Odor and Nutrient Management Newsletter

Summer 2004

DNR proposes airborne hydrogen sulfide level

by Bryan Bunton, Iowa Department of Natural Resources

The Iowa Department of Natural Resources (DNR) is proposing a rule to establish health standards for airborne levels of hydrogen sulfide gas. The proposed health effects standard for hydrogen sulfide gas is 30 parts per billion (ppb), daily maximum one-hour average, not to be exceeded more than seven times per year as measured at residences, churches, schools or other public use areas near animal feeding operations. The rule is scheduled for final adoption at the July 19 meeting of the Iowa Environmental Protection Commission. The meeting is open to the public.

The health standard is being proposed to compare against monitored levels of hydrogen sulfide gathered as part of a legislatively mandated field study that requires the DNR to measure levels of ammonia, hydrogen sulfide and odors near some of the largest animal feeding operations in Iowa. The health standard will be the “bar” used to compare against this monitoring data.
Because of the tremendous interest in this issue, the DNR recently conducted six public hearings around the state. As a result, almost 3,000 comments from livestock producers, those living in the vicinity of livestock operations, agricultural commodity groups, environmental organizations and concerned citizens were gathered. This is nearly twice the number of comments that the Environmental Protection Agency recently received on a proposed rule that applied nationwide.

Based on public comments and recommendations from the Iowa Department of Public Health, DNR staff will be proposing a level of 30 ppb over one-hour to the EPC, who then must make the final decision on the level of the standard. The DNR initially proposed a level of 15 ppb.
The Iowa Department of Public Health has identified several research articles that support the level of 30 ppb. These include a study completed in northeastern Nebraska where an association was made between visits to the hospital due to respiratory issues and exposure to ambient levels of hydrogen sulfide greater than 30 ppb measured on thirty-minute averages. In addition, a study of air pollution in Finland found an association between people reporting more incidences of headaches, depression, tiredness and nausea when exposed to levels of hydrogen sulfide greater than 28 ppb.

A proposed level of 30 ppb over one-hour is also supported by data from the state of California. The magnitude and duration of the standard are identical to the California ambient air quality standard (CAAS) for hydrogen sulfide. The CAAS standard for hydrogen sulfide has been in place since 1969. The March 1999 evaluation of the public health data by the California Office of Environmental Health Hazard Assessment underlying the standard is available at:


In addition to adjusting the proposed hydrogen sulfide level to 30 ppb, the department has proposed several other modifications to the rule that can be viewed by visiting the Air Quality Bureau’s animal feeding operations Web page located at:


The department also has developed a responsiveness summary that contains a written response to all public comments received. The summary explains the department’s rationale and logic behind any modifications that were made to the proposed rule, or discusses why no such changes were made. The response to comments is available to the public and has been posted on the Air Quality Bureau’s Web page.

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Iowa Manure Matters: Odor and Nutrient Management is published by Iowa State University Extension, with funding support from the USDA Natural Resource Conservation Service through Cooperative Agreement No. 74-6114-8-22. To subscribe or change the address of a current subscription, write to Angela Rieck-Hinz, 2104 Agronomy Hall, Iowa State University, Ames, Iowa, 50011-1010 or call 515-294-9590, fax 515-294-9985 or email: amrieck@iastate.edu. Please indicate you are inquiring about the Odor and Nutrient Management Newsletter. The newsletter's coordinators are Angela Rieck-Hinz, extension program specialist, Department of Agronomy, Wendy Powers, environmental extension specialist, Department of Animal Science, and Robert Burns, Department of Agricultural and Biosystems Engineering; the editor is Jean McGuire, the subscription manager is Rachel Klein, the production designer is Beth Kroeschell, and the web page designer is Liisa Jarvinen.

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