Black carbon particles contribute to increasing COVID-19 cases

The novel coronavirus or SARS-CoV-2 that causes the novel coronavirus disease (COVID-19), is found in and piggybacks on black carbon (BC) particles emitted during biomass burning. This is according to a recent study conducted by the Indian Institute of Tropical Meteorology located in Pune.

The study also suggests that this is holds true only for black carbon particles and not all PM2.5 particles. The study is based on data collected in Delhi from September to December last year.

PM2.5 consists of black carbon, often called soot and polycyclic aromatic hydrocarbons as well as other chemicals. Some 40 per cent of BC emissions are caused by the open  burning of biomass, 40 per cent by the burning of fossil fuels and 20 per cent by the burning of biofuel.

The COVID-19 infection rate in the national capital increased after a six-month normalcy. This coincided with stubble burning in neighbouring states, the study showed.

The aged biomass BC particles aggregated and reacted with other compounds to grow in size, providing temporary habitat to viruses. This led to a rapid increase in COVID-19 cases. It declined after the crop burning stopped.

The researchers found that the concentration of black carbon “directly corresponds to the speed at which infections spread after the onset of winter and the stubble burning period and then reduces with a declining trend in black carbon due to a reduction in stubble fire counts”.

There is an increase in black carbon emissions and an increase in PM2.5 concentration, which is transported externally from stubble-burning regions.

Black carbon transported from biomass burning sources combines with moisture and other compounds under cooler conditions and acts as a vector for SARS-CoV-2 and hence increases the COVID-19 infection rate.

The study proved that:

• The COVID-19 infection count increase corresponded with an increase in black carbon in the atmosphere and decreased simultaneously with the decrease in black carbon in the atmosphere.
• The COVID-19 death count increased with an increase in black carbon in the atmosphere and decreased when there was a decrease in black carbon in the atmosphere.
• The study also shows that there is an increase in biomass share with an increase in biomass fire counts.

The burning period coincided with a reversal and a steep rise in COVID-19 cases in Delhi, leading to a wave when morbidity and mortality rate were at an all-time high. Thus, the study shows that SARS-CoV-2 has the potential to be transmitted through an aged black carbon-rich environment.