i,
RISK UPDATES
E
Number 5
September 1999
SK UPDATES is a
periodic bulletin prepared by EPA Region
I New England risk assessors to provide
information on new regional guidance.
RiskUpdates is distributed to contractors
supporting Superfund and RCRA,
regulators, and interested parties. Risk
assessment questions may be directed
to the following EPA scientists (area
code 617 unless otherwise noted):
Regional Risk Assessment Contact
Ann-Marie Burke 918-1237
Superfund
Human Health Risk Assessment
Ann-Marie Burke 918-1237
Cynthia Hanna 918-1446
Sarah Levinson 918-1390
Margaret McDonough 918-1276
Ecological Risk Assessment
Cornell Rosiu 918-1345
Patti Tyler (781) 860-4342
RCRA Corrective Action
MaryBallew 918-1277
Stephanie Carr 918-1363
Air Modeling
Brian Hennessey 918-1654
Combustion Risk Issues
Jui-YuHsieh 918-1646
Comparative Risk
Katrina Kipp 918-1082
Cost Benefit Analysis
Ronnie Levin 918-1716
Drinking Water
Maureen McClelland 918-1517
Air Risk Issues
Jeri Weiss 918-1568
ORD Technical Liaison
Steve Mangion 918-1452
EPA Region I, New England receives
additional ecological technical support
from Ken Finkelstein (918-1499) of the
National Oceanic Atmospheric
Administration (NOAA), and US Fish &
Wildlife (Steve Mierzykowski 207/827-
5938, Ken Munney 603/225-1411).
Editor
Sarah Levinson
Contents
RAGS PART D Page 1
COPC Selection Update Page 2
Exposure Point Concentration:
Ground Water Page 3
Adult Exposures to Lead Page 3
Combustion Risk Page 3
Health Threats to Children ....Page 4
Mercury Update Page 5
Strategy for PBT Pollutants....Page 6
Cumulative Exposure Project Page 7
Neurotoxicity Guidelines Page 8
Endocrine Disrupters Page 8
Tox Tidbits Page 9
EPA Web Sites Page 10
RAGS PART D
In January 1998, EPA released
"Part D" of the Human Health Risk
Assessment Guidance Series for
Superfund (RAGS). This marked
the fourth guidance in the RAGS
series. RAGS Part A contains
basic information for how to
conduct a human health risk
assessment and provides the
necessary background for RAGS
Part D. RAGS Part B provides
guidance on the development of
preliminary remediation goals and
RAGS Part C outlines the various
risk evaluations which should be
conducted after the remedial
investigation and baseline risk
assessments are complete
(particularly risks from remedial
alternatives). RAGS Part D
provides a standard method for
planning, reporting, and reviewing
human health risk assessments
and is expected to improve the
overall risk assessment process.
RAGS Part D was developed in
response to external criticisms
that risk assessments were not
transparent or consistent. As
such, development of a
standardized risk format was
identified as one of the Superfund
Administrative Reforms. A
national workgroup of EPA risk
assessors developed the guidance
which was reviewed by EPA,
State, DOD and DOE staff. RAGS
D consists of three basic
elements: 1. use of Standard
Tools, 2. Continuous
Involvement of the EPA Risk
Assessor, and 3. an Electronic
Data Transfer Element to a
National Superfund Database.
The Standard Tools includes the
Technical Approach for Risk
Assessment which indicates
where, in the CERCLA remedial
process, the risk assessor's input
and evaluations are necessary. It
is intended to ensure that risk
assessment requirements are
clearly defined and that the
appropriate planning will occur.
The Standard Tools also contain
the Standard Tables that clearly
and consistently document
important parameters, data,
calculations and conclusions from
the risk assessment. The
Standard Tables will not only
provide risk information in a
consistent format, but will also
clarify the assumptions and
increase the reader's ability to
understand the chosen approach.
Electronic templates for the
1
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Standard Tables are available
from EPA in LOTUSR and
EXCELR. For site specific risk
assessments, the Standard
Tables, related Worksheets and
supporting information should first
be prepared as interim
deliverables for EPA risk assessor
review, and later included in the
Draft and Final Baseline Risk
Assessment Reports.
RAGS Part D also emphasizes
early and Continuous
Involvement of the EPA Risk
Assessor from scoping through
completion and periodic review of
the remedial action. EPA risk
assessor involvement will improve
the reasonableness and
consistency of risk assessment
assumptions and conclusions. It
will also help ensure that
conclusions of the risk
assessment are appropriately
understood and applied to risk
management decisions.
The Electronic Data Transfer
Element, while still in
development, will store site-
specific risk information contained
in the Standard Tables, in a
National Superfund Database.
