Air Pollution

Air Pollution

Air pollution is a general term for a variety of substances and gases in our air that pose risks to health. Pollutants and irritants include nitrogen oxides, sulfur dioxide, carbon dioxide, particulate matter, volatile organic compounds (VOCs), toxic substances such as mercury, and some naturally occurring substances such as pollen. The combination of nitrogen oxides and VOCs in the presence of sunlight forms ozone, the major constituent of smog. Ozone has been shown to exacerbate asthma and cause shortness of breath and lung damage.

Most air pollution comes from human-made sources such as fossil fuel combustion, transportation, power plant emissions and emissions from other industrial processes. Burning fossil fuels for electricity generation is the single greatest source of air pollution in the United States. Fossil fuel combustion produces many pollutants including nitrogen oxides, sulfur oxides, hydrocarbons, mercury and particulates. These pollutants can cause serious health problems including asthma, irritation of the lungs, bronchitis, pneumonia, decreased resistance to respiratory infections, and even early death.

Some pollutants also cause certain environmental conditions, such as acid rain and climate change. Carbon dioxide emissions are a primary contributor to climate change. According to climate scientists, if carbon dioxide levels continue to increase, the planet will become warmer in the next century, affecting human health and the environment. Increases in temperature will most likely result in a variety of impacts including more heat-related illness, more severe weather events such as floods and droughts and resulting damage, and an increase in cases of vector-borne and water-borne diseases, and sea-level rise. Nitrogen oxides and sulfur oxides are important constituents of acid rain, which destroys lakes and rivers, diminishes crop yields, and deteriorates buildings.

Some air pollutants are toxic. Also known as hazardous air pollutants, these pollutants are known or suspected to cause cancer or other serious health effects, such as reproductive effects or birth defects, or adverse environmental effects. Examples of toxic air pollutants include VOCs such as benzene, which is found in gasoline, persistent organic compounds such as dioxin, and metals such as mercury and lead.

Indoor Air Pollution

The term "air pollution" typically conjures up images of smog, smokestack plumes, and other outdoor concentrations of air pollutants. However, the pollution of air indoors can have an even more detrimental impact on human health. In most industrialized countries, people spend more than 90 percent of their time indoors, increasing exposure to pollutants within closed walls. Indoor pollution sources that release gases or particles into the air are the primary cause of indoor air quality problems in homes. Inadequate ventilation can increase indoor pollutant levels by not bringing in enough outdoor air to dilute emissions from indoor sources and by not carrying indoor air pollutants out of the home. High temperature and humidity levels can also increase concentrations of some pollutants. Outdoor air pollutants can also be a problem indoors, especially on nice days or hot days when windows are left open.

Indoor environments tend to collect and concentrate pollutants, like cigarette smoke and carbon monoxide. Additionally, indoor combustion of fuels such as oil, gas, kerosene, coal, and wood, emit carbon monoxide. Plus, building materials tend to produce air pollutants as they age, such as dust from deteriorating carpets, and lead from interior paint. Mold can also develop indoors and mold spores can disperse in indoor air. Potential health effects and symptoms associated with mold exposures include allergic reactions, asthma, and other respiratory complaints. Cockroaches colonize indoor environments, releasing dander which aggravates asthma, and the pesticides used to control these and other indoor pests can persist indoors longer than they would outside.

The elderly, infants, and the ill are the most susceptible to many indoor air pollutants because of their weaker immune systems and tendencies to spend longer periods of time inside. It is especially important to protect air quality in places where people spend long hours or where vulnerable populations congregate: homes, schools, workplaces, hospitals, and other community meeting places.

Solutions to Air Pollution

To combat pollution in the United States, the Clean Air Act Amendments of 1970 gave the Environmental Protection Agency (EPA) the authority to establish and enforce air pollution standards and to set emission standards for new factories and extremely hazardous industrial pollutants. The states were required to meet "ambient air quality standards" by regulating the emissions of various pollutants from existing stationary sources, such as power plants and incinerators, in part by the installation of smokestack scrubbers, electrostatic precipitators, and other filters. Auto manufacturers were mandated to install exhaust controls or develop less polluting engines. The Clean Air Act, as amended in 1977, authorized the EPA to impose stricter pollution standards and higher penalties for failure to comply with air quality standards.

In 1990 when the act was reauthorized it required most cities to meet existing smog reduction regulations by the year 2005. The 1990 amendments also expanded the scope and strength of the regulations for controlling industrial pollution. The result has been limited progress in reducing the quantities of sulfur dioxide, carbon monoxide, nitrogen oxide, ozone, particulate matter, and lead in the air. The EPA also regulated hazardous air pollutants, which in 1992 included mercury, beryllium, asbestos, vinylchloride, benzene, radioactive substances, and inorganic arsenic.

The most satisfactory long-term solutions to air pollution may well be the elimination of fossil fuels and the ultimate replacement of the internal-combustion engine. To these ends efforts have begun in the United States, Japan, and Europe to develop alternative energy sources (see energy, sources of), as well as different kinds of transportation engines, perhaps powered by electricity or steam. A system of pollution allowances based on trading emission rights has been established in the United States in an attempt to use the free market to reward pollution reductions, and the international sale of surplus emission rights is permitted under the Kyoto Protocol (see below). Other proposed solutions include raising electricity and gasoline rates to better reflect environmental costs and to discourage waste and inefficiency, and mechanical