The World Health Organization released a report that estimated the annual premature deaths caused by air pollution as three million, many of which are children under five years old. Air pollution is associated with a higher incidence of heart disease, stroke, asthma, emphysema, and various types of diseases and cancers. Air pollution has harmful impacts on human lives directly or indirectly as it affects the food chain and disturbs the whole ecosystem. And air pollution formed over the years now has become a global issue. Air pollution is differentiated into outdoor air pollution and indoor air pollution.
Outdoor Air Pollution
There are two types of outdoor air pollution, primary pollutants and secondary pollutants. The former generally means the hazardous substances and chemicals are directly discharged into the atmosphere by manmade or natural ways. The latter refers to harmful chemicals and substances that are generated as a consequence of reactions between primary pollutants suspended in the air.
Here are the principal primary pollutants:
sulfur dioxide (SO2), carbon dioxide (CO2), Nitrogen dioxide (NO2) and carbon monoxide (CO)
All these oxides can be produced naturally, but human activities and industry are the main sources of oxides. The most common causes of oxides include fossil fuel combustion, industrial waste gas emitted by power plants, large factories and automotive exhaust. Carbon monoxide and nitrogen are toxic gases. Sulfur dioxide, attributable to acid rain, is highly dangerous to people and a known allergen. Carbon dioxide is mainly responsible for global warming.
Volatile organic compounds (VOCs):
methane, isoprene, benzene and formaldehyde
These can be generated naturally and artificially. However, the creation of volatile organic compounds by humans significantly exceeds that of natural processes. Human activities, such as the production of solvents and paints, and the burning of coal and wood, release enormous quantities of VOCs into the air. Since organic compounds have relatively low boiling points, it’s easy for them to sublimate or evaporate at normal temperature. Methane, as a kind of greenhouse gas, is also responsible for global warming, while other VOCs have long-term negative effects on the health of humans.
In the last century, CFCs were widely used in the production of refrigerators and aerosol propellants. But the use of CFCs has been reduced and phased out as it was found that they had the ability to deplete the ozone layer, which blocks much of the ultraviolet radiation from the sun. Though the use of CFCs has been widely banned, CFCs in the air and products which have strong links with refrigeration will still keep depleting the ozone.