) and
spatial consistency (SI Figure S.11) for PN measurements.
Comparison of LAX and Freeway PN Impacts. PN
concentration increases from ground level line sources such as
freeways, under conditions of daytime crosswind dilution,
decrease exponentially with increasing downwind distance and
return to baseline concentrations within 200−300 m.
two N−S freeways (I-405 and I-110 that run perpendicular to
the prevailing winds) did not contribute appreciably to elevated
PN concentrations in areas where we observed large impacts
from LAX on PN concentrations. This is illustrated in Figure 6,
which contains two enlargements to show the increase in PN
number concentrations over approximately 250 m distance
downwind of I-405, a distance and an increase in PN
concentration that is not discernible at the scale of Figures 2
and 3. The panel in Figure 6(c) at 1:10 000 scale shows the PN
concentration increase of about 24 000/cm3. The maximum PN
concentration was not immediately downwind of the freeway
because at this location there is an elevated overpass and some
distance is needed for emissions to reach the ground.
To put into further perspective the extent of the elevated PN
concentrations observed downwind of LAX, we estimated the
freeway length necessary to produce an equivalent impact in
terms of PN concentration-weighted area of impact assuming
typical daytime dilution conditions for freeways.
For the days we captured the fullest downwind extent of the
impact under typical daytime wind conditions (August 15, 23,
and 24), we calculated an integrated PN impact above baseline
PN concentrations of 2.3, 1.6, and 1.1 ×106(particles/cm3)×
km2, respectively. See Table S.3(a)−(c) of SI for calculations.
Impacted areas were calculated using ArcGIS spatial analysis
tools and were conservatively deﬁned as areas where increased
PN concentration were at least double the baseline
concentrations measured north and south of the impact zone.
The resulting impact areas were 30−65 km2. For comparison, a
less conservative criterion for deﬁning the impact area such as a
50% or 33% increase over baseline PN concentrations increased
the impacted area by 40% and 80%, respectively.
To calculate PN impacts downwind of freeways, we
combined the exponential regression ﬁt of near-freeway
measurements made downwind of I-405 by Zhu et al.
with updated average daytime on-freeway PN
concentrations taken from Li et al. 2013
(71 000 particles/
cm3). PN concentrations were at least double the baseline PN
concentrations of 15 000−20 000 particles/cm3for 90−130 m
This resulted in a concentration-weighted impact
area of 2930−3930 (particles/cm3)×km2per km of freeway
Based on these concentration-weighted impact areas, 280−
790 km of freeway are needed to produce the equivalent PN-
concentration-weighted impact area of LAX. (The less
conservative criteria resulted in ranges of freeway length of
340−1000 km and 430−1100 km for thresholds of 50% and
33%, respectively.) There are only about 1500 km of freeways
and highways in Los Angeles County.
Therefore, LAX should
be considered one of the most important sources of PN in Los
Angeles. For comparison, within the 60 km2area of elevated
PN concentrations downwind and east of LAX, the 15−25 km
of freeways contributed less than 5% of the PN concentration
Recommendations for Other Studies. LAX is in a region
of Los Angeles with highly consistent wind direction. This
provided the several hours necessary for a single mobile
platform to monitor a suﬃcient number of transects to cover
the large area impacted by LAX emissions. At airport locations
where the prevailing wind direction frequently shifts during the
day, multiple platforms would be necessary to quickly capture
the full spatial extent of emissions impacts to surrounding air
The emissions from LAX are likely not unique on a per-
activity basis. The large area of impact from LAX suggests that
air pollution studies involving PN, localized roadway impacts,
or other sources whose impacts are in the inﬂuence zone of a
large airport should carefully consider wind conditions and
whether measurements are inﬂuenced by airport emissions.
Source apportionment of speciﬁc airport sources or activities
was beyond the scope of our study but would be necessary to
evaluate the eﬀectiveness of possible mitigation options.
Diﬀering NO2to NOxratios at diﬀerent levels of engine
might be used to distinguish the contributions of jet
landing, idling or takeoﬀactivities. Takeoﬀand idling emission
also diﬀer in surface properties (i.e., the ratio of active surface
area to surface bound photoionizable species)
size distributions diﬀer between aircraft and ground support
Map of monitoring area (Figure S.1), the instruments used
(Tables S.1−S.2), wind roses (Figures S.2 and S.3), illustration
of data processing (Figures S.4−S.7), additional maps
illustrating the spatial pattern (Figures S.8 and S.9), concurrent
sampling with two mobile measurement platforms (Figures
S.10 and S.11) and calculations for comparing freeway impact
(Table S.3 (a)−(c)) are presented in the Supporting
Information. This material is available free of charge via the
Internet at http://pubs.acs.org.
*Phone: 323-442-2870; fax: 323-442-3272; e-mail: fruin@usc.
S.A.F.: Keck School of Medicine, Department of Preventive
Medicine, University of Southern California, 2001 North Soto
Street, Los Angeles, CA 90089-9013, United States.
The authors declare no competing ﬁnancial interest.
This work was funded by National Institute of Environmental
Health Sciences (NIEHS) Grant 1K25ES019224-01 and
5P30ES007048 to the University of Southern California and
by US EPA Grant RD-83479601-0. This publication’s contents
are solely the responsibility of the grantee and do not
necessarily represent the oﬃcial views of NIEHS or US EPA.
