#3 Agreement to accept deer carcasses at landfill
DEPARTMENT OF PUBLIC WORKS MEMORANDUM
December 4, 2009
TO: City Council
FROM: John Whitcomb, Operations Director
SUBJECT: Proposed Indemnification Agreements with Wisconsin Department
of Natural Resources
Summary
This memo provides information regarding proposed indemnification agreements
with the Wisconsin Department of Natural Resources (WDNR) pertaining to the
landfill disposal of deer carcasses possibly affected with chronic wasting disease
(CWD). The indemnification agreements cover disposal operations at the City’s
landfill and treatment of landfill leachate at the City’s wastewater treatment
facility. The issues relative to deer carcass disposal at the landfill were reviewed
by the Sustainable Janesville Committee at their meetings on November 17 and
December 1, 2009. At their meeting on December 1, 2009, the committee
recommended that the City Council authorize the City Manager to enter into the
proposed agreements on a 4-3 vote.
Staff Recommendation
Given the available information, including the UW study on prion behavior in
landfills and that CWD has not been shown to be transmissible to humans, staff
believes continuing to accept deer carcasses for disposal at the landfill presents
a low level of environmental and human health risk. Further, in the absence of a
landfill disposal option, meat processors and residents processing their own deer
have no other appropriate disposal options which would likely lead to
indiscriminate dumping of carcasses and renderings.
Therefore, following Council discussion, staff recommends the City Council
authorize the Administration to enter into both the landfill and wastewater
treatment facility indemnification agreements with the WDNR.
Recommended Motion
I move to authorize the Administration to enter into the proposed indemnification
agreements as recommended by staff.
City Manager Recommendation
The City Manager concurs with the staff and Sustainability Committee
recommendation based on the information provided by the WDNR.
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Background
CWD is a fatal nervous system disease known to naturally infect whitetail deer
and other specific cervid populations. CWD belongs to a family of nervous
system diseases known as transmissible spongiform encephalopothies (TSE) or
prion diseases. It has common features with other prion diseases, like mad cow
disease in cattle, scrapie in sheep, and Creutzfeldt-Jakob Disease in humans.
However, CWD is distinct and known only to infect specific members of the deer
family. Like scrapie in sheep, there is no evidence showing CWD in deer is
transmissible to humans. This is unlike mad cow disease which has been shown
to be transmissible to humans under specific circumstances. Given the
extensive amount of information available through DNR about CWD, those
wishing additional information should visit the DNR’s website at:
http://dnr.wi.gov/org/land/wildlife/whealth/issues/CWD/
One of the issues which has arisen as a result of the discovery of CWD regards
questions about the proper disposal of deer carcasses. Only chemical digestion
and high temperature incineration will actually destroy the prions which cause all
manifestations of TSE. However, these methods are costly and not practical at
this time given the numbers of carcasses and renderings available for disposal
on an annual basis.
Some landfills have stopped accepting deer carcasses for disposal, for various
reasons, but primarily over concern about potential future regulation of the prions
causing CWD, not necessarily health-related concerns. Some of these landfills
had to stop accepting deer carcasses because the wastewater treatment facilities
treating their leachate required the landfills stop accepting deer carcasses.
These wastewater treatment facilities had similar concerns over potential future
regulation of prions. The City has continued to accept deer carcasses from
residents and current customers for disposal at its landfill, adopting special
handling and disposal procedures recommended by WDNR and the U.S.
Environmental Protection Agency.
The University of Wisconsin, a leader in CWD and prion research, conducted a
study to specifically determine how prions would behave in the landfill
environment. The study concluded that landfill disposal of carcasses and
renderings affected with CWD presents a very low-level risk of potential future
exposure to the prions causing CWD, either within the landfill or via leachate that
exits the landfill and is treated at a wastewater treatment facility. This study has
been used by agencies in other states in developing their carcass disposal
policies. All other states currently dealing with this issue recommend landfill
disposal, as does the EPA.
