Field measurements of indoor and community air quality in rural Beijing before, during, and after the COVID-19 lockdown

Abstract

The coronavirus (COVID-19) lockdown in China is thought to have reduced air pollution emissions due to reduced human mobility and economic activities. Few studies have assessed the impacts of COVID-19 on community and indoor air quality in environments with diverse socioeconomic and household energy use patterns. The main goal of this study was to evaluate whether indoor and community air pollution differed before, during, and after the COVID-19 lockdown in homes with different energy use patterns. Using calibrated real-time PM_2.5 sensors, we measured indoor and community air quality in 147 homes from 30 villages in Beijing over 4 months including periods before, during, and after the COVID-19 lockdown. Community pollution was higher during the lockdown (61 ± 47 μg/m³ ) compared with before (45 ± 35 μg/m³ , p < 0.001) and after (47 ± 37 μg/m³ , p < 0.001) the lockdown. However, we did not observe significantly increased indoor PM_2.5 during the COVID-19 lockdown. Indoor-generated PM_2.5 in homes using clean energy for heating without smokers was the lowest compared with those using solid fuel with/without smokers, implying air pollutant emissions are reduced in homes using clean energy. Indoor air quality may not have been impacted by the COVID-19 lockdown in rural settings in China and appeared to be more impacted by the household energy choice and indoor smoking than the COVID-19 lockdown. As clean energy transitions occurred in rural households in northern China, our work highlights the importance of understanding multiple possible indoor sources to interpret the impacts of interventions, intended or otherwise.

Keywords: COVID-19 lockdown; air pollution sources; cigarette smoking; household energy use; indoor and community PM2.5.

FIGURE 1

Time series (A) and box plot (B) of indoor PM_2.5 concentrations in households with different energy use patterns. Heating season (HS) defined as from January 15 to March 15, 2020. Non‐heating season (NHS) defined as from March 16 to April 25, 2020. COVID‐19 lockdown period (HS‐during) is from January 25 to February 25, 2020. Before COVID‐19 lockdown (HS‐before) is from January 15 to February 24, 2020. After COVID‐19 lockdown (HS‐after) is from February 26 to March 15, 2020. Box midline in the right panel indicates the median; the open square symbol in the box indicates the mean value; the borders of the box represent the upper and lower bounds of the interquartile range (IQR); the whiskers of the box extend from the borders of the box to the maximum/minimum data points within 1.5 × IQR; and the points are outliers which are beyond the end of the whiskers.

FIGURE 2

Time series (A) of community PM_2.5 and temperature and box plots (B) of community PM_2.5 concentrations over the heating season and the non‐heating season (NHS), with before‐, during‐, and after COVID‐19 periods also designated. Boxplot features are calculated as described for Figure 1. Outdoor temperature was from the National Oceanic and Atmospheric Administration (NOAA) of the United States (https://www.ncdc.noaa.gov).

FIGURE 3

Time series of indoor‐generated PM_2.5 in smoking (A) and non‐smoking (B) households. “Before” indicates before COVID‐19 lockdown, which is from January 15 to January 24, 2020. “During” indicates during COVID‐19 lockdown, which is from January 25 to February 25, 2020. “After” indicates after COVID‐19 lockdown, which is from February 26 to March 15, 2020.

FIGURE 4

Boxplots of indoor‐generated PM_2.5 by household energy use patterns. Boxplots features are calculated as described for Figure 1. “Before” indicates before COVID‐19 lockdown, which is from January 15 to January 24, 2020. “During” indicates during COVID‐19 lockdown, which is from January 25 to February 25, 2020. “After” indicates after COVID‐19 lockdown, which is from February 26 to March 15, 2020.

FIGURE 5

Diurnal variation of indoor‐generated PM_2.5. Boxplots features are calculated as described for Figure 1. “Before” indicates before COVID‐19 lockdown, which is from January 15 to January 24, 2020. “During” indicates during COVID‐19 lockdown, which is from January 25 to February 25, 2020. “After” indicates after COVID‐19 lockdown, which is from February 26 to March 15, 2020. “Morning” refers to 6 – 10 am; “Noon” refers to 11 am ‐ 3 pm; “Evening” refers to 4 – 8 pm; and “Midnight” refers to 9 pm – 5 am on the next day.