 Acid rain, acid rain is a rain or any other form of precipitation that is unusually acidic, meaning that it has elevated levels of hydrogen ions low pH. It can have harmful effects on plants, aquatic animals and infrastructure. Acid rain is caused by emissions of sulfur dioxide and nitrogen oxide, which react with the water molecules in the atmosphere to produce acids. Some governments have made efforts since the 1970s to reduce the release of sulfur dioxide and nitrogen oxide into the atmosphere with positive results. Hydrogen oxides can also be produced naturally by lightning strikes. And sulfur dioxide is produced by volcanic eruptions. Acid rain has been shown to have adverse impacts on forests, fresh waters and soils, killing insect and aquatic life forms, causing paint to peel, corrosion to steel structures such as bridges and weather ring of stone buildings and statues as well as having impacts on human health.