--- ---  # San Francisco Bans Chewing Tobacco at Sports Venues  by [Olivia B. Waxman](https://time.com/author/olivia-b-waxman/)  ## Olivia B. Waxman Staff Writer May 9, 2015 2:57 PM UTC  A packed, sunny day at AT&T Park on July 10, 2013, in San Francisco. A packed, sunny day at AT&T Park on July 10, 2013, in San Francisco.George Rose—Getty Images  by [Olivia B. Waxman](https://time.com/author/olivia-b-waxman/)  ## Olivia B. Waxman Staff Writer May 9, 2015 2:57 PM UTC On Friday, San Francisco became the first American city to ban smokeless tobacco—chewing tobacco and “moist inhalable snuff”—at sports venues. The new ordinance, signed by Mayor Ed Lee, goes into effect on Jan. 1, 2016\. Violators will be asked to leave the playing fields (where cigarette and cigar smoking is already banned), the Associated Press reports. Anti-smoking groups [argue](http://time.com/3722784/chewing-tobacco-ban-california-baseball/) that a ban on smokeless tobacco—which has been linked to cancer and nicotine addiction—sends the right message to kids who look up to the players. But San Francisco Giants pitcher Matt Cain said the measure may be hard to enforce, noting that coffee pouches resemble tobacco pouches, according to an article on [the team’s website](http://m.giants.mlb.com/news/article/123229214/giants-await-more-info-on-san-franciscos-new-smokeless-tobacco-ban). The state Assembly is still considering a bill banning tobacco use—electronic cigarettes included—wherever there’s a baseball game, the AP reports. _Read next:_ [_Why Lawmakers Want Smokeless Tobacco Thrown Out of the Homes of a National Pastime_](http://time.com/3722784/chewing-tobacco-ban-california-baseball/) ### See The Tobacco Leaves That Could Cure Ebola  Tobacco plants are grown for six weeks in the Medicago greenhouse in Quebec City so their leaves are large enough to serve as a factory for making antibodies. The plants are not modified or genetically altered in any way during this time. Mathieu Belanger—Reuters  Researchers at Icon Genetics in Germany prepare the DNA coding for antibodies that can neutralize Ebola. These genes are inserted into a soil bacterium that easily infects the tobacco plant cells. Once in the cells, the gene is treated like any other plant gene and the plant starts churning out the antibodies. Sean Gallup—Getty Images  To infect the leaves with the antibody-containing bacteria, the plants are submerged in a water solution of the loaded bacteria. Plant cells have plenty of empty spaces filled with air, so a vacuum removes the air and the water, along with the bacteria and antibody genes, flow in. Mathieu Belanger—Reuters  The leaf at the bottom has not been treated. The leaf on top is now an antibody-making factory. The plant's normal machinery starts making the antibody as if it is a plant protein. Mathieu Belanger—Reuters  Researchers at Icon Genetics grind the leaves down to filter out the antibodies. Sean Gallup—Getty Images  Ultraviolet light reveals the clusters of cells that are busy making antibodies. One kg of leaves produces about 5g of antibodies, which is about a third of the dose required to treat an Ebola patient. 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