Sulphur dioxide (SO 2 )
What is it? It's a gas with a pungent smell, but no colour and is produced from oxidation of sulphur. It comes from combustion of fossil fuels (coal, diesel oil) and from smelting metals industries. A low percentage of SO 2 (6-7%) is produced by vehicular traffic, particularly diesel engines. The concentration of Sulphur dioxide is higher in the winter, when domestic heating systems are at work.
Damage caused- The gas causes itchy eyes, sore throat and affects the respiratory tract; its effects are worse when combined with fog, as it dissolves easily in water droplets. The smallest drops may reach the lungs and lead to bronchitis and lung disease. Moreover, in the atmosphere, when it reacts with oxygen and water molecules, it produces acid rain, which is responsible for serious damages to forests, farming and waterways.
Development- Until a few years ago SO 2 was considered the most important air pollutant. However, improvements in the quality of fuels with a reduced amount of sulphur required by law, together with the widespread use of methane gas, have resulted in a consistent decrease of sulphur dioxide in air.
Range of allowed values, according to law (DM n. 60 del 02/02/2002)
|
Max concentration per hour ( µ g/mc) |
Max concentration 24 h ( µ g/mc) |
Max quantity for human health |
350 |
125 |
Tolerance limit |
At present 0 |
Tolerance limit for ecosystems |
20 |
Danger limit measured on 100sqkm |
500 |
Range of values in urban centres
|
Human health (average 24 h) ( µ g/mc) |
Features of ecosystem (winter average) ( µ g/mc) |
Low limit |
50 |
8 |
High limit |
75 |
12 |
|