Journal of Environmental Protection, 2011, 2, 974-981
doi:10.4236/jep.2011.27112 Published Online September2011 (http://www.SciRP.org/journal/jep)
Metanalysis: Respiratory Effects in the General
Population Exposed to Urban Pollution
Angela Sancini, Francesco Tomei, Assunta Capozzella, Alessandro Pacchiarotti, Simone De Sio,
Gianfranco Tomei*, Paola Palermo, Manuela Ciarrocca
University of Rome “Sapienza”, Rome, Italy.
Received March 30th, 2011; revised July 14th, 2011; accepted August 24th, 2011.
ABSTRACT
Aim: The purpose of this study was to evaluate spirometric lung function parameters in the general population exposed
to urban pollution and confirm the existence of an association between exposure to environmental pollutants and effects
from these products and which respiratory parameters are associated to urban pollution in general population.
Methods: This study is a systematic research of all articles on the assessment of respiratory effects on general
population exposed to urban pollution, excluding studies on adolescents and children. The research included articles
from January 2008 to May 2009. In the articles included in our meta-analysis, the exposed group is represented by
general population aged between 15 and 75 years for both genders, resident in very polluted urban areas, while the
control group is represented by general population resident in rural and suburban areas, where pollution is lower.
Results: The results confirm the presence of statistica lly significant effects of urban pollu tion on the respiratory system
for cough, phlegm, shortness of breath/breathlessness, wheezing, FVC, FEV1, PEFR, chronic bronchitis, bronchial
asthma, rhinitis, emphysema.
Keywords: Urban Pollution, Respiratory Symptoms on General Population , Lung Disease, Environmental Exposure
1. Introduction
On the basis of the assessment conducted by WHO, urban
pollution is a very significant public health problem.
Studies of assessment have invariably shown that adverse
effects of air pollution on health are substantial.
Measures of containment have produced a reduction of
urban pollution levels, but results of recent studies
continue to emphasize acute and chronic effects on
health, even when these levels are low.
Epidemiological research has consistently documented
a wide range of adverse effects to human health for
exposure to pollutants: it has been documented a wide
range of adverse health outcomes due to short and long
term exposure to air pollutant concentration levels for
urban populations.
Numerous clinical and toxicological studies have
provided significant information about the specific
effects of pollutants and the possible mechanisms of
action these effects have.
General population is daily exposed to pollutants of
various kinds. These pollutants are made up of chemical
and physical (i.e. noise).
Furthermore, the presence of high levels of air pollu-
tion is connected to respiratory symptoms and disease in
various European and non European countries: in the
U.S., the presence of chronic bronchitis was significantly
associated with fine particle pollution [1].
In Italy it was shown that residents in a rural area have
prevalence rates of respiratory symptoms lower than
children who live in urban areas [21,22].
Another important European study has shown, in
adults, an increased risk of developing a framework of
bronchitis resulting from exposure to traffic pollution
from motor vehicles [2]. The respiratory symptoms of 40
- 59 year old women, who spent much of their time at
home, was related to the proximity of their residence to
high motor vehicle traffic areas[15]. Other studies to re-
member in this context are conducted on a population of
at least 10 years in metropolitan areas or rural areas,
where there has been a significant association between
symptoms of chronic obstructive respiratory disease and
high levels of particulates [3].
The purpose of this study was to evaluate spirometric
lung function parameters in the general population ex-
posed to urban pollution and confirm the existence of an

Metanalysis: Respiratory Effects in the General Population Exposed to Urban Pollution975
association between exposure to environmental pollu-
tants and effects from these products and which respira-
tory parameters are associated to urban pollution in gen-
eral population.
2. Materials and Methods
This study has been conducted with a systematic research
of all articles on the assessment of respiratory effects in
the general population exposed to urban pollution,
excluding studies on adolescents and children. The
research included articles from January 2008 (year of
enactment of Presidential Decree 203/88: “Implementa-
tion of directives CEE n. 80/779, 82/884, 84/360 and
85/203 that pertain to air quality directives, relatively to
specific pollutant and the pollution producted by industry,
pursuant to art. 15 of Law of April 16, 1987, number
183”) to May 2009.
