Clean air contains only the gases and water vapor needed to keep the Earth's environment healthy. Pollutants are substances, or even energy, that harm living — and some non-living — things. A high concentration of pollutants in the air is called air pollution.
Air pollution can destroy our environment and can cause humans and other living things to become sick. Sometimes, air pollution can cause rashes, eye/nose irritation, headaches, sleepiness, coughing, sneezing and dizziness. If you breathe in too much air pollution, of a very high concentration, it can cause severe illnesses, such as cancer, asthma, kidney failure, liver damage and even birth defects. Air pollution negatively affects the plants and animals in our environment as well.
Air pollution can even destroy buildings. Particles of pollution may coat a building, making it look dirty. Pollution can also cause acid rain that can eat away at buildings
Engineers that work on air pollution problems must have a good understanding of the composition and characteristics of air before beginning to design technology solutions for air pollution. Some of the technologies that engineers have designed to clean up air pollution include a scrubber, an electrostatic precipitator, a cyclone and a baghouse.
What are Air Pollutants?
There are literally hundreds of pollutants that float around at any given time in the air that we breathe. Some of these pollutants come from natural sources, but most come from human activity. Air pollution consists of the gases and particles that affect the quality of the air around us, are harmful to the environment, and/or enter the atmosphere at highly concentrated levels. Air pollution generally consists of: visible gases, invisible gases and particulates (such as, soot), as well as fibers, mists, molds and bacteria. These particulates can be found both outdoors and indoors. Most major air pollutants are invisible (like carbon dioxide and carbon monoxide but large amounts of them can be seen as smog when they are concentrated in areas such as cities. Because visible pollutants (like particulate matter and photochemical smog) are more obvious, we understand more about them and tend to have more regulations focusing on them than we do on invisible pollutants.
Particulate matter is often invisible to the naked eye unless it is very concentrated. To study the particulates more easily, it is possible to "catch" and identify some of them by concentrating them on a collector. Engineers use a variety of technologies to measure concentrations of and identify types of particulate matter. Engineers must first learn this information about a pollution site before working towards cleaning up the pollutants. Engineers also use this information to help design new technologies (new fuel types, more efficient engines, process treatments in industrial applications, etc.) that more effectively prevent and reduce air pollution.
The word "smog" comes from the combination of the words "smoke" and "fog." It was first used in the early 1900s to describe the combination of smoke and thick fog that sometimes hung over London, England. Today, smog really refers to photochemical smog,a combination of Volatile Organic Compounds (VOCs) and Nitrogen Oxides. When exposed to sunlight, photochemical smog creates tropospheric ozoneand other irritants. Weather conditions, such as lack of wind can cause smog to build up. Smog is especially obvious during a thermal inversion that prevents the smog fromrisingand scattering). Mountain ranges near cities can also trap smog in an area.
Sources of Air Pollution (Outdoor/Indoor)
Man-Made Outdoor Sources
The burning of fossil fuelsis one of the main causes of air pollution and is a major contributor to global climate change. Smoke and fumes containing carbon dioxide and sulfur dioxide from power stations and factories are the worst offenders. Car exhaust is another large source of air pollution. It contains both invisible gases (carbon dioxide, carbon monoxide, hydrocarbons, and nitrogen oxides) and particles. Many consumer products (hair spray, paint and cleaners) release high levels of volatile organic compounds(VOCs) into the atmosphere. Other important sources include gas stations, industry (many types), agriculture and forestry.
One of the greatest sources of air pollution is the incomplete combustion of gasoline in car engines. The engines are only about 30% efficient; this means that for every 10 gallons of gasoline in the tank, only three gallons are actually used to move the vehicle! Some of the remaining gas heats the engine and some is pushed out of the engine unburned. This inefficiency is one of the largest contributors to photochemical smog. If gasoline were completely burned, the only by-products would be water vapor and carbon dioxide. Carbon dioxide can still be harmful to the environment when emitted in large amounts, but complete combustion limits the number of other harmful gases released into the atmosphere. Engineer-designed devices that reduce pollution emissions include catalytic converters, modified fuels and more efficient engines.
