Exhaust gases also react with strong sunlight to produce poisonous ozone gas which damages plant growth and in some cases, human health. Sulphur is one of the chemical elements that make up the Earth. It can come from natural sources including volcanic eruptions, sea spray and minute sea creatures called plankton. The building of tall chimneys, which was supposed to prevent problems by dispersing pollutants over a wider area, has made the problem worse for distant areas lying downwind. Norway and Sweden, for example, receive far more pollutants than they produce, much of them from Britain.
Acid rain corrodes metal and stone work making the maintenance of buildings more costly.
The major threats are to older historic buildings. Farming As the land become more acid, it is less suitable for growing crops and yields can be reduced. The crops themselves can be damaged, for example, pollen on maize affected by acid rain does not germinate so well and cannot fertilize the female plant. Trees and forests Sulphur dioxide interferes with the process of photosynthesis. Coniferous trees seem to be most at risk from acid rain because they do not shed their needles at the end of each year.