Blue arrow shows the upper winds that travel from the west to the east or northeast. Winds travel from the mid-west to the northeast. In addition, a copper-nickel smelter in Sudbury, Ontario, just north of Lake Huron is the most significant sulfur oxide source in Canada. The winds may also carry the sulfur oxide clouds to the Northeast in the U.S. where it may be converted to acid rain.
Interesting how acid rain transportation travels long distances through wind and eventually break down as acid precipitation. Though it leads to cross-border environmental damage, it proves to not only be a local issue but a regional and international concern that requires environmental policies and regulations to mitigate its widespread ecological and economic effects.