United States
Environmental
Protection Agency
Office of Solid Waste and
Emergency Response
(5204G)
&EPA
EPA 540-K-96-003
OSWER 9200.2-261
PB96-963227
February 1997
OCUS ON RISK ASSESSMENT
What is Risk Assessment?
Driving acar, eating ameal,
or flying in an airplane—all
of these ordinary activities
pose some degree of risk to
our health and well-being.
Every day, people take a
multitude of risks. Many have
well-documented potential
for harm. We think about our
needs, and decide for
ourselves which risks are
worth taking.
It isn't as easy to make
decisions about risks related
to environmental pollution.
How dangerous is that
Superfund site nearby? Past
land uses like wood treating,
metal plating, dry cleaning,
and waste disposal may have
left hazardous chemicals in
the soil at these sites. In
many cases, contaminants
have moved into the ground
water, air, or surface water.
Super-fund's Human Health
Risk Assessment Asks:
1. What contaminants exist
at the site?
2. How are people exposed
to them?
3. How dangerous could
contaminants be to
human health?
4. What contaminant
concentrations are safe?
People who then come into
contact with these contaminated
media face a certain degree of
risk. But how much? We
need expert help to answer
the question of whether or
not we are at risk.
The professionals who
practice "risk assessment"
pro vide that help. Superfund's
risk assessors determine how
threatening a hazardous waste
site is to human health and
the environment. They seek
to determine a safe level for
each potentially dangerous
contaminantpresent—alevel
at which ill health effects are
unlikely and the probability
of cancer is very small. While
risk assessors frequently
analyze threats to the
environment, the protection
of human health is considered
paramount.
The clipboard (left) shows
the four main questions the
risk assessment process
answers. Each Superfund site
is unique in terms of
contaminants and their
potential health effects.
Therefore, EPA conducts
risk assessments on a site-
by-site basis. The risk
assessment estimates the
current and possible future
risks if no action were taken
to clean up the site. The goal
This Issue...
• Profiles Superfund's
human health risk
assessment
process;
• Presents a case
study in risk
assessment;
• Discusses some
cleanup approaches
that reduce risk; and
• Provides resources
you can tap for more
information.
is to manage risks to
acceptable levels. Risk
managers balance risk
information against a variety
of site factors to select the
best cleanup strategies.
Living near a Superfund site
doesn't automatically place a
person at risk—that depends
on the chemicals present and
the ways people are exposed
to them. Indeed, the risk from
a Superfund site is often
considerably less than many
risks we take every day. Still,
Americans wantto be informed
about these unfamiliarthreats.
The pages that follow describe
how EPA measures human
health risk at hazardous waste
sites. Q
•February 1997«
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•Superfund Today-Risk Assessment-
Superfund's Risk Assessment Process for
Human Health
A Superfund human health risk
assessmentestimatesthe "baseline risk."
This is an estimate of the likelihood of
health problems occurring if no cleanup
action were taken at the site. To estimate
the baseline risk at a Superfund site,
EPA undertakes a four-step process:
Step 1: Analyze Contamination
Step 2: Estimate Exposure
Step 3: Assess Potential Health
Dangers
Step 4: Characterize Site Risk
Over years of cleanup experience, risk
assessors have refined scientific
approaches, assumptions, and equations
to support risk assessment decisions.
These are documented in guidances that
help them make informed, consistent
decisions about potential health risks.
Analyze
Contamination
Scientists collect samples of soil, air,
water, sediment, plants, fish and/or
animals at and around the site. They
analyze these samples in laboratories.
These analyses reveal the chemicals
present and their levels. Risk assessors
consult past scientific studies on the effects
thesechemicalshavehadonpeople. Where
human studies are unavailable, risk
assessors look at animal studies. They
compare chemical levels at the site with
those in the studies. This helps determine
Risk
Assessment
1
Analyze
Contamination
K -7
2
^stimate
Exposure
K ^
3
A Assess Potential
H Health Dangers
K >
4
Characterize
Site Risk
Paves the Way for...
Risk
Management
exposure might reasonably be expected to
occur. People may come into contact with
chemicals in a variety of ways: breathing,
touching, or consuming contaminated air,
water, soil, or food. For each of these
"pathways," EPA estimates quantities
of a given chemical that could reach a
person's lungs, digestive system, or skin.
To do this, EPA's risk assessors ask such
questions as:
^ Do people live or work on or
near the site? For how long?
