905R88112
v>EPA
United States
Environmental Protection
Agency
Office of Public Affairs
Region 5
, 230 S. Dearborn
Chicago, II 60604
Illinois Indiana
Michigan Minnesota
Ohio Wisconsin
Summary of Risk
Assessment and Proposed
Risk Management Actions
Midland, Michigan
April 1988
Not to Scale
Consumers Power Company
Cooling Ponds
FIGURE 1
Dow Chemical Company
Midland Plant Site Map
Midland, Michigan
INTRODUCTION
In 1983, at the request of the Michigan Department of
Natural Resources (MDNR), the U.S. Environmental
Protection Agency (U.S. EPA) initiated a series of
environmental studies in the Midland, Michigan, area for
dioxins and other tone pollutants. Much of this
investigative work focused on sources of dioxins at the Dow
Chemical Michigan Division Midland Plant. The results of
different parts of these studies were released in 1985 and
1986.
U.S. EPA is now releasing a summary of the final results of
each study, and an assessment of the possible public health
risks associated with dioxin exposures in the Midland area.
U.S. EPA is also seeking public comment on the risk
assessment and proposed risk management actions it
believes are appropriate to further reduce dioxin emissions
and discharges from Dow Chemical, and to further reduce
public exposures to dioxins. This fact sheet summarizes the
results of the risk assessment and risk management study.
The public will have an opportunity to comment on the risk
assessment and risk management reports during a public
comment period beginning April 25,1988. More
information about these studies and the comment period is
located at the end of this fact sheet under "Opportunities for
Public Involvement." %*
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MAJOR FINDINGS AND
CONCLUSIONS
• Point source and environmental studies
conducted by U.S. EPA, the State of
Michigan, and Dow Chemical over the past
several years indicate that the Dow Chemical
Midland plant has been the most significant,
if not the only significant, source of dioxin
contamination at the plant site and the
general Midland area.
• 2378-TCDD and other dioxins and related
compounds have been found in native fish
from the Tittabawassee River; in surface soils
at the Dow plant and at relatively low levels
in the community; and in ambient air outside
of the plant. Dioxins have not been found in
the public or private drinking water supplies
that were tested.
• Discharges and emissions of dioxins from
Dow Chemical have been reduced, and levels
in Tittabawassee River fish may be declining.
Corrective actions implemented by Dow
Chemical over the past several years appear
to have lowered the levels of dioxins outside
the plant.
• Levels of dioxins found in surface soils in the
community, and in ambient air generally do
not present unacceptable public health risks.
Health risks associated with living in Midland
are probably not different from those
experienced in other industrialized
communities.
• The levels of dioxins found in Tittabawassee
River fish present a potential public health
concern for people who eat those fish,
particularly children, pregnant women, and
women of child-bearing age.
• U.S. EPA is proposing certain risk
management actions to further reduce public
exposures and the risk of dioxin
contamination. These include:
Additional Point Source Controls at the Dow
Chemical Midland Plant
• Research on additional wastewater
treatment for dioxins.
• Studies of the possible effects of
incinerator wastewater treatment and
pond sediments on dioxin wastewater
discharge levels.
• Further improvement of combustion
and pollution controls at the
hazardous waste incinerator.
• Continuation of programs to minimize
windblown dust from the plant site.
Precautionary Measures Recommended to
the Public for Minimizing Exposures to
Dioxins
• In Michigan, responsibility for
advising the public on the health risks
of fish consumption lies with the
Department of Public Health
(MDPH). The MDPH currently
advises against any consumption of
catfish or carp from the
Tittabawassee. The U.S. EPA risk
assessment findings provide clear
support for the existing advisory and
also point to possible risks from
consumption of walleye and other
game fish from the river. The MDPH
will consider the risk assessment
findings along with any new data on
fish contaminant levels and local
consumption rates when it reviews its
fish consumption advisory for the
Tittabawassee River.
• Individuals who choose to eat fish
from the Tittabawassee River should
clean them in accordance with
Michigan Department of Public
Health recommendations.
• Parents of toddlers and children with
pica (those who eat large amounts of
soil) should encourage their children
to keep dirt or soil out of their
mouths.
