Long term trends in air quality in the City

Nitrogen Dioxide

Up until 2002, although NO2 concentrations were above the air quality objective of 40 µg m-3, concentrations of the gas remained relatively stable at each site and showed a general decrease in concentrations. However, since 2002, annual average NO2 concentrations have increased quite dramatically at all diffusion tube sampling locations.

During 2006 the concentrations dropped to below that of 2005 levels, however, it should be noted that the results for 2006 prior to applying the bias factor were actually of greater concentrations than those in 2005.

Fine Particles (PM₁₀)

PM₁₀ is measured at three locations across the City. The air quality in 2003 with respect to PM₁₀ was the worst year recorded since monitoring began at Beech Street in 1999. Since 2003 the 24 hour PM₁₀ objective has been exceeded at all sites, apart from at John Cass School during the years 2004 and 2006.

Benzene

Concentrations of benzene have declined since monitoring began in 1997. As can be seen in the following graph, benzene concentrations in the City are below the 2003 and 2010 objectives set by the Government.

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