Abstract
Inhaled toxic aerosols of conventional cigarette smoke may impact not only the health of smokers, but also those exposed to second-stream smoke, especially children. Thus, less harmful cigarettes (LHCs), also called potential reduced exposure products (PREPs), or modified risk tobacco products (MRTP) have been designed by tobacco manufacturers to focus on the reduction of the concentration of carcinogenic components and toxicants in tobacco. However, some studies have pointed out that the new cigarette products may be actually more harmful than the conventional ones due to variations in puffing or post-puffing behavior, different physical and chemical characteristics of inhaled toxic aerosols, and longer exposure conditions. In order to understand the toxicological impact of tobacco smoke, it is essential for scientists, engineers and manufacturers to develop experiments, clinical investigations, and predictive numerical models for tracking the intake and deposition of toxicants of both LHCs and conventional cigarettes. Furthermore, to link inhaled toxicants to lung and other diseases, it is necessary to determine the physical mechanisms and parameters that have significant impacts on droplet/vapor transport and deposition. Complex mechanisms include droplet coagulation, hygroscopic growth, condensation and evaporation, vapor formation and changes in composition. Of interest are also different puffing behavior, smoke inlet conditions, subject geometries, and mass transfer of deposited material into systemic regions. This review article is intended to serve as an overview of contributions mainly published between 2009 and 2013, focusing on the potential health risks of toxicants in cigarette smoke, progress made in different approaches of impact analyses for inhaled toxic aerosols, as well as challenges and future directions.
Highlights
Cigarette smoke is a complex assemblage of liquid droplets, i.e., particulate phase, suspended in a mixture of gases and vapors
Borrowing the same idea that heating rather than combusting tobacco can provide a substantial reduction in many carcinogenic smoke constituents, Patskan and Reininghaus [3] proposed a new design of Electrical Heated Cigarettes (EHCs) whose previous product was Accord® (Philip Morris, 1997)
Apostolou et al [35] reported that Second-hand smoke (SHS)-inhalation increases the blood lead levels in US children, while Knudsen and Kleinstreuer [72] and Proietti et al [73] pointed out that exposure to SHS may cause disruptive embryonic vascular development and low birth weight
Summary
Cigarette smoke is a complex assemblage of liquid droplets, i.e., particulate phase, suspended in a mixture of gases and vapors. To reduce the potential health risks of cigarette smoking, manufacturers world-wide have introduced and marketed a variety of “less harmful cigarette (LHC)” products [10] in the past decades. To evaluate the potential health risks of new emerging cigarette products on humans, results from separate or combined experimental, clinical and numerical studies can be considered. It should be able to predict inhaled tobacco smoke droplet/vapor and toxicant deposition for a set of realistic inlet conditions on a subject-specific basis. We begin with a brief discussion of the toxicology of cigarette smoke, followed by the introduction of different manufacturing approaches and tobacco products, as well as their potential health risks to humans, especially to the most vulnerable population groups, i.e., children and seniors. The last section is devoted to challenges and future research directions
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