The number of mainland girls who smoke may be higher than the authorities recognise, a Shanghai-based health research team has found. According to a two-year study led by Ma Jin of the Shanghai Jiao Tong University's school of public health, up to 14 per cent of girls on the mainland could be smokers, much higher than the rate estimated in an earlier government study. The China Tobacco Control Blueprint (2012-2015), issued by seven state ministries and the State Tobacco Monopoly Administration last year, put the number of mainland teenagers who smoke at 11.5 per cent. It said only 3.6 per cent of girls smoked, compared with 18.4 per cent of boys. Ma's study, published in The Lancet medical journal last month, also reported that the number of adult women smokers on the mainland reported by authorities could be a third lower than the actual figure. Ma said his survey gave a more accurate picture of mainland tobacco-use in comparison with a similar study led by State University of New York Professor Gary Giovino published in the same journal in August. According to Giovino's study, which analysed tobacco use in 16 countries, more than half of mainland males over the age of 15 smoked. The figure was only 2 per cent for females. The study estimated the mainland has 301 million smokers. The results from his study matched estimates of mainland authorities. Ma said Giovino's study used a self-report method which was regarded as reliable in some Western countries, but it "severely" underestimated the true number of smokers on the mainland. "Young students, especially girls, and adult women tend to cover up their identities as smokers because of pressure from society, which generally regards smoking as bad behaviour for students and women," he said. Ma's study, funded by the Bill & Melinda Gates Foundation and Shanghai's municipal government, canvassed 11,104 people, which included students aged 12 to 20 and their parents from five city districts. The students are from 18 high schools, 45 junior middle schools and five technical schools, and these schools are located in five central and suburb districts in Shanghai "We focus on young people's smoking activities because many smokers initiate this addiction when they are young," Ma said. His team first asked the students to answer a questionnaire, based on a World Health Organisation questionnaire template on juvenile smoking behaviour. The questionnaire found 13.6 per cent of boys and 5.2 per cent of girls smoked. But Ma thought the figures were far too low in light of his everyday observations. So his team adopted a "capture-recapture" method - resampling the schools - to adjust the results. They concluded that the real smoking rates for boys should be 18.3 per cent and 14.2 per cent for girls. "The actual number of smokers in China could be substantially higher than 301 million," Ma wrote in The Lancet . "Such underestimation could hinder our ability to assess the progress of current and future intervention efforts." Compared with Western countries, where a high percentage of teenagers let their parents know of their habit, in Shanghai, only 2.9 per cent of boys' parents and 0.6 per cent of girls' parents were aware that their children smoked, Ma's survey found. He said most students were encouraged to smoke by their peers and ignored all the health warnings because they thought holding a cigarette and blowing a smoke ring was "cool". Wu Yiqun , deputy director of the Beijing-based Think Tank Research Centre for Health Development, said the number of juvenile smokers on the mainland had been increasing over the past decade and children were taking up the habit at a younger age. "Preventing children and teenagers from smoking is vital for our smoke-control campaign because people pick up habits when they are young and smoking is especially bad for their health since their bodies are growing," she said. Three years ago, the Ministry of Education launched a nationwide "non-smoking schools" movement which bans smoking in outdoor and indoor areas at primary and middle schools and kindergartens.