Ambient air quality criteria

Ambient air quality criteria or standards are concentrations of pollutants in the air (usually outdoor air but sometimes indoor air) specified for a variety of reasons including for the protection of human health, buildings, crops, vegetation, ecosystems, as well as for planning and other purposes. There is no internationally accepted definition but usually "standards" have some legal or enforcement aspect, whereas "guidelines" may not be backed by laws. "Criteria/criterion" can be used as a generic term to cover standards and guidelines.

Various organisations have proposed criteria e.g. WHO, EU, US EPA and they are often similar - but not always, even if they are proposed for the same purpose (e.g. the protection of human health).

Specifying the Criteria

Important for any numerical standard is to ensure that averaging period, unit, and statistical measure are given (e.g. 98th percentile of hourlry means measured over a calendar year in micrograms per cubic metre (µg/m3)). Without all of these three aspects the criterion is confusing and meaningless. Criteria can be set in different units (e.g. µg/m3, parts per billion by volume (ppbv), parts per billion by mass (ppb(mass)), parts per million (ppm)) and it is possible to convert between all of these units if you know the molecular mass of the pollutant and the temperature at which you want to convert. Different temperatures are used throughout the world and so it is important to state the temperature of conversion (if relevant). Most pollutants have ambient criteria in the parts per billion (ppb)/µg/m3 range. Some have smaller units (e.g. dioxins are often in pico grams /m3); others have larger units (e.g. carbon monoxide (CO) in mg/m3). Particle pollution (e.g. PM10, PM1.0) is specified in units of mass (e.g. µg/m3) and not in units of volume (ppmv).

The Criteria

Below is a list of available criteria around the world. There is a lot of cross referencing (e.g. the International Finance Corp (IFC) has their own criteria but they are a copy of those specified by the WHO. It is important to check the reference as not all the related caveats/controlling parameters of the criterion can be put in the table. Also some criteria require certain specific ways of monitoring to demonstrate compliance.

Pollutant Abbr. Value Units Averaging Period Statistical Measure # exceedences Organisation Status Applicability Notes
Nitrogen dioxide NO240 µg/m3 Annual Mean None WHO [1] Guideline Global
Nitrogen dioxide NO240 µg/m3 Annual Mean None EU [2] Limit Value EU Member States Calendar Year
Nitrogen dioxide NO2100 µg/m3 Annual Mean None US EPA [3] Legal United States Quoted as 53 ppb
Nitrogen dioxide NO2113 µg/m3 Daily Daily mean of hourly None Japanese Ministry of Environment [4] Legal Japan Quoted as 0.06 ppm
Nitrogen dioxide NO2100 µg/m3 Annual Yrly mean of daily None SCENR [5] Legal Qatar Calendar Year
Nitrogen dioxide NO2150 µg/m3 Daily (24hr) 99.7%ile 1 day/yr SCENR [5] Legal Qatar Calendar Year
Nitrogen dioxide NO2200 µg/m3 1 hour 99.79%ile 18 hrs/yr EU [2] Limit value EU Member States Calendar Year
Nitrogen dioxide NO2400 µg/m3 1 hour 99.7%ile 26 hrs/yr SCENR [5] Legal Qatar Calendar Year
Pollutant Abbr. Value Units Averaging Period Statistical Measure # exceedences Organisation Status Applicability Notes
Sulphur dioxide SO2125 µg/m3 24 hour Any 24 hour period None WHO [1] Interim Target (IT) 1 Global Was the guideline in 2000
Sulphur dioxide SO250 µg/m3 24 hour Any 24 hour period None WHO [1] Interim Target (IT) 2 Global Calendar Year (1 Jan - 31 Dec)
Sulphur dioxide SO2125 µg/m3 24 hour Any 24 hour mean None WHO [1] Interim Target (IT) 1 Global
Sulphur dioxide SO250 µg/m3 24 hour Any 24 hour mean None WHO [1] Interim Target (IT) 2 Global
Sulphur dioxide SO220 µg/m3 24 hour Any 24 hour mean None WHO [1] Guideline Global
Sulphur dioxide SO2500 µg/m3 10 minute Any 10 minute mean None WHO [1] Guideline Global
Sulphur dioxide SO21300 µg/m3 1 hour 99.99%ile 1 hr/year Ras Laffan Legal Qatar Calendar Year
Pollutant Abbr. Value Units Averaging Period Statistical Measure # exceedences Organisation Status Applicability Notes
Fine particles PM10 125 µg/m3 24 hour 99th %ile 3 days/yr WHO [1] Guideline Global
Very fine particles PM2.5 25 µg/m3 24 hour Any 24 hr mean None WHO [1] Guideline Global
Very fine particles PM2.5 75 µg/m3 24 hour Any 24 hr mean None WHO [1] Interim target (IT) 1 Global
Very fine particles PM2.5 50 µg/m3 24 hour Any 24 hr mean None WHO [1] Interim target (IT) 2 Global
Very fine particles PM2.5 37.5 µg/m3 24 hour Any 24 hr mean None WHO [1] Interim target (IT) 3 Global
Very fine particles PM2.5 10 µg/m3 Annual Mean None WHO [1] Guideline Global
Very fine particles PM2.5 35 µg/m3 Annual Mean None WHO [1] Interim target (IT) 1 Global
Very fine particles PM2.5 25 µg/m3 Annual Mean None WHO [1] Interim target (IT) 2 Global
Very fine particles PM2.5 15 µg/m3 Annual Mean None WHO [1] Interim target (IT) 3 Global
Pollutant Abbr. Value Units Averaging Period Statistical Measure # exceedences Organisation Status Applicability Notes
Ozone O3100 µg/m3 8 hours Any 8 hour mean None WHO [1] Guideline Global
Ozone O3160 µg/m3 8 hours Any 8 hour mean None WHO [1] Interim target Global
Ozone O3235 µg/m3 1 hour 99.9% 8 hrs/yr SCENR [5] Legal Qatar Calendar Year
Ozone O3120 µg/m3 8 hours 99.8% 2x8hrs/yr SCENR [5] Legal Qatar Calendar Year
Pollutant Abbr. Value Units Averaging Period Statistical Measure # exceedences Organisation Status Applicability Notes
Carbon monoxide CO 40000 µg/m3 1 hour Maximum None SCENR [5] Legal Qatar Calendar Year
Carbon monoxide CO 10000 µg/m3 8 hour Maximum None SCENR [5] Legal Qatar Calendar Year

References

  1. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 Air quality guidelines - global update 2005 www.who.int/phe/health_topics/outdoorair/outdoorair_aqg/en/
  2. 1 2 DIRECTIVE 2008/50/EC OF THE EUROPEAN PARLIAMENT AND OF THE COUNCIL of 21 May 2008 on ambient air quality and cleaner air for Europe http://eur-lex.europa.eu/legal-content/EN/TXT/?uri=CELEX:32008L0050
  3. ↑ National Ambient Air Quality Standards https://www.epa.gov/criteria-air-pollutants/naaqs-table
  4. ↑ Japanese Ministry of Environment, Environmental Quality Standards - Air Quality https://www.env.go.jp/en/air/aq/aq.html
  5. 1 2 3 4 5 6 7 Supreme Council for Environment and Natural Resources, Executive Bye-law for the Environment Protection Law Issued via the Decree Law No. 30 for the Year 2002, Annex 3"
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