San Francisco — home of the 2014 World Series champion Giants — could become the first U.S. city to ban chewing tobacco from all ballparks and playing fields.

City supervisors on Tuesday voted unanimously to prohibit all tobacco products, including smokeless tobacco, at every athletic venue in the city and county of San Francisco. The ban would apply to both fans and players.

The Campaign for Tobacco-Free Kids backed the new ordinance as part of its “Knock Tobacco Out of the Park” initiative.

The organization is also supporting a statewide bill that would ban tobacco products at major and minor league baseball venues in California, as well as at all interscholastic and intramural play and organized leagues for youths and adults.

The Tobacco-Free Baseball Act, introduced in late February, is now moving through the California Assembly. While smoking is already banned or restricted at ballparks nationwide, the California bill would ban all tobacco products.

“The use of smokeless tobacco in baseball, at any level and in any location, sets a terrible example for the millions of young people who watch the game and far too often see their favorite players using snuff, dip or chew,” the bill’s author, California Assembly member Tony Thurmond, D-Richmond, said in a statement. “We have a great opportunity to protect our players and stand up for kids by getting tobacco out of the game.”

Matthew Myers, president of the Campaign for Tobacco-Free Kids, said in a statement that San Francisco legislators recognize “some simple but important facts — kids see athletes as role models, and when baseball stars use smokeless tobacco the kids who look up to them are much more likely to as well.”

A study published in April by researchers at the University of California, San Francisco, found that nearly 15 percent of high school males use smokeless tobacco, with a higher prevalence among high school students who play sports.

The city ordinance must pass one final vote on April 28 before going to San Francisco Mayor Ed Lee for his signature. The ban would take effect Jan. 1, 2016.

“San Francisco will become the first city to take tobacco out of baseball,” Myers said, “setting a powerful example that all of Major League Baseball and the rest of the country should quickly follow.”