Atmospheric Pollution (World of Earth Science)
Atmospheric pollution (also commonly called air pollution) is derived chiefly from the spewing of gasses and solid particulates into the atmosphere. Many pollutantsust, pollen, and soil particlesccur naturally, but most air pollution, as the term is most commonly used and understood, is caused by human activity. Although there are countless sources of air pollution, the most common are emissions from the burning of hydrocarbons or fossil fuels (e.g., coal and oil products). Most of the world's industrialized countries rely on the burning of fossil fuels; power plants heat homes and provide electricity, automobiles burn gas, and factories burn materials to create products.
Air pollution is a serious global problem, and is especially problematic in large urban areas such as Mexico City, Mexico, and Athens, Greece. Many people suffer from serious illnesses caused by smog and air pollution in these areas. Plants, buildings, and animals are also victims of a particular type of air pollution called acid rain. Acid rain is caused by airborne sulfur from burning coal in power plants and can be transported in rain droplets for thousands of miles. Poisons are then deposited in streams, lakes, and soils, causing damage to wildlife. In addition, acid rain eats into concrete and other solid structures, causing buildings to slowly deteriorate.
Scientists study air pollution by breaking the particulates into two different categories of gasses: permanent and variable. The most common of the stable gasses are nitrogen at 78%, and oxygen at 21% of the total atmosphere. Other highly variable gasses are water vapor, carbon dioxide, methane, carbon monoxide, sulfur dioxide, nitrogen dioxide, ozone, ammonia, and hydrogen sulfide.
Output of variable gasses increases with the growth of industrialization and population. The benefits of progress cost people billions of dollars each year in repairing and preventing air pollution damage. This includes health care and the increased maintenance of structures such as the Great Pyramids of Egypt that are crumbling, in part due to air pollution.
The effects of air pollution have to be carefully measured because the build-up of particulates depends on atmospheric conditions and a specific area's emission level. Once pollutants are released into the atmosphere, wind patterns make it impossible to contain them to any particular region. This is why the effects of pollution from major oil fires in the Middle East are measurable in Europe and elsewhere. On the other hand, terrestrial formations such as mountain ridges can act as natural barriers. The terrain and climate of a particular area (e.g., Denver, Houston, and Los Angeles) can also help promote or deflect air pollution. Specifically, weather conditions called thermal inversions can trap the impurities and cause them to build up until they have reached dangerous levels. A thermal inversion is created when a layer of warm air settles over a layer of cool area closer to the ground. It can stay until rain or wind dissipates the layer of stationary warm air.
The United States government plays an active role in establishing safe and acceptable levels of clean air. In 1967, Congress passed the Air Quality Act that set forth outlines for air quality standards. The Environmental Protection Agency released the first nationwide survey on air pollution in 1989 after Congress passed a law requiring the report. In most cases, it is up to individual states, however, to enforce air pollution controls and meet federally mandated goals. In addition, states may set their own clean air standards that are more strict than those established at the federal level. For example, in 1989, California adopted a radical air pollution reduction plan that essentially requires each region to drastically reduce current levels of air pollution. Even as early as 1970, California adopted more stringent standards for motor-vehicle emissions.
Government regulations have shown moderate success. Since 1970, emissions of sulfur oxide, carbon monoxide, lead, and hydrocarbons have decreased by approximately 30% while nitrogen oxide output has been reduced by approximately 10%. Cars are now required to have pollution-control devices called catalytic converters, and most power plants are equipped with filters called scrubbers to remove sulfur oxides.
In addition to atmospheric pollution, indoor air pollution also poses special hazards. Some man-made sources of indoor air pollutants include asbestos particulates and formaldehyde vaporsnce common building materials now thought to cause cancer. Lead paint is also a problem in older buildings, but its use has been phased out. Other sources of man-made indoor air pollution include improperly vented stoves and heaters, tobacco smoke, and emissions or spillage from pesticides, aerosol sprays, solvents, and disinfectants.
See also Atmosphere; Geochemistry; Global warming; Greenhouse gases and greenhouse effect; Petroleum, economic uses of; Rate factors in geologic processes; Weathering and weathering series