Evaluation of the PAH and water-extractable phenols content in used cross ties from the French rail network

- Used railway sleepers were sampled and analyzed for an environmental assessment.
- The creosote content of cross ties was always above 1000 mg kg−1.
- Cross ties showed a high content of PAHs and especially benzo[a]pyrene.
- Water extractable phenols concentrations were below European regulations.
- All cross ties should be considered as a hazardous waste.

Recycling used railway sleepers is a major economic and environmental issue since nearly 50 000 tons of those are incinerated every year in France. Therefore, it appeared essential to determine the real toxicity of sleepers and particularly for very old one. They are treated with creosote, which contains toxic and carcinogen compounds such as polycyclic aromatic hydrocarbons (PAHs). This study aims at measuring the amount of 16 priority PAHs and water extractable phenols in 12 sleepers implemented between 1936 and 1978. Results showed that the creosote content was systematically far above 1000 mg kg−1, even after 76 years ageing. Crossties should then be considered as a hazardous waste according to European regulations. Less creosote and PAHs were detected in the sleepers centers. Moreover, the fraction of volatile PAHs was lower in the surface part, due to their evaporation. It appeared that a long ageing process was not sufficient to remove the major part of volatile PAHs and that they could be yet released in the atmospheric environment. Moreover, most of the treated crossties contained huge amount of the highly toxic benzo[a]pyrene, between 179 mg kg−1 and up to 853 mg kg−1 in wood. In contrast, the study revealed that concentrations of water extractable phenols were well below European regulations (3% by mass of creosote).