evidence: Research has found that wearing a mask (with at least two layers of fabric) is one of the most effective methods Americans can take to slow the spread of the coronavirus. Yet health myths about masks flood social media — people worry that wearing masks will lower oxygen levels or cause carbon dioxide poisoning. Others fear they’ll develop bacterial infections from moist, sweaty masks or weaken their immune system’s ability to fight off colds. Health care professionals have attempted to clarify these misconceptions on social media. A doctor in South Carolina challenged the idea that "oxygen levels drop dramatically while wearing a mask." Dr. Megan Hall tested her oxygen saturation and heart rate using a pulse oximeter in four situations for five minutes at a time: one without a mask, one with a surgical mask, one with a N95 mask and one with a N95 and surgical mask. [...] The American Lung Association recently released a statement addressing the idea that masks make it difficult to breath: "The masks are designed to be breathed through and there is no evidence that low oxygen levels occur."