We used the following electronic search engines,
available online:
 Biomedcentral
 MEDLINE/ PubMed
 MEDLINE/ National Library of Medicine (NLM)
 MEDLINE Plus
 Nioshtic-2
 Scopus
 TOXNET/Toxline
Furthermore we examined the acts of national con-
gresses organized by S.I.M.L.I.I. (Italian Society of Oc-
cupational Health and Industrial Hygiene) and by
A.I.D.I.I. (Italian Association of Industrial Hygienist)
and many books of Environmental health.
For all search engines we used the following key
words:
 Air pollution (or pollutant) and urban (or rural or
general) population
 Urban pollution (or pollutants) and urban (or rural or
general) population
 Urban air pollution and urban (or rural or general)
population
 Urban atmospheric pollution (or pollutant) and urban
(or rural or general) population
 Ambient air (pollution) and urban (or rural or general)
population
 Ambient exposure and urban (or rural or general)
population
 Environmental exposure and urban (or rural or gen-
eral) population
 Particulate matter (PM) and urban (or rural or general)
population
 Urban particulate matter (UPM) and urban (or rural or
general) population
 Ultrafine particulate matter and urban (or rural or
general) population
 Ultrafine particles (fine particles) and urban (or rural
or general) population
 Concentrated ambient fine particles (CAP) and urban
(or rural or general) population
 Volatile organic compounds (VOCs) and urban (or
rural or general) population
 Suspended particulate matter (SPM) and urban (or
rural or general) population
 Total suspended particulate matter (TSPM) and urban
(or rural or general) population
 Traffic emissions (air pollution) and urban (or rural or
general) population
 Urban traffic and urban (or rural or general) popula-
tion
 Road traffic (pollution) and urban (or rural or general)
population
 High (or heavy) traffic density and urban (or rural or
general) population
Of the 976 publications we found, 85 turned out to be
inherent with the aim of our study and only 22 responded
to the following inclusion criteria:
1) Case-Control studies, studies in which the
experimental group was composed of subjects vulnerable
to urban pollution and the control group was made up of
subjects exposed to a lower degree of urban pollution;
2) Studies that reported results in numerical terms of
media and standard deviation (for the continues variables)
or of frequency (for not continue variables); their main
characteristics are reported in Tables 1-3.
We tried to contact the authors of publications in
which the results were expressed in unvailable numeric
form, to obtain substantial data but did not have any
answer.
3. Description of Participants
In the articles included in our meta-analysis, the exposed
group is represented by general population aged between
15 and 75 years for both gender, resident in most
polluted urban areas, while the control group is re-
presented by general population resident in rural and
suburban areas, where pollution is lower.
The numbers of participants included in this meta-
analysis is 48.848; the number of cases is 22.414 while
the number of controls is 26.434.
In the studies, where is specified, total number of male
subjects in the case group is 10.357 while the number of
female is 10.965. In the studies, where is specified, total
number of male subjects in the control group is 13.457
while the number of female is 12.136.
4. Data Organization
After a careful analysis of selected studies we have
identified the most frequently studied variables on the

Metanalysis: Respiratory Effects in the General Population Exposed to Urban Pollution 976
Table 1. Distribution of studies included in the variables.
Class Variables Authors To
t
Cough
Van der Zee et al. 2000; Bjornsson et al. 1994; Viegi et al. 1991; Viegi et al. 1999; Viegi et al. 2004;
Sunyer et al. 2006; Devereux et al. 1996; Walraven et al. 2001; Kumar et al. 2000;
Sekine et al. 2004; Jedrychowski et al. 1989.