This component of RAGS D will
accomplish reporting
requirements, facilitate data
consistency review, and make
data readily available for
interested parties to review.
RAGS Part D became effective
January 1, 1998 and applies to all
Superfund risk assessments
(including those performed by
Federal Facilities) commencing
after this date. RAGS D applies
to all stages of the Superfund
RI/FS process including the
Record of Decision (ROD),
Explanation of Significant
Differences (ESDs), amended
RODs and five-year reviews. The
use of RAGS D is encouraged at
RCRA Corrective Action and
removal sites.
RAGS Part D can be obtained at:
www.epa.gov/superfund/programs/
risk/ragsd while questions on the
guidance can be directed to any
Regional risk assessor.
Written by Ann-Marie Burke
COPC Selection Process
Update
In a previous issue of the Risk
Updates Newsletter (Update #3,
8/95), EPA Region I addressed the
selection of chemicals of potential
concern (COPCs) for focusing risk
estimation. At this time, Region I
is updating the process in order to
reflect a change in the use of
readily available risk based
concentrations (RBCs) and
clarifying the role background data
plays in selecting COPCs.
EPA Region 9 Risk Based
Concentrations
EPA Region I is adopting EPA
Region 9 RBCs for the COPC
selection process, because Region
9 RBCs address the following
routes of exposure:
• Tap Water:
ingestion, and inhalation of
volatile organic compounds
(VOCs)
• Soil:
incidental ingestion,
inhalation of particulates and
VOCs, and dermal
absorption
• Ambient Air:
inhalation of particulates
and VOCs.
Region 9 RBCs should be used in
lieu of Region 3 RBCs in the
COPC selection process
according to the guidance
presented in the 8/95 Region I
Risk Update #3 Newsletter.
Exposure routes unique to the
Region 9 RBCs are dermal
absorption of contaminants, and
inhalation of VOCs and
particulates from soils. Region 9
RBCs also incorporate the latest
EPA dermal risk evaluation
procedures and are available from
the Region 9 web site (referred to
as Preliminary Remediation
Goals) at:
www.epa.gov/region09/waste/sfu
nd/prg/index.htm.
Background Data and Risk
Management
EPA Region I also seeks to clarify
that comparisons between site
and background levels of metals or
organic compounds (i.e., either
naturally occurring or
anthropogenic) may not be used to
eliminate any COPC from the risk
evaluation process. The objective
of the COPC selection process is
to focus the analysis on those
chemicals most likely to present a
hazard if exposure were to occur.
Chemicals present below
background concentrations may
still significantly contribute to the
total site risk and therefore should
be retained in order to conduct a
complete characterization of site
risk. Furthermore, EPA is
increasingly interested in
evaluations of cumulative risk (i.e.,
site-related risks and risks from
other sources) in seeking how
best to manage risk.
Evaluation of the nature and
magnitude of background levels of
risk is a very important tool for
risk management. EPA typically
does not require clean-up below
background. Background data
comparisons for compounds
contributing significantly to the
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overall risk level is very relevant
and could represent a cost-
savings by tailoring background
sample analyses to just the few
compounds in question. The
relevance of background levels of
contamination should be
discussed in the risk
characterization, uncertainty
section, or remedial response
objectives development. An EPA
workgroup is currently developing
national guidance on background
data collection and interpretation.
Written by Cindy Hanna
Clarification on the
Exposure Point
Concentration for
Ground Water Risk
Evaluation
As another matter of clarification
to a previous Risk Update (Update
#2, Aug. '94), EPA Region I
wishes to emphasize that the
highest temporal average
concentration from a single well
may be used as the reasonable
maximum exposure (RME) point
concentration for use in Superfund
Risk Assessments to evaluate
risk to potential groundwater
users. The RME ground water
concentration is to be based on
the highest of the temporal
average concentrations of each
contaminant in each well provided
that a sufficient number of
sampling events have been
obtained over a sufficient period of
time so as to characterize a
temporal average exposure
concentration for a given well. It
is not possible to specify the
minimum number of sampling
events needed to characterize a
temporal average as each site will
be subject to different conditions
(ground water velocities, seasonal
fluctuations in the water table,
etc.). In situations in which an
EPA risk assessor in conjunction
with an EPA hydrogeologist
conclude that insufficient data
exists upon which to generate a
temporal average concentration,
then EPA Region I advocates the
maximum groundwater exposure
point concentration be utilized for
RME risk evaluation purposes.
For questions on this approach,
contact any Superfund risk
assessor.
