Retrieval - air pollution

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Across
  1. 2. What gas do animals breathe?
  2. 5. What gas makes up most of healthy air?
  3. 6. Air pollution can be caused by cutting down ...
  4. 7. What pollutant is produced when volcanoes erupt?
Down
  1. 1. What pollutant is produced from farming animals?
  2. 3. What is the name of tiny pieces of plastic that can float in the air?
  3. 4. Having more people in each car produces _____ pollution