1. Introduction
Air pollution has become an increasingly alarming problem in many cities across the globe. The World Health Organization (WHO) stated that in 2016 “more than 80% of people living in urban areas that monitor air pollution are exposed to air quality levels that exceed [WHO] limits” [
1]. The health-related consequences of this have been well established over recent years: air pollution, especially particulate matter—referred to as PM
2.5 and PM
10 when the particle diameters measure less than 2.5 or 10 micrometers, respectively—can affect both respiratory and cardiovascular health through conditions, such as chronic obstructive pulmonary disease, myocardial infarction, stroke, and cancer [
2,
3,
4]. In addition, new links are being discovered between harmful PM pollution and diabetes, decreased neurological function in children, and increased risk of mortality in Covid-19 patients [
4,
5]. Gaseous air pollutants that are expelled through anthropogenic activities, namely nitrogen oxides (NO
x), sulfur dioxide (SO
2), Black Carbon (CO), and ozone (O
3), have also been shown to increase cardiovascular and respiratory mortality and morbidity [
6,
7]; these air pollutants further harm human health by affecting the environment through phenomena, such as acid rain [
8]. As the urban population increases, especially in low- and middle-income countries (LMICs), an increasing amount of people are becoming susceptible to suffering from these health effects [
8]. A study that was carried out in Senegal, for example, identified the links between poor air quality and conditions, like asthma and bronchitis, especially in urban regions [
9]. Air pollution also leads to millions of preventable deaths each year—4.2 million in 2016—90% of which are concentrated in LMICs [
2,
10].
Since the harmful effects of air pollution became evident, high-income countries, the WHO, and the United Nation’s (UN) Sustainable Development Goals have adopted or endorsed clean air guidelines and strategies [
4,
11]. This has helped many parts of the world today to develop effective policy means and data to control, and even reduce, harmful emissions in cities and, consequently, limit health burdens [
2]. This trend includes countries that have known harsh air pollution situations until recently, such as China [
12,
13]. However, in other regional contexts, for varying reasons, governments continue to struggle with increasing levels of urban air pollution and underperforming air quality surveillance. A clear example is the Economic Community of West African States (ECOWAS), which comprises fifteen West African nations (see map in
Figure 1). These countries are subject to unique meteorological and geographical phenomena that greatly influence air quality, such as highly seasonal weather (a rainy season between November and March, and dry season the rest of the year) and close proximity to the Sahara Desert. Especially during the dry season, most ECOWAS cities receive large amounts of Saharan dust, while others suffer from smoke from Central African forest and agricultural fires, the effects of which have not yet been widely studied for this part of the world [
14,
15]. These long-range pollution sources are added to the rapid population growth, industrialization, urbanization, and motorization that have recently taken ECOWAS cities by storm (see
Table 1), greatly increasing anthropogenic emissions due to traffic and other activities that are related to urbanization such as waste burning [
16]. Therefore, air pollution levels in ECOWAS cities are quickly rising to dangerous levels: Nigerian cities, like Onitsha and Kaduna, are now among the most polluted in the world, with PM
10 levels that are 30 and 21 times over WHO’s limit, respectively [
17]. To make matters worse, all ECOWAS nations are classified as low- or lower-middle income countries [
18], which means that their public health system is fragile and their population is more susceptible to poverty-related diseases, such as tuberculosis [
19]. Studies have shown that long-term exposure to ambient air pollution increases the risk of developing active and even drug-resistant tuberculosis infections, putting the inhabitants of ECOWAS cities further at risk [
20,
21,
22].
