Figure 3.2: The percentage of measured 24-hour average PM₁₀ concentrations within air quality categories at Henderson and Mt Eden, Auckland

Text description of figure

There are two charts showing 24-hour concentrations of PM₁₀ in Auckland (at Henderson between 1998 and 2000, and Mount Eden, between 1997 and 2000).

At Henderson the 1998 and 2000 concentrations were identical (50 per cent of measurements were 'good', about 45 per cent 'acceptable', and around 5 per cent at 'alert' level), but in 1999 concentrations worsened, with only 30 per cent in the 'good' category, and over 10 per cent in the 'alert' category.

At Mount Eden concentrations deteriorated slightly through the period. In 1997 60 per cent of measurements were in the 'good' category, This dropped sharply in 1998 to around 30 per cent, and only recovered to 40 per cent in subsequent years. The proportion of measurements in the alert category was steady at around 5 per cent, but increased to about 10 per cent in 2000.