Monitoring exposure to airborne ultrafine particles in Lisbon, Portugal.

Abstract

The aim of this study is to contribute to the assessment of exposure levels of ultrafine particles (UFP) in the urban environment of Lisbon, Portugal, due to automobile traffic, by monitoring lung-deposited alveolar surface area (resulting from exposure to UFP) in a major avenue leading to the town centre during late Spring, as well as in indoor buildings facing it. This study revealed differentiated patterns for week days and weekends, consistent with PM(2.5) and PM(10) patterns currently monitored by air quality stations in Lisbon. The observed ultrafine particulate levels could be directly related with the fluxes of automobile traffic. During a typical week, UFP alveolar deposited surface area varied between 35.0 and 89.2 µm(2)/cm(3), which is comparable with levels reported for other towns such in Germany and United States. The measured values allowed the determination of the number of UFP per cm(3), which are comparable to levels reported for Madrid and Brisbane. In what concerns outdoor/indoor levels, we observed higher levels (32-63%) outdoor, which is somewhat lower than levels observed in houses in Ontario.

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425
Introduction
The adverse health effects of particulate matter have
been reported in numerous scientific studies (Pope &
Dockery, 2006; Buonanno et al., 2010). A number of
epidemiological studies also associated these effects with
particle mass concentration including PM2.5 (Pope, 2000)
and PM10 (Loomis, 2000), as well as ultrafine particle
(UFP), number concentration (Hauser et al., 2001),
surface area concentration (Driscoll, 1996), and overall
exposure rate (Siegmann & Siegmann, 1998). Apart
from that, a number of studies worldwide have found an
elevated risk of lung and ovarian cancer associated with
exposure to diesel engine fumes and other emissions
derived from automobile traffic (Ramachandran et al.,
2005). An important information gap, that limits the
use of this data for epidemiological studies and risk
assessment evaluations, is the absence of quantitative
exposure data from which to estimate the dose-response
relationship (Mauderley, 1992). It is not clear, at the
moment, which fraction of the particulate matter is
responsible for the health effects. Nearly all of the mass
emitted by engines is in the fine particle range and nearly
all the number is in the nanoparticle range (Kittelson,
1992). Several studies have suggested that, at similar
mass concentrations, nanometer size particles are more
harmful than micron size particles (Seaton et al., 1995;
Oberdörster, 1996). One possible cause for this might
be that, since the number of particles and also particle
surface area per unit mass increases with decreasing
particle size, and also as pulmonary deposition increases
with decreasing particle size, the dose by particle
number or the surface area will increase as the particle
MeasureMent technology
Monitoring exposure to airborne ultrafine particles in
Lisbon, Portugal
João Fernando Pereira Gomes1,2, João Carlos Moura Bordado1, and Paula Cristina Silva
Albuquerque3
1IBB – Instituto de Biotecnologia e Bioengenharia/Instituto Superior Técnico – Universidade Técnica de Lisboa,
Lisboa, Portugal, 2ISEL – Instituto Superior de Engenharia de Lisboa, Área Departamental de Engenharia Química, R.
Conselheiro Emídio Navarro, Lisboa, Portugal, and 3ESTESL – Escola Superior de Tecnologias de Saúde de
Lisboa – Instituto Politécnico de Lisboa, Lisboa, Portugal
abstract
The aim of this study is to contribute to the assessment of exposure levels of ultrafine particles (UFP) in the urban
environment of Lisbon, Portugal, due to automobile traffic, by monitoring lung-deposited alveolar surface area
(resulting from exposure to UFP) in a major avenue leading to the town centre during late Spring, as well as in indoor
buildings facing it. This study revealed differentiated patterns for week days and weekends, consistent with PM2.5 and
PM10 patterns currently monitored by air quality stations in Lisbon. The observed ultrafine particulate levels could be
directly related with the fluxes of automobile traffic. During a typical week, UFP alveolar deposited surface area varied
between 35.0 and 89.2 µm2/cm3, which is comparable with levels reported for other towns such in Germany and
United States. The measured values allowed the determination of the number of UFP per cm3, which are comparable
to levels reported for Madrid and Brisbane. In what concerns outdoor/indoor levels, we observed higher levels
(32–63%) outdoor, which is somewhat lower than levels observed in houses in Ontario.
