CARINAL AND TUBULAR AIRWAY PARTICLE CONCENTRATIONS IN THE LARGE AIRWAYS OF NONSMOKERS IN THE GENERAL-POPULATION - EVIDENCE FOR HIGH PARTICLE CONCENTRATION AT AIRWAY CARINAS

Objective - To evaluate the extent to which human airway carinas accum ulate ambient atmospheric particles, a newly developed technique was u sed to micro-dissect and analyse particle concentration in tubular seg ments and carinas of the large airways of 10 necropsy lungs from non-s mokers from the general population of Vancouver. Methods - Ratios of t he particle concentrations on the carinas to the tubular segment immed iately preceding it were measured with analytical electron microscopy for the mainstem bronchus, upper and lower lobe bronchi, and four diff erent segmental or subsegmental bronchi - that is, Weibel generations 1 to about 5. A total of 119 carinal-tubular pairs was evaluated. Resu lts - Over all cases, both carinal and tubular particle concentrations increased with increasing airway generation; the median ratio of cari nal to tubular particle concentration was 9:1 and did not show any tre nd with airway generation. The ratio was > 5 in 71% of carinal-tubular pairs, > 10 in 42% of pairs, > 20 in 31% of pairs, and > 100 in 9% of pairs. Some subjects showed a notable tendency to high ratios, with m any ratios > 100, and other subjects had a tendency reward low ratios. The predominant mineral species in both carinas and tubular airway se gments was crystalline silica and the relative proportion was similar in both sites; however, mean particle diameter was consistently less i n the carinal tissues. Conclusions - These findings suggest that the r atio of carinal to tubular retained particles in the large airways in non-smokers is higher than might be supposed from data generated in ai rway casts, and that there is considerable variation in this ratio bet ween subjects. This finding is of potential interest in models of carc inogen, toxin, and dose of fibrogenic agent to the large airways as it suggests high and sometimes extreme concentrations of toxic particles at carinas, and thus rein-forces the notion that carinas may be sites of initiation of disease.