U.S. EPA is also proposing a number of
supplemental monitoring programs for Dow
Chemical. These are outlined on page 6.
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HISTORY OF DIOXIN
STUDIES IN MIDLAND
The Dow Chemical Company has
manufactured more than 1,000 different
chemicals at its Midland facility between
the 1930s and 1970s, including pesticides
and other chlorinated products. Dow
Chemical no longer manufactures those
chemicals most often associated with
dioxin formation. Hazardous and non-
hazardous wastes have been incinerated
at the site since the 1930s.
In June 1978, Dow Chemical informed
the MDNR that rainbow trout exposed
to Dew's treated wastewater had
accumulated significant levels of 2,3,7,8-
tetrachlorodibenzo-p-dioxin (2378-
TCDD), the most toxic of the dioxin
compounds. Based on the results of that
study and analysis of native catfish from
the Tittabawassee River, the Michigan
Department of Public Health (MDPH)
issued a formal advisory in June 1978
warning against consumption of any fish
collected from the Tittabawassee River
downstream of the Dow Dam. The
advisory remained in effect until March
1986, when the MDPH modified it to
apply only to catfish and carp, after
reviewing 1985 monitoring data
indicating lower levels in the game fish.
In response to the Dow Chemical
findings, the MDNR and U.S. EPA
conducted a number of investigations
from 1978 through 1981 to determine
whether or to what extent the Dow
Chemical Midland Plant had contributed
to 2378-TCDD contamination in
Tittabawassee River fish. The 1981
study results showed that wastewater
originating from the plant was a
significant source of 2378-TCDD in the
Tittabawassee River. The preliminary
results from those studies were released
in March 1983 with a series of
recommendations for additional dioxin
studies in Midland and elsewhere.
Those recommendations were reflected
in U.S. EPA's Dioxin Strategy and
National Dioxin Study.
In March 1983, the State of Michigan
made a formal request to the U.S. EPA
for assistance in conducting a series of
dioxin studies at the Dow Chemical
Midland Plant, and assessing dioxin
contamination in the Midland area. In
the spring and summer of 1983,
U.S. EPA coordinated planning for the
studies with several state agencies. The
studies, collectively called the Michigan
Dioxin Studies, included the following
elements:
• Native fish and sediment sampling in
the Tittabawassee River.
• Surface soil sampling at the Dow
Chemical Midland Plant, in the city
of Midland, and at comparison sites.
• Evaluation of public and private
drinking water supplies and Dow
Chemical brine operations.
• Dow Chemical wastewater and
sewer system sampling.
• Incinerator emissions and limited air
monitoring.
These investigations included analyses
for dioxins and other toxic pollutants
that might be present.
In 1983, Dow Chemical initiated its own
investigation of dioxins at the Midland
Plant. That work included surface soil
sampling at the plant, untreated and
treated wastewater sampling, incinerator
emissions testing and limited air
monitoring.
In 1987, Dow Chemical conducted
additional incinerator emissions testing,
monitoring of Tittabawassee River fish
in response to a consent order with
U.S. EPA, and twice monthly monitoring
for 2378-TCDD in process wastewater
discharged to the Tittabawassee River.
Studies by Dow Chemical and U.S. EPA
revealed widespread contamination of
surface soil at Dew's Midland facility,
with an average concentration of 0.5 ppb
2378-TCDD. Several small areas within
the facility were found to be more highly
contaminated (2 ppb to 50 ppb).
U.S. EPA studies also found lower level
dioxin contamination of soils throughout
the community, with an average
concentration of less than 0.1 ppb. -
Since then, Dow has paved over the
heavily contaminated soil at the plant in
response to U.S. EPA orders. The
sources of on-site soil contamination
appear to have been leaks or emissions
from the production processes and the
waste incinerator. The off-site soil
contamination has been attributed to
airborne incinerator emissions of
dioxins, wind-borne contaminated soil
from the facility, and past emissions
from production operations.
Significant levels of dioxins have also
been detected hi treated Dow Chemical
wastewater which is discharged to the
Tittabawassee River. Studies conducted
between 1979 and 1985 determined that
2378-TCDD persisted at levels of
concern hi Tittabawassee River native
fish, despite the shut-down of the Dow
Chemical Midland Plant production
facilities principally associated with
dioxin formation.
