Mainstream smoke of the waterpipe: Does this environmental matrix reveal as significant source of toxic compounds?

Abstract

In recent years the number of waterpipe smokers has increased substantially worldwide. Here we report on the concentrations of tobacco-specific nitrosamines (TSNAs) and polycyclic aromatic hydrocarbons (PAHs) in waterpipe smoke and the analysis of selected biomarkers indicative for the body burden in waterpipe users. We further identify high amounts of unburned humectants (glycerol and propylene glycol) in the waterpipe smoke as main part of the so-called “tar” fraction. These results give cause for serious concern. For standardization we applied a machine smoking protocol. Smoke was collected on glass fiber filters and analyzed for nicotine, water, humectants, TSNAs, and PAHs. In addition, we determined carbon monoxide and found high amounts in the smoke being causative for high levels of carboxyhemoglobin (COHb) in the blood of smokers. In comparison to the reference cigarette 3R4F, the nicotine contents were 10-times higher, but TSNA levels were found lower in waterpipe smoke. This finding explained the low levels of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol detected in the urine of waterpipe smokers. Finally, the levels of benzo[a]pyrene were three times higher in waterpipe smoke compared to the reference cigarette. Altogether, the data presented in this study point to the health hazards associated with the consumption of waterpipes.

Introduction

The waterpipe is a traditional aid for tobacco consumption in Asia and Northern Africa (Maziak et al., 2004a). Although exact numbers are missing to date, web blogs, “hookah bar” advertisements and the advent of popular waterpipe stores indicate that both the general interest and the number of young people smoking waterpipes have considerably grown in recent years in European countries and North America (BZgA, 2008, Jackson and Aveyard, 2008, Primack et al., 2008).

There are major differences in the consumption of waterpipes and cigarettes: The flavored tobacco, mainly used for waterpipes in Europe and the US, contains huge amounts of humectants such as glycerol and propylene glycol. The humectants prevent the tobacco from burning thereby yielding a smooth and pleasant smoke. Furthermore, the heat for the waterpipe is generated using charcoal, which is placed on top of the tobacco head. Studies from Lebanon showed that smoking habits differ greatly between waterpipe and cigarette smokers (Shihadeh et al., 2004). For instance, average inhalation volumes were about 530 ml for single waterpipe puffs whereas the puff volumes found for cigarette smoking were in the range of 35–60 ml (Hammond et al., 2007). Furthermore, the smoking time differs greatly. For a waterpipe with 10 g tobacco the smoking time amounted to almost 60 min and 171 puffs whereas the time for a cigarette is between 5 and 10 min (6–11 puffs). Shihadeh and colleagues established a machine-smoking protocol, which is based on the investigations of smoking behavior of waterpipe smokers in Lebanon, and investigated several constituents of waterpipe smoke such as carbon monoxide (CO), polycyclic aromatic hydrocarbons (PAHs), various aldehydes (e.g., formaldehyde, acetaldehyde, acrolein), and certain metals (e.g., lead, chromium, arsenic) (Al Rashidi et al., 2008, Monzer et al., 2008, Sepetdjian et al., 2008, Shihadeh, 2003, Shihadeh and Saleh, 2005).

In the present study three major questions were addressed: firstly, we determined the levels of tar, nicotine and CO in the waterpipe smoke. To assess the internal body burden of these toxins, biomonitoring of nicotine and carboxyhemoglobin (COHb) in the blood and of cotinine in the urine of smokers was performed. Since the amounts of tar were high in waterpipe smoke, we investigated its composition and found high amounts of humectants. Secondly, the levels of tobacco-specific nitrosamines (TSNAs) were measured in tobacco, tobacco smoke and in the urine of consumers. Since N′-nitrosonornicotine (NNN) and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) have been classified as human carcinogens (IARC, 2007), we determined the contents of these compounds in waterpipe tobacco and smoke. As biomarker of NNK its metabolite 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) was analyzed. Thirdly, various PAHs such as benzo[a]pyrene were measured in the waterpipe smoke. Benzo[a]pyrene has been classified as human carcinogen (IARC, 2010) and serves as well-established carcinogenic lead compound of environmental PAH mixtures since decades.