In general, the availability of air quality data from government sources is an issue for ECOWAS countries. This contributes to the problem of urban air pollution receiving low public attention and being placed low on governmental agendas. Consequently, public bodies frequently lack legal or political incentives, funds, standards, and policy guidelines to help them keep air quality within healthy ranges [
26]. In the countries where legislations have been passed, enforcement is often weak, as well as coordination between relevant government sectors. For example, Toure et al. [
9] showed how coordinating data from the Ministry of the Environment and the Ministry of Health would allow for better understanding the extent of the influence of air quality on respiratory conditions in Senegal, yet it is unknown whether or not such coordination occurs at the government level for Senegal or for other ECOWAS countries. Insufficient air quality data means that many national and local governments only have partial knowledge of emissions sources, concentrations, and evolution trends. It also means the effectiveness of predictive models that are used by some governments may be limited, as they require ground-level measurements to be accurate [
27]. This deficient knowledge regarding the main sources of pollution makes the creation of emissions inventories, which are a necessary input for these models, very challenging [
28]. It also hampers the selection of target values and the setting of priorities that are adapted to the local context. In sum, without such monitoring tools, addressing the health impacts of urban air pollution poses immense difficulties for policy makers.
In terms of official air quality monitoring and related health knowledge, ECOWAS countries lag behind other African ones, such as South Africa, for which studies using air quality monitoring data in order to assess health risks exist [
29]. Offor et al. [
30], for example, gathered a list of all air quality studies that were carried out for Nigeria between 1985 and 2015, all of which acquired their data independently. Another study in Senegal deployed low-cost sensors of their own to assess air quality in Dakar [
31]. ECOWAS countries have also been the subject of several large-scale initiatives aimed at characterizing and understanding air quality in the region, such as the Aerosol Robotic Network (AERONET), the African Monsoon Multidisciplinary Analysis (AMMA), or the Pollution des Capitales Africaines program; this project identified the NO
2 and Black Carbon levels—with the latter being a strong indicator for urban air pollution—exceeding WHO limits in Dakar (Senegal), Bamako (Mali), Ouagadougou (Burkina Faso), and Cotonou (Benin) between 2007 and 2010 [
32,
33]. The Dynamics-Aerosol-Chemistry-Cloud interactions in West Africa (DACCIWA) project advocated for the combination of air quality and health data by using hospital admissions from certain respiratory or cardiovascular diseases as an indicator of long-term exposure to PM
2.5 [
27]. These projects provided much-needed indications of the situation regarding the air quality of these countries, but their means were limited, and their research inevitably time-bound. As such initiatives end, ECOWAS’s main cities continue to grow and industrialize at a rapid pace, while the natural pollution sources of the area continue to exert their effects on the population, but without scientific measurements that could provide a vital understanding of the evolution of these phenomena.
Controlling levels of urban air pollution—and, therefore, controlling health-related consequences—starts with sound research. To date, no comprehensive literature review of available knowledge on this subject has been performed, as the few existing reviews on air quality and health in the Sub-Saharan African region (none were specific to West Africa) have been centered around indoor air pollution [
34] or on specific population, such as children [
35], and have not assessed the status of air quality monitoring or policy. Moreover, gray literature and expert knowledge are essential for comprehensively gathering existing information, as scientific literature for this topic and this region is limited. Against this backdrop, the present study offers a recension of existing knowledge regarding air quality monitoring networks in ECOWAS cities, evaluates current trends in the development of such networks, and reviews related policy initiatives and health effects for all fifteen countries. Such a scoping study appears to be a necessary step in better understanding where this region currently stands, identify information gaps, and highlight future research and cooperation strategies.
4. Discussion
The above results show that, in general, the status of air quality monitoring, public policy, and legislation in ECOWAS cities is slowly developing, although it has a long way to go before it reaches the levels of Europe, America, Asia, or even other African regions. Research must be promoted, so that the sources and health effects of urban air pollution in ECOWAS can be properly measured and addressed.
