Does the water in a hookah filter the smoke? What was measured

Hookah myths & facts Part 2

“Hookah is milder than cigarettes, the smoke goes through water and gets cleaned.” You hear it in every lounge, and it's the number one hookah myth. Half of it is true: the smoke is milder. The false half is the part that makes people think it's harmless. Here's what the water in the base does, what it doesn't do, and what was measured when someone finally tested it on a machine.

What the water does and doesn't do

The smoke coming out of the bowl is hot. It goes down the stem, exits below the water surface in the base, bubbles up, and travels through a metre and a half of hose to you. Along the way it cools down and picks up moisture. That's why it doesn't scratch the throat like a cigarette, and why a beginner can inhale it at all. That is the whole job of the water: cooling and humidifying. A waterpipe is called a waterpipe because it has water in it, not because the water cleans anything.

How the smoke feels in your throat and what's in it are two different things. Cool smoke is more pleasant, but it carries the same nicotine, the same carbon monoxide from the charcoal, the same tar and metals from the tobacco. Thomas Eissenberg of Virginia Commonwealth University, who has studied hookah for twenty years, puts it in one sentence: the water doesn't filter the smoke, it cools it so it's very easy to inhale. The water does hold back some particles and some soluble compounds, that's true. Just not the ones you care about.

The Jordan measurement: 3 percent

The cleanest answer came from a group at the German Jordanian University and the Royal Scientific Society in Amman, published in 2015 in BMC Public Health. The question was simple: how much of the metal in the tobacco ends up in the water, how much in the ash, and how much in the smoke. They bought four tobaccos from the local market, domestic and imported from the Emirates, and smoked them on a smoking machine, not on people, so every puff was identical: 530 millilitres, 2.6 seconds, three puffs a minute. Twenty-two grams of tobacco per session, ten sessions per tobacco, charcoal cubes on foil like in any lounge. The water in the base, 750 millilitres, was not changed during all ten sessions.

Then they measured eleven metals in the tobacco before smoking, in the water after smoking and in the ash left in the bowl: chromium, copper, iron, lead, manganese, nickel, vanadium, uranium and a few more. The result: about 3 percent of the total metal stayed in the water, give or take one percent. By individual metal, from 0.2 percent for manganese to 4.4 percent for vanadium. About 40 percent stayed in the ash. The remainder, about 57 percent, was in neither the water nor the ash, so it could only have gone into the smoke. For uranium that's 95 percent, for manganese 48.

The authors' conclusion, without any softening: such a small fraction would not provide protection from the majority of potentially toxic metals. Water that hadn't been changed for ten sessions still retained only 3 percent. The full paper is publicly available, with tables for each metal.

Carbon monoxide and nicotine pass through

Metals are one part of the story. What actually gets you after a hookah is carbon monoxide, and it has nothing to do with the water. It's a gas that practically doesn't dissolve in water: a litre of water takes about 28 milligrams, and the smoke passes through the base as bubbles, in a fraction of a second. In the measurements on people we covered in part one of this series, after 45 minutes of hookah the blood held three to four times more carbon monoxide than after one cigarette. All of that gas had “gone through the water”.

Nicotine is more interesting, because it does dissolve in water. But the smoke passes through the base too fast for the water to catch it, and the blood shows it: peak nicotine after 45 minutes of hookah 10.2 nanograms per millilitre, after one cigarette 10.6. The same. If the water caught the nicotine, hookah wouldn't “work”, it wouldn't be addictive and people wouldn't order one after another. It works.

What it looks like in the lounge. After a session the water in the base turns yellow and smells of tobacco. That's the 3 percent plus some flavour and molasses. It looks like it “collected the dirt”, so people think the filter did its job. What passed through it you can't see, because it's already in you.

Why “smoother” is actually the problem

Smoother smoke isn't just more pleasant, it changes how you smoke. A cigarette scratches, so puffs are short and shallow: about 20 per cigarette, half a litre of smoke in total. Hookah doesn't scratch, so you inhale deeper and longer, while talking and looking at your phone: about 200 puffs in an hour and close to 90 litres of smoke through the lungs, according to the World Health Organization and the US CDC. Cooled smoke goes deeper into the lungs than hot smoke.

In other words, the water doesn't make hookah less harmful, it makes it easier to smoke. That's the difference worth remembering: smoother in the throat doesn't mean less in the lungs. It's also why the comparison with cigarettes comes out the way it does: by nicotine like one to a few cigarettes, by smoke and carbon monoxide far more.

Ice, milk, juice and alcohol in the base

Once you believe the water cleans, it's easy to believe something else cleans even better. There is no measurement showing that, for any of these:

• Ice and ice-cold water. The smoke gets even colder and even softer. Pleasant, but by the logic above it only means deeper puffs. Nothing gets filtered more than with plain water.
• Milk. It foams, the foam goes up the stem and into the hose, and once it warms up the smell isn't what you wanted. Hookah on milk was an internet trick, not science.
• Juice and wine. They add some flavour and that's it. The sugar from the juice stays in the base and the hose, and every hookah after that tastes off.
• Alcohol. It evaporates into the smoke you inhale, on top of the nicotine and carbon monoxide. That's not a filter, that's an extra.

The water is in the base for cooling, and there's nothing to improve there. The only thing that really matters: fresh water every time and a clean hose, because stale water and a damp hose collect what you don't want to breathe tomorrow.

What's true and what isn't

What actually helps

1. A shorter session. Smoke and carbon monoxide add up by the minute. Half an hour instead of an hour and a half is the biggest saving you can make.
2. Less charcoal, and natural charcoal. Two coconut cubes instead of three quick-light ones. The carbon monoxide comes from the charcoal, not from the tobacco.
3. A ventilated space. A terrace, an open window or a table by the door. Carbon monoxide builds up indoors, and not only from your hookah.
4. Don't count on the water. Fresh water every time, for taste and hygiene, not for a “filter”.
5. Your own mouthpiece, and a break when you feel dizzy. A brief head rush is the nicotine, but if the spinning lasts or your head hurts, it's carbon monoxide. Get some air.

How to set up a hookah so it smokes and smells as little as possible is in our guide on how to prepare a hookah, and where every part sits is on the 3D model. If you're just starting out, read the beginner's guide first.

FAQ

This is not medical advice. The numbers come from published studies: Al-Kazwini, Said and Sdepanian (BMC Public Health, 2015), Eissenberg and Shihadeh (2009), Cobb et al. (2011), the World Health Organization (2005, 2015), the US CDC.