Case Study of Worker Exposure to Coal tar Containing Paving Materials on a Routine Paving Project in Iowa

Abstract

The potential for unknown exposure of present day highway paving workers to coal tar products is of concern to the asphalt paving industry. A case study describing this type of situation is the subject of this report. The project specifications called for the contractor to pulverize and re-compact the entire 230 mm (9 inches) of existing pavement and then pave the pulverized layer with a new HMA layer. Discovery of the presence of mix containing coal tar in the bottom 75 mm (3 inches) of the existing pavement led to a redesign of the project. A decision was made to mill only the upper most 75 to 87 mm (3 to 3.5 inches) of pavement to isolate the coal tar mix from the workers. Initial analysis of bitumen extracted from cores of the top 88 mm (3.5 inches) of pavement did not show the presence of coal tar chemicals. However, samplers mounted on the equipment for 6 hrs during the redesigned milling process showed the presence of coal tar type chemicals extracted from the bitumen coated dust particles captured on the samplers using infrared and GC/MS analysis.