Assessment of air quality in car cabin in and around Paris from on-board measurements and comparison with 2007 data
Introduction
Air quality has become a vital issue in recent years as a result of major concerns regarding the effect of air pollution on public health and the environment. In France, air quality is monitored by independent associations on behalf of public authorities. Airparif, a non-profit organization accredited by the French Ministry of the Ecological Transition, is responsible for this surveillance for the Greater Paris area. The health cost related to air pollution in France was assessed to at least 3 billion Euros per year while the total social cost ranged from 20 to 100 billion Euros (Husson et al., 2015). Furthermore, 650,000 days of work stoppage caused by poor air quality are recorded per year (Husson et al., 2015), while 48,000 deaths per year are attributed to fine particles including those emitted by transportation (Pascal et al., 2016).
Traffic-related emissions affect daily life, since urban populations are exposed to particulate matter (PM) produced by non-exhaust (from the resuspension of road dust in the form of tire and brake wear) and tailpipe (exhaust) emissions. According to the French Environment and Energy Management Agency (ADEME, 2020) and based on data provided by CITEPA (Technical Interprofessional Centre for Atmospheric Pollution Studies), almost 90% of primary particle emissions (PM10, in mass) produced from road transport are generated by Diesel-powered vehicles in France. 15% of PM10 emissions (in mass) come from Diesel vehicles and dust emitted from roads, brakes and tyres. Fine (PM2.5) and ultrafine (PM0.1) particles (UFP) can reach the alveolar region of the human lung with greater efficiency than larger particles (Oberdörster et al., 2005; Thomas, 2013). They can deposit in alveoli due to their small size and damage pulmonary cells, but they can also enter the systemic circulation (Buzea et al., 2007). Recently, Valentino et al. (2016) showed that “maternal exposure to diluted diesel engine exhaust alters placental function and induces intergenerational effects in rabbits”, indicating that UFP can cross the placenta barrier, exposing the fetus to deleterious air pollutants. Ultrafine particles can contaminate any part of the human body including the brain (Buzea et al., 2007). In the last few decades, several studies have demonstrated that particulate air pollution is responsible for early atherosclerosis and systemic oxidative stress (Araujo et al., 2008), for increasing cardiovascular risks (Delfino et al., 2005; Verrier et al., 2002), allergic diseases (Diaz-Sanchez et al., 2003), lung cancer and cardiopulmonary mortality (Pope et al., 2002; Silverman et al., 2012). Considering these issues, it is crucial to obtain a better assessment of commuters's exposure to traffic-related particles, particularly for those traveling in automobiles.
Past studies discussed particle exposure in car cabins, buses or train stations in different cities in order to address the effects of the ventilation settings, types of road or traffic load (Morin et al., 2009; Knibbs and de Dear., 2010; Knibbs et al., 2010; Knibbs et al., 2011; Hudda et al., 2011; Hudda et al., 2012; Joodatnia et al., 2013; Xu and Zhu, 2013; Handakas et al., 2017; Mayer et al., 2018; Nayeb Yazdi et al., 2018; Qiu, Liu, et al., 2019; Matthaios et al., 2020; Torkmahalleh et al., 2020). Exposures of cyclists and pedestrians were also assessed in recent studies (Sturm et al., 2003; Kaur et al., 2007; Int Panis et al., 2010; Rakowska et al., 2014; Polednik et al., 2018; Qiu, Wang, et al., 2019). To date, few on-board data are available in the literature for the megacity of Paris and its inner and outer suburbs, with the last study conducted in 2007 (Airparif, 2009). About 12 million people live in Paris and in the surrounding area: 2.19 million live in Paris, 4.53 million in the inner suburbs and 5.27 million in the outer suburbs. An update of the population exposure to traffic-related PM is therefore needed considering that the vehicle fleet has substantially changed in-between due to new regulations for exhaust-related emissions. 15.5 million daily trips were recorded in 2010 in and around Paris. On average, the duration of a trip is about 78 min per day. Nevertheless, some of these trips can last much longer due to traffic congestion. For home-to-work trips, 44% were done by car (STIF, 2013). Commuters (drivers and passengers) are likely to be exposed to higher levels of air pollution. The infiltration of pollutants from outdoor to the car cabin depends on a number of parameters including the speed of the vehicles, the traffic, the types of roads, the ventilation settings, the vehicle age and mileage (Hudda et al., 2011, 2012; Handakas et al., 2017). We should also note that air pollution levels at the heart of traffic are not measured by regional monitoring networks like the one managed by Airparif (traffic stations are located at a maximum distance of 10 m to assess population exposure in the direct vicinity of roads), but are estimated by modelling by Airparif every hour. However the great variability at the heart of traffic can not be fully included in this model. The study conducted by Airparif (2009) was the first to assess real exposure of commuters from on-board measurements. Ten years after this study it was crucial to conduct a new study to produce updated data representing levels of in-cabin exposure for commuters in and around Paris. It is expected that these results will provide insights on commuter's exposure and its dependence on highly variable conditions such as those observed in inner/outer suburbs, in Paris downtown or on the ring. Furthermore, there is a need to analyze the role of important parameters such as road types, period of the day or vehicle speed on in-cabin PM concentration, some of them have not been considered in the earlier investigations in Paris (Airparif, 2009).
