A woman smokes an e-cigarette. (Paul J. Richards/AFP/Getty Images)

Tom Miller, a Democrat, is attorney general of Iowa.

Twenty years ago this month, I joined 45 other state attorneys general to enter into the landmark settlement with the tobacco industry. Since then, the U.S. cigarette smoking rate fell from 24 percent of adults to 14 percent last year — the lowest ever.

We have the opportunity to go much lower. But we’re also at risk of reversing these gains if we fail to give smokers safe alternatives to cigarettes.

E-cigarettes are prompting a great deal of discussion and debate, especially regarding their use by children. On Thursday, the Food and Drug Administration unveiled new restrictions on the sale of e-cigarettes and on vaping flavors in an attempt to curb teenage use of the products. But it is important to put this discussion into the context of harm reduction — similar to how we think about safe sex and clean needles.

Public Health England, which has been a bellwether on these issues, found e-cigarettes to be at least 95 percent less harmful than combustibles. This rather dramatic result occurs because e-cigarettes do not produce the carbon monoxide and hundreds of other deadly chemicals found in cigarette smoke.

Thirty-four million American adults smoke, and 17 million will die from smoking-related diseases. If all American smokers switched to e-cigarettes, we could extend the lives of up to 6.6 million people . Some have switched. In the past three years, the adult smoking rate dropped 17 percent, a rate rarely, if ever, seen. Tax increases, smoke-free statutes, public ad campaigns, advertising restrictions and cessation programs have contributed to consistently falling smoking rates. But the most plausible explanation for the recent accelerated decline is the common use of e-cigarettes. England, which pursued harm reduction through e-cigarettes sooner than the United States did, has seen its adult smoking rate drop 23 percent in five years. In Japan, heat-not-burn products, another alternative to combustible cigarettes, have helped reduce the sales of cigarettes by 27 percent in two years, according to Japan Tobacco.

 I have outlined a plan for the country whereby the adult smoking rate goes to less 10 percent by 2021 with the distinct possibility of it going to under 5 percent by 2024. (The plan is heavily premised on the availability of e-cigarettes and heat-not-burn products, and on the FDA reducing the amount of nicotine in combustibles.) This could save millions of lives.

This great benefit must be balanced against the harm to children. Kids’ use of e-cigarettes has spiked recently, with approximately 21 percent of high-schoolers using e-cigarettes at least once in the previous 30 days. There are two important points to put this in context: First, this once-in-30-days use is overwhelmingly experimental or dual use. A new study in the journal Tobacco Control shows that approximately 75 percent of 15- to 17-year-olds using JUUL e-cigarettes use them fewer than 10 days a month. Daily use of e-cigarettes, assuming previous patterns, would be around 2 percent for all youths. If there is an epidemic, it is an epidemic of casual use. There is no real fear of addicting a generation — 2 percent does not make a generation.

As for disease concerns, they are limited because, again, e-cigarettes are far less harmful than combustibles. The main concern is addiction — a serious matter, but there is no credible evidence that teens who vape will switch to combustible cigarettes. Some have raised concerns about nicotine’s effects on brain development, as decades-old studies in animals have indicated harm. But there have been no studies in humans that show brain development is harmed by nicotine in any way.

We should take this epidemic of casual e-cigarette use among children seriously, but we should not overreact. To overreact and limit access to harm-reducing tools means that adults die. Of course, we should enact measures such as age verification and implement rules to prevent vape companies from marketing to youths in any meaningful way. The primary question, however, is how to regulate e-cigarette flavors, many of which appeal to both adults and kids. Any significant restriction of flavors should be justified by a strictly science-based analysis of the harms and benefits. That would be difficult to justify, because the potential harm to adults would be the ultimate public health harm — death — and the harm of casual use of e-cigarettes is either very small or nonexistent.

The FDA should be the last institution to slow or stop the harm-reduction potential of these products. The FDA should never act in a way to cause tens of thousands of Americans, perhaps hundreds of thousands, to die.