The effect of COVID-19 restrictions on particulate matter on different modes of transport in China

Abstract

Since the COVID-19 pandemic, ventilation on transport has been improved to control the aerosol transmission. We utilized portable monitors to measure real-time concentrations of PM 10 , PM 2.5 , PM 1.0 and black carbon (BC) on six modes of transport and estimate personal exposures under the epidemic prevention. The mean concentrations of PM 10 , PM 2.5 , PM 1.0 and BC measured on transport were 18.8 ± 19.4, 16.6 ± 16.5, 12.2 ± 10.8 and 4.1 ± 6.9 μg/m 3 , respectively. It reduced PM levels on subway to apply the full fresh air mode rather than partial recirculation mode. Airplane had the lowest concentrations and the highest decay rates, implying the most efficient ventilation and filtration. PM were higher on intra-city transport than inter-city, and significantly increased on arrival at stations. BC and BC/PM ratios were higher on road transport than rail transport, indicating the contribution of exhaust emissions. The ventilation mode to exchange air with the outside and the positive association between concentrations and decay rates on high-speed train suggested filtration efficiency should be improved simultaneously with enhancing ventilation. Wearing facemasks on transport further protects passengers against PM exposure, which reduced personal exposure concentrations on four modes of transport lower than 10 μg/m 3 , the World Health Organization guideline.

In-train particulate matter (PM10 and PM2.5) concentrations: Level, source, composition, mitigation measures and health risk effect – A systematic literature review

“…From the eligible articles measuring the in-train concentration of PMs, 52% of the studies were performed in Asia, with China having a more significant fraction of 29 publications, as shown in Figure 3. From the publications in China, Shanghai has a total of six publications, [26][27][28][29][30][31] followed by Hong Kong with five publications, [32][33][34][35][36] Beijing with four publications, 23,[37][38][39] Taiwan with three publications, [40][41][42] Nanjing and Xi'an have two publications each, [43][44][45][46] and Guangzhou, 47 Foshan, 48 Suzhou, 49 Tianjin, 9 Yangtze 50 and Zhengzhou, 51 have one publication each. A publication was also found for the northern part of China.…”

“…In most cases the selected studies compared between underground, ground and above ground in-train PM concentration, 6,8,9,23,27,28,34,35,[39][40][41][42]49,52,54,61,75,77,82 or between divers transporting modes, 6,26,32,35,36,39,43,[45][46][47][48]50,51,57,58,60,64,67,69,72,83,85,87,88,90 or in different seasons of the year (summer, winter, autumn, spring and autumn). 6,26,27,35,43,46,49,…”

“…Source originating people's activities in train Smoking 78 Cooking 30 Passenger density 27,28,31,43,64 Presence and movement of passengers 38,40,62,106 Resuspended materials from passengers and luggage from the carriage floor 28,31,40,64,78 Sources originating from trains operation Doors and windows opening 29,37,61,65,73,74,79 Train arrival/departure 37 Air conditioning/ ventilation system 26,28,43,56,69,75 Inorganic metallic source from subway station internal facilities 52 Air exchange between train and tunnel 65,74 Sources originating from the mechanical movement of train parts Steel abrasion/wear of parts 58,97 Friction between railway lines and the rail wheels 9,52,58,62,86…”

“…Construction activities/materials 62,89 Poor maintenance 47 PM from stations 26,43,82 consequently. However, the PM concentration at the ground level section was lower due to clean air entering the train through the window, creating a 'washing effect'.…”

Public face masks wearing during the COVID-19 pandemic: A comprehensive analysis is needed for potential implications

“…A subsidiary benefit of wearing facemasks has been a decrease in the exposure of wearers to particulate matter (PM) ( Lin et al, 2021 ). Numerous studies allude to a positive correlation between PM levels with respect to the transmission and fatality rates of COVID-19 ( Wang et al, 2020 ; Zhang et al, 2020 ; Zhu et al, 2020 ).…”