Background
Ammonia is a chemical additive found in tobacco filler [
1‐
4]. It increases nicotine dependence in cigarette smokers and has been included in the non-exhaustive priority list of 39 tobacco contents and emissions of cigarette by the World Health Organization (WHO) Study Group on Tobacco Product Regulation [
1]. The effects of ammonia present in tobacco filler on cigarette smoke, such as increasing its alkalinity, which in turn increases the amount of unprotonated nicotine in cigarette smoke, have been examined extensively [
1]. Unprotonated (“free-base”) nicotine is lipophilic and is absorbed more quickly into the bloodstream than its protonated form [
1]. The increase in free-base nicotine increases the addictive potential of cigarettes [
2]. Thus, the role of added ammonia in increasing the delivery of free-base nicotine to the brain has been suggested as an ammonia technology. A recent study analyzed the levels of nicotine in the blood of participants who smoked cigarettes containing different levels of ammonia in the tobacco filler, and no differences in nicotine levels were found [
5]. As a result of this study, ammonia technology is regarded a legacy technology. However, this study did not use products with very low levels of ammonia in their tobacco fillers; therefore, the influence of the amount of ammonia in tobacco filler on nicotine absorption is still unknown. Currently, tobacco industries are developing alternative technologies and approaches to ammonia technology. There are 600 additives besides ammonia contained in tobacco products (including cocoa, caramel color, menthol, and rum and its flavors) [
6]. Furthermore, there are 188 additives listed on the homepage of Japan Tobacco Inc. [
7]. For instance, menthol allows the deeper inhalation of cigarette smoke since it has local anesthetic qualities. A deeper puff of smoke is achieved, and the dose of nicotine per puff is higher. The sale of flavored tobacco products, such as menthol capsule cigarettes, is not regulated in Japan. Therefore, manufacturers can use additives other than ammonia, such as menthol and cocoa. As the ammonia levels in commercially marketed cigarette brands in Japan have not been disclosed, the ammonia levels of these cigarettes should be investigated.
The ammonia levels in tobacco fillers of foreign cigarette brands have been analyzed [
8‐
10]. Canadian cigarette brands reportedly contain significantly lower levels of ammonia than US cigarette brands [
9]. Moreover, in the USA, ammonia levels differ significantly between tobacco manufacturers [
10]. Although several countries now monitor the ammonia levels of cigarettes, the Japanese government has yet to set forth monitoring requirements for ammonia in commercially marketed cigarettes. In 2005, Philip Morris USA reported that the ammonia levels of five cigarette brands sold in Japan ranged from 1.06 to 3.28 mg/g [
8]. However, the ammonia levels of Japanese cigarette brands have not been reported.
Another important aspect that needs to be investigated is the amount of ammonia transferred from the tobacco filler to cigarette smoke. The ammonia levels in mainstream smoke have not been determined separately from that transferred from tobacco filler as mainstream smoke contains much less ammonia (3.1–29.0 μg/cigarette according to the International Organization for Standardization (ISO)) [
8] than tobacco filler. The US Surgeon General [
11] reported that the ammonia levels of sidestream smoke are significantly higher, resulting in a more alkaline pH [
12]. Additionally, due to its corrosive and exothermic nature, ammonia can cause immediate injury to the mucosa of the eyes, skin, oral cavity, and respiratory tract. Monitoring hazardous chemicals in tobacco smoke is essential for the regulation of tobacco products. The analysis of toxicants in mainstream smoke is also required according to articles 9 and 10 of the WHO Framework Convention on Tobacco Control (FCTC)—regulation of the contents and disclosures of tobacco products. Accordingly, we hypothesized that the transfer of ammonia from tobacco filler to smoke and differences between ammonia levels of different cigarette brands can be confirmed by analyzing the ammonia levels in sidestream smoke.
The analytical methods for ammonia in tobacco filler are mainly based on ion chromatography. Among those, the methods proposed by the WHO and Cooperation Centre for Scientific Research Relative to Tobacco (CORESTA) are fast and reliable [
13,
14]. Ion chromatography is widely used for studying various anions and cations in water and allows simultaneous analysis of cations other than ammonia. Ion chromatography has also been used to analyze ammonia in mainstream cigarette smoke [
15]. However, purchasing and maintaining ion chromatography instruments only for analyzing ammonia in tobacco filler and tobacco smoke is relatively expensive. Jansen et al. proposed an analytical method that uses clinical analyzers based on enzyme reactions [
16]. In addition, in the water research field, the colorimetric method has been generally followed to determine ammonia levels by using an absorption spectrometer, which is generally available in most analytical laboratories. This method is based on the salicylate-chlorine reaction [
17] and has sensitivity and specificity for ammonia analysis of tobacco products. Therefore, we followed this method to analyze the ammonia levels in tobacco filler as well as in sidestream smoke.
The aim of this study was to develop a colorimetric method for determining ammonia levels in tobacco filler and sidestream smoke using an absorption spectrometer and two reagents (sodium nitroprusside and sodium dichloroisocyanurate). The proposed method was compared to ion chromatography, the ammonia levels of different Japanese cigarette brands were measured, and ammonia levels in cigarettes of four tobacco manufacturers in the Japanese market were compared. The proposed method was then used to determine the ammonia levels in sidestream smoke and whether the ammonia detected in sidestream smoke is directly transferred from tobacco filler or is formed through the pyrolysis of the nitrogenous compounds in tobacco filler.
Acknowledgements
The authors thank Ms. Yasuko Hara, Ms. Sayuri Hayashi, and Mr. Tadamichi Ohkubo of the National Institute of Public Health, Japan, for the technical support.