Animal agriculture has become concentrated in many parts of the country with multiple operations in an area; each feeding large numbers of livestock, according to Wendy Powers and associates, Michigan State University Extension. With this consolidation has come concern over human health impacts of exposures to odors and gases associated with livestock production, including manure storage and land application of manure to croplands.
A number of studies have considered the impact on human health of living near animal-feeding operations. In the 1990s, Susan Schiffman, then a professor at Duke University , conducted studies that showed people who lived near large swine farms in North Carolina self-reported increased incidence of headaches, depression, nausea and vomiting as a result of exposure to odors from swine operations.
More recently, a study conducted by Stacy Sneeringer at Wellesley College  showed that infant mortality increased in communities as livestock inventories increased, based on data available from public health sources and agricultural statistics.
Such findings have spurred further investigation to elucidate if these findings are supported by health evaluations and further scrutiny of data. A group of scientists from around the United States reviewed findings from over 4,500 studies reporting the respiratory, gastrointestinal and mental health outcomes measured directly on human subjects in order to determine if there was an association between the health measures and the livestock operations. No conclusive association was determined, but proximity and livestock density were not included in the studies reviewed.
A group of scientists at Michigan State University  are considering these factors in their own work. This group is using state and national animal data and human health data to establish the relationships between proximity to livestock and livestock density with infant mortality in Michigan and replicate the earlier findings of Sneeringer.
Roy Black, Karen Chou and Melissa Millerick-May, faculty at Michigan State University, will explore this topic more and share their own research findings at the Michigan State University Extension  Communities and Livestock meeting  April 23, 2013, in East Lansing, MI. The conference will be held at the Diagnostic Center for Population and Animal Health  on the Michigan State University campus. Online registration  is available. The registration fee is $85, which covers all materials, refreshments and lunch.