The most recent information indicates
2378-TCDD levels in native fish may be
declining. Data collected in 1985 show
that native Tittabawassee River fish
collected downstream of the Dow
Chemical Midland plant area are also
contaminated with other organic
chemicals, including PCBs. The Dow
Chemical Midland Plant is not believed
to be a significant source of PCBs.
The U.S. EPA has evaluated data from
its testing programs and available data
from other studies in a risk assessment
for people living in the Midland area. A
summary of the risk assessment is
presented in the following section. «*
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RISK ASSESSMENT
There are four components to a risk
assessment:
Hazard Identification - Identifies the
hazards and potentially toxic effects a
contaminant may produce on human
health and the environment.
Dose-response assessment - Determines
the dose or amount of the contaminant
that may produce an adverse human
health response.
Human exposure assessment - Assesses
the potential for people to come in
contact with the contaminant, as well as
the maximum amount of exposure which
may occur.
Risk characterization - Combines all the
above factors to estimate the potential
health impacts from the contaminant in
question. Also, the uncertainty
associated with the risk estimates is
reviewed.
HAZARD IDENTIFICATION
Chlorinated dibenzo-p-dioxins (CDDs,
or simply dioxins) are a family of 75
related chemical compounds with
varying chemical, physical, and
toricologic properties. The form of
dioxm that appears to be the most toxic,
and has generally raised the greatest
health concerns, is 2,3,7,8-
tetrachlorodibenzo-p-dioxin, abbreviated
as 2378-TCDD.
Experimental studies with 2378-TCDD
in laboratory animals have shown a
variety of toxic effects. These include
cancer, reproductive effects, liver
damage, effects on the skin and thyroid,
and effects on unborn offspring.
U.S. EPA has determined that the
critical concerns associated with
exposure to dioxins in the Midland area
are cancer, reproductive and teratogenic
effects, and liver damage. A teratogen is
a substance which has adverse effects on
an unborn child, when the mother is
exposed.
DOSE-RESPONSE ASSESSMENT
The evidence for the cancer-causing
effects of 2378-TCDD comes mainly
from several long-term studies of
laboratory animals exposed to the
substance. Based on these studies and
other factors, U.S. EPA has concluded
that 2378-TCDD causes cancer in
animals and should be regarded as a
probable human carcinogen. U.S. EPA
used the experimental animal data to
develop dose levels at which various
health effects may occur. U.S. EPA is
currently re-evaluating its estimates of
the cancer potency of 2378-TCDD.
Many of the samples of fish, soil, water,
and air analyzed in U.S. EPA's studies
were found to contain several different
types of dioxins and related compounds
called chlorinated dibenzofurans.
U.S. EPA has developed a procedure for
estimating the toricity of mixtures of
dioxins and the related compounds by
converting the results to equivalent
amounts of 2378-TCDD. This approach
was used in the risk assessment to take
into account the possible toxic effects of
the other dioxins and related
compounds.
HUMAN EXPOSURE ASSESSMENT
Exposure to Ambient Air
Midland has a total population of
approximately 32,000 people. About
26,000 of these people live within three
miles of the Dow Chemical Midland
Plant. Most of the population lives
between 05 and 35 miles north of the
plant. However, several residences are
located closer to the facility. Based on
the results of ambient air studies, many
of Midland's residents have been
exposed to low levels of dioxins in the
air. For the risk assessment, U.S. EPA
evaluated the exposures of two groups of
people: (1) a group who would
theoretically live their lives near the
fenceline of the Dow plant and (2)
another group who live in the more
heavily populated area north and
northeast of the plant.
Exposure to Soil
Soil studies conducted by U.S. EPA
indicate that the average level of 2378-
TCDD in Midland soils outside the Dow
Chemical plant is less than 0.1 ppb. This
is well below the 1 ppb level in
residential soils at which the Centers for
Disease Control (CDC) recommends
consideration of actions to minimize
exposures.
Some possible routes of exposure to
dioxins in Midland soils include: direct
ingestion by children playing outdoors;
ingestion of household dusts which may
be contaminated from outdoor soils;
ingestion of soil attached to home-grown
vegetables; absorption through the skin
which comes in contact with the soil
through play, gardening, or other
activities; and inhalation of contaminated
participates from the soil.
