Across:

1. Volcanoes, forest fires and plant & animal decay.
2. The presence of contaminants in the air in high enough concentrations to be harmful.
3. A major source of pollution in our air today.

Down:

4. Odorless and colorless gas emitted by cars and from cigarette smoking.
5. Any harmful chemical emitted into the air, water or soil.
6. A metal added to some gasoline that is emitted into the atmosphere as the is burned.
7. Small droplets or particles of fly ash, smoke or dust that are suspended in the air for a long time.
8. A gas in the upper atmosphere that protects the earth from the damaging rays of the sun.
9. A gas that can be found in your home. You cannot see, smell or taste it

Answers