A National Institute of Environmental Health Sciences Center of Excellence


2007 Midwest State Legislators Workshop

CAFO Publications

Environmental Impacts of Industrialized Livestock Production

In an ongoing effort to address the environmental concerns of rural residents in the U.S., the Environmental Health Sciences Research Center’s (EHSRC) Community Outreach and Education Core (COEC) has played a major role in translating the science of the EHSRC into policy through outreach to local, county, and state governments around the country as well as to stakeholder groups. The COEC has sponsored four conferences and workshops that have produced important state-of-the-art consensus documents. These have been used by state legislatures, state environmental protection commissions and the U.S. EPA to promulgate regulations and pursue enforcement actions. The EHSRC website has become a valuable resource for accessing the “Concentrated Animal Feeding Operations (CAFO) Air Quality Study”, a document which describes the environmental health impacts of modern livestock production methods. CAFO workshops organized by the COEC are described below.

In 1995 the EHSRC sponsored a two-day workshop entitled, “Understanding the Impacts of Large-Scale Swine Production.” This workshop addressed the occupational and environmental impacts of the expansion of vertically-integrated swine production technology.  Environmental health scientists from the United States and Canada participated and began to identify and address the complex scientific and policy issues. This workshop resulted in a 207-page proceedings document that identified emerging science and gaps in knowledge along with strategies to fill those gaps. The proceedings report was distributed widely to environmental groups, producer associations, and policy makers and began a dialog about the need to address the impacts of this type of agriculture.

The 1995 workshop put the EHSRC in the spotlight in the Midwest region for information on environmental health impacts of CAFOs. Thus, when NIEHS invited the EHSRC to host a Town Meeting we elected to focus on this highly contentious topic. On November 16, 2001, the EHSRC hosted “Concentrated Animal Feeding Operations: Airing the Environmental Health Issues. A Town Meeting.” Over 200 farmers, rural residents, scientists, and policy makers attended the all day meeting. The morning focused on scientific issues with presentations on changes in the structure of agriculture and rural life, the principal occupational and community health concerns, environmental contaminants from CAFOs, engineering control approaches, and the emerging issue of antibiotic resistant organisms. Dr. Ken Olden described the role of NIEHS in developing research to elucidate the relationship between environmental exposures and susceptibility factors leading to environmentally induced disease. A keynote address by Mr. Jeff Vonk, the Director of the Iowa Department of Natural Resources (IDNR), focused on the important role of rigorous science to guide us in addressing the problem of environmental pollution from CAFOs. He indicated that the IDNR needed stronger regulations governing the siting and operation of CAFOs. The afternoon included a panel discussion with six producers and rural residents representing divergent viewpoints and an extended open question and answer period. Questioners from the floor spoke of their damaged health and economic ruin that they attributed to large hog facilities moving into their communities. Others expressed concern that state and local government officials had been unable to help rural citizens by enforcing environmental regulations. Another topic of discussion was the concern that poor environmental quality and offensive odors pose significant health threats to both rural and urban residents.

In mid-June of 2001, Iowa Governor Tom Vilsack requested that a study group comprised of key faculty of The University of Iowa and Iowa State University address the public health and environmental impacts of concentrated animal feeding operations (CAFOs). James Merchant and Peter Thorne led the University of Iowa team and the EHSRC became the lead center for organizing faculty researchers and producing the final report. IDNR Director Jeff Vonk asked the study group to provide guidance regarding the impacts of air quality surrounding CAFOs on Iowans and recommended methods for reducing and/or minimizing emissions. Specifically, Director Vonk asked, “… what would you recommend as Iowa or National consensus standards for any proposed substances to be regulated as emissions from CAFOs?”

The study group submitted their 10-chapter 221-page report to Director Vonk on February 8 and recommended that the DNR develop ambient air quality standards to regulate air emissions from CAFOs. The report states that “emissions may constitute a public health hazard and that precautions should be taken to minimize . . . exposures arising from CAFOs.” The study group recommended specific air quality standards for regulating emissions of hydrogen sulfide, ammonia, and odors. The report documents that hydrogen sulfide and ammonia have been measured near livestock operations in concentrations that could be harmful to humans. Both substances are pulmonary irritants. Odors arising from CAFOs were reported to be associated with increased eye and respiratory symptoms by rural residents living near the facilities.