Adult Exposure to Lead
in Soil: Update
EPA's Technical Review
Workgroup (TRW) developed a
methodology for evaluating the
hazard potential resulting from
adult exposures to lead in soil. The
TRW methodology results in an
estimate of the fetal blood lead
concentration among women
exposed to lead contaminated
soils. The basis of the approach
recommended by the TRW stems
from the relationship between the
soil lead concentration and the
maternal blood lead concentration.
Fetal blood lead concentrations
which are proportional to maternal
blood lead concentrations can then
be estimated. Fetuses are
considered a highly sensitive
population with respect to adverse
effects of lead during development.
The blood lead level of concern for
a fetus is 10 ug/dL. EPA's health
based goal is to limit the risk of
exceeding the level of concern to
no more than 5%. The approach is
similar to the slope factor
approach proposed by Bowers et
al, 1994.
The TRW published the
methodology in "Recommenda-
tions of the Technical Review
Workgroup for Lead, an Interim
Approach to Assessing Risks
Associated with Adult Exposures
to Lead in Soil", December 1996.
This report is available on the
Internet at the TRWs homepage:
www.epa.qov/superfund/proqrams
/lead/index, htm. The report
describes the basic algorithms
used in the methodology and
default parameter values that can
be used when site-specific data
are lacking. Consultation with the
TRW workgroup (via the web) on
the applicability of the adult lead
methodology to other populations
(such as adolescents) is strongly
advised.
References
Bowers, T.S., Beck, B.D., Karam,
H.S., 1994. Assessing the
relationship between environ-
mental lead concentrations and
adult blood lead levels. Risk
Analysis 14:183-89.
Written by Margaret McDonough
Risk Assessment
Protocol for Hazardous
Waste Combustors
EPA's Office of Solid Waste
(OSW) has released a draft
guidance entitled: Human Health
Risk Assessment Protocol for
Hazardous Waste Combustion
Facilities, Volumes 1, 2, and 3
(EPA530-D-98-001A,B,C July
1998). This supercedes the 1994
OSW draft Guidance for
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Performing Screening Level Risk
Analyses at Combustion Facilities
Burning Hazardous Waste. The
guidance develops an
understanding of the potential
human health risks associated
with the emissions from
hazardous waste combustors.
The guidance includes specific
parameters, pathways and
algorithms that evaluate both
direct and indirect exposure and
risk. It reflects other pertinent
EPA risk guidances including the
Exposure Factors Handbook
(1997), Mercury Report to
Congress (1997), and Estimating
Exposure to Dioxin-Like
Compounds (1994).
OSW intends to use risk
estimates generated in
accordance with the guidance for
the permitting of RCRA hazardous
waste combustors to ensure they
are protective of human health and
the environ-ment. (An ecological
risk companion to the human
health risk protocol is anticipated
for release later this year.)
It is recommended that the
Human Health Risk Protocol for
Hazardous Waste Combustors be
used in conjunction with the OSW
risk burn guidance on Collection
of Emissions Data to Support
Site-Specific Risk Assessments
at Hazardous Waste Combustion
Facilities (EPA 530-D-98-002
August 1998). Since the human
health risk protocol was released
for external peer review, it may
undergo some modification in the
future. Readers can access the
draft human health risk protocol
(www.epa.qov/epaoswer/hazwast
e/combust/risk.htm)
or obtain a hard copy by calling
the RCRA hotline at (800) 424-
9346.
Written by Jui-Yu Hsieh
Addressing
Environmental Health
Threats to Children
In September 1996, EPA released
"Environmental Health Threats to
Children" (available on the web at
www.epa.gov/epadocs/child.htm)
detailing health threats faced by
children from toxics in the
environment. Key findings of the
report highlight differences between
a child's exposure and resulting
health risks vis a vis an adult's.
For example, children are known to
differ from adults in terms of the
amount and types of exposure,
physical sensitivity and
vulnerability to chemical agents,
and the likelihood of lifelong
effects. EPA called for a new
national agenda to protect children
from these risks more
comprehensively than before.
Shortly afterwards, EPA created a
new Office of Children's Health
Protection to ensure that infant and
children's health protection are
consistently and explicitly
integrated into all EPA actions.
President Clinton signed an
Executive Order on children's
health in April of 1997, calling
healthy children and strong families
fundamental to the future of our
nation and emphasizing that
protection of the environment is
critical to our children's health.
Two Washington based subcom-
mittees were established in
response to the Administration's
call: one was tasked with
increasing public access to federal
government sponsored research on
environmental health and safety
risks to children, and the other
identified public outreach activities
that would protect children's
environmental health and safety.
