Open Journal of Respiratory Diseases, 2013, 3, 13-20
http://dx.doi.org/10.4236/ojrd.2013.31003 Published Online February 2013 (http://www.scirp.org/journal/ojrd)
Bronchospasm Diagnosis in Motorcycle Taxi Drivers
Exposed to Automotive Pollutants in Porto-Novo*
Folly Messan1#, Mohamed Lawani2, Barnabé Akplogan2, Pierre Dansou1,
Daouda Mama3, Rodrigue Hounkponou1, Rodrigue A. Dagnitché1
1Laboratory of PSA and Motricity, National Institute of Youth,
Physical Education and Sport (INJEPS), University of Abomey-Calavi, Cotonou, Republic of Benin
2Laboratory of Biomechanics and Performance (LABIOP), National Institute of Youth,
Physical Education and Sport (INJEPS), University of Abomey-Calavi, Cotonou, Republic of Benin
3Laboratory of Applied Hydrology, Faculty of Sciences and Technics,
University of Abomey-Calavi, Cotonou, Republic of Benin
Received October 26, 2012; revised November 28, 2012; accepted December 5, 2012
ABSTRACT
Background: In African cities, chronic exposure to pollutants is the most common public health problem faced daily
by motorcycle taxi drivers. In Benin, studies conducted on motorcycle drivers, have shown the presence of nitrogen
oxides, carbon monoxide, sulfur dioxide, volatile organic compounds and particulate matter in ambient air, which may
affect lung function. Aims: This study aims to diagnose potential respiratory problems among 48 motorcycle taxi dri-
vers (47.02 ± 8.75 years) compared to a control group made up of 52 people (46.38 ± 8.81 years) in Porto-Novo, Benin.
Methods: A questionnaire, two exploration pulmonary function tests and two 6-minute walk tests were used to identify
symptoms and changes in respiratory variables that reveal the existence of bronchospasm. Results: The frequency of
respiratory symptoms noted among motorcycle taxi drivers is higher than that recorded among members of the control
group. We observed that motorcycle drivers at rest and after physical effort have significantly lower respiratory vari-
ables (FVC, FEV1, PEF, FEF25-75, FEF50 and FEF25) (p < 0.05) than those recoded in control group. Conclusion: It can
therefore be concluded that, because of the relatively long duration of exposure among motorcycle taxi drivers, the in-
halation of automobile pollutants, may cause respiratory problems in this population.
Keywords: Automobile Pollution; Asthma; Bronchospasm; Urban Pollution; Motorcycle-Taxi Drivers; Benin
1. Introduction
The socioeconomic status of West African countries has
not improved despite the implementation of the Millen-
nium Development Objectives in 2000, which aim to
reduce extreme poverty and hunger, improve health and
ensure environmental sustainability by 2015. With less
than five years left to meet these goals, it is clear that
problems still remain, including relatively low rates of
children enrolled in school, high poverty rates and high
levels of environmental pollution generated by urban
transport in African capital cities. Indeed, urban popula-
tion growth, migration of young people from villages to
cities, massive layoffs of civil servants resulting from the
structural adjustment programs imposed by the Bretton
Woods Institutions in the 1980s and the devaluation of
the currency of the African Financial Community (CFA)
in 1994, have resulted in a high rate of unemployment in
West African countries in general and in Benin in par-
ticular. This crisis is most acutely felt in Benin’s major
cities, such as Cotonou and Porto-Novo where low in-
comes and the lack of transportation policy governing
urban public transportation have given rise to informal
transportation activity led by motorcycle taxi drivers.
These motorcycles imported from Europe are locally
called “Zémidjan” and 95% of them have used engines
that emit thick black smoke into the atmosphere, particu-
larly at intersections during peak traffic hours. The fumes
are generated by incomplete combustion of hydrocarbons
and other particles due to mechanical failures of the
automobiles poorly maintained motors and the poor
quality of fuel illegally imported from neighboring, Ni-
geria. These motorcycles contribute to the degradation
and pollution of the environment, causing health prob-
lems among the general population and among profess-
sional motorcycle taxi drivers in particular. A study con-
ducted on samples of urine and blood collected from
motorcycle taxi drivers in Cotonou showed high levels of
benzene and ultrafine particles which are likely to dam-
age the deoxyribonucleic acid (DNA) [1-3]. Another
*The authors declare no conflict of interest.
#Corresponding author.
C
opyright © 2013 SciRes. OJRD

