Where does the pollution in your air come from? Q22 of The Big Here Quiz

According to the Ontario Ministry of the Environment, "it is estimated that more than 50 per cent of Ontario's ground-level ozone and fine particulate matter come from the U.S."

The MOE also looks at the point of origin of air pollutants from Ontario. From its 2006 Air Quality in Ontario report (pdf), the pollution in our air comes from:

Ontario Volatile Organic Compounds Emissions by Sector
- 22% General Solvent Use
- 22% Other Transportation
- 16% Other Industrial Processes
- 13% Road Vehicles
- 10% Printing/Surface Coating
- 9% Miscellaneous
- 8% Residential

Ontario Nitrogen Oxide Emissions by Sector
- 38% Other Transportation
- 27% Road Vehicles
- 12% Other Industrial Processes
- 9% Utilities
- 6% Cement and Concrete
- 6% Miscellaneous
- 2% Smelters / Primary Metals

Ontario Particulate Matter (2.5) Emissions By Sector
- 32% Residential
- 30% Other Industrial Processes
- 20% Transportation
- 10% Smelters / Primary Metals
- 5% Miscellaneous
- 3% Pulp and Paper

Ontario Carbon Monoxide Emissions By Sector

- 46% Road Vehicles
- 38% Other Transportation
- 8% Residential / Miscellaneous
- 5% Other Industrial Processes
- 3% Smelters / Primary Metals

Ontario Sulphur Dioxide Emissions by Sector
- 48% Smelters
- 22% Utilities
- 10% Petroleum Refining
- 9% Other Industrial Processes
- 5% Cement and Concrete
- 3% Transportation
- 3% Miscellaneous


Ha! But when I went to look at the other answers to this question, I noticed this comment from one of the creators of the Big Here Quiz:

When we first conceived of this question, we meant what "air mass" or "regional weather front" brought the pollution. So New York gets it from Detroit; the Grand Canyon gets it from LA, etc. It's seasonal too. Sorry for the confusion between source (cars, etc.) and air masses.

Hmm. There was an earlier question, Where do storms usually come from? Would the answer to that question be different from, Where do your air masses come from? That's the trouble with profound ignorance: you don't know when a difference makes a difference...