[Federal Register Volume 65, Number 31 (Tuesday, February 15, 2000)]
[Notices]
[Pages 7550-7552]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 00-3492]


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ENVIRONMENTAL PROTECTION AGENCY

[FRL-6537-6]


Superfund Probabilistic Risk Assessment to Characterize 
Uncertainty and Variability

AGENCY: Environmental Protection Agency.

ACTION: Notice of availability with request for comment.

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SUMMARY: The Environmental Protection Agency (EPA) has developed and is 
requesting public comment on a draft guidance entitled ``Risk 
Assessment Guidance for Superfund Volume 3 Part A: Process for 
Conducting Probabilistic Risk Assessment (RAGS 3A).'' It is available 
electronically on the Internet at http://www.epa.gov/superfund/pubs.htm#r. RAGS 3A addresses the technical and policy issues 
associated with the use of probabilistic risk assessment (PRA) in the 
EPA hazardous waste sites cleanup program, commonly known as Superfund. 
PRA, if applied appropriately, can better characterize uncertainty and 
variability in the risk estimates than the traditional point estimate 
approach. The guidance presents a recommended tiered process for 
conducting both human health and ecological PRA using Monte Carlo 
analysis, with emphasis on applying sensitivity analysis to identify 
important sources of variability and uncertainty in risk estimates, 
applying frequency distributions to characterize variability in 
exposure, and quantifying uncertainty in the mean contaminant 
concentration. The draft RAGS 3A should not be used or cited until it 
is finalized. RAGS 3A provides guidance to EPA staff and also to the 
public and to the regulated community on how EPA generally intends that 
the PRA be implemented to evaluate risk at more complex Superfund sites 
addressed under the Comprehensive Environmental Response, Compensation, 
and Liability Act of 1980 (CERCLA). The guidance is designed to 
describe EPA's national policy on the use of PRA. PRA is not expected 
to be relevant at every site. The document does not substitute for 
EPA's statutes or regulations, nor is it a regulation itself. Thus, it 
cannot impose legally-binding requirements on EPA, States, or the 
regulated community. EPA may change this guidance in the future, as 
appropriate.
    Further, Executive Order 13132, entitled ``Federalism'' (64 FR 
43255, August 10, 1999), requires EPA to develop an accountable process 
to ensure ``meaningful and timely input by State and local officials in 
the development of regulatory policies that have federalism 
implications.'' ``Policies that have federalism implications'' is 
defined in the Executive Order to include regulations and regulatory 
policies that have ``substantial direct effects on the States, on the 
relationship between the national government and the States, or on the 
distribution of power and responsibilities among the various levels of 
government.''
    RAGS 3A does not have federalism implications. It will not have 
substantial direct effects on the States, on the relationship between 
the national government and the States, or on the distribution of power 
and responsibilities among the various levels of government, as 
specified in Executive Order 13132. As explained above, RAGS 3A does 
not impose legally-binding requirements on the States. It is a 
technical risk assessment guidance which discusses a statistical risk 
assessment approach that may be used at more complex Superfund sites. 
Thus, the requirements of section 6 of the Executive Order do not apply 
to RAGS 3A.

DATES: You may submit comments until April 21, 2000. Comments received 
after

[[Page 7551]]

that date will be considered to the extent feasible; however, EPA will 
not delay finalizing the guidance in order to accommodate late 
comments.

ADDRESSES: You are invited to submit written comments to: EPA, 
Superfund Docket RAGS 3A-2, Mail Code 5202G, Ariel Rios Building, 1200 
Pennsylvania Avenue, N.W., Washington, DC 20460. For cost savings the 
draft RAGS 3A document is available electronically on the Internet and 
EPA plans to print the document only after it is finalized. The 
Superfund Docket containing the RAGS 3A document and public comments is 
physically located at 1235 Jefferson Davis Highway, Crystal Gateway I 
Building street level, Arlington, Virginia. The docket is available for 
inspection between 9:00 a.m. and 4:00 p.m., Monday through Friday, 
excluding Federal holidays. Appointments to review the docket can be 
made by calling (703) 603-9232. The public may copy a maximum of 266 
pages from the docket free of charge, however a charge of 15 cents will 
be incurred for each additional page, plus a $25.00 administrative fee.

FOR FURTHER INFORMATION CONTACT: S. Steven Chang, Office of Emergency 
and Remedial Response (5204G), U.S. Environmental Protection Agency, 
Ariel Rios Building, 1200 Pennsylvania Avenue, N.W., Washington, DC 
20460, at (703) 603-9017, by E-Mail at [email protected], or the 
RCRA/Superfund Hotline at (800) 424-9346 (in the Washington, DC 
metropolitan area, (703) 412-9810). The Telecommunications Device for 
the Deaf (TDD) Hotline number is (800) 553-7672 (in the Washington, DC 
metropolitan area, (703) 412-3323).

