Literature Review of Contaminants in Livestock and Poultry Manure and Implications for Water Quality

This "Literature Review of Contaminants in Livestock and Poultry Manure and Implications for Water Quality" was prepared as part of the United States Environmental Protection Agency's (USEPA) ongoing efforts to better understand the environmental occurrence and potential effects related to contaminants of emerging concern. The report makes no policy or regulatory recommendations; it does identify information gaps that may help define research needs for USEPA and its federal, state and local partners to better understand these issues. Over the past 60 years the structure of American agriculture has significantly changed. Across all agricultural sectors, farm operations have expanded - farms have gotten larger and fewer in number. The shift from the "family farm" is perhaps most pronounced in the production of livestock and poultry. Food animal production has evolved from largely grazing animals and on-farm feed production to fewer and larger operations and increasingly more to concentrated facilities, often with animals raised in confinement. This has been done, in part, to meet the demands for meat and animal products from a growing human population in the U.S. and abroad. The increase in concentration of livestock and poultry also leads to increased concentration of animal manure that must be managed. Historically, manure was used as fertilizer on the farm to provide nutrients for plant growth on the cropland, pasture or rangeland that, in turn, partly provided the feed for the animals raised on the farm. Manure can also improve soil quality, when managed appropriately as a fertilizer, where the producer considers the right rate, timing, source, and method of application (NRC 1993). However, while livestock manure can be a resource, it can also degrade environmental quality, particularly surface and ground water if not managed appropriately. The geographic concentration of livestock and poultry can lead to concentrations of manure that may exceed the needs of the plants and the farmland where it was produced. Recognizing the potential for human and ecological health effects associated with the other contaminants in manure, this report focuses on the growing scientific information related to contaminants of emerging concern - particularly pathogens, antimicrobials, and hormones in manure - and reviews the potential and documented human health and ecological effects associated with these manure contaminants. Many other groups and initiatives are focusing on nutrient water quality issues, including the relative contributions of animal manure. This report briefly discusses the magnitude of manure generation (which is often highly localized) for perspective on the relationship to these emerging contaminants and their prevalence in the environment, for major livestock types - beef and dairy cattle, swine, poultry and aquaculture. This report is focused on manure and does not address other waste management issues related to livestock and poultry operations (e.g., disposal of dead animals, spoiled feed). The purpose of this report is to summarize publicly available literature for those involved with watershed protection and management and the linked efforts for source water protection and planning for drinking water systems. As noted in the report, there are very different levels of information available on many of these topics associated with manure. Hence, the report can also help to identify information gaps and guide research needs for the U.S. Environmental Protection Agency (USEPA) and other partners to better understand these issues.