In 2019, U.S. health officials became very concerned about a mysterious illness related to vaping.

Vaping is the act of breathing in vapor through the mouth. It uses a battery-operated electronic device to heat liquid and mix small particles with air.

An illness tied to vaping can make a teenager's lungs look like those of an old person.

The Centers for Disease Control and Prevention, or CDC reports, as of December 17, that more than 2,500 people had been hospitalized for injuries connected to vaping.

People in 27 American states have died from the illness. The CDC says additional deaths are under investigation. More than 50 deaths have been blamed on vaping. However, new numbers are expected to be released Tuesday.

Link to marijuana products

Vaping is popular among people who want to avoid smoking tobacco cigarettes. It also has become a way for people to inhale marijuana to get high.

Most of the illnesses have occurred in people who vaped THC, the substance in marijuana that produces a high.

In November, American officials reported the discovery of Vitamin E acetate in lung tissue from 29 patients. The substance is believed to be used in illegal vaping products containing marijuana.

The CDC called Vitamin E acetate a "chemical of concern." It recommended that the substance not be added to e-cigarette or vaping products while the investigation is ongoing.

Chemicals are added to e-cigarettes and other products to provide different tastes. They are then inhaled while vaping. Even when the e-liquids do not contain nicotine, the lungs still take in other chemicals. While many of the flavorings are considered safe in foods, earlier research has suggested that inhaling vapor from these chemicals may damage the lungs, blood vessels and heart.

More U.S. teens vaping marijuana in 2019

More than 20 percent of U.S. high school seniors said they vaped THC in 2019, researchers reported in December. The researchers also found that seven percent of students as young as 13 reported vaping THC in the last year.

Richard Miech of the University of Michigan led the study. The findings appeared in the medical publication JAMA. "Whatever teens can vape has increased dramatically in the last few years," he told Reuters.

More harmful effects of e-cigarettes

New information about the harmful effects of e-cigarettes also was released last month. That study showed the use of e-cigarettes increases the risk of developing chronic lung diseases, but less so than smoking regular tobacco cigarettes.

The study was published in the American Journal of Preventive Medicine. It looked at 32,000 American adults between 2013 and 2016 who had no signs of lung disease when the study began.

Scientists found that those who used e-cigarettes were 1.3 times more likely to develop chronic lung diseases such as asthma, bronchitis, emphysema, and chronic obstructive pulmonary disease.

For people who used both e-cigarettes and traditional cigarettes, the risk was nearly three times higher.

Last month, the World Health Organization called for additional rules on the marketing and sales of e-cigarettes, as more information about the possible effects of these products becomes known.

Health officials are increasingly worried about reports of deaths and illnesses linked to vaping. They see the recent death of a young man in Belgium and reports of vaping-related illnesses in the Philippines as a reason to take stronger action.

I'm Jill Robbins.

Anne Ball wrote this story, with information from Reuters and the Associated Press and VOA News. Ashley Thompson was the editor.

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vapor – n. a substance that is in the form of a gas or that consists of very small drops or particles mixed with the air

teenager – n. someone who is between 13 and 19 years old

inhale – v. to breathe in

marijuana – n. the dried leaves and flowers of the hemp plant that are smoked as a drug

flavoring – n. a substance that is added to a food or drink to give it a desired taste

dramatically – adj. sudden and extreme

chronic – adj. continuing or occurring again and again for a long time