CO₂ Levels Affect Virus Spread
Researchers at the University of Bristol have found that higher concentrations of carbon dioxide (CO₂) in the air can lead to increased airborne transmission of viruses.
Dr. Allen Haddrell, a chemist at the university, says that opening windows could have a greater impact than previously thought, especially in crowded and poorly ventilated spaces. Fresh air, which has lower CO₂ levels, causes viruses to become inactive much faster.
Haddrell and his colleagues measured the ability of SARS-CoV-2 to remain infectious as an aerosol in droplets under different environmental conditions. They found that the concentration of CO₂ in the air directly affected the stability of the virus.
How CO₂ Affects Viruses
The team used a novel technique to measure how different temperatures, relative humidity, and gas concentrations affected airborne virus particles. In the atmosphere, CO₂ levels are typically around 400 parts per million (ppm). However, in occupied indoor spaces, CO₂ levels can spike to around 3,000 ppm. The researchers found that the number of infectious virus particles at this higher concentration could be as much as 10 times higher than outdoors.
"The higher pH of exhaled breath droplets containing SARS-CoV-2 is likely a key factor in reducing its infectivity. CO₂ acts as an acid when it mixes with water droplets. This makes the droplets less alkaline, which causes the virus inside them to become inactivated at a slower rate," Haddrell explains.
Furthermore, in poorly ventilated, crowded environments, CO₂ levels can exceed 5,000 ppm. Haddrell notes that this relationship could shed light on why superspreading events can occur under certain conditions.
Climate Change and Virus Spread
Different strains of SARS-CoV-2 exhibit different stabilities in the air. While more research is needed to confirm the relationship between CO₂ and other types of viruses, the researchers suspect that these differences could explain why many respiratory viruses are seasonal.
As the weather gets colder, people tend to spend more time indoors, increasing their exposure to higher CO₂ levels. Outdoor CO₂ levels are also rising due to global warming, with predictions suggesting levels could exceed 700 ppm by the end of the century.
"This work also emphasizes the global importance of achieving net zero, by showing that even modest increases in CO₂, which is rising due to climate change, can significantly increase the survival of viruses and increase the risk of them spreading," Haddrell adds.
Implications for Future Pandemics
"These findings could inform the scientific basis for designing mitigation strategies to save lives in any future pandemics," concludes Dr. Jonathan Reid, a physical chemist also at the University of Bristol.
The study has been published in the journal Nature Communications.
Summary:
- Higher CO₂ levels in the air lead to increased airborne transmission of viruses.
- Opening windows and improving ventilation can reduce CO₂ levels and help prevent viral spread.
- Different strains of viruses exhibit different stabilities in the air, which may contribute to seasonal patterns.
- Rising CO₂ levels due to climate change could increase the risk of virus spread in the future.