U.S. GEOLOGICAL SURVEY

Water-Resources Investigations Report

Pesticide Toxicity Index for 

Freshwater Aquatic Organisms 

by Mark D. Munn and Robert J. Gilliom

Sacramento, California

2001

01-4077

8056-76

NATIONAL WATER-QUALITY ASSESSMENT PROGRAM
U.S. DEPARTMENT OF THE INTERIOR

GALE A. NORTON, Secretary

U.S. GEOLOGICAL SURVEY

Charles G. Groat, Director

The use of firm, trade, and brand names in this report is for identification purposes only and does

not constitute endorsement by the United States Government.

For additional information write to: Copies of this report can be purchased

U.S. Geological Survey

Branch of Information Services

Box 25286

Denver, CO 80225-0286

from:

District Chief

U.S. Geological Survey

Water Resources Division

Placer Hall, 6000 J Street

Sacramento, California 95819-6129
Robert M. Hirsch

Associate Director for Water

FOREWORD

The U.S. Geological Survey (USGS) is committed to 

serve the Nation with accurate and timely scientific information that helps enhance and protect the overall quality of 

life, and facilitates effective management of water, biological, energy, and mineral resources. (http://www.usgs.gov/). 

Information on the quality of the Nation s water resources is 

of critical interest to the USGS because it is so integrally 

linked to the long-term availability of water that is clean and 

safe for drinking and recreation and that is suitable for 

industry, irrigation, and habitat for fish and wildlife. Escalating population growth and increasing demands for the 

multiple water uses make water availability, now measured 

in terms of quantity and quality, even more critical to the 

long-term sustainability of our communities and ecosystems.

The USGS implemented the National Water-Quality 

Assessment (NAWQA) Program to support national, 

regional, and local information needs and decisions related 

to water-quality management and policy. (http://

water.usgs.gov/nawqa). Shaped by and coordinated with 

ongoing efforts of other Federal, State, and local agencies, 

the NAWQA Program is designed to answer: What is the 

condition of our Nation s streams and ground water? How 

are the conditions changing over time? How do natural features and human activities affect the quality of streams and 

ground water, and where are those effects most pronounced? By combining information on water chemistry, 

physical characteristics, stream habitat, and aquatic life, the 

NAWQA Program aims to provide science-based insights 

for current and emerging water issues and priorities. 

NAWQA results can contribute to informed decisions that 

result in practical and effective water-resource management 

and strategies that protect and restore water quality.

Since 1991, the NAWQA Program has implemented 

interdisciplinary assessments in more than 50 of the 

Nation s most important river basins and aquifers, referred 

to as Study Units. (http://water.usgs.gov/nawqa/

nawqamap.html). Collectively, these Study Units account 

for more than 60 percent of the overall water use and population served by public water supply, and are representative 

of the Nation s major hydrologic landscapes, priority ecological resources, and agricultural, urban, and natural 

sources of contamination. 

Each assessment is guided by a nationally consistent 

study design and methods of sampling and analysis. The 

assessments thereby build local knowledge abou

quality issues and trends in a particular stream or 

while providing an understanding of how and wh

quality varies regionally and nationally. The cons

multi-scale approach helps to determine if certain 

water-quality issues are isolated or pervasive, an

direct comparisons of how human activities and n

cesses affect water quality and ecological health 

Nation s diverse geographic and environmental s

Comprehensive assessments on pesticides, nutrie

tile organic compounds, trace metals, and aquatic 

are developed at the national scale through comp

analysis of the Study-Unit findings. (http://water

nawqa/natsyn.html). 

The USGS places high value on the commun

and dissemination of credible, timely, and releva

so that the most recent and available knowledge a

resources can be applied in management and pol

sions. We hope this NAWQA publication will pr

the needed insights and information to meet your 

thereby foster increased awareness and involvem

protection and restoration of our Nation s waters

The NAWQA Program recognizes that a nat

assessment by a single program cannot address a

resource issues of interest. External coordination 

els is critical for a fully integrated understanding 

sheds and for cost-effective management, regulat

conservation of our Nation s water resources. The 

therefore, depends extensively on the advice, coo

and information from other Federal, State, interst

and local agencies, non-government organization

academia, and other stakeholder groups. The assi

suggestions of all are greatly appreciated.
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Contents 

CONTENTS

Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Purpose and Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Development of the Pesticide Toxicity Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Applications of the Pesticide Toxicity Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Example Application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Limitations of the Pesticide Toxicity Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Summary and Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

References Cited . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

FIGURES

1. Concentrations of the 18 most common pesticides found in Little Buck Creek, Indiana . . . . . . . . . . . . . . . . . . . . 

2. Pesticide Toxicity Index for bluegills in Little Buck Creek, Indiana, and the contributions of 

selected pesticides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

3. Pesticide Toxicity Index for bluegills in Little Buck Creek, Indiana, compared with 

total pesticide concentration. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

TABLES

1. Pesticides analyzed in surface waters for the National Water-Quality Assessment (NAWQA) Program . . . . . . . . 

2. Summary of toxicity values by species . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

3. Summary of taxa included in bioassay data set and number of bioassays and compounds . . . . . . . . . . . . . . . . . . 

4. Summary of EC50 median toxicity concentrations for cladocerans . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

5. Summary of LC50 median toxicity concentrations for benthic invertebrates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

6. Summary of LC50 median toxicity concentrations for freshwater fish . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

7. Relative toxicity of the pesticides within each of three taxonomic groups: cladocerans, 

benthic invertebrates, and fish . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

ACRONYMS AND ABBREVIATIONS

AQUIRE, AQUatic Toxicity Information REtrieval (EPA database)

BCF, bioconcentration factor

EC, effect concentration (behavioral change)

CAS, Chemical Abstracts Service

CRS, chemical ranking and scoring (system)

EC50, concentration at which 50 percent of test organisms exhibited nonlethal responses (an effect on behavior)

EPA, U.S. Environmental Protection Agency

LC, lethal concentration (mortal)

LC50, concentration lethal to 50 percent of test organisms (mortality)

N, number of bioassays

NAWQA, National Water-Quality Assessment (Program)

NOEL, no observed effect level

ppb, part per billion

PTI, Pesticide Toxicity Index

MTC, median toxicity concentration for a pesticide

USGS, U.S. Geological Survey

Abstract 

Pesticide Toxicity Index for Freshwater Aquatic Organisms

by Mark D. Munn and Robert J. Gilliom

ABSTRACT

The U.S. Geological Survey’s National 

Water-Quality Assessment (NAWQA) Program is 

designed to assess current water-quality conditions, changes in water quality over time, and the 

effects of natural and human factors on water 

quality for the Nation’s streams and ground-water 

resources. For streams, one of the most difficult 

parts of the assessment is to link chemical conditions to effects on aquatic biota, particularly for 

pesticides, which tend to occur in streams as complex mixtures with strong seasonal patterns. 

A Pesticide Toxicity Index (PTI) was developed that combines pesticide exposure of aquatic 

biota (measured concentrations of pesticides in 

stream water) with toxicity estimates (standard 

endpoints from laboratory bioassays) to produce a 

single index value for a sample or site. The development of the PTI was limited to pesticide compounds routinely measured in NAWQA studies 

and to toxicity data readily available from existing 

databases. Qualifying toxicity data were found for 

one or more types of test organisms for 75 of the 

83 pesticide compounds measured in NAWQA 

samples, but with a wide range of bioassays per 

compound (1 to 65). There were a total of 2,824 

bioassays for the 75 compounds, including 287 

48-hour EC50 values (concentration at which 50 

percent of test organisms exhibit a nonlethal 

response) for freshwater cladocerans, 585 96-hour 

LC50 values (concentration lethal to 50 percent of 

test organisms) for freshwater benthic invertebrates, and 1,952 96-hour LC50 values for freshwater fish. The PTI for a particular sample is the 

sum of toxicity quotients (measured concentration 

divided by the median toxicity concentration fr

bioassays) for each detected pesticide. The PT

can be calculated for specific groups of pesticid

and for specific taxonomic groups.

While the PTI does not determine wheth

water in a sample is toxic, its values can be use

to rank or compare the toxicity of samples or si

on a relative basis for use in further analysis or 

additional assessments. The PTI approach may 

useful as a basis for comparing the potential si

nificance of pesticides in different streams on a 

common basis, for evaluating relations betwee

pesticide exposure and observed biological con

tions, and for prioritizing where further studies 

are most needed. 

INTRODUCTION

Background

The U.S. Geological Survey’s (USGS) Natio

Water-Quality Assessment (NAWQA) Program is 

designed to assess current water-quality conditions

changes in water quality over time, and the effects 

natural and human factors on water quality for the 

Nation’s streams and ground-water resources (Hirs

and others, 1988; Leahy and others, 1990; Gilliom 

others, 1995). In 1991, the NAWQA Program bega

investigating physical, chemical, and biological 

characteristics of water resources in more than 50 

major hydrologic systems in the Nation, referred to 

study units. Integrating these different aspects of wa

quality and understanding cause-and-effect relation

one of the principle challenges for the NAWQA 

Program. For streams, one of the most difficult part

the assessment is to link chemical conditions to effe
2 Pesticide Toxicity Index for Freshwater Aquatic Organisms

on aquatic biota, particularly for pesticides, which 

tend to occur in streams as complex mixtures with 

strong seasonal patterns. 

The most common way of assessing the 

potential effects of pesticides on the aquatic environment in a controlled manner is by standardized 

laboratory bioassays that expose a single species to a 

single compound for a predetermined time period at 

specified concentration levels. Depending on the 

effects measured, specific endpoints can be calculated. 

Common toxicological endpoints include lethal 

concentrations (LC), effect concentrations that result 

in a nonlethal response (EC), and no observed effect 

levels (NOEL). Laboratory bioassays are commonly 

used to assess single compounds for registration, 

effluent permits, and toxicological research, but 

laboratory results cannot reliably be extrapolated 

directly to field conditions. For example, species used 

in bioassays are rarely the same species that reside in a 

particular system, tested life-history stages do not 

include all the exposed life stages, test duration does 

not match the predicted exposure duration, physical 

and chemical test conditions are not the same as the 

expected field conditions, reported responses do not 

include all the responses of concern, and test endpoints are at a different level of biological organization 

(organism) than the assessment endpoints (population 

to ecosystem) (Sutter, 1995). However, even with 

these well-known limitations, bioassays remain a 

useful tool for quantifying toxicological effects of 

specific contaminants on aquatic life in a consistent 

relatively reproducible manner. Furthermore, standardized bioassay tests are constantly being improved 

with the development of new tests. 

One type of ecological risk-assessment method 

presently being used to address the complexity of 

pesticide exposure and effects is chemical ranking and 

scoring (CRS) systems (Swanson and Socha, 1997), 

which are based on the potential toxicity of chemicals 

to the environment or human health. The selection of a 

particular CRS system depends on the goals of the 

evaluation, the level of information needed, the degree 

of acceptable uncertainty, and the available resources. 

CRS is a tool for assessing chemicals that may 

incorporate health effects, environmental effects or 

other hazards, persistence, and exposure. Many CRS 

systems take a nonrisk-based approach using single 

endpoints as in published toxicity, fate, or exposure 

data. A more realistic method, however, is to use a 

risk-based approach that integrates measured exposure 

(stream concentrations) with biological effe

(bioassays) (Davis and others 1997).

Purpose and Scope

This report describes the developmen

potential applications of a Pesticide Toxicity 

(PTI), which can be used to evaluate the rela

of pesticides to aquatic organisms in stream

is a variation of a risk-based scoring system 

by Kimerle and others (1997). The PTI was 

for use with data collected as part of the NA

Program studies of pesticide concentrations 

water. The PTI can be applied to samples co

NAWQA sites, and PTI values for individua

samples then can be used to rank stream site

according to their expected relative toxicity 

pesticides or to assess changes in potential t

over time at a single site. PTI values for sam

seasons, or sites also can be used as explana

variables in multivariate analysis designed t

determine which environmental variables be

spatial patterns in the structure of a biologic

community.

Acknowledgments

This project was funded by the NAWQ

Program. While many people provided idea

report, we would particularly like to thank R

Stuart (Pentac Consulting), Karsten Liber (U

of Saskatchewan), and Brian Montague (U.S

Environmental Protection Agency [EPA]). W

thank Thomas Cuffney (USGS) and William 

(Colorado State University) for technical rev

DEVELOPMENT OF THE PESTICIDE 

TOXICITY INDEX

The PTI is a ranking system based on 

exposure and toxicity of pesticides to freshw

aquatic organisms. The development of the 

limited to pesticide compounds routinely me

the NAWQA Program and to LC50 (concentr

which 50 percent mortality occurred) and E

(concentration at which 50 percent of test or

exhibited nonlethal responses) toxicity data 

available from existing databases. 

