Science puzzle

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Across
  1. 3. synthetic organic materials
  2. 4. haze
  3. 5. population decline
  4. 8. pollution
  5. 9. heavy smoke
Down
  1. 1. CO
  2. 2. can’t point to source
  3. 3. point to source
  4. 6. insect spray
  5. 7. indoor pollutants