The nexus between in-car aerosol concentrations, ventilation and the risk of respiratory infection. (December 2021)

• Record Type: Journal Article
• Authors: Kumar, Prashant; Omidvarborna, Hamid; Tiwari, Arvind; Morawska, Lidia
• Is Part Of: Environment international. Volume 157(2021)
• Publication Date: 2021-12
• Subjects: In-car exposure -- COVID-19 transmission -- Respiratory infection -- Low-cost sensors -- Envilution® Chamber -- Transport microenvironments; Environmental protection -- Periodicals; Environmental health -- Periodicals; Environmental monitoring -- Periodicals; Environmental Monitoring -- Periodicals; Environnement -- Protection -- Périodiques; Hygiène du milieu -- Périodiques; Environnement -- Surveillance -- Périodiques; Environmental health; Environmental monitoring; Environmental protection; Periodicals; 333.705
• DOI: 10.1016/j.envint.2021.106814
• Languages: English
• ISSNs: 0160-4120

Abstract

Graphical abstract: Research highlights: Performance of in-car sensors was evaluated under lab/dynamic environments. Driving with WO significantly contributes to daily traffic exposure in the morning hours. WC-RC substantially reduced exposure to PM2.5 /PNC but rapidly elevated CO2 level. Probability of COVID-19 transmission dramatically increased with time in WC-RC. Fresh air and efficient facemasks substantially reduced COVID-19 infection probability. Abstract: We examined the trade-offs between in-car aerosol concentrations, ventilation and respiratory infection transmission under three ventilation settings: windows open (WO); windows closed with air-conditioning on ambient air mode (WC-AA); and windows closed with air-conditioning on recirculation (WC-RC). Forty-five runs, covering a total of 324 km distance on a 7.2-km looped route, were carried out three times a day (morning, afternoon, evening) to monitor aerosols (PM2.5 ; particulate matter < 2.5 μm and PNC; particle number concentration), CO2 and environmental conditions (temperature and relative humidity). Ideally, higher ventilation rates would give lower in-car pollutant concentrations due to dilution from outdoor air. However, in-car aerosol concentrations increased with ventilation (WO > WC-AA > WC-RC) due to the ingress of polluted outdoor air on urban routes. A clear trade-off, therefore, exists for the in-car air quality (icAQ) versus ventilation; for example, WC-RC showed the least aerosol concentrations (i.e. four-times lower compared with WO), but corresponded to elevated CO2 levels (i.e. five-times higher compared with WO) in 20 mins. We considered COVID-19 as an example of respiratory infection transmission. The probability of its transmission from an infected occupant in a five-seater car was estimated during different quanta generation rates (2–60.5 quanta hr -1 ) using the Wells-Riley model. In WO, the probability with 50%-efficient and without facemasks under normal speaking (9.4 quanta hr -1 ) varied only by upto 0.5%. It increased by 2-fold in WC-AA (<1.1%) and 10-fold in WC-RC (<5.2%) during a 20 mins trip. Therefore, a wise selection of ventilation settings is needed to balance in-car exposure in urban areas affected by outdoor air pollution and that by COVID-19 transmission. We also successfully developed and assessed the feasibility of using sensor units in static and dynamic environments to monitor icAQ and potentially infer COVID-19 transmission. Further research is required to develop automatic-alarm systems to help reduce both pollutant exposure and infection from respiratory COVID-19 transmission.