This 2002 study was conducted as a cooperative effort between
researchers at Iowa State University and the University of Iowa
Medical School at the request of the former governor of Iowa, Tom
Vilsack.
Five questions were presented to the researchers regarding the
impact of concentrated animal feeding operations (CAFOs) on public
health and environmental quality. This unique study involved medical
professionals, engineers, and environmental consultants and provides
an assessment and review of current scientific research.
This summary provides a brief overview of the answers relevant to
the environment for each question addressed by this research group.
For the full text of the researchers’ responses to the questions,
please refer to the complete “Iowa
CAFO Air Quality Study Report.”
Question 1 (2
Parts).
Based on
analysis of peer-reviewed, duplicated, legitimate, published
scientific research, is there direct evidence of harm to humans by
emissions, byproducts, toxic waste, or infectious agents produced by
C[A]FOs?
There is now an extensive literature documenting acute and
chronic respiratory diseases and dysfunction among workers,
especially swine and poultry workers, from exposures to complex
mixtures of particulates, gases and vapors within CAFO units.
However, one cannot directly extrapolate occupational health
risks observed among workers inside CAFOs to community health
risks that may arise from CAFO emissions. While the discharge
of airborne particulates and gases/vapors from CAFOs and
manure handling clearly occur, the aerosols at the point
source differ from ambient exposures as they move downwind,
both in composition and in concentration.
What human research is there to
confirm the existence of disease and exactly what are the specific
chemical, bacterial, or aromatic causes of such
diseases?
Published, controlled studies of odor experienced by community
residents living in proximity to CAFOs are limited to two
studies in North Carolina and one in Iowa. The first North
Carolina study reported more negative mood states (tension,
depression, anger, reduced vigor, fatigue and confusion)
among those exposed to CAFO odor compared with control subjects.
The second North Carolina study reported increased symptoms
of headache, runny nose, sore throat, excessive coughing,
diarrhea, burning eyes and reduced quality of life measures
among community residents living in proximity to a swine
CAFO compared with rural residents not living in proximity
to livestock operations. The Iowa study found increases
in several symptom clusters, mainly eye and upper respiratory
symptoms, among those living within two miles of a swine
CAFO compared with rural residents living near minimal livestock
production. These studies are limited in size and scope,
did not make specific environmental exposure or odor measurements,
and are subject to recall bias.
[M]any experimental and epidemiological studies of non-CAFO
populations exposed to low concentrations of individual chemical
components of CAFO emissions, particularly hydrogen sulfide, ammonia
and endotoxin [have been conducted]. Because at least two of these
chemicals (hydrogen sulfide and ammonia) are found in CAFO
emissions…, these experimental and community exposure studies are
relevant to this question. Both the EPA and the Agency for Toxic
Substance and Disease Registry have recommended ambient exposure
limits for ammonia and hydrogen sulfide based on these studies.
It is concluded that no specific disease(s) per se among
community residents can be confirmed to arise from a specific
chemical, bacteria or aromatic cause. However, the findings
of the limited community studies of concentrated livestock
exposures are consistent with adverse health effects observed
in other experimental and epidemiological studies of some
specific chemicals (ammonia and hydrogen sulfide) known
to be components of CAFO air emissions. It is, therefore,
also concluded that CAFO air emissions may constitute a
public health hazard and that precautions should be taken
to minimize both specific chemical exposures (hydrogen sulfide
and ammonia) and mixed exposures (including odor) arising
from CAFOs.
Question
2.
Based on an
analysis of peer-reviewed, duplicated, legitimate, and published
scientific research, what specific substances, including aromatic
compounds, do you believe require regulatory action to protect the
public?
By consensus of the entire study group, the following substances
should be considered for regulatory action: (1) hydrogen sulfide;
(2) ammonia; and (3) odors. The justification for regulatory action
of these substances is based on our assessment of the scientific
literature, recommendations by pertinent federal agencies, and
review of regulations established in other states.
Question 3.
Based on an analysis
of peer-reviewed, duplicated, legitimate, and published scientific
research, what would you recommend as Iowa or National consensus
standards for any proposed substances to be regulated as emissions
from CFOs?
The study group recommends that ambient air quality standards be
developed to regulate the concentration of hydrogen sulfide, ammonia
and odor.
The study group reached consensus that measurements for hydrogen
sulfide and ammonia should be taken at the CAFO property line and
residence or public use area. Measurements for odor should be taken
at a residence or public use area and one proposal includes
measurements at the CAFO property line. The study group recommends
that measurements for hydrogen sulfide and ammonia should be time
weighted rather that instantaneous to allow for atmospheric
variability.
[I]t is also recommended that provisions be made for allowable
times to exceed the established standards to allow for proper manure
application to land.
(For specific recommendations of exposure limits for gaseous and
odor emissions, see the full
report.)
Question 4.
What do you think should be done to address any other emerging
issues with respect to industrial C[A]FOs in Iowa?
Study group members reached consensus that as operations
become more numerous and concentrated on limited land bases,
there is an increased risk for deterioration of water quality.
All members believe that if producers do not follow their
manure management plans, the chance for runoff of nutrients
and bacteria is increased.
Wastes that are stored in lagoons or earthen waste storage
structures have a potential for spills and/or groundwater
contamination if existing standards are not met.
Various studies have demonstrated that continued use of
antibiotics in feedstuffs provides conditions favorable
to the selection of resistant strains of bacteria in food
animals and their environment. Yet the threats for emergence
of resistant strains of bacteria through subtherapeutic
use of antibiotics in livestock applies wherever these practices
occur; the threat is not restricted to CAFOs.
Regarding air pollution, air permits are not required for
emissions from CAFOs, so there is not a good method to quantify
their inputs. However, emissions of particulate matter,
sulfur compounds, and nitrogen oxides are believed to be
a very minor portion of Iowa’s total emissions. CAFO emissions
of these pollutants are small compared to emissions from
stationary sources (power plants and industry) and mobile
sources (automobiles and truck diesel). Greenhouse gas emissions
from CAFOs are significant for methane.
Question 5.
Finally, I am seeking your recommendations regarding available
methods of reducing or minimizing the emissions from CFOs
and the impact of those emissions on the ambient air surrounding
sites.
Emissions from CAFOs originate from three primary sources:
(1) air emissions from housing units; (2) air emissions
from manure storage facilities, and (3) air emissions during
and following land application events. Documented emission
reduction strategies exist for all three of these sources.
Some of the documented strategies are more effective than
others and some are more economical than others, however,
economical strategies exist for dealing with emissions from
all three sources.
From the Executive Summary of
the Iowa CAFO Air Quality Study:
