“It’s a pouch packed with problems—high levels of nicotine,” Schumer said on Sunday. “I’m delivering a warning to parents, because these nicotine pouches seem to lock their sights on young kids—teenagers, and even lower—and then use the social media to hook them.”

Schumer, who has previously fought for tobacco regulations and e-cigarette bans in schools, said that “ZYN is the next battle.”

Nicotine pouches, which do not contain tobacco but are slipped under a user’s lip like snus, have grown wildly popular. Over 800 million units were sold between January and March 2022, compared to 126.06 million units between August to December 2019 and beating out its competitors. ZYN shipped 105.4 million cans in the U.S. in their 2023 Q3, a 65.7% increase from Swedish Match’s 63.6 million can shipments in the same period in 2022. Philip Morris International, which owns ZYN’s parent company Swedish Match, noted the “exceptional growth“of ZYN in its last earnings, although the company has clarified to Fortune that this unit is not yet folded into its reporting, so did not contribute to its $9 billion in quarterly net revenue.

On social media, young people and so-called “Zynfluencers” are spreading the nicotine buzz, withTikToks using #zyn receiving over 715.6 million views to date. 

A 2022 National Institute of Health study found that users talking about nicotine on the app espouse both the harms and benefits of products. Of the 149 videos using #nicotineaddiction analyzed in the study, 28% mentioned psychological or physical benefits of nicotine, such as feeling a buzz, and 28% mentioned a social benefit, such as connecting with other users. Almost half of the analyzed videos mentioned nicotine withdrawal symptoms, and content creators under 21 mentioned quitting less frequently than creators over 21.

A PMI spokesperson told Fortune that the company does not work with influencers on marketing materials, and that ZYN only uploads age-gated Instagram and Facebook posts to users over 21.

“Our marketing practices—which prohibit the use of social media influencers—are focused on preventing underage access and set the benchmark for the industry,” PMI wrote in a statement.

Big tobacco turns anti-cigarette

PMI’s acquisition of Swedish Match in 2022 was part of the company’s plan to promote smoke-free products, with the goal to have two-thirds of its revenue come from smoke-free products by 2030.

Cigarette smoking reached a new low in 2021, with over three-quarters of Americans surveyed in a 2022 Gallup poll calling the practice “very harmful.” British American Tobacco Plc wrote down some of its U.S. cigarette brands by $31.5 million last month, its biggest decline in shares in four years.

Tobacco companies are pivoting from the weakening popularity and health risks of cigarettes to try to make up share with other nicotine-containing products. PMI and Marlboro-maker Altria, which in 2019 acquired Helix Innovations, producer of On! nicotine pouches, describe their smoke-free options as part of a “harm reduction” framework. The pouches, as well as other smoke-free products, are intended for cigarette smokers looking to cut down on combustible products.

PMI told Fortune that “the vast majority of harm from tobacco use comes from smoke breathed into the lungs—ZYN does not produce smoke.” However, dentists have reported that nicotine pouch users have noticeable gum damage. The CDC reported that nicotine can harm brain development, which extends into a person’s 20s.

Nicotine pouch use is low compared to e-cigarette use among Gen Z, with 1.5% of middle- and high-schoolers reporting current nicotine pouch use, with an estimated 400,000 young users in the U.S. That’s compared to 7.7% of the cohort, or an estimated 2.1 million people, reporting using e-cigarettes, according to the 2023 National Youth Tobacco Survey.

Dr. Panagis Galiatsatos, a pulmonary and critical care medicine physician and director of the Tobacco Treatment Clinic at Johns Hopkins School of Medicine, told Fortune that young people’s use of nicotine pouches differs from that of adult smokers.

ZYN can represent a harm reduction option for adult smokers, he said, but for young people, nicotine pouches can be an introduction to a decades-long addition to nicotine.

“Being introduced to nicotine in its most addicting form is much more vulnerable in the young because that part of the brain still gets developed—the prefrontal cortex,” Galiatsatos said in an interview. “Having them exposed to these products will mean they may be decades-old users of these products. Suddenly that cumulative risk may catch up to them.”

Update, Jan. 26, 2024: This story has been updated to note that Philip Morris International has not yet folded Swedish Match group into its GAAP earnings report.