F. MESSAN ET AL.
14
cross-sectional study conducted among 400 motorcycle
taxi drivers, after analysis of the ambient air collected at
intersections and motorcycle taxi parks, showed peak
concentrations of carbon monoxide of 38.6 ppm (parts
per million) in the morning and 78.6 ppm in the after-
noon compared to the standard level of 30 ppm with lev-
els of benzene at 7.2 μg/m3 [3]. Motorcycle taxi drivers
usually work in urban sub-Saharan Africa where the
weather is hot with, high ambient temperatures. As a re-
sult, pollutants emitted by motors exposed to solar ultra-
violet radiation form ozone (O3), when a molecule of
nitrogen dioxide oxygen is combined with oxygen in the
atmosphere (O2) to form ozone (O3). Ozone, an atmos-
pheric gas, irritates the mucous membranes of the nose,
throat, and bronchi may even cause a decrease in lung
function. It is therefore likely that drivers who are chro-
nically exposed to ozone and automotive pollutants may,
in the medium- or long-term, become victims of respira-
tory diseases, including bronchospasm, which character-
ized by paroxysmal respiratory problems and sibilants.
Similarly, research carried out in Benin using self-report
questionnaires distributed to motorcycle taxi drivers,
showed that 23% of the drivers had difficulty breathing
[3]. However, the questionnaire based only on clinical
symptoms, seems unreliable to assess bronchospasm. In
this sense, the work of Thole [4], Rundell [5] and, more
recently Bougault [6] has shown that the existence of cli-
nical symptoms is not necessarily a sign of airway hyper-
responsiveness as clinical symptoms do not always co-
exist with bronchospasm. It therefore seems necessary
that the self-report questionnaires distributed to study
groups to assess the existence of symptoms of broncho-
spasm be supplemented by a lung function test. To the
best of our knowledge, this approach to diagnosing bron-
chospasm has not yet been used among the motorcycle
taxi drivers population. Therefore, the present work, the
first of its kind, conducted in the city of Porto-Novo,
Benin, seeks to explore the pulmonary function of mo-
torcycle taxi drivers and the subjects of an equivalent
control group for those who experienced: 1) clinical dis-
orders; 2) changes in lung volumes and flow rates; 3)
prevalence values indicating bronchospasm.
2. Materials and Methods
2.1. Type and Scope of the Study
This is an analytical and experimental study carried out
from 2 to 30 July 2011 on motorcycle taxi drivers resid-
ing in the city of Porto-Novo, the political capital city of
Benin in West Africa. In this city, intra-urban transport is
provided exclusively by motorcycle taxi drivers who
carry their clients on the back seats of two-wheeled mo-
torcycles, a type of informal public transport commonly
called “Zémidjan”. The data on this occupation were
obtained from officials of the professional association of
motorcycle taxi drivers based in Porto Novo. Car taxis
are almost nonexistent in the capital city. Markets, parks,
intersections and traffic lights have become major places
of concentration for motorcycle taxi drivers.
2.2. Subject of the Study
The study sample consists of 48 professional motorcycle
taxi drivers and 52 control subjects selected by a simple
random probability method. All subjects were male and
their mean (±SD) age, height, weight and body mass in-
dex were respectively 47.02 ± 8.75 yr, 170 ± 0.06 cm,
72.70 ± 13.30 kg, and 25.34 ± 3.71 kg/m2 for profess-
sional motorcycle taxi drivers and were respectively
46.38 ± 8.81 yr, 171 ± 0.06 cm, 72.42 ± 13.01 kg and
26.81 ± 3.91 kg/m2 for control group. A physical exami-
nation was used to ensure that each participant was in
good health. Subjects are selected among motorcycle taxi
drivers who are members of the Association that mana-
ges the profession. Subjects in the control group were se-
lected from among those who engage in physical exer-
cise on weekend mornings and who are members of the
Association which organizes this activity. Therefore, the
experimental group consists of professional motorcycle
taxi drivers and the control group is composed of people
who occasionally practice sports for health maintenance.
The study did not expose individuals to health risk, but in
case of discovery of unknown respiratory impairment,
the individual was referred to a specialist for consultation
and monitoring.
2.3. Sampling
The study sample consisted of two subject groups, mo-
torcycle taxi drivers and a control group from the town of
Porto-Novo and its surroundings. The work of Fourn and
Fayomi that conducted in Cotonou showed clinical signs
of asthma in 50 motorcycle taxi drivers [3]. Generally,
the size of the study population when it is estimated at
less than 10,000 individuals is calculated by the Margaret
Formula (1) [7]:


