Over the last 15 years, major progress has been made in reducing sulphur dioxide, one of the key pollutants which forms acid rain. Since 1980, eastern Canada has cut its emissions of sulphur dioxide by more than half.
Reductions are also underway in the United States.
Yet despite this progress, the latest scientific studies show that the recovery of natural ecosystems has been much slower than anticipated, and that our actions will still not be enough to protect our most vulnerable lakes and forests. The main sources of these pollutants are coal-fired power plants, nickel and copper smelters, and motor vehicles. While airborne, it reacts with water vapour to form sulphuric acid. Similarly, nitrogen oxides, released mainly during high-temperature fuel combustion, form nitric acid. These pollutants can stay in the air for days, sometimes travelling thousands of kilometres.