In response to the limited landfill disposal options currently available, DNR has
developed indemnification agreements for landfills willing to accommodate deer
carcass disposal and for wastewater facilities treating leachate from these
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landfills. Under these agreements, the WDNR indemnifies landfills and treatment
facilities from future liability directly related to the disposal of CWD affected deer
carcasses, provided certain conditions are met. The City Attorney has reviewed
and approved the proposed indemnification agreements.
On a final note, the City’s wastewater treatment plant staff has indicated they will
continue to allow landfill disposal of deer carcasses on condition the Council
authorizes, at a minimum, the proposed wastewater treatment plant
indemnification agreement. Without this indemnification agreement, the landfill
will be unable to continue to accept deer carcasses.
The issues relative to deer carcass disposal were reviewed by the Sustainable
Janesville Committee at their meetings on November 17 and December 1, 2009.
At their meeting on December 1, 2009, the committee recommended that the
City Council authorize the City Manager to enter into the proposed agreements
on a 4-3 vote.
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An Analysis of Risks Associated with the Disposal of Deer from Wisconsin in
Municipal Solid Waste Landfills
1.Background
The purpose of this document is to evaluate risks associated with the landfilling of CWD-infected
deer carcasses. It uses the current scientific information available on this subject and, as such, should
be considered an interim document that will be updated as new information is available.
1.1 The Challenge
In February 2002 the first cases of chronic wasting disease (CWD) in free-ranging white-tailed deer
east of the Mississippi River were reported in southwest Wisconsin. Further surveillance revealed a
3% rate of infection in an 11-mile radius around the initial cases. Based on these findings and the
input of wildlife disease control and CWD experts, a disease eradication program was developed.
This program calls for the harvest of all of the deer within a 360 square mile area and for population
reductions in the surrounding areas.
The zone targeted for complete depopulation has been designated the eradication zone (EZ) and the
surrounding area has been termed the management zone. It is estimated that, as of fall of 2002, there
are approximately 25,000 deer in the EZ alone. Citizen-hunters are expected to be the primary means
of removing deer from the EZ. It is expected that the majority of these deer will not be used as a
source of venison. Therefore, the carcasses will need to be disposed of in a manner that does not
jeopardize animal or human health or environmental quality.
Any disposal method must also have the following attributes: the capacity to handle a large number
of carcasses; the ability to conform to local, state and national laws and regulations; and to be in place
by October 2002. A final consideration is the cost of disposal. Although the latter is not the primary
consideration, it is likely that disposal costs will be one of the largest expenses of Wisconsin’s CWD
control program. The four primary options currently under consideration for the disposal of deer are
landfilling, rendering, incineration and chemical digestion.
Deer carcasses and tissues are often sent to municipal solid waste landfills. This material is
incorporated in with other waste at the landfill. Landfills generate a certain amount of liquid, termed
leachate, which is collected and processed. This leachate results primarily from precipitation falling
on the landfill surface. Composite landfill liners prevent leachate from entering groundwater. The
leachate is collected at the base of the waste just above the liner. In most instances the leachate is
transferred to a wastewater treatment plant (WWTP) for treatment. Less commonly, some landfills
may recirculate a portion of the leachate. At the WWTP, the leachate is processed along other
wastewater. Solids are separated from the water portion. This material, termed “sludge” or biosolids,
is commonly applied on farm fields or landfilled.
Based on the above, the primary pathway of potential risk identified for the CWD prion following
landfill disposal of infected deer can be described as:
?????
carcasslandfill leachatewastewater treatment plantsludge
?
farm fieldingestion by humans or deer.
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1.2 The Disease
CWD is a member of the transmissible spongiform encephalopathies (TSEs) a group of diseases that
includes scrapie of sheep, bovine spongiform encephalopathy (BSE) of cattle and Creutzfeldt-Jakob
Disease of humans. BSE is the only animal TSE for which there is experimental and epidemiological
evidence of transmission to humans (Bruce et al. 1997, Hill et al. 1997 and Scott et al. 1999). All of
the diseases in this group are characterized by a prolonged incubation, insidious onset of neurological
signs, typically slow progression and eventual death. As a group, the TSEs are infectious, but not
highly contagious. The specific transmission routes (i.e. portal(s) of agent exit and entry) of CWD
between infected and susceptible animals have not been established. There is evidence that CWD
can be transmitted by direct and indirect means; that is by animal-to-animal contact or by animal
contact with contaminated items or the environment.