As highlighted by numerous studies, the particular geographical location and meteorological conditions of ECOWAS set the region at an initial disadvantage when it comes to air quality [
31]. Although less researched than other parts of the world [
3], the effects of Saharan dust on the health of ECOWAS citizens cannot be ignored. The seasonal variability of these effects adds to the difficulties that are involved in managing such a situation, even before starting to consider the additional layer of complications introduced by urban anthropogenic air pollution. Aside from the effects on cardiovascular, respiratory, and other aspects of human health, excessive anthropogenic air pollution in a region already struggling with naturally poor air quality has the potential to alter the delicate weather patterns in ECOWAS, which can, in turn, affect agricultural and farming practices, thus also damaging human health in the longer term [
27]. The lack of specificity in the information regarding polluting activities of ECOWAS cities, for example, through emissions inventories, makes it challenging to properly understand both the problem at hand and corresponding impact on health.
The results have shown that official air quality monitoring data are lacking or unavailable in most ECOWAS cities, being especially urgent for the larger ones, like Lagos (Nigeria). Some have highlighted how governments in this part of the world may not see investments in air quality monitoring as a priority, given the pressing issues that they face in other policy sectors [
46]. Infectious diseases, widespread poverty, and social deprivation, indeed, force governments to have other matters constantly on the top of their agendas. In the case of Liberia, for example, the civil war ending in 1996, along with ongoing conflicts, result in an unstable political situation, in which, understandably, air quality management cannot be set as a priority. It must also be added that not having air quality data in the first place also makes it easier for the issue of air pollution to go politically unnoticed. Moreover, when it comes to studying air pollution and related health effects, Amegah [
41] also claims that Sub-Saharan Africa—and the present study has shown that ECOWAS is particularly vulnerable to this—is systematically excluded from such research, setting the region further behind. Not having air quality or health data to highlight the severity of the situation also makes creating public awareness difficult. There are traditional practices that contribute immensely to both household and ambient air pollution in ECOWAS countries; social change in this matter requires up-to-date information to be effectively communicated to the public and their representatives, along with government-backed incentives and funds that are designed to help the adoption of new habits. Structural investments in these urban settings, for instance, in waste management and energy provision, are also a key dimension of any comprehensive policy.
The prohibitive costs of the infrastructure necessary to establish air quality monitoring networks also justifiably dissuade governments from investing in them [
28]. Once set up, there is also a long list of associated requirements, from energy needs to technical maintenance and human capacity, all of which must be strengthened in ECOWAS in order to ensure that air quality monitoring equipment continue to function. Solutions, such as low-cost sensors, are slowly spreading across ECOWAS cities. Although they appear to be a promising option to speed up the development of air quality monitoring networks, these devices carry several issues that must not be overlooked. Calibration issues can lead to unreliability, especially if there is not a reference monitor to measure against. Moreover, standards for these devices have yet to be developed, which can lead to the coexistence of sensors of varying quality [
46]. These sensors can, at least, serve as a starting point for air quality monitoring in ECOWAS, with the goal of transitioning into more permanent monitoring networks. What is clear is that increasing the availability of air quality data would be extremely useful for ECOWAS governments to improve the quality of their models, strategize on mitigation measures, target and prioritize among emissions sources, and increase stakeholder involvement. Finding an adequate combination of the different air quality monitoring equipment available to date, from research-grade equipment, to low-cost sensors, to satellite imagery, to models, could represent a cost-effective compromise for ECOWAS countries. Further research is needed in order to determine if such an amalgam has the potential to be feasible, affordable, and of acceptable quality.
It has also been highlighted that, even if more ambient air quality data are acquired through low-cost sensors or through other means, simply gathering air quality data would not be sufficient for triggering effective action against air pollution. Firstly, specific data from multiple sectors that influence air quality is necessary, such as agriculture, industry, and transportation. Coordination with the health sector should also be promoted to further the use of the data, as proposed by the DACCIWA project or by a study conducted in Senegal [
9,
27]. Neither the availability of health data nor the level of coordination between different ministries whose actions may influence health were mentioned in most studies; they were even highlighted as a concerning gap by some. Moreover, even if the data were available, there must be long-term funding mechanisms in place in order to ensure that it can be properly used and exploited. The process of acquiring data within each of these sectors will undoubtedly encounter numerous additional barriers along the way. A potential opportunity lies within the fact that most ECOWAS countries do not have air quality monitoring or detailed health information systems in place yet: they can, therefore, be designed in a coordinated fashion from the beginning, rather than made later out of a merge of two fragmented systems. Although a positive outlook, challenges that are related to the establishment of such systems within such a complex institutional landscape will undoubtedly arise.
