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Patients with existing respiratory conditions are at risk for developing more severe cases of COVID-19. There are many factors that can contribute to respiratory conditions, including genetic factors, behaviors like smoking, and environmental characteristics like air quality.

However, we can't quantify the direct impact of air pollution on COVID-19. In many areas with high levels of air pollution and large outbreaks of COVID-19, we also see a number of confounding factors, like , which leads to increased transmission between people and larger outbreaks.