Figure 10.1: Percentage of measured 24-hour average PM₁₀ concentrations within air quality categories at St Albans, Christchurch

Text description of figure

There is a graph comparing average 24-hour concentrations of PM₁₀ in St Albans, Christchurch, between 1988 and 2001. At the start of the period, nearly 30 per cent of concentrations were in the 'alert' category, or over the guideline. This improved throughout the period, although there were both positive and negative fluctuations to this trend in the early 1990s. At the other end of the scale, the percentage of concentrations in the 'good' category was below 40 per cent at the start of the period. This amount quickly rose, plummeted, and then rose again, into the mid 1990s, and has subsequently declined from over 60 per cent of all concentrations, to about 50 per cent.