21-09-2017, 10:13 AM
Air pollution occurs when noxious substances including particles and biological molecules are introduced into the Earth's atmosphere. May cause disease, allergy or death of humans; can also cause damage to other living organisms, such as animals and food crops, and can damage the natural or built environment. Human activity and natural processes can generate air pollution.
Indoor air pollution and poor urban air quality are listed as two of the world's worst toxic pollution problems in the 2008 Blacksmith Institute report, the worst polluted sites. According to the World Health Organization report of 2014, air pollution in 2012 killed around 7 million people worldwide, an estimated estimate by the International Energy Agency.
An air pollutant is a substance in the air that can have adverse effects on humans and the ecosystem. The substance may be solid particles, liquid droplets or gases. A contaminant can be of natural or artificial origin. Contaminants are classified as primary or secondary. Primary pollutants are usually produced from a process, such as ash from a volcanic eruption. Other examples include carbon monoxide gas from the exhaust of motor vehicles, or sulfur dioxide released from the factories. Secondary contaminants are not emitted directly. Rather, they form in the air when primary pollutants react or interact. Ozone at ground level is a prominent example of a secondary pollutant. Some contaminants can be both primary and secondary: both are emitted directly and formed from other primary pollutants.
