Recent studies indicate that despite the improvements in air quality over the decades, air pollution remains a significant concern for public health in America. Surprisingly, the cleaner air has inadvertently facilitated the proliferation of Legionnaires’ disease, according to researchers.
Decrease in SO2 in the air associated with Legionnaires’ disease
A study from the State University of New York at Albany suggests a link between the increase in cases of Legionnaires’ disease and the decrease in sulfur dioxide (SO2) air pollution globally. In the United States, the number of Legionnaires’ disease cases rose significantly from 1,100 in 2000 to almost 10,000 in 2018.
Legionnaires’ disease is contracted by breathing in aerosols containing Legionella bacteria. These bacteria thrive in building water systems like cooling towers, hot tubs, and showerheads. Cooling towers, common in urban areas, can become breeding grounds for Legionella if not maintained properly, leading to outbreaks of the disease.
Various environmental factors such as humidity, temperature, precipitation, and UV radiation are proposed to impact the disease, but they fail to account for its long-term rising trend. Research suggests that mortality rates for the condition range between 10-25%.
The reduction of air pollution has inadvertently led to an increase in Legionnaires’ disease. Researchers Fangqun Yu and Arshad Arjunan Nair suggest that cleaner air has eliminated a crucial factor that prevents the spread of the disease: sulfur dioxide (SO2).
SO2 causes acidity in the air making it inhospitable for legionella bacteria
Airborne water droplets, including those carrying Legionella bacteria, absorb SO2, increasing acidity and toxicity levels, creating an inhospitable environment for the bacteria. Consequently, as SO2 levels decrease due to air quality improvements, the conditions for Legionnaires’ disease to thrive have improved, leading to an increase in cases.
Researchers suggest that as sulfur dioxide (SO2) pollution decreases nationwide, bacteria can survive longer in airborne droplets, potentially increasing the risk of these bacteria reaching human lungs. Analyzing data from New York State, known for its high burden of Legionnaires’ disease, the study found significant correlations between disease incidence and SO2 concentrations, emissions, and the pH of rainwater and cooling tower droplets.
