Rain water is naturally slightly acidic, however whenever mixed with air pollutants caused by the burning of fossil fuels in power stations or the use of cars it becomes more acidic.
Oxides of sulphur and nitrogen when mixed with water form sulphuric acid.
This falls as rain or snow onto the soil or water which releases aluminium and lead which is highly toxic to plants, vegetation and fish. Acid rain also causes problems to limestone, sandstone and metals such as window frames.
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