Industrial Animal Agriculture in the Yakima Valley, Air Pollution, and Pediatric Asthma Morbidity

Abstract

Background: Elevated rates of pediatric asthma morbidity have been observed in some regions of the rural United States; however, the potential links between asthma exacerbations and environmental exposures common to rural settings are largely unexplored in the research literature. The growth of industrial-scale agriculture has degraded outdoor air quality in many rural communities including by emissions of large animal feeding operations (AFOs). Methods: We conducted a longitudinal, repeated measures study of community-level AFO exposures and pediatric asthma morbidity in the Yakima Valley, an agricultural region of Washington State. Our cohort consisted of school-aged children with preexisting asthma (n=58) participating in the Aggravating Factors of Asthma in a Rural Environment (AFARE) study, a community-based participatory research project. Over a 26 month period, subjects' respiratory health was assessed on a biweekly basis using the Asthma Control Questionnaire (ACQ), a survey of asthma symptom severity and "rescue" medication use, and daily home spirometry, which provided measurements of forced expiratory volume in one second (FEV1). Three outdoor air exposures related to AFO pollution were investigated in separate analyses: regional particulate matter of 2.5 µm or less in aerodynamic diameter (PM2.5); ammonia, repeatedly measured at 18 residential sites across the study area; and a novel metric of AFO airborne "plume" exposure, calculated using proximity and size of nearby AFOs as well as daily wind conditions. Results: We found that on average, children in the AFARE cohort experienced decrements in FEV1% one to two days following elevated exposure to PM2.5, ammonia, and AFO plumes. In addition, elevated PM2.5 was associated with increased symptom severity and medication usage as reported on the ACQ. No statistically significant associations between ACQ results and ammonia or AFO plume exposure were observed, however. Conclusions: Our findings indicate that children with asthma may experience short-term respiratory effects following increased exposure to airborne AFO pollutants, adding to a growing body of research evidence that AFO-related air pollution may cause community-level health effects. To our knowledge, our work represents the first analyses of time-varying changes in respiratory health for children with asthma, a vulnerable subgroup of rural populations. Additional research to confirm these findings in oterh study populations is warranted.