The creosote content of used railway crossties as compared with European stipulations for hazardous waste

Through the history of railways, wooden crossties impregnated with potentially hazardous creosote tar have supported the rails. With impregnated crossties having a lifespan of approximately 50 years, their creosote content is considered as quite safely stored while in dug-down usage. This situation of relative safety does, however, change into acute risk upon replacement and destruction. Carrying a highly flammable content, creosote crossties discharge a pulse of carcinogenic PAH compounds if burnt as ordinary waste. Safe destruction is therefore required if concentrations exceed a critical limit stipulated by the European Union. Since safe destruction is a process of considerable expense, there is a tendency among financial stakeholders to underestimate the creosote content of used railway crossties. In order to actually test whether concentrations generally exceed the critical limit, a set of used creosote ties was therefore sampled while still situated in the railway embankment. With a standard sum of sixteen PAH compounds used as an expression of their total creosote content, the generic concentration was formally inferred and found to significantly exceed the critical limit. The same applies to the fraction of seven carcinogenic PAH compounds, that alone exceed the stipulated limit for hazardous waste. It was also found that the material of railway embankments, whether or not the crossties were used in switches and/or railway yards, and sample depth within the crosstie, has a significant effect on creosote concentrations. Regardless of the status of these factors, the concentrations significantly exceed the critical limit that defines hazardous waste within the European Union. (c) 2008 Elsevier B.V. All rights reserved.