^ Do children play on or near the
site? How frequently?
^ Do people drink or shower with
site-contaminated water? How
frequently?
which site chemicals are most likely to
pose the greatest threat to human health.
The rest of the risk assessment study
focuses on these chemical substances.
Estimate
Exposure
EPA calculates ways people might be
exposed to the chemicals identified in
Step 1 and at what levels. Risk assessors
also figure out how many years this
S Do people eat fish from, or
swim in, site-contaminated
lakes or streams? How often?
From this information, risk assessors
calculate the "Reasonable Maximum
Exposure" scenario, or RME for short.
The RME portrays the highest level of
human exposure that could reasonably
be expected to occur from the chemi-
cals identified in Step 1. Exposures are
calculated for groups of people like
children, site workers, and residents.
They take into account how long, how
often, and how many ways people could
be exposed to site chemicals. The
RME scenario also factors in the num-
ber of years exposure could occur if the
site were not cleaned up. Both current
and likely future uses for the site are
considered. Step 2 helps ensure
the selected cleanup remedy protects
all people around a Superfund
site, with a focus on the most
vulnerable or sensitive populations.
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•Superfund Today Risk Assessment-
Assess Potential
Health Dangers
While probable exposure to the
community is being calculated, risk
assessors determine the toxicity, or
harmfulness, of each chemical identified
in Step 1. Obviously, the type and
intensity of potential health problems
vary, depending on the chemicals and
the amount of exposure. Risk assessors
compare the results of animal (and, when
available, human) studies on health
effects to "doses" that could be
encountered around a site. For example,
a likely "dose" could come from
consuming a certain amount of
contaminants as a result of drinking
polluted water every day for 30 years.
Risk assessors use two methods to
evaluate the human health effects arising
from exposure to Superfund site con-
taminants. One approach calculates the
chance of cancer occurring as a result of
exposure. The other compares what is
known about the non-cancer health ef-
fects of chemicals to the concentration of
those chemicals at the site.
The likelihood of any kind of cancer
resulting from a Superfund site is
expressed as a probability; for example,
a"l in 10,000 chance." In other words,
for every 10,000 people that could be
exposed, one extra cancer case may
occur as a result of exposure to site
contaminants. An extra cancer case
means that one more person could get
cancerthan would normally be expected
to from all other causes.
Non-cancer health effects can range
from rashes, eye irritation, and breathing
difficulties to organ damage, birth
defects, and death. Risk assessors
calculate a "hazard index" for non-cancer
health effects. The key concept here is
that a "threshold level" (measured
usually as a hazard index of less than 1)
exists below which non-cancer health
effects are no longer predicted. Risk
assessors determine the amount of a
chemical that can cause a noticeable
non-cancer health effect. Then they use
these data to figure out how dangerous
the site contaminants are.
Characterize
Site Risk
In this step, EPA determines the most
critical site risks and whether they are
great enough to cause health problems
for people at or near a Superfund site.
The results of the three previous steps
are combined, evaluated, and
summarized. Risk assessors add up
potential risks from the individual
chemicals and pathways and calculate a
total site risk. They also consider the
amount of uncertainty in the risk
estimates. Risk assessment results are
then factored into decisions on how best
to clean up the site during the risk
management phase.
Risk Management Puts Risk
Assessment to Work
Risk managers use the data on cancer
risk and non-cancer health effects to
decide how to handle site cleanup. They
also consider several other factors not
related to risk in arriving at final cleanup
Remember...
Risk assessment is not an exact
science. Risk assessors use the best
available data on what is occurring, or
could occur, at the site, and apply their
scientific judgment to calculate the
likelihood of exposure to site chemicals.
Results are probabilities, not certainties.
levels. These factors include state and
federal regulations, costs, treatment
techniques, technological feasibility,
and community acceptance.
The goal is to assess risk and then
manage it. Risk managers plan strategies
to reduce or prevent risk by limiting or
stopping exposure to contaminants. This
does not always call for the removal of
contaminants orthe cleaning of soil, air,
or water. Sometimes cleanup workers
can simply put a cap over the site or
build underground walls to keep
chemicals from reaching people.
