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2. Service de Pneumologie, Centre Hospitalier Universitaire de Fann, Faculté de Médecine, de Pharmacie et d’Odontologie (FMPO), BP : 5035 Dakar-Fann, Sénégal.
3. Department des sciences physico-chimiques, Unité d’Enseignement et Recherche, Université Iba Der Thiam, BP : A967 Grand Standing, Thiès, Sénégal.
4. Institut de Santé et de Développement (ISED), Département de Médecine, Faculté de Médecine, de Pharmacie et d’Odontologie (FMPO), Université Cheikh Anta Diop, BP : 5005 Dakar-Fann, Sénégal.
5. Laboratoire de Physiologie et d’Exploration Fonctionnelle, Département de Médecine, Faculté de Médecine, de Pharmacie et d’Odontologie (FMPO), Université Cheikh Anta Diop, BP : 5005 Dakar-Fann, Sénégal.
This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Indoor air pollution is the underlying cause of 4 million deaths throughout the worldwide, of which 11% is directly caused by obstructive pulmonary disease. This study showed the possibilities of characterizing indoor air pollution in Medina neighbourhood (Dakar) and it also made it possible to estimate the impact of the main living room’s ventilation on the occurrence of obstructive lung diseases (Asthma and COPD). This is a cross-sectional study based on a socio-demographic survey, air quality metrology (CO, PM10, NO, CO2) and Functional Respiratory Assessment (spirometry). The impact measurement was carried out by logistic regression taking into account a certain number of confounding factors. Participants are distributed between 27 households which mainly use gas (55.56%) and charcoal (29.63%) as cooking fuel and in closed kitchens with window (66.67%). The prevalence of Obstructive pulmonary diseases is estimated at 33.06%. Regarding pollutants, levels are below WHO guidelines: CO (3.81 ppm), CO2 (531.5 ppm), PM10 (0.27 μg/m3) and NO (2.88 μg/m3). In addition, study revealed an association between obstructive pulmonary diseases and living room’s ventilation (chi-squared test’s p-value = 0.02). Indeed, this lack of ventilation exposes residents to a higher risk of obstructive pulmonary disease: the Adjusted Odds Ratio (AOR [95%CI]) for medium and for poor levels are respectively estimated at 2.54 [1.27-5.08] and 2.06 [1.02-4.17]. These results therefore suggest that indoor air quality, particularly the renewal of air in the living rooms, as a determining factor of residents respiratory health condition.
Keywords: Indoor air, Respiratory lung disease, Senegal, Spirometry, West Africa
Individuals spend an average rate of 80% of their time inside buildings (housing, public establishments, transport, etc.) [1]. The air components of these environments varies according to weather and activities that usually take place there. Most of the anthropogenic activities emitting pollutants inside buildings are known. For housing, these include combustion processes (biomass, smoking, etc.), cleaning products, waste incineration, road traffic and/or pollution caused by nearby industries [2]. These sources contaminate indoor air by emitting carbon monoxide, volatile organic compounds (benzene, toluene, ethylbenzene, xylene, formaldehyde, etc.), particulate matter, with harmful consequences for health and environment [3,4]. According to World Health Organization (WHO), indoor air pollution is the underlying cause of 4 million deaths thoughtout world, most of which occur in low- and middle- income countries [5]. In addition, 11% of these deaths are directly linked to obstructive pulmonary diseases [6]. Countries of Southeast Asia and sub-Saharan Africa are the most affected by these conditions. Among other obstructive respiratory diseases are asthma and Chronic Obstructive Pulmonary Disease (COPD) in first line. Prevalence of the latter varies respectively between 4 and 14% and between 4 and 25% in sub-Saharan Africa [7]. These data are supported by few studies carried out in Africa with a significantly higher prevalence compared to developed countries [8-10]. In Burkina Faso and Senegal for example, respectively, a prevalence of 18.18% of asthma in women exposed to biomass smoke [9] and 43% of allergic rhinitis in street vendors exposed to road traffic has been documented [11]. These studies are an illustration of the negative impact of air pollution on respiratory health. This study supports existing literature on indoor air pollution and its health impact, particularly in Medina, a cosmopolitan city of Dakar.