Additionally, since data alone do not make a policy, proper attention and broad vision by policymakers and administrations is also paramount in ensuring successful urban air quality management, as improving legislation is a necessary first step. Some ECOWAS nations include the right to a clean environment in their very constitutions, and others have air quality regulations that date back to the 1980s and 1990s. Despite this strong start, these regulations are now outdated, with, for instance, PM limits that are greatly above WHO guidelines. Therefore, even in countries with published standards, public health remains insufficiently protected. The question of health literacy arises due to this situation, as what is officially considered to be acceptable air quality for these nations is already far beyond the threshold of what health guidelines consider to be so. This shows that the transfer of research and evidence into policy making encounters particular difficulties and delays in ECOWAS countries.
Moreover, there are many countries that have yet to publish air quality standards at all. Issues of fragile governance and weak enforcement capabilities must be added to these limited regulations: even when legislation is present, ensuring compliance is often a challenge due to the limited administrative resources. This is, in part, due to the fact that urban air pollution is a matter that affects an extremely wide range of sectors. Therefore, its management requires a high level of coordination and cooperation amongst them. Having an agency that is responsible for centralizing air quality management, like in the cases of Senegal, Ghana, and Ivory Coast, could lead to positive results in this respect, although detailed evaluation studies are lacking. City-level regulations or initiatives, only mentioned for Abidjan, could also serve as an interesting means of improving governance, as efforts at the local level could be less fragmented and, therefore, more effective. However, even when air pollution management is relatively centralized like in Nigeria, other aspects, like country size, the importance of industrial activity (backed by influential private networks and lobbies that are difficult to regulate), and low public awareness make enforcing regulations just as difficult. The added challenge of managing the very strategic oil sector puts the health of the citizens of the most urbanized country in ECOWAS in a delicate position. It is clear that not only a strong science-policy interface is needed—lacking in ECOWAS countries according to several experts—but also political will and strong means are essential in making progress on air quality management.
Interestingly, different studies view the problems of regulating air pollution through different lenses. While Ladan [
54] clearly sees sectorial enforcement issues to be paramount, others view the problem as a result of poor urban planning [
44], while others highlight the effects on the environment and climate change [
40]. Although general health effects are mentioned in most studies, the source of the problem—and the corresponding path towards the solution—varies greatly according to different authors, and the focus often strays from public health. A clear example is Nigeria’s shift from the Public Health Act addressing air quality to NESREA’s dependence on the Federal Ministry of the Environment. Failing to view air pollution as a public health problem in and of itself, rather than as a consequence of a different problem, threatens to remove attention from its life-threatening effects. However, the multiple ways in which it can be framed can also be seen as an advantage, since it can be tailored to different audiences and stakeholders, with the end result of improving public health regardless of the initial motivation. The growing global movement to mitigate climate change, for example, has the potential to advance the air pollution agenda, since traffic, energy, and industrial emissions are generally damaging to both causes [
40,
65]. However, the immense threat to public health may not be neglected, and research into the immediate and long-term health effects of urban air pollution in ECOWAS is highly needed in any case.
