Grades 9-12

Unit 1, Lesson 2

Pounds of Pollution: What's in the Air and How Bad Is It?


  • learn techniques to visualize the amount of air pollution emitted by a car each year;
  • learn that air pollutants emitted by vehicles have weight, or mass; and
  • calculate the weight of various pollutants.

Air pollution is often referred to in terms of pounds. We know air has weight, but how much of a gas is a pound? Using two-liter bottles and calculations, this lesson helps students understand the "weight" of automobile pollution and helps raise awareness about the differences between pollutants and the quantity of pollutants emitted by cars versus sport-utility vehicles (SUVs).


English, Language Arts and Reading

  • 13, 13E


  • Integrated Physics and Chemistry: 3
  • Biology: 2A-D, 3A-D, 12A
  • Chemistry: 7A
  • Geology, Meteorology, and Oceanography: 9B-C


It is recommended that each student bring a clean, empty two-liter soda bottle to school, stripped of its label.

Teacher Preparation:

The average American contributes 20 tons of CO2 to the atmosphere each year.

Air pollution is a difficult concept to grasp. We often can't see it! Yet cars emit many different air pollutants. (See "A Car Does What?" box in the directions below.) Air pollution is often referred to in terms of pounds. You know that air has weight, but how much of a gas is a pound? By displaying the soda bottles and attaching a label that informs passersby that the bottles represent one pound of carbon dioxide (CO2), the awareness of a school and community can be significantly raised.

This lesson contains a number of air pollution terms that students may not be familiar with, including carbon dioxide (CO2), carbon monoxide (CO), hydrocarbons, and nitrogen oxide (NOx). These terms are defined and summarized below. Presenting these terms and definitions may prove a helpful introduction to this lesson.

Criteria Pollutant: Nitrogen Oxides (NOx)
Nitrogen gas comprises about 80 percent of the air. At high temperatures it can react with oxygen, forming different gaseous compounds. Collectively they are called nitrogen oxides. These gases are formed when fossil fuels are burned in cars, power plants, and factories. These gases are also an ingredient in making ground-level ozone. They are a precursor to acid rain, which can affect terrestrial and aquatic ecosystems.

Health and Other Effects of Nitrogen Oxides
Nitrogen oxides affect human health in ways similar to ozone. They include:

  • a measurable decrease in lung function, especially in asthmatics;
  • lung irritation;
  • increased rates of lung disease; and
  • destroyed lung tissue, leading to emphysema.

Nitrogen oxides can also:

  • seriously injure vegetation at certain concentrations (bleaching or killing plant tissue, causing leaves to fall, and reducing growth rate);
  • deteriorate fabric and fade dyes;
  • corrode metals; and
  • reduce visibility.

Criteria Pollutant: Particulate Matter
Particulate matter can consist of solid matter or liquid droplets from smoke, dust, fly ash, and condensing vapors. There are two types of particulate matter: PM10 and PM2.5. These numbers relate to the monitoring criteria and size of the particles. The 10 and the 2.5 are "microns," so PM10 means particulate matter size 10 microns or smaller. PM2.5 means particulate matter size 2.5 microns or smaller. PM10 has been studied and monitored for a long time, but PM2.5 is newer. This study will better protect human health since the smaller the particle, the deeper it can go into your lungs.

Particulate matter can be either man made or naturally occurring. Natural sources include soil, bacteria and viruses, fungi, molds, yeasts, pollen, and salt particles from evaporating seawater. Human sources include soot from smokestacks, dirt kicked up by vehicles on gravel or dirt roads, dust from bulldozing and mining, smoke from burning wood, and gasoline and diesel exhaust.

Health and Other Effects of Particulate Matter
Over 99 percent of inhaled particulates are exhaled or expelled from the body by coughing. The remaining percent of particles are so small that they can get lodged in the lung capillaries and alveoli, causing shortness of breath and strain to the heart, which must work harder to compensate for oxygen loss. Seniors, children, and those with lung or heart disease are more susceptible.

Some particulates may be poisonous if inhaled or absorbed, damaging organs like the kidneys and liver. Poison-laden mucus can damage the gastrointestinal system if swallowed.

Irritating odors are generally associated with particulates, such as the smell of diesel exhaust or trash burning.

Particulate matter can also:

  • corrode metals and building facades;
  • cover leaf surfaces of crops, trees, and shrubs, injuring or inhibiting growth; and
  • reduce visibility.

Criteria Pollutant: Carbon Monoxide
Carbon monoxide (CO) is a colorless, odorless, and tasteless gas. It is a by-product of incomplete combustion. In other words, it is emitted when wood, gasoline, coal, and fossil fuels are burned incompletely. It is also emitted naturally when plants decay. Carbon monoxide can temporarily accumulate at harmful levels, especially during the calm, cool days of winter and early spring. That is when fossil fuel consumption is at its peak and when the gas is most chemically stable, due to low temperatures.

Sources of Carbon Monoxide

  • automobiles (responsible for more than two-thirds of the man made CO in the air; levels are especially high in traffic-congested cities due to the number of cars and the ability of tall buildings to trap the gas and keep it from blowing away);
  • home/building heating;
  • volcanoes, thunderstorms, and forest fires;
  • vegetation during certain growth stages; and
  • the chemical transformation of methane, a gas emitted from decaying plants (carbon monoxide from natural sources usually dissipates quickly over a large area, posing reduced risk to health).

