Don't trust your own eyes, trust us, say environmental officials in Beijing. An official yesterday insisted that Beijing's air quality was 'on good or moderate levels' and said the recent haze hovering over the capital was not due to pollution. 'Good air quality does not necessarily mean blue sky,' said Du Shaozhong, deputy director of the Beijing Municipal Environmental Protection Bureau. 'We should judge whether there is pollution by scientific statistics, not by what our eyes can see. 'You might not be able to see things in a [steamy] bathroom, but you would not [conclude that it's due to] pollution,' Dr Du said. Hours after his remarks, an air-pollution reading of 47 major cities released by Xinhua classified the air quality in the Olympic host city as Category III 1 - which is considered harmful to people's health. In fact, Beijing was one of the only two cities on the list whose air quality was classified as Category III 1 - the other was Ningbo . All other major mainland cities had better readings. It was the third day in a row that the air-pollution reading in Beijing was in the III 1 category, which is defined as having the potential to affect people with respiratory problems severely and making breathing difficult for most other people. Beijing has been closing factories and taking cars off the road to improve the air quality as the opening of the Olympic Games is less than two weeks away. Many foreign athletes and trainers have expressed concerns over the pollution problem. Shougang Group, one of the country's biggest steelmakers, and several coking plants have been moved from the Olympic host city, where construction sites have also been ordered to suspend work. More than 3 million cars have been forced since July 20 to run on alternating days based on even or odd numbers on their licence plates, a move expected to reduce about 60 per cent of car emissions. Dr Du again pledged that the government would do what it took to ensure good air quality during the Games. 'Keeping an [acceptable quality of air] for the Olympic Games is a promise made by the Chinese government, and we will honour our commitment,' he said. He discouraged people from wearing masks, saying it was 'absolutely unnecessary'. President Hu Jintao said that 'more meticulous efforts' were needed for the success of the Beijing Olympics, Xinhua reported. Speaking at a meeting of the Politburo, Mr Hu said hosting a successful Olympics was now the country's 'top priority'. He ordered officials to spare no efforts to ensure the event was a success.