The PTI is the sum of toxicity quotien

pesticide compound measured in a stream: 
Development of the Pesticide Toxicity Index 

(1)

where

 Ei = concentration of pesticide i

 MTCx,i = median toxicity concentration for the 

pesticide i for taxonomic group x

 n = number of pesticides, and

 E and MTC are expressed in the same units.

In most cases, the PTI should be calculated for a single 

taxonomic group as appropriate for the specific 

application. In addition, the most meaningful values of 

PTI may be for groups of chemicals with similar 

modes of toxicity.

 NAWQA Program pesticide data evaluated for 

the PTI include 76 pesticides and 7 degradation 

products (table 1). Of the 76 parent compounds, the 

majority are herbicides (68 percent) and insecticides 

(30 percent); only one fungicide and one nematocide 

were evaluated. Pesticide data were collected at 

various levels of intensity throughout the year at 

stream sites in each NAWQA study unit (Shelton, 

1994).

Toxicity data for each compound were obtained 

primarily from two EPA databases—AQUIRE 

(AQUatic Toxicity Information REtrieval) and the 

Pesticide Ecotoxicity Database. AQUIRE 

(http://www.epa.gov/ecotox/), a database developed 

by the EPA National Health and Environmental 

Effects Research Laboratory, is one of the primary 

resources for aquatic toxicity information and is 

commonly used to evaluate and prioritize the hazards 

of industrial chemicals and pesticides for impact 

assessments of effluent and leachate discharges (U.S. 

Environmental Protection Agency, accessed December 

12, 2000). The second EPA database is the Pesticide 

Ecotoxicity Database, which was developed by the 

EPA Office of Pesticide Programs. Some of the 

toxicity data are in both databases. 

The toxicity databases contain a wide range of 

toxicological data that are highly variable in nature 

and quality. Criteria were established to ensure that the 

data were relatively comparable; however, many 

factors in a bioassay could not be accounted for, any of 

which can greatly increase the variability of results for 

a particular compound. Criteria used to screen data for 

the PTI are: 

• Species: Bioassays used are for freshwater invertebrates or fish, or at least species that completed 

part of their life cycle in the freshwater 

environment (for example, salmon). 

• Endpoint: Two endpoints were selected from the 

toxicity databases, LC50 and EC50. 

• Duration: The LC50 test was for 96 hours, and the 

EC50 test was for 48 hours.

• Concentrations: Discreet values were required; 

therefore, results reported as “greater than” a 

particular value, or as ranges, were not include

Qualifying toxicity data were found for 75 o

the 83 compounds measured in water samples from 

the NAWQA Program, but with a wide range of 

bioassays per compound (1 to 165). The review 

resulted in a total of 2,824 bioassays divided into th

data sets: 48-hour EC50 values for freshwater 

cladocerans (commonly referred to as waterfleas), 

96-hour LC50 for freshwater benthic invertebrates 

(including a few invertebrates that are benthic dwel

for only a short time), and 96-hour LC50 values for 

freshwater fish. All values are summarized by spec

in table 2.

The EC50 data set for cladocerans, a related 

group of crustaceans commonly used in laboratory 

bioassays, includes 287 bioassays (table 3). There 

five genera and nine species; however, most tests w

run using Daphnia magna (70 percent), Daphnia pu

(13 percent), and Simocephalus serrulatus (11 

percent). Of the 287 bioassays included, data were 

available for 61 of the 83 pesticide compounds 

analyzed by the NAWQA Program. The median 

number of bioassays per compound was 3 with a ran

of 1 to 24. Data from three or more bioassays were 

available for only 38 of the compounds. The combin

EC50 toxicity data for cladoceran species are 

summarized in table 4.

The LC50 data set for benthic invertebrates 

includes toxicity data from 585 bioassays and 

encompasses 46 of the 83 compounds analyzed in 

NAWQA stream studies (table 3). The median num

of bioassays per pesticide was five, with only 30 

compounds having three or more bioassays. This d

set includes a wide range of benthic invertebrates (

taxa) consisting of Insecta (49 percent), Custacea 

(34 percent), Mollusca (8 percent), Oligochaetae 

(5 percent), Turbullaria (2 percent), and Nematoda 

(1 percent) (table 3). The combined LC50 data for th

benthic invertebrates are summarized in table 5. 

Most bioassays found in the toxicity databas

(1,952) were for freshwater fish (table 3), with toxic

PTI

Ei

MTCx i ,

---------------------------

i 1 =

n

= ∑
4 Pesticide Toxicity Index for Freshwater Aquatic Organisms

data for 90 percent of the pesticides routinely 

measured by NAWQA. This higher number resulted in 

a median of 13 bioassays per compound with 67 

compounds having greater than 3 bioassays. The fish 

data set includes bioassays from 61 different taxa, 

including warm and cold water species. 

Approximately 50 percent of the fish bioassay data 

came from three species: bluegill (20 percent), rainbow trout (19 percent), and fathead minnow (11 

percent). The combined toxicity data for freshwater 

fish are summarized in table 6. 

The relative toxicity of the compounds within 

each of the three taxonomic groups is summarized in 

table 7. Relative toxicity was estimated by setting the 

most toxic compound to 1, and then calculating the 

relative toxicity of all other compounds in the data set 

in comparison to the toxicity value of this compound. 

For example, the most toxic compound for 

cladocerans is chlorpyrifos, with the next compound, 

ethyl parathion, 62 percent as toxic. This approach is 

used by the U.S. Environmental Protection Agency for 

summarizing the toxicity of dioxins and furans (U.S. 

Environmental Protection Agency, 1990). 

APPLICATIONS OF THE PESTICIDE 

TOXICITY INDEX

The PTI combines pesticide exposure of aquatic 

biota (measured pesticide concentrations in stream 

water) with toxicity (laboratory bioassays) to produce 

a toxicity index value for a sample or site. While the 

PTI is not a direct measure of toxicity to biological 

communities, it is a method for weighting and 

aggregating pesticide concentrations in a biologically 

relevant manner. The PTI was developed for use with 

data collected as part of the NAWQA Program studies 

of pesticide concentrations in stream water and thus 

method development was limited to the 83 pesticide 

compounds that are analyzed in most NAWQA stream 

samples (qualifying toxicity data were found for 75 

compounds). The approach also can be applied to 

otherwise appropriate non-NAWQA data for the same 

pesticide compounds.

Most commonly, the application of the PTI to 

assessing stream quality begins with the computation 

of PTI values for detected chemicals and appropriate 

taxa groups for individual water samples. Given the 

relatively short time periods for the bioassay tests 

upon which the PTI is based (48 or 96 hours), each 

individual water sample reasonably represents a 

similar time interval as the bioassay test. Ty

sampling at NAWQA pesticide sites, for exa

two to four samples per month during high u

runoff periods and one to two samples per m

during the rest of the year. Routine monitori

often more sparse than the NAWQA Program 

because of the high expense. With only two 

instantaneous samples collected during a 30

the probability of sampling short-lived cond

such as peak concentrations due to runoff ev

relatively low. There is a general tendency to

sampling the conditions that are relatively c

and thus potential acute toxicity is likely 

underestimated. In applying the PTI to mon

data of this nature, PTI values computed for 

samples are the most appropriate basis for e

potential for toxicity in the stream. This may 

most appropriate approach for other data, ho

such as very frequently collected samples du

short-lived storm. In these cases, concentrat

need to be averaged over an appropriate tim

before computing the PTI. 

The PTI can be calculated with toxici

from any of the three major taxonomic grou

specific subgroup. Of the three, the EC50 dat

cladocerans is the least variable and most co

because it is based on a small number of cla

species, with Daphnia the most common tax

advantage of using the Daphnia data is that 

responses to the various compounds should 

similar because the taxa are closely related. 

two data sets were both based on 96-hour LC

with the fish data set the most complete bec

contains the bioassay data for the most com

Rank correlations between the relative 

values (table 7) for the three taxa groups are 

significant for all combinations, but generall

the independent information value of each. T

correlation of relative toxicities (r2

) for clad

and the benthic invertebrates was greatest, w

of 71 percent (one outlier, pendamethalin, w

excluded), but r2

 values for correlations betw

and cladocerans and between fish and benth

invertebrates were much lower at 47 percent 

percent, respectively. 

PTI values for multiple individual wa

samples can be used to assess changes in po

toxicity over time at a single site or, if statis

aggregated by year or season, to rank stream 

according to their expected relative toxicity 
Limitations of the Pesticide Toxicity Index 

pesticides. PTI values for samples or sites also can be 

used as explanatory variables in multivariate analysis 

aimed at determining which environmental variables 

best explain spatial patterns in the structure of 

biological communities.

Although the PTI relies on measured water 

concentrations and laboratory bioassays, the index 

could be modified to include other variables. For 

example, one could develop an index that includes a 

combination of toxicity, persistence (half-life), and 

bioconcentration factor (BCF). One could also 

combine results for organisms from multiple trophic 

levels, including primary producers (algae), primary 

consumers and prey species (invertebrates), and 

predators (invertebrates and fish) (Kimerle and others 

1997).

EXAMPLE APPLICATION

The potential applications of the PTI include 

evaluating the temporal distribution of relative toxicity 

in a waterbody and identification of which compounds 

or groups of compounds are most likely to cause 

adverse effects. To illustrate the application of the PTI 

to these objectives, the seasonal distribution of 

pesticide levels in Little Buck Creek, an urban stream 

in the Indianapolis area, which also has some cropland 

in its drainage basin, was examined. The data used are 

NAWQA results from analysis of pesticides in 33 

samples during 1993. Methods for sample collection 

and analysis are described by Larson and others 

(1999). 

Throughout the year, most water samples from 

Little Buck Creek contain several pesticides— 

typically 6 to 10 were detectable at any particular time 

and 18 different pesticides were found in more than 10 

percent of the samples. This pattern is typical of many 

urban streams. The complex and varying mixtures of 

herbicides and insecticides make interpretation of 

potential effects on aquatic biota particularly difficult. 

Figure 1 shows concentrations of the 18 most common 

pesticides during 1993. The total concentration of the 

18 pesticides was usually dominated by atrazine, 

simazine, prometon, metolachlor, alachlor, and 

diazinon, and reached the highest levels from late May 

through mid July.

Pesticide concentrations in Little Buck Creek 

were evaluated using the PTI (equation 1) for bluegills, a common species in that area, with MTC from 

table 6, for each of the 12 most commonly found 

pesticides for which there are toxicity values for 

bluegills. Figure 2 shows the PTI for the combinati

of all 12 pesticides during 1993 and the individual 

contributions of each pesticide to the index value. 

Figure 3 shows PTI results for bluegills compared 

total pesticide concentration. The PTI indicates a 

period of highest potential toxicity during June and 

July, when total pesticide concentrations are highes

However, the PTI also indicates potential toxicity 

during parts of autumn, winter, and early spring wh

pesticide concentrations are low. Results indicate th

inference of potential biological effects from pestic

concentration data alone may be misleading. In Lit

Buck Creek, the greatest contributor to the PTI is 

usually the organophosphate insecticide chlorpyrif

even though its concentration is usually low compa

to other compounds. Other major contributors to hi

PTI values are diazinon and malathion, which are a

organophosphate insecticides.

Little Buck Creek illustrates one type of ana

ysis and insight that can be gained through applicat

of the PTI. The PTI provides a simple means to eva

uate the potential toxicity, based on an additive mod

of complex mixtures of pesticides on a sample by 

sample basis. The relation of PTI values, which are 

strictly relative, to actual biological effects remains 

be tested. In evaluating such relations, however, the 

PTI provides a specific quantitative basis for hypotheses that can be tailored to many different situatio

For example, individual PTI can be computed for 

different compound groups with similar modes of 

toxicity (e.g. organophosphates) and for the specifi

type of organism being studied in the field. Inform

tion on the seasonal timing of high PTI values can 

used in the design of effects studies. 

LIMITATIONS OF THE PESTICIDE TOXICITY IND

The PTI has several limitations, which must 

carefully considered in applications: 

• The PTI is a relative ranking system that indicate

that one sample is likely to be more or less tox

than another sample, but does not necessarily 

demonstrate actual toxicity. 

• Toxicity values are based on short-term laborator

experiments with EC50 (nonlethal response) or 
6 Pesticide Toxicity Index for Freshwater Aquatic Organisms

LC50 (mortality) endpoints; therefore, the PTI 

does not incorporate long-term chronic endpoints. 

• Several environmental factors, which are not 

accounted for by the PTI, can modify the toxicity 

and bioavailability of pesticides, including 

dissolved organic carbon, particulates, and 

temperature. 