1nfnn N (1)
In this formula, n refers to the size of the study sample
and N to the size of the estimated population.
The formula for n is the following (2):


²nZPqd ² (2)
In this formula, n = Number of necessary subjects, Z =
Interval of trust at 95% (Z = 1.96), P = the theoretical
proportion of groups of people likely to show signs of
bronchospasm in a normal population, and q = 1 − P and
refers to the level of trust usually set at 5%. According to
the data currently available, the proportion (P) is 15%.
Thus,

F. MESSAN ET AL. 15
 
2
1.960.15 0.850.05n 

2
(3)
then,



1961196 250nf 

(4)
Thus, according to this formula (3), the total sample
size should be at least 100 individuals.
2.4. Selection Criteria
2.4.1. Inclusion Criteria
Individuals meeting the following criteria are included in
the study: 1) male; 2) from the Department of Oueme; 3)
at least 30 years old and a resident of Porto-Novo; 4)
provision of the signed informed consent form to parti-
cipate in the study; 5) own a private motorcycle; 6) hold-
ing a membership card of the association of sports practi-
tioners or of motorcycle taxi drivers for at least five years,
and 7) having at least five years of experience as motor-
cycle drivers in Porto-Novo.
2.4.2. Exclusion Criteria
Individuals meeting the following criteria are not includ-
ed in the study 1) being a victim of myocardial infarction
during the previous month; 2) having a resting heart rate
greater than or equal to 120 bpm; 3) being a cigarette
smoker 4) suffering from asthma or tuberculosis; 5) hav-
ing a clinical history of rheumatism or orthopedic symp-
toms that obstruct the completion of a 6-minute walk test;
6) conducting imperfect maneuvers during respiratory
exploration tests; 7) practicing intense sports activities in
addition to motorcycle riding, or 8) refusing to sign the
informed consent form.
2.4.3. Materia l s and Techniques
Both groups were questioned using a respiratory ques-
tionnaire based on that used by the American Thoracic
Society (ATS), and also including questions about previ-
ously established clinical disorders (e.g., headache and/
or insomnia, conjunctival hyperemia and breathing dis-
orders) [8]. The closed-answer questions most often had
dichotomous responses and were translated into the local
language goun when necessary. Fact sheets were used to
collect information from members of both groups, on age,
history of diseases and monthly frequencies of motorcy-
cle taxi use. A SECA brand human weighing machine,
accurate to approximately 500 g with a maximum range
of 150 kg, used to determine the body weight of each
subject. A wall gauge measuring from zero to two meters
was used to measure the height of the subjects standing
barefoot and upright, with the head positioned in the ho-
rizontal plane of Frankfort [9]. The body mass index
(BMI = weight on the square of height (kg·m−2)) was
calculated. A trail of 30 linear meters delineated by studs
placed at each distance of one meter was used to conduct
the 6-minute walk tests (6-MWT) as recommended by
the ATS [8]. A double decameter calibrated in centime-
ters with a digital display and a Run Tech measuring tape
stopwatch, accurate to one hundredth of a second, were
used to measure the length of the track and the duration
of walking tests. A Run Tech heart rate monitor model
20,488 was used to record the individuals’ heart rates at
rest and after physical exercise. Mouthpieces and dis-
posable antibacterial filters (Cosmed Ltd., Rome, Italy)
were used to avoid cross contamination between patients.
Pulmonary function tests were performed using the Mi-
cro quark spirometer (Cosmed Ltd, Rome, Italy). At the
beginning of each day of operation, the spirometer is ca-
librated using a calibration syringe (Cosmed Ltd, Rome,
Italy) with a capacity of 3 liters of atmospheric air. In the
evaluation of the individuals’ pulmonary function, the
Micro Spirometer Quark displays the flow volume curve
in real-time on the monitor. The flow emitted varies from
0.03 to 20 L/s and with maximum volume of 10 L, with
an accuracy of plus or minus 3%, as recommended by the
European Respiratory Society [10] and the American Tho-
racic Society [8]. The Micro Quark equipped with a tur-
bine vane sensor works as follows: a light is flashed and
is continuously recorded by a photoelectric cell. The ro-
tating impeller with vanes blocks the light path and chan-
ges the electrical collection, depending on the speed of
movements induced by the volume of air exhaled by the
individual. The interruption of the beam depends on the
speed of the air passing through the initial deflector. The
electrical impulses are recorded by a tachometer.
2.4.4. Experimental Protocol
2.4.4.1. Experimentation Plan
In the first phase of experimentation, the motorcycle taxi
drivers and the selected members of the control group
filled out the individual information sheets and informed
consent forms. The BMI and height of the individuals
were measured. In the second phase, the subject, sitting
in a chair, observes15 minutes of passive rest after which
the following measurements are taken: heart rate while
sitting, lung volumes and flow rates while standing. After
a 10 minutes passive break, the subject performs the first
6-minute walk test (6-MWT1) followed by 10 minutes of
rest, then a second walk test (6-MWT2). At the end of the
6-MWT2, the heart rate is immediately measured while
the measurement of respiratory variables is performed
after a 10-minute break.
2.4.4.2. Pulmonary Function Tests
The pulmonary function tests (PFT) were performed un-
der the supervision of a medical technician. After deter-
mining the size, body weight, age, sex and race of the in-
dividual, the spirometer unit automatically calculates the

