ORIGINAL ARTICLE Acute Pulmonary Function Change Associated With Work on Large Dairies in California Chelsea Eastman, PhD, MPH, Marc B. Schenker, MD, MPH, Diane C. Mitchell, PhD, Daniel J. Tancredi, PhD, Deborah H. Bennett, PhD, and Frank M. Mitloehner, PhD Objective: To study whether dairy workers in California have lower baseline and greater cross-shift decrements in lung function than control employees. Methods: A cross-sectional study of 210 dairy and 47 control workers who completed questionnaires and spirometry before and after the work shift. Results: Dairy work was associated with mean baseline differences of −0.132 L (P = 0.07) and −0.131 L (P = 0.13) in forced expiratory volume in 1 second and forced vital capacity, respectively, compared with control employees, adjusting for age, height, smoking status, and days back at work since last day off. Dairy work was associated with a mean cross- shift difference of −65.2 mL (P = 0.02) and −103.1 mL (P < 0.01) in forced expiratory volume in 1 second and forced vital capacity, respectively, adjusting for smoking status and work-shift time. Conclusions: Dairy work in California was associated with mild acute airway obstruction. The unclear long-term effect of dairy work in California merits further investigation. D airy work has been associated with an increased preva- lence of respiratory symptoms, including chronic bronchitis, wheeze, allergies, hypersensitivity pneumonitis, and organic dust toxic syndrome. 1–7 Dairy farming also has been associated with an accelerated decline in the ratio between forced expiratory volume in 1 second (FEV 1 ) and forced vital capacity (FVC) and with moder- ate airway obstruction. 1–3,5 Sufficient exposure to organic particles, specifically endotoxins, may result in dose-dependent organic dust toxic syndrome. The endotoxin content of respirable dust has been associated with decreased FEV 1 . 8,9 Although previous studies have documented the association between dairy work and decrements in respiratory health, the situa- tion in California is distinctive. In 2007, California’s dairies had an average herd size of 952 cows. 10 By contrast, the second and third highest-producing dairy states Wisconsin and New York had aver- age herd sizes of 88 and 108 cows, respectively. 10 European dairies had even smaller herds, ranging in size from an average of 35 cows (Belgium) to 78 cows (the United Kingdom). 11 In addition to sub- stantially larger herd sizes, California’s dairy facilities have naturally ventilated barns or open corrals in contrast to enclosed dairy barns in Europe and the eastern United States. 10,11 We aimed to determine whether the much larger herd size but open-air ventilation of the facilities in California resulted in lower or higher concentrations of air pollutants relative to previous studies, and whether there were any health concerns due to possibly different types of air pollutants that might be generated on these western US facilities. Given this unique From the Departments of Public Health Sciences (Drs Eastman, Schenker, Mitchell, and Bennett), Pediatrics (Dr Tancredi), and Animal Science (Dr Mitloehner), University of California, Davis; and Centre for Research in Environmental Epidemiology (CREAL) (Dr Eastman), Barcelona, Spain. Support for this research was provided by the National Institute for Occupa- tional Safety and Health grant OH00770-07 and the University of California Toxic Substances Research and Teaching Program through the Atmospheric Aerosols and Health Lead Campus Program (aah.ucdavis.edu). The authors declare no conflict of interest. Address correspondence to: Marc B. Schenker, MD, MPH, Rm 138 MS1-C, Department of Public Health Sciences, University of California, Davis, CA 95616 (mbschenker@ucdavis.edu). Copyright C  2013 by American College of Occupational and Environmental Medicine DOI: 10.1097/JOM.0b013e318270d6e4 arrangement, we studied whether dairy workers in California have lower baseline and greater cross-shift decrements in lung function than control employees. MATERIALS AND METHODS Study Subjects and Design Male participants from 13 dairy facilities and a control facility in California completed questionnaires and spirometry before and after the work shifts from June to September 2008. The control facility (a vegetable-processing plant) was selected on the basis of a similar worker population (eg, ethnicity, income, and education) with a night shift. Study design, methods, and survey protocols have been described previously. 12 Spirometry All pulmonary function tests (PFTs) were performed by National Institute of Occupational Safety and Health–trained and certified spirometry technicians using EasyOne R  spirometers (Med- ical Technologies, Inc, Andover, MA). Questionable spirograms were reviewed by a pulmonary physician with extensive experience in treating adverse health effects of occupational respiratory exposures. Two hundred twenty-six dairy workers and 49 control em- ployees completed all study protocols. Of these, 16 dairy workers (7.1%) and two control employees (4.1%) were excluded from PFT analyses because of incomplete or unusable spirograms. The remain- ing 257 participants were divided into categories on the basis of the variability of the two best maneuvers. The first category followed American Thoracic Society (ATS) recommendations (less than 5% variability). 13 The second, more highly variable (5% to 8% variability category) was created to test whether we could include participants who had less reproducible spirograms, perhaps because they were sick or had less formal education. The spirometry values themselves are less reproducible, but it’s also the participants performing spirom- etry and so in a way they are less reproducible themselves. Sicker patients have a harder time producing reproducible spirograms. 14 Participants with more than 8% variability were excluded from anal- yses. Each PFT measure was considered separately (ie, a participant could be included in analyses for FEV 1 but if his FVC measures had higher than 8% variability, then he was excluded from FVC analy- ses). Categorization of ratio measures from participants was based on whichever component in the ratio displayed a greater variabil- ity; for example, if a participant had more than 8% variability for FEV 1 but less than 5% variability for FVC, the FEV 1 /FVC ratio would be categorized as having more than 8% variability (ie, unus- able). To estimate baseline forced expiratory flow between 25% and 75% of FVC (FEF 25%–75% ), all the most highly variable spirograms were excluded using the categorization of FEV 1 /FVC. Baseline and cross-shift changes in FEV 1 , forced expiratory volume in 6 seconds (FEV 6 ), FVC, FEF 25%–75% , FEV 1 /FEV 6 , and FEV 1 /FVC were mod- eled separately as outcome measures in regression models. Cross- shift changes were calculated by subtracting the measure before the shift measure from the measure after the shift. Analysis To account for possible clustering by facility, we used a mixed- effects multiple linear regression modeling strategy. To facilitate Copyright © 2013 Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited. 74 JOEM  Volume 55, Number 1, January 2013