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:
http://www.oehha.ca.gov/air/acute_rels/pdf/7783064A.pdf.
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:
http://www.iowadnr.com/air/afo/afo.html.
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.
