Predictions of ozone absorption in human lungs from newborn to adult.

Although children are an important human population, dosimetry models for gases have been used to predict absorption mainly in laboratory animals and adult humans. To correct this omission, we have used several sources of data on age-dependent lower respiratory tract (LRT) volumes, age-dependent airway dimensions, a model of the adult tracheobronchial region, and a model of the adult acinus to construct theoretical LRT lung models for humans from birth to adulthood. An ozone (O3) dosimetry model was then used to estimate the regional and local uptake of O3 in the (theoretical) LRT of children and adults. For sedentary or quiet breathing, the LRT distribution of absorbed O3, the percent uptake (84 to 88%) and the centriacinar O3 tissue dose are not very sensitive to age. For maximal work during exercise, predicted LRT uptakes range from 87 to 93%, and the regional percent uptakes are more dependent on age than during quiet breathing. In general, the total quantity of O3 absorbed per minute increases with age. Regardless of age and state of breathing, the largest tissue dose of O3 is predicted to occur in the centriacinar region, where many animal studies show the maximal morphological damage from O3.