Sulfur Dioxide

Houston Levels of Sulfur Dioxide Remain Well Below EPA’s Health Based Standard

What is Sulfur Dioxide?

Sulfur dioxide (SO2) is one of a group of highly reactive gasses known as “oxides of sulfur.”  Short-term exposures to SO2 can harm the human respiratory system and make breathing difficult. Children, the elderly, and those who suffer from asthma are particularly sensitive to effects of SO2.

Where is Sulfur Dioxide Found?

The largest sources of SO2 emissions are from fossil fuel combustion at power plants (73%) and other industrial facilities (20%).  Smaller sources of SO2 emissions include industrial processes such as extracting metal from ore, and the burning of high sulfur containing fuels by locomotives, large ships, and non-road equipment.  SO2 is linked with a number of adverse effects on the respiratory system.

SO2 is also a contributor to fine particle pollution, and to acid rain, which can cause damage to trees and other vegetation and cause lakes to become more acidic.
In 2010, EPA revised the health-based SO2 standard by establishing a new 1-hour standard at a level of 75 parts per billion (ppb). Annual average SO2 concentrations, as measured by monitors around the nation, have decreased by more than 70% since 1980. Measurements of the acidity of rain and lakes have also shown decreases.

Houston has met the national standard for SO2 for many years now, and concentrations at all monitors are well below national standards.

Learn More about SO2:

Houston SO2 Levels