Keywords: Airborne ultrafine particles, urban environment, indoor/outdoor
Address for Correspondence: João Fernando Pereira Gomes, IBB – Instituto de Biotecnologia e Bioengenharia/Instituto Superior
Técnico – Universidade Técnica de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa, Portugal. Tel: +351.96.3902456; Fax: +351.21.8317001.
E-mail: jgomes@deq.isel.ipl.pt
(Received 06 March 2012; revised 04 April 2012; accepted 06 April 2012)
Inhalation Toxicology, 2012; 24(7): 425–433
© 2012 Informa Healthcare USA, Inc.
ISSN 0895-8378 print/ISSN 1091-7691 online
DOI: 10.3109/08958378.2012.684077
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426 J. F. P. Gomes et al.
Inhalation Toxicology
size decreases (Ramachandran et al., 2005). Current
workplace and ambient air environmental exposure
limits, that have been established long ago, are based
on particle mass. However, this criterion does not seem
adequate in what concerns UFP as these materials are,
in fact, characterized by very large surface areas, which
has been pointed out as the distinctive characteristic
that could even turn out an inert substance into a toxic
substance, having the same chemical composition, but
exhibiting very different interactions with biological
fluids and cells (Pope & Dockery, 2006). Therefore,
it seems that, assessing human exposure based on
the mass concentration of particles, which is widely
adopted for particles over 1 µm, would not be adequate
in this particular case. In fact, UFP have far more surface
area for the equivalent mass of larger particles, which
increases the chance that they may react with body
tissues (Buonanno et al., 2010). Thus, a growing number
of experts (Pope, 2000; Loomis, 2000) have been claiming
that surface area should be used for UFP exposure and
dosing. As a result, assessing workplace conditions and
personal exposure based on the measurement of particle
surface area is of increasing interest. It is well-known
that lung deposition is one of the most efficient ways
for airborne particles to enter the body and potentially
cause adverse health effects. If UFP can deposit in the
lung and remain there, have an active surface chemistry
and interact with the body, then, there is a strong
potential for exposure and dosing. (Oberdörster, 1996)
showed that surface area plays an important role in the
toxicity of nanoparticles, and this is the measurement
metric that best correlates with particle-induced
adverse health effects. The potential for adverse health
effects is directly proportional to particle surface area
(Driscoll, 1996). Although the mass concentration of
fine particles, namely in the ranges of PM2.5 and PM10,
has been currently monitored in urban environments in
large towns worldwide, very few studies have been made
regarding UFP, as referred in Table 1. The majority of
these studies report concentrations in terms of number
of particles per cm3, while some other groups measured
UFP concentration in terms of surface area, expressed
as µm2/cm3, which we feel is the most significant metric
in what concerns this type of pollutant, particularly
bearing in mind the existing relationship between
surface area of UFP and its health effects. Regarding
indoor concentrations some studies were focused on the
determination of fine particles concentration, expressed
as #/cm3, as described also in Table 1, but none of these
studies comprised the determination of surface area of
indoor particles.
The primary aim of this study is to contribute to the
assessment of exposure levels of UFP in the urban envi-
ronment of Lisbon, Portugal, due to automobile traffic,
by monitoring lung-deposited alveolar surface area
(resulting from exposure to UFP) in a major avenue
leading to the town centre during late Spring, as well as
in indoor buildings facing it.
