Each individual breathes nearly 3,400 gallons of air every day. Yet the air is being polluted by human activities like driving cars, burning fossil fuels, and manufacturing chemicals, and natural events such as forest fires. These add gases and particles to the air we breathe and, in high enough concentrations, can have harmful effects on people and the environment. Many air pollutants such as those that form ground level ozone, acid rain, and some toxic compounds remain in the environment for long periods of time and can be transported great distances from their origin.

Since air pollutants do not recognize political boundaries, states and communities cannot independently solve all of their air pollution problems. Resolving air pollution control issues often requires state and local governments to work together to reduce air emissions.

Ozone "precursors," such as NOx emissions, as well as ozone itself, can be carried hundreds of miles from their origins, causing air pollution over wide regions. Although many urban areas have made efforts to control ozone by reducing local NOx and VOCs emissions, incoming ozone transported from other areas also need to be addressed in order to meet the National Ambient Air Quality Standards. High levels of ozone entering some nonattainment areas can make achieving the national ozone standard difficult and costly, unless upwind sources are identified and controlled. If these sources fall within a certain state's boundaries, it can take measures to control them. If, as is often the case, these sources fall beyond the political boundaries of that state, it must work with EPA and other states to reduce air pollution on a regional scale. Often, it is more cost-effective to reduce emissions from upwind sources than to control emissions from smaller businesses in the nonattainment areas being affected downwind.

Some regional strategies for reducing ground-level ozone include:

• reducing NOx emissions from power plants and industrial combustion sources
• introducing low-emission cars and trucks
• burning gasoline reformulated to reduce VOCs, NOx, and other emissions.

Winds blow in different directions and in different speeds at different altitudes. Living on the Earth's surface, we are accustomed to what are known as Surface winds. Surface winds range from 0 - 1,000 feet in altitude. The winds associated with transport occur from 1,000 to 3,000 feet in altitude. The winds we experience at the surface may be moving at a different speed and direction than the winds at the "transport" level. This can create a problem when scientists attempt to track and especially regulate pollution levels.

Although this curriculum concentrates on ground level ozone, its causes and effects, it is important to note that ozone and its precursors are not the only pollutants that are transported by wind.

For example, a number of toxic air pollutants persist in the environment and concentrate in the food web, including toxaphene, a pesticide that is used primarily in the Southern U.S., and have been found in fatty tissues of polar bears and other Arctic animals thousands of miles away from any possible source. Lead and other trace metals have been measured in the air and rainfall at remote locations over the Atlantic and Pacific Oceans, great distances from likely sources. Core samples from peat bogs in the Great Lakes region show deposition of new releases of DDT. Since DDT is used only under special condition in the U.S., this toxic compound may be originating from sources as far away as Mexico or Central America. Fortunately, Mexico has also banned the use and production of DDT.

It is very important that people realize that when it comes to air quality, they have to worry about more than their own neighborhood. Since air pollution does not adhere to boundaries, it is important they we all contribute to the solution, on a local, regional and national level.

In this lesson, students will access wind data at the "transport" level and also access various pollutants' movements across the U.S. as well as other areas on Earth.

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