Acid rain, In 1982, Canada alleged that pollution blown in from the north-eastern United States had killed all the fish in 147 Ontario lakes and was depleting salmon stocks in Nova Scotia. With that, the phenomenon of acid-rain entered the international consciousness.

Officially known as acid deposition, acid rain is capable of harming waterways, trees, crops , buildings and human beings. Sulphur dioxide and oxides of nitrogen are the main culprits and these gaseous pollutants are formed when fossil fuels are burned in cars and power stations. When dissolved in water, these gases form sulphuric and nitric acids and fall to earth as precipitation or dust. Scandinavian concerns over acid rain have been present since the 1950s, when studies linked it to declining freshwater fish populations. In the 1970s acid rain was also blamed for the widespread damage to West German forests.

While the US, under President Ronald Reagan (who opposed environmental legislation as too costly to taxpayers and businesses), shuffled its way to preventive legislation, European response was much faster. In 1984 ten nations joined the "30 percent club", pledging to reduce emissions 30 percent from 1980 levels by 1993. The following year, the Helsinki Protocol was signed by 21 nations, pledging a similar reduction. By the early 1990s, sulphur dioxide emissions had dropped by 40 percent in most of Western Europe and by as much as 70 percent in "Green" West Germany. Unfortunately, by that time thousands of lake worldwide were already biologically dead and forests globally were in peril. And in the former Soviet bloc, little had been done to stem the burning of high-sulphur coal, releasing corrosive chemicals into the atmosphere.