After enjoying a summer of blue skies, Hongkongers have again been forced to face the harsh reality of dirty air. At 4am yesterday, the Air Pollution Index at the roadside station in Central hit 174, the second highest in the city's history. The highest was recorded at Mong Kok's roadside station: 182 on November 3, 2003. The sky was hazy and buildings on the other side of Victoria Harbour were barely visible. 'It's worse than three months ago. I can barely see the buildings,' said Australian Llewellyn Owens, 28, who visits Hong Kong regularly on business. His three-year-old son, Xavier, has asthma and was suffering from the grime. Owens said pollution would deter him from visiting as a tourist. 'It's not a place for leisure,' he added. Yau Cheuk-chun, eight, was enjoying the weekend with his father outside the Cultural Centre. 'If you live here you have to accept the bad air. You have no choice,' the father said, describing conditions yesterday as 'bearable'. He said conditions would not improve unless all factories in the Pearl River Delta closed. 'I don't think the government here or in the US has the ability to improve air quality,' he said. Ingrid Rossing, 47, watched a traffic jam on a bridge in Central. 'I can smell the exhausts,' said the teacher, who works in Japan and was put off moving to Hong Kong by pollution. A spokesman for the Environmental Protection Department said regional pollution and exhaust fumes had led to high roadside readings. Observatory scientific officer Tong Yu-fai said there had been little wind in the past three days, which meant suspended particles were not blown away. 'This occurs during sunny days with light winds,' he said. Nevertheless, the index dropped after a breeze swept across Hong Kong Island. Professor Alexis Lau Kai-hon, an atmospheric scientist at the University of Science and Technology, said nitrogen oxides emitted by vehicles could combine with the ozone - most of which is believed to originate on the mainland - and form nitrogen dioxide, which contributed to the increase in the pollution index. At 5pm, the API in Central, Causeway Bay and Mong Kok had dropped to 152, 144 and 146 respectively. The government's four-month public consultation on the Air Quality Objectives review ends next month. Greenpeace campaigner Prentice Koo Wai-muk said air quality usually deteriorated after the Mid-Autumn Festival. The roadside index showed air quality was not improving as the government claimed, he added. In March, Australia issued a health alert to nationals about Hong Kong's dirty air. But a Tourism Board survey showed fewer than 20 per cent of visitors were dissatisfied with the air quality in the past three years. In the past five years, the number of hours with poor visibility dropped 30 per cent, according to the Environment Bureau.