Air pollution causes depletion of ozone in the stratosphere which endangers human health as well as the Earth’s ecosystems. Air pollutants can be in the form of solid particles, liquid droplets, or gases. They could be natural or man-made.
Pollutants can be classified as either primary or secondary. Substances which are directly emitted due to certain processes like ash from a volcanic eruption, or carbon monoxide gas from a motor vehicle exhaust or sulfur dioxide released from factories- are primary pollutants.
Secondary pollutants are not emitted directly. They form in the air when primary pollutants react or interact. One example is ground level ozone. There are also pollutants that are both primary and secondary: that is, they are both emitted directly and formed from other primary pollutants. About 4 percent of deaths in the United States is the result of air pollution, says a study. Air pollution can cause skin and eye allergies, cancer, lung disease, etc.
Primary pollutants produced by human activity include sulfur oxides, nitrogen oxides, carbon monoxide, carbon dioxide, volatile organic compounds, particulate matter, toxic metals like lead, cadmium and copper, chlorofluorocarbons, foul odors (from garbage, sewage and industrial processes) and radioactive pollutants. Secondary pollutants include particulate matter formed from gaseous primary pollutants and compounds in photochemical smog.
Smog is a form of air pollution. Nowadays it is caused by vehicular and industrial emissions. Ground level ozone and peroxyacetyl nitrate are other secondary pollutants. Persistent organic pollutants (POPs) are organic compounds that can withstand environmental degradation.
Many activities are responsible for the formation of air pollutants. These sources...