New research suggests that keeping CO2 levels low can help reduce infectious airborne viral loads. This study focused on the pathogen behind COVID-19, but the implications extend to reducing the risk of transmitting viruses in poorly ventilated spaces. According to University of Bristol chemist Allen Haddrell, opening a window to let in fresh air may be more effective than originally thought, especially in crowded and poorly ventilated rooms.
Haddrell and his colleagues used a new technique called Controlled Electrodynamic Levitation and Extraction of Bioaerosol onto a Substrate (CELEBS) to measure the impact of temperature, relative humidity, and different gas concentrations on suspended virus particles. The study found that atmospheric CO2 concentrations are currently around 400 parts per million (ppm), but in closed rooms with a high occupancy, levels can skyrocket to 3,000 ppm. Under these conditions, the number of viral particles that remain infectious can be significantly higher than in outdoor air.
The researchers discovered that the stability of the SARS-CoV-2 virus is directly impacted by CO2 levels in the air. The high pH of exhaled droplets containing the virus is a key factor in the loss of infectiousness. CO2 behaves as an acid when it interacts with droplets, causing the pH to become less alkaline and inactivating the virus at a slower rate. In poorly ventilated, crowded spaces where CO2 levels exceed 5,000 ppm, the risk of viral transmission is significantly higher.
Interestingly, the study found that different strains of SARS-CoV-2 exhibit varying patterns of stability in the air. For example, the Omicron (BA.2) variant showed 1.7 times higher viable viral particle concentrations than the Delta variant after only 5 minutes. This suggests that there may be a lot of variability among viral particle types. Further research is needed to confirm the relationships between CO2 levels and other types of viruses.
The researchers believe that the findings of this study have important implications for mitigating the spread of respiratory viruses in the future. As global warming contributes to the increase in atmospheric CO2 levels, concentrations are projected to exceed 700 ppm by the end of the century. This underscores the importance of global net zero goals in combating the spread of viruses. By understanding the relationship between CO2 levels and viral stability, scientists can develop strategies to save lives in future pandemics.
The study highlights the critical role that CO2 levels play in the transmission of airborne viruses. By keeping CO2 levels low through proper ventilation and air circulation, the risk of viral transmission can be significantly reduced. This research provides a scientific basis for designing effective mitigation strategies that can help prevent the spread of infectious diseases in various environments.