BRONCHIAL HYPER-IRRITABILITY IN HEALTHY SUBJECTS AFTER EXPOSURE TO OZONE

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Abstract
The effect of a 2-h exposure to 0.6 ppm of ozone [environmental pollutant] on bronchial reactivity in 8 healthy, nonsmoking subjects was studied by measuring the increase in airway resistance (Raw) produced by inhalation of histamine diphosphate aerosol (1.6%, 10 breaths). Before exposure to ozone, histamine increased the mean Raw from 1.2 to 1.8 cm H2O/l per s. Immediately after exposure to ozone, the mean baseline Raw was unchanged, but the mean response to histamine was significantly greater than the pre-ozone response (Raw = 3.3 cm H2O/l per s; P < 0.05). For the group, this increase disappeared 1 day after exposure to ozone, although 2 subjects still had a significantly increased response to histamine for more than 1 wk after exposure. In 4 subjects, pretreatment with atropine sulfate aerosol (0.1-0.2 mg/kg body wt) blocked the increase in Raw produced by histamine after exposure to ozone. Brief exposure to 0.6 ppm of ozone produces bronchial hyperirritability via cholinergic postganglionic pathways, probably by damaging airway epithelium and thereby sensitizing bronchial irritant receptors.