.
UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON, D.C. 20460
-.„,„„- TQQ< OFFICE OF THE ADMINISTRATOR
reoruary A iy^:> SCENCE ADVISORY BOARD
EPA-SAB-EPEC-LTR-95-001
Carol M. Browner
Administrator
U.S. Environmental Protection Agency
401 M Street, S.W.
Washington, D.C. 20460
RE: Science Advisory Board Review of the Technical Basis for Listing Ammonia on the
Toxics Release
Dear Ms. Browner,
The Toxics Reporting Subcommittee of the Ecological Processes and Effects Committee of
the Science Advisory Board met in Washington, D.C. on January 4, 1995 to discuss questions
related to the listing of ammonia on the Toxics Release Inventory (TRI). The Subcommittee was
briefed by EPA staff from the Office of Pollution Prevention and Toxics and the Office of Research
and Development on the rationale for listing ammonia on the TRI and received public comments
from scientists appearing on behalf of petitioners to delist ammonia.
1. The EPA asked the SAB to address two questions which follow with our responses.
a. What is the most appropriate way to report releases of aqueous ammonia under the
Emergency Planning and Community Right-to-Know Act (EPC,RA) section-313 as non-
ionized ammonia or as total ammonia?
Response of the Subcommittee: The factors influencing the environmental behavior of
ionized and non-ionized ammonia, and the relationships of these two forms to total ammonia, are
well understood. Furthermore, the potential toxicity to aquatic life and human health, as well as
potential ecological effects related to nutrient enrichment by the major forms of ammonia, are well
understood. Thus, the major issues related to the question posed by the Agency to this
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Subcommittee do not involve scientific uncertainties, but they relate instead to how the scientific
information should be integrated into the structure of the TRI. That is, the scientific basis for
regulating aqueous ammonia as detailed by EPA OPPT and ORD staff is clear and definitive.
Ionized ammonia and non-ionized ammonia always occur together, and their proportions
are governed by pH and temperature. Total ammonia = ionized ammonia + non-ionized ammonia.
If the concentration of any form of ammonia is known and the temperature and pH in the
environment are known, then the concentrations of the other forms of ammonia can be readily
calculated. These relationships hold true for the forms of ammonia in a discharge, as well as under
environmental conditions. Under normal environmental conditions the ionized ammonia
concentrations are much higher than the non-ionized ammonia concentrations.
Toxicity has been used as the major basis for listing other substances on the TRI. The acute
toxicity of non-ionized ammonia to aquatic life is approximately 100 times greater than ionized
ammonia. The toxicities of non-ionized and ionized ammonia are approximately additive. Because
of the differences in potency between these forms of ammonia, under normal environmental
conditions the acute toxicity of ammonia is driven almost exclusively by non-ionized ammonia
concentrations. If ammonia only existed in the ionized form, then it is doubtful that ammonia
would have been listed on the TRI based on the Agency's current TRI toxicity guidelines.
For example, if the policy concern is solely for aquatic toxicity, then reporting non-ionized
ammonia concentrations at a standard pH and temperature (e.g. pH 7 and 15°C) would address this
endpoint If the policy concerns extend to other endpoints; e.g., nutrient enrichment, then reporting
of total ammonia would be more appropriate as that would related more clearly to concerns about
the ecological consequences of eutrophication due to nitrogen nutrient enrichment which many
scientists have judged to be an adverse effect on aquatic ecosystems. In this case the specific forms
of ammonia are not very relevant (i.e., both ionized and non-ionized ammonia have the same
nutrient enrichment properties), and total ammonia concentrations would be the most appropriate
form of ammonia to report. Again, the use of standard pH and temperature conditions would also
be useful. It should be noted that nitrogen is typically the limiting nutrient only in coastal waters
and estuaries, but not in fresh waters where phosphates are typically the limiting nutrients.
The Subcommittee concludes that the scientific facts on the chemistry, transformations,
toxicity, and ecological effects of the various forms of ammonia are well understood. Thus, the
question of whether to list or how to list ammonia or any of its forms is not a scientific issue but
strictly a matter of policy for the. Agency to decide.
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b. Does total ammonia meet the EPCRA section 313 listing criteria?