11
Phlegm Van der Zee et al. 2000; Viegi et al. 1991; Viegi et al. 1999; Viegi et al. 2004; Sunyer et al. 2006;
Kumar et al. 2000; Sekine et al. 2004; Jedrychowski et al. 1989. 8
Dyspnea Viegi et al. 1991; Viegi et al. 1999; Viegi et al. 2004; Jedrychowski et al. 1989. 4
Short
breath/breathless
ness
Devereux et al. 1996; Wieringa et al. 1997; Sekine et al. 2004; 3
Prevalence
of respiratory
symptoms
Wheezing
Van der Zee et al. 2000; Bjornsson et al. 1994; Viegi et al. 1991; Viegi et al. 1999;
Devereux et al. 1996; Wieringa et al. 1997; Wieringa et al. 1998; Wieringa et al. 2001;
Walraven et al. 2001; Burr et al. 2004; Sekine et al. 2004; Jedrychowski et al. 1989
12
Fev1 Boezen et al.. 1998; Kumar et al. 2000; Chattopadhyay et al. 2007; Sichletidis et al 2005;
Vanderjagt et al. 2004; Lubinski et al. 2005; Sekine et al. 2004; Heydarpour et al. 2007 8
Fvc Kumar et al. 2000; Chattopadhyay et al. 2007; Sichletidis et al. 2005; Vanderjagt et al. 2004;
Lubinski et al. 2005; Sekine et al. 2004; Heydarpour et al. 2007 7
Fev1/Fvc Chattopadhyay et al. 2007; Sichletidis et al. 2005; Vanderjagt et al. 2004;
Lubinski et al. 2005; Heydarpour et al. 2007 5
PEFR Kumar et al. 2000; Chattopadhyay et al. 2007; Vanderjagt et al. 2004; Lubinski et al. 2005 4
Fef25-75 Chattopadhyay et al. 2007; Sichletidis et al. 2005; Vanderjagt et al.. 2004; Heydarpour et al. 2007; 4
Lung
Function
Fef75-85 Chattopadhyay et al. 2007 1
Chronic Bron-
chitis Viegi et al. 1991; Viegi et al. 1999; Viegi et al. 2004; Kumar et al. 2000 4
Asthma
Van der Zee et al. 2000; Bjornsson et al. 1994; Viegi et al. 1991; Viegi et al. 1999; Viegi et al. 2004;
Wieringa et al. 1997; Wieringa et al.. 1998; Wieringa et al.. 2001; Walraven et al.. 2001;
Burr et al. 2004; Sekine et al. 2004
11
Rinithis Sichletidis et al. 2005; Viegi et al. 1991; Burr et al. 2004; Kumar et al.. 2000 4
Emphisema Viegi et al. 1991; Viegi et al. 1999; Viegi et al. 2004; Wieringa et al. . 2001 4
Prevalence of
respiratory
disease
Drug use for
asthma
Van der Zee et al. 2000; Devereux et al. 1996; Wieringa et al. 1998;
Wieringa et al. 2001; Burr et al. 2004 5
Table 2. Statistical Analysis for variables.
Indici della meta-analisi
Classe Variabile CampioneRisultato
P I2 % ES
Cough GE: 11389
GC: 16009 Increased in the exposed groupZ = 3.556 P = 0.000 72.890 OR 1.277 [1.116; 1.461]
Phlegm GE: 4971
GC: 7837 Increased in the exposed groupZ = 2.030 P = 0.042 66.369 OR 1.239 [1.007; 1.524]
Dyspnea GE: 3499
GC: 5590 NS Z = –0.144 P = 0.885 99.985 OR 0,948 [0.459; 1.959]
Short breath/breathlessness GE: 2834
GC: 3979 Increased in the exposed groupZ = 2.623 P = 0.009 78.948 OR 2.058 [1.200; 3.528]
Prevalence of respiratory
symptoms
Wheezing GE: 16322
GC: 21040 Increased in the exposed groupZ = 4.657 P = 0.000 82.950 OR 1,402 [1.216; 1.617]
FEV1
GE: 2282
GC: 1810 decreased in the exposed groupZ = –2.904 P = 0.004 79.272 SMD –0.282 [–0.472; 0.092]
FVC GE: 2191
GC: 1712 decreased in the exposed groupZ = –4.062 P = 0.000 21.996 WMD –0.139 [–0.206; 0.072]
FEV1/FVC GE: 2033
GC: 1536 NS Z = –1.512 P = 0.131 87.879 SMD –0.230 [–0.528; 0.068]
PEFR GE: 336
GC: 736 decreased in the exposed groupZ = –4.779 P = 0.000 0.000 SMD –0.320 [–0.452; –0.189]
Fef25-75
GE: 1883
GC: 1207 NS Z = –1.644 P = 0.100 26.788 WMD –0.064 [–0.139; 0.012]
Lung Function
Fef75-85
GE: 94
GC: 289 NS Z = –1.673 P = 0.094 46.843 WMD –0.199 –0.433; 0.034]
Chronic Bronchitis GE: 4252
GC: 7602 Increased in the exposed groupZ = 4.147 P = 0.000 52.391 OR 2.256 [1.536; 3.313]
Prevalence of respiratory
disease
Asthma GE: 15643
GC: 21176 Increased in the exposed groupZ = 3.864 P = 0.000 77.540 OR 1.573 [1.250; 1.958]

Metanalysis: Respiratory Effects in the General Population Exposed to Urban Pollution 977
Rinithis GE: 2862
GC: 4630 Increased in the exposed groupZ = 2.123 P = 0.034 97.217 OR 2.824 [1.083; 7.361]
Emphisema GE: 5639
GC: 9390 Increased in the exposed groupZ = 5.057 P = 0.000 78.247 OR 2.976 [1.950; 4.541]
Drug use for asthma GE: 6307
GC: 6903 NS Z = 1.474 P = 0.140 60.016 OR 1.201 [0.941; 1.533]
GE: group of exposed; GC: gruop of control; NS: Not Significant; P: Probability; I2: Inconsistence Index; ES: Effect Size; SMD: Standardized Mean Difference; WMD: Weighted Mean
Difference; OR: Odds Ratio.
