In conclusion, the observed decline in the short-term effect of
PM10 on mortality in Sydney and Brisbane is suggestive that, even
though average PM10 concentrations have remained steady, the
public health burden of PM10 in Australia is potentially on the
decline. One possible reason for this observed decline being Government
intervention that may have lead to a less toxic chemical
composition of PM10. However, we stress that definitively attributing
such declines to Government intervention, such as regulatory
changes, is difficult and is something that is not shown in this study
(Tolbert, 2007). A useful critique of the methods used in the current
paper, including interpreting the resulting output and other possibilities
for an observed decline in the short-term effect of PM10, is
given in Tolbert (2007). As always the results of time-series studies
of air pollution and mortality need to be interpreted with caution
due to issues such as: (1) The adequacy of ambient PM10 concentrations
as a measure of actual population exposure; and (2) The adequacy of the adjustment for the potentially complex relationship
between mortality and confounding variables