Air pollution

Claude Monet's drawing of London smog, which is made because of air pollution. Sometimes air pollution can become so dangerous that people have to wear surgical masks when they go outside.

Air pollution is a change in the air that can influence the health, survival, or activities of organisms, including humans. Many of the world's large cities today have bad air quality. Even 2,000 years ago, the Romans were complaining about the bad air in their cities (at that time, the air was thick with smoke from fires and the smell of sewer). Air pollution has been for a long time a danger to human health and Earth's many ecosystems.

Air quality

Even "clean" air is not really clean. It has many pollutants (things that pollute the air) from natural sources. These pollutants include dust, sea salt, volcanic ashes and gases, smoke from forest fires, pollen, and many other materials. In fact, there are many more natural pollutants than pollutants that human make. However, humans have adapted to most of these natural pollutants.

Types of air pollution

Ash from volcanic eruptions is an example of primary pollutants.

Air pollutions are usually described as either primary pollutants or secondary pollutants. Primary pollutants are pollutants that are put directly into the air by humans or natural sources. For instance, exhaust (gas) from cars, soot from smoke, duststorms and ash from volcanic eruptions (as seen in the picture on the left), are all examples of primary pollutants.

Secondary pollutants are pollutants that are made from chemical reactions when pollutants mix with other primary pollutants or natural substances like water vapor. Many secondary pollutants are made when a primary pollutant reacts with sunlight. Ozone and smog are secondary pollutants. Ozone is a gas that is helpful and takes in harmful rays from the sun. When it is near the ground, though, ozone is a dangerous pollutant that influences the health of all organisms.

Sources of Human-made air pollution

There are many problems caused by air pollution, like greenhouse effect and acid rain.

Human-made air pollution comes from many things. Most air pollution made by humans today is because of transportation. Cars, for instance, make about 60% of the human-made air pollution in the United States. The gases inside car exhaust, like nitrogen oxide, make smog and acid rain.

Industrial air pollution

Many industrial power plants burn fossil fuels to get their energy. But burning fossil fuels can make lots of oxides (chemical compounds that have oxygen and other elements inside). In fact, the burning of fossil fuels makes 96% of the sulfur oxides in the atmosphere.

Some industries also make chemicals that make poisonous fumes (smoke).

Indoor air pollution

Air pollution is not only on the outside. Homes, schools, and buildings can have lots of air pollution, too. Sometimes the air inside a building is even worse than the air outside. Many things we use every day pollute the air. Compounds inside carpets, paints, building materials, and furniture also pollute the air, especially when they are new.

In buildings where the windows are tightly shut to stop air leaks and so the payment for electricity will be less, pollutants can be higher than outside.

Air pollution

Air pollution is a problem everywhere in the world. Local air pollution usually influences big cities. Air pollution becomes a worldwide problem when local pollution moves away from where it came from. For example, winds carry air pollution made in the middle of the western part of the United States to Canada, like acid precipitation.

Acid precipitation

Acid precipitation is precipitation, like rain, sleet, or snow, that has acids from air pollution. When fossil fuels are burned, they let out oxides into the air. When these oxides mix with water in the atmosphere, they make acid, which fall as precipitation. Acid precipitation can kill living things, like fish and trees, by making the place where they live too acidic. Acid rain can also damage buildings made by limestone and concrete.

Ozone hole

Other global concerns because of air include the greenhouse gases and the ozone hole in the stratosphere. The ozone hole in the stratosphere is supposed to protect people from the Sun's harmful ultraviolet rays. But in the 1970s, scientists found out that some chemicals let out into the atmosphere makes the ozone turn into oxygen, which makes more ultraviolet rays reach the Earth. During the 1980s, scientists found that the ozone hole above the South Pole had thinned by 50 to 98 percent.

Human health

On March 17, 1992, in Mexico City, all children under the age of 14 could not go to school because of air pollution. This does not often happen, but being exposed to air pollution every day can make people have many health problems. Children, elderly (old) people, and people with allergies especially, can have a lot of problems because of air pollution. Studies from the University of Birmingham showed that deaths because of pneumonia and air pollution from motor vehicles like cars are related. The World Health Organization said that 2.4 million people died because of direct problems of air pollution.Some of the problems include:

Head Dizziness Headaches

Face Burning, scratchy eyes Runny nose Coughing and hard breathing

Other Lung cancer and lung diseases Sore throat Chest pains, colds, and allergies

Other Websites

Air quality science and general information

• UNEP Urban Issues
• European Commission > Environment > Policies > Air >Air Quality.
• UNEP Partnership for Clean Fuels and Vehicles

Air quality modelling

• Stuff in the Air Standard air quality modelling procedure for industrial sources.
• Wiki on Atmospheric Dispersion Modelling. Addresses the international community of atmospheric dispersion modellers — primarily researchers, but also users of models. Its purpose is to pool experiences gained by dispersion modellers during their work.
• Air Dispersion Modeling Conversions and Formulas One of six technical articles devoted to air quality and air pollution dispersion modeling.

Effects on human health

• Air Pollution Triggers Blood Clots
• American Lung Association of New England on air quality.