Sources of lead in urban dust: identification of a contribution from newspaper printworks.

High levels of lead in pavement dusts in parts of central London have been traced to newspaper printworks in the area. Concentrations exceeding 5000 micrograms g-1, the interim 'action level' adopted by the Greater London Council, extend up to 150 m from the works, with levels of greater than 200 000 micrograms g-1 encountered close to the exit of one works. By contrast, average levels alongside 14 major roads elsewhere in London ranged from 1360 to 3400 micrograms g-1. Identification of the printworks as the probable source was based on the spatial distribution of the lead-in-dust concentrations. Confirmation came from the close association between lead and tin concentrations, tin being a constituent of the lead alloy used in the printing industry. Such an association was not found in dusts contaminated by lead from petrol or paint. Tracking out on shoes and clothing, and possibly vehicles, is the most likely route by which the lead is leaving the works.