• This PTI is based on the simplifying assumption that 

pesticide toxicity is additive and there is no 

chemical interaction (synergism, antagonism), 

which may not be the case in the environment. 

One of the primary limitations of the PTI is the 

uncertainty in the relative toxicity of compounds that 

have a low number of comparable bioassays. Whereas 

2,824 bioassays appear to be a large data set

are divided into three categories of endpoint

cladocerans, LC50 for benthic invertebrates, 

for fish), 83 pesticide compounds, and 162 s

making the number in each group relatively 

Many taxa only have a single bioassay per c

although a few taxa have numerous bioassay

compound. Even when species are combine

each of the three major taxonomic groups, th

number of bioassays per compound is relativ

ranging from 3 for the EC50 data set to 13 fo

fish data set. While this does not preclude th

the data as the best available, it demonstrate

sparseness of available data on the toxicity o

the pesticides presently applied. 

Figure 1. Concentrations of the 18 most common pesticides found in Little Buck Creek, Indiana show the complexity of mixtures 

occur in this stream.

0.001

0.01

0.1

1

10

100

Dec. Feb. Apr. June Aug. Oct. Dec. Feb.

, gp

1993

Carba

Chlorp

Diazin

Malath

Alachl

Atrazi

Benflu

Butyla

Cyana

DCPA

Linuro

Metola

Metrib

Pendi

Prome

Simaz

Tebut

Triflura

Sum o

of all 1

EXPLANAT
Limitations of the Pesticide Toxicity Index 

The high variability in toxicity data should be 

considered when using data from this report or any 

database. For example, the malathion LC50 toxicity 

values for fish (n=146) ranged from 0.19 to 50,200 

ppb. The range of malathion toxicity decreases when 

the data is restricted to a single species like bluegills 

(n=13, 20 to 1,200 ppb) or rainbow trout (n=17, 2.8 to 

234 ppb). The high variation in laboratory toxicity 

tests is due to different factors, including (1) formula 

of pesticide tested, (2) species tested and condition of 

individual organisms used, (3) water conditions (pH, 

temperature) during the testing period, (4) testing 

environment (flow through or static), and (5) individual operator of the test. These factors all contribute 

to the overall variability observed when combining 

data from multiple sources. For applications in whi

certain individual compounds are particularly 

important, special attention should be given to the 

variability in toxicity test results for those compoun

Adjustment of the approach may be merited, such 

examining results with other percentiles of the test 

results, or according to a subset of test results that 

most closely match the needs of a particular 

assessment. 

The problem of limited data can be addressed 

two ways. First, the toxicity data can be expanded 

include published data from other databases and 

reports; however, it would be essential to carefully 

cross-reference to prevent the duplication of data a

to verify that the bioassays are as comparable as 

Figure 2. Pesticide Toxicity Index (PTI) for bluegills in Little Buck Creek, Indiana, and the contributions of selected pesticides. 

Nondetections and other individual values less than a PTI of 0.00001 are not plotted.

0.00001

0.0001

0.001

0.01

0.1

Dec. Feb. Apr. June Aug. Oct. Dec. Feb.

1993

Carbary

Chlorpyr

Diazinon

Malathio

Alachlor

Atrazine

Benflura

Cyanazi

Metolac

Pendime

Prometo

Triflurali

PTI blue

Pesticide 

Toxicity Index for bluegills

EXPLANATIO

no data
8 Pesticide Toxicity Index for Freshwater Aquatic Organisms

possible, a task that could prove difficult. A second 

approach is to reduce the data to a subset of species 

with more data that is most relevant to a particular 

problem. The PTI, for example, can be calculated 

using only warm or cold water species in areas where 

only one of the two groups resides. 

SUMMARY AND CONCLUSIONS

The Pesticide Toxicity Index (PTI) for a 

particular sample is the sum of toxicity quotients 

(measured concentration divided by the median 

toxicity concentration from bioassays) for each 

detected pesticide. Qualifying toxicity data were found 

for one or more types of test organisms for 75 of the 

83 pesticide compounds measured in NAWQA 

samples, but with a wide range of bioassays per 

compound (1 to 65). There were a total of 2,824 

bioassays for the 75 compounds, including 287 

48-hour EC50 values for freshwater cladocerans, 

585 96-hour LC50 values for freshwater bent

invertebrates, and 1,952 96-hour LC50 value

freshwater fish.

While the PTI does not determine whe

in a sample is toxic, it can be used to rank o

the toxicity of samples or sites on a relative 

use in further analysis or additional assessm

particular, the PTI may be useful as a basis 

comparing the potential significance of pest

different streams on a common basis, for ev

relations between pesticide exposure and ob

biological conditions, and prioritizing wher

studies are needed. Initial example applicati

indicate that high relative toxicity may some

occur during seasons when total pesticide 

concentrations are not particularly high.

The PTI has several limitations, which 

carefully considered in applications: 

• The PTI is a relative ranking system that i

that a sample is likely to be more or les

Figure 3. Pesticide Toxicity Index (PTI) for bluegills in Little Buck Creek, Indiana, compared with total pesticide concentration.

0

2

4

6

8

10

12

14

16

18

20

0

0.002

0.004

0.006

0.008

0.01

0.012

0.014

Dec. Feb. Apr. June Aug. Oct. Dec. Feb.

Total pesticide concentration, in micrograms per liter

Pesticide Toxicity Index for bluegills

1993

Total pesticide 

concentration

PTI bluegills
References Cited 

than another sample, but does not necessarily 

demonstrate actual toxicity. 

• Toxicity values are based on short-term laboratory 

experiments with EC50 or LC50 endpoints; 

therefore, the PTI does not incorporate long-term 

chronic endpoints. 

• Several environmental factors, which are not 

accounted for by the PTI, can modify the toxicity 

and bioavailability of pesticides, including 

dissolved organic carbon, particulates, and 

temperature. 

• This PTI is based on the simplifying assumption that 

pesticide toxicity is additive and there is no 

chemical interaction (synergism, antagonism), 

which may not be the case in the environment. 

The actual utility of the PTI for evaluating 

effects of pesticides on aquatic biota in streams can 

only be determined by testing the correlation of PTI 

values with various measures of the nature and health 

of aquatic biota. 

REFERENCES CITED

Davis, G., Fort, D., Hansen, B., Irwin, F., Jones, B., Jones, 

S., Socha, A., Wilson, R., Haaf, B., Gray, G., and 

Hoffman, B., 1997, Framework for chemical ranking 

and scoring systems, chap. 1 in Swanson, M.B., and 

Socha, A.C., eds., Chemical ranking and scoring: 

Guidelines for relative assessments of chemical: 

Proceedings of the Pellston Workshop on Chemical 

Ranking and Scoring, 11–16 February 1995, 

Sandestin, Florida: Pensacola, Fla., SETAC Press, 

SETAC special publication series, p. 1–30.

Gilliom, R.J., Alley, W.M., and Gurtz, M.E., 1995, Design 

of the National Water-Quality Assessment Program: 

Occurrence and distribution of water-quality conditions: U.S. Geological Survey Circular 1112, 33 p. 

Hirsch, R.M., Alley, W.M., and Wilber, W.G., 1988, 

Concepts for a National Water-Quality Assessment 

Program: U.S. Geological Survey Circular 1021, 42 p.

Kimerle, R., Barnthouse, L., Brown, R., de Beyssac, B.C., 

Gilbertson, M., Monk, K., Poremski, H.J., Purdy, R., 

Reinert, K., Rolland, R., and Zeeman, M, 1997, 

Ecological effects, chap. 4 in Swanson, M.B., and 

Socha, A.C., eds., Chemical ranking and scoring—

Guidelines for relative assessments of chemical: 

Proceedings of the Pellston Workshop on Chemica

Ranking and Scoring, 11–16 February 1995, 

Sandestin, Florida: Pensacola, Fla., SETAC Press, 

SETAC special publication series, 154 p.

Larson, S.J., Gilliom, R.J., and Capel, P.D., 1999, Pestici

in Streams of the United States—Initial Results fro

the National Water-Quality Assessment Program: U

Geological Survey Water-Resources Investigations 

Report 98-4222, 92 p.

Leahy, P.P., Rosenshein, J.S., and Knopman, D.S., 1990

Implementation plan for the National Water-Qualit

Assessment Program: U.S. Geological Survey Ope

File Report 90-174, 10 p.

Shelton, L.R., 1994. Field guide for collecting and 

processing stream-water samples for the National 

Water-Quality Assessment Program, U.S. Geologic

Survey Open-File Report 94-455, 45 p. 

Sutter, G.W., 1995. Introduction of ecological risk 

assessment for aquatic toxic effects, chap. 28 in Ra

G.M., and Petrocelli, S.R., eds., Fundamentals of 

aquatic toxicology: Methods and applications: 

Washington, D.C., Taylor and Francis Publishers, 

p. 803–816. 

Swanson, M.B., and Socha, A.C., eds., 1997, Chemical 

ranking and scoring: Guidelines for relative assessments of chemical: Proceedings of the Pellston 

Workshop on Chemical Ranking and Scoring, 

11–16 February 1995, Sandestin, Florida: Pensaco

Fla., SETAC Press, SETAC special publication seri

154 p.

U.S. Environmental Protection Agency, ECOTOX datab

system: accessed December 12, 2000, at URL http

www.epa.gov/med/databases/databases.html#aqu

———1990, Method 8290: Polychlorinated dibenzodiox

(PCDDs) and polychlorinated dibenzofurans (PCD

by high-resolution gas chromatography/high-resolu

tion mass spectrometry (HRGC/HRMS): Washingt

D.C., U.S. Environmental Protection Agency 8290

64 p.
TABLES
 Tables 

Compound Chemical class Use CAS number

2-(2,4,5-Trichlorophenoxy) propionic acid Chlorophenoxy acid Herbicide 93-72-1

2,4,5-T do. Herbicide 93-76-5

2,4-D do. Herbicide 94-75-7

2,4-DB do. Herbicide 94-82-6

2,6-Diethylaniline Alachlor degradate 579-66-8

3-Hydroxycarbofuran Carbofuran degradate 16655-82-6

4,6-Dinitro-2-methylphenol Miscellaneous Herbicide 534-52-1

Acetochlor Acetanilide Herbicide 34256-82-1

Acifluorfen Benzoic acid derivative Herbicide 50594-66-6

Alachlor Acetanilide Herbicide 15972-60-8

Aldicarb Carbamate Insecticide 116-06-3

Aldicarb sulfone Carbamate, aldicarb degradate 1646-88-4

Aldicarb sulfoxide Aldicarb degradate 1646-87-3

α-HCH Organochlorine Insecticide 319-84-6

Atrazine Triazine Herbicide 1912-24-9

Azinphos-methyl Organophophorus Insecticide 86-50-0

Benfluralin Dinitroaniline Herbicide 1861-40-1

Bentazon Miscellaneous Herbicide 25057-89-0

Bromacil Uracil Herbicide 314-40-9

Bromoxynil Miscellaneous Herbicide 1689-84-5

Butylate Thiocarbamate Herbicide 2008-41-5

Carbaryl Carbamate Insecticide 63-25-2

Carbofuran do. Insecticide 1563-66-2

Chloramben Chlorobenzoic acid Herbicide 133-90-4

Chlorothalonil Organochlorine Fungicide 1897-45-6

Chlorpyrifos Organophophorus Insecticide 2921-88-2

cis-Permethrin Pyrithroid Insecticide 54774-45-7

Clopyralid Organochlorine Herbicide 1702-17-6

Cyanazine Triazine Herbicide 21725-46-2

Dacthal Chlorobenzoic acid Herbicide 1861-32-1

Dacthal monoacid (MTP) Dacthal degradate 887-54-7

Deethylatrazine Atrazine degradate 6190-65-4

Diazinon Organophosphorus Insecticide 333-41-5

Dicamba Chlorobenzoic acid Herbicide 1918-00-9

Dichlobenil Organochlorine Herbicide 1194-65-6

Dichlorprop (2,4-DP) Chlorophenoxy acid derivate Herbicide 120-36-5

Dieldrin Organochlorine Insecticide 60-57-1

Dinoseb Nitrophenol Herbicide 88-85-7

Disulfoton Organophosphorus Insecticide 298-04-4

Diuron Urea Herbicide 330-54-1

EPTC (Eptam) Thiocarbamate Herbicide 759-94-4

Ethalfluralin Dinitroaniline Herbicide 55283-68-6

Ethoprop Organophosphorus Nematocide 13194-48-4

Fenuron Urea Herbicide 101-42-8

Fluometuron do. Herbicide 2164-17-2

Fonofos Organophosphorus Insecticide 944-22-9

Lindane (γ-HCH) Organochlorine Insecticide 58-89-9

Table 1. Pesticides analyzed in streams for the National Water-Quality Assessment (NAWQA) Program

