Ozone levels ‘failing to drop in Northern Ireland’

Ozone and benzopyrene levels are continuing to breach UK objectives in Northern Ireland, although nitrogen dioxide and PM10 targets are being met, according to government report

Levels of ozone are failing to decrease in Northern Ireland, a government report has found, leading to fears that the country will continue to breach UK objectives for the pollutant.

Annual mean benzopyrene concentration levels are also exceeding UK objectives at a number of monitoring sites in Northern Ireland, although objectives for annual mean levels of nitrogen dioxide and particulate matter PM10 are below UK objectives.

Data provided by Ricardo-AEA which shows ozone levels at monitoring sites in Northern Ireland since 2001

Data provided by Ricardo-AEA which shows ozone levels at monitoring sites in Northern Ireland since 2001

The findings come in the Department of Environment for Northern Ireland (DOENI)’s fifth annual Northern Ireland Environmental Statistics Report, which is based on data collected by environmental consultants Ricardo-AEA.

Ozone is monitored in Northern Ireland at sites in Belfast, Londonderry and Lough Navar in the south west. In the last 10 years, exceedances of the UK objective have occurred on five occasions at the Derry and Lough Navar sites, which the report attributes to variable weather conditions in the country.

The UK objective for ozone states that for the whole of the UK, an eight hour mean concentration of 100 micrograms per cubic metre must not to be exceeded more than ten times a year by December 31 2005.

The report states: “Unlike some other pollutants, levels of ozone in Northern Ireland do not appear to be decreasing, but remain variable from year to year, depending on weather conditions and transboundary levels of ozone i.e. Ozone crossing provincial, territorial or national boundaries. Therefore, ozone exceedences remain a possibility.”

With regards to nitrogen dioxide, the report suggests that although there has been more variation at roadside levels, the background level of nitrogen dioxide in urban areas has remained relatively stable over the past ten years.

The average annual mean concentration at Northern Ireland’s urban background monitoring sites has ranged from 19 to 27 micrograms per cubic metre since 2001. The UK national objective is 40.

The report also shows that since 2001, the annual mean concentration of PM10 averaged over Northern Ireland’s urban monitoring sites has been less than 28 micrograms per cubic metre, thus falling below the UK national objective of 40 micrograms per cubic metre.


However, the PM10 limit has been breached regularly at the four monitoring sites for the pollutant during the last 10 years: Lisburn Dunmurry High School near Belfast, Belfast Clara Street, Derry Brandywell and Ballykeel in Ballymena.

For the whole of the UK, the limit for annual average concentrations of carcinogenic benzopyrene is 0.25 nanograms per cubic metre to be met by December 31 2010.

Monitoring of the pollutant stopped at Belfast Clara Street in 2007, but all three other sites breached national limits in 2011. Ballykeel Ballymena also breached the less stringent EU limit of 1 nanogram per cubic metre for the pollutant in 2011, which the report suggests is due to the widespread use of smoky coal.

Benzopyrene has been monitored the longest (since 2001) at Lisburn Dunmurry High School, with annual levels fluctuating between 0.44 and 1.44 micrograms per cubic metre.

According to the report, the three remaining monitoring sites in Northern Ireland for benzopyrene show annual mean concentrations “similar to those seen in industrial areas in Great Britain such as Scunthorpe, Middlesbrough and Port Talbot”.

The report states: “It is considered likely that the high polycyclic aromatic hydrocarbon (PAH — in this case benzopyrene) concentrations recorded at these locations are due to widespread combustion of smoky (bituminous) coal.  This is demonstrated by the lower PAH levels recorded at Belfast Clara Street (part of a Smoke Control Area) from 2001 to 2006, being comparable to levels recorded in other large UK cities.”

There are more than 30 air quality monitoring stations in Northern Ireland. Levels of carbon monoxide, nitrogen oxides, sulphur dioxide, particles, ozone, benzene, 1,3-butadiene and polycyclic aromatic hydrocarbons are monitored at many of these stations.

The fifth annual Northern Ireland Environmental Statistics Report was published on the DOENI website yesterday (January 31).


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