The abovementioned pollution reduction strategies, while not
directly leading to a reduction in PM10 levels, may have resulted in
the chemical composition and toxicity of PM10 changing over time
in Australian cities (Barnett, 2012). For example, the use of reduced
sulphur fuel may result in the contribution of sulphate to the PM10
composition decreasing over time. Similarly, the stricter ADR
emission requirements may result in a reduction over time in the
levels of ambient organic carbon and ammonium nitrate particles
found in PM10 (Dominici et al., 2007). These potential changes in
the chemical composition of PM10 give rise to the question of
whether the toxicity of PM10 has changed over time in Australia.