Inhaled concentration (C), minute volume (MV), and exposure duration (T) are factors that may affect the uptake of ozone (O3) within the respiratory tract. Ten healthy adult nonsmokers participated in four sessions, inhaling 0.2 or 0.4 ppm O3 through an oral mask while exercising continuously to elicit a MV of 20 l/min for 60 min or 40 l/min for 30 min. In each session, fractional absorption (FA) was determined on a breath-by-breath basis as the ratio of O3 uptake to the inhaled O3 dose. The mean ± SD value of FA for all breaths was 0.86 ± 0.06. Although C, MV, and T all had statistically significant effects on FA (P < 0.0001, P = 0.004, and P = 0.026, respectively), the magnitudes of these effects were small compared with intersubject variability. For an average subject, a 0.05 change in FA would require that C change by 1.3 ppm, MV change by 46 l/min, or T change by 1.7 h. It is concluded that inhaled dose is a reasonable surrogate for the actual dose delivered to a particular subject during O3 exposures of <2 h, but it is not a reasonable surrogate when comparisons are made between individuals.
All Science Journal Classification (ASJC) codes
- Physiology (medical)