Videos promoting the use of e-cigarettes and other tobacco products are widespread on YouTube, a new study finds.

Viewership of these videos soared from 2013 to 2019, researchers at the University of Pennsylvania found. Tutorials for vaping products are especially popular. In 2019, the most-viewed pro-tobacco video was on “the art of the vape,” which had logged more than 40 million total views, or more than 68,000 per day.

Other popular videos claim the risks of tobacco use can be managed in various ways, without offering scientific evidence.

“Although we have no direct evidence of the effect of pro-vaping videos, the rise of vaping among adolescents in the last few years has been accompanied by dramatic increases in viewership of vaping videos,” lead author Dan Romer said in a news release.