Topping the list of children's health
concerns are: asthma,
unintentional injuries,
developmental disorders, and
childhood cancers.
In January 1999, President
Clinton's budget proposal sought
$68 million for fighting asthma
alone, just one of the top
children's health priorities. Most
of the money - $50 million - would
be used for competitive state
grants to identify and treat
asthmatic children who are served
by Medicaid. Two million dollars
would be used to fund asthma
related research and $8.4 million
would be used to establish school-
based asthma programs that
reduce or eliminate allergens and
irritants. In addition, the budget
proposal seeks to establish an
asthma surveillance program,
expand support for state and local
public health action, promote
clinician and patient
implementation of national
guidelines for reducing
environmental risks that worsen
asthma, and reduce children's
exposure to environmental
tobacco smoke.
Despite concerted efforts, current
statistics about increasing rates of
asthma among young children and
unchanging rates of lead poisoning
in many urban areas in New
England has caused serious
concern in our region. EPA-New
England has begun our own
campaign to reduce environmental
health risks to children. To date
we have invested nearly $400,000
in grants and other aid to
communities and non-govern-
mental organizations to help
develop programs that protect
children from diseases caused by
environmental factors. We are
engaged in neighborhood projects
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throughout New England (see
spotlight below on Manchester,
NH) that include relandscaping
yards to make them lead-free for
children, counseling families
about ways to make their homes
safer, and educating daycare
providers about lead poisoning
prevention. We have funded
programs in New England to help
smokers learn the importance of
not smoking around children in
their care, and sponsored regional
conferences on asthma.
We have built new partnerships
with other federal and state
agencies to expand our ability to
help families find resources
-including health insurance-for
their children. And we are looking
creatively at some of our
enforcement tools to help reduce
environmental health threats to
children. For example,
companies choosing to offset a
portion of an environmental fine
may implement a Supplemental
Environmental Project benefit-ting
the local community.
Spotlight:
Manchester, NH - A Child
Health Champion Community
Manchester, New Hampshire is
one of eleven Child Health
Champion national pilot
communities engaged in an
aggressive local campaign to
reduce environmental health risks
facing its children. With the help
of $135,000 in EPA funding from
the Office of Children's Health
Protection, a group of
organizations representing a
broad spectrum of the Manchester
community-from the health
department to a local theater
group-was formed to help the
city's children have a strong and
healthy future.
Manchester is an old industrial
city, and many of its houses are in
poor condition. The city has the
highest rate of childhood lead
poisoning in New Hampshire, and
the largest percentage of
school-age children with asthma.
Manchester also has the largest
and fastest growing immigrant
population in the state which
complicates efforts to establish an
ongoing dialogue about
environmental health among its
residents. Nevertheless, both the
city's mayor and its government
have made a strong commitment to
charting a course for Manchester
that provides its youngest
population with the greatest
possible opportunities to prosper.
The city's Child Health Champion
project offers young families
information about how to create a
healthy home, right from the start.
For smokers who want to quit, the
project offers free smoking
cessation classes, so that the
children in close contact with
adults who smoke will stop
suffering from the effects of second
hand smoke exposure. The project
also provides in-home services to
reduce asthma allergens and lead
dust. In conjunction with allergen
and lead dust removal, the local
chapter of the Audubon Society is
offering free after school eco-health
programs to any child who needs a
safe place to go while their homes
are being cleaned. The
community's theater group is
producing a show that helps young
families understand what they can
do to reduce children's risk from
environmental factors. Working
together, Manchester's Child
Health Champions have become a
national model, demonstrating
how a community can make a
difference for their children.
Written by Alice Kaufman, Office
of the Regional Administrator
Mercury Update
Interest in mercury contamination
has been growing as has the
awareness of the impacts of
mercury deposition. Now, all six
New England states have fish
advisories warning against eat-ing
fresh water fish. Most of these
warnings target sensitive
populations, women of child-
bearing age, pregnant women, and
children.
Several activities have taken place
fairly recently designed to help
reduce or eliminate mercury
emissions and which reflect the
latest understanding of the
hazards mercury poses to human
health. The following represents a
brief summary of these activities.
Efforts to Control Mercury
In December 1997, EPA released
a Mercury Study Report to
Congress identifying the major
sources of mercury, costs for
controlling mercury emissions,
and the impacts and health effects
attributed to mercury exposure.
This report helped to pave the way
for inclusion of mercury as one of
the twelve persistent,
bioaccumulative, and toxic (PBT)
pollutants that EPA is targeting for
risk reduction (see related article
in this issue of Risk Updates). A
national action plan for controlling
mercury emissions has already
been developed as part of the PBT
Strategy. In addition to the
emission reductions from sources
such as municipal and medical
waste incinerators, the plan also
supports development of tools to
link air emissions with water
quality impacts.