Further, NIEHS and U.S. EPA do not endorse the purchase of
any commercial products or services mentioned in the
publication. We thank Andrea Hricko of USC for helpful
Environmental Science & Technology Article
dx.doi.org/10.1021/es5001566 |Environ. Sci. Technol. 2014, 48, 6628−66356634
(1) Carslaw, D. C.; Beevers, S. D.; Ropkins, K.; Bell, M. C. Detecting
and quantifying aircraft and other on-airport contributions to ambient
nitrogen oxides in the vicinity of a large international airport. Atmos.
Environ. 2006,40 (28), 5424−5434.
(2) Yu, K. N.; Cheung, Y. P.; Cheung, T.; Henry, R. C. Identifying
the impact of large urban airports on local air quality by nonparametric
regression. Atmos. Environ. 2004,38 (27), 4501−4507.
(3) Fanning, E., Yu, R. C., Lu, R., Froines, J. Monitoring and Modeling
of Ultraﬁne Particles and Black Carbon at the Los Angeles International
Airport; California Air Resources Board, 2007.
(4) Dodson, R. E.; Houseman, E. A.; Morin, B.; Levy, J. I. An analysis
of continuous black carbon concentrations in proximity to an airport
and major roadways. Atmos. Environ. 2009,43 (24), 3764−3773.
(5) Klapmeyer, M. E.; Marr, L. C. CO2,NO
xand particle emissions
from aircraft and support activities at a regional airport. Environ. Sci.
Technol. 2012,46, 10974−110981.
(6) Stettler, M. E. J.; Eastham, S.; Barrett, S. R. H. Air quality and
public health impacts of UK airports. Part I: Emissions. Atmos. Environ.
(7) Hsu, H. H.; Adamkiewicz, G.; Houseman, E. A.; Zarubiak, D.;
Spengler, J. D.; Levy, J. I. Contributions of aircraft arrivals and
departures to ultrafine particle counts near Los Angeles International
Airport. Sci. Total Environ. 2013,444, 347−355.
(8) Westerdahl, D.; Fruin, S. A.; Fine, P. M.; Sioutas, C. The Los
Angeles International Airport as a source of ultrafine particles and
other pollutants to nearby communities. Atmos. Environ. 2008,42,
(9) Zhu, Y.; Fanning, E.; Yu, R. C.; Zhang, Q.; Froines, J. R. Aircraft
emissions and local air quality impacts from takeoff activities at a large
international airport. Atmos. Environ. 2011,45, 6526−33.
(10) California State Airport Noise Standards Quarterly Report, First
Quarter, Los Angeles World Airports, September 18, 2013. http://
www.lawa.org/welcome_lax.aspx?id=1090 (accessed December 03,
(11) Los Angeles County Regional Planning Department, Airport
Land Use Commission, DRP_Airport_Inﬂuence_Areas. http://egis3.
cessed April 19, 2014).
(12) Fisk, C. J. Diurnal and Seasonal Wind Variability for Selected
Stations in Southern California Climate Regions, 20th Conference on
Climate Variability and Change; American Meteorological Society:
New Orleans, January 20−24, 2008; http://ams.confex.com/ams/
pdfpapers/135164.pdf (accessed November 11, 2013).
(13) Watson, J. G.; Chow, J. C.; DuBois, D. W.; Green, M. C.; Frank,
N. H.; Pitchford, M. L. Guidance for Network Design and Optimal Site
Exposure for PM2.5 and PM10, Report No. EPA-454/R-99-022; U.S.
Environmental Protection Agency, Research Triangle Park, NC. 1997.
(14) Li, L.; Wu, J.; Hudda, N.; Sioutas, C.; Fruin, S. A.; Delfino, R. J.
Modeling the concentrations of on-road air pollutants in southern
California. Environ. Sci. Technol. 2013,47 (16), 9291−9299.
(15) Graham, A.; Raper, D. W. Transport to ground of emissions in
aircraft wakes. Part I: Processes. Atmos. Environ. 2006,40, 5874−85.
(16) Graham, A.; Raper, D. W. Transport to ground of emissions in
aircraft wakes. Part II: Effect on NOxconcentrations in airport
approaches. Atmos. Environ. 2006,40, 5824−36.
(17) Karner, A.; Eisinger, A.; Niemeier, D. Near-roadway air quality:
Synthesizing the findings from real-world data. Environ. Sci. Technol.
(18) Zhu, Y.; Hinds, W. C.; Kim, S.; Shen, S.; Sioutas, C.
Concentration and size distribution of ultrafine particles near a
major highway. J. Air Waste Manage. Assoc. 2002a,36 (27), 4323−
(19) California Department of Transportation. http://www.dot.ca.
gov/dist07/aboutus/proﬁle/d7p_print.html (accessed November 11,
(20) Herndon, S. C.; Shorter, J. H.; Zahniser, M. S.; Nelson, D. D. J.;
Jayne, J. T.; Brown, R. C.; Miake-Lye, R. C.; Waitz, I. A.; Silva, P.;
Lanni, T.; Demerjian, K. L.; Kolb, C. E. NO and NO2emissions ratios
measured from in use commercial aircraft during taxi and take-off.
Environ. Sci. Technol. 2004,38, 6078−84.
(21) Herndon, S. C.; Onasch, T. B.; Frank, B. P.; Marr, L. C.; Jayne,
J. T.; Canagaratna, M. R.; Grygas, J.; Lanni, T.; Anderson, B. E.;
Worsnop, D.; Miake-Lye, R. C. Particulate emissions from in-use
commercial aircraft. Aerosol Sci. Technol. 2005,39 (8), 799−809,
Environmental Science & Technology Article
dx.doi.org/10.1021/es5001566 |Environ. Sci. Technol. 2014, 48, 6628−66356635