F. MESSAN ET AL.
16
theoretical values of each respiratory parameter. In the
PFT, the individual, while standing with nose pinched
and a turbine between their two hands breathed naturally
and quietly through the mouthpiece connected to the spi-
rometer. The individual was then instructed to inflate his
lungs, and then breathe the air as quickly as possible, in a
continuous and complete way. After the test, the best test
was selected among the three reproducible tests that have
been validated according to the algorithms of the spiro-
meter. The lung volumes and peak flows were recorded.
2.4.4.3. Six-Minute Walk Test (6-MWT)
This test was carried out according to the protocol sug-
gested by the ATS [8]. Subjects are asked to keep a run-
ning speed as regular as possible and travel the greatest
distance possible in six minutes, running back and forth
between two 30-meter markers. All individuals perfor-
med the 6-MWT without encouragement and under the
supervision of three sports instructors. Because of possi-
ble influences that may induce biorhythms that impact
performance, all six-minute walk tests were conducted in
the morning between 7:30 and 9:30 am, and food intake
was not allowed before or during that time-frame. The
Intensive Care Unit of Porto Novo Central Hospital was
informed of the experiment to prepare for any eventuality.
This study was approved by the Scientific Committee of
Science and the Technology Sector of the Sports and Phy-
sical Activities Department (CSS/sport science), Abomey-
Calavi University, in accordance with the Helsinki Act of
1975 on ethics.
2.4.5. Variables S tudied
2.4.5.1. Variables Measured at Rest before the 6-MWT
The forced vital capacity (FVC), the forced expiratory
volume in one second (FEV1), the peak expiratory flow
(PEF), the forced expiratory flow from 25% - 75% of the
vital capacity (FEF25-75), the forced expiratory flow from
50% of the vital capacity (FEF50) and the forced expira-
tory flow from 25% of the vital capacity (FEF25) ob-
tained from respiratory exploration are used as respira-
tory variables. The theoretical maximum heart rate (pre-
dicted HRmax) equal to the individual’s age subtracted
from 220 (220-age), was observed while all subjects were
at rest. These variables, noted for both groups of indi-
viduals prior to completion of 6-MWT1, were considered
to be resting values. Comparison of respiratory variables
of the group of motorcycle taxi drivers with those of the
control group was used to assess the risk from inhalation
of exhaust gases from vehicles.
2.4.5.2. Variables Measured after the 6-MWT
The maximum heart rates (HRmax) noted at the end of
6-MWT were expressed as percentage change compared
to the predicted HRmax, as assessed at the end of the ex-
periment, in addition to the level of intensity of the exer-
cise test reached by the subjects.
These parameters were calculated using the following
formula.