Table 3. Statistical Analysis for class.
Indici della meta-analisi
Classe Campione Risultato
P I2 % ES
Prevalence of respiratory symptoms GE: 16,509
GC: 21,319 High in the exposed group Z = 5.26 P = 0.00 85.23 OR 1.30 [1.17; 1.43]
Lung Function GE: 2282
GC: 1810 Low in the exposed group Z = –4.08 P = 0.00 85.58 SMD –0.21 [–0.31; –0.11]
Prevalence of respiratory disease GE: 20,009
GC: 24,419 High in the exposed group Z = 4.89 P = 0.00 92.16 OR 1.66 [1.35; 2.04]
GE: group of exposed; GC: group of controls; P: Probability; I2: Inconsistence Index; ES: Effect Size; SMD: Standardized Mean Difference; OR: Odds Ratio.
assessment of the effects on the respiratory systems and
of the factors related to the onset of lung disease.
The following variables contained data expressed as
means and standard deviations:
 FEV1
 FVC
 PEFR
 FEV1/FVC (Tiffeneau index)
 FEF 25 - 75
 FEF 75 - 85
The following variables gave data expressed in fre-
quency:
 cough
 sputum
 wheezing
 dyspnea
 shortness of breath / breathlessness
 Chronic bronchitis
 Asthma
 emphysema
 use of medications for asthma
5. Statistical Analysis
The Effect Size (ES) is a value that expresses the
magnitude of the association strength between two
variables and was used to express the result of our meta-
analysis.
The confidence interval of the effect size was also
calculated, that expresses the accuracy with which the
effect size was estimated in our study.
In our study the confidence interval corresponds to
95% of the observations, P value was set equal to P <
0.05. The P value that is necessarily correlated to the con-
fidence interval allows to express the significance of the
ES.
When studies reported data expressed as mean and
standard deviation, the ES was expressed in Standardized
Mean Difference or in Weighted Mean Difference de-
pending on the value of the Index of Inconsistency (I2).
The Inconsistency Index was used as a measure of het-
erogeneity. In the systematic review, the heterogeneity
relates to the variability or the difference among the stud-
ies on the evaluation of the effects.
With the I2, we calculated the percentage of variance
due to real heterogeneity rather than to the blind chance.
If the I2 value is near to the zero, the observed variance
is referable to the blind chance while if the I2 value is
high the variance is referable to different factors that
must be better investigated.
The calculation of heterogeneity was used for the
choice of the statistical model to calculate the ES.
In the presence of a high Inconsistency Index (I2 >
50%), the ES was evaluated with the Random Effects
Model (REM) that is a statistical model in which the
confidence interval is influenced by the sampling error
internal to the study and by the variability among the
studies included in the meta-analysis. In this case, the
REM is more robust because it provides wider confi-
dence intervals than those obtained from another model
which the Fixed Effects Model (FEM). The quantifica-
tion of the ES was calculated with the Standardized
Mean Difference (SMD) that shows the relationship be-
tween the difference of two averages and an estimator of
standard deviation inside the group.
Without a high inconsistency between the studies (I2 <
50%), the ES was calculated with the FEM. In this model,
only the variations inside the study can influence the
confidence interval. So, the quantification of the ES is
made with the Weighted Mean Difference (WMD),
which allows to combine the measures of a continue

Metanalysis: Respiratory Effects in the General Population Exposed to Urban Pollution 978
scale when average, standard deviation and numerosity
of the sample are known parameters. The importance that
is given to each study is determined by the precision of
the estimator of the effect provided that all studies have
measured the variable with the same rating scale. A dif-
ference of 0.0 showed lack of difference among studied
groups, for the measures of ES based on the differences
(i.e. SMD and WMD).The ES was expressed in terms of
Odds Ratio (OR), when the studies reported data ex-
pressed in frequency.
