**4.1 An overview for the big picture**

The desert's dust together with anthropogenic biomass burning's black carbon in the tropical regions are associated with many effects to climate and air quality.

Globally overviewed in **Figure 5(a)** and **(b)**, respectively, the dust as an air polluting aerosol expands all over the world from the world's dust belt that stretches from the Atlantic Ocean in the neighborhood of West-Northern Africa to the East and Middle Asia, and the atmospheric black carbon is abundantly stretched all over the mid-latitudes of the earth.

The Global overview of these selected aerosols and air pollutants, is an important input to research contents in the subsequent sections.

#### **Figure 5.**

*The global overview of selected Aerosols and Air pollutants' column mass density: (a) dust, aerosol and air pollutant; (b) black carbon aerosol and air pollutant.*

*An Analysis of Remote Sensing Data to Evaluate the Problem of Atmospheric Aerosol… DOI: http://dx.doi.org/10.5772/intechopen.99377*

## **4.2 The results**

The desert's dust together with anthropogenic biomass burning's black carbon in the tropical regions associate with both climate changes and air quality problems.

For example, the aerosol optical thickness (AOT), known as an extent to which aerosols obstruct the light energy transmission, via absorption or/and scattering of that light, AOT is distributed within a column of air to the top of the atmosphere [15]. The process of absorption and scattering makes up the extinction process, which means the loosing of the photon incoming energy [33].

It is according to the knowledge of the African Physical Geography as well as climates that five sub-regions had been created and those are described as region 1, 2, 3, 4 and 5.


The purpose of those five subdivisions is to obtain most reliable remote sensing results, and the focus was put in the most central part of Africa.

The findings are presented in **Figure 5**.

In this research, four seasons are shortened as:


From the existing research, the dust's particulates are one of the causes of pulmonary tuberculosis [34]; dry desert's dust in particular is one of the causes to Meningococcal meningitis ([35], p. 108–109).

In the research, **Table 1** reports the results for PM2.5, in the 5 sub-regions of Africa, and it's found that the averaged mass concentration is very high as compared to 25 μg/m3 , the recommendable concentration [14].

Looking at the table, the vastest global Desert, Sahara, which keeps expanding [1] might be the reason for the increase of the global dust aerosol since the year 2000 onwards, most notably in the seasons of DJF and MAM, during the whole time series from the year 2000 to date.

Besides, the African Sahara Desert being the biggest contributors to global atmospheric particulate matter (PM) and air pollutants in particular, **Table 1** demonstrates the concentration of PM2.5 in Africa.



**Table 1.**

*The dust's PM2.5 mass concentration in μg/m3 in five African sub-regions of interest [36].*

*An Analysis of Remote Sensing Data to Evaluate the Problem of Atmospheric Aerosol… DOI: http://dx.doi.org/10.5772/intechopen.99377*

Looking at some existing research works, "exposure to common air pollutants like fine and coarse particulate matter (PM2.5 and PM10), Nitrogen dioxide (NO2), and sulfur dioxide (SO2) were closely associated with asthma patients who visited Shanghai from January 22, 2014 to October 31, 2015 [37];" generally, the portion of nearly 90% of BC belongs to PM2.5 [38].

## **5. Discussion**

It's expected that both the inhabitants of the region of interest (RoI), and visitors will understand furthermore the dangers of particulate matter, and will take precautions to comfortably live on earth because the atmosphere is shared resource: the dust belt's PM2.5 unlimitedly spreads to the sub-Saharan, European, Asian, and Atlantic Ocean regions.

Most specifically, in this research, the direct effects of aerosols on heath are presented by results in **Table 1**, speaking of the central African focal region of interest: the dust's PM2.5 mass concentration is mostly above the highest recommended value for health which is 25 μg/m<sup>3</sup> .

With a reference to the World's Dust Belt [17], the heavily concentrated particulate matter in the west, north and central African sub-regions is attributed to the Sahara Desert, and this has nothing to do with the population.

Apart from the world's dust belt which is due to deserts, the nature source of dust aerosols and linked air pollutant groups is also from volcanic eruption activities, and anthropogenic activities.

Therefore, inhabitants of arid regions are recommended to learn from China's policy, which turned a desert into crop and forestland, cited by Rushingabigwi et al. ([39], p. 1958), which would reduce the dust aerosols which are windblown all over the world.

#### **6. Conclusions**

Aerosol science, a sub-branch of physics or physical-chemistry which, until 1980s, has been so neglected that most people have not cared about the aerosols dangers to the human breathing and blood circulation. In this research, a quick overview of aerosols and air pollutants (solid and gaseous) has been made; the research has resulted in finding more about air polluting aerosols such as the dust's fine particulate matter, PM2.5, an agent to many diseases leading to the mortality due to cardiac dysrhythmias, cardiac arrest, etc.

In this research, the west and north African sub-regions are characterized by the concentrations of PM2.5 above the standard, 25 μg/m<sup>3</sup> , in all the seasons; the same thing applies to the Central African JJA season.

In any case, the atmosphere is such a complex dynamic natural system that sustaining life on earth is very essential since the atmospheric air interacts with water and land. Acidic rain due to atmospheric chemistry of sulfate aerosols reacting with the clouds Hydrogen, for instance, is a result of air pollution.

Black carbon (abundant in the African mid-latitude and the global midlatitudes), together with dust aerosols (from deserts, volcanic activities, and anthropogenic activities), windblown from their sources to surrounding regions are certainly hazardous to the global ecosystem, especially when in the precipitation's clouds.

Therefore, for sustainability of the life on earth, this research can help policy makers to plan for the community welfare: it is expected that by publishing different research works in this area, more scholars will furthermore understand the real problem, and if supported by policy makers, smart systems will be developed for the welfare of end users.
