In this photo illustration, ZYN nicotine cases and pouches are seen on a table, Jan. 29, 2024, in New York. (Michael M. Santiago/Getty Images)

(NEW YORK) -- A type of nicotine pouches designed for adults is facing scrutiny on Capitol Hill, while also exploding in popularity online and among young people.

The pouches, sold under the brand name ZYN, have long been popular in Europe, but are now taking hold in the United States with the help of so-called "Zynfluencers" on social media.

The hashtag #ZYN has amassed more than 700 million views on TikTok alone. With their popularity on social media, the pouches have gained the attention of Gen-Z, some of whom are under the age of 18.

Here are three things to know about the pouches, and the controversy:

1. ZYN is marketed as a tobacco-free alternative to smoking

ZYN is manufactured by Swedish Match, a Stockholm-based company. The parent company of Swedish Match is Philip Morris International, which is headquartered in Connecticut.

The product is a small pouch that you place between your upper lip and gum for "up to one hour," according to the company's website.

The pouches come in flavors ranging from cinnamon and citrus to coffee and peppermint.

Swedish Match describes ZYN as an "alternative to smoking or dipping," noting on its website, "For those consumers concerned about the health effects of smoking or dipping, the best thing to do is quit."

ZYN pouches contain nicotine, the addictive product used in cigarettes, cigars and most e-cigarettes.

The health risks of using nicotine include everything from increased blood pressure to increased heart rate, increased heart attack risk and a narrowing of the arteries, research shows.

According to Swedish Match, ZYN pouches are required by the U.S. Food and Drug Administration to come with a warning that notes the product contains nicotine and that nicotine is "an addictive chemical."

2. Medical experts say it's too early to know the impact of nicotine pouches on kids

While ZYN pouches contain a smaller amount of nicotine compared to traditional cigarettes, medical experts say nicotine-containing products are a health risk for young people under the age of 18, in particular.

Consuming nicotine in high amounts can put young people at risk of acute nicotine toxicity, which can cause agitation, a fast heart rate and vomiting, according to the U.S. Centers for Disease Control and Prevention.

Prolonged nicotine use can also increase the risk of cardiovascular and respiratory disorders.

Nicotine exposure can hinder brain development in adolescents and young adults, which can continue into the mid-20s, the CDC says.

"If you take kids that are in their teenage years, and you make them lifelong users, four or five decades later, I don't know what the health consequences would be," Dr. Panagis Galiatsatos, a pulmonary and critical care medicine physician and spokesperson for the American Lung Association, told ABC News' Good Morning America.

Philip Morris International told GMA in a statement that the company is "focused on" preventing young people under the age of 21 from using its products.

"ZYN is designed for adults aged 21 or older who are currently using nicotine products and wish to continue using nicotine," the company said in a statement. "Our marketing practices -- which prohibit the use of social media influencers -- are focused on preventing underage access and set the benchmark for the industry.”

3. Legislators are calling for a crackdown

Amid the rise in ZYN's popularity, Senate Majority Leader Chuck Schumer called for federal action to regulate nicotine when it comes to marketing the product to kids.

Last week, Schumer, a Democrat from New York, urged the FDA to investigate ZYN over its marketing practices.

"A simple search of social media for ZYN will generate an eye-popping amount of content," Schumer said at a Jan. 21, press conference. "Most of you probably haven't heard of it, but your kids probably have."

"It's a pouch packed with problems -- high levels of nicotine," said Schumer, who previously led the charge against vapes and e-cigarettes being marketed to children. "So today, 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 'em."

According to the CDC, around 1 in every 100 high school students last year reported using nicotine pouches in the past 30 days.

If you or someone you know is struggling with nicotine addiction or other substance abuse or mental health concern, free and confidential help is available 24 hours a day, 7 days a week. Call the National Substance Abuse and Mental Health Services Administration (SAMHSA) helpline at 1-800-662-HELP (4357).

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