Distribution, Deposition, and Chemical Speciation of Mainstream Smoke Particles in Respiratory Tract of Smokers

Abstract

P-131 Abstract: The tobacco industry recently introduced potential reduced-exposure tobacco products (PREPs) that are marketed with claims that they are less harmful or addictive than conventional tobacco products because they supposedly deliver lower amounts of toxic, carcinogenic, and/or addictive chemicals to the user. Although these products have not yet found wide acceptance, their toxicity and potential impact on individual and public health is unknown. Available scientific evidence is insufficient for developing conclusions about whether there is any reduction in harm to users who switch to PREPs. Tobacco exposure biomarkers are needed that will provide an objective measure of the relationship between a reduction in tobacco toxins and biomarker endpoints. Because the most potent carcinogens in cigarette smoke are attached to particles, we developed and used a novel, non-invasive technique to measure the particle deposition of fine (0.1 < diameter < 4.0 μm) and ultra-fine (<0.1 μm) particles in the respiratory tract of smokers, and quantified the levels of the associated carcinogens. The system uses the Dekati Electrical Low Pressure Impactor (ELPI) to directly measure, without the use of sample collection bags, the particle concentration and size distribution in 12 aerodynamic diameters, ranging from 0.007–4.0 μm. Each subject's exhaled mainstream smoke was passed through a Nafion dryer into the ELPI. The mainstream smoke inhaled by each subject was simulated by first measuring his/her smoking topography (puff volume, flow, duration, and inter-puff interval) in a separate session, and then programming a flow controller/pump assembly attached to the ELPI's sampling inlet with that topography data. This system allowed each subject's freshly simulated inhaled mainstream smoke to flow directly into the ELPI. The measured concentration of particles in exhaled mainstream smoke divided by that measured in inhaled mainstream smoke represents the percent deposited in the respiratory tract. Real-time particle distribution data for exhaled breath showed that particle clearance, or the time it took for particle concentrations to return to baseline, was less than one minute for all particle sizes. The distribution of particles in exhaled breath generally showed two maxima, one at 0.007 μm and one at 0.15 μm. The number of particles corresponding to the lowest measurable cutpoint, 0.007 μm, is at least a factor of ten greater than that measured for the next five larger cutpoints, 0.027–0.26 μm. We extracted the substrates and quantified the tobacco-related carcinogens from the fine and ultra-fine particles collected from the inhaled and exhaled breath of smokers using gas chromatography/mass spectrometry. Preliminary results for fine and ultra-fine particles (<0.38 μm) in the exhaled breath of smokers show measureable nicotine (125–1,200 μg/m3), cotinine (6–9 μg/m3), NNN (∼0.3 μg/m3), and NNK (∼0.2 μg/m3).