Analysis on Airborne Bacteria Suppressed

Published Feb 18, 2005

NOTE: The following is one of a series of case studies produced by the Union of Concerned Scientists' Scientific Integrity Program between 2004 and 2010 to document the abuses highlighted in our 2004 report, Scientific Integrity in Policy Making.

Dr. James Zahn, a research microbiologist at the U.S. Department of Agriculture (USDA), asserted that he was prohibited on no fewer than 11 occasions from publicizing his research on the potential hazards to human health posed by airborne bacteria originating in farm wastes.1

Zahn’s research had discovered significant levels of antibiotic-resistant bacteria in the air near hog confinement operations in Iowa and Missouri.2 But he was repeatedly barred by his superiors from presenting his research at scientific conferences in 2002.3 In at least one instance, a message from a supervisor advised Zahn that “politically sensitive and controversial issues require discretion.”4

Zahn says USDA officials told him his work was being discouraged because it dealt with human health, an issue outside his unit’s mission.5 Yet the website for the research unit at the USDA where Zahn worked stated that its mission was “to solve critical problems in the swine production industry that impact production efficiency, environmental quality, and human health.”6

Dr. Alan DiSpirito, a microbiologist at Iowa State University who collaborated with Zahn on this research, claimed that Zahn was careful never to make unwarranted claims about the health effects of his research. As DiSpirito put it, Zahn’s “data concerned careful measurements of odor producing compounds. All the measurements were very straightforward.” According to DiSpirito, Zahn “found evidence of airborne toxic substances and antibiotics, which certainly raised health questions, but as a careful and very competent scientist, he never commented on these in his work except to suggest that someone else ought to look into them.”7

Zahn had accidentally stumbled on the issue of airborne antibiotic resistance while researching a related topic and, prior to the start of the Bush administration, was initially encouraged by his supervisors to pursue the work. But with the change in administration, he soon came to feel that his research was being suppressed because it was perceived to be politically unpalatable.

The suppression of Zahn’s research results was part of a larger pattern within the USDA of squelching findings that conflicted with the George W. Bush administration’s agenda. Notably, a directive issued in February 2002 instructed USDA staff scientists to seek prior approval before publishing any research or speaking publicly on “sensitive issues” including “agricultural practices with negative health and environmental consequences, e.g. global climate change; contamination of water by hazardous materials (nutrients, pesticides, and pathogens); animal feeding operations or crop production practices that negatively impact soil, water, or air quality.”8

Zahn, who has since left the USDA, offered a harsh critique of the agency. He contended that USDA officials censor controversial research by forcing it through an extended approval process, prevent researchers from publicizing sensitive findings in scientific journals and at public meetings, and cooperate with industry groups to suppress research results that don’t meet those groups’ satisfaction. In particular, he stated, the aforementioned directive represented “a choke hold on objective research” at the government agency.9

Note: This page is an excerpt from the 2004 UCS report Scientific Integrity in Policymaking.

1. Interview with James Zahn, January 2004, for UCS Scientific Integrity report. See also P. Beeman, “Ag Scientists Feel the Heat,” Des Moines Register, December 1, 2002. Online at

2. B. Harder, “Antibiotics fed to animals drift in air,” Science News, July 5, 2003. (The article reports on Zahn’s research.)

3. Among these was his request to present a paper at an international joint meeting of the American Society for Agricultural Engineering and the 15th World Congress of CIGR (Commission Internationale du Genie Rural), Chicago, July 28-31, 2002.

4. J. Lee, “Neighbors of Vast Hog Farms Say Foul Air Endangers Their Health,” New York Times, May 11, 2003.

5. Author interview with James Zahn, January 2004.

6. “USDA Agricultural Research Service Swine Odor and Manure Management Research Unit,” USDA. Online at

7. Interview with Alan DiSpirito, March 2004, for UCS Scientific Integrity report.

8. “Lists of Sensitive Issues for ARS Manuscript Review and Approval by National Program Staff—February 2002 (revised),” USDA, February 2002.

9. Interview with James Zahn, January 2004, Op. cit.

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