Air Quality Standards
The Environmental Protection Agency manages the ambient air quality monitoring network.
In order to protect our health, vegetation and ecosystems, EU directives set down air quality standards in Ireland and the other member states for a wide variety of pollutants. These rules include how we should monitor, assess and manage ambient air quality. The European Commission set down the principles to this approach in 1996 with its Air Quality Framework Directive. Four "daughter" directives lay down limits for specific pollutants:
- 1st Daughter Directive: Sulphur dioxide, nitrogen dioxide and oxides of nitrogen, particulate matter and lead
- 2nd Daughter Directive: Carbon monoxide and benzene
- 3rd Daughter Directive: Ozone
- 4th Daughter Directive: Polyaromatic hydrocarbons, arsenic, nickel, cadmium and mercury in ambient air
The Ambient Air Quality and Cleaner Air for Europe (CAFE) Directive (2008/50/EC) was published in May 2008. It replaced the Framework Directive and the first, second and third Daughter Directives. The fourth Daughter Directive (2004/107/EC) will be included in CAFE at a later stage. The limit and target values for both Directives are outlined below.
The CAFE Directive was transposed into Irish legislation by the Air Quality Standards Regulations 2011 (S.I. No. 180 of 2011). It replaces the Air Quality Standards Regulations 2002 (S.I. No. 271 of 2002), the Ozone in Ambient Air Regulations 2004 (S.I. No. 53 of 2004) and S.I. No. 33 of 1999.
The fourth Daughter Directive was transposed into Irish legislation by the Arsenic, Cadmium, Mercury, Nickel and Polycyclic Aromatic Hydrocarbons in Ambient Air Regulations 2009 (S.I. No. 58 of 2009).
Links to EU and Irish ambient air quality legislation currently in force
- Directive on ambient air quality and cleaner air for Europe (CAFE) - replaces the air framework directive and the first three daughter directives - 2008/50/EC
- Air quality standards regulations 2011 - SI 180 of 2011 transposed the CAFE Directive into Irish law.
- Fourth 'daughter' directive - relating to arsenic, cadmium, mercury, nickel and polycyclic aromatic hydrocarbons - 2004/107/EC
- The arsenic, cadmium, mercury, nickel and polycyclic aromatic hydrocarbons in ambient air Regulations 2009 - SI 58 of 2009 transposed the 4th Daughter Directive into Irish law.
Directives set targets for air quality
The following tables show the limit or target values specified by the five published directives that set down limits for specific air pollutants. The directives cover:
- Sulphur dioxide, nitrogen dioxide and oxides of nitrogen, particulate matter (PM10 and PM2.5) and lead
- Carbon monoxide and benzene
- Ozone
- Arsenic, Cadmium, Nickel and Benzo(a)pyrene
Check the bottom of this article for explanations of the abbreviations used.
Limit values of CAFE Directive 2008/50/EC
| Pollutant | Limit Value Objective | Averaging Period | Limit Value µg/m³ | Limit Value ppb | Basis of Application of the Limit Value | Limit Value Attainment Date |
|---|---|---|---|---|---|---|
| SO2 | Protection of human health | 1 hour | 350 | 132 | Not to be exceeded more than 24 times in a calendar year | 1 Jan 2005 |
| SO2 | Protection of human health | 24 hours | 125 | 47 | Not to be exceeded more than 3 times in a calendar year | 1 Jan 2005 |
| SO2 | Protection of vegetation | calendar year | 20 | 7.5 | Annual mean | 19 July 2001 |
| SO2 | Protection of vegetation | 1 Oct to 31 Mar | 20 | 7.5 | Winter mean | 19 July 2001 |
| NO2 | Protection of human health | 1 hour | 200 | 105 | Not to be exceeded more than 18 times in a calendar year | 1 Jan 2010 |
| NO2 | Protection of human health | calendar year | 40 | 21 | Annual mean | 1 Jan 2010 |
| NO + NO2 | Protection of ecosystems | calendar year | 30 | 16 | Annual mean | 19 July 2001 |
| PM10 | Protection of human health | 24 hours | 50 | Not to be exceeded more than 35 times in a calendar year | 1 Jan 2005 | |
| PM10 | Protection of human health | calendar year | 40 | Annual mean | 1 Jan 2005 | |
| PM2.5 - Stage 1 | Protection of human health | calendar year | 25 | Annual mean | 1 Jan 2015 | |
| PM2.5 - Stage 2 | Protection of human health | calendar year | 20 | Annual mean | 1 Jan 2015 | |
| Lead | Protection of human health | calendar year | 0.5 | Annual mean | 1 Jan 2005 | |
| Carbon Monoxide | Protection of human health | 8 hours | 10,000 | 8620 | Not to be exceeded | 1 Jan 2005 |
| Benzene | Protection of human health | calendar year | 5 | 1.5 | Annual mean | 1 Jan 2010 |
Alert thresholds
The public must be informed if the following thresholds are exceeded for three consecutive hours.
