Percentage of urban population resident in areas for days per year with SO2 concentration exceeding daily limit value, EEA member countries, 1996-2005
2: Over the years 1990-2005, the total population for which exposure estimates are made, increases from 62 to 122 million people due to an increasing number of monitoring station reporting air quality data. Year-to-year variations in exposure classes are partly caused by the changes in spatial coverage. The number of available data series varies considerably from year to year and is for the first part of the 90s insufficient. Availability of data before 1990 is too low to include in the indicator; data for non-EU countries is largely missing before 1995.