Regardless of the approach chosen,
risk managers seek a solution that
will make the site safe for both current
and expected future uses. Until
all cleanup is completed, cleanup
workers continue to check the site. This
ensures contaminant levels
are dropping or remain in the safe
range, and cleanup requirements are
being met. Q
Children Are Often More Vulnerable
to Site Chemicals
They can swallow dirt when
they play
The same "dose" of a
chemical has a greater
effect on a smaller person
due to lower body weight
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•Superfund Today-Risk Assessment-
Case Study
Risk Assessment in Action:
Joseph Forest Products, Wallowa County, Oregon
A Picture of Progress
Q A fire in 1974 at the Joseph Forest Products site destroyed the facility and caused
thousands of gallons of wood treatment solutions and waste to be washed into the
soil.
Q In 1984, the company removed some waste material in response to a violation
notice from the Oregon Department of Environmental Quality. The company was
unable to continue further cleanup efforts after filing for bankruptcy and ceasing
wood treatment operations.
Q EPA testing in 1985 revealed elevated levels of contaminants, primarily arsenic
and chromium, in the soil at the site. In addition, contamination was found in some
ground water and surface water samples.
Q Initial investigations showed that City of Enterprise water supply springs, located
in the path of the contaminated water moving from the site, were threatened by
site contamination. EPA responded by excavating over 1,000 tons of highly
contaminated soil and installing a security fence around a treatment building to
prevent access.
Q These actions ensured the safety of the City water supply and ground water while
EPA conducted a risk assessment and looked into a long-term cleanup plan for the
site.
Q During the site cleanup, City officials visited the site and assisted EPA with
sampling activities. EPA also updated City officials on site progress during City
Council meetings and with periodic fact sheets.
The Risk Assessment
The cleanup efforts begun by Joseph Forest Products and the soil removal conducted by EPA
reduced the immediate threat posed by the site. EPA then conducted a site risk assessment to decide
whether additional measures were needed to protect the public from the long-term risks of
contamination. Like most risk assessments, the one conducted at Joseph Forest Products estimated
"baseline risk," the potential risk of health problems if no additional cleanup actions were taken
at the site. The focus of the risk assessment was to determine cleanup levels appropriate for the
likely future use of the site (in this case, residential). The risk assessment followed the four steps
described on page 2 and page 3.
Step 1: Analyze Contamination
Samples taken of the soil, ground water, and surface water revealed that the main contaminants
were arsenic and chromium. These chemicals were used in wood treatment processes conducted
at the site. The most contaminated areas were on or around the treatment building.
Step 2: Estimate Exposure
EPA identified Reasonable Maximum Exposure (RME) scenarios and estimated human
exposures to contaminants identified in Step 1. These scenarios describe the probable situation if
the site remained contaminated with no cleanup technologies in place, and include both the current
and future uses of the site.
Since residential areas are located directly across the street from the site, both the "current use"
and "future use" RME scenarios were residential. In this case, it was assumed that children living
near the site could ingest or be exposed to contaminated soil.
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•Superfund Today Risk Assessment-
Step 3: Assess Potential Health Dangers
Arsenic and chromium are known to cause non-cancer health effects. Exposure to arsenic can have an effect
on people's nervous systems, usually beginning with numbness, blurred vision, and muscle tenderness. The
primary non-cancer health effect from chromium exposure is kidney damage. Long-term exposure to both
chemicals also can ultimately cause extra cancer cases among the population. As mentioned earlier, an extra
cancer case means that one more person could get cancer than would normally be expected from all other
causes.
Step 4: Calculate Site Risk
Overall, EPA's investigation at Joseph Forest Products found that the high risk of non-cancer health effects
and the increased chance of cancer from swallowing or coming into direct contact with contaminated soils
were the main threats to human health if the soils remained untreated.
EPA's risk assessment showed that additional cancer risk and non-cancer health effects were probable if
the site was not cleaned up. Calculations were based on the likely amount of time various people would spend
at the site, their activity there, and the amount of contact they would have with contaminated resources.
The risk assessment calculated that without long-term site cleanup, future child residents would face a4 in 1,000
chance of developing an extra cancer case—primarily from swallowing or coming into direct contact with arsenic-
contaminated soils over a lifetime. In addition to the risk posed by contaminated soils, the potential contamination
of ground water and surface water threatened City water supplies. The risk assessment also calculated a hazard
index of 82 for potential non-cancer health effects from the contaminated soils around the treatment building.
