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What's The Air Forecast?

Activity 7 (Explore): Air Pollution Trends and

the Clean Air Act

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Activity Overview

Activity Summary

In this activity, students use graphs based on EPA data to analyze national and regional trends in the 6 Criteria Pollutants defined by the Clean Air Act. In the second half of the activity, students learn more about the Clean Air Act and how humans can have a positive impact on the environment.

Activity Objectives & Materials

Approximate Time: 2 class periods (approx. 90-120 minutes)


  • Students will interpret graphs to determine how air quality in the US has changed over time

  • Students will use the Clean Air Act to discuss whether humans have a positive or negative impact on the planet



  • Computer & projector

  • Speakers (for video)

  • Pollutant trends graphs


  • Air Pollution Summary Sheet

  • How Much Pollution is Too Much? (optional)

Standards Connection

DCI: ESS 3.C – Human Impacts on Earth’s Systems

SEP: Obtaining, Evaluating, and Communicating Information

CCC: Patterns



Show students the map of the DC/ Baltimore/Philadelphia area below and tell them that it is a map of the area on the Code Red Day (July 9, 2018).

AQI Map July 9 2018.jpg


  1. Where is the AQI unhealthy or unhealthy for sensitive groups on this map? (between Washington and Philadelphia)

  2. Why do you think the AQI is bad in this area (because there are a lot of people in DC, Baltimore, and Philadelphia; because there is a lot of transportation between these cities)


If students struggle with Question 2, have them consider what the land might be like between Washington and Philadelphia as opposed to western Maryland. Is it farmland? Are there a lot of roads? Are there a lot of people?


1. Frame the Activity

Ask students what they learned in the last activity about how ground-level ozone air pollution has changed in the area over the last 25 years. They should recall that air quality in the region is generally getting better. Next, ask them if they think that’s true for other pollutants or other parts of the country. Why? They may have reasons to think that air quality has improved or declined around the country, so give them time to share their ideas. Finally, tell students that during their activity today, they are going to look at a series of graphs to see how air quality has changed over the last 40 years, and then they will learn about why that change has happened.

Step 1

How Much Pollution is Too Much? (optional Literacy & Math extension)

If you have time, consider using this literacy and math extension here. It will help build students’ background knowledge about the EPA and the pollution limits, and also improve their understanding about scale, quantity, and proportion. The directions are below, and the handout is at the end of the activity.


Hand out the reading “How Much Pollution Is Too Much?” Provide a reading strategy to help students identify key ideas and questions they have. For example, have students highlight the key ideas, and put a question mark by things they want to ask about. When students are done reading, have them share key points, and use peer discussion to help answer their questions.


Animated Part-per-million (optional). Show students the animated video “How to Visualize One Part Per Million”:


Review the table of pollutants and limits with students, and then have them do the first math problem. Support as necessary in comparing the fractions. Then read the second problem together. Have them setup the problem on their own or with a partner, and then have them do the calculations on their own. Review together as a class.

2. Air Pollution Over Time

There are two different options for how to do this activity, based upon time, logistics, etc. In both options, student groups will look at graphs of how the criteria pollutants have changed over time, and answer a few questions about each graph. Adapt the directions below based upon which option you choose.

  • Option 1 (Stations). Student groups travel to each station, study all pollutants, and answer all the questions themselves.

  • Option 2 (Expert Groups). Each group studies one pollutant, answers the questions for their pollutant, and then each group presents their answers to the class so all groups get all the answers.

Tech integrationThe air pollution trends graphs are easily accessible on the EPA website. Instead of printing out the maps, have students look at them online using the EPA’s air trends page:

ModificationInstead of stations, keep materials in folders and pass the folders from group to group instead of having students move.

Hand out the air pollution summary sheet. The sheet has the six criteria pollutants listed, and a few questions to answer about each one:

  • What is the EPA limit for this pollutant?

  • How has the amount of this pollutant changed over time?

  • Is this pollutant still a problem where we live? (NE region or SE)


Display the sample graph below so all students can see it, and go over the information it contains. The important things to point out are:

  • The National Standard (dotted line). This is the same as the EPA limit. Make sure to show students how to read the y-axis for this measurement

  • The average for all places where they collected data (the white line)

  • The range that includes 80% of all sites (the blue area)

EPA Criteria Pollutants sample graph.jpg

Teacher TipFor more information on how to interpret the trends graphs, go to:

The graphs that students will be using also have a statistic that describes the trend over time.

If you think it is necessary, you can use the ozone trends graph as an example for students.


Review the directions with students for how they will collect and/or share their data. When you are confident that students understand how to read the graphs, and fill in their summary sheets, release them to begin their research. Most of the information students get from the graphs is straightforward, but they may need help using the scales if they have decimals.


When students have finished all stations, or presented their research to the rest of the class, begin the summarizing section below.

