The attacks on e-cigarettes are gathering pace with the American Lung Association's annual State of Tobacco Control report adding to the chorus of voices ranged against the products.

The ALA's report assigns each state a letter grade based on how well lawmakers are restricting tobacco use and promoting smoking cessation.

But the report also criticizes states where e-cigarettes are exempted from proposals to raise the minimum age of sale for tobacco to 21.

For a charity that purports to save lives by reducing lung disease, the call for a minimum vaping age of 21 is puzzling. E-cigarettes contain no tobacco whatsoever, so it is somewhat bewildering for these products to be contained in a tobacco control report in the first place.

E-cigarettes also represent a fraction of the risk of regular combustible cigarettes. According to the United Kingdom's Royal College of Physicians, e-cigarettes are unlikely to exceed 5 percent of the risk of regular cigarettes.

There is also a large and growing body of evidence suggesting e-cigarettes are helping smokers quit for good. Rising e-cigarette prevalence has not interrupted the rapid decline in teen smoking rates, with some experts suggesting the products may have contributed to this decline.

So why are these products targeted by the ALA's report for a minimum age of sale of 21? Based on the evidence it would appear foolish to deprive adult smokers under 21 the chance to switch to a reduced risk product.

The most probable reason is that the majority of e-cigarettes contain nicotine and vaping mimics the experience of smoking. Most public health bodies are wary of smoking cessation methods that don't have the government's stamp of approval. For many in the world of public health, nicotine abstinence is more highly prized than harm reduction.

The problem with this approach is that many smokers find it extremely difficult to quit and the officially approved nicotine replacement therapies have dismal rates of success.

While it is widely accepted that an abstinence-only approach is not the best way to go in other major public health areas such as drug use or sexual health, when it comes to nicotine and vaping, public health groups appear to have a blindspot.

Proposals to raise the vaping age to 21 not only deprive adult smokers of a safer legal alternative to tobacco, but there is evidence to suggest these age restrictions may produce the opposite effect of what they intend.

A study published in Preventative Medicine in 2016 found there was an 11.7 percent increase in teen cigarette use after states introduced new age restrictions for e-cigarettes between 2007 and 2013.

"We should regulate tobacco products proportionate to their risks, and e-cigarette evidence suggests they're less risky products," said the study's lead author Dr. Michael F. Pesko. "While there's some risk, it would be a mistake to regulate them the same way we regulate cigarettes."

A similar effect was observed in a study published in 2015 from the Yale School of Public Health showing smoking rates among 12 to 17-year-olds rose in states that banned e-cigarette sales to minors.

Pesko's latest study on the effect of age restrictions on e-cigarette purchases published Wednesday shows they had an even larger impact on cigarette use by pregnant teens, increasing by 2.1 percentage points.

All three of these studies looked at the impact of raising the age of e-cigarette purchases to 18, which is now the minimum age nationwide thanks to Food and Drug Administration regulation and supported by the industry.

Raising the purchase age of e-cigarettes purchase to 21 could undermine the very goals the ALA says it is pursuing by making it increasingly unattractive for younger smokers to switch to a safer product.

"With the release of this report, the ALA is again showing itself to be an organization guided by politics and ideology, not public health science," says Gregory Conley, president of the American Vaping Association.

"While respected medical bodies in the United Kingdom and Canada are taking proactive steps to truthfully inform adult smokers that vaping can save lives, groups like the ALA are continuing to push prohibition and excessive taxation," Conley added.

Guy Bentley (@gbentley1) is a contributor to the Washington Examiner's Beltway Confidential blog. He is a consumer freedom research associate at the Reason Foundation and was previously a reporter for the Daily Caller. Thinking of submitting an op-ed to the Washington Examiner? Be sure to read our guidelines on submissions.