Abstract
Exposure to traffic-related air pollution (TRAP) has been associated with adverse health outcomes but underlying biological mechanisms remain poorly understood. Two randomized crossover trials were used here, the Oxford Street II (London) and the TAPAS II (Barcelona) studies, where volunteers were allocated to high or low air pollution exposures. The two locations represent different exposure scenarios, with Oxford Street characterized by diesel vehicles and Barcelona by normal mixed urban traffic. Levels of five and four pollutants were measured, respectively, using personal exposure monitoring devices. Serum samples were used for metabolomic profiling. The association between TRAP and levels of each metabolic feature was assessed. All pollutant levels were significantly higher at the high pollution sites. 29 and 77 metabolic features were associated with at least one pollutant in the Oxford Street II and TAPAS II studies, respectively, which related to 17 and 30 metabolic compounds. Little overlap was observed across pollutants for metabolic features, suggesting that different pollutants may affect levels of different metabolic features. After observing the annotated compounds, the main pathway suggested in Oxford Street II in association with NO2 was the acyl-carnitine pathway, previously found to be associated with cardio-respiratory disease. No overlap was found between the metabolic features identified in the two studies.
Highlights
Exposure to traffic-related air pollution (TRAP) has been associated with adverse respiratory and cardiovascular outcomes, both in healthy and susceptible subjects (W.H.O, 2013)
In the TAPAS II study, two participants were excluded from the analysis due to missing metabolomic data, resulting in 28 participants with complete data
This study, together with (Vlaanderen et al, 2017; Ladva et al, 2017), represents one of the first agnostic projects investigating the effect of short-term exposure to traffic-related air pollutants (TRAP) on the metabolome, utilizing two experimental studies with a crossover design, alternating higher and lower TRAP
Summary
Exposure to traffic-related air pollution (TRAP) has been associated with adverse respiratory and cardiovascular outcomes, both in healthy and susceptible subjects (W.H.O, 2013). Our previous observations in the experimental Oxford Street I study described a reduction of up to 6.1% in the forced expiration volume in 1 s (FEV1) and up to 5.4% in the forced vital capacity (FVC) among subjects walking in Oxford Street, a street in London with heavy exposure to diesel-related TRAP. These reductions were significantly larger compared with exposure in Hyde Park, a green area close to Oxford Street and subject to lower TRAP exposures (p-value = 0.04 and p-value = 0.01 respectively) (McCreanor et al, 2007). Cardiovascular and pulmonary mortality have been associated with long-term exposure to air pollution (Hoek et al, 2013)
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