Setting and study design
This is a cross-sectional study which based on socio-demographic survey, air quality metrology and Functional Respiratory Assessment. The study took place in the Medina, one of the most popular neighbourhood in Dakar with a density of 40,667 inhabitants/km2 [12]. Several main and secondary roads pass through the neighbourhood Medina , hence the heavy traffic over there. In addition, Medina is characterized by the narrowness of its housing, most of which accommodates several families. These common housings seldom often have open kitchens (opening to another room), for, they have closed kitchens (not communicate with any other room) with no windows and very little green space.
Data Sampling and collection
Indoor air quality metrology
Measurement campaign included 27 dwellings, at the rate of two successive days of sampling by 7 hours a day . Measurements were carried out using air quality monitors: AQ Pro version 1.05 is used to measure levels of nitrogen oxides (NO and NO2) while EVM-7 version 1.05 is used for carbon oxides (CO and CO2) and Particulates Matter (PM10) levels measurement.
Socio-demographic survey
In each home included in study, a questionnaire was administered to volunteers over 11 years old. In addition to certain housing characteristics (type of housing, cooking fuel, type of kitchen, burning incense, ventilation, etc.), this questionnaire is used to collect individual information (age, sex, smoking status, health status, etc.).
Functional Respiratory Assessment
It was carried out by spirometry and included participants in socio-demographic survey and others volunteers over 7 years old who had lived in Medina for at least five years and who had not had recent thoracic surgery. Moreover, parental consent had been obtained for children. Spirobank II and its accessories (scale, centimeter, recyclable tips, bronchodilator (salbutamol®) and inhalation chamber) were used to perform examination. This was done in a seated position and using a nose clip as recommended by the American Thoracic Society (ATS). A first phase without bronchodilator was implemented, then a second phase, 15 minutes after inhalation of the bronchodilator. Slow Vital Capacity and Second Maximum Expiratory Volume (FEV1) were obtained during this examination, as well as Forced Vital Capacity (CVF), estimates of Median Maximum Expiratory Flow (MED) at 75%, 50%, and 25% of CVF and Maximum Minute Ventilation (VMM).
Description of variables of interest
Obstructive lung disease
It is defined as a dependent variable and corresponds to being diagnosed with asthma and/or obstructive pulmonary disease. These disorders were diagnosed by spirometry according to the criteria of the Global Initiative for Asthma (GINA), and the Global Initiative for Chronic Obstructive Lung Disease (GOLD) [13]. Obstructive syndrome is first retained in face of a decrease in FEV1 more than 12%, a FEV1/FVC ratio less than 70% and a reduction of more than 20% in other ventilation flows. Differential diagnosis of asthma and COPD is made through a bronchial obstruction reversibility test using a β2 mimetic (salbutamol®) [13,14]. In addition, restrictive syndrome (restrictive ventilatory disorder, bronchospasm) is retained on basis to a decrease in slow vital capacity (CVL) and FEV1/FVC ratio greater than 95% in basal state [13].
Living room’s’ ventilation
It is a variable with three levels (good, medium and bad). Good ventilation corresponds to the presence of at least one door and at least one window permanently open during the day. As for medium ventilation, it corresponds to the presence of at least one door permanently open during the day associated with the lack of a window. And finally, poor ventilation, corresponds to presence of at least one door not permanently open during the day associated with lack of window.
Statistical analysis
Analysis was carried out with R software after merging different databases (spirometry, survey and air quality), setting a significance threshold for estimates at 5%. Data were described in the form of frequencies (for qualitative variables), means and standard deviation (for quantitative variables). Factors associated with obstructive lung disease were determined using chi-squared test and impact measurement was caried out by logistic regression. The odds ratios (Crude Odds Ratios (COR) and Adjusted Odds Ratios (AOR)) were estimated along with their 95% confidence intervals (95% CI).
Ethical considerations
This study was approved by the ethics committee of Cheikh Anta Diop University under number (0335/2018 / CER / UCAD) issued on 25/May/2018. The process was explained to participants, who in turn signed an informed consent letter after reading and understanding study objectives. All participants were coated according to the standards of the Helsinki Declaration, respecting the criteria of anonymity, obtaining consent, confidentiality of results, risks and benefits of the study.
