A Waterpipe is not a Cigarette, it is not Even a Conventional Pipe

A waterpipe is not a cigarette. It is not even a conventional pipe. However, those who have been in charge of standards-setting bodies such as CORESTA and ISO Technical Committee TC 126 on Tobacco and Tobacco Products have tried to make waterpipe and other forms of tobacco products and devices behave the same as cigarettes. This is particularly true for ISO Standard 22486:2019 (1) and the accompanying ISO Technical Specifications 22487:2019 (2) and 22491:2019 (3). When one reads 22486, one sees specifications with narrow tolerance on puff duration, puff volume, puff frequency, and pressure drop with apparently no experimental data to back up those tolerances. Perhaps those tolerances were set by the manufacturer, Borgwaldt KC GmbH, that designed and built the shisha smoking machine in 2014. However, the puffing parameters for the machine are not the major problems. The electric heater and the bowl that holds the shisha are.

The electric heater was designed to be used without foil over the shisha (waterpipe tobacco) in the bowl (waterpipe tobacco holder) of the hookah. This is problematic because it does not reflect typical consumer behavior as most use perforated aluminum foil over the bowl to hold the glowing charcoal briquettes. This was noted by Wilkinson (4) and Miller-Holt et al. (5). Moreover, we have found that using perforated foil with the small and large versions of the Hady E-Shisha Smokepans prevents scorching, and in one case partial combustion (particles nearest the surface of the heater turned gray) of the shisha by the electric heating (6, 7). The lack of foil in the current ISO standard has the potential to increase the amounts of toxic components in the emission. Even with foil, tobacco temperatures in electrically-heated bowls have been reported to range from 286 °C to 300 °C depending on heater power versus 150 °C when charcoal was used (8). In another study on electrically heated shisha bowls, scientists at the US FDA's Center for Tobacco Products (CTP) reported a new electric heater for shisha bowls (9). Comparisons were made between charcoal heating, a no-longer available commercial electric heater, and the new heater using Nakhla Two Apples shisha and a puffing protocol similar to that specified in ISO 22486:2019. Two of the parameters determined (n = 3 separate runs) were maximum temperature of the shisha during heating and shisha mass loss during the heating process. For charcoal heating, tobacco temperature was 118.5 ± 3.38 °C and mass loss was 31.35 ± 2.58%. For the new electric heater set at 350 °C, tobacco temperature was 118.3 ± 0.98 °C, and the mass loss was 26.14 ± 0.96%. The temperature setting of the new heater had to be raised to 370 °C to match the mass loss with charcoal heating. Reported tobacco temperature at the 370 °C setting was just under 180 °C. This temperature increase could mean more tobacco-related pyrolysis (10).

The typical way of determining mass loss is to weigh the bowl before adding shisha and then weigh it again after the shisha has been added. The difference is the net weight of shisha added to the bowl. The bowl and shisha is weighed again and the weight of the bowl is subtracted from that value. This is the weight of the residue. Mass loss is typically reported as percent lost. So weight of residue divided by net weight of shisha added to the bowl times 100% gives the percent mass loss. There are two plausible explanations for the reported difference in mass loss: 1) the evidence for the first is found in the much larger standard deviation for temperature for the charcoal-heated shisha; when a puff is taken, room air is drawn over the glowing charcoal causing it to burn faster. This in turn increases the temperature of shisha and hence more mass loss; and 2) there are no holes in the body of the new heater that allow the air drawn in by the puff to enter the foil-covered bowl; this only allows the air that passes between the heater and the foil to enter the bowl; and thus, no heated air is available to heat the shisha as in the cases of charcoal heating. Not all shisha tobaccos are the same. They not only differ by the type of tobacco used [flue-cured (FC) or dark air-cured (DAC)], but also by ratios of tobacco/glycerol/sugar syrups [often high fructose corn syrup (HFCS)] (11). Also, some flavorings such as citrus oils are used in relatively large amounts and are composed mostly of limonene (boiling point: 176 °C); other volatile solvents used as flavor carriers include ethanol and water. Moreover, one brand of shisha uses a 50/50 mixture of glycerol and propylene glycol (PG) instead of glycerol as the major contributor to the aerosol (12). The presence of the large amount of PG reduces the amount of heat required to produce the aerosol and more mass is lost in the early part of the hour-long puffing sequence specified in ISO 22486:2019.

The shishas also differ in particle size distribution (12). Generally, shishas based on DAC tobaccos have much smaller particles than their FC counterparts. Moreover, DAC tobaccos will absorb less of the solutions of glycerol and sugar syrups that are applied to the tobaccos and hence are more fluid than their FC counterparts both at ambient temperatures and when heated. Thus, when Egyptian-style bowls such as the one specified in ISO 22486:2019 are used, the particles of tobacco and the fluid around them are sucked down into the suction tube (6). This may not be obvious to the users of instrumentation fabricated to meet the ISO standard. However, it is very obvious to those who use retail shisha bowls such as the Mya Egyptian Bowl (13) even though the holes in the bottom of the Mya bowls are about 3 mm in diameter instead of the 5 mm specified in the ISO standard. After runs with both commercial and laboratory-prepared DAC shishas, particles of tobacco can be found underneath the bowl and liquid can be found on the bowl grommet. Thus, sample integrity has been compromised. The solution to this problem is to use a phunnel bowl instead of the Egyptian-style bowl (14). Another benefit of the phunnel bowl over the Egyptian-style bowl (Mya) is that it appears to reduce the final shisha temperature at the end of the puffing period.

This is very important as sugar-derived aerosol toxicants (furanic compounds) increase with increasing mass loss as mass loss is related to temperature of shisha during heating (9). In addition, the following quotation from an article by Schubert et al. (15) shows the importance of temperature control during the process of determination of shisha emissions; “The generation of furanic compounds during a waterpipe smoking session depends mainly on four parameters. These are the steepness of the temperature increase and the maximum temperature finally reached in the tobacco head during the smoking process, as well as the levels of carbohydrates and humectants being already present in the unburned tobacco.”

The shisha industry is under attack, not only due to flavorful products and perceived attractiveness by public health authorities (16), but also by those who chose to focus on toxicity related to sugar-derived toxicants but ignore the toxicants from the charcoal heating sources (17). We would not accept the test results from other tobacco products whose integrity was compromised by the testing protocol. Why should we make an exception for shisha? It is time for the leadership of ISO TC 126 on Tobacco and Tobacco Products to organize the work required to develop the instrumentation and protocols that would cover all commercial shisha products and provide results that are supported by the chemistry, not the politics. This may well require specific instrumentation for each major type of shisha and revision of methods for sampling and chemical and physical characterization of shisha products.