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Closer to home, the New England
states and the Eastern Canadian
Provinces have been working
together and in Feb. of 1998
released "Mercury Report for the
Northeast States and Eastern
Canadian Provinces." This led to
a joint resolution between the New
England Governors and the
Eastern Canadian Premiers in
which a Regional Mercury Action
Plan was adopted. The Regional
Action Plan identified 40 specific
actions that the states and
provinces will take to meet the
goal of "virtual elimination of
anthropogenic sources of
mercury."
EPA is also encouraging voluntary
efforts to reduce mercury
emissions. As an example, EPA
has developed a Memorandum of
Understanding with the American
Hospital Association (AHA)
calling for the virtual elimination of
mercury in hospital waste
streams. EPA New England is
working with local hospitals and
State Hospital Associations to
reduce mercury emissions from
this sector.
Methyl Mercury Reference
Dose
The toxic effects of mercury
poisoning were well known at the
turn of the century, the term "mad
as a hatter" was coined to
describe the effects from mercury
poisoning. Epidemics of methyl
mercury poisoning in Japan and
Iraq resulted from high-dose
exposures to methyl mercury. In
these epidemics, both adults and
developing fetuses were adversely
impacted by exposure to methyl
mercury. The epidemics
demonstrated that neurotoxicity is
the health effect of greatest
concern and that the developing
fetus was the most sensitive
receptor.
Data from the Iraqi methyl mercury
epidemic was used by EPA in the
revision of the oral reference dose
for methyl mercury. Formerly,
EPA had based the oral reference
dose for methyl mercury on
neurological effects observed in
adults. Now, using data from the
Iraqi study on the neurological
effects noted in the fetus, EPA
established the oral reference dose
at 0.1 ug/kg/day. The reference
dose for methyl mercury was also
significant in that it is one of the
few compounds for which the
benchmark dose (BMD)
methodology has been used to
establish the reference dose.
[Information on the benchmark
dose approach can be obtained in
The Use of Benchmark Dose
Approach in Health Risk
Assessment published by EPA's
Office of Research and
Development EPA/630/R-94/007
Feb. 1995 or on the web at
www.epa.gov/nceawww1/bmds.ht
m].
Two additional epidemiological
studies from the Seychelles and
the Faeroe Islands, are
investigating developmental and
neurological toxicity resulting from
fetal exposure to methyl mercury
at exposure levels that are
common to fish eating populations.
While EPA decided not to
incorporate the findings from these
epidemiological studies in the RfD
for methyl mercury (since much of
the data was unpublished or had
not been subjected to rigorous peer
review at the time), efforts are now
underway to re-evaluate the health
effects of human exposure to
methyl mercury. In Nov. 1998 the
Office of Science and Technology
Policy of The White House
organized a conference to evaluate
these recent epidemiological
studies. They concluded that both
studies from the Seychelles
Islands and from the Faeroe
Islands were scientifically
conducted and well designed.
Additionally, the National
Academy of Sciences (NAS) will
soon begin a comprehensive
mercury study and prepare
recommendations on an
appropriate reference dose within
the next 18 months.
EPA plans to await the NAS report
prior to re-evaluating the current
RfD for methyl mercury. In the
meantime, EPA's Office of
Research and Development will
issue interim guidance in order to
provide stability and consistency
to programs evaluating risks from
methyl mercury.
Note: This article was based in
part on a paper presented by
Glenn Rice of EPA's National
Center for Environmental
Assessment. If you would like a
copy of "Derivation of US EPA's
Methyl Mercury RfD," please
contact Jeri Weiss.
Written by Jeri Weiss
EPA's Strategy for
Reducing Priority
Persistent,
Bioaccumulative and
Toxic Pollutants
In May 1998, EPA released a
multimedia strategy to reduce
persistent, bioaccumulative, and
toxic (PBT) pollutants in the
environment. The goal of the
strategy is to identify and reduce
risks to human health and the
environment from existing and
future priority PBT pollutants using
all tools available to the EPA
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(voluntary, regulatory, research,
etc.) Persistent, bioaccumulative
and toxic pollutants share the
character-istic of being highly
toxic, long-lasting substances
that can build up in the food chain
to levels that are harmful to
human and ecosystem health.
They present an additional
challenge to EPA in that they
readily transfer between the air,
water, and land, they can travel
great distances, and linger for
generations in people and the
environment.
