Hookah smoking involves passing air over heated tobacco or herbal mixtures, with the resulting emission traveling through a water-filled base before inhalation. A widespread belief among users is that this process purifies the substance, leaving only harmless water vapor to be inhaled. This common misconception is based on the visible cloud and the presence of water. However, the emission is a complex aerosol containing numerous toxins and particulate matter.
Smoke Versus Vapor: Defining the Physical State
True water vapor is a colorless, odorless gas phase of water, like steam, and is invisible to the naked eye. The large, visible cloud produced by a hookah is not pure vapor but a dense aerosol, a suspension of fine solid and liquid particles in a gas. This aerosol is generated through pyrolysis and combustion, which is the chemical decomposition of organic material caused by high heat.
The heat source, typically burning charcoal, causes the tobacco mixture to undergo thermal degradation, releasing chemical compounds and generating smoke particles. The shisha mixture is often saturated with glycerin, which, when heated, produces visible condensation that contributes to the cloud’s thickness. This visible cloud primarily consists of ultrafine particulate matter and condensed water and glycerin. These microscopic particles are a defining characteristic of smoke and can penetrate deeply into the lungs.
Chemical Composition of Hookah Emissions
The emissions inhaled during a session contain many of the same toxic compounds found in cigarette smoke, often at higher concentrations due to the extended duration of use. A major component is carbon monoxide (CO), generated primarily by the burning charcoal. Inhaling this gas significantly elevates CO levels in the blood, leading to oxygen deprivation.
The aerosol also carries numerous cancer-causing substances, including polycyclic aromatic hydrocarbons (PAHs) and volatile aldehydes such as formaldehyde and acrolein. Trace amounts of heavy metals are also delivered to the user, originating from both the tobacco and the heating element. Because a typical hookah session can last an hour or more, the total volume of smoke inhaled can be 100 to 200 times the volume inhaled from a single cigarette. This means a single session can expose a user to nearly nine times more carbon monoxide and significantly higher doses of other toxins.
The Role of the Water in the Pipe
The presence of water in the base of the pipe leads to the belief that the smoke is filtered or purified. However, the water’s main function is to cool the hot smoke before inhalation. As the smoke passes through the water, it loses heat, making the resulting aerosol feel smoother and less irritating to the throat and lungs.
This cooling effect is counterproductive, as the smoother smoke may encourage users to inhale more deeply and hold the smoke longer, increasing the dose of toxins absorbed. Research confirms that the water filters out very few hazardous, gas-phase chemical products. While the water may trap some larger particles, it provides negligible filtration against microscopic particulate matter, carbon monoxide, and other volatile organic compounds.
Specific Health Consequences
The inhalation of this toxic aerosol poses several direct health consequences for the user. An immediate risk is carbon monoxide poisoning, sometimes called “hookah sickness,” which causes symptoms like headache, nausea, and lethargy. The introduction of these toxins into the bloodstream also strains the cardiovascular system, raising heart rate and blood pressure.
Long-term use is associated with serious conditions, including various cancers, such as lung, oral, and bladder cancer. The constant exposure to particulate matter and inflammatory substances reduces lung function and increases the risk of respiratory diseases. Furthermore, the communal nature of hookah use, often involving the sharing of a mouthpiece, increases the risk of transmitting infectious diseases.