Respondents’ individual characteristics
A total of 27 households and 365 volunteers participated (N) in the study. The latter concerned all residents aged at least 7 years. Sample was mainly made up of adults (42.47%), with a strong participation of children (29.86%) and adolescents (21.1%) as well as a slight female predominance (52.05%). Less than half of respondents declared having an occupational activity (45.7%) and 3.91% of participants are current smokers versus 7.03% former smokers. Pulmonary diseases are noted in 37.16% of participants; these are distributed as follows: asthma (25.74%), COPD (61.03%), bronchospasm (10.29%), mixed ventilatory disorder (2.21%) and other (0.74%). Thus, prevalence of obstructive ventilatory diseases is estimated at 33.06% (Table 1).
Table 1 : Respondents individual characteristics (in %).
Households selected characteristics
Table 2 records characteristics of surveyed households. Three types of households were identified with the majority having a surface of 150 m2 (74.07%): larger household (44.44%), apartment (37.04%) and wooden house (18.52%). Average number of residents per household is 20.89 (+/- 13.13) and more than half of the households have a good ventilation overall (59.26%). However, concerning main living room, less than half of households (25.95%) have a good level of ventilation. Regarding polluting activities related to cooking, households mainly use closed with window: 66.67% versus 25.93% of open-air kitchen. In addition, 55.56% of households use gas as cooking fuel versus 29.63% of charcoal users. Cooking takes an average 2 hours for the majority of households (55.56%). In addition, exposure to tobacco smoke and perfume sprays are respectively estimated at 66.67% and 55.56%. However, residents’ exposure levels to pollutants such as CO (3.81 ppm), CO2 (531.5 ppm), PM10 (0.27 μg/m3) and NO (2.88 μg/m3) are below WHO reference values for short-term exposure (Table 2).
Table 2 : Housing characteristics (in %) including indoor air parameters (in mean [+/- sd)).
Occurrence of obstructive lung disease by selected characteristics and chi-squared test
Regarding the results of bivariate analysis, living room’s ventilation is significantly associated with the occurrence of obstructive lung disease (p=0.02 <5%). Indeed, 16.16% of participants with an obstructive lung disease lived in households where living room’s ventilation is bad while 12.60% and 3.84% of them respectively lived in households with a medium and good ventilation for this room (Table 3).
Table 3 : Distribution of obstructive lung disease (in %) according to selected characteristics.
Impact measurement by logistic regression
Both in univariate and multivariate logistic regression, living room’s ventilation is associated with an excess risk of obstructive lung disease occurence. Results reveal Crude Odds Ratios of 2.55 [1.08-4.23] and 2.14 [1.31-4.96] for respectively medium and poor levels of ventilation. After adjusting for age, sex, smoking status, occupational activities and exposure to perfume sprays , Adjusted Odds Ratios (AOR) were estimated at 2.54 [1.27-5.08] (medium ventilation) and 2.06 [1.02-4.17] (bad ventilation) (Table 4).
Table 4 : Univariable and adjusted logistic regression models between obstructive lung disease and level of living room ventilation.
In Médina, the average number of residents per household is estimated at 20, therefore higher than national average (6 residents) and those found in Ouagadougou (7 residents) and Durban (14 residents) [15-17]. This situation reflects a promiscuity, partly explained by the history of the neighbourhood . It happens to be a traditional residential area where of most of the houses are legacies [15] hence the polynuclear structure of families. Moreover, for its proximity to the town, Medina is a place where civil servants and informal sector’ workers converge [18]. 3.91% of respondents (children excluded) declared to be current tobacco smokers, a proportion below the national average estimated at 6% in 2015 [19]. This low proportion is linked to the massive presence of women whose consumption is lower compared to men, but also to religion and culture. However, the study revealed a high proportion of exposure to passive smoking (66.67%), i.e., twice the 25% recorded in India [20]. The same is observed for exposure to perfume sprays (estimated at 55.56%). This could be the result of increased promiscuity in urban areas and high demography (about 5% per year) [21]. Indeed, Dakar concentrates about 23% of Senegalese population and nearly 61% of urban population [21]. Participants in this study are from 27 households which mainly use liquefied petroleum gas (55.56%) as cooking fuel versus 29.63% of charcoal users. Liquefied petroleum gas is indeed of very widespread usage in Senegal, particularly in urban areas where it is estimated at 49.5% versus 