Alterations to the urinary metabolome following semi-controlled short exposures to ultrafine particles at a major airport

BACKGROUND: Inflammation, oxidative stress and reduced cardiopulmonary function following exposure to ultrafine particles (UFP) from airports has been reported but the biological pathways underlying these toxicological endpoints remain to be explored. Urinary metabolomics offers a robust method by which changes in cellular pathway activity can be characterised following environmental exposures. OBJECTIVE: We assessed the impact of short-term exposures to UFP from different sources at a major airport on the human urinary metabolome. METHODS: 21 healthy, non-smoking volunteers (aged 19–27 years) were repeatedly (2–5 visits) exposed for 5h to ambient air at Amsterdam Airport Schiphol, while performing intermittent, moderate exercise. Pre- to-post exposure changes in urinary metabolite concentrations were assessed via (1)H NMR spectroscopy and related to total and source-specific particle number concentrations (PNC) using linear mixed effects models. RESULTS: Total PNC at the exposure site was on average, 53,500 particles/cm(3) (range 10,500–173,200) and associated with significant reductions in urinary taurine (−0.262 AU, 95% CI: −0.507 to −0.020) and dimethylamine concentrations (−0.021 AU, 95% CI: −0.040 to −0.067). Aviation UFP exposure accounted for these changes, with the reductions in taurine and dimethylamine associating with UFP produced during both aircraft landing and take-off. Significant reductions in pyroglutamate concentration were also associated with aviation UFP specifically, (−0.005 AU, 95% CI: −0.010 – <0.000) again, with contributions from both landing and take-off UFP exposure. While non-aviation UFPs induced small changes to the urinary metabolome, their effects did not significantly impact the overall response to airport UFP exposure. DISCUSSION: Following short-term exposures at a major airport, aviation-related UFP caused the greatest changes to the urinary metabolome. These were consistent with a heightened antioxidant response and altered nitric oxide synthesis. Although some of these responses could be adaptive, they appeared after short-term exposures in healthy adults. Further study is required to determine whether long-term exposures induce injurious effects.