Updated systematic review: associations between proximity to animal feeding operations and health of individuals in nearby communities
BACKGROUND Despite public concern about potential adverse health effects of concentrated animal feeding operations, objectively assessed data on environmental exposure to concentrated animal feeding operations and respiratory health are sparse. We aimed to assess respiratory health in neighbors of confined animal feeding operations. METHODS A survey was done in 2002-2004 among all adults (18-45 years old) living in 4 rural German towns with a high density of confined animal feeding operations. Questionnaire data were available for 6937 (68%) eligible subjects. In a random sample we measured the following outcomes: specific IgE to common and farm-specific allergens, lung function, and bronchial hyperresponsiveness to methacholine. Exposure was measured by collecting data on odor annoyance and geo-coded data on the number of animal houses within 500 m of the home. Locally optimal estimating and smoothing scatter plots were used to model the association between exposure and outcome. Analyses were restricted to subjects without private or professional contact with farming environments. RESULTS The prevalence of self-reported asthma symptoms and nasal allergies increased with self-reported odor annoyance. The number of animal houses was a predictor of self-reported wheeze and decreased forced expiratory volume in 1 second, but not allergic rhinitis or specific sensitization. Self-reported exposure and results of clinical measurements were poorly correlated. CONCLUSIONS Confined animal feeding operations may contribute to the burden of respiratory disease among their neighbors. Our findings underline the importance of objective assessment of exposure and outcome in environmental epidemiology.