EPA has identified an initial list of
12 PBTs (aldrin/dieldrin,
benzo(a)pyrene, chlordane, DDT,
hexachlorobenzene, alkyl-lead,
mercury and compounds, mirex,
octachlorostyrene, PCBs, dioxins
and furans, and toxaphene) and
will be screening and selecting
additional PBT pollutants in the
future. EPA's strategy will
include the development and
implementation of action plans for
each PBT. To date, EPA has
developed an action plan for
mercury. Additional information
on EPA's PBT strategy can be
found on the web at
www.epa.gov/opptintr/pbt.
Summarized from EPA's Web
page by Ronnie Levin
Cumulative Exposure
Project: Air Toxics
The Cumulative Exposure Project
(CEP), initiated in 1994 by EPA's
Office of Policy, seeks to evaluate
the combined exposures to
multiple pollutants through three
different pathways- air, food, and
drinking water. To date, EPA has
focused Agency efforts on air
toxics and the potential they
present for exposure via inhalation.
In order to develop estimates of
concentrations of toxic air
pollutants across the United
States, EPA has developed a new
air quality modeling tool, known as
the Assessment System for
Population Exposure Nationwide
(ASPEN). ASPEN is based on
standard EPA air quality modeling
methods, and significantly expands
the scope of such models by
including the capability to model a
large number of pollutants across
the entire continental United
States.
EPA is using the ASPEN model to
better characterize air toxics from
a national perspective and to help
set priorities to reduce emissions
of air toxics that may be impacting
public health. EPA also intends to
use the ASPEN model to track
ambient air toxic concentration
trends over time and to measure
progress toward meeting risk
reduction goals.
Assumptions and Limitations of
the ASPEN Model
The ASPEN model is a dispersion
model which estimates ambient
concentrations of air pollutants in
two basic steps: first, pollutant
emissions are estimated; and
second, a computer model
simulates the impacts of winds and
other atmospheric processes on
the pollutants once emitted. Like
any computerized dispersion
model, ASPEN relies on a number
of assumptions and
approximations in estimating air
toxics concentrations rather than
on actual measurements of
concentration. The precision of
the model is limited by
uncertainties in the quantities of
pollutants emitted, locations at
which pollutants are emitted, and
the model's mathematical repre-
sentations of what happens to
pollutants after they are emitted.
It should be noted that the model
estimates ambient concentrations
of air toxics and not an individual's
exposure to those pollutants.
1990 Model Characterization
Results
As part of the Cumulative
Exposure Project, EPA estimated
concentrations of 148 air toxics
across the continental United
States in 1990. Comparison of the
1990 modeled concentrations to
the available 1990 air toxics
monitoring data showed that the
study's modeled concentrations
are generally of the correct
magnitude, and have a tendency
to underestimate 1990
concentrations.
Analysis of the 1990 modeling
results, published in the
Environmental Health
Perspectives (May 1998), found
that the 1990 modeled
concentrations of several airtoxics
were high throughout the United
States in comparison to
previously-defined health
benchmarks. Thirteen toxic air
pollutants had modeled concen-
trations that exceeded bench-mark
values for more than half of the
country; for eight of these air
toxics, this result was attributable
to the impact of 1990 man-made
emissions, while for the other five
air toxics, this result was
attributable to background
7
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concentrations. EPA believes
that this initial characterization
reinforces the importance of
continuing to reduce air toxics.
It is important to note that these
modeling results are based on
1990 emissions information, and
therefore should not be interpreted
as representative of current
conditions. Since 1990, EPA,
states and local govern-ments
have developed standards to
reduce air toxics.
Future Applications of the
ASPEN Model
EPA's Office of Air and Radiation
is working with state and local
agencies to update and improve
its information on air toxics
emissions, and plans to have a
final 1996 National Toxics
Inventory (NTI) completed by
October 1999. In conducting
national air toxics assessments,
as part of its Air Toxics Program,
EPA will use the ASPEN model
with the updated NTI to estimate
1996 air toxics concentrations
across the continental U.S.
Through the remainder of the year,
EPA will incorporate the NTI data
into the ASPEN model and
analyze modeled results. The
modeling effort and subsequent
follow-up work on public health
implications in this area will help
prioritize the Agency's efforts to
reduce emissions of air toxics
that may be impacting public
health.
More information about the
Cumulative Exposure Project can
be found at:
www.epa.aov/cumulativeexposure
Summarized by Susan Lancey,
Office of Ecosystem Protection
from EPA's Introduction to
Estimated 1990 Air Toxics
Concentrations from EPA's
Cumulative Exposure Project.