[do., ditto; CAS, Chemical Abstracts Service; blank cells, not applicable]
12 Pesticide Toxicity Index for Freshwater Aquatic Organisms

Linuron Urea Herbicide 330-55-2

Malathion Organophosphorus Insecticide 121-75-5

MCPA Chlorophenoxy acid Herbicide 94-74-6

MCPB do. Herbicide 94-81-5

Methiocarb Carbamate Insecticide 2032-65-7

Methomyl do. Insecticide 16752-77-5

Metolachlor Acetamilide Herbicide 51218-45-2

Metribuzin Trazine Herbicide 21087-64-9

Molinate Thiocarbamate Herbicide 2212-67-1

Napropamide Amide Herbicide 15299-99-7

Neburon Uraea Herbicide 555-37-3

Norflurazon Amine Herbicide 27314-13-2

Oryzalin Dinitroaniline Herbicide 19044-88-3

Oxamyl Carbamate Insecticide 23135-22-0

p,p′-DDE p,p′-DDT degradate Insecticide 72-55-9

Parathion Organophophorus Insecticide 56-38-2

Parathion-methyl do. Insecticide 298-00-0

Pebulate Thiocarbamate Herbicide 1114-71-2

Pendimethalin Dinitroaniline Herbicide 40487-42-1

Phorate Organophosphorus Insecticide 298-02-2

Picloram Amine Herbicide 1918-02-1

Prometon Triazine Herbicide 1610-18-0

Propachlor Acetanilide Herbicide 1918-16-7

Propanil Amide Herbicide 709-98-8

Propargite Sulfite ester Insecticide 2312-35-8

Propham Carbamate Herbicide 122-42-9

Propoxur do. Insecticide 114-26-1

Propyzamide (Pronamide) Amide Herbicide 23950-58-5

Simazine Triazine Herbicide 122-34-9

Tebuthiuron Urea Herbicide 34014-18-1

Terbacil Uracil Herbicide 5902-51-2

Terbufos Organophosphorus Insecticide 13071-79-9

Thiobencarb Thiocarbamate Herbicide 28249-77-6

Triallate do. Herbicide 2303-17-5

Triclopyr Organochlorine Herbicide 55335-06-3

Trifluralin Dinitroaniline Herbicide 1582-09-8

Compound Chemical class Use CAS number

Table 1. Pesticides analyzed in streams for the National Water-Quality Assessment (NAWQA) Program—Continued
 Tables 13

Endpoint Taxa Species Name Compound N Minimum

(ppb)

Median

(ppb)

Maximum

(ppb)

EC50 Crustacea Ceriodaphnia dubia Water flea Carbaryl 1 — 3.1 —

do. do. do. Carbofuran 1 — 2.0 —

do. Chydorus ovalis do. Lindane 1 — 1,100.0 —

do. Daphnia carinata do. Carbaryl 1 — 35.0 —

do. do. do. Dieldrin 1 — 130.0 —

do. do. do. Lindane 1 — 100.0 —

do. do. do. Malathion 1 — 100.0 —

do. Daphnia laevis do. Aldicarb 2 51.0 58.0 65.0

do. do. do. Aldicarb sulfone 2 369.0 462.5 556.0

do. do. do. Aldicarb sulfoxide 2 43.0 50.0 57.0

do. Daphnia magna do. 2,4-D 1 — 25,000.0 —

do. do. do. 2,4-DB 1 — 25,000.0 —

do. do. do. 2,6-Dinitro-2-methylphenol 1 — 2,700.0 —

do. do. do. Dichlorprop (2,4-DP) 2 5,400.0 5,825.0 6,250.0

do. do. do. Acetochlor 3 7,200.0 8,200.0 14,000.0

do. do. do. Alachlor 6 7,700.0 21,500.0 35,000.0

do. do. do. Aldicarb 1 — 410.7 —

do. do. do. Aldicarb sulfone 1 — 280.0 —

do. do. do. Atrazine 2 6,900.0 60,950.0 115,000.0

do. do. do. Azinphos-methyl 4 1.1 1.6 4.4

do. do. do. Benfluralin 1 — 2,186.0 —

do. do. do. Bromacil 1 — 121,000.0 —

do. do. do. Bromoxynil 24 41.0 126.5 74,000.0

do. do. do. Butylate 2 11,900.0 85,250.0 158,600.0

do. do. do. Carbaryl 9 2.8 7.2 7,100.0

do. do. do. Carbofuran 5 29.0 41.0 86.1

do. do. do. Chlorothalonil 4 70.0 97.0 172.0

do. do. do. Chlorpyrifos 2 0.1 0.9 1.7

do. do. do. Cyanazine 9 35,500.0 84,000.0 106,000.0

do. do. do. DCPA (Dacthal) 2 27,000.0 82,500.0 138,000.0

do. do. do. Diazinon 10 0.5 1.2 1.5

[do., ditto; EC50, concentration at which 50 percent of test organisms exhibited nonlethal responses; LC50, concentration at which 50 percent mortality occurred; N, number of 

bioassays; ppb, part per billion; —, no data]
Pesticide Toxicity Index for Freshwater Aquatic Organisms

EC50 Crustacea Daphnia magna Water flea Dicamba 2 110,700.0 430,350.0 750,000.0

do. do. do. Dichlobenil 1 — 6,200.0 —

do. do. do. Disulfoton 1 — 13.0 —

do. do. do. Diuron 1 — 8,400.0 —

do. do. do. EPTC 3 6,400.0 7,500.0 14,150.0

do. do. do. Ethalfluralin 1 — 60.0 —

do. do. do. Ethoprop 3 43.9 93.0 690,000.0

do. do. do. Ethyl parathion 7 0.7 1.3 7.2

do. do. do. Fonofos 3 2.0 8.4 15.5

do. do. do. Lindane 8 516.0 4,145.0 8,000.0

do. do. do. Linuron 4 120.0 240.0 1,100.0

do. do. do. Malathion 7 1.0 1.7 2.2

do. do. do. Methiocarb 1 — 19.0 —

do. do. do. Methomyl 6 7.6 8.8 3,200.0

do. do. do. Methyl parathion 8 0.1 8.3 28.2

do. do. do. Metolachlor 3 23,500.0 25,100.0 26,000.0

do. do. do. Metribuzin 3 4,180.0 4,200.0 98,500.0

do. do. do. Molinate 3 4,700.0 19,400.0 24,000.0

do. do. do. Napropamide 2 14,300.0 19,500.0 24,700.0

do. do. do. Oryzalin 1 — 1,500.0 —

do. do. do. Oxamyl 5 420.0 1,950.0 5,700.0

do. do. do. Pebulate 1 — 6,830.0 —

do. do. do. Pendimethalin 2 280.0 2,690.0 5,100.0

do. do. do. Phorate 4 18.2 21.8 37.0

do. do. do. Prometon 3 25,700.0 38,000.0 59,800.0

do. do. do. Propachlor 3 6,900.0 7,800.0 13,000.0

do. do. do. Propanil 2 1,200.0 3,950.0 6,700.0

do. do. do. Propargite 2 74.0 82.5 91.0

do. do. do. Propoxur 2 11.0 19.1 27.2

do. do. do. Simazine 2 1,100.0 1,100.0 1,100.0

do. do. do. Tebuthiuron 1 — 297,000.0 —

do. do. do. Terbacil 1 — 65,000.0 —

do. do. do. Terbufos 4 0.3 3.4 13.0

do. do. do. Thiobencarb 4 101.0 335.0 1,200.0

do. do. do. Triallate 2 91.0 260.5 430.0

Endpoint Taxa Species Name Compound N Minimum

(ppb)

Median

(ppb)

Maximum

(ppb)
Tables 15

EC50 Crustacea Daphnia magna Water flea Trifluralin 1 — 560.0 —

do. do. do. α-HCH 2 800.0 900.0 1,000.0

do. Daphnia pulex do. 2,4-D 1 — 3,200.0 —

do. do. do. 2,6-Dinitro-2-methylphenol 1 — 145.0 —

do. do. do. Alachlor 2 9,000.0 9,700.0 10,400.0

do. do. do. Atrazine 2 36,500.0 41,500.0 46,500.0

do. do. do. Carbaryl 3 6.4 6.4 6.4

do. do. do. Carbofuran 2 35.0 40.0 45.0

do. do. do. Diazinon 3 0.8 0.8 0.9

do. do. do. Dichlobenil 2 3,700.0 3,700.0 3,700.0

do. do. do. Dieldrin 3 190.0 250.0 251.0

do. do. do. Diuron 3 1,400.0 1,400.0 1,400.0

do. do. do. Ethyl parathion 3 0.6 0.6 0.6

do. do. do. Lindane 3 460.0 460.0 460.0

do. do. do. Malathion 3 1.8 1.8 1.8

do. do. do. Propanil 1 — 11,400.0 —

do. do. do. Propham 2 8,000.0 9,000.0 10,000.0

do. do. do. Trifluralin 3 240.0 625.0 625.0

do. Moina australiensis do. Molinate 1 — 2,400.0 —

do. Simocephalus serrulatus do. 2,4-D 1 — 4,900.0 —

do. do. do. Carbaryl 2 7.6 7.6 7.6

do. do. do. Diazinon 3 1.4 1.4 1.8

do. do. do. Dichlobenil 3 5,800.0 5,800.0 5,800.0

do. do. do. Dieldrin 3 190.0 240.0 240.0

do. do. do. Diuron 2 2,000.0 2,000.0 2,000.0

do. do. do. Ethyl parathion 4 0.4 0.4 0.5

do. do. do. Lindane 4 520.0 520.0 880.0

do. do. do. Malathion 4 0.6 3.5 6.2

do. do. do. Methyl parathion 2 0.4 0.4 0.4

do. do. do. Propham 2 10,000.0 10,000.0 10,000.0

do. do. do. Trifluralin 3 450.0 900.0 900.0

do. Simocephalus sp. do. Diazinon 1 — 1.4 —

do. do. do. Diuron 1 — 2,000.0 —

Endpoint Taxa Species Name Compound N Minimum

(ppb)

Median

(ppb)

Maximum

(ppb)
Pesticide Toxicity Index for Freshwater Aquatic Organisms

LC50 Crustacea Simocephalus vetulus do. Chlorpyrifos 1 — 0.4 —

Annelida Branchiura sowerbyi Oligochaete Malathion 1 — 4,570.0 —

do. Lumbriculus variegatus do. Diazinon 1 — 6,160.0 —

do. do. do. Propoxur 1 — 146,000.0 —

do. Tubificidae do. Dieldrin 1 — 6,710.0 —

do. do. do. Ethyl parathion 1 — 5,230.0 —

do. do. do. Malathion 1 — 16,700.0 —

Crustacea Acartia tonsa Calanoid copepod Atrazine 1 — 94.0 —

do. do. do. Lindane 1 — 17.0 —

do. do. do. Methomyl 1 — 410.0 —

do. Artemia salina Brine shrimp Dieldrin 2 65.0 82.5 100.0

do. do. do. α-HCH 1 — 500.0 —

do. Asellus aquaticus Aquatic sowbug Lindane 1 — 375.0 —

do. Asellus brevicaudus do. Azinphos-methyl 3 21.0 21.0 21.0

do. do. do. Carbaryl 3 240.0 280.0 280.0

do. do. do. Dichlobenil 2 35,000.0 35,000.0 35,000.0

do. do. do. Dieldrin 2 5.0 5.0 5.0

do. do. do. Diuron 1 — 15,500.0 —

do. do. do. EPTC 2 23,000.0 23,000.0 23,000.0

do. do. do. Ethyl parathion 3 213.0 600.0 2,130.0

do. do. do. Lindane 3 10.0 10.0 10.0

do. do. do. Malathion 3 3,000.0 3,000.0 3,000.0

do. do. do. Oryzalin 1 — 400.0 —

do. Asellus communis do. Diazinon 1 — 21.0 —

do. Caridina rajadhari Freshwater prawn Carbofuran 1 — 0.3 —

do. do. do. Lindane 1 — 31.3 —

do. Cyclops strenuus Copepod Methomyl 1 — 190.0 —

do. Cypridopsis vidua Seed shrimp Lindane 1 — 3.2 —

do. Gammarus fasciatus Scud 2,4-D 1 — 2,400.0 —

do. do. do. 2,6-Dinitro-2-methylphenol 1 — 1,100.0 —

do. do. do. Azinphos-methyl 4 0.1 0.1 0.4

do. do. do. Benfluralin 2 1,100.0 1,100.0 1,100.0

do. do. do. Butylate 4 10,000.0 11,000.0 15,000.0

Endpoint Taxa Species Name Compound N Minimum

(ppb)