Health Effects of Carbon Monoxide
Carbon monoxide reduces the amount of oxygen distributed throughout the body by the blood stream. Once carbon monoxide enters the blood stream, it attaches to hemoglobin, the substance that carries oxygen to the cells. The ability of CO to attach to hemoglobin occurs 200 times more readily than it does for oxygen. Low levels of oxygen and high levels of carbon monoxide:

  • affect the nervous system;
  • weaken heart contractions, lowering the amount of blood distributed to body parts;
  • reduce athletic performance;
  • cause fatigue;
  • cause shortness of breath and chest pain for people with heart disease; and
  • lead to irritability, headaches, rapid breathing, blurred vision, lack of coordination, nausea, dizziness, and impaired vision in normally healthy people.

Young children, elderly, smokers, and those with pre-existing lung and heart diseases are more susceptible to carbon monoxide's negative health effects.

Greenhouse Gases
Carbon dioxide, methane, and nitrogen oxides are the major greenhouse gases. These gases build up in the upper atmosphere and may lead to global climate change, or "global warming."

Carbon dioxide emissions come from fossil fuel combustion from transportation and energy use.


  1. Calculate the volume of one pound of whatever air pollutant you are interested in by using the following equation:

    There are 454 grams in a pound. The next step is to find out how many grams of your pollutant are in a mole. This number can be calculated using values from the Periodic Table of the Elements. Add the grams per mole for each compound. For example, one atom of oxygen is 16 grams per mole, and carbon dioxide is 12 grams per mole. This totals 44 grams per mole of carbon dioxide molecules (CO2 is two oxygen atoms plus one carbon atom). For your convenience, we have listed the weights of carbon dioxide, carbon monoxide, and nitrogen dioxide—three pollutants given off by cars. Insert these values for "X" depending on the pollutant.

    CO2 = 44 g
    CO = 28 g
    NOx = 46 g

    There are 22.4 liters in a mole. Multiply by this number of liters and you have converted the pound of gas into an equivalent number of liters.

  2. Calculate how many two-liter bottles are needed for the display. Use the following equation:

    volume of 1 lb of the pollutant / 2 liters = total bottles

    For example, if you are dealing with CO2, which you have calculated to be 231 liters per pound, divide 231 by 2. This tells you that you need 115.5 bottles to represent one pound of CO2.


    In one year, a new 2001 model small car, traveling an average of 12,513.2 miles per year, getting 28.7 miles to the gallon, using 436 gallons/year, spews the following into the air we breathe*:

    • 8,725 lb of carbon dioxide (CO2);
    • 193 lb of carbon monoxide (CO);
    • 5.7 lbs of hydrocarbons
    • 18 lb of nitrogen oxide (NOx); and
    • smaller amounts of benzene, formaldehyde, volatile organic compounds, and other toxic materials.

    Larger vehicles, like popular SUVs, can produce more than twice as much pollution as a small car!

    Note: Cars emit several different nitrogen oxides. If you want to demonstrate how much of a particular nitrogen oxide weighs per pound, you would have to make a separate calculation for each kind of nitrogen oxide using their different atomic masses.

    *Figures from "Tailpipe Tally," Environmental Defense Fund, on the web at

    Answer Key
    Number of two-liter bottles:
    CO2 = 115.5 bottles
    CO = 181.3 bottles
    NO2 = 110.5 bottles


Student Questions

  1. How many bottles would be needed to represent the hypothetical car's (see box) yearly CO2 and CO emissions?
  2. Calculate how many bottles would be needed to represent the amount of CO2 and CO your class members contribute to the atmosphere during one school week. Use the hypothetical car amounts, above.
  3. According to Wisconsin Department of Natural Resources calculations, the number of tons of NOx emitted on a hot summer day in southeastern Wisconsin* is about 409. If this amount were made up entirely of NO2, how many soda bottles would this be?

    * "Southeastern Wisconsin," above, refers to the following 11 counties: Door, Kenosha, Kewaunee, Manitowoc, Milwaukee, Ozaukee, Racine, Sheboygan, Walworth, Washington, and Waukesha.

Student Answers

  1. There are 363 liters per pound of CO, multiplied by 193 lb emitted by the average car per year, which equals 70,059 liters. There are 231 liters per pound of CO2, multiplied by 8,725 lb emitted by the average car per year, which equals 2,015,475 liters. CO = 35,029.5 bottles. CO2 = 1,007,737.5 bottles.
  2. Answers will vary.
  3. Multiply the 409 tons of NOx emitted by 2000 lb in a ton, and you have 818,000 lb of NOx. There are 221 liters per pound of NO2. Multiply this by 818,000 lb, and you have 180,778,000 liters. This is 90,389,000 soda bottles worth emitted on one summer day in southeastern Wisconsin.


Web Sites

    Tailpipe Tally, Environmental Defense

Source: Al Stenstrup, Education Outreach; Mittsy Voiles, Air Education Specialist; Tammie Niffenegger, Port Washington High School, Wisconsin,

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