Methods
Sampling site
Measurements were made in 56 consecutive days on
late spring, from the 4th of April until the 30th of May,
2011, on a trailer which was located downwind on a
4-lane avenue in Lisbon, Portugal, shown in Figure 1,
which is one of the main accesses to the town center
coming from West (Benfica) and its surroundings. The
measurements were made during the dry season, in the
absence of rain. Lisbon has a subtropical-mediterranean
climate with mild winter and warm to hot summers. The
annual average temperature is 17°C, 21°C during the
day and 13°C at night, with an annual precipitation of
725.8 mm mainly concentrated in autumn and winter
months. Summer lasts about 6 months, from May to
October. In the measuring period, the average daily
temperature was 17.4°C, with a maximum temperature of
21.4°C during day and a minimum temperature of 13.3°C
at night. The consistency of this weather on a daily basis
ensures that representative results were obtained during
the duration of this study. Previous studies focused on
air pollution episodes in Lisbon area have characterized
their driving meteorological conditions as well as their
typical atmospheric patterns: in summer the situation
permits the development of mesoscale flows land-sea
breeze and upslope-downslope (anabatic-katabatic)
flow (Barros et al., 2003), leading to the occurrence of
episodic air pollution events. Thus, the worst pollution
Table 1. Previous studies measuring outdoor and indoor levels of
fine and ultrafine particles.
Particle
sizes
sampledunits
Beijing, Paris,
Mexico City,
New York,
Tokyo, Zurich
Birmingham,
UK
Brisbane,
Australiaparticles
(UFP)
Madrid, Spain UFP#/cm3
Sampling sites
Measuring Outdoor/
indoor
Outdoor Zhiqiang et al.,
2000
References
>1 µm #/cm3
<10 µm#/cm3
Outdoor Shi et al., 2001
Ultrafine
#/cm3
Outdoor Morawska
et al., 2002
Outdoor Gomez-Moreno
et al., 2011
Outdoor Ramachandran
et al., 2005
Outdoor Kuhlbusch
et al., 2004
Outdoor Ntziachristos
et al., 2007
Outdoor
and
indoor
IndoorHoek et al.,
2008
Minneapolis,
USA
Dusseldorf,
Germany
Los Angeles,
USA
Espoo, Finland
UFP µm2/cm3
UFPµm2/cm3
UFPµm2/cm3
UFP#/cm3
Hussein et al.,
2006
Helsinki, Athens,
Amsterdam,
Birmingham
Windsor,
Canada
UFP#/cm3
UFP#/cm3
Outdoor
and
indoor
Kearney et al.,
2011
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Exposure to ultrafine particles 427
© 2012 Informa Healthcare USA, Inc.
episodic situations in this region usually coincide
with typical summer weather. During the sampling
periods no air pollution episodes took place, and no
significant Eastern Atlantic Ocean influence occurred
in the sampling site as it is located in the middle of the
town, surrounded by tall buildings. It is estimated that
exhaust gases from automobiles account for 44.0% and
11.7% of NOx and volatile organic compounds emissions
respectively, in Lisbon area, and 12.5% of PM10 (Gois
et al., 2009). The contribution of exhaust gas emissions to
the concentration levels of UFP has not been quantified
previously, but it is expected to be substantial. The
automobile traffic fluxes entering and leaving the center
of Lisbon have been previously monitored for these
main access avenues (Rocha, 2008). It was noticed that
the incoming traffic during the morning increases from
400 until 1,000 vehicles/h from 8:00 am to 9:00 am. In
the afternoon, the opposite flux leaving the town center
increases from 800 to 1,000 vehicles/h between 1700
h and 1800 h and sometimes reaches 1,100 vehicles/h
at 2000 h, during working days. It is also estimated that
this traffic consisted of about 40% of diesel vs. 60% of
gasoline-fueled vehicles.
Through this avenue, where measurements have been
done, heavy fluxes of traffic enter the town, consisting
of automobiles, trucks, and buses. For comparison pur-
poses, the air quality data on particulate emissions (PM2.5
and PM10) measured regularly on two nearby station in
Entrecampos and Av. da Liberdade were also obtained as
part of the information made public by the Portuguese
Ministry of Environment. Measurements were made dur-
ing week days and also at weekends, during 24-h periods,
every 10 s. This station is also located in a 4-lane avenue
of Lisbon, which has similar traffic patterns of the sam-
pling site. Also, indoor measurements were done inside
the room (facing the avenue) of an apartment on the
second floor of an eight-stories high building located in
the same avenue where other measurements took place.
