Sampling of Asphalt for PAH and Coal Tar


We were on site at Nottingham recently for a client sampling the Asphalt in the carriageway to determine if it contained Coal Tar and thus elevated levels of PAH.

Waste classification.

Coal tar is classified as carcinogenic due to its high concentration of Polynuclear Aromatic Hydrocarbons (PAHs) – more that 15,000 times that found in bitumen. Consequently, waste tar bound road planings are considered to be hazardous waste (European Waste Code 17 03 01* bituminous mixtures containing coal tar) where the level of coal tar is >0.1% w/w (1,000 mg/kg). Even when treated, normally by using a binding agent such as cold bitumen foam mix, they are still considered to be hazardous waste and their subsequent use in construction requires an environmental permit to be registered with the Environment Agency.

Coal tar identification process.

The presence of coal tar can have major implications to a construction project, due to the health and safety issues posed by handling the material as well as the additional cost that comes with the removal and disposal of a hazardous waste. The early identification of tar bound material can therefore act as an early warning to Project Managers and Designers involved in highways maintenance projects and can be be vital in reducing project costs and delays.