The effect of Pb reduction in petrol on the Pb content of kerbside dust in Hong Kong.

Before 1981, Pb in petrol in Hong Kong averaged about 0.84 g/l. Then the Pb level was stepwisely reduced and by early 1987, it was at 0.25 g/l. The effect of Pb reduction in petrol on the roadside environment was assessed by comparing the Pb content in kerbside dust samples (extracted by hot 3.5 M NO3 and analysed by flame AAS) taken in Nov 77-Jan 78 and in Jan 1987 from 37 sites which covered a wide range of traffic density. The arithmetic mean Pb levels for the 1977-78 and 1987 samples were 3280 and 1080 micrograms/g respectively and their difference was highly significant (P = 0.0005, paired t-test). Parallel studies on the levels of Cu, Zn and Mn in the two batches of samples showed no significant changes. Thus Pb reduction in petrol has drastically lowered the metal's contamination in the roadside environment in Hong Kong.