Polycyclic aromatic hydrocarbon (PAH) levels in environmental media potentially impacted by reused or stored creosote-treated railway ties.

Abstract

Disused creosote-treated railway ties are reused in France and many other countries and, in particular, for landscaping and other residential uses. Given the lack of data on the environmental fate of creosote-derived compounds released from used railway ties, a survey of different environmental media (i.e. soil, sediment, surface water, plants and outdoor air) was carried out at six sites located in France where old creosote-treated railway ties are stored or reused for different purposes. Maximum total polycyclic aromatic hydrocarbon (PAH) concentrations measured in soils ranged from 2 to 140mg/kg dry weight. PAH impacts were limited both vertically and horizontally to several centimetres from the railway ties. At two sites, PAH levels in plants (up to 140μg/kg fresh weight) appeared correlated to the levels measured in soils, suggesting a transfer from soils to the plants. PAHs in sediment were measured at concentrations of up to 280mg/kg dry weight. As observed in soil, PAH concentrations decreased rapidly further away from the railway ties. Principal component analysis and hierarchical clustering on principal components indicate that PAHs detected in soils and sediments originated from unweathered to severely weathered creosote and could be strongly influenced by urban background. Results on outdoor air measurements show a degradation of air quality above old and fresh railway tie storage areas at a railway station and to a lesser extent in their vicinity. However, this degradation was low to moderate when compared to French regulatory values, ambient background levels reported in France, as well as health-based air comparison values.