Sulfur dioxide is one of the most harmful air pollutants. It is together with the nitrogen oxides the major precursor of acid rain. High concentration of sulfur dioxide in the air can cause adverse health effects such as breathing problems, respiratory illness, and even cardiovascular disease.
The major source of sulfur dioxide emissions are coal power plants. US coal power plants are for instance responsible for around 67 percent of the nation's sulfur dioxide emissions.
When coal is burned, one of the substances that are released is sulfur dioxide together with carbon dioxide and nitrogen oxide.
The levels of sulfur dioxide seem to have been decreasing in the last couple of years. According to the latest NASA measuring sulfur dioxide levels in the vicinity of major US coal power plants have fallen by nearly half (46%) since 2005.
The major factor behind this significant decrease in sulfur dioxide emissions has been an adequate legislation, namely the Clean Air Interstate Rule of 2005 that called for deep reductions in sulfur dioxide emissions.
This legislation forced many US coal power plants to install desulfurization devices as well as taking some other necessary steps to limit the released amount of sulfur dioxide.
A few decades back sulfur pollution was severe pollution issue in United States but luckily levels of this serious air pollutant have dropped by approximately 75 percent since the 1980s thanks mostly to the passage of the Clean Air Act.
The country that is currently most severely affected with high levels of sulfur dioxide in the air is China. China's fast growing economy is heavily dependent on coal burning and this has created significant levels of sulfur dioxide in the air in the vicinity of Chinese coal power plants.
In order to measure the levels of sulfur dioxide in the air scientists use Ozone Monitoring Instrument on NASA's Aura satellite.