Contrary to popular belief, hookah smoke is not chemically safer than cigarette smoke, according to a recent study at UC Irvine that analyzed hookah smoke emissions and found that one drag from a water pipe could contain as many harmful substances as smoke from an entire cigarette.

The first of a two-part study funded by the National Institutes of Health was published in late June. It focuses on identifying the specific chemical components of hookah smoke.

Hookahs are water pipes typically used to smoke specially made flavored tobacco.

Beginning in 2017, a team of UCI scientists used a custom-built apparatus to test regular tobacco and a nicotine-free herbal mixture.

Following analysis of emissions produced by both in a typical water pipe session, researchers found what they described as a surprisingly large amount of ultra-fine particles in the hookah smoke, which can pose significant health risks.

Ultra-fine particles are particulate matter measuring less than 100 nanometers in diameter. A nanometer is one-billionth of a meter.

By comparison, a single strand of hair is about 100 microns; 100 nanometers is about 1,000 times smaller than that, according to Veronique Perraud, the lead author of the study and an associate project scientist at the UCI department of chemistry.

When they are inhaled, ultra-fine particles aren’t stopped in the upper part — the nose — of the human respiratory system, Perraud said. The particles could instead deposit themselves deeper in the respiratory tract, and the smallest of them are able to make it into the bloodstream to be delivered to different parts of the body.

The team also found large amounts of carbon monoxide and organic molecules, such as acetaldehyde, acrolein or benzene — a known human carcinogen, according to the American Cancer Society.

The federal Centers for Disease Control and Prevention says hookah smoke’s popularity has grown in recent years among high schoolers and college students and that many users believe it is a less harmful alternative to cigarette smoke.

“There’s a perception that, No. 1, a nicotine-free tobacco is good for you. It’s incorrect — even if you have a nicotine-free product, you still have a whole lot of different chemicals coming out, including some that are toxic,” said study co-author Sergey Nizkorodov, a chemistry professor at UCI. “No. 2, there’s also a perception that if you have water in the water pipe, it’ll clean out the smoke to remove the toxins from it. We and other [researchers] don’t see evidence for this.

“Most of the chemicals pass right through the water, and the number of ultra-fine particles is actually enhanced by water.”

But this study is not technically indicative of whether the smoke from a water pipe is more dangerous than that of a cigarette, Nizkorodov said.

The complexity of hookah smoke may be comparable to that of cigarette smoke, he said, but that doesn’t indicate that hookah smoke is worse than cigarette smoke. To determine that, researchers need to study the health effects that hookah smoke can cause.

The second part of the study, which focuses on the specific health effects of water pipe smoking, is underway at the UC Irvine School of Medicine.

“We’re just saying that if you look at this from a chemical point of view, [hookah smoke] contains a lot of carbon monoxide and particulate matter and someone should really examine the health effects of this more carefully,” Nizkorodov said. “We are trying to do this ourselves, but we want to encourage others to do this as well.”