Sulfur dioxide emissions in the U.S. 1970-2022

Sulfur dioxide (SO₂) emissions in the United States have decreased significantly over the five decades. Approximately 31.2 million tons of SO₂ were emitted in 1970, but levels have since dropped to below 1.8 million tons. This was a reduction of roughly 94 percent. There are numerous factors for these reductions, such as implementation of the Acid Rain Program and a shift away from coal-fired electricity generation.

Sources of sulfur dioxide

SO2 is largely used as an indicator for gaseous sulfur oxides (SOx) as these gases are found in low concentrations in the atmosphere. There are a number of sources of SO₂ emissions, though it is mostly emitted into the atmosphere through the burning of fossil fuels. Roughly half of SO₂ emissions in the U.S. are produced by electric utilities. Emissions can also be derived through industrial processes like extracting metal from ore, operating vehicles and heavy equipment that burn high-sulfur content fuel.

Air pollutants in the U.S.

In 1970, annual sulfur dioxide emissions were considerably higher than other key air pollutants in the U.S. , but over the years they have fallen so much that annual emissions of PM10, nitrogen dioxide, and ammonia are now higher.