EFFECT OF ACROLEIN VAPOR ON UPPER RESPIRATORY-TRACT UPTAKE OF ACETALDEHYDE

Acetaldehyde and acrolein are nasal toxicant vapors that are both pres ent 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 tha t acrolein alters nasal uptake of acetone vapor; the current study was designed to determine ii acrolein alters nasal uptake of acetaldehyde vapor. Toward this end, uptake of acetaldehyde vapor at an inspired c oncentration of 14 mu g/L was measured in the surgically isolated uppe r respiratory tract (URT) of anesthetized male rats throughout a 40-mi n exposure to acetaldehyde alone or in combination with 2, 10, or 20 m u g/L acrolein. Uptake was measured under unidirectional inspiratory ( 50, 100, 200, or 300 ml/min) or pseudocyclic (207 ml/min mean inspirat ory flow) conditions. Although uptake of acetaldehyde vapors rapidly a ttains a steady state in animals exposed to this vapor alone, simultan eous exposure to acrolein resulted in non-steady-state acetaldehyde up take behavior, with uptake efficiencies steadily decreasing in the las t 20 min of exposure. Acrolein also produced a concentration-dependent reduction in net uptake during the exposure. For example at a flow ra te 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 p pm acrolein, respectively. The mechanisms of these responses are not k nown. However, these results demonstrate that caution is necessary in utilizing dosimetric data obtained during exposure to individual vapor s to predict relationships that may exist under complex exposure scena rios to multiple vapors.