The prevalence of bronchitis is elevated in agricultural workers despite their lower rates of cigarette smoking compared to the general population and other occupational cohorts. Nonsmoking farming populations appear to have a prevalence range of 3% to 30% for chronic bronchitis. Up to 13% to 20% of hog confinement workers may report symptoms consistent with chronic bronchitis. Exposures to grain dust, swine confinement areas, and poultry farming appear to be associated with the highest risk for bronchitis in the agricultural population. Grain workers may develop a dose-related, acute cross-shift decline in peak flow and a gradual reduction in forced expiratory volume in 1 second (FEV1) over the initial 2 weeks of exposure. Many workers also experience cough and dyspnea, which is initially reversible but recurs with seasonal reexposure to grain dust. With chronic exposure, approximately 20% of nonsmoking and up to 50% of smoking elevator workers develop cough and phlegm (84-91).

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