max maxmax
HR%HR100Predicted HR (5)
The best variables recorded at the end of 6-MWT were
considered post-exercise values. At the end of 6-MWT,
the six-minute walking distance (6-MWD) was calcu-
lated following formula.

 
6-MWD m
Number of round trips60 mfinal meters
(6)
At the end of 6-MWT, the comparison of respiratory
variables in the experimental group with the control
group was used to evaluate the variation of these para-
meters. The diagnosis of bronchospasm was said to be
positive in a subject if his post-FEV dropped at least 10%
compared with the value at rest as calculated using the
formula.


 
FEV %
FEV post exercise100FEV pre exercise100

 
total riding time of 8 hours minimum and 12 hours maxi-
(7)
2.4.6. Statistical Analysis
The variables were processed using StatView 5 software
(version 5) (Abacus Concepts Inc. Berkeley, CA, USA).
Descriptive statistics were generated for each variable.
The normal distribution of variables, as well as the equi-
valence of their respective variances, was checked by the
Kolmogorov-Smirnov test and the F-test. Comparisons
between groups were performed by unpaired t-tests after
the normality of the distribution and homogeneity of va-
riances were verified. For all statistical analyses, the null
hypothesis was rejected at a probability of P < 0.05.
3. Results
Table 1 shows the comparison of biometric parameters
and distances between motorcycle taxi drivers and me-
mbers of control group. The differences were not signifi-
cant (p > 0.05). In contrast, the percentage of predicted
HRmax of motorcycle taxi drivers was significantly (p <
0.001) lower than the control group (Table 1). Symptoms
recorded during the self-reported questionnaires among
motorcycle taxis drivers, were related to clinical disor-
ders (headache and/or insomnia) in 30% of cases, con-
junctival hyperemia (25%), digestive disorders such as
nausea and vomiting (26%), and respiratory disorders
and persistent bronchorrhea (20%). In the control group,
the same disorders were noted with lower frequencies:
headache (18.5%), conjunctival hyperemia (13%), and
headache (16%). The included motorcycle drivers had a

