Figure 1 illustrates that:
• Urban background particulate pollution has shown long-term improvement but
remained stable recently: average concentrations have gone down fairly consistently
throughout the time series to 17 µg m-3 in 2014, a new low since monitoring began in
1992. Concentrations changed little in the past seven years but in the past three years
have remained consistently below the level in 2008.
• Roadside particulate pollution has shown long-term improvement but changed
little recently: average concentrations have steadily declined to 19 µg m-3 in 2014, a
new low since monitoring began in 1996. Concentrations changed little in the past
seven years but in the past three years have remained consistently below the level in
2009.
• Urban background ozone pollution has shown a long-term increase: the average
maximum daily eight hour mean concentration has increased since 1987 and was 61 µg