particularly Sulfur dioxide (SO2) is a gas. It is invisible and has a nasty, sharp smell. It reacts easily with other substances to form harmful compounds, such as sulfuric acid, sulfurous acid and sulfate particles. About 99% of the sulfur dioxide in air comes from human sources, mostly comes from burning of fossil fuel (mainly coal and oil) in power plants, but it also comes from factories producing chemicals, paper or fuel.
During the process of oxidation in the atmosphere this gas forms sulfates or salts that can be transported in the breathable particulate material (PM10) that in presence of humidity forms acids. Later these acids are an important part of the secondary particulate material or finest particulate material (PM2,5). The exposure to sulfates and the exposure to acids derived from SO2 is extremely risky for people’s health because these compounds enter the circulatory system directly through the airways.
The SO2 is hydroscopic, when it is in the atmosphere it reacts with humidity and forms sulfuric and sulfurous aerosol acid that is later part of the so-called acid rain. The intensity in the formation of aerosols and the permanence of them in the atmosphere depend on the meteorological conditions and the quantity of catalytic impurities (substances that accelerate the processes) present in the air. But in general, the average time of permanence in the atmosphere is around 3-5 days, so it can be transported to greater distances.
The air pollution by SO2 has the following effects on human beings:
Breathing difficulty, Airways inflammation, Eye irritation, Psychic alterations, Pulmonary oedema, Heart failure, or Circulatory collapse.
SO2 maximum exposure for humans is set to 125 µg/m3/day while a max of 350 µg/m3 per 1 hour should not be crossed