Danger In The Air!
Activity #8: Particulate Matter in the Atmosphere (Optional)

Purpose: To collect and look at particulate matter that is in polluted air.

Particulates are small solid particles and liquid droplets that are suspended in the air. Collectively, these particulates are called aerosols. Natural sources of particulates include dust, volcanic ash, and pollen. The dispersal of airborne particulates in the atmosphere because of human activity has become a concern because of health related problems to living things. Human sources of particulates include dust from plowing and overgrazing of arid land, mineral dust from mining and smelting, coal and oil burning power plants, ash and smoke from industries, vehicles, particularly those that burn diesel fuel, and burning wood in fireplaces and wood-burning stoves. Liquid particulates include sulfuric acid, PCBs, petroleum, and pesticides. Industrial processes account for 40% of the 6.6 million metric tons emitted in the United States each year. Cars account for 17% of the particulates.

Particulate sizes are measured in microns. A micron is one-millionth of a meter, which is also one-thousandth of a millimeter. "Fine dust" is less than 100 microns in diameter, "coarse dust" or "grit" is greater than 100 microns, and "fumes" are between 0.0001 to 1 micron in size. Small particulates, .1 micron (0.001 mm), can remain in the atmosphere for several months or even years. Winds can carry the particulates thousands of miles. Rain and snow help to clear particulate matter from the atmosphere.

Particulate air pollutants can be harmful to human and animal life if inhaled. Our body naturally can filter out large particulates with the hair in our nose, mucus in our throat, and cilia in our lungs. Small particulates can carry poisonous substances into our lungs and cause breathing problems and lung damage.

Observation of Particulates

Materials: Flashlight or slide projector.


Tap a chalk board eraser below the light to show how the dust is suspended in the air. Turn the lights on while there is a large amount of "dust" visible in the light beam. Notice the particulates are less visible in the increased light.

Summarize what you learned about particulates--where are they, what do you think causes them, and how abundant are they?

Collecting and Observing Particles in the Air

Materials: Posterboard or thin cardboard, scissors, ruler, transparent tape, string, hole punch, magnifying glass or dissecting microscope, analytic balance.


  1. Make two "Air Strips" per person--one to hang at school and one at home.

  2. Mass the air strips before placing the strips around school and home. Note: you need a VERY sensitive balance for this part.
  3. Hang the strips around the school, both inside and outside. You may hang strips in halls, classroom, science labs, where buses let off students, parking lots, on buildings, on trees, etc. Provide tape or string to hang the collectors.
  4. Hang a "control strip" in a closet or other protected area.
  5. Hang an Air Strip at home.
  6. Leave the collectors for a week.
  7. Record the weather conditions during the week.
  8. Collect data: Identify the types of particulates using a magnifying glass or dissecting microscope. Estimate the percent of the area covered with particulates and the relative proportion of each size of particulates. Mass the air strips to determine the gain in mass.
  9. Organize data: Put all data into a table. Include the location of the Air Strip, data from the Control Strip, and specific findings.

Analysis (answer on a sheet of paper)

Are there differences in the particles based on where the air strips were placed?

Which collectors had the most particulates and why?

What variables or conditions might affect the amount of particulates collected on a collector?

What are some health hazards associated with the particulates you collected?

How could particulate pollutants dispersed by human activity be reduced?

[Live from Earth & Mars]__________________________________________________