Periodic Reporting for period 2 - MMAP-VEX (Measuring and Modelling Air Pollution Within Vehicles – Implications for daily EXposure and Human Health.)
Reporting period: 2022-07-01 to 2023-06-30
According to the World Health Organization (WHO), outdoor air pollution is accountable for at least 4.2 million premature deaths per year, and possibly as high as 8.8 million per year. Air pollution has not only increased acute threats to public health, but also increased the economic burden establishing it as a leading environmental risk factor for health globally. Worldwide, more than 80% of urban residents are exposed to outdoor air pollution levels that exceed the WHO limits. As this outdoor polluted air undergoes exchange with the air inside vehicle cabins, vehicle occupants may suffer elevated exposure to ambient/outdoor air pollutants of varying extents during this time. Additionally, personal air pollution exposure within vehicles varies not only under different ventilation settings, but also during time of the day and road type. The project aims to investigate how the outdoor air quality is a determinable factor of health and personal air pollution exposure in passenger cars. Knowing that in Europe 56% of the population use their cars as the main transportation option, it is essential to understand controllable exposure reduction mechanisms for better management of occupants’ exposure to air pollutants. Specifically the research objectives of the project are to determine the absolute exposure and inhalation dose of vehicle occupants to nitric oxide (NO), nitrogen dioxide (NO2), PM10, PM2.5 PM1 (particulate matter with aerodynamic diameter ≤ 10, 2.5 and 1 µm, respectively), UFP (ultrafine particles with aerodynamic diameter < 300 nm), LSDA (lung surface deposited area of the aerosols), carbon dioxide (CO2) and volatile organic compounds (VOC) relatively to the one directly outside vehicles under different ventilations settings, cabin filters of vehicles and roads. The project’s second research objective is to apply two targeted interventions to investigate the air pollution exposure reduction potential of different cabin air filters and indoor air purifiers. MMAAP-VEX third research objective is to investigate the effect of physical and chemical processes of pollutants to air pollution exposure within-vehicles and how they change with different ventilation and driving conditions and outside - inside sources with experimental and numerical modelling approaches. The final research objective is to develop novel modelling techniques that can estimate personal exposure inside cars depending upon the roadside air pollution levels, ventilation preference and route choice. MMAP-VEX research is critical for effective indoor air quality management policies, alternative, greener commuting strategies and control of daily exposure to air pollution.
Since the beginning of the project we extensively measured air quality within vehicle cabins under different experimental conditions. The vehicles tested included different types (gasoline, diesel, hybrid and electric), had different manufacturing years (2004 – 2020), odometer (3000 – 160000 miles) and varied in size (cabin volume 1.2 – 2.63 m3). We applied a multi pollutant measurement approach in real time where we measured air pollution inside the car cabin (breathing area of the front passengers) and directly outside the car. Overall we used fifteen certified instruments to measure air pollution under different ventilation settings and road type. During the measurement period we applied two different targeted interventions. One included testing of different car cabin air filters under real world driving conditions to investigate the reduction potential of PM2.5 and NO2. For this reason, each car was tested three times once with the filter already in use (either a standard pollen filter or an activated carbon filter), second time with a new standard pollen filter and third time with a new activated carbon filter. Cars that had the biggest variations were also measured again after 3 months of the implementation of the new activated carbon filter to estimate the efficiency of the filter with time. During these experiments MMAP-VEX also examined how commercially available air purifiers car reduce air pollution exposure inside car cabins. Some of the key findings so far can be summarized as:
• Ventilation setting can reduce outdoor air pollution of PM2.5 by >60% and NO2 by >35%, but prolonged use of some ventilation settings might increase CO2 emissions.
• Route choice can reduce in-vehicle exposure by factors of up to 2.0 and 0.5 for PM2.5 and NO2, respectively but changes journey time and emissions.
• Replacing standard ‘pollen’ filters with activated charcoal filters reduces and NO2 by up to 94%, but need to be well maintained as the efficiency of the filter drops by 7.6% every month of use.
