Which organism is indicator of S-pollution?

S-pollution is Sulphur dioxide pollution, and Lichens is an indicators of S-pollution.
Lichens do not survive in areas polluted with Sulphur dioxide. Sulphur dioxide is a gaseous air pollutant composed of Sulphur and oxygen, formed by burning coal, oil, or diesel is burned. And this Sulphur dioxide combines with rain water and air to form sulphuric acid, which is the main component of acid rain.