5. Air Quality Index CO - Carbon Monoxide NO x - Nitrogen Compounds SO 2 - Sulfur Dioxide O 3 - Ozone PM - Particulate Matter

9. Why worry about air quality?

10. Ambient (outdoor air pollution) in both cities and rural areas was estimated to cause 3.7 million premature deaths worldwide per year in 2012; this mortality is due to exposure to small particulate matter of 10 microns or less in diameter (PM 10 ), which cause cardiovascular and respiratory disease, and cancers.

14. What causes poor air quality? What are the factors that make certain areas prone to poor air quality? Geography Population Industry Weather