Recent research has indicated that keeping carbon dioxide (CO2) levels low can help reduce infectious airborne viral loads. While initially focusing on the pathogen responsible for COVID-19, this study has broader implications for limiting the transmission of viruses in spaces with poor ventilation. University of Bristol chemist Allen Haddrell suggests that simply opening a window could be more effective than previously believed. In crowded and poorly ventilated rooms, fresh air with lower CO2 concentrations can deactivate the virus more rapidly.
By studying the SARS-CoV-2 virus in droplets under various environmental conditions, researchers found that its stability is directly affected by the levels of CO2 in the air. Using a novel technique called Controlled Electrodynamic Levitation and Extraction of Bioaerosol onto a Substrate (CELEBS), the team examined how temperature, humidity, and different gas concentrations impact suspended virus particles. While atmospheric CO2 concentrations are currently around 400 parts per million (ppm), indoor environments with limited ventilation can reach levels as high as 3,000 ppm. Under these elevated concentrations, the number of infectious viral particles can be significantly higher than in outdoor air.
Haddrell explains that the alkalinity of exhaled droplets containing the SARS-CoV-2 virus plays a crucial role in its infectiousness. When CO2 interacts with these droplets, it behaves as an acid, reducing their pH and slowing down the inactivation of the virus. In heavily crowded spaces with poor ventilation, CO2 levels can surpass 5,000 ppm, providing a conducive environment for virus survival and transmission. This insight into the relationship between CO2 levels and viral stability sheds light on the occurrence of super spreader events in certain conditions.
Interestingly, the study also revealed variations in stability among different strains of the SARS-CoV-2 virus. For example, the Omicron (BA.2) variant exhibited 1.7 times higher viable viral particle concentrations than the Delta variant after just 5 minutes. This suggests that different viral particles may behave differently in response to environmental factors such as CO2 levels. Further research is needed to explore the associations between CO2 and other types of viruses, potentially explaining the seasonality of respiratory illnesses.
As global CO2 levels continue to rise due to climate change, the research underscores the importance of reducing CO2 emissions to combat the spread of airborne viruses. With projections indicating that outdoor CO2 concentrations could exceed 700 ppm by the end of the century, it is crucial to prioritize global net zero goals. By recognizing the impact of even slightly elevated CO2 levels on virus survival and transmission, researchers believe that these findings can inform the development of effective mitigation strategies in future pandemics. University of Bristol physical chemist Jonathan Reid emphasizes the need for proactive measures based on scientific evidence to mitigate the risks associated with airborne viruses.
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