Modification: The trends graphs at the bottom of each page show the trends for the NE region and the SE region of the US. Graphs for all other US regions are available from the EPA pollution trends pages:

Step 4

3. Summarizing Patterns In Air Pollution Trends

Ask students to consider their predictions from earlier in class. Were they right or wrong? Most students are surprised to find out that air pollution has dropped significantly in the last 40 years. There are a variety of other summarizing questions you can ask students such as:

  • Which pollutant dropped the most? (lead)

  • What pollutants are still the biggest problems (ozone and PM)

  • Do these graphs mean that air quality is good everywhere? (no – use this as an opportunity to point out that the blue line shows were 80% of the data fall. 10% of the data sites had pollution above the line, so there are still some places where pollution is bad – we call this hyperlocal pollution)


Feel free to add your own summarizing questions to this list. This is also a good time to revisit the class definition of “air quality” if necessary to include the idea that air has better quality when it is below the EPA limit.

4. The Clean Air Act

Display one of the air pollution graphs (such as Carbon Monoxide below) and ask students why the think air pollution dropped so dramatically in the United States.




Students may remember that you mentioned The Clean Air Act in Activity 4, or they may say that the EPA sets rules for how much pollution can go into the air. Remind students that their graphs began in 1980. Based on the trends in the graph, what do they think the air pollution was like in 1970 (it was even worse). Ask students what they would have done if they were alive in 1970 and the air was very unsafe to breathe? They may say things like they would protest or stay inside. Tell students that people in the 1960s were very upset about air quality and water quality, so they decided to do something about it.

Tell students that you are going to show them a video about what people did to fix the problem of air pollution. While they watch, they should look for things that people did to have a positive impact on the planet. Show students the video: “The Clean Air Act of 1970

Note: some parts of the video will likely be over students’ heads, but there are some powerful images and concepts that make it worthwhile.

EPA CO graph.jpg

The US Without the Clean Air Act: This short video simulates what US cities would be like without the Clean Air Act. It can be a powerful visual to show students about how we can have both a positive and negative impact on the planet:

Additional media: This old video about air pollution (made in 1962) shows just how bad the air pollution actually was:

Connections to Current Events: Students may make connections between protests that they see in the video with protests that they see today (climate change, BLM, etc.). These are important and valuable connections for them to see about how people can advocate for change. With this said, be mindful of the fact that some of these movements are very different, and require thoughtfulness when leading the discussion.

After the video, ask students what things they heard or saw people doing to have a positive impact on the planet. Some things they may say:

  • They held protests (dressed up, made signs, marched, etc.) and held the first Earth Day

  • They wrote about pollution (ex. Rachel Carson’s book Silent Spring)

  • The passed laws to protect the environment (the Clean Air Act)

  • They worked together

If you find it useful, you can also choose to show students this graph, which shows how successful the Clean Air Act has been, despite the fact that we drive more, use more energy, and have a larger population than we did in 1970.

EPA growth areas graph.jpg

5. Do Humans Have A Positive or Negative Impact?

Now that they have learned about air pollution, trends in air quality, and the Clean Air Act, ask students if they think humans have a positive or negative impact on the environment. Have them start by turning to a partner to discuss what they think. There are many good points to be made on each side. Humans have done a lot of environmental damage, but we have also done a lot to clean up the environment. After students have been able to discuss with a partner, bring the whole class back together to discuss. Allow students to drive the debate, but use questioning to push their thinking.

Suggestion: To have this discussion, you may choose to have students form a circle so they can talk directly to one another and debate their positions.

You may also want to display the air quality map at IQAir: to remind students that the US air quality used to be like it is now in China and India. The Clean Air Act changed that. What do they think people in China and India are doing right now to begin cleaning up their air?

Extension: This discussion about whether humans have a positive or negative impact on the environment can easily be extended if you have the time to dig deeper. For example, is it considered a positive impact if we simply stop doing something that has a negative impact? What about conservation efforts? Consider what source materials students might need to more fully explore this issue.

6. Return to the Investigation Tracker

Have students make notes in their investigation tracker based on big ideas they learned during this activity. Key takeaways:

  • Air quality in the United States has improved a lot since 1980.

  • The Clean Air Act was a very important law that helped the US to clean up the air

  • People can have positive and negative impacts on the environment by polluting, or by working to stop pollution

7. Formative Assessment

Is the air in the United States safe to breathe? Use the research you gathered about air pollution during class today to support your answer.

  • Student responses will vary, but the important thing to note is how students use the data from the graphs to support their answers. For example, they may say no because ozone is still high, but they may also say yes because most of the criteria pollutants are below the national standard. Students may also say it is safe in some places but not others.


Homework Idea: From Air, Air Everywhere curriculum (Wisconsin): Have students interview an older family member (ex. grandparent) about their experience with air pollution as a child. If students don't have a grandparent to ask, connect them with an older staff member, or have them reach out to someone else in their community. Then have students compare their interview answers with their own perspectives to see how times have changed. Students can then share what they learned with their classmates.

Find the activity and interview questions here titled “Clean Air – How Far We’ve Come”,Air,EverywhereActivity5CleanAir-HowFarWeveCome.pdf

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