New research has suggested that maintaining low levels of CO2 can help reduce infectious airborne viral loads. While the study primarily focused on the virus responsible for COVID-19, its findings have significant implications for minimizing the risk of transmitting viruses in environments with limited ventilation.
According to University of Bristol chemist Allen Haddrell, opening a window to let fresh air in could be more effective than previously believed, especially in crowded and poorly ventilated spaces. Fresh air with lower concentrations of CO2 has the potential to deactivate the virus at a faster rate.
Researchers utilized a new technique called Controlled Electrodynamic Levitation and Extraction of Bioaerosol onto a Substrate (CELEBS) to measure how different environmental conditions affect the infectiousness of the SARS-CoV-2 virus while suspended in droplets. The study revealed that atmospheric CO2 concentrations typically hover around 400 parts per million (ppm). However, in crowded indoor settings, CO2 levels can skyrocket to 3,000 ppm or even exceed 5,000 ppm in highly crowded, poorly ventilated environments.
Haddrell and his team discovered that viral particles can remain infectious at levels ten times higher under elevated CO2 concentrations than in outdoor air. The researchers hypothesized that the high pH of exhaled droplets containing the virus plays a significant role in the virus’s loss of infectivity. CO2 acts as an acid when interacting with droplets, reducing their alkalinity and slowing down the inactivation rate of the virus.
Variability Between Different Virus Strains
Interestingly, the study found that various strains of SARS-CoV-2 exhibit different patterns of stability in the air. For example, after five minutes, the concentration of viable viral particles was 1.7 times higher for the Omicron (BA.2) variant compared to the Delta variant. This suggests that there may be significant variability in the behavior of viral particles.
While further research is needed to establish the relationship between CO2 levels and other types of viruses, the researchers believe that these findings could potentially explain why many respiratory viruses exhibit seasonality. Colder weather conditions may lead people to spend more time indoors, increasing their exposure to indoor air with higher CO2 levels.
As concentrations of CO2 in the atmosphere continue to rise due to global warming, the study underscores the importance of achieving global net-zero goals. Predictions suggest that CO2 levels could exceed 700 ppm by the end of the century, which could significantly impact virus survival and transmission rates.
The researchers emphasize the critical need for mitigation strategies based on these findings to potentially save lives in future pandemics. University of Bristol physical chemist Jonathan Reid concludes that understanding the relationship between CO2 levels and viral transmission could serve as a scientific foundation for developing effective prevention and control measures.
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