Relative exposure to swine animal feeding operations and childhood asthma prevalence in an agricultural cohort

Large swine animal feeding operations (AFOs) have become the model of livestock production throughout the United States. Epidemiological studies have consistently shown an increase in adverse respiratory symptoms among workers at AFOs. However, the impact on communities surrounding these facilities is still being investigated. We evaluated the association between relative environmental exposure to AFOs and the prevalence of prescribed medication for wheeze and/or childhood asthma in rural Iowa.Demographic and health information on 565 children aged 0-17 was obtained from a previous population-based cohort study while data on the AFOs were collected from publically available tax records. We created a metric of each child's relative environmental exposure to swine CAFOs which incorporated the size of the AFO as well as distance and wind direction. We determined the association between self-reported prescription medication for wheeze and/or self-reported physician diagnosed asthma and relative exposure while controlling for recognized risk factors using correlated logistic regression.The prevalence of childhood asthma in the cohort was 11.0% while 22.7% of children had been previously prescribed medication for wheeze or had a lifetime asthma diagnosis. Children with a larger relative environmental exposure to AFOs had a significantly increased odds of both outcomes (OR=1.51, p=0.014 asthma; OR=1.38, p=0.023 asthma or medication for wheeze). When stratified into exposure quartiles a linear trend was observed with asthma or medication for wheeze as the dependent variable but not with asthma alone. This study is the first to investigate children's cumulative relative exposure to smaller AFOs and adds to the growing volume of literature supporting a link between proximity to swine AFOs and adverse respiratory health.