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Inhalation of organic dust, including endotoxin, has been associated with inflammatory response of the pulmonary system. Limited studies have evaluated the work shift effects of endotoxin on respiratory outcomes for workers in the dairy industry, such as spirometry changes. Measurement techniques for exhaled nitric oxide (eNO) have been standardized by the American Thoracic Society (ATS) and used as a biomarker to identify diseases marked with lung inflammation. Dairy parlor workers are known to work long hours in one location with little job variability. The objectives of this study were to quantify exposure concentrations of inhalable dust and endotoxin among dairy parlor workers, evaluate acute cross-shift changes in respiratory status using spirometry, and assess the effectiveness of exhaled nitric oxide for detecting cross-shift bronchial inflammation changes.
The cross-sectional study recruited 62 dairy parlor workers from 10 large herd dairy farms across Iowa, Minnesota, Wisconsin, and South Dakota. Data collected before and after the work shifts included spirometry tests, eNO measurements, and pulmonary symptom questionnaires. Personal breathing zone exposure to inhalable dust was assessed during the shift using Button Aerosol Samplers. Gravimetric analysis was used to determine airborne concentrations of inhalable dust and endotoxin concentration was determined using the recombinant factor C assay.
Inhalable dust concentrations ranged from 0.09 - 4.95 mg/m3 with a geometric mean of 0.58 mg/m3. Inhalable endotoxin concentrations ranged from 4-1968 EU/m3 with a geometric mean of 117 EU/m3. The study participants pre-shift forced expiratory volume in the first second (FEV1) as a percentage of predicted was an average of 93.4%. Study group cross-shift FEV1 decreased by -1.16%. Six participants with moderate post-shift concentrations of eNO had an average FEV1 cross-shift change of -3.19%. Dairy parlor workers are exposed to concentrations of organic dusts that may adversely impact health. Future studies should test interventions in milking parlors to reduce dust exposure among dairy workers.