Besides air quality, the study group also was asked to address other emerging issues related to CAFOs. The report identified water quality, worker health, antibiotic resistance, greenhouse gas emissions, socioeconomic impacts on rural communities, and livestock epidemic and carcass disposal issues. The study group also outlined policy strategies to improve siting of new confinement facilities.  Finally, the study group reported on technologies and management strategies that are currently available to producers to reduce emissions. These included strategies related to housing ventilation, manure handling and storage.  The report, titled the Iowa Concentrated Animal Feeding Operation Air Quality Study (CAFO Air Quality Study), is available for download on the EHSRC’s web page.

News of the CAFO Air Quality Study was carried on television, radio and print media, especially in the Midwest, in February 2002.  EHSRC researchers, James Merchant, Peter Thorne, and Kelley Donham, officially presented the report to the Environmental Protection Commission on February 18th and to the Iowa House and Senate Agriculture and Environment Committees meeting in joint session on April 3. The Iowa Legislature passed and the Governor signed bill SF 2293 in May 2002. This is the first major change in Iowa animal agriculture law since 1995.  For the first time, air quality was specifically included as regulated substances for concentrated animal production permit holders.  At this time, the IDNR is proceeding to implement and monitor for the hydrogen sulfide and ammonia levels recommended by the study. Hearings have been held around the state on the standards and the defined procedures to measure these emissions.  EHSRC investigators have spoken at a number of these hearings. Importantly, other Midwestern states have considered policy actions and have used the CAFO Air Quality Study for supporting information.

The NIEHS-sponsored Town Meeting left several key issues inadequately addressed. Thus, the EHSRC applied for and received a supplemental award to host an international conference and workshop  entitled, “Environmental Health Impacts of CAFOs: Anticipating Hazards – Searching for Solutions.” This was held March 29-31, 2004 with an open conference on the first day and an invited workshop on the second two days. The conference was attended by over 200 people and featured speakers from the U.S., Canada, Sweden, Denmark and The Netherlands. Conference attendees included scientists, agricultural extension employees, producer group representatives, environmental activists, community activists, rural residents, and government officials. The Workshop on March 30 and 31 was very productive with 50 invited scientists covering all the major issues associated with livestock confinements and environmental health. Five working groups drafted state-of-the art reports which are now in preparation for publication. The working groups covered Respiratory Health Effects; Modeling and Monitoring of Air Toxics; Water Quality Issues; Influenza Pandemics, Infectious Diseases and Antibiotic Resistance; and Community Health and Socioeconomic Issues. Importantly, this conference demonstrated that viable solutions to many of the environmental health problems associated with livestock production exist and can be implemented economically. This conference also raised the specter of dangerous influenza pandemics arising in the U.S. from siting industrialized poultry and swine production in close proximity.

Public Health Significance

Through these conferences and workshops the EHSRC Community Outreach and Education Core has advanced the science and educated the public on an important rural environmental health issue. Recent legislative policy initiatives have drawn upon the expertise of EHSRC investigators for supporting scientific information.


  1. Donham KJ, Thu K, Jackson L, Melvin S, Lasley P, Thorne, PS, Hamilton ND. Understanding the Impacts of Large-Scale Swine Production: Proceedings from an Interdisciplinary Scientific Workshop, pp. 1-207, June 29-30, 1995.

  2. Merchant JA, Ross RF, Thorne PS, et al. Iowa Concentrated Animal Feeding Operations Air Quality Study, University of Iowa-Iowa State University Study Group, University of Iowa Environmental Health Sciences Research Center, pp. 1-221, Feb 8, 2002.

  3. Environmental Health Impacts of Concentrated Animal Feeding Operations (CAFOs). Environmental Health Perspectives Mini-Monograph Series, 115(2):296-320, 2007.
  Entire Publication Series  
  Environmental Health Impacts of Concentrated Animal Feeding Operations (CAFOs)  
  Individual Publications  
  Environmental Health Impacts of CAFOs (Introduction to the series)  
  Health Effects of Airborne Exposures from CAFOs  
  Monitoring and Modeling of Emissions from CAFOs  
  Impacts of Waste from CAFOs on Water Quality  
  The Potential Role of CAFOs in Infectious Disease Epidemics and Antibiotic Resistance  
  Community Health and Socioeconomic Issues Surrounding CAFOs  

  Environmental Health Sciences Research Center, The University of Iowa, University Research Park, #178 IREH, Iowa City, IA 52242

Tel: (319) 335-4756 / Fax: (319) 335-4225 / E-mail: nancy-wyland@uiowa.edu