HONG KONG – OCTOBER 25: A tourist takes a photograph during a cloudy day in front of a billboard featuring photos of the city skyline with a clear sky on October 25, 2013 in Hong Kong. A government warning has been issued after Hong Kong’s environmental protection department reported today that Air Pollution Index results of over 100. Hong Kong’s Air Pollution index has recorded a reading of 189 in Central, this is the highest reading since April 2013. A reading of more than 100 automatically triggers a government warning for people with respiratory related illnesses. Photo by Lam Yik Fei/Getty Images.