1.3Biochemical and Physical Properties of the TSEs
Biochemically, the TSEs are characterized by a resistant form of a normal protein that is found in all
mammalian and avian species examined to date. This protein is termed prion protein (PrP). The
abnormal form, termed PrP-res, is associated with TSE infectivity and pathogenicity. The “res”
refers to the fact that the abnormal prion protein is partially resistant to proteinase K digestion.
Unlike the normal host prion protein, PrP-res forms ordered oligomeric structures; which are units
composed of more than one protein chain. PrP-res has both hydrophilic and hydrophobic regions
(Meyer et al. 1986). The hydrophobic region will be an important determinant of the behavior of the
CWD agent in the landfill environment. Other distinctive properties of PrP-res include resistance to
many of the commonly used disinfectants and inactivation procedures that are typically used to
destroy infectious agents. Finally, there are multiple strains of TSE agents that have been identified,
even within a particular disease group. Research has shown that some strains are more resistant to
inactivation than others. With respect to CWD, it is unknown whether there are multiple strains and
what relative degree of resistance to inactivation CWD has with respect to some of the better
characterized TSE agents such as scrapie and BSE.
2. Behavior of the Prion Protein (PrP-res) in the Environment
2.1 Soil and Solid Waste
Due to the hydrophobic regions of the CWD PrP-res molecule, infectious prions in the environment
can be expected to adsorb to organic material and soil. Initially the infectious agent is likely to
adhere to the protein and carbohydrate components of the animal carcass. As the carcass
decomposes, the undegraded PrP-res will adhere to adjacent soil or waste material in a landfill. The
ability of scrapie prions to bind to metals and plastics has been reported (Flechsig et al, 2001;
Weissman et al., 2002). All municipal solid waste landfills in Wisconsin employ a thick plastic
membrane (generally polyethylene) as a component of the liner. This liner acts as a protective barrier
and should prevent the movement of 'free' prions to subsurface soils or to groundwater.
In the only experiment to examine the fate of PrP-res in an outdoor environment, Brown and
Gajdusek (1991) buried perforated petri dishes containing hamster scrapie in a residential garden for
three years. They found that approximately 1% of the original infectivity in the original location
survived this term. Examining surrounding soil layers, no infectivity was found above the original
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location, a small amount of infectivity was found in the 4 cm soil layer that was directly beneath the
perforated dish containing the original inoculum and no infectivity was found at 4-8 cm below the
dish. The authors conclude that the hamster scrapie agent used in this experiment can persist in
contaminated soil for three years under natural environmental conditions, but that there is little
leaching to surrounding soil layers. To date there has been no further work that specifically examines
the fate of TSE agents in the soil/solid waste environment.
Land application of municipal sludge that potentially contains CWD PrP-res may result in the
presence of CWD PrP-res in surface soils. The application rates of municipal sludge are dependent
on the chemical characteristics of the sludge and therefore will vary. The mechanism and time
course of PrP-res degradation in soil/solid waste environment is unknown. Normal biodegredation
processes are expected to inactivate the CWD prion over time.
2.2 Water
The hydrophobic nature of PrP-res (Bennett 1992) indicates that leaching of the CWD agent into an
aqueous environment is unlikely to occur in the landfill or in soil. This assumption is echoed in a
2000 BSE risk assessment produced for the British Ministry of Agriculture, Fisheries and Food (now
Department for Environment, Food & Rural Affairs [DEFRA]). In section 3.1 titled “Fundamental
Assumptions” it states that “BSE agent is stuck to particulate matter and, hence, is removed with the
particulate matter from the effluent.” Gale et al. (1998) in examining the risk from BSE in the aquatic
environment state, “With the possible exception of flows in the vicinity of extraction wells, the rate
of flow through landfilled wastes is generally slow and non-turbulent, with the result that particulate
material is unlikely to be taken up in suspension.”