• A reduction in the activated carbon filter’s efficiency is observed after the first 7 months of use.
• During these experiments MMAP-VEX estimated the cabin filter efficiency in reducing in-vehicle air pollution exposure with months in use.
• The use of appropriate car cabin filter in conjunction with the optimal ventilation setting can result in 14- fold reduction in-vehicle NO2 and PM2.5 concentrations.
• Commercially available purifiers only improve the air quality inside smaller cabin sized cars
• Factors affecting in-vehicle exposure can be broadly categorized into environmental, vehicle and driving-related
• The biggest environmental factor affecting in-vehicle exposure to NO2 and PM2.5 is on-road air pollution contributing 22.3 and 30% respectively.
• Vehicle related factors include: vehicle age, cabin size, odometer reading, air filter type, window setting, ventilation setting and contribute to 48.7 and 61.3% of in-vehicle NO2 and PM2.5 exposures respectively.
• Driving related factors include: Driving speed, traffic conditions, traffic lights, roundabouts and road high-emitters and contribute to 22 and 7.4% of in-vehicle NO2 and PM2.5 exposures respectively.
• Ventilation setting can reduce outdoor air pollution of PM2.5 by >60% and NO2 by >35%, but prolonged use of some ventilation settings might increase CO2 emissions.
• Route choice can reduce in-vehicle exposure by factors of up to 2.0 and 0.5 for PM2.5 and NO2, respectively but changes journey time and emissions.
• Replacing standard ‘pollen’ filters with activated charcoal filters reduces and NO2 by up to 94%, but need to be well maintained as the efficiency of the filter drops by 7.6% every month of use.
• A reduction in the activated carbon filter’s efficiency is observed after the first 7 months of use.
• During these experiments MMAP-VEX estimated the cabin filter efficiency in reducing in-vehicle air pollution exposure with months in use.
• The use of appropriate car cabin filter in conjunction with the optimal ventilation setting can result in 14- fold reduction in-vehicle NO2 and PM2.5 concentrations.
• Commercially available purifiers only improve the air quality inside smaller cabin sized cars
• Factors affecting in-vehicle exposure can be broadly categorized into environmental, vehicle and driving-related
• The biggest environmental factor affecting in-vehicle exposure to NO2 and PM2.5 is on-road air pollution contributing 22.3 and 30% respectively.
• Vehicle related factors include: vehicle age, cabin size, odometer reading, air filter type, window setting, ventilation setting and contribute to 48.7 and 61.3% of in-vehicle NO2 and PM2.5 exposures respectively.
• Driving related factors include: Driving speed, traffic conditions, traffic lights, roundabouts and road high-emitters and contribute to 22 and 7.4% of in-vehicle NO2 and PM2.5 exposures respectively.
The expected results of the project would help understand key controllable factors that affect in-vehicle air quality. These findings can then be used to raise awareness and inform policies to introduce new indoor air quality standards. For example an inexpensive way to reduce NO2 exposure inside cars is the use and regular change of activated carbon cabin filter which can reduce NO2 levels by 87.4% on average. This will result in significant public health improvements which in turn will have significant socio-economic impacts knowing that at least 56% of the Europeans are using their cars on a daily basis to commute to work. These benefits are likely to be amplified for vehicle occupants spending the greatest periods of time within vehicles, including elderly, mobility impaired commuters and professional drivers. The modelling techniques we developed identified the factors that contribute to in-vehicle air pollution exposure while the machine learning algorithms provided novel tools to estimate these exposures without any knowledge of the actual in-vehicle levels. We estimated that one fifth of NO2 and one third of PM2.5 in-vehicle exposure comes from on-road air pollution while about half comes from the filtration and ventilation options. Such methodologies can be used in areas with little to no information of air quality, whereas the findings can be further used to apply targeted policies in order to reduce personal exposure to air pollution inside cars which are the third most used microenvironment other than home and workspace in Europe.