Banning smoking in most workplaces, as Maryland did in 1995, was a major public health advance. So were the decisions by several counties and, in 2008, the state, to extend the ban to bars and restaurants. The ban on smoking in Howard County's parks, which County Executive Ken Ulman plans to announce tomorrow, not so much. Bartenders and waiters faced a real risk of health problems from secondhand smoke as a result of their work conditions, but a family going for a picnic in Centennial Park faces little or no danger from someone taking a puff 100 yards away. Even Dr. Peter Beilenson, the county's health officer, admits that the direct public health benefit of this move is modest.