Pb levels in petrol were reduced progressively since the 1980s.In January 1991, unleaded petrol was introduced in Singapore and leaded petrol was phased out on 1 July 1998. Significant
reductions in Pb concentration were seen over this time frame, where roadside Pb levels dropped from 1.4 μg/m3 to around 0.1 μg/m3 and remained below that level since 1992.The WHO guideline for annual average Pb levels is 0.5 μg/m3 and Singapore currently complies with this value.