The developed approach discussed in this paper is innovative and complementary to Airparif (2009). It is based on simultaneous measurements of particle number concentrations (PNCs), both inside and outside the car cabin in real driving conditions in and around Paris. This large field campaign was carried out over 2 years (2016–2017). The main objectives were: 1) to identify the levels of commuter's exposure with respect to outdoor concentrations, 2) to discuss the role of road infrastructures (tunnels, ring road, highways), vehicle speed and period of the day on PNC in the car cabin for a given ventilation setting, and 3) to investigate the evolution of commuter's exposure over the last decade. A preliminary study was conducted to define representative daily trips including typical home-to-work routes. These routes were adjusted in order to drive through different roads, including those identified in the literature as the worse in terms of exposure (tunnels, ring road and highways). This was done based on a large statistical database provided by STIF (2013) and in agreement with Airparif (2009) for further comparisons. In the next section, the experimental methodology is detailed. Results are presented in section 3. Comparisons with the last Airparif's study conducted in 2007 for similar conditions are discussed in section 4 together with earlier recent international studies. Conclusions and recommendations for future research are presented in the last part.
Section snippets
On-board measurements
The present on-board measurements focused on the concentrations of PM in number (PNC in #/cm3). For all data, a specific ventilation setting was selected and remained unchanged throughout the campaign. Outdoor air passed through an activated carbon sprayed cabin filter, with the average strength of the fans set to 2/4, with no recirculation or air conditioning. The vehicle windows were kept closed. In addition to the driver, one person was always in the car during the experimental campaign to
General trends
Examples of time series of the measured PNC are presented in Fig. 4 for both outside (in blue) and inside the car cabin (in red). They correspond to route 3 (all sub trips included) on December 7th, 2017. A zoom in on the sub trip “Echo” on the same day is included in this figure. On this sub-trip, the vehicle passed through tunnels (between 17:09 and 17:16 and between 17:30 and 17:33) and on the ring road between 17:20 and 18:00. On both figures, black and green vertical lines mark the
Conclusions and recommendations for future work
In this paper, we report results from an intensive field campaign focusing on car cabin air quality. The first objective was to identify the actual levels of commuter's exposure with respect to outdoor concentrations. The second goal aimed at discussing the role of road infrastructures (tunnels, ring road, highways), vehicle speed and period of the day on PNC in the car cabin for a given ventilation setting. Lastly, we made a comparison of commuter's exposure in Paris and its suburbs between
Declaration of competing interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgements
The authors acknowledge the financial support of ADEME (French Environment and Energy Management Agency). The CAPTIHV project was funded through the call for proposal “CORTEA 2015”. They thank Benjamin Bruge, Romain Rodriguez, Namamoudou Sidiki Keita and Georges Fokoua for their participation in the measurement campaigns as well as Baptiste Recordon, Jérôme Renaud and Aurelien Thorez for their contribution as part of their final year student project. The contribution of Guillaume Fontaine is
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