Bills are proposed in the California Legislature as well as in San Francisco that would ban all tobacco from baseball diamonds.

The image of a pitcher squirting out a mouthful of brown sludge into the dirt is ubiquitous in American baseball.

The national pastime and smokeless tobacco are so closely tied that an iconic chewing gum marketed towards children, Big League Chew, mimics a pouch of chaw — also called dip or chew — and features a cartoon baseball character on the packaging.

But pieces of legislature at the state and local levels in California would force players to leave their habits in the locker room.

Today, the San Francisco Board of Supervisors is scheduled to hear the introduction of a bill that would ban tobacco wherever organized sports are played. This goes from weekend recreational leagues in Golden Gate Park to AT&T Park, home of the San Francisco Giants.

Supervisor Mark Farrell, a former smokeless tobacco user and baseball player, told reporters last week the measure was specifically aimed at America’s pastime.

“This will have positive health benefits for our city and for our youth for years to come,” Farrell told the San Francisco Chronicle. “It’s time for the city to step up to the plate and ban smokeless tobacco.”

A similar bill was proposed last week in the state capital. This ban would include the use of smokeless tobacco, cigarettes, and e-cigarettes by players, coaches, managers, and fans.

Players smoking tobacco is already banned by Major League Baseball.

Smoking for fans, however, varies. Some stadiums allow smoking in designated outdoor areas while others already have smoking bans that follow state anti-smoking bans.

The smoking prohibitions in public areas like baseball parks were enacted after decades of scientific evidence showed the dangers of second-hand smoke. While smokeless tobacco may not have direct secondary effects, anti-smoking advocates say it can harm children watching in the stands.

Matthew Myers, president of Tobacco-Free Kids, a nonprofit organization that advocates stronger restrictions on tobacco, told KQED he believes smokeless tobacco use by players goes beyond a personal choice issue.

“This is vitally important. For too long, we’ve witnessed major league baseball players not only endanger their own health, but we’re particularly interested because their use endangers the health of millions of kids because young fans idolize baseball players,” he said.

Major League Baseball currently discourages smokeless tobacco use by players, but their unions have blocked a complete ban.

“We ardently believe that children should not use or be exposed to smokeless tobacco, and we support the spirit of this initiative in California and any others that would help achieve this important goal,” the league said in a statement.

While San Francisco’s proposed ban may be the first of its kind in the nation, the dangers of chewing in the majors was highlighted last year when baseball Hall-of-Famer Tony Gwynn died from complications due to salivary gland cancer.

Before his death, Gwynn attributed his cancer from dipping tobacco that he began using in the minor leagues and continued through his 20 seasons with the San Diego Padres. He was 54 when he died.

Gwynn’s death — along with the state’s five major league baseball stadiums — is one reason Myers says legislation was targeted to begin in California.

Former Boston Red Sox pitcher Curt Shilling has said he believes “without a doubt, unquestionably” his 30 years of chewing on the mound is responsible for his squamous-cell carcinoma in his mouth. While his cancer is in remission, he lost his sense of smell and the majority of his sense of taste.

Other major league stars who continue to use chewing tobacco admit it’s harmful and addictive, but they say it’s also a welcomed stress reliever during games.

“I’m trying to stop,’’ Red Sox second baseman Dustin Pedroia told The Boston Globe after Gwynn’s death. “It’s not a good habit. It’s one of those things, you try like heck. I wish I had never started.”

The proposed bans have sparked debate, a large portion centered around the balance between public health and legislating personal choice.

Oakland A’s outfielder Sam Fuld said the fact that there’s no second-hand smoke means smokeless tobacco isn’t as serious of a health threat as smoking.

“My gut is, that for a vice that has really, really minimal effect on those around them but that has negative physical consequences for the user, I feel it’s something that just should be heavily taxed,” he told the SF Chronicle. “It is a liberty. My gut says that you shouldn’t take that away. Alcohol has a greater effect on nonusers than chewing tobacco. So it should just be taxed.”

The tobacco bans may be debated among politicians and players, but medical health professionals say they have reams of scientific studies that prove the dangers of smokeless tobacco.

Smokeless tobacco, in its many forms, still contains nicotine, which means it can be addictive. The Mayo Clinic points out smokeless tobacco can also cause cancer, cavities, gum disease, heart disease, and precancerous mouth lesions.