Effects of formaldehyde on the frog's mucociliary epithelium as a surrogate to evaluate air pollution effects on the respiratory epithelium

The increasing use of alcohol as an alternative fuel to gasoline or diesel can increase emission of formaldehyde, an organic gas that is irritant to t he mucous membranes. The respiratory system is the major target of air poll utants and its major defense mechanism depends on the continuous activity o f the cilia and the resulting constant transportation of mucous secretion. The present study was designed to evaluate the effects of formaldehyde on t he ciliated epithelium through a relative large dose range around the thres hold limit value adopted by the Brazilian legislation, namely 1.6 ppm (1.25 to 5 ppm). For this pur pose, the isolated frog palate preparation was use d as the target of toxic injury. Four groups of frog palates were exposed t o diluted Ringer solution (control, N = 8) and formaldehyde diluted in Ring er solution at three different concentrations (1.25, 2.5 and 5.0 ppm, N = 1 0 for each group). Mucociliary clearance and ciliary beat frequency decreas ed significantly in contact with formaldehyde at the concentrations of 2.5 and 5.0 ppm after 60 min of exposure (P <0.05). We conclude that relatively low concentrations of formaldehyde, which is even below the Brazilian thre shold limit value, are sufficient to cause short-term mucociliary impairmen t.