In recent weeks, a crisis has erupted over vaping.
States have issued dire warnings, banned flavored e-cigarettes and tried, along with the federal government, to get to the bottom of what was causing hundreds of mysterious lung illnesses as well as several deaths around the country.
However, the recent warnings are not the first, with statements dating back a decade from major government entities and for years in scientific journals.
E-cigarettes and vaping started gaining popularity first in 2007 and have become more and more common since. With that, the number of official warnings has picked up steadily over time.
Here are some of them:
June 22, 2009: The Tobacco Control Act goes into effect
Then-President Barack Obama signed the Tobacco Control Act into law, which gave the Food and Drug Administration (FDA) the authority to regulate the creation and marketing of tobacco products, but doesn’t specifically list or mention e-cigarettes.
July 22, 2009: FDA warns about e-cigarettes
A news release from the U.S. Food and Drug Administration pointed to a laboratory analysis of e-cigarette samples that found “they contain carcinogens and toxic chemicals such as diethylene glycol, an ingredient used in antifreeze.”
“The FDA is concerned about the safety of these products and how they are marketed to the public,” Margaret A. Hamburg, M.D., commissioner of food and drugs, said in the news release.
The release went on to note that the products had not been evaluated or approved by the FDA so “at this time the agency has no way of knowing, except for the limited testing it has performed, the levels of nicotine or the amounts or kinds of other chemicals that the various brands of these products deliver to the user.”
Sept. 24, 2013: National Association of Attorneys General wants regulation
A letter signed by 40 state and territorial attorneys general called for the FDA to test and regulate e-cigarettes, noting how at that time there was so little known about them.
“Through television advertising, consumers are led to believe that e-cigarettes are a safe alternative to cigarettes, despite the fact that they are addictive, and there is no regulatory oversight ensuring the safety of e-cigarette ingredients,” the National Association of Attorneys General news release stated.
The group noted that unlike cigarettes, there were no age restrictions on e-cigarettes and they had flavors that appeal to younger users.
Dec. 15, 2015: Study questions whether chronic e-cigarette use could cause lung disease
In a study in the American Journal of Physiology, researchers asked if e-cigarette smoke could have similar effects as cigarette smoke in chronic users. While they acknowledged that more study was needed, they concluded that the vapor contains toxic substances, although less so than cigarette smoke.
And they did say that it elicited a biological response in mice in the in the "vast majority" of studies.
2016: Surgeon General releases report about e-cigarette use among youth
The report warns about the significant uptick in popularity among young people in spite of the fact that “gaps in scientific evidence do exist.”
“E-cigarette use among U.S. youth and young adults is now a major public health concern. E-cigarette use has increased considerably in recent years, growing an astounding 900% among high school students from 2011 to 2015,” then-Surgeon General Vivek Muthy’s preface states.
Specifically, the surgeon general warned about nicotine and its effects on the developing brain. "The effects include addiction, priming for use of other addictive substances, reduced impulse control, deficits in attention and cognition, and mood disorders," the report said. There were also warnings for pregnant women and the dangers of ingestion.
But there was also much that was not known. "The health effects and potentially harmful doses of heated and aerosolized constituents of e-cigarette liquids—including solvents, flavorants, and toxicants—are not completely understood. However, although e-cigarettes generally emit fewer toxicants than combustible tobacco products, we know that aerosol from e-cigarettes is not harmless," the report said.
May 5, 2016: FDA issues new e-cigarette regulations
The FDA bolstered its regulations of e-cigarettes, adding requirements that affect manufacturing, ingredient labeling and not selling the product to those under the age of 18.
"We have more to do to help protect Americans from the dangers of tobacco and nicotine, especially our youth. As cigarette smoking among those under 18 has fallen, the use of other nicotine products, including e-cigarettes, has taken a drastic leap. All of this is creating a new generation of Americans who are at risk of addiction," then-Health and Human Services Secretary Sylvia Burwell said in a statement.
"Today’s announcement is an important step in the fight for a tobacco-free generation -- it will help us catch up with changes in the marketplace, put into place rules that protect our kids and give adults information they need to make informed decisions," Burwell said.