| Pollutant | Averaging Period | Limit Value |
|---|---|---|
| Sulphur Dioxide | 1 hour | 500 µg/m³ |
| Nitrogen Dioxide | 1 hour | 400 µg/m³ |
Target values and long-term objectives of CAFE Directive 2008/50/EC
Target values for ozone from 2010
| Objective | Parameter | Value |
|---|---|---|
| Protection of human health | Maximum daily 8 hour mean | 120 µg/m³ not to be exceeded more than 25 days per calendar year averaged over 3 years |
| Protection of vegetation | AOT40, calculated from 1 hour values from May to July | 18000 µg/m³-h averaged over 5 years |
Long-term objectives for ozone from 2020
| Objective | Parameter | Value |
|---|---|---|
| Protection of human health | Maximum daily 8 hour mean | 120 µg/m³ |
| Protection of vegetation | AOT40, calculated from 1 hour values from May to July | 6000 µg/m³-h |
The public must be informed if ozone levels exceed the following thresholds
| Parameter | Threshold | |
|---|---|---|
| Information Threshold | 1 hour average | 180 µg/m³ |
| Alert Threshold | 1 hour average | 240 µg/m³ |
Target Values of Directive 2004/107/EC
| Pollutant | Limit Value Objective | Averaging Period | Target Value ng/m³ | Limit Value Attainment Date |
|---|---|---|---|---|
| Arsenic | Protection of human health | calendar year | 6 | 31 Dec 2012 |
| Cadmium | Protection of human health | calendar year | 5 | 31 Dec 2012 |
| Nickel | Protection of human health | calendar year | 20 | 31 Dec 2012 |
| Benzo(a)pyrene | Protection of human health | calendar year | 1 | 31 Dec 2012 |
Conversion factors from ppb to µg/m³
Nitrogen dioxide 1 ppb = 1.91 ug/m3
Sulphur dioxide 1 ppb = 2.66 ug/m3
Ozone 1 ppb = 2.0 ug/m3
Carbon monoxide 1 ppb = 1.16 ug/m3
Benzene 1 ppb = 3.24 ug/m3
An example of calculating the AOT40
The following is a worked example:
| Local Time Ireland | Central European Time | Ozone Concentration µg/m³ | Difference between previous column and 80 µg/m³ |
|---|---|---|---|
| 23:00 | 00:00 | 63 | Not counted before 08:00 |
| 00:00 | 01:00 | 70 | Not counted before 08:00 |
| 01:00 | 02:00 | 65 | Not counted before 08:00 |
| 02:00 | 03:00 | 63 | Not counted before 08:00 |
| 03:00 | 04:00 | 45 | Not counted before 08:00 |
| 04:00 | 05:00 | 54 | Not counted before 08:00 |
| 05:00 | 06:00 | 56 | Not counted before 08:00 |
| 06:00 | 07:00 | 55 | Not counted before 08:00 |
| 07:00 | 08:00 | 55 | Only values greater than 80 count |
| 08:00 | 09:00 | 62 | 0 |
| 09:00 | 10:00 | 51 | 0 |
| 10:00 | 11:00 | 70 | 0 |
| 11:00 | 12:00 | 92 | 12 |
| 12:00 | 13:00 | 90 | 10 |
| 13:00 | 14:00 | 82 | 2 |
| 14:00 | 15:00 | 87 | 7 |
| 15:00 | 16:00 | 91 | 11 |
| 16:00 | 17:00 | 90 | 10 |
| 17:00 | 18:00 | 89 | 9 |
| 18:00 | 19:00 | 84 | 4 |
| 19:00 | 20:00 | 85 | Not counted after 20:00 |
| 20:00 | 21:00 | 83 | Not counted after 20:00 |
| 21:00 | 22:00 | 70 | Not counted after 20:00 |
| 22:00 | 23:00 | 60 | Not counted after 20:00 |
| AOT40 = sum of values in the 4th column = | 65 µg/m³ hours | ||
Abbreviations used
- µg/m³
- micrograms per cubic metre
- ng/m³
- nanograms per cubic metre
- ppb
- parts per billion
- NO2
- Nitrogen Dioxide
- NO
- Nitric Oxide
- SO2
- Sulphur Dioxide
- PM10
- Particulate Matter with a diameter less than 10 microns
- PM2.5
- Particulate Matter with a diameter less than 2.5 microns
- AOT40
- This is a measure of the overall exposure of plants to ozone. It is the sum of the excess hourly concentrations greater than 80 µg/m³ and is expressed as µg/m³ hours. Only values measured between 08:00 and 20:00 Central European Time each day from May to July are used for the calculation. (The name AOT40 refers to 40ppb which is the same as 80 µg/m³)