Site Cleanup and Risk Management
Clearly, the risk assessment pointed out the necessity of further cleanup actions to protect Enterprise
residents and restore the safety of the Joseph Forest Products site. All cleanup actions have been
completed at the Joseph Forest Products site and cleanup goals have been met. EPA will continue to
monitor the ground water to ensure cleanup levels are maintained. Cleanup actions have included:
^ Removing and decontaminating the process equipment from the wood preservative
treatment building, demolishing the building, and excavating the soil beneath the building.
S Removing additional contaminated soil to an approved hazardous waste facility.
S Removing two underground petroleum tanks.
^ Sampling soil, ground water, and surface water to confirm that cleanup levels were achieved.
^ Limiting use of the immediate area surrounding the treatment building with deed restrictions.
The Rest of the Story: Superfund Cleanups
EPA uses the results of a risk
assessment to help decide whether
any long-term cleanup is needed at a
Superfund site. If the answer is "yes,"
the risk assessment also guides
decisions on which remedy would be
best suited to the site and the
surrounding community. EPA seeks
the community's opinions on the
cleanup approaches, and all cleanup
options are thoroughly investigated
before any decision is made.
The many cleanup technologies
in use at Superfund sites are
organized into two main categories: treat-
ment and containment.
Treatment technologies use
engineering approaches to reduce the
volume, toxicity, or mobility of the
contaminants.
Common treatment technologies
include destroying wastes by burning
them at high temperatures while
controlling the fumes; allowing wastes
to evaporate into an air stream that is
then treated and released; and injecting
soils with micro-organisms that digest
contaminants and result in less harmful
materials.
Containment approaches build
barriers that isolate contamination and
keep it from coming into contact with
people and the environment.
Common containment technologies
include constructing aprotective barrier,
or cap, over the contaminated area;
excavating the waste materials and
disposing of them in a securely designed
landfill; and building an underground
barrier that blocks, diverts, or captures
contaminated ground water.
In many cases, a combination of
treatment and containment is the best
solution. Engineers design the long-
term cleanup approach, and as cleanup
work progresses, the risk from
hazardous waste contamination
declines. If wastes are left at a site,
EPA re-examines the site every five
years after cleanup to make sure it is
still safe. Q
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•Superfund Today-Risk Assessment-
For More Information...
...on EPA's risk assessment process, or about a Superfund site in your
neighborhood, please contact the toll-free Superfund/RCRA Hotline at
1 -800-424-9346 or the Community Involvement Coordinator in the EPA
regional office for your state; their numbers are listed below. Your local
EPA office can tell you where you can go to review files on every Superfund
site in your area. This information may include the results of a risk assessment. Often, EPA
conducts community meetings to keep people who live near a site informed about site activities.
Region 1 CT, ME, MA, NH, Rl, VT (617) 565-3425
John F. Kennedy Federal Bldg., Rm. RPS-
74, Boston, MA 02203
Region 2 NJ, NY, Puerto Rico, Virgin Islands
(212)637-3671
290 Broadway, New York, NY 10007
Region 3 DE, DC, MD, PA, VA, WV (215) 566-3245
841 Chestnut St., Philadelphia, PA 19107
Region 4 AL, FL, GA, KY, MS, NC, SC, TN
Waste Management Division, Atlanta
Federal Center, 61 Forsyth Street, Atlanta,
GA 30303
AL, FL, GA, MS (800) 435-9234
KY, NC, SC, TN (800) 435-9233
For emergency responses: (800) 564-7577
Region 5 IL, IN, Ml, MN, OH, I/I// (312) 886-6685
Metcalfe Federal Bldg. 19th Floor, 77 West
Jackson Blvd., Chicago, IL 60604
Region 6 AR, LA, NM, OK, TX (214) 665-6617
Tower & Fountain Place, 1445 Ross Ave.
12th Floor, Dallas, TX 75202
Region 7 IA, KS, MO, NE (913) 551-7003 or
(800) 223-0425
726 Minnesota Ave., Kansas City, KS 66101
Region 8 CO, MT, ND, SD, UT, WY (303) 312-6600
999 18th St., Suite 500, Denver, CO 80202
Region 9 AZ, CA, HI, NV, U.S. Territories
(415)744-2178
75 Hawthorne St., San Francisco, CA 94105
Region 10 AK, ID, OR, WA (206) 553-1272
1200 6th Ave., Seattle, WA 98101
5-EPA
United States
Environmental Protection
Agency (5204G)
Washington, DC 20460
Official Business
Penalty for Private Use
$300
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