Lung dosimetry for inhaled radon progeny in smokers

Abstract

Cigarette smoking may change the morphological and physiological parameters of the lung. Thus the primary objective of the present study was to investigate to what extent these smoke-induced changes can modify deposition, clearance and resulting doses of inhaled radon progeny relative to healthy non-smokers (NSs). Doses to sensitive bronchial target cells were computed for four categories of smokers: (1) Light, short-term (LST) smokers, (2) light, long-term (LLT) smokers, (3) heavy, short-term (HST) smokers and (4) heavy, long-term (HLT) smokers. Because of only small changes of morphological and physiological parameters, doses for the LST smokers hardly differed from those for NSs. For LLT and HST smokers, even a protective effect could be observed, caused by a thicker mucus layer and increased mucus velocities. Only in the case of HLT smokers were doses higher by about a factor of 2 than those for NSs, caused primarily by impaired mucociliary clearance, higher breathing frequency, reduced lung volume and airway obstructions. These higher doses suggest that the contribution of inhaled radon progeny to the risk of lung cancer in smokers may be higher than currently assumed on the basis of NS doses.

Cytogenetic biomonitoring of inhabitants of a large uranium mineralization area: the municipalities of Monte Alegre, Prainha, and Alenquer, in the State of Pará, Brazil

“…All our smoker subjects had low daily cigarette intake and most of them in an acute exposure. These data are in accordance with Baias et al (2010), who determined that the effects of acute smoking even protect the lung from radiation damage due to an increase in mucus secretion and in the thickness of this layer that can protect cells from alpha particles emitted from the gel phase of mucus layer. However, these apparent "advantages" of smoking disappear with continued exposure.…”

Lung Cancer Risk from Occupational and Environmental Radon and Role of Smoking in Two Czech Nested Case-Control Studies

“…Some of them include the impact of smoking on exposure, others exposure–dose relation and others dose-response relation in smokers and non-smokers as was reported by Baias et al [21]. Although the study does not provide evidence relevant to each of the reasons, the probable explanations include differences in lung morphometry of target cells, thickness of the mucous layer and mucociliary clearance between smokers and non-smokers.…”

Genetic modifiers of radon-induced lung cancer risk: a genome-wide interaction study in former uranium miners

“…Accordingly, a protective effect of smoking against radon induced LC was hypothesized and justified by thicker mucus layer and increased mucus velocities. Contrary, Baias et al (2010) calculated the local radiation dose due to inhaled radon progeny in bronchial target cells to be twice as high in heavy smokers compares to never smokers. However, the apparent “LC protection by smoking” perhaps results from interaction in opposite direction of genes at chromosome 15q25.1 with smoking- respectively radon-induced LC.…”