Reassessment of 2,3,7,8-Tetrachlorodibenzo-p-dioxin (2,3,7,8- TCDD, dioxin)

ENVIRONMENTAL PROTECTION AGENCY

[FRL-5070-7]

Reassessment of 2,3,7,8-Tetrachlorodibenzo-p-dioxin (2,3,7,8-

TCDD, dioxin)

AGENCY: Environmental Protection Agency (EPA).

ACTION: As part of the Agency's reassessment of 2,3,7,8-

tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD, hereinafter referred to as

simply dioxin), two External Review Draft documents are being made

available for a 120-day public review and comment period.

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SUMMARY: This notice announces the availability of two External Review

Draft documents for public review and comment:

1. Health Assessment Document for 2,3,7,8-Tetrachlorodibenzo-p-dioxin

(TCDD) and Related Compounds (EPA/600/BP-92/001a-c)

2. Estimating Exposure to Dioxin-Like Compounds (EPA/600/6-88/005Ca-c)

During the public comment period, public comment meetings will be

convened to take formal comments on the draft documents. These meetings

are being planned for the first two weeks of December at five

locations: Washington, DC; New York, NY/New Jersey; Chicago, IL;

Dallas, TX; and San Francisco, CA. Detailed information will be

provided in a future Federal Register notice.

The draft documents also will be reviewed at a Science Advisory

Board meeting to be held after the public comment period has ended,

early next year. Information about this meeting will be published in a

future Federal Register notice.

DATES: The draft documents will be made available on September 13,

1994. Comments must be postmarked by January 13, 1994.

ADDRESSES:

Requesting Documents

Due to the large size of both draft documents (each is over 1,000

pages in length), the documents will be available as follows:

Health Assessment Document for 2,3,7,8-Tetrachlorodibenzo-p-dioxin

(TCDD) and Related Compounds, EPA/600/BP-92/001a, 001b, 001c. (Note:

The full document is 3 volumes and approx. 1,100 pages.)

or

Risk Characterization Chapter, EPA/600/BP-92/001c. (Note: This third

volume of the 3-volume set integrates health and exposure information

on dioxin and related compounds; approx. 100 pages.)

and/or

Estimating Exposure to Dioxin-Like Compounds, EPA/600/6-88/005Ca, Cb,

Cc. (Note: The full document is 3 volumes and approx. 1,300 pages.)

or

Executive Summary Chapter of the Exposure Document, EPA/600/6-88/005Ca.

(Note: This first volume of the 3-volume set summarizes the exposure

information; approx. 100 pages.)

To obtain a paper copy of these draft documents, interested parties

should contact the ORD Publications Center, CERI-FRN, U.S.

Environmental Protection Agency, 26 W. Martin Luther King Drive,

Cincinnati, OH 45268; telephone (513) 569-7562; fax (513) 569-7566.

Please provide your name, mailing address, document title, and EPA

number.

Please note that the two summary volumes also will be made

available as WordPerfect 5.1 files on 3\1/2\'' PC-DOS formatted disks.

Please request by document title and EPA number:

Risk Characterization Chapter (Vol. III-Health), EPA/600/BP-92/001ca

(disk)

Executive Summary Chapter (Vol. I-Exposure), EPA/600/6-88/005Caa (disk)

The draft documents will be provided for inspection at the ORD

Public Information Shelf, EPA Headquarters Library, 401 M Street, S.W.,

Washington, DC 20460, between the hours of 10 a.m. and 2 p.m., Monday

through Friday, except for Federal holidays, and at all of the EPA

Regional and Laboratory libraries.

Submitting Comments

All comments must be in writing. Commenters should submit three

copies of each comment, and if commenting on both documents--the health

assessment document and the exposure assessment--submit separate

comments rather than combined submissions.

For the health assessment document, send comments to: Dioxin Health

Assessment Comments, Technical Information Staff (8601), Office of

Health and Environmental Assessment, U.S. Environmental Protection

Agency, 401 M Street, S.W., Washington, DC 20460.

For the exposure assessment document, send comments to: Dioxin

Exposure Assessment Comments, Technical Information Staff (8601),

Office of Health and Environmental Assessment, U.S. Environmental

Protection Agency, 401 M Street, SW., Washington, DC 20460.

FOR FURTHER INFORMATION CONTACT:

For questions on the overall reassessment of dioxin or technical

questions on the health assessment document: William Farland, Office of

Health and Environmental Assessment (8601), Office of Research and

Development, U.S. Environmental Protection Agency, 401 M Street, SW.,

Washington, DC 20460; telephone (202) 260-7315; fax (202) 260-0393.

For technical questions on the exposure assessment: John Schaum,

Exposure Assessment Group (8603), Office of Health and Environmental

Assessment, U.S. Environmental Protection Agency, 401 M Street SW.,

Washington, DC 20460; telephone (202) 260-8909; fax 260-1722.

SUPPLEMENTARY INFORMATION:

The Scientific Reassessment of Dioxin

In April 1991, EPA announced that it would conduct a scientific

reassessment of the health risks of exposure to 2,3,7,8-

tetracholorodibenzo-p-dioxin (TCDD) and chemically similar compounds

collectively known as dioxin. The EPA has undertaken this task in

response to emerging scientific knowledge of the biological, human

health, and environmental effects of dioxin. Significant advances have

occurred in the scientific understanding of mechanisms of dioxin

toxicity, of the carcinogenic and other adverse health effects of

dioxin in people, of the pathways to human exposure, and of the toxic

effects of dioxin to the environment. The reassessment is part of the

Agency's goals to improve the research and science base and to

incorporate improved research and science into EPA decisions.