Median

(ppb)

Maximum

(ppb)
Tables 17

LC50 Crustacea Gammarus fasciatus Scud Carbaryl 3 26.0 26.0 26.0

do. do. do. Chlorpyrifos 1 — 0.3 —

do. do. do. Cyanazine 2 2,000.0 2,000.0 2,000.0

do. do. do. Diazinon 2 0.2 0.2 0.2

do. do. do. Dichlobenil 1 — 10,000.0 —

do. do. do. Dieldrin 3 600.0 640.0 640.0

do. do. do. Dinoseb 1 — 1,800.0 —

do. do. do. Disulfoton 5 21.0 52.0 27,000.0

do. do. do. Diuron 3 160.0 160.0 700.0

do. do. do. EPTC 4 23,000.0 44,500.0 66,000.0

do. do. do. Ethyl parathion 10 0.3 1.3 4.5

do. do. do. Lindane 4 10.0 10.0 11.0

do. do. do. Malathion 5 0.5 0.8 0.9

do. do. do. Methyl parathion 2 3.8 3.8 3.8

do. do. do. Molinate 2 300.0 2,400.0 4,500.0

do. do. do. Oryzalin 1 — 190.0 —

do. do. do. Pebulate 2 10,000.0 10,000.0 10,000.0

do. do. do. Phorate 6 0.6 0.7 4.0

do. do. do. Picloram 1 — 27.0 —

do. do. do. Propanil 1 — 16,000.0 —

do. do. do. Propham 1 — 19,000.0 —

do. do. do. Propoxur 1 — 50.0 —

do. do. do. Trifluralin 3 1,000.0 2,200.0 2,200.0

do. Gammarus fossarum do. Ethyl parathion 1 — 2.5 —

do. Gammarus italicus do. Alachlor 1 — 19,700.0 —

do. do. do. Aldicarb 1 — 420.0 —

do. do. do. Atrazine 1 — 10,100.0 —

do. do. do. Azinphos-methyl 1 — 0.2 —

do. do. do. Carbaryl 1 — 28.0 —

do. do. do. Carbofuran 1 — 12.0 —

do. do. do. Lindane 1 — 26.0 —

do. do. do. Methomyl 1 — 47.0 —

Endpoint Taxa Species Name Compound N Minimum

(ppb)

Median

(ppb)

Maximum

(ppb)
Pesticide Toxicity Index for Freshwater Aquatic Organisms

LC50 Crustacea Gammarus italicus Scud Methyl parathion 1 — 2.9 —

do. do. do. Molinate 1 — 2,200.0 —

do. do. do. Oxamyl 1 — 220.0 —

do. do. do. Propoxur 1 — 50.0 —

do. Gammarus lacustris do. Azinphos-methyl 4 0.1 0.1 0.2

do. do. do. Carbaryl 3 16.0 22.0 22.0

do. do. do. Chlorpyrifos 3 0.1 0.1 0.1

do. do. do. Diazinon 2 170.0 185.0 200.0

do. do. do. Dicamba 2 3,900.0 3,900.0 3,900.0

do. do. do. Dichlobenil 3 11,000.0 11,000.0 11,000.0

do. do. do. Dieldrin 3 460.0 700.0 700.0

do. do. do. Disulfoton 3 52.0 240.0 240.0

do. do. do. Diuron 1 — 160.0 —

do. do. do. Ethyl parathion 5 3.5 3.5 12.8

do. do. do. Lindane 3 48.0 88.0 88.0

do. do. do. Malathion 3 1.6 1.6 1.8

do. do. do. Molinate 1 — 4,500.0 —

do. do. do. Phorate 2 9.0 9.0 9.0

do. do. do. Propham 1 — 10,000.0 —

do. do. do. Propoxur 3 34.0 34.0 34.0

do. do. do. Simazine 2 13,000.0 13,000.0 13,000.0

do. do. do. Trifluralin 1 — 2,200.0 —

do. Gammarus pseudolimnaeus do. Carbaryl 5 7.0 13.0 16.0

do. do. do. Chlorpyrifos 1 — 0.2 —

do. do. do. DCPA (Dacthal) 1 — 6,200.0 —

do. do. do. Diazinon 1 — 2.0 —

do. do. do. Methomyl 6 720.0 920.0 1,050.0

do. do. do. Permethrin 1 — 0.2 —

do. do. do. Terbufos 3 0.2 0.2 1.3

do. do. do. Thiobencarb 3 720.0 1,000.0 1,000.0

do. Gammarus pulex do. Atrazine 1 — 14,900.0 —

do. do. do. Carbofuran 1 — 9.0 —

Endpoint Taxa Species Name Compound N Minimum

(ppb)

Median

(ppb)

Maximum

(ppb)
Tables 19

LC50 Crustacea Gammarus pulex Scud Chlorpyrifos 1 — 0.1 —

do. do. do. Ethyl parathion 1 — 3.2 —

do. do. do. Lindane 8 5.5 18.8 225.0

do. do. do. Methomyl 1 — 760.0 —

do. Hyalella azteca Scud Atrazine 1 — 14,700.0 —

do. do. do. Azinphos-methyl 1 — 0.3 —

do. do. do. Chlorpyrifos 2 0.0 0.1 0.1

do. do. do. Diazinon 1 — 6.5 —

do. Macrobrachium dayanum Freshwater prawn Carbaryl 1 — 35.2 —

do. Macrobrachium rosenbergii Giant river prawn Malathion 2 9.0 11.0 13.0

do. Neomysis mercedis Opposum Shrimp Carbofuran 4 2.7 12.9 27.0

do. do. do. Malathion 4 1.4 1.9 3.8

do. do. do. Methyl parathion 2 0.2 0.2 0.2

do. Orconectes immunis Crayfish Carbaryl 1 — 2,870.0 —

do. do. do. Chlorpyrifos 1 — 6.0 —

do. Orconectes nais do. Carbaryl 2 8.6 504.3 1,000.0

do. do. do. Dieldrin 2 740.0 740.0 740.0

do. do. do. Ethyl parathion 4 0.0 0.0 15.0

do. do. do. Malathion 3 50.0 180.0 180.0

do. do. do. Methyl parathion 2 15.0 15.0 15.0

do. do. do. Phorate 2 50.0 50.0 50.0

do. do. do. Thiobencarb 1 — 2,000.0 —

do. Palaemonetes kadiakensis Grass shrimp Azinphos-methyl 5 0.1 0.2 1.2

do. do. do. Carbaryl 4 5.6 5.6 120.0

do. do. do. Dieldrin 1 — 20.0 —

do. do. do. Disulfoton 3 3.9 3.9 38.0

do. do. do. Ethyl parathion 4 1.5 1.5 5.0

do. do. do. Malathion 4 12.0 51.0 90.0

do. do. do. Methiocarb 2 110.0 110.0 110.0

do. do. do. Molinate 1 — 15,900.0 —

do. do. do. Trifluralin 1 — 37.0 —

do. Palaemonetes pugio Daggerblade grass shrimp Atrazine 1 — 9,000.0 —

Endpoint Taxa Species Name Compound N Minimum

(ppb)

Median

(ppb)

Maximum

(ppb)
Pesticide Toxicity Index for Freshwater Aquatic Organisms

LC50 Crustacea Palaemonetes pugio Daggerblade grass shrimp Azinphos-methyl 1 — 1.3 —

do. do. do. Chlorpyrifos 4 0.4 0.6 83.0

do. do. do. Lindane 2 4.4 4.4 4.4

do. do. do. Malathion 1 — 10.4 —

do. do. do. Propargite 1 — 101.0 —

do. do. do. Thiobencarb 1 — 380.0 —

do. do. do. Trifluralin 1 — 638.5 —

do. Palaemonetes sp. Grass shrimp Terbufos 12 4.6 5.7 12.0

do. Palaemonetes vulgaris Marsh grass shrimp Dieldrin 1 — 50.0 —

do. do. do. Lindane 1 — 10.0 —

do. do. do. Malathion 1 — 82.0 —

do. do. do. Methomyl 1 — 49.0 —

do. do. do. Methyl parathion 1 — 3.0 —

do. Procambarus acutus acutus Crayfish Methiocarb 1 — 1,300.0 —

do. do. White river crayfish Azinphos-methyl 1 — 40.0 —

do. do. do. Carbaryl 1 — 500.0 —

do. do. do. Carbofuran 1 — 500.0 —

do. do. do. Chlorpyrifos 1 — 2.0 —

do. do. do. Malathion 1 — 50,000.0 —

do. do. do. Methiocarb 1 — 1,300.0 —

do. do. do. Methomyl 1 — 1,000.0 —

do. do. do. Methyl parathion 1 — 3.0 —

do. Procambarus blandingii Crayfish Permethrin 1 — 210.0 —

do. Procambarus clarkii Red swamp crayfish Carbaryl 1 — 1,000.0 —

do. do. do. Chlorpyrifos 1 — 21.0 —

do. do. do. Malathion 1 — 49,170.0 —

do. do. do. Molinate 2 6,130.0 10,065.0 14,000.0

do. do. do. Propoxur 1 — 1,430.0 —

do. do. do. Terbufos 1 — 5.9 —

do. do. do. Thiobencarb 3 200.0 6,500.0 9,240.0

do. do. do. Trifluralin 3 12,000.0 13,000.0 26,000.0

do. Procambarus simulans Crayfish Carbaryl 1 — 2,430.0 —

Endpoint Taxa Species Name Compound N Minimum

(ppb)

Median

(ppb)

Maximum

(ppb)
Tables 21

LC50 Crustacea Procambarus simulans Crayfish Molinate 1 — 21,800.0 —

do. Procambarus sp. do. Alachlor 1 — 19,500.0 —

do. do. do. Azinphos-methyl 2 56.0 56.0 56.0

do. do. do. Carbaryl 2 1.9 951.0 1,900.0

do. do. do. Terbufos 1 — 8.0 —

Fish Ameiurus melas Black bullhead Atrazine 1 — 35,000.0 —

do. do. do. Azinphos-methyl 3 3,500.0 3,500.0 3,500.0

do. do. do. Carbaryl 3 20,000.0 20,000.0 20,000.0

do. do. do. Diazinon 1 — 8,000.0 —

do. do. do. Fluometuron 1 — 55,000.0 —

do. do. do. Lindane 3 64.0 64.0 64.0

do. do. do. Malathion 3 11,700.0 12,900.0 12,900.0

do. do. do. Methyl parathion 3 6,640.0 6,640.0 6,640.0

do. do. do. Prometon 1 — 20,000.0 —

do. do. do. Simazine 1 — 65,000.0 —

do. Ameiurus natalis Yellow bullhead do. 1 — 110,000.0 —

do. Ameiurus nebulosus Brown bullhead Molinate 1 — 34,000.0 —

do. Ameiurus sp. Bullhead catfish Atrazine 2 7,600.0 21,300.0 35,000.0

do. do. do. Diazinon 1 — 8,000.0 —

do. do. do. Fluometuron 2 44,000.0 49,500.0 55,000.0

do. do. do. Prometon 1 — 20,000.0 —

do. do. do. Simazine 1 — 65,000.0 —

do. Anguilla anguilla European eel Chlorpyrifos 1 — 540.0 —

do. do. do. Diazinon 6 80.0 82.5 86.0

do. do. do. Lindane 10 320.0 545.0 680.0

do. do. do. Methyl parathion 1 — 4,120.0 —

do. Anguilla rostrata American eel 2,4,5-T 1 — 43,700.0 —

do. do. do. 2,4-D 1 — 300,600.0 —

do. do. do. Dieldrin 1 — 0.9 —

do. do. do. Lindane 1 — 56.0 —

do. do. do. Malathion 2 82.0 291.0 500.0

do. do. do. Methyl parathion 2 6,300.0 11,600.0 16,900.0

Endpoint Taxa Species Name Compound N Minimum

(ppb)

Median

(ppb)