July 7, 2016: American Lung Association warns of 'popcorn lung'
The American Lung Association warned that a chemical found in artificially buttered popcorn, diacetyl -- which caused "deaths and hundreds of cases of bronchiolitis obliterans, a serious and irreversible lung disease" -- was found in "many" e-cigarette flavors. "It is added to "e-juice" liquid by some e-cigarette companies to complement flavorings such as vanilla, maple, coconut and more," the statement said.
"So while diacetyl was swiftly removed from popcorn products since it could cause this devastating disease among factory workers, e-cigarette users are now directly inhaling this harmful chemical into their lungs," the statement said.
Citing a study from Harvard, the ALA said diacetyl was found in 39 of 51 e-cigarette brands it tested and other harmful chemicals -- 2,3 pentanedione and acetoin -- were found as well.
Aug. 8, 2016: FDA gets authority over e-cigarettes
The FDA’s “deeming rule” went into effect for electronic nicotine delivery systems (ENDS), which meant that the Center for Tobacco Products gained regulatory authority over e-cigarettes, vapes and other products.
“Since late 2016, FDA has worked at maximal speed to regulate this rapidly evolving class of new tobacco products, but our policies and procedures in this area are still evolving,” an FDA overview of their oversight states.
On that date, it became illegal to sell e-cigarettes and other ENDS to people under 18 years old, the FDA stated.
March 5, 2018: Report notes presence of toxic chemicals
A report in the medical journal Pediatrics showed vaping could lead to the presence of concerning levels of toxic chemicals in the bodies of those who smoked as well as vaped or those who just vaped alone.
Almost 100 teens from the San Francisco Bay area were examined in the University of California-San Francisco study: 67 teens used e-cigarettes only, 16 used both e-cigarettes and conventional cigarettes and 20 didn't smoke or vape at all.
Urine and salivary gland testing looked for breakdown products of toxic chemicals that have been associated with cancer -- and found them in both smokers and vapers -- but not those who didn’t smoke at all.
June 8, 2018: CDC report notes popularity decrease after massive uptick
In the CDC’s Morbidity and Mortality Weekly Report (MMWR), it stated that at this time, e-cigarettes were the most commonly used tobacco product among middle school and high school students.
E-cigarettes had experienced a massive increase in use starting in 2011, but decreased after 2015.
Aug. 13, 2018: Journal suggests that vaping may increase toxic effects of e-liquid
A study in the journal Thorax indicated a "significant increase in cytotoxicity [on certain lung immune cells] caused by the vaping process itself."
The authors noted that exposures of the cells to the vapor during the in vitro experiment "induced many of the same cellular and functional changes...seen in cigarette smokers and patients with COPD."
"While further research is needed to fully understand the effects of e-cigarette exposure in humans in vivo, we suggest continued caution against the widely held opinion that e-cigarettes are safe," the authors said.
Sept. 11, 2018: Retailers warned and manufacturers highlighted
The FDA went so far as to call e-cigarettes an “epidemic” among children and issued warning letters to retailers over unlawfully selling to minors.
"We're seeing an acceleration in the use of the cigarettes to levels that simply aren't tolerable,” then-FDA commissioner Scott Gottlieb told ABC News.
“We have access to data that tells us that the growth in youth use of the cigarettes has reached what I'm calling epidemic proportions and we need to step in and take action to try to stem that use to try to bring the rates of use among young people down, particularly high school students,” he said at the time.
Sept. 18, 2018: FDA launches e-cigarette prevention campaign
“E-cigarettes have become an almost ubiquitous – and dangerous – trend among youth that we believe has reached epidemic proportions,” said Gottlieb.
“This troubling reality is prompting us to take even more forceful actions to stem this dangerous trend, including revisiting our compliance policy that extended the compliance dates for manufacturers of certain e-cigarettes, including flavored e-cigarettes, to submit applications for premarket authorization,” Gottlieb said in a statement.
Dec. 18, 2018: Surgeon General issues advisory, calls e-cigarette surge “cause for great concern”
The U.S. surgeon general issued a strong warning against e-cigarette use by young people, called it "unsafe" in any form and termed vaping an "epidemic."
