I&#x27;m studying abroad in Beijing right now, and my throat began to hurt even at lower levels of PM2.5 simply because I wasn&#x27;t wearing a mask. I&#x27;m very surprised at the number of people who don&#x27;t wear a mask; they either don&#x27;t value their health or don&#x27;t know how bad the air is because they&#x27;ve been accustomed to it.