U.S. EPA soil studies in Midland have
shown that dioxins tend to concentrate in
areas near roof downspouts or drip lines.
Toddlers and children with pica are
likely to ingest more soil than older
children or adults. Children with pica
intentionally consume large amounts of
soil; this is considered a medical
disorder.
For the risk assessment, U.S. EPA
evaluated two levels for people exposed
to contaminated soils under normal
conditions. Children with pica were
considered as a separate group.
Exposure to Drinking Water
Based on testing and follow-up surveys,
U.S. EPA concluded that 2378-TCDD
was not present in the major public and
the private drinking water supplies
tested.
Fyppsure to Contaminated Fish
Fish consumption presents the most
significant exposure to dioxins in the
Midland area for people who eat fish
caught in the Tittabawassee River. This
is because toxic substances such as
dioxin (and PCBs) tend to collect and
concentrate in the fatty tissues of fish
and are directly ingested into the body
by those who eat fish. Although the
Tittabawassee River is not used for
commercial fishing, it is heavily used by
sport fishermen.
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Fishermen and their families who may
eat fish from the Tittabawassee River as
a significant portion of their diet are of
most concern. Bottom-feeding fish, such
as catfish and carp have been shown to
accumulate higher levels of
contaminants than game fish. These fish
are usually more fatty than game fish
and obtain more of their food from river
sediments which may be contaminated.
Tittabawassee River game fish, such as
walleye, smaUmouth bass, crappie,
northern pike, and yellow perch, contain
lower levels of 2378-TCDD, with an
overall average concentration of less
than 5 ppt.
For the risk assessment, U.S. EPA
evaluated risks for several groups of
people who might eat Tittabawassee
River fish. The highest group might eat
as much as 80 Ibs/year, half of which
would be game fish and half bottom-
feeding fish. The lowest group would eat
only 6 Ibs/year, half of which would be
game fish from the Tittabawassee River
and half uncontaminated fish from
another source.
Other Routes of Exposure
Infants may be exposed to dioxin when
breast fed. Compounds such as dioxin
are retained in the fatty tissues of the
mother, and are secreted in fat-rich milk.
Infants who depend on their mother's
milk for most or all of their diet, could
be exposed to higher levels of dioxin
than the mother herself. However, the
many important benefits of breast
feeding probably outweigh these risks in
most cases.
RISK CHARACTERIZATION
As noted earlier, U.S. EPA's risk
assessment focuses on cancer,
reproductive and teratogenic effects, and
liver damage as the critical public health
concerns for dioxin contamination in
Midland. U.S. EPA evaluated possible
public health risks associated with
cancer, in terms of the excess rate of
cancer expected beyond the national
average cancer rate which is about one
in four. The estimated excess lifetime
cancer risks associated with dioxin
exposures in the Midland area are
presented in Table 1. Note that these
"upper-bound" risks are based on
conservative assumptions. Actual risks
to Midland residents are likely to be
lower than the values shown below.
Cancer risks from consumption of
Tittabawassee River fish are estimated
to be the most significant and much
higher than risks associated with
exposure to Midland soils or ambient
air.
The greatest estimated non-cancer risks
are also associated with activities where
people eat or ingest materials containing
dioxins. These activities include fish
consumption, soil ingestion by children
with pica, and breast feeding by mothers
who have had high rates of exposure.
Again, fish consumption is by far the
most significant. Non-cancer effects
include adverse effects on the
reproductive systems and the liver.
U.S. EPA believes actions should be
considered to minimize exposure to
substances when the estimated excess
lifetime cancer risk levels exceed 1 in
100,000 to 1 in 1,000,000 range, or when
non-cancer risks are estimated to be
significant based on comparison with
reference doses and health advisories.
The following section discusses actions
that have been taken and should be
taken to reduce risks to Midland
residents from dioxin exposure.
