in outdoor air is formed through energy generation and ships’ emissions. Concentrations in the Helsinki Metropolitan
Area are nowadays low, and won’t exceed the limit values. The abbreviation SO2
refers to sulphur dioxide.
is poor when the hourly value exceeds 250 µg/m3. Sulphur dioxide’s limit value for an hour is 350 µg/m3 and the limit for
24 hours is 125 µg/m3. The public must be warned about
health hazards if the warning threshold (500 µg/m3) continues to be exceeded
for three hours. Concentrations this high are very unlikely in the Helsinki