Acid rain 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 sulphur 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 sulphur dioxide and nitrogen oxide into the atmosphere with positive results. Nitrogen oxides can also be produced naturally by lightning strikes, and sulphur dioxide
Environmental standard that can be released into atmosphere in order to maintain air quality and human health and regulate the release of greenhouse gases such as carbon dioxide (CO), oxides of nitrogen and oxides of sulfur. The standards are established in two phases to stay up to date, with final projections aiming to collectively save Americans $1.7 trillion in fuel costs and reduce the amount of greenhouse gas emissions (GHG) by 6 billion metric tons. Similar to the ambient standards, individuals states may also tighten regulations. For example, California set their own emissions standards through the California Air Resources Board (CARB), and