Abstract
The Tamil Nadu Air Pollution and Health Effects study (TAPHE-2) aims to evaluate the relationship between air pollution and birth outcome in a rural-urban cohort of 300 pregnant women. Due to COVID-19 related lockdowns, some TAPHE-2 activities were delayed; however, continuous indoor and outdoor air quality data were collected in and around Chennai, India. We report here the impact of graded COVID-19 lockdown on indoor particulate matter (PM2.5 and PM10) levels based on calibrated data from affordable real-time PM sensors called atmos™ and ambient PM levels from publicly available regulatory monitors. The study period was between 11 March and 30 June 2020 (i.e., 100 days of continuous monitoring), which coincided with four phases of a nationwide graded lockdown. Field calibration coefficients for the atmos PM were derived by collocating them with reference-grade PM monitors. The normalized root mean square error (NRMSE) of the atmos hourly PM2.5 (PM10) improved from 41% to 15% (33% to 18%) after applying the field calibration coefficients. Lockdowns resulted in significant reductions in indoor and ambient PM levels, with the highest reduction observed during lockdown phase 2 (L2) and phase 3 (L3). Reductions as high as 70%, 91%, and 62% were observed in ambient PM2.5, indoor PM2.5, and indoor PM10 relative to pre-lockdown levels (PL), respectively. The indoor PM2.5/PM10 ratio decreased during the lockdown, suggesting a decline in the fine mode dominance in PM10. The indoor-to-outdoor (I/O) ratios in PM2.5 marginally increased during L1, L2, and L3 phases compared to that of PL levels, suggesting an uneven reduction in indoor and ambient PM2.5 levels during the lockdown.
Highlights
IntroductionThe annual average population-weighted PM2.5 exposures in India have been increasing steadily from 62 μg m–3 in Aerosol and Air Quality Research | https://aaqr.org in 2010 to 83.2 μg m–3 in 2019 (HEI, 2020)
We report here the impact of graded COVID-19 lockdown on indoor particulate matter (PM2.5 and PM10) levels based on calibrated data from affordable real-time PM sensors called atmosTM and ambient PM levels from publicly available regulatory monitors
The study evaluated the impact of graded COVID-19 lockdown on the indoor and ambient PM levels in Chennai, a megacity in South India
Summary
The annual average population-weighted PM2.5 exposures in India have been increasing steadily from 62 μg m–3 in Aerosol and Air Quality Research | https://aaqr.org in 2010 to 83.2 μg m–3 in 2019 (HEI, 2020). These exposure levels are among the highest in the world—higher than China (1.7×), Nigeria (1.2×), Bangladesh (1.3×), Pakistan (1.3×), Brazil (7×), the United Kingdom (8×), and the United States (11×) (HEI, 2020). The current state of air pollution in India poses a serious challenge to public health
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