This building is directly facing the site where the trailer
was installed, so that we can assume that the sampling
location is only one, but situated at two different heights:
at ground level (trailer) and at two stories high (indoor).
Regarding outdoor, baseline measurements were made
inside the trailer.
Measuring equipment
For measuring UFP exposure a Nanoparticle Surface Area
Monitor (NSAM), TSI, Model 3550 (Shoreview, MN), was
used. This equipment indicates the human lung-deposited
surface area of particles expressed as square micrometers
per cubic centimeter of air (µm2/cm3), corresponding
to tracheobronchial (TB) or alveolar (A) regions of the
human lung, according to the ICRP deposition model
developed by ACGIH (Phalen, 1999). This equipment
is based on diffusion charging of sampled particles,
followed by detection of the charged aerosol using an
electrometer. Using an integral pump, an aerosol sample
is drawn into the instrument through a cyclone with a
1 µm cut point. The sample flow is then split, one stream
going through a set of carbon and HEPA filters and an
ionizer to introduce positively charged ions into a mixing
chamber. The other aerosol flow stream is mixed with
the ionized stream in a mixing chamber and charged
aerosol and excess ions move onto an ion trap. The ion
trap voltage can be set to TB or A response. The ion trap
acts as an inlet conditioner or a size-selective sampler
for the electrometer, by collecting the excess ions and
particles that are not of a charge state, corresponding to
the TB or A response settings. The aerosol, then moves
on to the electrometer for charge measurement, where
current is passed from the particles to a conductive filter
and measured by a very sensitive amplifier. The charge
Figure 1. Location of sampling site in Lisbon (red dot indicates sampling site and green dots indicates Entrecampos and Av. Liberdade air
quality stations).
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428 J. F. P. Gomes et al.
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measured by the electrometer is directly proportional
to the surface area of the particles passing through the
electrometer.
Particle number concentration and size distribution
were measured using a Scanning Mobility Particle Size
Spectrometer (SMPS), TSI, Model 3034 (Shoreview, MN).
The system consists of three components, (i) a bipolar
radioactive charger for charging the particles, (ii) a dif-
ferential mobility analyzer for classifying particles by
electrical mobility, and (iii) a condensation particle
counter for detecting particles. The SMPS measures Dp
(in terms of electrical mobility diameter) between 10 and
487 nm using 54-size channels (32 channels per decade)
for number concentrations in the range from 102 to 107
#/cm3.
Morphological analysis were conducted using a
Nanometer Aerosol Sampler, TSI, Model 3089 (Shoreview,
MN) to collect particles on a mesh Transmission
Electron Microscopy (TEM) copper grid with a carbon/
formvar support film, and these samples were analyzed
throughaTEM microscope, FEI, model Tecnel G2, 200 kV,
Twin Lens.
results and discussion
Measurement results, over a typical week, are presented
in Table 2, which also shows calculated values of time-
weighted average (TWA) for 8-h periods, total deposited
alveolar area and lung area covered by particle matter. It
should be noted that TWA is the average exposure over
a specified period of time, usually a nominal 8 h, which
is a parameter frequently used in exposure assessments
in indoor environments. Although it is usually not fre-
quently used for outdoor environments, it is useful for
further comparisons with indoor exposures.
Apart from TWA, Table 2, also shows total deposited
alveolar area, which is calculated as the sum of all mea-
sured instantaneous deposited alveolar area values dur-
ing sampling period; and lung area covered by particles
which is calculated by dividing the total deposited alveo-
lar area per an average lung area of 80 m2.
Table 2. Measurement results over a typical week (late Spring, 2011).
Sampling
conditions(µm2/cm3)
Baseline34.1 ± 5.0
Monday57.6 ± 5.7
Tuesday89.2 ± 8.0
Wednesday87.1 ± 7.5
Thursday 82.2 ± 7.2
Friday 75.0 ± 6.9
Saturday35.0 ± 4.5
Sunday34.9 ± 4.0
TWA, time-weighted average.
