The study, which appears online Feb. 17 in The Lancet, also noted a surprisingly high use of smokeless tobacco products among both boys and girls.

　　"This is an alarming pattern and suggests that tobacco use, especially among young girls, is on the increase," said Charles Warren, lead author of the paper and research coordinator for the Global Youth Tobacco Survey, from the U.S. Centers for Disease Control and Prevention's Office on Smoking and Health.

　　"The findings suggest that the tobacco-control effort needs to broaden its scope and needs to develop some special program efforts," he said.

　　Danny McGoldrick, director of research at the Campaign for Tobacco-Free Kids, said the findings "should serve as a warning sign that the already incredible toll will only get worse if we don't put in place the interventions we know work."

　　Tobacco use is a major risk factor for lung and other cancers, heart disease and respiratory problems, and is the second leading cause of death worldwide.

　　Experts predict that the number of worldwide deaths annually from tobacco use will double from 5 million in 2005 to 10 million in 2020. And those numbers may be conservative, since they don't fully take into account non-cigarette tobacco use and unexpectedly high rates of smoking among young girls, the researchers said.

　　The new findings come from a school-based survey of about 750,000 students aged 13 to 15 in 131 countries as well as the Gaza Strip and West Bank of Israel. Students answered questions about current tobacco use, exposure to secondhand smoke and susceptibility to smoking.

　　The survey is a joint project of the World Health Organization, the CDC and the Canadian Public Health Association, as well as most WHO member states. The survey surveillance system is the world's largest body of comparable data for youth tobacco use.

　　When the survey started in 1999, little data on tobacco use among young people was available.

　　According to the new survey, nearly 9 percent of students surveyed were current smokers and 11 percent currently used tobacco products other than cigarettes. Use of any form of tobacco was highest among youth in the Americas (22.2 percent) and lowest in southeast Asia (12.9 percent) and the western Pacific (11.4 percent). Smoking was highest in the Americas (17.5 percent) and Europe (17.9) and less than 10 percent elsewhere.

　　The gap in smoking rates between boys and girls was narrower than expected and smaller than the difference between adult men and women.

　　In fact, "in over half the countries, there was no difference between boys and girls in cigarette smoking and that is a very, very different pattern from what the adult data has shown," Warren said.

　　Overall, 18.3 percent of students who had never smoked said they thought they might try smoking in the coming year. Boys were more likely to report this susceptibility than girls.

　　More than 40 percent of the students were exposed to secondhand smoke at home and 50 percent were exposed in public places.

　　Use of tobacco products other than cigarettes was as high or higher than cigarette smoking in many parts of the world.

　　Why the change?

　　"In most cases, country research coordinators are seeing a shift in the cultural acceptance of girls [toward tobacco use]. It's OK for girls to be seen smoking," Warren said. "There's no definitive data but it's an observation."

　　The more pertinent question may be, what should societies do?

　　"The evidence base is showing you need to raise taxes, you need to pass laws and enforce laws on exposure to secondhand smoke," Warren said. "You [also] need to pass laws and enforce the laws on regulating media exposure and advertising regarding pro-tobacco, you need to develop a youth-focused cessation program as a community and probably at the school level, you need to develop public education campaigns in the communities and schools that are reaching the young people, and those campaigns need to not be focused on just boys."

　　"It's not a quick fix," he added. "It's not something you'll be able to do immediately."

　　Some countries have already charted some level of success. The Philippines, for instance, instituted bans on smoking in public places while raising awareness with an active community-education campaign. That country has seen about a 30 percent decrease in young people smoking.

　　The survey authors plan to use the new data to help more countries develop and implement tobacco-control programs.

　　"It's not always the case that we know what to do about horrible public health problems and this is one that is absolutely and completely preventable," McGoldrick said. "Every one of the 5 million deaths from tobacco use around the world is completely preventable."