EFFECT OF NITROGEN-DIOXIDE AND SULFUR-DIOXIDE ON AIRWAY RESPONSE OF MILD ASTHMATIC-PATIENTS TO ALLERGEN INHALATION

Air pollution may enhance the airway response of asthmatic subjects to allergen inhalation. To test the hypothesis that sulphur dioxide and nitrogen dioxide alone or in combination could have a contributory rol e, we have studied the effect of 6 h exposure to air, 200 parts per bi llion (ppb) sulphur dioxide, 400 ppb nitrogen dioxide, and the two gas es together on the airway response to inhaled allergen in ten voluntee rs with mild atonic asthma. The subjects were exposed to the gases in random order at weekly visits, then challenged with pre-determined con centrations of Dermatophagoides pteronyssinus allergen 10 min after ea ch exposure. The forced expiratory volume in 1 s (FEV(1)), forced vita l capacity (FVC), and cumulative breath units (CBU) of D pteronyssinus allergen required to produce a 20% fall in FEV(1) (PD(20)FEV(1)) were measured after each exposure. Compared with air, neither sulphur diox ide nor nitrogen dioxide nor the combination significantly altered FEV (1) or FVC. Although the decreases in PD(20)FEV(1) after exposure to e ach agent alone were not significant (41.2%, p=0.125 after nitrogen di oxide; 32.2%, p=0.506 after sulphur dioxide) the decrease after exposu re to the combination was significant (60.5 [SE 8.1]%, p=0.015). Expos ure to a combination of sulphur dioxide and nitrogen dioxide in concen trations that could be encountered in heavy traffic enhances the airwa y response to inhaled allergen, possibly as a result of previous airwa y inflammation.