F. MESSAN ET AL. 17
Table 1. Comparisons of biometric, distances traveled and
heart rates betw een motorcycle taxi drivers group and con-
trol group.
Parameters Motorcycle taxi
dri 8) Control Group (n = 52) vers Group (n = 4
Mean ± SD Mean ± SD
Age ears)
7 7
6 6
H
(y47.02 ± 8.75 46.38 ± 8.81
Height (m) 1.70 ± 0.06 1.71 ± 0.06
Weight (kg) 2.70 ± 13.30 2.42 ± 13.01
BMI (kg·m−2) 25.34 ± 3.71 26.81 ± 3.91
6-MWD (m) 15.63 ± 65.15 37.05 ± 79.88
Rmax (%) Pred52.36 ± 9.80*** 66.00 ± 9.58
SDn; HRteax; Pred:WD:
um per day whereas the control subjects were exposed
at, at
re
ts were noted after the physical exercise
of
4. Discussion
tudy was to test lung function and to
y Motorcycle taxi
dri8) Control Group (n = 52)
: Standard deviatiomax: Heart Ra m Predicted; 6-M
6-Minute Walking Distance; BMI: Body Mass Index; ***p < 0.001
m
to pollution in traffic for one to two hours per day.
Among motorcycle taxi drivers, Table 2 shows th
st and before physical exercise, respiratory variables
were significantly (p < 0.01) lower than those of the con-
trol group.
The same resul
6MWT (Table 3). A drop of at least 10% in FEV post
exercise was observed in 15 motorcycle taxi drivers out
of a total of 48, with an average drop in FEV by 19.17%
(10.04% 37.04%), which is a prevalence of bronchospa-
sm of 31.07%. In the control group, this criterion was
found in 12 subjects out of a total of 52, with an average
drop of 17.36% in FEV (10.08% 37.41%), which is a
prevalence of 23.07%.
The aim of this s
determine the prevalence of bronchospasm among mo-
torcycle taxi drivers working in urban areas of Porto-
Novo. Cross-sectional studies previously conducted in
Benin showed that in urban environments where informal
public transport activities are carried out, the environ-
ment is highly polluted [1-3]. Indeed, urban pollution is
the result of pollutants emissions from various sources,
including traffic and industrial activities within cities. The
most prevalent pollutants generated from road transport
are nitrogen oxides (NO and NO2), carbon monoxide (CO),
sulfur dioxide (SO2), volatile organic compounds and par-
ticulate matter [11]. In addition, ozone is a common pol-
lutant formed by a photochemical reaction, resulting from
the sufficient duration of sunlight in Porto-Novo at high
ambient temperatures. Similarly, some particles are
emitted directly or formed by reaction between gases and
particles. The analysis of ambient air in these cities of
Benin reveals a concentration of carbon monoxide rang-
Table 2. Comparisons of respiratory variables between
Motorcycle taxi drivers group and Control group before
6-MWT.
Respirator
variables vers Group (n = 4
Mean ± SD Mean ± SD
FVC (L)
F
)
2.97 ± 0.68** 3.43 ± 0.67
FEV1 (L) 2.00 ± 0.55** 2.42 ± 0.49
PEF (L·s−1) 2.82 ± 1.04** 3.84 ± 1.47
EF25-75 (L·s−1)1.76 ± 0.62*** 2.33 ± 0.66
FEF50 (L·s−1 2.06 ± 0.73** 2.69 ± 0.87
FEF25 (L·s−1) 1.02 ± 0.39** 1.35 ± 0.45
SDation; FVcapacity; FE-
able 3. Comparisons of respiratory variables between Mo-
iratory Motorcycle taxi
dri 8)
Control Group
: Standard deviC: forced vital V1: forced expira
tory volume in one second; PEF: peak expiratory flow; FEF25-75: expiratory
flow from 25% - 75% of the vital capacity; FEF25, FEF50: instantaneous
expiratory flows at 25% and 50% respectively; **p < 0.01; ***p < 0.001.
T
torcycle taxi drivers group and Control group after 6-
MWT.
Resp
variables vers Group (n = 4(n = 52)
Mean ± SD M ean ± SD
FVC (L)
F
50 )
3.06 ± 0.70** 3.45 ± 0.66
FEV1 (L) 1.95 ± 0.54*** 2.46 ± 0.48
PEF (L·s−1) 2.66 ± 0.92*** 3.89 ± 1.63
EF25-75 (L·s−1)1.71 ± 0.60*** 2.28 ± 0.72
FEF (L·s−12.03 ± 0.72** 2.61 ± 1.01
FEF25 (L·s−1) 0.98 ± 0.40** 1.30 ± 0.41
SD:tion; FVCapacity; FE-
g between 26 to 38.6 ppm in the morning and 58 to 78.6
Standard devia: forced vital cV1: forced expira
tory volume in one second; PEF: peak expiratory flow; FEF25-75: expiratory
flow from 25% - 75% of the vital capacity; FEF25, FEF50: instantaneous
expiratory flows at 25% and 50% respectively; **p < 0.01; ***p < 0.001.
in
ppm in the afternoon against a 30 ppm [3]. Likewise, ben-
zene was identified with an average value of 7.2 µg/m3.
On the basis of a self-report questionnaire that reveals
respiratory disorders in the motorcycle taxi drivers, this
study suggest that this bronchopulmonary infection could
be caused by automobile pollution. To assess possible
influences of the ambient polluted air on the lung func-
tion of motorcycle taxi drivers and control group residing
in Porto-Novo, respiratory variables were carefully mea-
sured in the resting state during pulmonary function test-
ing. In addition, the individuals were subjected to a stress
test because the bronchospasm is recognized as being a
latent respiratory disease. The physical characteristics of
individuals such as height, body mass and age, that may
affect the respiratory variables were compared between