24.1% of charcoal use [22]. Compared to other West African countries, Liquefied petroleum gas is used much lower: 60% (Burkina Faso), 98% (Mali) and 47% (Ivory Coast) [17,23,24] use charcoal as their main energy source. Indeed, in most of these countries, access to clean energy is often more difficult for households [9]. In addition, certain ancestral culinary practices are still very widespread in these countries, unlike Dakar where the modernity of life and lack of space no longer allow certain cooking methods. Biomass fuel is involved in deterioration of indoor air quality due to the significant emission of several harmful components such as carbon monoxide, Volatile Organic Compounds (VOCs) and suspended particles [17,25,26]. It is often used in closed kitchens with window, in open air or inside bedrooms. In the urban area of Dakar, 66.67% of households have closed kitchens window compared to 40.46% in Burkina and 31.3% in Mali [24,27]. Many of these kitchens are often poorly ventilated reflecting a high level of pollution. In these kitchens, woman also stay cooking for hours, everyday . The study reveals an average cooking duration of 1-3 hours. This is similar to that noted in India (2 hours) but relatively low compared to that average cooking-time found in Zimbabwe (1.5-9 hours) [20,28]. Concerning air quality metrology, study reveals concentrations below WHO regulatory values for short-term exposition: CO (4,36 mg/m3 ), CO2 (531.5 ppm), PM10 (0.27 μg/m3) and NO (2.88 μg/m3). Higher levels of pollution have been documented by other studies. Indeed, much higher concentrations of NO (19 μg/m3) and PM10 (19 μg/m3) are found in Durban [16], and in Zimbabwe, a level of CO (23.0 mg/m3) 8 times higher was observed [28]. These levels are the result of biomass combustion inside households, the lack of air renewal, a poor hygienic condition and a set of domestic practices emitting pollutants in air [25,29]. Air quality is a determinant of respiratory health, particularly, obstructive pathologies such as asthma and COPD. 37.16% of participants (365) presented pulmonary involvement, which corresponds to asthma and COPD in 25.74% and 61.03% respectively. A proportion of asthmatics twice as high (45%) as that noted in present study is noted among bus drivers in Dakar, unlike COPD (40%) [30] which is significantly underrated [30]. Lower proportions of asthma and COPD are documented by other studies in East Africa. Indeed, asthma and COPD are noted with respective proportions of 9.8% (Uganda) and 4.5% (Rwanda), i.e., 9 and 12 times the values recorded in Medina [31,32]. Moreover, the prevalence of obstructive ventilatory disease (asthma and COPD) is estimated at 33.06%. This prevalence is multiplied by 3 compared to a Nepalese study (8.1%) among adults exposed to biomass smoke [33]. Other non-obstructive pathologies were also diagnosed in Medina, these are restrictive ventilatory disorders (2.21%) and bronchospasm (10.29%). Living room’s ventilation has been identified as a determining factor in the occurrence of obstructive ventilatory disease in the Medina. Indeed, adjusted risk (AOR [95%CI]) through age, sex, smoking status, occupational status and exposure to perfume sprays , is respectively estimated at 2.54 [1.27-5.08] and 2.06 [1.02-4.17] for medium and poor levels of ventilation in a room.
The study revealed a high prevalence of obstructive respiratory diseases among residents of the Medina. Lack of ventilation in living room is a determining factor in the occurrence of these disorders. This result suggests broadening and deepening studies on indoor air quality in housing and its health impact in order to have enough evidence to support advocacy for regulating indoor air level in Senegal particularly, but also generally in sub-Saharan Africa.
The authors declare that they have no competing interests.
| Authors' contributions | ST | MLD | KT | ANB | AF | MD | MCN | FB | NOT | MF |
| Research concept and design | √ | -- | -- | -- | -- | -- | -- | -- | -- | √ |
| Collection and/or assembly of data | √ | -- | √ | -- | -- | -- | -- | -- | -- | -- |
| Data analysis and interpretation | √ | √ | -- | -- | -- | -- | -- | -- | -- | -- |
| Writing the article | √ | √ | -- | -- | -- | -- | -- | -- | -- | -- |
| Critical revision of the article | √ | -- | -- | √ | -- | -- | -- | -- | -- | -- |
| Final approval of article | √ | √ | -- | -- | √ | √ | √ | √ | √ | √ |
| Statistical analysis | -- | √ | -- | -- | -- | -- | -- | -- | -- | -- |
We thank the ChairPol project for the technical support to this work. We would like also to thank the Medina People for their time and valuable information that they provided for this study.
Editor: David Han, University of Texas at San Antonio, USA.
Received: 01-Nov-2022 Final Revised: 07-Jan-2023
Accepted: 11-Jan-2023 Published: 09-Feb-2023
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