Average deposited area
Range of values
(µm2/cm3)
25.5–50.3
14.7–343.3
27.4–510.5
31.1–421.1
23.2–245.7
17.8–511.1
6.91–365.5
4.94–252.2
TWA for 8 h
(µm2/cm3)
1.07
172.8
267.6
261.4
165.2
143.6
107.4
104.7
Total deposited area
(µm2)
5.12 × 105
8.29 × 107
1.28 × 108
1.25 × 108
4.72 × 107
4.70 × 107
4.26 × 107
4.10 × 107
Lung area covered by
particles (µm2/m2)
6.40 × 103
1.04 × 106
1.61 × 106
1.57 × 106
5.90 × 105
4.60 × 105
3.40 × 105
3.20 × 105
Figure 2. Measurements over a typical week day: Tuesday, the 10th
May 2011.
Figure 3. Measurements over a typical week day: Wednesday, the
11th May 2011.
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Exposure to ultrafine particles 429
© 2012 Informa Healthcare USA, Inc.
Figure 2 shows the measured alveolar deposited
surface area from 0000 h of Tuesday, the 10th May 2011
until 2400 h of the same day, a typical week day. Figure 3
shows the same type of measurements for the following
day, Wednesday, the 11th May 2011, from 0000 to 2400 h,
another typical week day. Figure 4 shows measurements
done from 0000 to 2400 h of Sunday, the 8th May 2011, a
typical weekend day.
In selected periods, measurements were made both
indoor and outdoor, in terms of A and also TB deposition
modes, which are presented in Table 3.
These measurements exhibited differentiated patterns
for week days and also for weekend days, as expected,
and previously noticed for other urban environments
(Morawska et al., 2002; Ntziachristos et al., 2007). As
the obtained measurements have shown always similar
patterns regarding weekdays and weekend days, other
measurements are not shown here.
Figure 5, which shows three superimposed week day
patterns (sample 4 = Tuesday, sample 5 = Wednesday, sam-
ple 6 = Thursday), shows the similarity of those patterns.
On the opposite, Figure 6, which shows superimposed
week (sample 3 = Monday, sample 4 = Tuesday, sample
Table 3. Indoor/outdoor measurement results over typical days (late Spring, 2011).
Sampling conditions
Weekend indoor (TB)
Weekend oudoor (TB)
Weekend indoor (A)
Weekend outdoor (A)
Weekday indoor (A)
Weekday outdoor (A)
A, alveolar; TB, tracheobronchial; TWA, time-weighted average.
Average deposited area
(µm2/cm3)
5.7 ± 0.3
16.6 ± 9.1
33.1 ± 5.0
59.2 ± 24.4
29.1 ± 1.0
108.3 ± 38.1
Range of values
(µm2/cm3)
5.18–6.29
6.91–73.1
24.5–51.3
17.5–188.7
26.9–31.4
35.5–239.2
TWA for 8 h
(µm2/cm3)
0.49
1.61
1.07
10.2
2.49
21.4
Total deposited area
(µm2)
2.33 × 105
7.74 × 105
5.11 × 105
4.88 × 106
1.19 × 106
1.03 × 107
Lung area covered
by particles
(µm2/m2)
2.92 × 103
9.68 × 103
6.40 × 103
6.10 × 104
1.49 × 104
1.29 × 105
Figure 4. Measurements over a typical weekend day: Sunday, the
8th May 2011.
Figure 5. Superimposed measurements for 3 week days.
Figure 6. Superimposed measurements for 7 days, both week days
and weekend days.
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430 J. F. P. Gomes et al.
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5 = Wednesday, sample 6 = Thursday, sample 7 = Friday) and
also weekend days (sample 1 = Saturday and sample 2 =
Sunday), exhibits considerable differences which can be,
of course, attributed to heavier fluxes of automobile traffic
during week days when compared to weekend days.