"Two years after my predecessor sounded the alarm bells, youth e-cigarette use has skyrocketed -- so much so today that I am officially declaring e-cigarette use among youth an epidemic in the United States," said U.S. Surgeon General Jerome Adams, known as the "nation's doctor," at a news conference.
An associated CDC report noted that after leveling off a bit in 2016 and 2017, e-cigarette use skyrocketed again in 2018. The report cited the effects of nicotine exposure as well as the dangers of flavored products being marketed to youth.
"And I don't want there to be any misconceptions about this. I don't use that word, epidemic, which means a sudden increase about normally expected numbers, I do not use that word lightly," Adams said.
Aug. 14, 2019: Minneapolis officials call for investigation
The Minnesota Department of Health (MDH) asked health care providers to be on alert for lung diseases related to vaping and e-cigarette use among young adults after a Minnesota hospital reported several “severe” cases.
Children’s Minnesota hospital has reported four cases of “severe lung injury” in the Minneapolis area that it says are similar to cases recently reported in Wisconsin and Illinois. The hospital also said it is “too early to say whether they are connected.”
The patients spent several weeks in the hospital and some were admitted to the intensive care unit for symptoms including shortness of breath, fever, cough, vomiting and diarrhea. Other symptoms reported by some patients included headache, dizziness and chest pain.
Aug. 18, 2019: Federal investigations launched
Federal health officials are investigating potential links between lung illnesses and e-cigarettes.
Since June 28, there have been at least 94 cases reported across several states involving people with "severe pulmonary disease" possibly tied to vaping, with the majority of those affected being teenagers and young adults, according to the U.S. Centers for Disease Control and Prevention.
At least 30 of those cases were reported in Wisconsin, the CDC said in a statement.
Aug. 23, 2019: First possible vaping death reported
An investigation was launched in Illinois into more than 30 cases where individuals experienced respiratory illness after using e-cigarettes or vaping, state officials said.
One such case involved an individual who allegedly recently vaped before being hospitalized with severe respiratory illness. That individual, whose name, gender and age were not publicly released, died, according to Illinois Department of Public Health.
"The severity of illness people are experiencing is alarming and we must get the word out that using e-cigarettes and vaping can be dangerous," IDPH Director Dr. Ngozi Ezike said in the news release.
The type of e-cigarettes used by these individuals were not disclosed.
Sept. 9, 2019: Melania Trump speaks out against e-cigarettes, and movement in New York
First Lady Melania Trump tweeted about vaping, saying she is "deeply concerned about the growing epidemic."
That same day, New York Gov. Andrew Cuomo announced that he wants to ban flavored e-cigarettes amid growing national health concerns about vaping.
The New York Department of Health is also launching an investigation into companies producing vaping substances and will require shops that sell e-cigarettes to post a warning to "let people know this is a risky endeavor," he said.
"This is a frightening public health phenomenon," Cuomo said at a news conference.
As part of the investigation, Cuomo said subpoenas will be issued to learn more about the chemical makeup of vaping products.
He added that "common sense" would suggest that "if you don’t know what you are smoking, don’t smoke it, and right now we don’t know."
Sept. 11: 2019: President Trump calls for ban on flavored e-cigarettes
"We are looking at vaping strongly, it's very dangerous, children have died and people have died," Trump told reporters in the Oval Office. "We're going to have some very strong rules and regulations."
The president said kids are coming home from school and saying, "Mom, I want to vape."
Sept. 19, 2019: Warning not to buy products from the street
The FDA, working with their criminal investigation unit, says it has collected 150 samples from several states to analyze and is testing for "chemicals, nicotine, THC, opioids, cutting agents, additives, poisons, toxins, pesticides."
The investigators say they did not plan to pursue prosecutions immediately, just that they’re trying to trace the supply chain for the problem vaping products.
It’s crucial, they say, that vapers who use those products aren’t afraid of prosecution, or they won’t report information that could help the search.
Those who use vaping products were warned not to add anything to the vape cartridge and not to buy products from the street.
ABC News’ Stephanie Ebbs, Anne Flaherty, Quinn Owen, Karma Allen, Allie Yang and Meridith McGraw contributed to this report.