Figure 3.4: The percentage of measured 24-hour average PM₁₀ concentrations within air quality categories at Penrose, Auckland

Text description of figure

The chart shows 24-hour concentrations of PM₁₀ measured in Penrose, Auckland, between 1994 and 2001. At the beginning of the period over 40 per cent of concentrations were good, 35 per cent were 'acceptable', about 13 per cent were in the 'alert' category, and about 7 per cent were over the guideline. There was an immediate drop in the percentage of 'good' concentrations to 20 per cent in 1995. Through the late 1990s these proportions remained consistent, but in 2000 the proportion of 'good' concentrations doubled to nearly 50 per cent, and in 2001 the proportion of concentrations in the 'alert' category, or over the guideline, decreased to about 5 per cent.