On week days, the diurnal profile of the particle surface
concentrations shows that in the early night hours, from
000 to around 0300 h, the concentrations have values in
the approximate range of the baseline. Some small peaks
can be observed around 0300 h, during a short time (15–30
min) which can be attributed to the traffic fluxes of garbage
collection trucks as well as street cleaning vehicles, both
operated on diesel fuel, operating at this period. As particle
surface concentrations are clearly influenced by automobile
traffic, concentrations clearly start to increase from 0500 to
0600 h, thus reflecting traffic entering the center of the town.
At these early hours, traffic is mostly constituted by trucks
and buses largely fueled by diesel. This traffic fluxes entering
the town continues to increase during early morning and
reaches a maximal peak around 0700–0730 h. However,
the traffic fluxes usually do not diminish until 0900–0930
h which is not shown in the measured concentrations,
where a slight decrease can be observed in this period. This
is possibly due to an alteration on the traffic profile from
the previous hours which is now mainly constituted by
gasoline-fueled vehicles, circulating, at first, at low velocity
and, afterwards, in intense and compact traffic jams. These
traffic jams are certainly the cause for another concentration
peaks appearing around 0900–0930 h. Concentrations
then decrease until new peaks are observed near lunch
hour (1200 h) thus accounting for heavier traffic fluxes,
but based on gasoline-fueled vehicles. Concentrations
start to rise again during the afternoon, around
1700–1800 h, accounting for traffic leaving the center of
the town. Further on, concentrations are still elevated,
compared to baseline, until 2100 h, where other, less
intense, peaks are reached. After 2100 h, concentrations
drop slowly until 2400 h and until 0200–0300 h of the
following day. It can be noticed that this daily pattern is
reproducible in the next week day.
However, in weekend days, concentrations are much
smaller, seldom surpassing the baseline, with scattered
peaks during all day, more concentrated near lunch hour
and early afternoon. During weekend days there are nei-
ther heavy traffic fluxes nor rush hours, which are reflected
in the measurements taken. Also during these days, traffic
is mainly composed by gasoline-fueled vehicles.
Figure 7 shows the mass concentration variation pat-
tern of PM10 measured at the nearby air quality station
of Entrecampos, during the same weekdays depicted
in Figures 2 and 3: although there are some similarities
regarding the occurrence of concentration peaks during
rush hours, no sound correlation was found between
measured alveolar deposited surface area and PM10, as
the involved metric is completely different as explained
previously.
Figures 8 and 9 show the measured size distribution
measured with the SMPS analyzer: Figure 8 shows Dp,
the electrical mobility diameter and number of particles
on a typical week day, corresponding to an average diam-
eter of 16.9 ± 1.46 nm and an average number of particles
(dN/dlogDp) of 4.53 × 104 #/cm3. Figure 9 refers to a typi-
cal weekend day, corresponding to an average diameter
of 128.6 ± 1.97 nm and an average number of particles of
7.5 × 103 #/cm3. The observed differences, during week
Figure 7. Typical PM10 concentration pattern measured at
Entrecampos air quality station during week days: Tuesday, the
10th and Wednesday, the 11th May 2011.
Figure 8. Size distribution of particles during a typical week day:
Tuesday, the 10th May 2011.
Figure 9. Size distribution of particles during a typical weekend
day: Sunday, the 8th May 2011.
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Exposure to ultrafine particles 431
© 2012 Informa Healthcare USA, Inc.
and weekend days, are consistent with a majority of gas-
oline-fueled vehicles during weekend compared to week
days where diesel fueled vehicles (trucks and buses) are
in considerable higher number.
Figure 10 shows the evolution of the median values
of number of particles and Dp for each day of the week,
as computed from the number size distribution spectra
measured by the SMPS. Each point is the mean between
all days of this study and the error bars represent the
respective standard errors of all readings corresponding
to each day of the week.
