The effects of urbanization have produced several environmental threats where among them is air pollutant which has imposed health threats worldwide
By 2050, it is predicted that two-thirds of the world’s population are expected to live in urban areas due to the advantages it has to offer including greater opportunities to receive education, health care, and services such as entertainment.
However, due to urbanization, air pollution continues to be a significant health treat worldwide.
According to the World Health Organization (WHO), more than 2 million premature deaths each year can be attributed to the effects of urban outdoor and indoor air pollution.
Designed to offer guidance in reducing the health impacts of air pollution, the WHO Air Quality Guidelines was first published in 1987 to offer guidance on thresholds and limits for key air pollutants that pose health risks.
The guidelines apply worldwide and are based on expert evaluation of current scientific evidence particulate matter (PM), ozone (O3), nitrogen dioxide (NO2) and sulfur dioxide (SO2).
PM is a common proxy indicator for air pollution where major components of PM are sulfate, nitrates, ammonia, sodium chloride, black carbon, mineral dust and water.
The guidelines indicate that by reducing particulate matter (PM10) pollution from 70 to 20 micrograms per cubic metre (μg/m), the world can cut air pollution-related deaths by around 15%.
In low- and middle- income countries, exposure to pollutants increases the risk for air pollution-related diseases, including acute lower respiratory infections, cardiovascular disease, chronic obstructive pulmonary disease and lung cancer.
On the other hand, ozone is formed by the reaction with sunlight (photochemical reaction) of pollutants such as nitrogen oxides from vehicle, industry emissions and volatile organic compounds emitted by vehicles, solvents and industry.
Excessive ozone in the air can cause breathing problems, trigger asthma, reduce lung function and cause lung diseases.
Nitrogen dioxide is a major source of anthropogenic emissions of combustion processes (heating, power generation, and engines in vehicles and ships).
Studies shows that among the health symptoms to exposure of nitrogen dioxide includes bronchitis in asthmatic children and reduced lung function growth in cities of Europe and North America.