Should any PrP-res exit the landfill as part of the leachate, it will, due to its hydrophobic nature, be
attached to particulates (colloids) suspended in the leachate. Once that leachate reaches the
wastewater treatment plant the suspended solids will be separated from the effluent. Those
suspended solids will then be termed “sludge” or biosolids. Again, due to its hydrophobic nature, the
PrP-res is expected to selectively partition with the solids into the sludge portion, and is not expected
to be present in wastewater discharged to surface water. Gale and Stanfield (2001) discuss this
expectation in their risk assessment for BSE in sewage sludge.
2.3 Air
Air transport is not considered in this document because there is currently no evidence that PrP-res
can be released into the air or volatilized in any way under natural conditions. In addition, there is no
evidence of airborne transmission between animals or people.
3. Human vs. Animal Exposure to the CWD Agent
To date, no human illness has been associated with exposure to the CWD agent. However,
systematic surveillance has only recently begun. Given that humans have likely been exposed to the
CWD agent for decades from animals, in laboratories and from the environment, this is a significant
observation. Surveillance of prion-related diseases in humans is in its infancy. The primary routes of
exposure in the future are likely to be through hunting and the consumption of CWD-contaminated
venison and elk. To date, test-tube experiments in which normal human prion protein is exposed to
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PrP-res from white-tailed deer have shown a limited degree of infectivity, but at a less efficient rate
than that for BSE or scrapie (Raymond et al., 2000).
In contrast to interspecies transmission of CWD from deer to humans, there is good evidence that
deer and elk can contract CWD by animal-to-animal contact as well as by contact of a susceptible
animal with a contaminated environment.
Domestic cattle have failed to develop disease when housed with CWD-infected deer (Williams &
Miller 2002). Under experimental conditions, however, 3 of 13 cattle inoculated (~ 5 years ago)
intracerebrally with CWD did succumb to a TSE illness (Hamir et al., 2001). The remaining cattle
are still alive and will remain under observation for another 5 years. Animals orally inoculated have,
to date, not succumbed to the disease (Williams, 2002). Based on the above observations, the
following pathway is not considered further in this document:
??????
deerlandfillleachate wastewater treatment plantsludge farm field
??
animal fodder (surface contamination)domestic livestockcommercial meat.
4. Impact Assessment
4.1 Minimum Level of Exposure Known to Cause Disease
As described above, it is likely that over the past several decades, thousands of hunters, taxidermists,
meat processors, and research staff have ingested the CWD prion, as well as been exposed via eye
splashes and through cuts and wounds. Exposure from these routes is likely to have been
significantly greater than any that would be expected to result from contact with leachate from a well-
managed landfill.
The issue of how much infected material an individual (human or animal) must consume or be
exposed to in order to become infected with CWD or any other TSE is not known
. Neither is it
known if repeated small doses can result in infection. In an experimental setting, low-dose
inoculation studies have revealed a decreased probability of infection and prolonged incubation
periods. In some animal experiments, the incubation period extended beyond the natural life span of
the animal; that is, at the time of death due to “natural causes”, the animal was infected with the TSE
agent, but was not symptomatic (Dickinson, 1977; Thackray et al., 2002).
4.2 Transmission of TSEs to Humans and Among Animals of the Same Species
As stated in section 2., the only animal TSE that is known to have been transmitted to humans is
BSE. Transmission of TSEs from one animal to another is likely to depend on a number of factors.
These include the specific TSE, the strain of the TSE, the dose, the route of exposure, the human PrP
genotype, and likely other unidentified factors.
