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View Article Sources. What Is Air Pollution? What is ozone? VOCs: Carbon-containing compounds that easily evaporate at room temperature and enter the surrounding air. Many VOCs are emitted naturally by plants. Others come from human-made sources, including products such as paints, pesticides, solvents, and processes such as fuel production and combustion.
Gas-powered lawn equipment and older-model cars emit particularly high levels of VOCs. Until relatively recently, car emissions were the largest source of VOCs in most cities. However, the catalytic converter almost completely eliminates these emissions in modern vehicles. Nitrogen oxides: A family of gases that cause pollution and are harmful to human health. Trucks and automobiles are responsible for about half of all nitrogen oxide emissions, with electric power plants and other industrial sources contributing most of the rest.
In addition to smog, nitrogen oxides are converted in the atmosphere to nitric acid, a component of acid rain. What is particulate matter? How do ozone and particulate matter affect human health? How do ozone and particulate matter affect the environment? Due to the direct production of it by vehicles, the smog forms over cities where many people may encounter its adverse health effects.
Hotter days mean more photochemical smog, especially in the densely populated cities such as those mentioned above. As more and more urban populations arise around the globe, this problem is only expected to increase. Nitric oxide NO and nitrogen dioxide NO 2 are emitted from the combustion of fossil fuels , along with being naturally emitted from things such as volcanos and forest fires it is the immense concentration of these pollutants within cities that is of the most concern however, as natural emissions tend to spread out over larger areas.
When exposed to ultraviolet radiation, NO 2 goes through a complex series of reactions with hydrocarbons to produce the components of photochemical smog—a mixture of ozone , nitric acid , aldehydes , peroxyacyl nitrates PANs and other secondary pollutants. NO 2 , ozone and PANs are called photochemical oxidants because they can react and oxidize certain compounds in the atmosphere or within a person's lungs that are not normally oxidized.
Even small traces of these chemicals can affect the respiratory tract of humans and animals, and damage crops and trees. Photochemical smog has many adverse effects. When combined with hydrocarbons, the chemicals contained within it form molecules that cause eye irritation. Radicals in the air interfere with the nitrogen cycle by preventing the destruction of ground level ozone.
Other effects include reduced visibility and respiratory ailments. Ground level ozone is also produced which has various effects on the human body. For more information, visit the ozone page.
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