An unusual bout of smog in Sanya has alarmed locals and tourists alike. They fear the resort city's reputation as a haven from the country's worsening air pollution may be at risk. Locals said a blanket of smog hung over the city in Hainan province for the sixth straight day yesterday, even though environmental authorities continued to rate the local air quality as "good". The local air pollution index (API) hit 83 yesterday, down slightly from a high of 84 on Friday, according to figures from the Ministry of Environmental Protection. The smog was first noticed last Monday, when the API jumped to 67, up from 37 the previous day. While such readings would be welcomed in a northern city like Beijing, where the index can exceed 200, some in Sanya saw the smog as a worrying sign. Shop owner Chen Baochun said he had never seen such persistent smog during his 54 years in the city of more than 685,000, which is widely regarded as having some of the country's clearest skies. Chen said it would be depressing if Sanya became just like any other mainland city. "But I suppose Sanya can no longer be freed from smog if we don't tackle air pollution in a collective and comprehensive way," Chen said. For all of last month, Sanya's API rating was below 50, which is considered "excellent". The Sanya Land Resources and Environment Bureau told the Hainan Island News that a combination of weather patterns, emissions from locally owned vehicles and pollution wafting from Guangdong and other neighbouring regions was to blame for the smog. The local meteorological bureau refused to predict when the smog might end. Su Yi , who visited Sanya from Beijing last October, said his first reaction to the smog reports was that they must have been faked. He said he saw nothing but blue skies and the occasional rain cloud during his stay last year. "Now we have learned a hard lesson about how polluted the air in China is, because the most pollution-free city is no longer clean," Su said. Air pollution has been a growing concern across the mainland, especially in the north.