The University of California is banning cigarettes and all other tobacco products from its campuses over the next two years, in a move designed to both protect nonsmokers from secondhand smoke and prevent young people from developing the bad habit.

Students and staff alike will be prohibited from smoking anywhere on a UC campus - including outdoor spaces, parking lots and private residences. There won't be any designated smoking areas.

The main impetus for the policy is to reduce people's exposure to secondhand smoke, UC officials said. But a major benefit, they hope, will be an overall reduction in smoking among those who work or study on the campuses.

"Our young students who come here as freshmen, who don't smoke but come to college and start experimenting, maybe they won't choose to smoke now. That would be a huge gain," said Trish Ratto, manager of UC Berkeley's Health Matters wellness program and a member of the committee that is developing the UC-wide smoking ban.

Smoking has been forbidden at the UC medical centers, including UCSF, since November, and at least seven state university or community college campuses outlaw smoking.

The policy change was revealed this week in a letter from the UC President Mark Yudof to campus leaders. Details such as the exact date that the policy will take effect and how it will be enforced are still not known. Ratto said she expects UC Berkeley and other campuses to beef up programs to help staff and students stop smoking.

"This is a very important milestone in California," said Colleen Stevens, chief of the tobacco control branch of the California Public Health Department. "In other states, most young people start smoking in their teens, but in California, that start date is getting older. This policy will help protect the next generation from suffering the horrible impacts of tobacco."

California has some of the most stringent antismoking laws in the country, and has among the lowest rates of smoking. About 12 percent of Californians smoke, compared with 19.6 percent of people nationwide, according to state and national public health reports.

Smoking rates are even lower in the UC system - about 10 percent of employees and about 8 percent of students smoke regularly, according to a UC Office of the President report. Another 11 percent of students report that they smoke occasionally, or less than once a month.

Student smokers should be a focus of the new smoke-free policy, public health experts said. Multiple studies have shown that the fewer places people are able to smoke, the more likely they will be to quit.

If young people can stop smoking, or never start smoking, before they reach their late 20s, they will be unlikely to ever develop the habit as older adults, said Dr. Stanton Glantz, director of UCSF's Center for Tobacco Control Research and Education.

"Virtually nobody starts smoking after age 24 or 25," Glantz said. "If you can get people through the college ages and a little bit past, and they've either not started or they've stopped, then they're pretty well taken care of."