Neurotoxicity Risk
Assessment Guideline
Available
EPA's neurotoxicity risk
assessment guideline, published in
May 1998, establishes principles
and procedures to guide EPA
scientists in all program offices in
evaluating environmental
contaminants that may pose a
hazard to the nervous system. The
neurotoxicity risk assessment
guideline supple-ments the library
of guidelines previously available on
carcinogenicity, mutagenicity,
chemical mixtures, developmental
toxicants, exposure assessment,
reproductive toxicity and ecological
risk assessment. The
neurotoxicity guideline addresses
the special vulnerability of the
nervous system, particularly that
of infants and children, to
environmentally relevant chemicals,
and provides guidance for the
interpretation of data from
developmental and reproductive
studies involving the assessment of
nervous system structure and
function. While intended to
increase consistency in these
evaluations, the guideline
emphasizes that risk assessments
will continue to be done on a
case-by-case basis. The
neurotoxicity risk assessment
guideline can be obtained on the
web at:
www.epa.qov/ncea/nurotox.htm.
Information obtained from EPA's
Web Site.
Endocrine Disrupters
Chemicals which interfere with
endocrine system functioning
(endocrine disrupters) have
concerned the EPA for some time.
A variety of human health and
ecological effects have been
attributed to endocrine disrupters
such as behavioral changes,
adverse reproductive, develop-
mental, and carcinogenic effects.
A difficulty remains in that we do
not currently know which
chemicals interfere with endocrine
system function, the extent to
which problems exist, or how
widespread these compounds
may be in the environment.
In 1996,the passage of the Food
Quality Protection Act (FQPA)
and the Safe Drinking Water Act
(SDWA) mandated EPA develop
a screening and testing strategy
for endocrine disrupters by 1998
and implement the strategy by
August 1999. The legislation cites
the Federal Insecticide, Fungicide,
and Rodenticide Act (FIFRA) and
the Toxic Substances Control Act
(TSCA) as the two statutes under
which EPA will implement an
endocrine screening and testing
strategy and also provides
supplementary authority to require
industry conduct the necessary
testing.
Thus in October 1996, EPA
commissioned a committee to
address the difficult technical and
policy issues associated with
endocrine disrupter screening and
testing known as the Endocrine
Disrupter Screening and Testing
Advisory Committee (EDSTAC).
The EDSTAC has proposed a
conceptual framework upon which
a proposed screening system is
based.
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The EDSTAC Conceptual
Framework places activities in an
ordered sequence. The elements
of this sequence include: a)
priority setting, which includes the
sorting and prioritization of
chemical substances and
mixtures for evaluation in
screening and/ortesting batteries;
b) screening to detect chemical
substances and mixtures capable
of acting on endocrine systems;
and c) testing to confirm,
characterize, and quantify the
nature of the endocrine disrupting
properties of the chemical
substances and mixtures
identified by prior information
and/or screening. EDSTAC also
recommended a communication
and outreach strategy be
developed to inform the public of
results of the screening and
testing program.
Information obtained from EPA's
endocrine disrupter web site:
www. eoa. aov/optytintr/ODDtendo/in
dex.htm.
Tox Tidbits
While it is always recommended
to check EPA's web version of
IRIS (Integrated Risk Information
System) at www.epa.gov/iris
for the most up-to-date information
regarding Agency verified
chemical toxicity, Tox Tidbits is
an attempt to bring recent or often
overlooked changes to light. A
comprehen-sive summary of
recent additions and changes to
the IRIS database can readily be
accessed by selecting the
"What's New" icon on the web
page. The following represents
examples of recent changes or
often overlooked changes in
cancer slope factors or unit risk
values and reference doses or
reference concentra-tions.
Slope Factors
Beryllium. As of March 1998,
EPA withdrew the Agency oral
slope factor for beryllium. Upon
review of the original data, EPA
decided that there was not a
statistically significant increase in
tumors in the treated group relative
to controls. EPA withdrew the oral
slope factor while leaving the
inhalation unit risk in the IRIS
database. EPA Region I therefore
at this time, only requires
quantitation of the carcinogenic
potential posed by exposure to
beryllium via the inhalation pathway
- not the oral pathway. Evaluation
of non-carcinogenic health threats
posed by beryllium should not be
overlooked via the oral and
inhalation exposure pathways.
Doses/
Reference
Concentrations
Napthalene: As of Sept. 1998,
EPA added a verified oral
reference dose for napthalene
corresponding to 2 x 10~2
mg/kg/day and an inhalation unit
risk of 3 x 10~3 mg/m3. For non-
carcinogenic PAHs lacking a
current EPA reference dose or
concentration, it is EPA Region I
policy to adopt the reference dose
or concentration of a structurally
similar PAH for hazard evaluation
purposes.
