Chronic Low-Level Nitrogen Dioxide Exposure and Mucociliary Clearance

Mucociliary clearance in the rat was studied by a new technique permitting repeated measurements over a period of several months. Two transport parameters were used: a first edge time (FET) and a 20% transport time (TPTT). When an animal was untreated, the FET and TPTT did not change significantly. A mean mucociliary velocity of 8.14 ± 4.01 mm/min was obtained from the FET measurements in 77 untreated rats. A six-week exposure to 6 ppm of nitrogen dioxide, (NO2) caused a significant increase in both parameters of transport despite large individual variations. In animals demonstrating a depression in mucociliary transport, there was no apparent abnormality and the functional impairment induced by NO2 was reversible within seven days.