SUPPLEMENTARY INFORMATION:

Introduction

    The U.S. Environmental Protection Agency (EPA) responds to releases 
and threatened releases of hazardous substances under the authority of 
CERCLA. Regulations governing such responses are found in the National 
Oil and Hazardous Substances Pollution Contingency Plan or NCP. The 
process for remedy selection in the NCP generally involves performance 
of a remedial investigation to identify the nature and extent of 
contamination at National Priorities List sites. In general, sampling 
results and site observations obtained in the field are used in the 
baseline risk assessment to identify specific contaminants and exposure 
pathways of concern and to determine whether remedial action is 
warranted.
    Today's Federal Register notice introduces a draft guidance on use 
of a tool which could evaluate the uncertainty and variability 
associated with risk estimates developed as part of the baseline risk 
assessment for hazardous waste sites. The RAGS 3A document builds upon 
basic concepts of risk assessment outlined in the RAGS Volume 1 (U.S. 
EPA, 1989),\1\ the ``Guiding Principles for Monte Carlo Analysis'' and 
the ``Policy for Use of Probabilistic Analysis in Risk Assessment'' 
(U.S. EPA, 1997).\2\ PRA is not a requirement, and will not be 
appropriate at many sites. The guidance focuses on Monte Carlo analysis 
as a method of quantifying uncertainty and variability in risk. 
Primarily targeted toward the risk assessors, it is intended to be most 
accessible to those readers who are familiar with risk assessment and 
basic statistic concepts. The development of a PRA could involve 
significant investment of time by the risk assessor and risk manager to 
determine the extent and scope of the assessment. A tiered approach to 
PRA is advocated, beginning with evaluating the results of a point 
estimate approach. Important considerations include the time required 
to perform the PRA, the additional resources involved in developing the 
PRA, the available data on exposure that will be used in the 
assessment, and the value added by conducting the PRA.
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    \1\ U.S. EPA, 1989, Risk Assessment Guidance for Superfund: 
Volume 1: Human Health Evaluation Manual, Part A, Interim Final. 
EPA/540/1-89/002. Office of Emergency and Remedial Response, 
Washington, DC. NTIS PB90-155581.
    \2\ U.S. EPA, 1997, ``Guiding Principles for Monte Carlo 
Analysis.'' EPA/630/R-97/001. Office of Research and Development 
Risk Assessment Forum, Washington, DC.
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Background

    Probabilistic risk analysis, as exemplified by Monte Carlo 
analysis, has been in use since 1946. However, the application of PRA 
to human health and ecological risk assessment is a more recent 
application. As a result, the Agency believes that those using PRA 
analysis would benefit from development of additional guidance.
    In 1997, the EPA announced the ``Policy for Use of Probabilistic 
Analysis in Risk Assessment at the U.S. EPA'' (U.S. EPA, 1997), 
indicating the Agency's interest in probabilistic analysis in human 
health and ecological risk assessment. This 1997 policy states that 
``It is the policy of the U.S. Environmental Protection Agency that 
such probabilistic analysis techniques as Monte Carlo analysis, given 
adequate supporting data and credible assumptions, can be viable 
statistical tools for analyzing variability and uncertainty in risk 
assessments. As such, and provided that the conditions described below 
are met, risk assessments using Monte Carlo analysis or other 
probabilistic techniques will be evaluated and utilized in a manner 
that is consistent with other risk assessments submitted to the Agency 
for review or consideration. It is not the intent of this policy to 
recommend that probabilistic analysis be conducted for all risk 
assessments supporting risk management decisions. Such analysis should 
be a part of a tiered approach to risk assessment that progresses from 
simpler (e.g., deterministic) to more complex (e.g., probabilistic) 
analyses as the risk management situation requires. Use of Monte Carlo 
or other such techniques in risk assessments shall not be cause, per 
se, for rejection of the risk assessment by the Agency. For human 
health risk assessments, the application of Monte Carlo and other 
probabilistic techniques has been limited to exposure assessments in 
the majority of cases. The current (1997) policy, Conditions for 
Acceptance and associated guiding principles are not intended to apply 
to dose response evaluations for human health risk assessment until 
this application of probabilistic analysis has been studied further. In 
the case of ecological risk assessment, however, this policy applies to 
all aspects including stressor and dose-response assessment.''
    Based on this (1997) Policy the Superfund program is developing 
guidance for implementation of PRA to better characterize variability 
and uncertainty in fate and transport, and exposure assessment for 
human health and ecological risk assessments, and dose-response 
assessment for ecological risk assessments.

Goals

    EPA welcomes feedback on today's draft RAGS 3A document. EPA will 
review public comments received on the draft RAGS 3A document and, 
where appropriate, incorporate changes responsive to those comments.
    EPA is seeking public comment at this time in order to ensure 
hearing the widest range of views and obtaining all information 
relevant to the development of policy, not because doing so is a legal 
requirement. EPA does, however, expect to respond to the principal 
comments received on the draft RAGS 3A document as a matter of public 
information.


[[Page 7552]]


    Dated: February 9, 2000.
Stephen Luftig,
Office Director, Office of Emergency and Remedial Response.
[FR Doc. 00-3492 Filed 2-14-00; 8:45 am]
BILLING CODE 6560-50-U