Response of the Subcommittee: Section 313(d)(2)(C) lists the criteria for inclusion in the
TRI as toxicity, persistence, bioaccumulation, and a significantly adverse effect on the environment
of sufficient seriousness in the judgement of the Administrator. The issue of toxicity was addressed
above. Bioaccumulatioo is not a factor for ammonia. Environmental persistence is more difficult
to define, Because white ammonia may be unstable, the component nitrogen becomes part of a
regional nitrogen cycle. The ammonia contribution to this cycle is often overlooked. Based on our
evaluation of the criteria, we conclude that total ammonia meets the EPCRA section 313 listing
criteria only if the Administrator determines that there is "a significant adverse effect on the
environment of sufficient seriousness to warrant reporting".
2. Policy-Related Observations and Concerns
The Subcommittee was not constituted to make assessments of the scientific underpinnings
of the Toxic Release Inventory (TRI) portion of EPCRA or to evaluate items of policy concerning
the act, nor is the SAB constituted to make policy recommendations. Therefore the policy
implications and policy recommendations cannot be addressed in depth. However, during the
discussion of the issue with the Agency and the public, the Subcommittee detected some confusion
about the roles and the relationships of emissions inventory, hazard assessment, exposure
assessment, and risk assessment in the development of TRI listings and subsequent uses of the TRI
data. The Subcommittee concluded, based on presentations by the Agency and public comments,
that the TRI data are sometimes misinterpreted to imply that they are direct measurements of
exposure and risk. The TRI emissions data can be useful for identifying potential targets for waste
reduction. However, they do not reflect toxicity/potency of various pollutant emissions and are not
related to exposure in a simple way, i.e., large emissions do not automatically imply large exposures
and risks to the population. Hence, the TRI data should not be represented as measures of
quantitative risk. All Subcommittee members expressed concerns about the potential for
misinterpretation of the TRI data and for inadvertently directing environmental protection efforts
away from the areas of most significant risk.
The Subcommittee notes that an opportunity exists for the Agency to conduct a broader
evaluation of the TRI reporting system. The goal of such an evaluation would be to improve the
value of the listings to the public as they interpret the significance of the information.
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We appreciate the opportunity to review these questions and we look forward to your
response to our comments.
Sincerely yours,
Dr uenevieve MatanostaTCnair
Executive Committee
Science Advisory Board
Dr. Mark Harwell, Chair
Ecological Processes and Effects Committee
Toxics Reporting Subcommittee
Ecological Processes and Effects Committee
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US ENVIRONMENTAL PROTECTION AGENCY
SCIENCE ADVISORY BOARD
ECOLOGICAL PROCESSES AND EFFECTS COMMITTEE
TOXICS REPORTING SUBCOMMITTEE
January 4. 1994
CHAIR
DR. ROLF HARTUNG, Professor, School of Public Health,
University of Michigan, Ann Arbor, Michigan
MEMBERS and CONSULTANTS
DR. WILLIAM J. ADAMS, ABC Laboratories, Columbia, Missouri
DR. PETER CHAPMAN, EVS Consultants, Vancouver,
British Columbia
DR. CHRISTOPHER G. INGERSOLL, Midwest Research
Center, National Biological Survey, Columbia, Missouri
FEDERAL EXPERT
DR. EDWARD LONG, NOAA-ORCA, Seattle, Washington -
FEDERAL EXPERT
DR. SAMUEL N. LUOMA, USGS, Menlo Park, California
FEDERAL EXPERT
DR. ALAN W. MAK^, Exxon Company, Houston, Texas
DR. FREDERIC K. PFAENDER, Director, Institute of Environmental
Studies, University of North Carolina, Chapel Hill, North
Carolina
DR. HERBERT WINDOM, Acting Director, Skidaway Institute of
Oceanography, Savannah, Georgia
DR. TERRY F. YOUNG, Environmental Defense Fund, Oakland,
California
SCIENCE ADVISORY BOARD STAFF
DR. EDWARD S. BENDER, Designated Federal Official, US
EPA/Science Advisory Board, 401 M Street, S.W. (1400-F)
Washington, D.C. 20460
(202) 260-6552 FAX: (202) 260-7118
MRS. CONNIE VALENTINE, Secretary to the Designated
Federal Official
(202) 260-6552 FAX: (202) 260-7118
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