A new study released in the journal Environmental Science and Technology is the second to highlight that manure used to fertilize farm fields may reduce the health of fish living in adjacent streams.
In the U.S., most of our meat hails from concentrated animal feeding operations, sometimes known as CAFOs, which are commonly called factory farms. Thousands of animals are raised in small spaces that, in the EPA’s own definition, “substitute structures and equipment for land and labor.” As you might suspect, factory farms generate a lot of animal waste.
Some of this waste has been given the green light to be applied to land as inexpensive agricultural fertilizer. Its use requires some preventative measures to minimize runoff from farm fields into nearby waterways.
But when Purdue University researchers looked at two central Indiana ditches receiving drainage from fields that used factory farm manure, they found, when compared to an unexposed stream, fish had lower diversity and reduced reproductive capacity. And animal hormones were ubiquitous in the water.
80% of water samples taken at the ditches contained testosterone — with peak levels occurring in the spring, when many fish spawn. No testosterone was found in the control stream. And when fathead minnow embryos were reared in water taken from the ditches, their sex-ratio was skewed, with 60% turning out male.
The natural and synthetic hormones in factory farm manure appear to be having a gender-bending impact on fish. We will need more research to look at long-term reproductive implications. But simply spreading manure on the land may be too simple as a solution.
Web Links
Scientific American
EPA Land Application of Manure
http://www.epa.gov/npdes/pubs/cafo_permitmanual_chapter6.pdf
Environmental Science and Technology
http://www.environmentalhealthnews.org/ehs/news/2012/leet-estes302599t.pdf
Photo, taken on April 30, 2005, courtesy of Friends of Family Farmers via Flickr.
Earth Wise is a production of WAMC Northeast Public Radio. Support for Earth Wise comes from the Cary Institute of Ecosystem Studies in Millbrook, NY, with partial support from the Field Day Foundation.