Chromium VI: As of Sept. 1998,
EPA updated the oral reference
dose (now 3 x 10"3 mg/kg/day) and
added two new inhalation unit risk
values corresponding to 8 x 10"6
mg/m3 for chromium*6 acid mists
and dissolved aerosols and a
second inhalation unit risk of 1 x
10~4 mg/m3 for exposure to
chromium*6 particulates.
Manganese: As indicated in the
Risk Update #4 ( Nov. 1996) the
oral reference dose for manganese
corresponding to 1.4 x 10~1
mg/kg/day represents an
allowable level for the TOTAL oral
intake. EPA Region I advocates
that an adjustment for the dietary
contribution be subtracted from
this allowable intake as discussed
in the IRIS file. The resulting non-
dietary reference dose of 7 x 10~2
mg/kg/day should be used for
Superfund risk evaluations
involving soil exposure. However,
for exposures to drinking water, as
stated in the IRIS file, a
modification factor of 3 should be
applied to the non-dietary
reference dose resulting in an
effective drinking water reference
dose of 2.4 x 10"2 mg/kg/day.
Compounds Lacking an IRIS
Value
It is EPA Region I Superfund
policy to contact the Superfund
Technical Support Center when
agency verified toxicity values are
lacking in the IRIS database. The
Tech Support Center has access
to non-verified toxicity criteria
available from the Health Effects
Assessment Summary Tables
(HEAST), other EPA program
offices, and chemical specific
reviews performed on request.
While there is talk brewing of
placing HEAST values on the
Internet, at present they can only
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be obtained via the Superfund
Tech Support Center. Those
external to EPA may contact the
Tech Support Center directly at
(513) 569-7300 for Superfund Site
related inquiries. Other inquiries
(not specific to a Superfund Site)
should be directed to one of the
Regional Risk Assessors listed
on the cover of the newsletter.
Several provisional (non-EPA
verified) dose-response values
that have been released by the
Tech Support Center but which
the Region I Office does not
endorse for use in quantitative risk
assessments include provisional
oral RfDs for copper and iron.
Reasons for not using provisional
oral reference doses for copper
and iron stem from the fact that
they were based on
concentrations needed to protect
against a deficiency of the
compound, rather than on
quantitative estimates related to
the hazard posed by
overexposure to the compound.
Information compiled by Sarah
Levinson
EPA Web Sites of
Interest
EPA is increasing the amount of
information available on the
Internet daily. To assist you in
locating many useful risk related
information distributed by EPA,
the following list of web sites was
compiled. It is not a complete
listing of the available resources,
merely a helpful beginning.
1. EPA's Superfund Risk page:
www.epa.qov/superfund/proqrams/r
isk. This site contains all of the
Human Health Risk Assessment
Guidelines for Human Health (
RAGS Parts A, B, C, and D - the
new standardized reporting format)
and the Superfund Ecological Risk
Guidance. In addition, EPA's Soil
Screening Levels, and Guidance on
the Use of Probabilistic Risk
Evaluation and Monte Carlo
Analysis can be found as well as
links to numerous other related
sites.
2. Region 9 Guidance for
Preliminary Remediation Goals
(used for COPC selection by
Region I):
www.epa.gov/reqion09/waste/sfund
/prq/index.htm.
3 EPA Region I Risk Updates:
www.epa.gov/reqionQ1/remed/risku
pdates.html.
4. Integrated Risk Information
System (IRIS) - Database of current
EPA verified toxicity information:
www.epa.gov/iris.
5. EPA lead models (Integrated
Exposure Uptake Biokinetic Model
or IEUBK for young children, and
Recommendations of the
Technical Review Workgroup for use
of a slope factor approach for
evaluating adult exposures to lead):
www.epa.gov/supe rfund/programs/l
ead.
6. A multitude of EPA human
health and ecological health related
publications such as the Exposure
Factors Handbook
www.epa.gov/ncea/exposfac.htm
7. EPA risk assessment
guidelines, benchmark dose
methodology, chemical specific
information, and links to risk related
sites can be found on EPA's
National Center for Exposure
Assessment homepage:
www.epa.gov/ncea.
8. Indoor air screening and risk
calculations, vapor intrusion into
buildings (Johnson and Ettinger
Model):
www.epa.gov/superfund/proqrams
/risk/airmodel/johnson ettinqer.ht
m.
9. Ecotoxicity thresholds for
screening:
www.epa.gov/superfund/resource
s/ecotox.
10. Wildlife exposure factors
handbook:
www.epa.qov/nceawww1/wefh.ht
m.
Information compiled by Mary
Ballew
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