Maximum

(ppb)
Pesticide Toxicity Index for Freshwater Aquatic Organisms

LC50 Fish Carassius auratus Goldfish Aldicarb 1 — 7,400.0 —

do. do. do. Atrazine 1 — 60,000.0 —

do. do. do. Azinphos-methyl 7 1,040.0 2,400.0 4,270.0

do. do. do. Benfluralin 2 800.0 805.0 810.0

do. do. do. Carbaryl 3 13,200.0 13,200.0 16,700.0

do. do. do. Carbofuran 1 — 10,250.0 —

do. do. do. Diazinon 1 — 9,000.0 —

do. do. do. Dichlobenil 2 7,680.0 7,740.0 7,800.0

do. do. do. Dieldrin 2 1.8 21.4 41.0

do. do. do. Disulfoton 2 7,200.0 7,200.0 7,200.0

do. do. do. EPTC 1 — 26,670.0 —

do. do. do. Ethalfluralin 1 — 260.0 —

do. do. do. Ethoprop 2 7,700.0 10,650.0 13,600.0

do. do. do. Ethyl parathion 4 1,830.0 2,215.0 2,700.0

do. do. do. Lindane 4 131.0 131.0 152.0

do. do. do. Malathion 6 790.0 6,925.0 10,700.0

do. do. do. Methyl parathion 4 9,000.0 9,000.0 12,000.0

do. do. do. Molinate 1 — 30,300.0 —

do. do. do. Oxamyl 1 — 27,500.0 —

do. do. do. Pronamide 1 — 350,000.0 —

do. do. do. Propoxur 1 — 50,000.0 —

do. do. do. Trifluralin 2 145.0 145.0 145.0

do. Centrarchidae Sunfish family Simazine 5 14,300.0 56,000.0 695,000.0

do. Clarias batrachus Walking catfish 2,4-D 1 — 60,000.0 —

do. do. do. Carbaryl 3 20,000.0 46,850.0 107,660.0

do. do. do. Diazinon 1 — 4,791.6 —

do. do. do. Dieldrin 1 — 1.0 —

do. do. do. Lindane 2 1.1 8,000.6 16,000.0

do. do. do. Malathion 2 47.0 6,023.5 12,000.0

do. Coregonus lavaretus Whitefish Atrazine 2 11,200.0 18,750.0 26,300.0

do. Ctenopharyngodon idella Grass carp Dichlobenil 1 — 9,400.0 —

do. do. do. Diuron 1 — 31,000.0 —

Endpoint Taxa Species Name Compound N Minimum

(ppb)

Median

(ppb)

Maximum

(ppb)
Tables 23

LC50 Fish Cyprinella lutrensis Red shiner Carbaryl 1 — 9,200.0 —

do. do. do. Malathion 1 — 25.0 —

do. Cyprinodon variegatus Sheepshead minnow Acetochlor 2 2,100.0 3,000.0 3,900.0

do. do. do. Aldicarb 2 41.0 105.5 170.0

do. do. do. Atrazine 4 2,000.0 7,850.0 16,200.0

do. do. do. Azinphos-methyl 2 1.9 2.3 2.7

do. do. do. Bromacil 1 — 162,800.0 —

do. do. do. Butylate 1 — 2,700.0 —

do. do. do. Carbaryl 3 1,200.0 2,200.0 2,600.0

do. do. do. Carbofuran 1 — 386.0 —

do. do. do. Chlorothalonil 1 — 32.0 —

do. do. do. Chlorpyrifos 4 136.0 205.0 270.0

do. do. do. Diazinon 3 150.0 1,470.0 1,470.0

do. do. do. Disulfoton 1 — 1,000.0 —

do. do. do. Diuron 1 — 6,700.0 —

do. do. do. Ethalfluralin 1 — 240.0 —

do. do. do. Ethoprop 2 180.0 569.0 958.0

do. do. do. Fluometuron 2 48,000.0 51,650.0 55,300.0

do. do. do. Lindane 2 100.0 102.0 103.9

do. do. do. Linuron 1 — 890.0 —

do. do. do. Malathion 3 33.0 51.0 55.0

do. do. do. Methomyl 2 960.0 1,060.0 1,160.0

do. do. do. Methyl parathion 2 3,400.0 7,700.0 12,000.0

do. do. do. Metolachlor 2 7,900.0 8,850.0 9,800.0

do. do. do. Metribuzin 1 — 85,000.0 —

do. do. do. Molinate 1 — 12,000.0 —

do. do. do. Napropamide 1 — 14,000.0 —

do. do. do. Norflurazon 1 — 9,580.0 —

do. do. do. Oxamyl 1 — 2,600.0 —

do. do. do. Pendimethalin 2 710.0 1,205.0 1,700.0

do. do. do. Permethrin 2 7.8 47.9 88.0

do. do. do. Phorate 3 1.3 4.0 8.2

Endpoint Taxa Species Name Compound N Minimum

(ppb)

Median

(ppb)

Maximum

(ppb)
Pesticide Toxicity Index for Freshwater Aquatic Organisms

LC50 Fish Cyprinodon variegatus Sheepshead minnow Prometon 1 — 47,300.0 —

do. do. do. Propanil 1 — 4,600.0 —

do. do. do. Propargite 1 — 60.0 —

do. do. do. Terbacil 1 — 108,000.0 —

do. do. do. Terbufos 9 1.6 4.0 4.6

do. do. do. Thiobencarb 5 658.0 1,370.0 1,400.0

do. do. do. Trifluralin 1 — 160.0 —

do. Cyprinus carpio Carp 2,4,5-T 2 5,300.0 23,200.0 41,100.0

do. do. do. 2,4-D 9 5,100.0 21,450.0 270,000.0

do. do. do. Alachlor 1 — 4,600.0 —

do. do. do. Atrazine 1 — 18,800.0 —

do. do. do. Azinphos-methyl 3 695.0 695.0 695.0

do. do. do. Bentazon 1 — 978,000.0 —

do. do. do. Carbaryl 11 1,190.0 3,300.0 5,280.0

do. do. do. Carbofuran 7 160.0 1,290.0 3,000.0

do. do. do. Diazinon 2 3,430.0 4,200.0 4,970.0

do. do. do. Dichlobenil 1 — 10,900.0 —

do. do. do. Dieldrin 1 — 600.0 —

do. do. do. Diuron 1 — 2,900.0 —

do. do. do. Ethoprop 1 — 640.0 —

do. do. do. Ethyl parathion 1 — 850.0 —

do. do. do. Fonofos 1 — 88.0 —

do. do. do. Lindane 6 90.0 145.0 13,000.0

do. do. do. MCPA 1 — 59,000.0 —

do. do. do. Malathion 14 2.0 6,590.0 13,800.0

do. do. do. Methyl parathion 4 7,130.0 7,130.0 14,800.0

do. do. do. Molinate 2 29,000.0 35,900.0 42,800.0

do. do. do. Permethrin 1 — 15.0 —

do. do. do. Propoxur 5 3,300.0 7,340.0 10,100.0

do. do. do. Thiobencarb 2 110.0 765.0 1,420.0

do. do. do. Trifluralin 1 — 660.0 —

do. Esox lucius Northern pike Azinphos-methyl 2 0.4 0.4 0.4

Endpoint Taxa Species Name Compound N Minimum

(ppb)

Median

(ppb)

Maximum

(ppb)
Tables 25

LC50 Fish Esox lucius Northern pike Phorate 2 110.0 110.0 110.0

do. Fundulus diaphanus Banded killifish 2,4,5-T 1 — 17,400.0 —

do. do. do. 2,4-D 1 — 26,700.0 —

do. do. do. Malathion 1 — 240.0 —

do. do. do. Methyl parathion 1 — 15,200.0 —

do. Fundulus heteroclitus Mummichog Azinphos-methyl 6 22.7 41.2 85.1

do. do. do. Chlorpyrifos 1 — 4.7 —

do. do. do. Dieldrin 3 5.0 5.0 16.0

do. do. do. Lindane 2 20.0 40.0 60.0

do. do. do. Malathion 5 22.5 70.0 400.0

do. do. do. Methyl parathion 2 8,000.0 33,000.0 58,000.0

do. Gambusia affinis Western mosquitofish 2-(2,4,5-Trichlorophenoxy) 

propionic acid

1 — 350.0 —

do. do. do. Azinphos-methyl 1 — 78.0 —

do. do. do. Bentazon 1 — 3,874,000.0 —

do. do. do. Butylate 1 — 8,500.0 —

do. do. do. Carbaryl 3 1,400.0 31,800.0 204,000.0

do. do. do. Carbofuran 1 — 300.0 —

do. do. do. Chlorpyrifos 2 280.0 425.0 570.0

do. do. do. Dicamba 1 — 465,000.0 —

do. do. do. Dieldrin 3 1.5 3.7 31.0

do. do. do. EPTC 1 — 16,370.0 —

do. do. do. Ethyl parathion 2 320.0 1,180.5 2,041.0

do. do. do. Lindane 4 130.0 440.6 1,350.0

do. do. do. Malathion 2 200.0 430.0 660.0

do. do. do. Methyl parathion 1 — 5.0 —

do. do. do. Molinate 1 — 16,400.0 —

do. do. do. Pebulate 1 — 10,000.0 —

do. do. do. Picloram 1 — 120,000.0 —

do. do. do. Trifluralin 1 — 12,000.0 —

do. Gambusia sp. Western mosquitofish Ethyl parathion 1 — 320.0 —

do. Gasterosteus aculeatus Threespine stickleback Azinphos-methyl 2 4.8 8.5 12.1

Endpoint Taxa Species Name Compound N Minimum

(ppb)

Median

(ppb)

Maximum

(ppb)
Pesticide Toxicity Index for Freshwater Aquatic Organisms

LC50 Fish Gasterosteus aculeatus Threespine stickleback Carbaryl 2 399.0 2,194.5 3,990.0

do. do. do. Chlorothalonil 1 — 69.0 —

do. do. do. Chlorpyrifos 1 — 8.5 —

do. do. do. Dieldrin 2 13.1 14.2 15.3

do. do. do. Lindane 2 44.0 47.0 50.0

do. do. do. Malathion 2 76.9 85.5 94.0

do. Gila elegans Bonytail Carbaryl 3 650.0 2,020.0 3,310.0

do. do. do. Malathion 1 — 1,530.0 —

do. Ictalurus punctatus Channel catfish 2,4-D 1 — 7,000.0 —

do. do. do. 2-(2,4,5-Trichlorophenoxy) 

propionic acid

1 — 19,400.0 —

do. do. do. Alachlor 1 — 6,500.0 —

do. do. do. Azinphos-methyl 4 3,220.0 3,290.0 3,290.0

do. do. do. Carbaryl 8 140.0 10,095.0 15,800.0

do. do. do. Carbofuran 2 248.0 248.0 248.0

do. do. do. Chlorothalonil 3 43.0 52.0 430.0

do. do. do. Chlorpyrifos 3 280.0 280.0 806.0

do. do. do. Cyanazine 6 10,400.0 11,300.0 17,400.0

do. do. do. Dieldrin 2 4.5 11.8 19.0

do. do. do. Dinoseb 6 28.0 53.5 118.0

do. do. do. Disulfoton 2 4,700.0 4,700.0 4,700.0

do. do. do. Ethyl parathion 4 2,650.0 2,975.0 3,300.0

do. do. do. Fluometuron 4 600.0 6,070.0 22,500.0

do. do. do. Lindane 4 44.0 44.0 450.0

do. do. do. Linuron 2 1,800.0 2,350.0 2,900.0

do. do. do. Malathion 5 7,620.0 8,970.0 52,200.0

do. do. do. Methomyl 9 300.0 320.0 1,800.0

do. do. do. Methyl parathion 3 5,240.0 5,240.0 5,710.0

do. do. do. Metolachlor 1 — 4,900.0 —

do. do. do. Metribuzin 1 — 3,400.0 —

do. do. do. Molinate 1 — 34,000.0 —

do. do. do. Oxamyl 2 13,500.0 15,500.0 17,500.0

Endpoint Taxa Species Name Compound N Minimum

(ppb)

Median

(ppb)

Maximum

(ppb)
Tables 27

LC50 Fish Ictalurus punctatus Channel catfish Pendimethalin 2 418.0 1,159.0 1,900.0

do. do. do. Permethrin 2 5.4 6.3 7.2

do. do. do. Phorate 3 2.2 280.0 280.0

do. do. do. Picloram 6 1,400.0 14,750.0 74,800.0

do. do. do. Propachlor 2 230.0 255.0 280.0

do. do. do. Propham 1 — 86,500.0 —

do. do. do. Propoxur 1 — 1,300.0 —

do. do. do. Simazine 1 — 85,000.0 —

do. do. do. Terbufos 2 9.6 904.8 1,800.0

do. do. do. Thiobencarb 4 1,800.0 2,285.0 2,300.0

do. do. do. Trifluralin 3 210.0 417.0 2,200.0

do. Jordanella floridae Flagfish Diazinon 3 1,500.0 1,600.0 1,800.0

do. do. do. Malathion 1 — 349.0 —

do. do. do. Picloram 1 — 26,100.0 —

do. Lagodon rhomboides Pinfish Lindane 1 — 30.6 —

do. Leiostomus xanthurus Spot Atrazine 1 — 8,500.0 —

do. Lepomis cyanellus Green sunfish Azinphos-methyl 2 52.0 52.0 52.0

do. do. do. Carbaryl 2 9,460.0 10,330.0 11,200.0

do. do. do. Dichlobenil 2 5,700.0 5,700.0 5,700.0

do. do. do. Dieldrin 3 6.2 8.5 11.0

do. do. do. Ethyl parathion 3 395.0 930.0 1,700.0

do. do. do. Lindane 2 70.0 76.5 83.0

do. do. do. Malathion 3 175.0 600.0 1,460.0

do. do. do. Methyl parathion 2 6,860.0 6,860.0 6,860.0

do. Lepomis gibbosus Pumpkinseed 2,4,5-T 1 — 20,000.0 —

do. do. do. 2,4-D 1 — 94,600.0 —

do. do. do. Malathion 1 — 480.0 —

do. do. do. Methyl parathion 1 — 3,600.0 —

do. do. do. Simazine 1 — 27,000.0 —

do. Lepomis macrochirus Bluegill 2,4-D 4 7,400.0 221,500.0 263,000.0

do. do. do. 2,4-DB 3 7,500.0 7,500.0 16,800.0

do. do. do. 2,6-Dinitro-2-methylphenol 2 230.0 295.0 360.0

Endpoint Taxa Species Name Compound N Minimum

(ppb)