F. MESSAN ET AL.
18
the group of motorcycle taxi drivers and the control
group. These comparisons showed no significant diffe-
rence between the two groups (p > 0.05), thereby ensur-
ing their comparability for the purposes of this study.
Variables observed in motorcycle taxi drivers were as-
sessed with reference to the control group. The main re-
sults noted in this study were as follows: 1) the frequen-
cies of symptoms observed among motorcycle taxi driv-
ers are higher than those recorded in the control group; 2)
the motorcycle taxi drivers experienced, at rest and after
exercise testing, peak flow volumes and lung capacity
that were significantly lower (p < 0.01) than in the indi-
viduals of the control group and; 3) the group of motor-
cycle taxi drivers presented a prevalence of 31.25% of
bronchospasm, which exceeds the 8.18% prevalence pre-
sented in the control group. However, proportions in the
control group did not differ significantly (p > 0.05). The
high frequency of symptoms, respiratory depression va-
riables and high values of prevalence of bronchospasm
observed in motorcycle taxi drivers compared to the con-
trol group may be due to exhaust gas poisoning. Indeed,
inhalation of oxidants such as NO2 generated by road tra-
ffic can degrade cell membranes constituents through the
toxic peroxides [12]. Experimental studies conducted on
animals show a reactivity of NO2 with the airway epithe-
lium and thickening of small airways, accompanied by a
proliferation of connective tissue around the bronchus
[13]. Another study on rats showed a decrease in to the
cilia of respiratory epithelia that play an essential role in
removing particles reaching the bronchi and bronchioles
[14]. Moreover, the toxic effects induced by NO2 gener-
ally observed on the respiratory mucosa, may range from
irritation to asthma attacks, following a bronchial reac-
tivity with cough [15]. An irritating effect on the ocular
membranes mucous (conjunctiva) and a decreased resis-
tance to pathogens were also noted [16]. SO2, a very so-
luble irritant, also acts synergistically with other sub-
stances, including particulate matter. The SO2 inhaled is
retained by the watery surfaces of the nose and upper
respiratory tract thereby causing eye irritation, skin and
respiratory infection. Exposure to SO2 increases the inci-
dence of chronic bronchitis and pharyngitis. Indeed, epi-
demiological studies show that exposure to sulfur dioxide
(SO2) at a concentration of approximately 1000 µg/m3
may cause or exacerbate latent respiratory infections and
result in increased mortality caused by respiratory or car-
diovascular disease [17]. Similarly, the work of Bruske-
Hohlfeld [18] showed that an increased level of air pollu-
tion consisting of fine particles, especially from vehicle
emissions, may lead to respiratory problems. In addition,
the high production of particles, carbon monoxide (CO),
lies in the anoxia-induced conversion of hemoglobin to
car- boxyhemoglobin while that of nitrogen dioxide (NO2)
and suspended ultrafine particles are involved in airway
dysfunction [19-21]. From the measurement of lung fun-
ction performed on children living in Los Angeles [22]
and China [23], the effect of ozone on respiratory vari-
ables has been highlighted. Indeed, some respiratory pa-
rameters such as FEV1, FEF25-75 and FVC were ob-
served to decrease over a period of monitoring from 1984
to 1987 [22]. Our results confirm those of Cakmak [24],
which conclude that chronic exposure to high concentra-
tions of polluted air causes a reduction in lung function.
Under these conditions, how can we explain differences
in the frequency of symptoms, respiratory variables and
values of bronchospasm prevalence noted among motor-
cycle taxi drivers and the control group? As part of their
profession, the motorcycle taxi drivers are exposed daily
to automotive pollutants for 8 hours minimum and some-
times as many as 10 to 12 hours, compared with control
subjects who are exposed to automotive pollutants one to
two hours per day because of their daily activities. Be-
cause individuals in both groups were not subjected to
the same level and duration of exposure to automotive
pollutants, it can be assumed that this fact can explain the
differences noted in frequency of symptoms, as well as
differences in recorded ventilatory parameters observed
at rest. Indeed, motorcycle taxi drivers at rest showed a
significant reduction in lung function compared with the
control group (Tab le 2 ). The diagnosis of lung function
sometimes requires the use of exercise testing which may
reveal latent or overt bronchospasm. Indeed, during phy-
sical exercise, the airways are exposed to progressively
hyper osmolarity. This dehydrating mechanism leads to
an increase in the concentrations of Ca2+, K+, Cl− and Na+.
As a result, the inflammatory mediators are released and
induce airway contraction [25,26]. As part of the study
and after the 6-minute walk test, motorcycle taxi drivers
showed respiratory variables significantly lower than
those noted in individuals of the control group (Table 3).
Can physical exercise, with its implications in the occur-
rence of bronchospasm, explain the observed differences
in respiratory variables? The change in respiratory pa-
rameters noted at the end of the 6-minute walk test has
several explanations. In fact, the 6-minute walk test is a
sub maximal exercise, classically tailored to elderly pa-
tients, as recommended by the ATS [8]. The heart rates
observed after the exercise test confirm that the 6-minute
walk test is actually sub maximal because they corre-
spond to 52.36% and 66% of predicted HRmax in motor-
cycle taxi drivers and the control group respectively. In
addition, variables observed at rest and after physical
exercise did not differ significantly between the two
groups. Motorcycle taxi drivers seem to be more physi-
cally fit and able than the control group because at the
end of the effort, the average HRmax recorded among
motorcycle taxi drivers (52.36 ± 9.80%) is significantly
(p < 0.01) lower than that of control subjects (66% ±

