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Background In the last decades, traffic related air pollutants (TRAP) have decreased in response to the implementation of stricter emission standards and to new technologies in automobile fleet. Despite these improvements, taxi drivers remain highly exposed to TRAP due to their proximity to the “traffic source” and the significant amount of time spent in traffic. Thus, we aimed to identify the determinants of Parisian taxi drivers’ exposure to ultrafine particles (UFP) and black carbon (BC), pollutants of recent interest, inside their vehicles.MethodsIn this cross-sectional study, we studied 499 trips conducted by 50 Parisian taxi drivers from PUF-TAXI project. UFP and BC were measured inside taxis by Diffusion Size Classifier Miniature® and microAeth® AE51, respectively, for 9 hours during normal service. Data on vehicles and trips characteristics were collected by questionnaires and face to face interviews. Associations between pollutants levels and their determinants were analyzed using Generalized Estimating Equations (GEE) model adjusting for potential confounders. ResultsUFP (32.3 ± 37.5 pt/cm³) and BC (3.3 ± 2.3 μg/m³) mean concentrations per trip inside taxi vehicles were moderately correlated (r= 0.3, p <0.001). The analyses showed that levels of UFP and BC inside taxi vehicles were greatly influenced by ventilation settings. The use of air-conditioning (A/C) with closed windows reduced UFP and BC by 53% and 19%, respectively. However, maximum air protection was obtained when both A/C and air recirculation were on. Vehicles speed, trips destinations were also significant determinants of in-taxis UFP and BC levels. In addition, the variability of BC levels inside taxis depended significantly on ambient air pollution, humidity and trip duration.ConclusionsOur results suggest that exposure to UFP and BC inside vehicles can be reduced significantly through simple preventative measures likely to be adopted by professional drivers as well as by all commuters.