SUMMARY OF ESTIMATED UPPER BOUND CANCER RISKS
FROM EXPOSURE TO DIOXIN CONTAMINATION
IN MIDLAND, MICHIGAN
Estimated Excess Lifetime Cancer Risk
Exposure
Route
Higher Estimate
Lower Estimate
Fish
1 in 100 (maximum consumer)
1 in 1,000 (high sports fisherman) 1 in 10,000 (occasional consumer)
Soil
1 in 100,000 (upper estimate)
1 in 10,000 (child with pica)
1 in 1,000,000 (lower estimate)
Air
1 in 10,000 (fenceline)
1 in 100,000 (residential area)
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PROPOSED RISK
MANAGEMENT ACTIONS
Collectively, the point source and
environmental studies conducted by
U.S. EPA, the State of Michigan, and
Dow Chemical over the past several
years clearly indicate that the Dow
Chemical Michigan Division plant at
Midland has been the most significant, if
not the only significant, source of dioxin
contamination at the plant site and the
general Midland area. As a result of
these investigations Dow Chemical has
completed or is implementing several
actions to minimize emissions and
discharges of dioxins and other toxic
pollutants. They are as follows:
• Terminated production of certain
chlorinated chemical compounds.
Installed a riverbank revetment
system to collect contaminated
ground water.
Upgraded operations and air
emission controls on the hazardous
waste incinerator.
Paved areas in the plant with high
levels of surface soil contamination.
Replaced open wastewater ditches
at the plant with enclosed sewers.
Installed a wastewater effluent
filtration system for the entire
treated wastewater discharge to the
Tittabawassee River. Provided
preliminary treatment of incinerator
scrubber waters.
Implemented a dust suppression
program on the plant site.
Recent data have shown reduced
incinerator emissions, reduced
wastewater effluent discharge levels an
to some extent, reduced fish
contamination levels. Overall,
conditions have improved significantly
over the last ten years. Despite this, th
levels of discharge and environmental
contamination as depicted by point
source and environmental data collecte
during the 1983-1986 period indicate th
further remedial work at the plant site
may be necessary. Minimization of
exposures through precautionary
measures by the public could be helpfu
in reducing the possible public health
risks described earlier.
U.S. EPA is proposing that the following programs
be conducted by Dow Chemical:
PROPOSED REMEDIAL ACTIONS BY DOW
CHEMICAL
WASTEWATER DISCHARGES
* Feasibility and end-of-pipe wastewater treatability
studies for dioxins.
• Assessment of the amount of 2378-TCDD in pond
sediments and a study to determine to what extent
resuspended sediments containing dioxins pass
through the filtration system.
• Evaluation of the effectiveness of the incinerator
wastewater pretreatment system.
AIR EMISSIONS
• Continue efforts to improve combustion conditions in
the waste incinerator, and operation of air pollution
control equipment to reduce dioxin emissions.
• Continue programs to reduce the amount of
windblown dusts from the plant site.
PROPOSED POINT SOURCE AND
ENVIRONMENTAL MONITORING
PROGRAMS BY DOW CHEMICAL
U.S. EPA proposes that the following programs be
conducted by Dow Chemical to confirm that control
measures installed from 1984 to 1987 are effective:
• Continued wastewater discharge monitoring.
• Supplemental incinerator emissions and ambient air
testing.
• Continued Tittabawassee River fish monitoring.
• Tittabawassee River sediment monitoring.
• Limited food chain studies (dairy sampling; garden
vegetable sampling; animal, aquatic life, and bird
sampling).
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PRECAUTIONARY MEASURES
RECOMMENDED TO THE PUBLIC
Although operations at Dow Chemical have caused
widespread contamination of the Midland area with 2378-
TCDD and other dioxins, U.S. EPA believes the levels of
contamination, with the exception of Tittabawassee River fish,
do not present unacceptable or unmanageable health risks
to the Midland community. There are, however, a number of
actions people can take to minimize exposures, and thus
minimize possible health risks associated with dioxins. Most
of these recommendations focus on avoiding or reducing
ingestion of materials that contain dioxins.
