                                                           File: ABSTRACT.TXT


                         LC50 Model System Abstract


               Center for Exposure Assessment Modeling (CEAM)
     National Exposure Research Laboratory - Ecosystems Research Division
                  Office of Research and Development (ORD)
               U.S. Environmental Protection Agency (U.S. EPA)
                          960 College Station Road
                         Athens, Georgia 30605-2700

                                706/355-8400



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                                  Summary

LC50 (lethal concentration, 50%) estimates LC50 values using the Trimmed
Spearman-Karber Method.  This program originated at Montana State University
and has been modified by data processing staffs at the Duluth and Athens
National Exposure Research Laboratories.  For a more detailed explanation of
the model and its functionality, see the enclosed user manual.

For reference, cite:
Hamilton, M.A., R.C. Russo, and R.V. Thurston, 1977.
Trimmed Spearman-Karber Method for Estimating Median Lethal Concentrations
in Toxicity Bioassays.
Environ. Sci. Technol. 11(7): 714-719;
Correction 12(4):417  (1978).

                                Documentation

The LC50 User's Manual is available as an Adobe(*) Acrobat(*) Portable
Document Format (PDF) file (USERMANU.PDF) within the DOCUMENT sub-directory
if the user chose to install the user's manual from the INSTALLC.EXE program
install menu.  To view, print, and/or navigate a PDF document, a reader
program must be installed on the users computer system.  A free Adobe reader
allows the user to view, navigate, and/or print PDF files across all major
computing platforms.  Acrobat Reader is a free viewing companion to Adobe
Acrobat 3.0 and is available free from the Adobe world wide web (WWW) site at
Uniform Resource Locator (URL) address: http://www.adobe.com.

To ensure that the user can view and/or print a PDF file in its entirety, the
user must down load and install the most recent version/edition of the free
Acrobat Reader.  PDF files can be viewed across multiple platforms (Mac,
Microcomputer, UNIX) using the appropriate reader for that platform.

* Adobe, Acrobat, and Adobe Type Manager are trademarks of Adobe Systems
Incorporated and may be registered in certain jurisdictions.  (C) Copyright
1994 Adobe Systems Incorporated.  All rights reserved.

Refer to file READ.ME in the README sub-directory for further information on
the storage format and hardware and/or software print/view requirement(s) of
the user's manual file.

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