There were no significant differences in Pb loadings for PDD
between suburbs but there were higher values in spring and summer
compared with winter (Supplementary materials).
In contrast to the PDD, during the 4 years of detailed investigation
of TSP in the Sydney suburb of Rozelle, Pb concentrations displayed
a maximum in late autumn-start of winter (Figure 4) [32]. Similar
trends have been observed in other Sydney suburbs (Figure 4) [34].
The higher Pb values in the autumn-winter months are probably
related to thermal inversions typical of the cold season or to drier
conditions during this period compared with summer. On the other
hand the higher Pb contents in summer for the PDD may arise from
the propensity of residents for open doors and windows in summer and
the higher temperatures giving rise to dust which may then enter the
residence. The decreasing Pb concentrations over time (p 0.008) reflect
the decreasing use of Pb from gasoline, terminated in 2002.