This scoping study has identified the need for further research into the status of urban air quality management in ECOWAS. Recommendations that were provided by literature and experts, which can serve to guide future research, have also been highlighted. These include promoting collaboration at various levels. While encouraging multi-stakeholder implications within ECOWAS is an ideal strategy, cooperation initiatives have generally occurred between the North and the South, such as USAID’s Air Quality Management Plan in Accra (Ghana) or the World Bank’s Pollution Management and Environmental Health Plan in Lagos (Nigeria). An unfortunate side of this is to observe the disparity that exists within ECOWAS countries, as some benefit from international partnerships while others struggle to lift their projects off the ground. The encouraging progress of countries that are involved in these programs may send the message that only those receiving this type of aid are able to advance in their air quality control plans. Placing efforts into promoting regional cooperation, or into programs that can benefit multiple nations at once, could help ECOWAS as a whole create more sustainable improvements. It should also be remembered that the natural pollution in the region, as well as the pollution resulting from desertification, makes transboundary pollution effects extremely relevant; therefore, the progress a certain country makes can be limited to what is ongoing in neighboring ones. This can serve as additional motivation to share resources and combine efforts when it comes to addressing air pollution. Furthermore, reviewing the literature findings, it seems that countries with laws or regulations on air quality have not yet implemented air quality monitoring, while countries with air quality monitoring stations have yet to promulgate their standards. In the end, it could seem difficult to take effective action in either situation: for countries with regulations, it is difficult to know whether they are being met without proper air quality monitoring and, for those countries that do monitor air quality, there are no standards to compare the acquired data to. This paradoxical situation could actually present as an additional opportunity for cooperation amongst ECOWAS nations, where the strengths of the first group of countries can serve to address the gaps of the second, and the other way around. Despite these findings, it is clear that further research, including local insights from experts in the field, is needed in order to better understand upcoming steps that ECOWAS countries should take when it comes to urban ambient air quality monitoring.
Finally, ECOWAS could draw from the example of other African countries—and even entire regions—that can serve as a roadmap for their combined air pollution-combatting efforts. South Africa, for example, has a well-distributed air quality monitoring network, which, as mentioned before, has led to studies that use official air quality monitoring data in order to assess air quality and corresponding health effects [
29,
41]. Several other African nations also have air quality monitoring stations in place: Botswana began monitoring air quality in 1996 and, today, has 21 stations, and both Ethiopia and Tanzania have eleven installed air quality monitoring stations. In addition, these countries use WHO or United States EPA guidelines until their own air quality standards are promulgated [
26]; it should be noted, however, that data on ambient air pollution-related health issues in these countries is lacking in most cases, as public health surveillance efforts continue to focus on infectious diseases or indoor air pollution [
66,
67,
68,
69,
70]. At the regional level, it has been mentioned how Northern, Eastern, and Southern African countries have strived for a regional approach in order to address urban air pollution. While ECOWAS has come together on economic and financial matters [
71], such collaboration on this front is only slowly taking off. Recent initiatives, such as the West and Central Africa Regional Framework Agreement on Air Pollution, signed in Abidjan in 2009, showed promise for a regional approach to addressing urban air pollution [
72]. The ECOWAS-wide pledge to reduce sulfur in fossil fuels [
73], which was signed this year, was also a strong statement. However, it is unsure whether substantial concrete action has occurred. Stronger cooperation, policies adapted to the local context, and strategies informed by precise data and knowledge are crucial in helping ECOWAS, and Africa as a whole, fight urban air pollution and its health effects in a resolute and effective way.
Limitations
The main limitation of this study refers to the low level of information available regarding the status of urban air quality monitoring, policy, and health effects across ECOWAS countries. Most states have little or no available literature that met the inclusion criteria, as most included literature covered larger nations, like Nigeria. Although this highlights the need for further research, it makes it difficult to determine each country’s specific situation. Out-of-date government websites, lacking access to official legislation, and insufficient local insights added to the difficulties in obtaining reliable information on the status of air pollution in ECOWAS cities.
Additionally, the aim and scope of the study could have led to the exclusion of studies that more directly addressed the health effects of urban air pollution in ECOWAS. However, including these would have strayed from the objective of assessing the status of official air quality monitoring and policy in ECOWAS cities. Likewise, studies focusing exclusively on indoor air pollution may have provided some insight into the ambient air quality of ECOWAS cities or on health effects, yet including them would have strayed too far from the aims and scope of the present review.