EFFECT OF ACROLEIN VAPOR ON UPPER RESPIRATORY TRACT UPTAKE OF ACETALDEHYDE

Abstract

Acetaldehyde and acrolein are nasal toxicant vapors that are both present in tobacco smoke. Quantitative risk assessment for inhaled vapors requires knowledge of the relationship between inspired concentration and delivered dose. Previous studies in this laboratory have shown that acrolein alters nasal uptake of acetone vapor; the current study was designed to determine if acrolein alters nasal uptake of acetaldehyde vapor. Toward this end, uptake of acetaldehyde vapor at an inspired concentration of 14 mug/L was measured in the surgically isolated upper respiratory tract (URT) of anesthetized male rats throughout a 40-min exposure to acetaldehyde alone or in combination with 2, 10, or 20 mug/L acrolein. Uptake was measured under unidirectional inspiratory (50, 100, 200, or 300 ml/min) or pseudocyclic (207 ml/min mean inspiratory flow) conditions. Although uptake of acetaldehyde vapors rapidly attains a steady state in animals exposed to this vapor alone, simultaneous exposure to acrolein resulted in non-steadystate acetaldehyde uptake behavior, with uptake efficiencies steadily decreasing in the last 20 min of exposure. Acrolein also produced a concentration-dependent reduction in net uptake during the exposure. For example at a flow rate of 200 ml/min, net URT acetaldehyde uptake efficiency averaged 43, 39, 24, and 24% in animals simultaneously exposed to 0, 2, 10, or 20 ppm acrolein, respectively. The mechanisms of these responses are not known. However, these results demonstrate that caution is necessary in utilizing dosimetric data obtained during exposure to individual vapors to predict relationships that may exist under complex exposure scenarios to multiple vapors.