”
The dose for any TSE is typically expressed as a “infectious/lethal dose 50” or an “I/LDper gram
50
of tissue. It represents the dose of material at which 50% of the recipients become infected and will
die. An I/LDis always species and route specific. The I/LD is determined by serial dilutions of
50 50
the original material and subsequent inoculations into groups of animals to determine the endpoint at
which 50% of the animals succumb or are diagnosed as infected (The term “LD” is often replaced
50
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by “ID” or “infectious dose 50” to indicate that experimental animals are not allowed to progress
50
fully through clinical disease to death). For the TSEs, a lower dose can decrease the likelihood that an
exposed animal will become infected.
The route of exposure is also an important factor. The intracerebral route of inoculation is the most
efficient. However, it is not a natural route of exposure. The following additional routes of infection
are listed in descending order of efficiency (generally): intravenous, intraperitoneal and oral. The oral
infectious dose of CWD has not been determined for deer or elk (E. Williams, personal
communication, 2002).
4.3 Movement of Prions to Landfill Leachate
While the assumptions in this analysis are based on limited data, they serve to provide an
approximation of the range of conditions likely to be encountered in the environment under the
scenario described in this document.
4.3.1 Permeability
Permeability is defined as the time needed for liquids to percolate through the waste mass at a
landfill. There are limited data available regarding the saturated hydraulic conductivity of municipal
waste. The EPA Hydrologic Evaluation of Landfill Performance (HELP) model for predicting the
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movement of liquids through landfill caps and liners uses a default value of 1 x 10 cm/sec for the
saturated hydraulic conductivity of municipal waste. This value is based on work by Oweis et al
(1990). More recent data (Shaw and Carey, 1996, Bleiker et al,1993;Townsend et al,1995) indicates a
-3-6
broader range of permeabilities from 10 to 10 cm/sec. Permeability, however, can vary based on
waste composition, age (degree of decomposition) and depth of fill.
4.3.2 Distance to the Leachate Collection System
Typical municipal waste landfills in Wisconsin range in final height from 100 to 300 feet above the
leachate collection system. The landfills are typically constructed in a series of phases over time, so
that there are disposal areas available in the upper portions of the previous phase, while filling is
occurring at the base of a new phase. DNR recommended in a June 6, 2002 letter to landfill operators
that the deer carcass burial area should be “strategically sited high in the landfill such that any liquids
will have to pass through many feet of waste material before reaching the leachate collection
system”(WDNR, 2002).
4.3.3 Summary
Considering these factors in tandem with the observations in section 2.1 about the hydrophobicity of
prions and their tendency to degrade in soil, it is expected that if prions were to move into landfill
leachate, their movement would be slow enough that their concentration would be significantly
reduced by degradation and retention in the remaining waste mass.
4.4 Ingestion of potentially CWD-contaminated soil by humans and deer after sludge
application
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As described in section 2 of this document, it is expected that any prions present in leachate will
adhere to sludge during the wastewater treatment process. Furthermore, the incorporation of sludge
into the 9-inch plow layer, which is standard for land application practices, would provide significant
dilution within the soil. This combination of concentration reduction factors at the landfill, the
sewerage treatment plant, and in the soil as well as the natural degradation processes is expected to
greatly reduce the potential for infectious CWD prions to be present in sludge-amended soil.
5.Discussion
A quantitative or semi-quantitative assessment of the risk is not possible because the amount of
infectivity present in a carcass is unknown. In addition, the dose needed to infect a human or deer is
also unknown. Nonetheless, existing information suggests that landfilling large numbers of deer
from an area with a low incidence of CWD is unlikely to pose a significant risk to humans or to
wildlife.
This document provides support for the following conclusions:
1.The disease specific agent is hydrophobic and is expected to adhere to organic
materials present in a landfill.
2.It is likely to take the CWD agent several months to move through a landfill. During
that time the agent will be subject to biodegredation and is likely to lose a significant
amount of its infectivity. Based on the findings of Brown and Gajdusek (1991), up to
98% loss of infectivity can be anticipated within a 3-yr period.
3.Any infectivity that exits the landfill will be captured in the effluent and transferred to
a wastewater treatment plant or recirculated in the landfill.