As described above, in the presence of a high degree
of heterogeneity (I2 > 50%), the ES was assessed with the
Random Effects Model (REM) while in the absence of
high heterogeneity among studies (I2 < 50 %), the calcu-
lation of the ES was performed with the Fixed Effects
Model (FEM).
A ratio of 1.0 indicates no difference among the stud-
ied groups, for measures of ES based on the reports (i.e.
OR) [4].
The results are been detected on the basis of the activ-
ity of research after a convention between the University
of Rome “Sapienza” (Unit of Occupational Medicine)
and INAIL (National Institute for the Insurance against
the Accident at Work).
6. Results
From the elaboration of the data inherent to each class
we had the following results [1-26]:
 The prevalence of respiratory symptoms, evaluated in
15 studies, on a total sample of 16.509 cases and
21.319 controls, appears significantly higher in the
group of subjects exposed to urban pollution than in
the group of less exposed subjects (OR 1.30 [1.18;
1.43]) the value of heterogeneity among the studies
was I2 85.23.
 The lung function, evaluated in 8 studies, on a total
sample of 2.282 cases and 1.810 controls, appears
significantly lower in the group of less exposed sub-
jects to urban pollution than in the group of less ex-
posed subjects (SMD –0.21 [–0.31; –0.11]) the value
of heterogeneity among the studies was I2 85.58.
 The prevalence of respiratory disease, evaluated in 13
studies, on a total sample of 20.009 cases and 24.419
controls, appears significantly higher in the group of
subjects exposed to urban pollution than in the group
of less exposed subjects (OR 1.66 [1.35; 2.04]) the
value of heterogeneity among the studies was I2
92.16.
The statistical analysis of data expressed as mean and
standard deviation gave the following results (Table 2):
 The average FVC, evaluated in 7 studies, on a total
sample of 2.191 cases and 1.712 controls, appears
significantly lower in the group of subjects exposed to
urban pollution than in the group of less exposed
subjects (WMD –0.139 [–0.206; –0.072]) the value of
heterogeneity among the studies was I2 21.996 (P =
0.000).
 The average FEV1, evaluated in 8 studies, on a total
sample of 2.282 cases and 1.810 controls, appears
significantly lower in the group of subjects exposed to
urban pollution than in the group of less exposed
subjects (SMD –0.282 [–0.472; –0.092]) the value of
heterogeneity among the studies was I2 79.272 (P =
0.004).
 The PEFR average evaluated in 4 studies, on a total
sample of 336 cases and 736 controls, appears sig-
nificantly lower in the group of subjects exposed to
urban pollution than in the group of less exposed
subjects (SMD –0.320 [–0.452; –0.189]) the value of
heterogeneity among the studies was (I2 0.00; P =
0.000).
 For all other evaluated parameters (FEV1/FVC,
FEF25-75, FEF75-85) there were no statistically sig-
nificant differences in the comparison of values found
in the exposed group and in the group of less ex-
posed.
The statistical treatment of data expressed in frequency
gave the following results (Table 2):
 Prevalence of respiratory symptoms: cough (OR
1.277 [1.116 to 1.461]; I2 72.890, P 0.000), phlegm
(OR 1.239 [1.007 to 1.524]; I2 66.369, P 0.042),
wheezing (OR 1.402 [1.216 to 1.617]; I2 82.950, P
0.000), shortness of breath/breathlessness (OR 2.058
[1.200 to 3.528]; I2 78.948, P 0.009), increased sig-
nificantly in the group of subjects exposed to urban
air pollution compared to the group of less exposed;
 Prevalence of respiratory disease: chronic bronchitis
(OR 2.256 [1.536 to 3.313]; I2 52.391, P 0.000),
bronchial asthma (OR 1.573 [1.250 to 1.980]; I2
77.540, P 0.000), rhinitis (OR 2.824 [1.083 to 7.361];
I2 97.217, P 0.034) and emphysema (OR 2.976 [1.954
to 4.541]; I2 78.247, P 0.000) increased significantly
in the group of subjects exposed to urban air pollution
compared with subjects less exposed.
As to the other parameters no statistically significant
differences appeared in the comparison of the frequen-
cies found in the two groups.
