Impact of biomass induced black carbon particles in cascading COVID-19.

We explore the association of biomass-induced black carbon aerosolized virus with COVID-19 in one of the top-ranked polluted hot spot regions of the world, Delhi, at the time when other confounding factors were almost stable and the pandemic wave was on the declining stage. Delhi was worst affected by COVID-19. However, when it was fast returning back to normal after about 6 months with minimum fatalities, it suddenly encountered a reversal with a 10 fold increase in infection counts, coinciding with the onset of the stubble burning period in neighbouring states. We hereby report that the crop residue burning induced lethal aged Black carbon-rich particles which engulfs Delhi during the post-monsoon months of October-November are strongly associated with COVID-19 and largely responsible for the sudden surge. It is found that the virus efficacy is not necessarily related to any particulates but it is more of source-based toxicity of its component where the virus is piggybacking. We conclude that the aged biomass BC particles tend to aggregate and react with other compounds to grow in size, providing temporary habitat to viruses leading to the rapid increase in COVID-19 cases which declined after the crop burning stopped.