Monitoring steel bridge renovation using lead isotopic tracing

Monitoring removal of lead (Pb) paint from steel structures usually involves analysis of 26 environmental samples for total lead and determination of blood Pb levels of employees involved 27 in the Pb paint removal. We used high precision Pb isotopic tracing for a bridge undergoing Pb 28 paint removal to determine if Pb in the environmental and blood samples originated from the 29 bridge paint. The paint system on the bridge consisted of an anti-corrosive red Pb primer top- 30 coated with a Micaceous Iron Oxide (MIO) alkyd. Analysis of the red Pb primer gave uniform 31 isotopic ratios indicative of Pb from the geologically-ancient Broken Hill mines in western New 32 South Wales, Australia. Likewise waste abrasive material, as anticipated, had the same isotopic 33 composition as the paint. The isotopic ratios for other samples lay on 2 separate linear arrays on 34 a 207Pb/204Pb versus 206Pb/204Pb diagram, one largely defined by gasoline and the majority of the 35 ambient air data, and the other by data for one sample each of gasoline and ambient air and 36 underwater sediments. Isotopic ratios in background ambient air samples for the project were 37 characteristic of leaded gasoline. Air sampling during paint removal showed a contribution of 38 paint Pb ranging from about 20 to 40%. Isotopic ratios in the blood of 8 employees prior to the 39 commencement of work showed that 6 of these had been previously exposed to the Broken Hill 40 Pb possibly from earlier bridge paint removal projects. One subject appeared to have increased 41 exposure to Pb probably from the paint renovations