7. Discussion
The results of our meta-analysis allow to confirm the
evidence of the effects of urban pollution on the respira-
tory system, although the mechanisms of action have
been clarified only in part (Committee the Environmental
and Occupational Health Assembly of the American
Thoracic Society 1996).
The effects of pollutants on the respiratory system de-

Metanalysis: Respiratory Effects in the General Population Exposed to Urban Pollution979
pend on the type of pollutant, its concentration in the
environment, on the duration of exposure and ventilatory
capacity [11].
Our results in line with other studies in the scientific
literature support the hypothesis that the reduction of
some parameters of lung function such as FVC, FEV1
and PEFR found in the general population living in urban
areas, or in areas with high pollution, could be due to
exposure to urban pollutants and depict a framework of
obstructive syndrome [12].
In one study [5], conducted in the USA, there was a
significant association between lung function and levels
of suspended particles in the non-smoking adults exam-
ined (NHANES I). The study showed that the increase of
particulate was associated with a decrease of FVC: this
association ceased approximately below 60 μg/m3 of
particulate [10].
A reduction of respiratory capacity (FVC and FEV1)
is also observed in the study of Pope III et al. 1993: in
particular a decrease of 2% of FEV 1 for rise of PM10 of
100 g/m3 in the subjects examined resulted statistically
significant, all the subjects were smokers with mild or
moderate chronic obstructive lung disease [13].
Another study [7] that must be remembered was made
in Cracovia on 1414 persons who hadn’t changed resi-
dence in the last 8 years: a faster decrease of respiratory
function was observed in persons living in an areas with
SO2 and PM10 pollution compared people living in other
areas.
An association between previous chronic exposition to
high levels of air pollution and respiratory function was
found in non-smokers living in 2 areas characterized by
different levels of pollution [16,17].
In an Italian study among subjects with BPCO and
asthma, the results of the analysis show that an increase
of environmental concentrations of PM10 and PM2,5
causes a decrease of respiratory function during the fol-
lowing 24 h - 48 h [18-20].
A Dutch study shows a reverse correlation between
FEV1 and nearness to a very busy freeway or between
FEV1 and the number of heavy vehicles in a day [8].
The availability of controlled studies in the literature is
rather small but the number of subjects studied is quite
high. Many studies [22-24] show a disparity between the
number of those who constitute the experimental group
and the size of the control group with the resulting dis-
tortion of the results.
However, the processing of the data available, grouped
by the three classes, allowed us to demonstrate an im-
pairment of the respiratory system characterized by:
1) reduction in lung function (I2 98.23);
2) increased prevalence of the class of symptoms (I2
55.65);
3) increase in respiratory disease (I2 51.31).
Among the class of respiratory symptoms, the results
on the short breath/breathlessness and wheezing were the
most sensitive.
With an ES of 2.06 and 1.40 respectively, the meta-
analysis indicates that within the population most ex-
posed, shortness of breath/breathlessness and wheezing
were observed more frequently than in individuals be-
longing to the group of less exposed.
Studies concerning the variable shortness of breath/
breathlessness and wheezing, show a low homogeneity
represented by their high value of I2 (respectively 78.95
and 82.95) [25].
Among respiratory disease, variables with a high sen-
sitivity that can be attributed to the effects of pollution
include chronic bronchitis, emphysema with an ES of
2.25 and 2.97 respectively.
The heterogeneity among the studies which analysed
for the presence of chronic bronchitis is 52.39 instead of
78.24 for the variable emphysema [9]. Among the statis-
tically significant results related to lung function the pa-
rameters FVC, FEV1 and PEFR are all reduced, indicat-
ing obstructive deficit as chronic effect in the exposed
population. The ES of the FVC and FEV1 PEFR is re-
spectively –0.14 and –0.28 –0.32 while the value of I2 is
respectively 21.99, 79.27 and zero.
The meta-analysis identified the variables that can be
used as indicators of the effects of pollution on the respi-
ratory system. Variables with low heterogeneity and high
sensitivity as the PEFR and bronchitis may be considered
useful indicators of exposure to urban pollutants [26].
The variables with high sensitivity and high heteroge-
neity such as emphysema and shortness of breath/
breathlessness should be further explored in future stud-
ies to verify their usefulness as indicators of exposure to
urban pollution.
8. Conclusions
In the light of the results is clear that the health of the
population exposed to urban pollution must necessarily
include a careful evaluation of the respiratory system
through targeted surveys to the variables mentioned
above with high sensitivity.
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