Influence of hay and animal feed exposure on respiratory status: a longitudinal study

Our aim was to study respiratory symptoms and lung function decline in farmers, with particular attention to the influence of handling hay, straw and animal feed. From a cohort recruited in 1993-1994, 219 (82.6%) dairy farmers, 130 (62.5%) nondairy agricultural workers and 99 (66.4%) controls were re-evaluated in 2006. They answered medical and occupational questionnaires, underwent spirometric tests at both evaluations and pulse oximetry in 2006. Dairy and nondairy agricultural workers showed an increased risk for usual morning phlegm (adjusted OR 4.27 (95% CI 1.41-12.95) and 3.59 (95% CI 1.16-11.10), respectively). Animal feed handling was associated with increased risks of wheezing (p=0.01) and usual morning phlegm (p=0.04); hay or straw handling was associated with increased risk of wheezing (p=0.008). Adjusting for smoking, age, height, sex and altitude, dairy farmers had greater declines in forced expiratory volume in 1 s (FEV1)/forced vital capacity ratio (p=0.01) than controls. An increased decline in FEV1 for all agricultural workers was associated with animal feed handling, both measured as a categorical (currently versus never handling; p=0.05) or quantitative value (years of exposure during the survey period; p=0.03). Hay, straw or animal feed handling represents a risk factor of bronchial symptoms and, for animal feed only, of accelerated decline in expiratory flows.