4.CWD prions present in wastewater are expected to partition with the sludge fraction.
5.Land-applied sludge will be greatly diluted by surface soils and incorporated with soil
at a depth of 9 inches.
5.1 Likelihood of Human Exposure
Two factors strongly influence human risk:
1.The presence of a species barrier
2.The route and dose of the exposure
The precise nature of any species barrier for CWD transmission between white-tailed deer and
humans has, as yet, not been described. Given the fact that controlled experiments cannot be
conducted in human beings, the existence of a species barrier cannot be directly tested. However,
there is limited experimental evidence of a species barrier (Raymond et al. 2000). Further supporting
the notion that such a species barrier exists is the observation that humans have been handling and
consuming tissues from infected deer for decades with no evidence to date of any correlation with
any human illness. The U. S. Centers for Disease Control (CDC) has investigated Creutzfeldt-Jakob
disease (CJD) among three individuals thirty years of age or younger who had some association with
hunting or consumption of venison (not related to the ongoing CDC investigation in Wisconsin) and
has concluded that there was no evidence for a causal link with the consumption of venison (Belay et
al., 2001).
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The route of exposure to TSEs is also an important determinant of the efficiency of transmission.
Oral (i.e. ingestion) exposure is among the least efficient means of transmitting any TSEs. In many
circumstances, TSEs that can be transmitted by the artificial route of intracranial (IC) inoculation
directly into the brain cannot be transmitted by the oral route. Under experimental conditions when
the dose can be controlled, it generally requires a far greater dose (typically 1,000- to 100,000-fold
more) to transmit a given TSE at the same rate by the oral route than by the IC route.
The collection of leachate from a large landfill, the co-mingling of the solids from the leachate with
other solids from the sewerage system and its mixing with 9 inches of topsoil provides an extremely
large dilution factor. In addition, any prions that enter the environment will degrade with time.
In summary, it is reasonable to conclude that while absolute numbers relating to human health risk
cannot be generated, the available knowledge about CWD and other TSEs suggests that landfilling of
CWD-infected deer does not pose a significant risk to human health.
5.2 Likelihood of Transmission to Deer
The major factors that influence the risk to deer from the landfilling of a population of deer some of
which are infected with CWD are:
1.The absence of a species barrier
2.The route of exposure
3.The concentration reduction factors inherent in sludge production and
application
4.The consumption of soil by deer.
For any TSE that is transmitted within the same species there is assumed to be no species barrier. The
consequence of this is that deer are the most susceptible species to any exposure to viable CWD agent
that enters the environment. For deer there may, however, be genetic influences on susceptibility and
incubation period. For CWD this information is not known. Therefore, the approach in this
document has been to assume that all white-tailed deer are equally susceptible to CWD infection.
The primary route of exposure to the CWD prion for deer from sludge amended soil is by ingestion.
Typically for the TSEs the oral route is among the least efficient means of transmission. However,
the oral infectious dose of CWD for deer has not been determined.
The collection of leachate from a large landfill, the co-mingling of the solids from the leachate with
all the other solids from the sewerage system and then its mixing with 9 inches of topsoil provides an
extremely large concentration reduction factor. Should any viable CWD prions make it out into the
environment it is likely that they will degrade with time and will be diluted due to the mixing to a
depth of 9 inches.
In conclusion, it is deemed likely that the risk of spreading CWD among Wisconsin's deer population
by landfill disposal of infected carcasses is quite small.
6. References:
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7
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thth
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Transmission of prions
C. Weissmann, M. Enari, P.-C. Klöhn, D. Rossi, and E. Flechsig;
PNAS published August 14, 2002, 10.1073/pnas.172403799 ( Colloquium ).
http://www.pnas.org/cgi/reprint/172403799v1.pdf
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City Council Memorandum
December 14, 2009
TO: Janesville City Council
FROM: Sustainable Janesville Committee
SUBJECT: Sustainable Janesville Committee’s Supporting Information
Regarding the Landfilling of Deer Carcasses at the Janesville
Municipal Landfill.
