Shenzhen's quality of life is deteriorating as problems with food safety, pollution and traffic congestion persist. A recently released white paper by the Shenzhen Bureau of Quality and Technical Supervision assessed a wide range of issues, from the quality of air to that of industrial products. While the overall quality of industrial products made in the city improved steadily last year, quality of life showed worrying signs of deterioration, the Shenzhen Special Zone News reported. The annual white paper described the city's general environment as worrying. Smog and bad-air days are becoming increasingly common, with more than 130 bad-air days last year, the most on record. The paper said Shenzhen now had one of the mainland's worst acid-rain problems. Most of its rivers were polluted and samples of their water failed national standards. Food safety has also become a big public concern. Nearly 30 per cent of food sold in markets failed to meet government standards, an increase of 12 percentage points on 2003. The bureau also randomly checked 714 food products made in Shenzhen, and 13 per cent were found to be substandard, about 6 percentage points more than the previous year. One tenth of wet-market vegetables contained pesticide residues higher than the approved level. About 5 per cent of meat products contained hazardous chemicals. The problem of traffic congestion also persisted, the white paper said, and the number of flight delays recorded at Shenzhen Airport was rising. Thirty-six per cent of flights did not take off on time last year, up 7 percentage points on 2003. Shenzhen Airport now had the second-worst record for delays on the mainland, the paper said. Shenzhen is one of the mainland's most developed cities after decades of rapid economic growth. But this growth is often achieved at the expense of its environment. In an earlier nationwide survey, Shenzhen failed to make the list of the 10 best mainland cities in which to live, falling behind Hangzhou , Qingdao and Chengdu , which are less economically developed but have cleaner air and better environments. Feng Haizhu, a company manager in Shenzhen, said: 'I have to say the air and water in Qingdao are much better than here. Making money is important but money does not always give you a comfortable life.'