COVID-19-associated 2020 lockdown: a study on atmospheric black carbon fall impact on human health

The mean mass concentrations of black carbon (BC)(,) biomass burning (BC)(bb,) and fossil fuel combustion (BC)(ff) have been estimated during March–May 2020 (during the COVID-19 outbreak) and March–May 2019 at a semiarid region of Agra over the Indo-Gangetic basin region. The daily mean mass concentration of BC in 2020 and 2019 was 3.9 and 6.9 µg m(−3), respectively. The high monthly mean mass concentration of BC was found to be 4.7, 3.4 and 3.3 µg m(−3) in Mar-2020, Apr-2020, and May-2020, respectively, whereas in Mar-2019, Apr-2019, and May-2019 was 7.7, 7.5 and 5.4 µg m(−3), respectively. The absorption coefficient (b(abs)) and absorption angstrom exponent (AAE) of black carbon were calculated. The highest mean AAE was 1.6 in the year 2020 (Mar–May 2020) indicating the dominance of biomass burning. The mean mass concentration of fossil fuel (BC)(ff) and biomass burning (BC)(bb) is 3.4 and 0.51 µg m(−3), respectively, in 2020 whereas 6.4 and 0.73 µg m(−3), respectively, in 2019. The mean fraction contribution of BC with fossil fuel (BC)(ff) was 82.1 ± 13.5% and biomass burning (BC)(bb) was 17.9 ± 4.3% in 2020, while in 2019, fossil fuel (BC)(ff) was 86.7 ± 13.5% and biomass burning (BC)(bb) was 13.3 ± 6.7%. The population-weighted mean concentration of BC, fossil fuel (BC)(ff), and biomass burning (BC)(bb) has been calculated. The health risk assessment of BC has been analyzed in the form of attributable relative risk factors and attributed relative risk during the COVID-19 outbreak using AirQ + v.2.0 model. The attributable relative risk factors of BC were 20.6% in 2020 and 29.4% in 2019. The mean attributed relative risk per 10,000,000 populations at 95% confidence interval (CI) due to BC was 184.06 (142.6–225.2) in 2020 and 609.06 (418.3–714.6) in 2019. The low attributed factor and attributed relative risk in 2020 may be attributed to improvements in air quality and a fall in the emission of BC. In 2020, due to the COVID-19 pandemic, the whole country faced the biggest lockdown, ban of the transportation of private vehicles, trains, aircraft, and construction activities, and shut down of the industry leading to a fall in the impact of BC on human health. Overall, this was like a blessing in disguise. This study will help in future planning of mitigation and emission control of air pollutants in large and BC in particular. It only needs a multipronged approach. This study may be like torch bearing to set path for mitigation of impacts of air pollution and improvement of air quality.