United States Environmental Protection Agency
Office of Water, Office of Wastewater Management, Water Permits Division

December 2024

EPA Toxicity Spreadsheet Statistical Tool

Description

The U.S. EPA's Water Permits Division/Office of Wastewater Management developed this EPA toxicity
spreadsheet statistical tool for EPA regions, states, authorized Tribes and interested parties to use to statistically
analyze valid toxicity test data. This toxicity spreadsheet statistical tool is based on Microsoft Excel®1. The
spreadsheet calculates acute and chronic toxicity biological effects on EPA toxicity test organisms (e.g., survival,
reproduction, biomass, fertilization) contained in EPA's toxicity test methods and used under the National
Pollutant Discharge Elimination System (NPDES) Whole Effluent Toxicity (WET) permit program. Valid
toxicity data generated from the following EPA toxicity test methods can be analyzed using this spreadsheet tool:
EPA toxicity test methods at 40 CFR Part 136 (USEPA 2002a, 2002b, 2002c) and EPA's west coast chronic
marine toxicity test methods (USEPA 1995). The spreadsheet calculates various toxicity test endpoints in EPA's
Technical Support Document for Water Quality-based Toxics Control (TSD; EPA/505/2-90-001, March 1991;
e.g., LCso, NOAEC, NOEC, LOEC, IC25; see Chapter 1, Section 1.3) based on the statistical flowcharts provided
in EPA's toxicity test methods, as well as results using EPA's NPDES WET Test of Significant Toxicity (TST)
document (EPA 833-R-10-003, June 2010).

Why is U.S. EPA making this spreadsheet

available to regions, states and
authorized Tribes?

EPA developed this toxicity spreadsheet statistical tool in
response to numerous requests from EPA regions, NPDES
permitting authorities and interested parties for a free statistical
tool to independently analyze and evaluate valid toxicity test data
(i.e., monitoring data used for NPDES WET permit and
compliance purposes). EPA regions and permitting authorities
have been successfully using the spreadsheet tool since 2012.

What can the EPA toxicity spreadsheet
statistical tool be used for?

•	NPDES permit reasonable potential evaluations. Point estimates using EPA's TSD statistical
approaches, as well as EPA's TST statistical approaches can be used for evaluating reasonable
potential.

•	NPDES permit compliance determinations. Point estimate (LC50, IC25) and hypothesis
(NOEC/LOEC, TST) statistical results can be used to determine NPDES WET permit compliance.

For more information, contact:

Laura Phillips, EPA HQ/OWM/WPD, (202) 564-0741, phillips.laura@epa.gov
Jackie Clark, EPA HQ/OWM/WPD, (202)-564-6582, clark.jackie@epa.gov



Features of the EPA Toxicity



Spreadsheet Statistical Tool

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Uses Microsoft Excel®, which is readily



available on most computers

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Easy data entry & toxicity test reference



tabs

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Drop down menus for entering different



types of valid toxicity test data & test



endpoint analyses (TSD and TST)

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One-click output of data

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Graphical & tabular display of results

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Ability to easily print or save analysis



results

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Runs Reasonable Potential analyses



using either TSD or TST


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