Committee Recommendation
At their December 1, 2009 meeting the Sustainable Janesville Committee
forwarded the following motion to the City Council:
“Move that the Sustainable Janesville Committee recommends to
the City Council that they authorize the City Manager to enter into
the proposed indemnification agreement with Wisconsin DNR, and
that the City Landfill be required to operate in compliance with the
WisDNR indemnification agreement, and further direct the City
Manager to review the City’s position on accepting deer carcasses
on an annual basis and make an annual recommendation to the
City Council.”
The motion was made by Committee Member Swanson with a second by
Committee Member Hyzer. The original motion passed on a 4-3-0 vote with
Committee Members Swanson, Hyzer, Udell and Councilmember Perrotto in
support and Committee Members Mills, Backenkeller and Cunningham opposed.
Background
As part of the discussion, Councilmember Perrotto suggested that Committee
Members should provide their thoughts on the issue in writing and provided to
the City Council. Councilmember Perrotto thought this information would be
helpful to the Council when making their decision on this matter at their
December 14 meeting. The following is a list from those Committee Members
who chose to provide their comments to the City Council in their words:
________________________________________________________________
Majority View Point ~ Ann Hyzer
“Primary criteria in support of vote to have City Council move forward with
authorization for the City Manager to enter into the Indemnification Agreement
CWD is a disease of the deer family.
Several studies provide evidence that, to date, CWD has not been transmitted to humans.
Additionally, routine surveillance has not shown any increase in the incidence of
Creutzfeldt-Jakob disease (a human prion disease) in Colorado or Wyoming. Because of
the long time between exposure to CWD and the development of disease, however, many
years of continued follow-up are required to be able to say what the risk, if any, of CWD
is to humans. We cannot say with absolute scientific certainty this will never happen, but
the preponderance of scientific research contains no strong evidence of CWD
transmission to humans.
The Center for Disease Control (CDC) states that the mode of transmission of CWD
among deer is not fully understood, but evidence supports the possibility that the disease
is spread through direct animal-to-animal contact or as a result of indirect exposure to
prions in the environment (e.g., in contaminated feed and water sources.). DNR
Specialist, Tim Lizotte, indicated that the exposure route for CWD in deer is oral. Lizotte
said deer eat a lot of soil when grazing in woods and pasture. Dermal (through the skin)
and airborne exposure paths have not been shown. ---- The bottom line is that landfilling
will essentially “entomb” potentially contaminated deer carcass residues and prevent
deer from coming in contact with any pathogens, therefore preventing the spread of the
disease from those landfilled carcasses.
This begs the following question: What happens if prions actually end up disposed of
in a landfill through infected deer waste? Could the pathogens move with the leachate
through the landfill and be removed via the leachate collection system? What happens
then?
As a soil scientist and former environmental regulator with the Minnesota Pollution
Control Agency I wanted to see some research that gave sound evidence that any prions
associated with infected deer carcasses put into the landfill system would stay in the
landfill.
A well designed study was conducted jointly by researchers in the fields of Civil and
Environmental Engineering, Comparative Biosciences, and Soil Science at the University
of Wisconsin-Madison to evaluate the fate of prions in a landfill simulation. The study
was designed to simulate what would happen if the disposal of CWD-infected deer
carcasses in a MSW landfill occurred. The findings were published in the Journal of
Environmental Science and Technology in 2009 (VOL. 43, NO. 6), a peer-reviewed
publication. The results indicated the following:
?
“Penetration into the burial material over the 46 year simulation period was <20
mm (<1 inch.)
?
“These analyses indicated that concentrations of the [infectious prions] in a
leachate collection system should be effectively zero for the conditions that were
simulated, regardless of whether the CWD waste is encased in burial soil.”
Prions do not dissolve well in water, or MSW landfill leachate, and therefore bond very
tightly to soil particles within the landfill. They appear not to move and are not detected
at very low detection levels within landfill leachate. Prions will stay in the landfill under
a normal, controlled management regime.