History

In 1985 and 1988, the Agency prepared assessments of the human

health risks from environmental exposures to dioxin. Also, in 1988, a

draft exposure document was prepared that presented procedures for

conducting site-specific exposure assessments to dioxin-like compounds.

These assessments were reviewed by the Agency's Science Advisory Board

(SAB). At the time of the 1988 assessments, there was general agreement

within the scientific community that there could be a substantial

improvement over the existing approach to analyzing dose response, but

there was no consensus as to a more biologically defensible

methodology. The Agency was asked to explore the development of such a

method. The Agency's reassessment activities are in response to this

request.

Stages in the Reassessment Process That Have Been Completed

The EPA had endeavored to make each phase of the reassessment of

dioxin an open and participatory effort. On November 15, 1991, and

April 28, 1992, public meetings were held to discuss the Agency's plans

and activities for the reassessment, to hear and receive public

comments and reviews of the proposed plans, and to receive any current,

scientifically relevant information.

In the Fall of 1992, the Agency convened two peer-review workshops

to review draft documents related to EPA's scientific reassessment of

the health effects of dioxin. The first workshop was held September 10

and 11, 1992, to review a draft exposure assessment titled, Estimating

Exposures to Dioxin-Like Compounds. The second workshop was held

September 22-25, 1992, to review eight chapters of a future draft

Health Assessment Document for 2,3,7,8-Tetrachlorodibenzo-p-dioxin

(TCDD) and Related Compounds. Peer-reviewers were also asked to

identify issues to be incorporated into the risk characterization,

which was under development.

In the Fall of 1993, a third peer-review workshop was held on

September 7 and 8, to review a draft of the revised and expanded

Epidemiology and Human Data Chapter, which also would be part of the

future health assessment document. The revised chapter provided an

evaluation of the scientific quality and strength of the epidemiology

data in the evaluation of toxic health effects, both cancer and

noncancer, from exposure to dioxin, with an emphasis on the specific

congener, 2,3,7,8-TCDD.

Prior to each workshop, the draft documents or chapters were made

available in keeping with the Agency's continuing commitment to conduct

the reassessment of dioxin in an open and participatory manner, to keep

the public informed of its progress, and to encourage public

participation in the document development process. The public also was

invited to attend the workshops, to present oral comments, and/or to

submit written comments. At each workshop, a panel of scientific

experts from outside the Agency reviewed the draft documents and

provided valuable comments. It also should be noted that outside

scientists have been heavily involved throughout the developmental

process of writing and reviewing these draft documents. With this

notice, the External Review Drafts of both draft documents are being

released for a 120-day public review and comment period.

Current Stage of the Scientific Reassessment of Dioxin

The scientific reassessment of dioxin consists of five activities:

1. Update and revision of the health assessment document for dioxin.

2. Laboratory research in support of the dose-response model.

3. Development of a biologically based dose-response model for dioxin.

4. Update and revision of the dioxin exposure assessment document.

5. Research to characterize ecological risks in aquatic ecosystems.

The first four activities have resulted in two draft documents (the

health assessment document and exposure document) for 2,3,7,8-

tetrachlorodibenzo-p-dioxin (TCDD) and related compounds. These

companion documents, which form the basis for the Agency's reassessment

of dioxin, have been used in the development of the risk

characterization chapter that follows the health assessment (Chapter 9,

Volume III). The process for developing these documents consisted of

three phases which are outlined in later paragraphs.

The fifth activity, which is in progress at EPA's Environmental

Research Laboratory in Duluth, Minnesota, involves characterizing

ecological risks in aquatic ecosystems from exposure to dioxins.

Research efforts are focused on the study of organisms in aquatic food

webs to identify the effects of dioxin exposure that are likely to

result in significant population impacts. A report titled, Interim

Report on Data and Methods for the Assessment of 2,3,7,8-

Tetrachlorodibenzo-p-Dioxin (TCDD) Risks to Aquatic Organisms and

Associated Wildlife (EPA/600/R-93/055), was published in April 1993.

This report will serve as a background document for assessing dioxin-

related ecological risks. Ultimately, these data will support the

development of aquatic life criteria which will aid in the

implementation of the Clean Water Act.

As mentioned previously, completion of the health assessment and

exposure documents involves three phases: Phase 1 involved drafting

state-of-the-science chapters and a dose-response model for the health

assessment document, expanding the exposure document to address dioxin

related compounds, and conducting peer-review workshops by panels of

experts. This phase has been completed.

Phase 2, preparation of the risk characterization, began during the

September 1992 workshops with discussions by the peer-review panels and

formulation of points to be carried forward into the risk

characterization. Following the September 1993 workshop, this work was

completed and was incorporated as Chapter 9 (Volume III) of the draft

health assessment document. This phase has been completed.

Phase 3 is currently underway. It includes making External Review

Drafts of both the health assessment document and the exposure document

available for public review and comment.

Next Stages in the Reassessment Process

As described previously, public briefings will be held during the

first week of the public comment period to be followed by formal public

hearings in December 1994. After the close of the public comment

period, the Agency's Science Advisory Board (SAB) will review the draft

documents in public session (early 1995). Following SAB review, the

draft documents will be revised, comments and revisions will be

incorporated, and final documents will be issued.

Dated: August 30, 1994.

Carl R. Gerber,

Acting Assistant Administrator for Research and Development.

[FR Doc. 94-22442 Filed 9-12-94; 8:45 am]

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