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EC Threshold/Limit Values

A number of EC criteria are reported in this database, as detailed below.

Pollutant Description Criteria Based on Value µg/m3 (ppb)
Ozone Vegetation Protection Threshold 1 hour mean 200 (100)
24 hour (daily) mean 65 (32)
Nitrogen Dioxide Alert Threshold 3 hour mean 400 (500)
Sulphur Dioxide Alert Threshold 3 hour mean 500 (188)
Limit Value Median of daily values for pollution year (1) 80 (30) if smoke concs > 34
120(45) if smoke <=34
Median of daily values for winter (2) 130 (49) if smoke concs > 51
180 (68) if smoke concs <=51
98th percentile of daily values for pollution year (3) 250 (94) if smoke concs > 128
350 (131) if smoke concs <=128

Note:

  1. Sulphur dioxide measurements are reported over a pollution year (1 April - 31 March) so that measurements include a continuous 6 month winter period. This is because these concentrations are generally higher during the winter months.
  2. Winter is defined as 1 Oct - 31 Mar
  3. A percentile is defined in the Glossary