Enhanced Response to Ozone Exposure during the Follicular Phase of the Menstrual Cycle

Exposure to ozone ( O3), a toxic component of photochemical smog, results in significant airway inflammation, respiratory discomfort, and pulmonary function impairment. These effects can be reduced via pretreatment with anti-inflammatory agents. Progesterone, a gonadal steroid, is known to reduce general inflammation in the uterine endometrium. However, it is not known whether fluctuations in blood levels of progesterone, which are experienced during the normal female menstrual cycle, could alter O3inflammatory-induced pulmonary responses. In this study, we tested the hypothesis that young, adult females are more responsive to O3inhalation with respect to pulmonary function impairment during their follicular (F) menstrual phase when progesterone levels are lowest than during their mid-luteal (ML) phase when progesterone levels are highest. Nine subjects with normal ovarian function were exposed in random order for 1 hr each to filtered air and to 0.30 ppm O3in their F and ML menstrual phases. Ozone responsiveness was measured by percent change in pulmonary function from pre- to postexposure. Significant gas concentration effects (filtered air versus O3) were observed for forced vital capacity (FVC), forced expiratory volume in 1 sec ( FEV1), and forced expiratory flow between 25 and 75% of FVC ( FEF25-75; p