Median

(ppb)

Maximum

(ppb)
Pesticide Toxicity Index for Freshwater Aquatic Organisms

LC50 Fish Lepomis macrochirus Bluegill 2-(2,4,5-Trichlorophenoxy) 

propionic acid

4 9,600.0 12,200.0 86,000.0

do. do. do. Dichlorprop (2,4-DP) 3 830.0 2,400.0 2,400.0

do. do. do. p,p'-DDE 1 — 240.0 —

do. do. do. Acetochlor 3 1,300.0 1,500.0 1,600.0

do. do. do. Alachlor 10 2,800.0 4,950.0 12,400.0

do. do. do. Aldicarb 4 50.0 51.0 450.0

do. do. do. Aldicarb sulfone 1 — 53,000.0 —

do. do. do. Atrazine 7 6,700.0 42,000.0 69,000.0

do. do. do. Azinphos-methyl 17 4.1 7.4 120.0

do. do. do. Benfluralin 3 65.0 420.0 600.0

do. do. do. Bromacil 1 — 127,000.0 —

do. do. do. Bromoxynil 2 4,000.0 13,500.0 23,000.0

do. do. do. Butylate 6 210.0 7,050.0 202,500.0

do. do. do. Carbaryl 26 760.0 6,760.0 290,000.0

do. do. do. Carbofuran 8 80.0 240.0 3,100.0

do. do. do. Chlorothalonil 5 26.3 62.0 386.0

do. do. do. Chlorpyrifos 10 1.3 6.5 108.0

do. do. do. Cyanazine 2 22,500.0 22,500.0 22,500.0

do. do. do. Diazinon 21 22.0 170.0 530.0

do. do. do. Dicamba 2 135,300.0 157,650.0 180,000.0

do. do. do. Dichlobenil 7 6,720.0 10,000.0 14,700.0

do. do. do. Dieldrin 20 2.8 12.5 79.0

do. do. do. Disulfoton 11 8.2 77.0 1,300.0

do. do. do. Diuron 8 2,800.0 6,750.0 84,000.0

do. do. do. EPTC 3 22,400.0 24,800.0 26,700.0

do. do. do. Ethalfluralin 2 32.0 67.0 102.0

do. do. do. Ethoprop 3 300.0 2,070.0 8,900.0

do. do. do. Ethyl parathion 12 18.0 210.5 710.0

do. do. do. Fluometuron 5 13,500.0 48,000.0 96,000.0

do. do. do. Fonofos 9 5.1 6.8 320.0

do. do. do. Lindane 22 25.0 66.5 810.0

Endpoint Taxa Species Name Compound N Minimum

(ppb)

Median

(ppb)

Maximum

(ppb)
Tables 29

LC50 Fish Lepomis macrochirus Bluegill Linuron 3 9,200.0 9,600.0 16,200.0

do. do. do. MCPA 1 — 97,000.0 —

do. do. do. MCPB 1 — 3,300.0 —

do. do. do. Malathion 13 20.0 103.0 1,200.0

do. do. do. Methiocarb 5 110.0 210.0 754.0

do. do. do. Methomyl 18 370.0 850.0 7,700.0

do. do. do. Methyl parathion 9 1,000.0 2,434.0 13,300.0

do. do. do. Metolachlor 1 — 10,000.0 —

do. do. do. Metribuzin 3 75,960.0 92,000.0 131,300.0

do. do. do. Molinate 7 320.0 19,670.0 29,000.0

do. do. do. Napropamide 2 12,000.0 12,650.0 13,300.0

do. do. do. Norflurazon 1 — 16,300.0 —

do. do. do. Oryzalin 1 — 2,880.0 —

do. do. do. Oxamyl 4 5,600.0 6,415.0 10,000.0

do. do. do. Pebulate 1 — 7,900.0 —

do. do. do. Pendimethalin 4 199.0 980.0 90,400.0

do. do. do. Permethrin 14 0.8 9.9 33.4

do. do. do. Phorate 6 1.0 3.4 12.0

do. do. do. Picloram 10 14,500.0 28,450.0 86,100.0

do. do. do. Prometon 3 15,500.0 40,000.0 41,500.0

do. do. do. Propanil 2 5,400.0 9,700.0 14,000.0

do. do. do. Propargite 2 31.0 99.0 167.0

do. do. do. Propham 2 29,000.0 29,000.0 29,000.0

do. do. do. Propoxur 7 4,800.0 6,200.0 180,000.0

do. do. do. Simazine 6 16,000.0 95,000.0 118,000.0

do. do. do. Tebuthiuron 1 — 106,000.0 —

do. do. do. Terbacil 2 102,900.0 107,450.0 112,000.0

do. do. do. Terbufos 7 0.8 1.7 13.3

do. do. do. Thiobencarb 6 560.0 1,700.0 2,500.0

do. do. do. Triallate 3 1,300.0 1,330.0 2,400.0

do. do. do. Trifluralin 7 8.4 58.0 190.0

do. do. Red ear sunfish Azinphos-methyl 1 — 52.0 —

Endpoint Taxa Species Name Compound N Minimum

(ppb)

Median

(ppb)

Maximum

(ppb)
Pesticide Toxicity Index for Freshwater Aquatic Organisms

LC50 Fish Lepomis microlophus Red ear sunfish Carbaryl 1 — 11,200.0 —

do. do. do. Lindane 1 — 83.0 —

do. do. do. Malathion 3 62.0 62.0 170.0

do. do. do. Methyl parathion 1 — 5,170.0 —

do. do. do. Simazine 1 — 54,000.0 —

do. Leuciscus idus Ide Azinphos-methyl 1 — 120.0 —

do. do. Ide Diazinon 2 150.0 150.0 150.0

do. Menidia beryllina Inland silverside 2,4-D 1 — 175,000.0 —

do. do. do. Azinphos-methyl 1 — 22.8 —

do. do. do. Chlorpyrifos 3 4.2 4.2 10.2

do. do. do. Malathion 2 0.2 0.2 0.3

do. do. do. Terbufos 1 — 4.7 —

do. Micropterus dolomieu Smallmouth bass 2,4-D 1 — 3,100.0 —

do. Micropterus salmoides Largemouth bass Azinphos-methyl 3 4.8 4.8 5.0

do. do. do. Carbaryl 3 6,400.0 6,400.0 6,400.0

do. do. do. Dichlobenil 1 — 12,500.0 —

do. do. do. Dieldrin 1 — 3.5 —

do. do. do. Disulfoton 2 60.0 60.0 60.0

do. do. do. Ethyl parathion 3 620.0 620.0 760.0

do. do. do. Lindane 3 32.0 32.0 32.0

do. do. do. Malathion 4 250.0 267.5 285.0

do. do. do. Methomyl 4 760.0 1,005.0 1,250.0

do. do. do. Methyl parathion 3 5,220.0 5,220.0 5,220.0

do. do. do. Phorate 2 5.0 5.0 5.0

do. do. do. Simazine 1 — 46,000.0 —

do. do. do. Trifluralin 2 75.0 75.0 75.0

do. Morone americana White perch 2,4,5-T 1 — 16,400.0 —

do. do. do. 2,4-D 1 — 40,000.0 —

do. do. do. Malathion 1 — 1,100.0 —

do. do. do. Methyl parathion 1 — 14,000.0 —

do. Morone saxatilis Striped bass 2,4,5-T 1 — 14,600.0 —

do. do. do. 2,4-D 1 — 70,100.0 —

Endpoint Taxa Species Name Compound N Minimum

(ppb)

Median

(ppb)

Maximum

(ppb)
Tables 31

LC50 Fish Morone saxatilis Striped bass Carbaryl 3 760.0 1,000.0 2,300.0

do. do. do. Carbofuran 6 130.0 170.0 370.0

do. do. do. Chlorpyrifos 1 — 0.6 —

do. do. do. Dichlobenil 1 — 6,200,000.0 —

do. do. do. Dieldrin 3 1.0 19.7 500.0

do. do. do. Diuron 3 500.0 3,100.0 6,000.0

do. do. do. Ethyl parathion 3 17.8 1,000.0 2,000.0

do. do. do. Lindane 2 7.3 203.7 400.0

do. do. do. Malathion 11 12.0 39.0 240.0

do. do. do. Methyl parathion 4 790.0 4,750.0 14,000.0

do. do. do. Molinate 4 8,100.0 9,400.0 12,000.0

do. do. do. Simazine 2 250.0 411,125.0 822,000.0

do. do. do. Thiobencarb 17 430.0 760.0 1,000.0

do. Mugil cephalus Striped mullet Chlorpyrifos 1 — 5.4 —

do. do. do. Dieldrin 1 — 23.0 —

do. do. do. Lindane 1 — 66.0 —

do. do. do. Malathion 1 — 550.0 —

do. do. do. Methyl parathion 1 — 5,200.0 —

do. do. do. Trifluralin 1 — 32.0 —

do. Notropis atherinoides Emerald shiner Atrazine 1 — 15,600.0 —

do. do. do. Propanil 1 — 7,500.0 —

do. Oncorhynchus clarki Cutthroat trout 2,4-D 2 24,500.0 44,250.0 64,000.0

do. do. do. Carbaryl 9 970.0 3,950.0 7,100.0

do. do. do. Chlorpyrifos 2 5.4 11.7 18.0

do. do. do. Diazinon 4 1,700.0 2,230.0 3,850.0

do. do. do. Dieldrin 3 6.0 6.4 12.0

do. do. do. Dinoseb 13 41.0 87.0 1,350.0

do. do. do. Diuron 3 710.0 1,400.0 1,400.0

do. do. do. EPTC 3 12,500.0 17,000.0 23,300.0

do. do. do. Ethyl parathion 2 1,560.0 1,560.0 1,560.0

do. do. do. Malathion 4 150.0 240.5 1,740.0

do. do. do. Methomyl 2 4,050.0 5,425.0 6,800.0

Endpoint Taxa Species Name Compound N Minimum

(ppb)

Median

(ppb)

Maximum

(ppb)
Pesticide Toxicity Index for Freshwater Aquatic Organisms

LC50 Fish Oncorhynchus clarki Cutthroat trout Methyl parathion 2 1,850.0 1,850.0 1,850.0

do. do. do. Phorate 2 6.0 36.0 66.0

do. do. do. Picloram 13 1,475.0 4,700.0 8,600.0

do. Oncorhynchus gorbuscha Pink salmon Dichlorprop (2,4-DP) 2 600.0 700.0 800.0

do. do. do. Triclopyr 2 500.0 2,900.0 5,300.0

do. Oncorhynchus keta Chum salmon Dichlorprop (2,4-DP) 1 — 1,100.0 —

do. do. do. Triclopyr 2 300.0 3,900.0 7,500.0

do. Oncorhynchus kisutch Coho salmon 2-(2,4,5-Trichlorophenoxy) 

propionic acid

1 — 600.0 —

do. do. do. Dichlorprop (2,4-DP) 3 1,500.0 1,800.0 2,200.0

do. do. do. Azinphos-methyl 4 4.2 6.1 17.0

do. do. do. Carbaryl 5 764.0 1,300.0 4,340.0

do. do. do. Carbofuran 2 530.0 530.0 530.0

do. do. do. Dieldrin 1 — 10.8 —

do. do. do. Lindane 4 23.0 32.0 50.0

do. do. do. Malathion 4 101.0 170.0 265.0

do. do. do. Methyl parathion 3 5,300.0 5,300.0 5,300.0

do. do. do. Permethrin 1 — 17.0 —

do. do. do. Triclopyr 6 260.0 1,150.0 9,600.0

do. Oncorhynchus mykiss Rainbow trout 2,4,5-T 2 150.0 4,425.0 8,700.0

do. do. do. 2,4-D 8 1,400.0 27,300.0 358,000.0

do. do. do. 2,4-DB 4 2,000.0 3,700.0 14,300.0

do. do. do. 2,6-Dinitro-2-methylphenol 1 — 66.0 —

do. do. do. 2-(2,4,5-Trichlorophenoxy) 

propionic acid

2 14,800.0 16,000.0 17,200.0

do. do. do. Dichlorprop (2,4-DP) 3 900.0 1,400.0 1,800.0

do. do. do. do. 4 500.0 3,960.0 6,100.0

do. do. do. p,p'-DDE 1 — 32.0 —

do. do. do. Acetochlor 3 380.0 420.0 1,200.0

do. do. do. Alachlor 10 240.0 2,100.0 4,200.0

do. do. do. Aldicarb 3 560.0 560.0 560.0

do. do. do. Aldicarb sulfone 1 — 42,000.0 —

Endpoint Taxa Species Name Compound N Minimum

(ppb)

