BRONCHIAL REACTIVITY, ATOPY, AND AIRWAY RESPONSE TO COTTON DUST

Studies of cotton textile workers have found an association between at opy and drop in FEV1 over a workshift. We studied the response of prev iously nonexposed volunteers with and without a history of mild atopy to a 5-h exposure to 1 mg/m3 of respirable cotton dust in a model card room. All participants were nonsmokers, had no history of asthma, and had normal spirometry. Twenty atopic subjects gave a personal history of mild respiratory allergy to pollen, dusts, or animals that had been confirmed by a physician. Thirty-two nonatopic subjects had no histor y of allergy. Spirometry and a methacholine challenge test were perfor med 1 to 2 days prior to exposure. Spirometry was repeated immediately before exposure to cotton dust; spirometry and a methacholine challen ge were performed immediately after exposure. Atopic subjects showed a significantly higher mean serum IgE level to Phadiatop(R), a screenin g test to common inhalant allergens, than did nonatopic subjects (mean percent binding, 32.1 versus 1.5; p < 0.001). Atopic subjects had a s ignificantly greater mean fall in FEV1 during exposure (8.3% versus 4. 9%, p < 0.05). The difference in FEV1 decline between atopic and nonat opic subjects was similar in magnitude to that reported for workshift FEV1 declines between textile workers with and without mild atopy. Ato pic subjects had significantly higher baseline methacholine responsive ness than did nonatopic subjects (26% versus 0% reaching a PD20, p < 0 .0005). After cotton dust exposure, there was a significant increase i n airway reactivity in both groups (68% versus 20% reaching a PD20, P < 0.0005). For all subjects combined baseline responsiveness was signi ficantly related to the change in FEV1 after exposure. These results s uggest that a history of mild atopy is a predictor for decrements in F EV1 after exposure to cotton dust in previously nonexposed healthy per sons. Even in nonatopic persons a transient increase in airway reactiv ity may be produced by cotton dust exposure.