Air pollution is increasingly understood as a global issue, requiring an understanding of pollution sources, transport, and transformation from local to regional to global scales (IPCC, 2013). Polluting gases, such as ozone (O3) and aerosols, particularly PM 2.5, are known to be major risk factors for public health (Cohen and others, 2017; Brauer and others, 2016). Fine particulate matter, such as PM 2.5 and PM 10, have diameters that are smaller than 2.5 μm and 10 μm, respectively, and penetrate deep into the lungs and cardiovascular system, causing diseases including stroke, heart disease, lung cancer, chronic obstructive pulmonary diseases, and respiratory infections. Tropospheric ozone, nitrogen dioxide (NO2) and sulphur dioxide (SO2) can irritate and damage the respiratory system, causing problems particularly to people with existing lung problems, such as asthma. Nitrogen dioxide and volatile organic compounds (VOCs), such as formaldehyde, also react to create ozone, or photochemical smog, while SO2 and NO2 can contribute to forming particulate matter. According to a World Health Organization report (2014), air pollution in 2012 caused the premature deaths of around 7 million people worldwide. It was estimated that if the aerosol level could be reduced to the safety level, about 300,000 to 700,000 persons could be prevented from premature death in developing countries. Industry, transportation, coal power plants, and household solid fuel usage contribute significantly to air pollution. Air pollution continues to rise at an alarming rate and affects economies and quality of life.
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