Invisible Air Pollution: I Don't Believe My Eyes!

Engineers design methods to measure invisible air pollutants and monitor air quality; they use these tools to measure emissions from vehicles and industry. For example, engineers design the equipment that is used when your car gets an emissions test. The equipment analyzes the substance discharged into the air by the internal combustion engine to determine whether the vehicle emissions include too many dangerous pollutants.

After this lesson, students should be able to:

• Identify the major types of invisible air pollutants.
• Describe how some invisible air pollutants affect our health.
• Describe how engineers interact with invisible air pollution.

The atmosphere is almost completely composed of invisible gaseous substances. Most major air pollutants are also invisible, meaning you cannot see or smell them. However, when large amounts of them are concentrated in areas such as cities, they can be seen as smog. Invisible air pollutants are among the most dangerous to our health. Refer to the associated activity What's Hiding in the Air? to develop students' understanding of the effects of invisible air pollutants with a rubber band air test and a bean plant experiment. Then follow with the second associated activity Visual Literacy: Tears in (Acid) Rain to help students learn how images are manipulated for a powerful effect and how a photograph can make the invisible (pollutants that form acid rain) visible (through the damage they cause).

The EPA set national air quality standards for six principal air pollutants (also referred to as criteria pollutants): carbon monoxide (CO), lead (Pb), nitrogen dioxide (NO₂), sulfur dioxide (SO₂), ozone (O₃) and particulate matter (PM). Four of these pollutants (CO, Pb, NO₂ and SO₂) result primarily from direct emissions from a variety of everyday sources. Particulate matter results from direct emissions, but is also commonly formed when emissions of nitrogen oxides (NO_x), sulfur oxides (SO_x), ammonia, organic compounds and other gases react in the atmosphere. Ozone is not directly emitted, but is formed when NO_x and volatile organic compounds (VOCs) react in the presence of sunlight.

Ask students to recall a visit to a gas station: Have they ever pumped the gas themselves or helped someone else do it? Have they ever taken a close look at the gas pump handle? Have they ever noticed that when they travel to other states or countries the pump nozzle may appear different? In Colorado (and many other places), the pump handles are equipped with a "rubber collar," designed by an engineer to prevent volatile organic compounds (VOCs, such as benzene) from escaping into the air while gas is pumped. This collar protects you from serious health effects that may result from inhaling fumes and also protects the environment from the smog caused by VOCs.

Create an idea web: Ask students to brainstorm a list of invisible pollutants. What effects do these pollutants have on us and our environment? What are some possible solutions for reducing these types of pollutants? (Refer students to the Common Air Pollutants Reference Sheet (PDF) or see the U.S. Environmental Protection Agency (EPA) Air Trends website at: www.epa.gov/airtrends/.

Ask students if they would like to add anything new to the idea web. Assign the Carbon Monoxide Emissions Worksheet (PDF) as homework.

Pre-Lesson Assessment

Discussion Topic: Ask students to recall a visit to a gas station. Have they ever pumped gas themselves or helped someone else do it? Have they ever taken a close look at the gas pump handle? Have they ever noticed that when they travel to other locations the pump nozzle may appear different? Why?

Post-Introduction Assessment

Idea Web: Ask students to brainstorm a list of invisible pollutants. What effects do these pollutants have on us and our environment? What are possible solutions for reducing these types of pollutants?

Lesson Summary Assessment

Idea Web Revisited: Ask students if they would like to add anything new to their idea web.

Informative Flyer: Have students create a flyer to inform other students, the school or their community about the presence of visible and invisible pollutants in the air. Include some of the ideas they generated in the idea web. Display these flyers in the classroom or the school's common area.

Homework

Worksheet: Assign students to complete the Carbon Monoxide Emissions Worksheet (PDF). Discuss findings during the next class period, paying particular attention to questions 3 and 6.

Take a field trip to a vehicle emissions testing site. Or, invite a speaker from a vehicle emissions testing site to speak to your class about how they measure the invisible pollutants from vehicles. What determines whether or not a car passes the inspection?

Air Trends. Updated May 4, 2004. U.S. Environmental Protection Agency. Accessed July 13, 2004. www.epa.gov/airtrends.

The Plain English Guide to the Clean Air Act, The Common Air Pollutants. Updated May 13, 2002. U.S. Environmental Protection Agency, EPA-OAQPS. Accessed July 13, 2004. www.epa.gov.