2.1.4: EAQLVlocal - Air Quality Limit - Local
EAQLVlocal – AIR QUALITY LIMIT – LOCAL
| Topic | Urban challenges | Sub-challenges |
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| Environment | 2 - Air Quality | 2.2 Air Quality at Local Scale |
Description | This indicator shows the fraction of a given area (local) that is potentially exposed to ambient air concentrations of certain pollutants (PM2.5 , PM10 , O3 , NO2 , SO2 and BaP) that are in excess of the EU limit or target values (EU, 2004, 2008) set for the protection of human health. This indicator is an adaptation at city scale of the indicator CSI 004 of the European Environment Agency : Exceedance of air quality limit values in urban areas. |
Scale as linked to D2.2 framework |
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Data source [ link to data framework] | For main cities throughout Europe useful data can be found in the following sources:
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Calculation methods | Population exposure: Two types of monitoring stations are considered, classified as 'urban traffic', and 'urban background'. The “urban traffic” stations represent the environmental conditions of places located closer than 100 meters from major roads. The “urban background” stations represent the average environmental conditions in the city. The percentage of the city population living closer than 100 meters from major roads is used to allocate exposure of the city population to the two types of environmental conditions. In case there are several stations of the same type an allocation rule has to be established to allocate the population to the different stations of the same type. This indicator is usually used at city scale where averaging effects come to play. These averaging effects won’t be effective ate a smaller scale. Thus the allocation of populations to the different monitoring stations becomes a key issue. A proper methodology with this regard has to be developed; number of monitoring stations, locations of the monitoring stations, allocation of population to the different station, … EU limit and target values: Particulate matter (PM2.5): The annual mean concentration is calculated for each of the selected stations. Depending on the mean concentration, each station (and its allocated population) is then classified uniquely in one of the two concentration classes (below or equal to the target value (25 µg/m3), or above it). The percentage of the urban population allocated to these two concentration classes is calculated by dividing the population represented by the stations assigned to each concentration class by the sum of the population assigned to each station. Particulate matter (PM10): For each selected station, the 90.4 percentile (P90.4) of the daily mean concentration series is calculated. P90.4 represents, in a complete series of 365 elements, the 36th highest value. When P90.4 is below or equal to 50 µg/m3, it indicates that the daily limit value (DLV) would not have been exceeded on more than 35 days. Depending on the value of P90.4, each station (and its allocated population) is then classified uniquely in one of the two concentration classes (P90.4 > 50 µg/m3, i.e. above the DLV and P90.4 ≤ 50 µg/m3, i.e. below the DLV). The percentage of the urban population allocated to these two concentration classes is calculated by dividing the population represented by the stations assigned to each individual concentration class by the sum of the population assigned to each station. Ozone (O3): For each selected station, the 93.2 percentile (P93.2) of the daily maximum 8-hourly mean concentration series is calculated. P93.2 represents, in a complete series of 365 elements, the 26th highest value. When P93.2 is below or equal to 120 µg/m3, it indicates that the long term objective would have not been exceeded on more than 25 days. Depending on the value of P93.2, each station (and its allocated population) is then classified uniquely in one of the two concentration classes (P93.2 > 120 µg/m3, i.e. exceedance of the long term objective on more than 25 days, and P93.2 ≤ 120 µg/m3, i.e. exceedance of the long term objective is less than or equal to 25 days). The percentage of the urban population allocated to these two concentration classes is calculated by dividing the population represented by the stations assigned to each individual concentration class by the sum of the population assigned to each station. Nitrogen dioxide (NO2): The annual mean concentration is calculated for each of the selected stations. Depending on the annual mean concentration, each station (and its allocated population) is then classified uniquely in one of the two concentration classes (below or equal to the limit value (40 µg/m3), or above the limit value). The percentage of the urban population allocated to these two concentration classes is calculated by dividing the population represented by the stations assigned to each concentration class by the sum of the population assigned to each station. Benzo[a]pyrene (BaP): The annual mean concentration is calculated for each of the selected stations. Depending on the mean concentration, each station (and its allocated population) is then classified uniquely in one of the two concentration classes (below or equal to the target value (1.0 ng/m3), or above the target value). The percentage of the urban population allocated to these two concentration classes is calculated by dividing the population represented by the stations assigned to each concentration class by the sum of the population assigned to each station. Sulfur dioxide (SO2): For each selected station, the 99.2 percentile (P99.2) of the daily mean concentration series is calculated. P99.2 represents, in a complete series of 365 elements, the 4th highest value. When P99.2 is below or equal to 125 µg/m3, it indicates that the daily limit value would have not been exceeded on more than three days. Depending on the value of P99.2, each station (and its allocated population) is then classified uniquely in one of these two concentration classes (P99.2 > 125 µg/m3, i.e. above the daily limit value and P99.2 ≤ 125 µg/m3, i.e. below the daily limit value). The percentage of the urban population allocated to these two concentration classes is calculated by dividing the population represented by the stations assigned to each individual concentration class by the sum of the population assigned to each station Data quality: For PM10, PM2.5, O3, NO2 and SO2, only stations with at least 75 % of valid data per calendar year are used. That is, in the case of daily values, those having more than 274 valid daily values per calendar year (or 275 days in a leap year). And in the case of hourly values, having more than 6 570 valid hourly values per calendar year (or 6 588 hours in a leap year). For BaP, the minimum data time coverage accepted is 14 % (51 days), according to the data quality objectives related to indicative measurements in the Directive 2004/107/EU (EU, 2004). |
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