Based on these results, I’m satisfied to a high degree that prions from CWD infected
deer, if placed in a landfill, would remain in the landfill adsorbed to soil. But will the
prion even be unearthed in the future? Could the prion material be re-exposed?
The Janesville MSW landfill is governed by DNR rules that include stringent closure
procedures and follow-up monitoring. An impermeable “cap” will be placed on the
landfill at closure which will prevent the movement of water through the landfill. In
addition, the indemnification agreement requires that Global Position System (GPS)
equipment be used to record coordinates of the deer disposal trench location and put into
the landfill records. The landfill record will be maintained during the operating life and
the 40 year long-term care period of the landfill. After the long-term care period, deed
restrictions will control, and effectively eliminate, the possibility of the deer carcass
material being unearthed.
The International Association of Fish and Wildlife Agencies state the following in a
publication Transportation and Disposal of Hunter-Killed Cervid Carcasses:
Recommendations to Wildlife Agencies to Reduce Chronic Wasting Disease Risks, March
2006:
?
“If all unwanted carcass parts, scraps, and trims removed from the field were
disposed of properly, the risk of CWD introduction via carcass transport would
essentially be eliminated.”
?
“Throughout North America, responsible agencies should recommend that
hunters, game farmers, processors, and taxidermists properly dispose of all
wastes from processed cervids.”
?
“The U.S. Environmental Protection Agency recognized the current reliance of
hunters on landfills to dispose of parts and occasional carcasses and affirmed
there is no reason to believe this practice is inappropriate.”
In closing--
Other means of deer waste disposal methods that destroy the CWD prion (i.e., high
temperature incineration and chemical digestion) are relatively very expensive. When
compared to the very, if not infinitesimally, small probability of transmission of CWD to
deer, or humans for that matter from landfilled deer waste, landfilling is an
economically, environmentally and public-health justified method of disposal of deer
carcasses.”
Ann Hyzer, Sustainable Janesville Committee, December 12, 2009
________________________________________________________________________
Minority View Point ~ Matt Mills
“What the recommendation by the SJC to landfill deer carcasses means for the City
Council. The WiDNR and deer hunters can buy a little more time in their loosing battle
with Chronic Wasting Disease. Expensive tissue digesters and high temperature
incinerators will not be used to destroy the prions in the environment. Instead, we will be
collecting and holding the areas infectious prions in our landfill. The risk of infectious
prion disease will remain in the landfill for both deer and the citizens of Janesville for
longer than the life of the landfill. And, we will be unable to monitor the presence of
prions in the leachate from the landfill or sludge from the wastewater treatment plant,
since no test exists to detect prions in either leachate or sludge.”
Matt Mills -Sustainable Janesville Committee Chairperson
_______________________________________________________________________
Minority View Point ~ Julie Backenkeller
“My concerns with CWD infected carcasses being landfilled, is that there is not enough
long term information about the disease. What is known, is that prions (the bad stuff) stay
viable in soils for very long periods of time. The only way to completely destroy the
prions is through chemical digestion, or incineration at very high temperatures. Our goal
is to destroy the prions. Burying them in the landfill does not do this. It is not the
responsibility of the residents of the City of Janesville to manage CWD for the WDNR.
Investing in proper disposal must be considered. In 2005, over 74 million tons of deer
waste was deposited into the Dane County landfill from November-February (This
information is incorrect. Dane County indicated they receive 3.8 tons). Regardless of
how many of these carcasses were infected with CWD, burying the carcasses, which
could be unearthed at some point by natural disaster or other, will further spread the
disease. Potential for prions to be spread over farmfields in sludge from leachate to
waste water, is the concern of water utilities, and should be considered.
Again, the WDNR needs to provide hunters with an option for carcass disposal that
destroys the prions. The residents of the City of Janesville should not be subjected to
potential damage to health and our environment because the WDNR is looking for a
cheap disposal option.
Use precaution.”
Julie Backenkeller
________________________________________________________________
cc: Eric Levitt
Jacob Winzenz
John Whitcomb