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Air Quality and Transboundary Emissions
35
transboundary pollutants: sulphur
dioxide (SO
2
), nitrogen oxides (NO
X
),
volatile organic compounds (VOCs)
and ammonia (NH
3
).
The Current Situation
Air Quality – Main Pollutants
Under the EU Directives, Ireland is
required to monitor a number of air
pollutants that have an impact on
health and vegetation. These include
NO
X
, SO
2
, carbon monoxide (CO),
ground level ozone (O
3
), particulate
matter (PM
10
and PM
2.5
), benzene,
heavy metals and polycyclic aromatic
hydrocarbons (PAHs). Across Europe
the most problematic pollutants
have consistently been NO
X
, PM and
O
3
. Recently PAHs have also been
identified as a pollutant of concern.
Oxides of Nitrogen (NO
X
)
NO
X
refers to the two pollutants
nitric oxide (NO) and nitrogen dioxide
(NO
2
). The main sources of these
pollutants are vehicle exhausts and
combustion sources. Exposure to
NO
2
is harmful to health, while
NO
X
contributes to the formation
of ground-level ozone and acid rain.
NO
2
levels across Ireland have
remained relatively static since 2002;
however, an increasing trend at
traffic-impacted sites in Dublin and
Cork is emerging. These sites are
approaching the 2010 limit value
for NO
2
with one exceedance of
the limit value recorded in 2009
at Winetavern Street, Dublin (EPA,
2010). This exceedance occurred
before the limit value came into
force on 1 January 2010. Figure 3.1
shows annual mean nitrogen dioxide
concentrations from 2002 to 2010
for monitoring sites across Ireland.
Particulate Matter (PM
10
and
PM
2.5
)
PM
10
and PM
2.5
are particles with
diameters less than 10 micrometres
and less than 2.5 micrometres
respectively. The health impacts of
these small particles relate to their
ability to penetrate deep into the
respiratory tract. In Ireland the main
sources are domestic use of solid fuel
and vehicular traffic.
PM
10
concentrations show a
decreasing trend in cities and
large urban areas since 2003. This
is mainly due to the decreases in
particulate emissions from traffic
arising from improvements in
vehicle engine emissions. However,
this decrease is not seen in smaller
towns, where domestic solid fuel
emissions are more significant than
traffic emissions. Many towns do
not benefit from the ban on smoky
coal, and often do not have access
to cleaner fuel alternatives such as
natural gas (EPA, 2011).
Under the CAFE Directive, Ireland
requires a reduction in levels of PM
2.5
by 10% between 2012 and 2020.
This reduction is challenging, as it
will require an integrated approach
across a number of sectors including
industrial, transport and residential
emissions. Figure 3.2 shows annual
mean PM
10
concentrations 2002–
2010 for monitoring sites across
Ireland.
Polycyclic Aromatic Hydrocarbons
(PAHs)
The sources of PAHs include industry,
traffic emissions and domestic use
of solid fuels such as wood and coal.
Long-term exposure to low levels
of PAHs may cause a number of
diseases including lung cancer.
PAHs were monitored in Ireland
for the first time in 2009 at five
monitoring stations. In 2010, levels
at two of the stations were at the
limit value of 1 ng/m
3
. Reductions
in emissions from traffic and from
domestic use of solid fuel are
required to reduce ambient levels
of PAHs.
Ground-Level Ozone (O
3
)
Ozone is a gas that is formed as a
secondary pollutant at ground-level
by the reaction of a mixture of other
chemicals – NO
X
, CO and VOCs – in
the presence of sunlight. Ozone is
a powerful oxidising agent and can
affect health and vegetation.
Figure 3.2
Annual Mean PM
10
Concentrations 2002–2010 (Source: EPA)
0
5
10
15
20
25
30
35
40
45
50
2002
µg/m
3
Zone A Traffic
(Dublin)
Zone A Background
(Dublin)
Zone B Traffic
(Cork)
Zone C
(21 biggest towns)
Zone D
(remainder of country)
Limit Value
2003
2004
2005
2006
2007
2008
2009
2010