“I am not aware of any other scientist in the world who has more publications than me concerning e-cigarettes,” he said.

Farsalinos travels the global scientific-conference circuit talking up the public-health benefits of vaping. He has a website at ecigarette-research.org, where he rails against studies and media reports casting vaping in a bad light.

In a recent blog post, Farsalinos called the U.S. reaction to the lung-injury outbreak “emotional and irrational hysteria.” In another, he complained of a “witch hunt against e-cigarettes” and criticized a Bloomberg article on early signs of vaping-related lung injuries as “a collection of confusing and irrelevant information.”

“There is no doubt that e-cigarettes are far less harmful than smoking, absolutely no doubt,” Farsalinos said in a phone interview. The concerns over e-cigarettes are exaggerated, he said, and “for a smoker who has failed to quit by other methods, they can be literally life-saving.” He recommends vaping only for people who can’t quit through other cessation tactics.

Scientists in many fields have seen their research attacked by critics who use invective to seed doubt and drown out adverse findings.

Studies on the dangers of tobacco and climate change have been challenged by groups backed by companies whose profits could be endangered by lawsuits or regulation. Similar campaigns have targeted the science on pesticides and vaccines. Now, vaping advocates — some backed by groups with industry ties — are trying to undermine research questioning the safety of e-cigarettes.

On one side are researchers who say they’ve found troubling, if preliminary, evidence from laboratory studies that vaping may pose potentially serious health risks.

Opposing them are those who view e-cigarettes as a historic opportunity to spare smokers from disease and death, and who lash out against research they find flawed, biased or unreliable. Some of the pro-vaping researchers have received funds from e-cigarette or tobacco companies. Their criticisms are amplified by an army of pro-industry bloggers, trade groups and think tanks.

Among addiction researchers, it is a “religious divide now; you are either pro-vape or anti-vape,” said Wasim Maziak, an epidemiologist at Florida International University. “A lot of people have invested career and reputation in supporting vaping as the best thing that happened to us since whenever, and they are not backing down.”

“The pushback is really significant and really organized,” said Peyton. “No matter where you are, the same group of people are going to come after you and try to discredit your work.”