Air Quality - Lesson 6 : What Has Been Done About Air Pollution?

Day One 

1. Investigate the history of air pollution.

Note: Before starting this lesson, have students read the Winds of Change student resource. You may want to discuss answers to the questions at the end of the reading or assign them as homework. 

Have air pollution and air quality standards changed over time? Present the following time periods to the class—pre-civilization, preindustrial society, early industry, and growing cities—and solicit ideas about air pollution issues at those times. Supplement their ideas with a few highlights from An Introduction to Air Pollution History teacher resource. Mention that the first air quality regulations in the United States were implemented in the late 1800s. Summarize what happened in the twentieth century, noting the pollution episodes that caused deaths, the importance of the events in 1970, and the 1990 Clean Air Act Amendments.

How has Michigan addressed air pollution issues? Use the student reading, Winds of Change, as an introduction to the timeline regarding how Michigan has addressed air pollution. Lead the students in a discussion of how Michigan has changed and how policies affect citizens today. A PowerPoint presentation on the MEECS Air Quality CD has examples of historical air pollution. Explain that, although Michigan follows guidance from the U.S. Environmental Protection Agency, the State has been proactive in addressing air pollution through its own permit program and rules such as those involving air toxics. Show the transparency about Regulation of Air Pollution to illustrate the many facets of addressing air quality.

Note: More detailed timelines are available on the MEECS Air Quality CD. Students can create a timeline for display in class to illustrate what has happened regarding air pollution throughout history. For example, students could create pictures about a specific time period that could be linked together on a string to hang in the classroom.

2. Describe the quality of air in Michigan based on data.

Given all of the regulations, pollution control equipment, and pollution prevention, has air quality improved in Michigan? Challenge the students to answer this question with evidence. Brainstorm where they could find that evidence (government reports, environmental groups, etc.). Government agencies summarize air quality in documents such as the EPA National Air Quality Status and Trends Report and the MDEQ Annual Air Quality Report.

Recall that the students have learned about the six criteria air pollutants (carbon monoxide, sulfur dioxide, particles, lead, ozone, and nitrogen oxides) in previous lessons. Divide the class into six groups and assign one criteria pollutant type to each group. Ask each group to investigate and report on the levels of their assigned pollutant in Michigan’s air. Reference materials from the Status and Trends Report and the MDEQ Annual Air Quality Report are found on the MEECS Air Quality CD, along with additional teacher resources for this lesson from the MDEQ Air Quality Report.

When each group presents their findings to the class, urge them to go beyond “decrease” or “increase” and tell why they think there was a change (i.e., lead decreased since it was taken out of gasoline). This will involve linking their results to the discussion of general air pollution history and the article, Winds of Change.

3. Analyze trends in emissions of pollutants.

Is this the whole story? Show the students the composite graph on Michigan Stationary Source Emission Trends. Point out that these are industrial sources and what they are seeing are numbers compiled from emission inventories. In other words, these are what industry is contributing to the air. Have them draw conclusions from what they see and how that relates to the actual amount of pollution in the air.

Why doesn’t the graph show ozone as an emission? [Industries do not report ozone since ozone is formed as a result of photochemical reactions involving other pollutants such as VOCs and NOX.]

What types of emissions are not represented in this graph? [Students should recall that there are also mobile and area sources to consider. They may even mention natural sources.]

What information would be needed to estimate the contribution of mobile sources of pollution? [Number of vehicles, their age, miles driven, types of pollutants, and their amounts per mile.] States and the EPA work together to create emission inventories that are used for planning purposes.

Day Two

Note: Assign the student reading on Acid Deposition before beginning Day Two.

4. Explore acid rain as an example.

What is an acid? If your students are unfamiliar with pH, review the pH scale and do some of the following activities. In groups or as a demonstration, use red cabbage juice or pH paper to determine the pH levels of rainwater, melted snow, or vinegar (pH of 5.6 or less), tap water (pH 7-8), and a baking soda solution (pH 9-10). This can be done on a micro-scale by mixing 10 drops of cabbage juice with 10 drops of each of the test items. The color interpretation for the cabbage juice is: neutral = deep purple, acidic = red, and basic = blue.

Mix baking soda, chalk, or crushed limestone with the acidic substance and cabbage juice to illustrate buffering capacity (ability to neutralize acid).

To illustrate the effects of an acid on materials, place two pennies older than 1983 in a petri dish and put tap water on the “Lincoln Memorial” side of one coin and a carbonated beverage or vinegar on the “Lincoln Memorial” side of the other coin. Observe what happens to the coins. In fact, monuments in Washington, DC, such as the Lincoln Memorial, are showing effects of acid rain. The penny experiment can be continued for another week by placing some coins in tap water and others in vinegar.

What is acid deposition? Based on their reading, engage the students in a discussion of acid deposition: What is it? What is the cause? How can emissions in one region affect other regions? What are the effects? Consider showing the PowerPoint on acid rain from the Maine Department of Environmental Quality that is included on the MEECS Air Quality CD.

Explain the rules and have groups play the Cap and Trade game followed by the Acid Rain game. As a class, discuss what was learned from the games.

5. Tying it all together.

Has the Acid Rain Program worked? Show the Is the Acid Rain Program Working? transparencies. Have students draw conclusions from the graphs. An increase in pH correlates with a decrease in emissions. This means that the rain has become less acidic over time. If you have access to a projection system, show the PowerPoint from the MEECS Air Quality CD that has the animated pH maps (or see the maps online at, which is the National Atmospheric Deposition Program site). These maps show that acid deposition is most pronounced in the eastern part of the United States, but the acidity has been decreasing over the years.

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