The home of the San Francisco Giants may become the first city in the nation to outlaw chewing tobacco from its playing fields.

Supervisors on Tuesday voted unanimously to prohibit the use of smokeless tobacco at athletic venues, specifically singling out baseball, which has a long history of players masticating and spitting tobacco juice in view of children who worship them.

That is not the right message to send to children, said Mark Farrell, chief sponsor of the legislation.