CSP Deposition to the Alveolar Region of the Lung: Implications of Cigarette Design

Abstract

Ventilated cigarettes were designed to reduce the levels of smoke under machine testing conditions; however, smokers alter their smoking pattern to compensate for the reduction in yields. A relative shift in incidence of lung cancer from the more central lung airways to the alveolar region has also been associated with ventilated cigarette use. Validated mathematical models indicate that particle deposition patterns in the lung depend on particle size and inhalation behavior, including inhalation volume, flow rate, and breath-hold time. This article finds that most mathematical models underpredict total cigarette smoke particulate (CSP) deposition in the lung, likely because they do not account for coagulation, hygroscopicity, and cloud dynamics, which may increase the effective particle diameter of CSP reaching the lung tissue. The models that include these processes indicate that puff volume would be unlikely to affect particle deposition in the lung, but puff time, inhalation depth, breath-hold time, and exhalation time may affect total deposition. Most compensation appears to occur through a combination of increased puff volume and puff flow, with possible increases in inhalation depth and breath-hold time. The complex interaction between the extent of cigarette ventilation, which can affect puffing/inhalation behavior, CSP concentration, and CSP size with CSP dose to the alveolar versus more central lung airways is described. Deposition efficiency in the alveoli could plausibly be increased through compensation, but it is still unclear whether compensation could sufficiently alter patterns of CSP deposition in the lung to elicit a shift in lung cancer sites.

Do changes in cigarette design influence the rise in adenocarcinoma of the lung?

“…The increase in puff volume and depth of inhalation observed among smokers of lower tar yield cigarettes might increase the exposure of lung alveolar cells to the carcinogens in smoke. Modeling of smoke deposition in the lungs of smokers resulting from compensatory changes in smoking behavior suggests that this effect is likely to occur, but the magnitude of the effect may not be large enough to explain the observed shift to adenocarcinoma [33]. A second mechanism is an increase in the levels of tobacco-specific nitrosamines in US cigarettes over time [8, 32].…”

Has the lung cancer risk from smoking increased over the last fifty years?

“…Ventilated filters increase the puff volume used by the smoker and may lead to deeper inhalation of the smoke increasing the smoke exposure to the lung [28]. Increasing nitrosamine levels may make the smoke more carcinogenic at any level of exposure.…”

Cigarette Smoke Cadmium Breakthrough From Traditional Filters: Implications for Exposure

“…42 As a consequence of multiple changes in cigarette design over the last 50 years, 43 and consequent changes in smoking habits, an increasing trend toward adenocarcinoma in distal lung relative to the previously more common small cell carcinoma in proximal lung has been observed though small cell carcinoma risk from smoking is still high. 44,45 If cadmium precipitates in particulate that consists of smaller particles than the CMDs discussed here, then cadmium would be expected to penetrate more deeply into the lung.…”

“…Deep lung penetration by small particles enriched in cadmium and possibly other carcinogens may be a partial explanation for the increase in distal lung adenocarcinomas that have been correlated with changes in cigarette design and smoking habits. 26,42–45 …”