Figure 11 shows a TEM image of ultrafine particulate
collected using the nanometer aerosol sampler, during
a week day. As expected (Health Effects Institute, 1995)
the collected particles seem to be composed of carbo-
naceous agglomerates of irregular shape, similarly to
vehicle exhaust particles from diesel fueled vehicles.
From the values shown in Table 2, it can be noted that
outdoor levels are 32% higher during weekend days and
63% higher during weekdays, when compared to baseline
levels. Also, it should be noted that the measured deposited
surface area is within the same order of magnitude as the
values measured by (Kuhlbusch et al., 2004) in the Ruhr
area, of 30–45 µm2/cm3 and by (Ntiziachristos et al., 2007)
in Los Angeles area, of 38–71 µm2/cm3. In what concerns
number of particles, (Morawska et al., 2002) measured
6,330/cm3 on weekends and 8,010/cm3 on week days for
Brisbane; while (Gomez-Moreno et al., 2011) measured
2,000–19,000/cm3 on week days in Madrid, which means
that the measured number of particles in this study is
considerably high. In spite of this, the evolution pattern,
noticed by (Morawska et al., 2002), on the number of
particles and its diameter during week days and weekends
was again observed in this study, as shown in Figures 12
and 13.
In what regards the measured levels of deposited alve-
olar surface area it should be noticed that outdoor levels,
during week days, show considerable increases from the
baseline, from 160 to 260%. This clearly points out for high
exposures to UFP in the urban environment of central
Lisbon, as also indicated by the measured total depos-
ited area and lung area covered by particles mentioned
Figure 10. Evolution of size distribution over a typical week: mean particle number concentration and mean particle median electrical
mobility diameter as a function of the day of the week based on all the monitoring data obtained during this study, with SE bars on the y-axis.
Figure 11. TEM image of ultrafine particulates collected on Tuesday,
the 10th May 2011. TEM, transmission electron microscopy.
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432 J. F. P. Gomes et al.
Inhalation Toxicology
in Table 2, when compared to baseline. This observation
is an indicator of a strong potential for occurrence of lung
related diseases due to the exposure to high doses of UFP
in this urban environment.
Concerning indoor/outdoor ratios, (Kearney et al.,
2011) observed that in Windsor, Ontario, outdoor levels
were 75–86% higher than indoor levels, which is consis-
tent with the findings of the present study.
When referring to lung-deposited area in TB tract
measurements, it was found, as expected (Anastacio &
Martin, 2001; Health Effects Institute, 1995; Mauderley,
1992), that both indoor and outdoor levels are lower
than the lung deposited area in A tract: comparing val-
ues for the same situation, alveolar measurement ranges
from 74 to 78% of (alveolar+tracheoronquial) levels. This
points out to an increased exposure risk posed by very
UFP (which deposit in the alveolar range) in urban envi-
ronments such as this.
conclusions
This set of measurements is the first stage of a study com-
prising the determination of the levels of airborne UFP in
the urban atmosphere of Lisbon, with the aim to contrib-
ute, further on, to establish epidemiologic correlations
on the exposure to exhaust gases.
The study clearly demonstrated the existence of UFP
due to automobile traffic which seem to be consistent
with observations of UFP concentrations in other major
towns. Mainly during week days, observed concentra-
tions can be as high as 2.6 times the measured baseline
level.
It should be noted that, although measured parameters
such as the deposited area and the lung area covered by
particles, are elevated when compared with baseline
values, mainly for week days where automobile traffic is
more intense, they cannot, at this stage, be ascertained
as toxicity indicators. Nevertheless, they point out for the
existence of an important contamination of potentially
hazardous particles released from automobile traffic
in urban environments. Data obtained in this study is
basic information for understanding the relationship
between exposure to UFP in urban atmospheres and
health affections, which can be taken as the basis for
epidemiologic studies. As UFP can have a significant
lifetime in urban air, possible effects on health cannot be
neglected.
acknowledgments
The authors would like to thank Ms. Rita Santos and Prof.
Teresa Vieira, from Coimbra University, for their help in
ultrafine particulate characterization.
Declaration of interest
The authors declared no conflicts of interest.
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