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What's The Air Forecast?

Activity 4 (Explain): The Criteria Air Pollutants

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Activity Overview

Activity Summary

In this activity, students learn about the 6 Criteria Pollutants defined by the Clean Air Act and the EPA, and they are introduced to sources of these pollutants. They  use this information to think about what pollutant could be the cause of the haze in their pictures. Then they learn to look up current and historical AQI data to identify the pollutant that caused the haze in their picture.

Activity Objectives & Materials

Approximate Time: 60 minutes


  • Students will define air pollution

  • Students will know there are different kinds of air pollution, and some are more important for us to consider

  • Students will identify the pollutant that caused the Code Red Day in DC



  • Computer & projector

  • Air pollution information stations (printed & cut)

  • Sources of air pollution signs

  • Scissors (optional for foldable)


  • The Criteria Pollutants (foldable or regular) – see note below

  • Reading: The Region's Air Quality Reached Unhealthy Code Red Levels on Monday

Foldable handout (recommended): To use the foldable notes sheet, print it double-sided (flipped on the short side). See activity directions for folding.

Standards Connection

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

SEP: Obtaining, Evaluating, and Communicating Information



How would you define air pollution?

  • After students have answered the warmup question for themselves, have them share ideas while you record on chart paper or on the board. Using their ideas, help them to create a class definition that everyone can agree on. Try not to use the word “pollution” in the definition. Sample definition: “Air pollution is things in the atmosphere that can be harmful to people.” Put the definition in a prominent place in the classroom for the rest of the investigation. You may choose to revise it with students at the end of this activity or at any time during the module. The point of this warmup is less to have a perfect definition of air pollution, and more to get students thinking about what air pollution is and what they already know about it


1. Frame the Activity

Remind students that at the end of the last activity, they decided that air pollution could be the cause of the haze in their photographs, but they weren’t sure. In this activity, they will investigate different kinds of air pollution to see if they can figure out what specific kind of pollution could be causing the haze in their pictures.

Step 1

2. Types of Air Pollution

Hand out the Types of Air Pollution graphic and put it up on the screen. Have students start by looking at the top row. Tell them that these are all different kinds of air pollution. See if students have ever heard of any of them. They may be familiar with ozone, carbon monoxide, or lead. Next have students look at the middle row. They are likely already familiar with the phases of matter. Tell students that air pollution doesn’t need to be a gas. Ask them what other liquids they know that might be in the air (water) or what kind of solid (dust). Note: The goal of this lesson is begin building students’ background knowledge on air pollution types, sources, and trends. It is not necessary to go into depth on the types of air pollution at this time.  

Types of Air Pollution Graphic.jpg

3. Identifying the 6 Criteria Pollutants

Tell students that the United States has a government agency called the Environmental Protection Agency (the EPA) that is responsible for monitoring and preventing pollution. In 1970, a law was passed called the Clean Air Act. That law requires the EPA to monitor 6 particular air pollutants. Ask students why they think these 6 pollutants were chosen (they can be harmful to human health, and they were a big problem when the law was passed in 1970). Tell students that they will learn more about the Clean Air Act later in their investigation.


See if students can identify the 6 criteria pollutants using the graphic: sulfur dioxide (SO2), nitrogen dioxide (NO2), carbon monoxide (CO), ozone (O3), particulate matter (PM), and lead. If students have done Module 1, they will already be familiar with ozone, but the others are probably new to them. They will learn more about ozone in this module, and particulate matter in the Module 3.

Step 4

4. Where Does Air Pollution Come From?

Hand out “The Criteria Pollutants” notes sheet (either the foldable or the regular sheet) to students. If you are using the foldable (recommended), have them fold the notes sheet using the directions below. Tell students that they will be doing some research on the criteria pollutants to learn more about them and see if they can identify which pollutant caused the haze in Washington D.C. on July 9th. For each pollutant, they will write down a few details of what it is, and where it comes from. If they are using the foldable, they also have space to write down clues as to whether they think the pollutant could be the cause of the Code Red Day and why.

Using the FoldableHave students hold the sheet with the solid lines side facing up. Then have them fold the left and right sides into the middle so they meet at the center. You can also have them cut the dotted lines on the front (just to the fold) so they can open the flaps. They can then tape or glue the foldable into their notebooks if they choose. Make sure students know how to use the foldable to take notes.

Divide students up into six groups, and give each group copies of the pollutant information for one station. Have them take notes on that pollutant on their notes sheet. After all groups have finished, have them move to the next station to take notes. Repeat until all students have visited each station and taken notes.

ModificationTake notes on one of the criteria pollutants together as a class before students begin the station work.

ModificationInstead of having students rotate from one station to the next, have them pass the materials to the next group.

5. Summarizing Criteria Pollutants and Sources

Have students return to their original seats. Have them review and summarize what they learned together as a class by asking the questions below:

  • What did you notice about the sources of different air pollutants? (they tend to be the same or similar)

  • What are the major sources of most of these air pollutants?

    • Power plants (SO2, NO2, O3, PM)

    • Vehicles (NOx, CO, O3, PM)

    • Industrial/Chemical plants (SO2, O3, PM, Lead)

    • Natural sources like forest fires (PM, NO2)


As students name these sources, put up the corresponding “Sources of Air Pollution” poster on the wall to go with it.

  • Based on your research, what pollutant do you think could be causing the haze?

    • At this point, students should be able to identify ozone as the culprit (or possibly PM). It occurs during the summer months, and it looks like a “dirty fog”. Other pollutants are the wrong color or colorless (NO2, SO2, Lead, CO) or are present in the winter (CO). PM could definitely be a possibility, but because ozone is referred to specifically by color, it is the better choice.


Don’t tell students whether they are right or wrong, but let them know they’ll find out the truth in a moment.

Power Plant Poster.jpg
Transportation Poster.jpg
Manufacturing Poster.jpg
Natural Sources Poster.jpg

6. Story of a Code Red Day

Tell students that on June 10, 2018 (the day after the Code Red Day from our picture) there were several news stories written about it. They are going to read a summary of one of those stories to see if they are right about their hypothesis. Hand out the double-entry journal article: Region’s air quality reached unhealthy Code Red levels on Monday. If necessary, review with students how to complete the double-entry journal, and provide support while they read and answer the questions.

Afterwards, review students’ responses to the questions, and celebrate that they were able to figure out what was going on in the picture.

Differentiation: Read the article out loud with students and give them time to answer the questions along the way.

7. Return to the Investigation Tracker

Have students take out their Investigation Trackers, and add new information to show what they learned about the cause of the haze and the Code Red Day. They should add information about what the pollutant was (ozone) and where ozone comes from. They can get this information from their notes sheet.

8. Formative Assessment

Go back to your definition of air pollution from the warm up, and add additional details to include what you’ve learned today about the criteria pollutants and where they come from.

  • Additional details students might add include the names of the criteria pollutants, the main sources of the criteria pollutants (in general) and why they were chosen as important.


Modification: Instead of having students complete this formative assessment, you can use their Investigation Trackers as the formative assessment for this lesson

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