E-cigarettes were introduced in the U.S. in the late 2000s and rapidly transformed the landscape of smoking. Combustible cigarettes, laden with the acrid smell of burning ash and burdened by their legacy of death and disease, fell out of favor with America’s younger generations. The new e-cigarettes were cleaner and safer — right?

Well, about that last part. The recent outbreak of vaping-related illnesses continues to permeate the U.S. with no signs of slowing. The Centers for Disease Control and Prevention are actively investigating over 1,000 cases, and the agency’s most recent death count stands at 18. The cigarette fallout of the 1950s and 1960s imparted a history lesson  — but much of the vaping public seems to have missed it.

Traditional tobacco, too, was once perceived as relatively innocuous. Marketers promoted the products as safe, and medical professionals didn’t immediately mobilize to counter those claims — until the U.S. Surgeon General released a report in 1964 that confirmed the role of cigarettes in causing lung cancer. In contrast, health experts were never fully on board with the safety of e-cigarettes.

“I think the public-health community’s radar screen is very heightened around any tobacco product, and so there’s no way a new product could be released without receiving great scrutiny,” said Anthony Alberg, chair of Epidemiology at UofSC’s Arnold School of Public Health.

Alberg said that, while e-cigarettes are likely safer than combustible cigarettes, they still aren’t safe. Like the outbreak of lung cancer cases that surfaced after decades of widespread combustible cigarette use in society, it will take time to see the long-term effects of e-cigarettes — and some effects will likely bear some similarities to those of traditional cigarettes.

“There are cancer-causing metals that have been documented in the vape and in the blood of e-cigarette smokers, so that gives very strong evidence to believe that they would be a cause of cancer,” Alberg said.

In addition to the carcinogenic metals released by the coil in e-cigarettes, many flavorants and additives could contribute to future illnesses. Additives like diacetyl, a common additive in butter, oils and other baking products, are approved by the Food and Drug Administration as safe. However, Alberg stressed that the FDA only cleared those additives for ingestion — not for inhalation.

Though the recent vaping-related illnesses demonstrate that e-cigarettes aren’t harmless, they still could entail major public-health benefits. There is some evidence that e-cigarettes are effective in helping people quit smoking traditional cigarettes. Given the potential benefit of these products, some experts disagree with the recent proposals by some states to ban e-cigarettes.

“I think it would be a big policy mistake to, in a sense, do away with something that is really helping a lot of people give up the real problem of inhaling smoke,” said Erik Collins, professor emeritus at UofSC’s School of Journalism and Mass Communications, and a former corporate communications adviser for Philip-Morris Incorporated.

Combustible tobacco smoking kills roughly 480,000 people per year, according to the CDC, compared to the relatively minute 18 killed by e-cigarettes thus far. Since e-cigarettes are so effective in breaking the hold of traditional cigarettes, the devices could carry a net-positive effect for public health.

Alberg warns, however, that it’s a two-way street. While e-cigarettes may help some addicted smokers break the habit, e-cigarettes also may lead a new generation back to old dangers.

“There’s strong evidence that youth who vape are much more likely to go on to smoke combustible tobacco cigarettes,” Alberg said. “And for me, as a public-health professional and one who knows the full consequences of combustible tobacco cigarettes, that’s one of the worst outcomes we can imagine — and therefore a strong reason to be concerned about the epidemic of vaping in youth.”

As the Trump administration’s plan to remove flavored e-cigarettes from the marketplace develops, states are left with a choice. Act now to curb a growing health crisis, or wait — and hope that the new-look e-cigarettes truly mitigate the devastation of the old cigarettes.

E-cigarettes may help addicted smokers quit, but experts fear they may also lead a younger generation to traditional cigarettes.

Decades of widespread cigarette use passed before the Surgeon General reported that smoking is harmful. The long-term effects of vaping remain unknown.