TITTABAWASSEE RIVER FISH
In Michigan, legal responsibility for evaluating health
risks and issuing health advisories resides with the
MDPH. At this time, the MDPH has in place a fish
advisory warning against consumption of catfish and
carp taken from the Tittabawassee River. These fish
contain much higher levels of 2378-TCDD and other
organic chemicals than other fish. As shown in the
risk assessment, regular consumption of even
relatively small amounts of these fish over the long
term may pose substantial risks of cancer. Also,
long-term consumption or, in certain circumstances,
short-term consumption of these fish may pose
significant risks of adverse impacts other than
cancer. The current Michigan fish consumption
advisory for catfish and carp is fully supported by
U.S. EPA studies.
The risk assessment also highlights possibly
significant risks from consumption of game or sports
fish (e.g., walleye, northern pike, smallmouth bass,
and white bass). These risks may be associated
with both short-term and long-term consumption.
The MDPH has been conducting a creel survey to
better define fish consumption patterns for
Tittabawassee River fishermen and their families.
The MDPH also has been actively participating in
ongoing discussions with the other Great Lakes
states, the U.S. EPA, and the Food and Drug
Administration, seeking a uniform basis for fish
consumption advisories. The MDPH will consider
the risk assessment findings along with any new
data on fish contaminant levels and local
consumption rates when it reviews the fish
consumption advisory for the Tittabawassee River.
Individuals who choose to consume any fish caught
in the Tittabawassee River should clean them in
accordance with MDPH recommendations. Fillets
should be skinned, with all visible traces of surface
fat removed. All belly fat from the fillet should be
removed, as well as dark tissue along the lateral line
on each fillet. Cooking methods which allow fats
and juices to drain from the fish may reduce
contaminant levels in the cooked fish.
CITY OF MIDLAND SURFACE
SOILS
The overall estimated cancer and non-cancer risks
from exposures to surface soils in Midland are not
considered to be significant except possibly for
children with pica. Parents of toddlers and children
with pica should encourage their children to keep
dirt or soil out of their mouths.
Other commonsense measures such as thoroughly
washing hands after exposure to outdoor soils;
washing or peeling home-grown vegetables prior to
eating; and regular house-cleaning to remove dusts
are also encouraged.
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OPPORTUNITIES FOR PUBLIC INVOLVEMENT
PUBLIC INFORMATION
REPOSITORIES
For more information about U.S. EPA's
dioxin studies in the Midland area,
please consult the information contained
in repositories at the following locations.
Complete copies of the risk assessment
and proposed risk management reports
are available for review at:
Grace A. Dow Memorial Public Library
Emilia Parker
1710 West St. Andrews Drive
Midland, MI 48640
(517) 835-7157
Midland Health Department
Dr. Winifred Oyen, Director
125 West Main Street
Midland, MI 48640
(517) 832-6655
Ingersoll Township Hall
Kurt Shaffner, Supervisor
4400 Brooks Road
Midland, MI 48640
(517) 835-5289
FOR ADDITIONAL
INFORMATION
Please contact:
John Perrecone
Community Relations Coordinator
U.S. EPA Region 5
230 South Dearborn Street
Chicago, IL 60604
(312) 886-6685
1-800-621-8431 (TOLL FREE,
8:30 a.m. - 4:30 p.m., Central Time)
Gary Amendola
U.S. EPA Project Manager
Michigan Dioxin Studies
U.S. EPA Eastern District Office
25089 Center Ridge Road
Westlake, OH 44145
(216) 835-5200
PUBLIC MEETING
The U.S. EPA is holding a public
meeting to discuss the risk assessm
and risk management reports, and
accept comments on these studies.
U.S. EPA personnel will be availat
answer questions the public may hi
about dioxin, health risks, and othe
topics.
DATE: April 28,1988
TIME:
PLACE:
Northeast Intermedia!
School, the Little Thei
1305 E. Sugnet, Midla
Michigan
PUBLIC COMMENT PERK
There will be a 30-day comment p<
to receive input from interested cit
about the risk assessment and proj
risk management actions. The cor
period will begin April 25,1988.
Comments must be postmarked bj
June 3,1988 and mailed to:
John Perrecone, 5PA-14
Office of Public Affairs
U.S. EPA Region 5
230 South Dearborn Street
Chicago, IL 60604
vxEPA
U. S. Environmental Protection Agency
Region 5
Office of Public Affairs
230 South Dearborn Street
Chicago, IL 60604
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