Respiratory health in dairy workers: findings from the Healthy Dairy Workers longitudinal study in Yakima, WA

Abstract

Poor air quality and respiratory disease are important occupational health problems. Dairy farm workers are known to have high levels of exposure to endotoxin, bioaerosols, dust, and other respiratory irritants. Previous work has focused on cross-sectional measurements of dairy worker respiratory health, and additional analysis of the long-term effects of dairy work is needed. We evaluated 50 dairy workers and 40 community controls from the Yakima Valley in Washington between 2017 and 2022. Dairy workers were recruited by study staff from 3 large dairies. Community controls were enrolled from community contacts without dairy work and then via snowball sampling, and were oversampled for male and Hispanic individuals. Participants had up to 5 study visits; each visit involved a questionnaire and spirometry measurements. We fit a linear mixed effects model to investigate the association between dairy work and respiratory function (measured as FEV1 as % predicted), adjusting for smoking status and body mass index. Additionally, effect modification was evaluated for growing up on a farm (a proxy for the protective “farm effect” of early life farm exposure contributing to decreased prevalence of allergic respiratory disease) and work in the milking parlor for dairy workers (a proxy for the harmful effects of higher concentrations of respiratory irritants in indoor air). Our results showed no evidence of association between dairy work and respiratory function decline over time, and no evidence of effect modification for growing up on a farm or work within the milking parlor. These findings suggest that dairy work did not appear to contribute to short-term occupational lung function decline in our cohort, though the healthy worker effect and limited period of follow-up may attenuate findings. More work is needed to better understand the health status of this important occupational group.