F. MESSAN ET AL. 19
9.58%). The fact remains, however, that the comparison
of the distances traveled by the two groups was not sig-
nificantly different (p > 0.05) (Table 1). Furthermore, the
fact that motorcycle taxis drivers ventilate polluted air
for many hours and the corresponding risk of contact
between the bronchial mucosa and allergens in the air
could increase their sensitivity [27,28]. Indeed, in the
event of a hypersensitivity to these allergens, the IgE-de-
pendent mechanism would become active, stimulate mast
cell membrane and facilitate the penetration of calcium
into the cell nucleus. Under these conditions, the mast
cells would degranulate the inflammatory mediators which
may also induce contraction of smooth muscles of the
airways. The findings of previous studies, in the studies
[29,30] also point to a link between exposure to gases
emitted by traffic and respiratory infection, including
bronchospasm. Therefore, the quality of ambient air in-
haled at rest as well as during physical exercise appears
to be a key factor that can lead to bronchospasm, the pre-
valence of which can be determined from comparing
FEV at rest and after exerting effort. The prevalence of
bronchospasm observed in the control group (23.07%) is
higher than that reported in the general population which
ranges from 4% to 20% [31-33]. In addition, at the end of
the 6-MWT, the prevalence of bronchospasm among mo-
torcycle taxi drivers (31.25%) is higher than that obser-
ved among basketball players in Benin (26%) [34]. Chro-
nic exposure of the general population and of the motor-
cycle taxi drivers to traffic pollution has emerged as a pu-
blic health problem whose consequences still raise health
concerns. Thus, studies showing links between exposure
to pollution from nearby urban areas and respiratory di-
seases are not unanimous in their findings. Therefore, the
knowledge of environmental conditions and their impact
on human health require an interdisciplinary approach.
5. Conclusion
ies previously conducted in Benin on
6. Acknowledgements
professional motorcycle
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