Natural Outdoor Sources
Volcanic eruptions often spew gases and ash into the atmosphere. Forest fires also release dust and smoke into the air.
Indoor air pollution is becoming a large concern of environmental engineers because the majority of the public's time is spent indoors. Indoor air (IA) pollutants can be created within the building or drawn inside from outdoor sources. Indoor sources include: equipment (malfunctioning HVAC systems, emissions from office equipment/labs), furnishings (new carpet that releases formaldehyde and burnt Teflon pans), dust-producing or water-damaged materials, unsanitary trash emissions, insects and pests (pesticides), food preparation areas, fungi, cleaning materials, pets (dander), and people (smoking). Some of the most common outdoor air pollutants that are brought inside are: smog, bacteria and mold spores, vehicle exhaust, exhaust fumes, pollen and dust, algae (from standing water) and smoke
Sound and Light Pollution
Some people also consider sound pollution a type of air pollution, because sound waves travel through the air. Outdoor sources include loud jets, construction equipment, huge trucks and other forms of transportation, etc. Indoor sources include music, TVs, mixers, dishwashers, washing machines, etc. Lights are also considered a source of air pollution to astronomers. Both sound and light pollution can affect human health as well as the health and migration patterns of animals.
What Are Air Pollutant Solutions?
To help inform this discussion, you may be interested in viewing the Asthma Free School Zones video below for your own edification or to share with your students in class.
The water cycle usually cleans air pollutants naturally. Currently, however, there are two problems with this: the water cycle is unable to clean contaminants as quickly as they are added, and high concentrations of pollutants contribute to acid rain.
Governments around the world are attempting to help control air pollution by passing laws, such as the Clean Air Act in the United States or the European Union’s Directive on Ambient Air Quality and Cleaner Air for Europe. Many governments also pass strict legislation to control the amount of by-products released by industrial companies and modes of transportation. These air quality standards are designed to protect the health and welfare of people, plants and animals, and to protect buildings, monuments, water resources, etc. In order to enforce these laws, however, it is important to monitor air quality over time.
One of the largest problems environmental engineers face is creating new techniques to prevent additional air pollution. In the U.S., there are many changes that have occurred as a result of the passing of new environmental laws. For example, many places used to burn coal as a means of heating or running machinery. Now, we know that burning coal (and other fossil fuels) causes air pollution, and many people do not burn coal as a result of public awareness and stricter air emissions laws. Another example is with the engineering of automobiles. Generally, most cars still burn gasoline (a fossil fuel), which, as we know, is a cause of air pollution, but new laws have changed how cars are built. In the last 25 years, there have been major improvements in motor vehicle technology that have led to exhaust emission reductions of up to 96% compared to vehicles from 1960.
Informed citizens are also making adjustments on a more personal level to help improve the air. For example, many of us are reducing fuel use by joining a car pool, taking the bus/train, riding a bike or walking, reducing the energy we use, and buying environmentally friendly products, like non-aerosol hair spray and non-toxic cleansers that will all help in the efforts to reduce air pollution.
Air Pollution Factoids
- Mexico City is one of the world's most polluted cities. When the air pollution is at its worst, birds have been known to drop dead out of the sky.
- Every day, each of the world's 11 billion cattle gives off 1 pound of methane (produced in their gut as they digest food). That means 274 billion pounds (137 million tons) of methane is produced each year! Methane is also produced in large quantities by rotting vegetation in landfills. Methane is a major greenhouse gas and contributes to climate change.
- The American Lung Association believes that sulfur-dioxide exposure (one source is the internal combustion engine of autos) is the third leading cause of lung disease,following smoking. It has also been implicated in the rising occurrence of asthma, bronchitis and emphysema. The average person takes about 20,000 breaths a day.
- Plants give us oxygen, and yet people have destroyed almost two-thirds of the original forests on Earth.
- Sometimes Hawaii has "vog" alerts. These are times when volcanically produced smog is at dangerous levels.