The Aerosol Sampling Project (ASP) has been monitoring lead in fine airborne particles (less than 2.5 micrometres (µm) or millionths of a metre) twice a week for 24 hour periods at 24 sites in a region extending 200 km around Sydney and including the major population areas of Newcastle, Sydney and Wollongong.

The average value for lead in airborne particles collected during 1992 over the whole network was 83 nanograms per cubic metre (ng/m³). The mean monthly winter value (123 ng/m³) was more than a factor of two higher than the corresponding summer value (55ng/m³). The maximum 24 hour average value (1700 ng/m³) for the whole network occurred at Lidcombe in Sydney on 12 July 1992.

Lead levels correlate strongly with the density of motor vehicles and decreased by a factor of twenty in going from the Sydney central business district to areas 200 km inland; lead levels in Newcastle and Wollongong were generally lower than those in Sydney. Lead accounts for between 0.2% and 2.5% of the total particle mass on the filters obtained from the network. At Lidcombe (in Sydney) and Mayfield (in Newcastle), fine-particle lead (less than 2.5 µm) comprised approximately 50% of the total airborne lead (as measured in total suspended particulates [TSP measures all particles less than 50 µm]).