Median

(ppb)

Maximum

(ppb)
Tables 33

LC50 Fish Oncorhynchus mykiss Rainbow trout Atrazine 6 4,500.0 11,750.0 24,000.0

do. do. do. Azinphos-methyl 10 3.2 7.0 28.0

do. do. do. Benfluralin 2 81.0 184.5 288.0

do. do. do. Bromacil 2 36,000.0 50,500.0 65,000.0

do. do. do. Bromoxynil 2 2,090.0 10,045.0 18,000.0

do. do. do. Butylate 6 2,100.0 4,700.0 202,500.0

do. do. do. Carbaryl 25 800.0 1,470.0 5,400.0

do. do. do. Carbofuran 4 362.0 380.0 420.0

do. do. do. Chlorothalonil 14 7.6 17.6 250.0

do. do. do. Chlorpyrifos 9 7.1 8.0 51.0

do. do. do. Cyanazine 2 9,000.0 9,000.0 9,000.0

do. do. do. DCPA (Dacthal) 2 6,600.0 18,300.0 30,000.0

do. do. do. Diazinon 11 90.0 400.0 3,200.0

do. do. do. Dicamba 5 28,000.0 130,000.0 153,000.0

do. do. do. Dichlobenil 3 4,930.0 6,300.0 18,000.0

do. do. do. Dieldrin 10 0.6 2.7 10,000.0

do. do. do. Disulfoton 6 1,850.0 3,010.0 13,900.0

do. do. do. Diuron 6 1,950.0 16,000.0 23,800.0

do. do. do. EPTC 3 19,960.0 20,720.0 21,840.0

do. do. do. Ethalfluralin 2 37.0 86.5 136.0

do. do. do. Ethoprop 5 1,100.0 7,800.0 13,800.0

do. do. do. Ethyl parathion 6 750.0 1,415.0 10,000.0

do. do. do. Fenuron 1 — 204,000.0 —

do. do. do. Fluometuron 10 2,960.0 25,200.0 47,000.0

do. do. do. Fonofos 5 19.0 20.0 2,800.0

do. do. do. Lindane 11 18.0 30.0 120.0

do. do. do. Linuron 2 3,000.0 9,700.0 16,400.0

do. do. do. MCPA 2 91,000.0 91,000.0 91,000.0

do. do. do. Malathion 17 2.8 122.0 234.0

do. do. do. Methiocarb 7 0.8 800.0 4,700.0

do. do. do. Methomyl 19 860.0 1,600.0 32,000.0

do. do. do. Methyl parathion 8 2,200.0 3,700.0 161,000.0

Endpoint Taxa Species Name Compound N Minimum

(ppb)

Median

(ppb)

Maximum

(ppb)
Pesticide Toxicity Index for Freshwater Aquatic Organisms

LC50 Fish Oncorhynchus mykiss Rainbow trout Metolachlor 1 — 3,900.0 —

do. do. do. Metribuzin 5 42,000.0 76,770.0 147,000.0

do. do. do. Molinate 10 200.0 11,150.0 20,000.0

do. do. do. Napropamide 3 9,400.0 10,100.0 13,400.0

do. do. do. Norflurazon 1 — 8,100.0 —

do. do. do. Oryzalin 2 3,260.0 3,355.0 3,450.0

do. do. do. Oxamyl 4 3,700.0 4,450.0 12,400.0

do. do. do. Pebulate 1 — 7,400.0 —

do. do. do. Pendimethalin 4 138.0 760.0 86,600.0

do. do. do. Permethrin 7 2.1 5.6 72.0

do. do. do. Phorate 4 13.0 16.0 45.0

do. do. do. Picloram 11 4,000.0 19,300.0 310,000.0

do. do. do. Prometon 5 12,000.0 16,000.0 20,000.0

do. do. do. Pronamide 1 — 72,000.0 —

do. do. do. Propachlor 2 170.0 295.0 420.0

do. do. do. Propanil 2 2,300.0 7,550.0 12,800.0

do. do. do. Propargite 3 118.0 143.0 455.0

do. do. do. Propham 1 — 38,000.0 —

do. do. do. Propoxur 6 3,700.0 8,200.0 92,000.0

do. do. do. Simazine 5 40,500.0 56,000.0 70,500.0

do. do. do. Tebuthiuron 1 — 143,000.0 —

do. do. do. Terbacil 3 46,200.0 54,000.0 79,000.0

do. do. do. Terbufos 7 7.6 10.2 68.0

do. do. do. Thiobencarb 6 790.0 1,175.0 1,500.0

do. do. do. Triallate 2 1,200.0 1,350.0 1,500.0

do. do. do. Triclopyr 3 1,100.0 2,200.0 7,500.0

do. do. do. Trifluralin 8 10.0 41.5 210.0

do. Oncorhynchus nerka Sockeye salmon Dichlorprop (2,4-DP) 1 — 700.0 —

do. do. do. Triclopyr 4 400.0 1,300.0 7,500.0

do. Oncorhynchus tshawytscha Chinook salmon 2,4-D 1 — 4,800.0 —

do. do. do. Dichlorprop (2,4-DP) 1 — 600.0 —

do. do. do. Azinphos-methyl 1 — 4.3 —

Endpoint Taxa Species Name Compound N Minimum

(ppb)

Median

(ppb)

Maximum

(ppb)
Tables 35

LC50 Fish Oncorhynchus tshawytscha Chinook salmon Carbaryl 2 2,400.0 2,400.0 2,400.0

do. do. do. Dieldrin 1 — 6.1 —

do. do. do. Lindane 1 — 42.0 —

do. do. do. Malathion 2 23.0 71.5 120.0

do. do. do. Molinate 2 13,000.0 13,000.0 13,000.0

do. do. do. Thiobencarb 1 — 760.0 —

do. do. do. Triclopyr 2 1,100.0 5,400.0 9,700.0

do. Perca flavescens Yellow perch Atrazine 1 — 50,000.0 —

do. do. do. Azinphos-methyl 5 2.4 13.0 40.0

do. do. do. Carbaryl 3 350.0 745.0 5,100.0

do. do. do. Carbofuran 3 120.0 147.0 147.0

do. do. do. Fluometuron 1 — 70,000.0 —

do. do. do. Lindane 4 23.0 68.0 68.0

do. do. do. Malathion 3 263.0 263.0 263.0

do. do. do. Methyl parathion 3 3,060.0 3,060.0 3,060.0

do. do. do. Simazine 1 — 90.0 —

do. Pimephales notatus Bluntnose minnow do. 1 — 66,000.0 —

do. Pimephales promelas Fathead minnow 2,4-D 6 2,400.0 70,700.0 320,000.0

do. do. do. 2,4-DB 2 18,000.0 18,000.0 18,000.0

do. do. do. 2,6-Dinitro-2-methylphenol 5 1,540.0 1,950.0 2,720.0

do. do. do. 2-(2,4,5-Trichlorophenoxy) 

propionic acid

2 13,000.0 43,000.0 73,000.0

do. do. do. Alachlor 3 5,000.0 5,000.0 5,000.0

do. do. do. Aldicarb 4 861.0 1,285.0 1,370.0

do. do. do. Atrazine 2 15,000.0 15,000.0 15,000.0

do. do. do. Azinphos-methyl 18 37.0 202.5 1,900.0

do. do. do. Bromacil 1 — 186,000.0 —

do. do. do. Bromoxynil 3 11,500.0 13,800.0 13,800.0

do. do. do. Carbaryl 15 5,010.0 9,470.0 41,000.0

do. do. do. Carbofuran 5 844.0 872.0 1,990.0

do. do. do. Chlorpyrifos 12 120.0 155.0 542.0

do. do. do. Cyanazine 6 16,300.0 17,500.0 21,300.0

Endpoint Taxa Species Name Compound N Minimum

(ppb)

Median

(ppb)

Maximum

(ppb)
Pesticide Toxicity Index for Freshwater Aquatic Organisms

LC50 Fish Pimephales promelas Fathead minnow Diazinon 11 3,700.0 6,800.0 10,300.0

do. do. do. Dichlobenil 2 6,000.0 6,000.0 6,000.0

do. do. do. Dieldrin 9 3.8 24.0 47.0

do. do. do. Dinoseb 12 88.0 155.0 700.0

do. do. do. Disulfoton 9 1,870.0 3,980.0 4,300.0

do. do. do. Diuron 2 14,200.0 14,200.0 14,200.0

do. do. do. Ethyl parathion 14 500.0 1,505.0 3,600.0

do. do. do. Fonofos 1 — 1,090.0 —

do. do. do. Lindane 8 56.0 82.0 130.0

do. do. do. MCPB 1 — 12,500.0 —

do. do. do. Malathion 10 8,650.0 11,650.0 25,000.0

do. do. do. Methomyl 10 1,500.0 1,800.0 2,800.0

do. do. do. Methyl parathion 13 4,460.0 8,170.0 9,500.0

do. do. do. Metolachlor 2 8,000.0 8,200.0 8,400.0

do. do. do. Molinate 1 — 27,000.0 —

do. do. do. Oxamyl 2 5,480.0 6,890.0 8,300.0

do. do. do. Permethrin 2 3.0 4.4 5.7

do. do. do. Phorate 1 — 250.0 —

do. do. do. Picloram 2 55,300.0 68,400.0 81,500.0

do. do. do. Propoxur 3 8,800.0 25,000.0 25,000.0

do. do. do. Simazine 3 5,000.0 6,400.0 510,000.0

do. do. do. Terbufos 3 13.3 150.0 390.0

do. do. do. Trifluralin 2 105.0 105.0 105.0

do. Poecilia reticulata Guppy 2,4,5-T 1 — 28,100.0 —

do. do. do. 2,4-D 2 8,356.0 39,528.0 70,700.0

do. do. do. Atrazine 1 — 4,300.0 —

do. do. do. Azinphos-methyl 2 120.0 375.0 630.0

do. do. do. Carbaryl 5 3,840.0 4,700.0 9,740.0

do. do. do. Diazinon 4 800.0 3,000.0 3,400.0

do. do. do. Dieldrin 14 1.0 6.8 300.0

do. do. do. Disulfoton 2 280.0 280.0 280.0

do. do. do. Ethyl parathion 1 — 56.0 —

Endpoint Taxa Species Name Compound N Minimum

(ppb)

Median

(ppb)

Maximum

(ppb)
Tables 37

LC50 Fish Poecilia reticulata Guppy Fluometuron 1 — 46,000.0 —

do. do. do. Lindane 4 16.0 95.0 360.0

do. do. do. Malathion 3 840.0 1,200.0 3,100.0

do. do. do. Methyl parathion 2 6,200.0 8,000.0 9,800.0

do. do. do. Metolachlor 1 — 8,600.0 —

do. do. do. Prometon 2 12,000.0 12,000.0 12,000.0

do. do. do. Pronamide 1 — 150,000.0 —

do. do. do. Propoxur 3 1,400.0 1,740.0 2,980.0

do. do. do. Simazine 2 49,000.0 49,000.0 49,000.0

do. do. do. α-HCH 1 — 1,490.0 —

do. Pomoxis nigromaculatus Black crappie Azinphos-methyl 2 3.0 3.0 3.0

do. do. do. Carbaryl 2 2,600.0 2,600.0 2,600.0

do. Ptychocheilus lucius Colorado squawfish do. 2 1,310.0 2,245.0 3,180.0

do. do. do. Malathion 1 — 9,140.0 —

do. Pungitius pungitius Ninespine stickleback Chlorpyrifos 1 — 4.7 —

do. Salmo salar Atlantic salmon p,p'-DDE 1 — 96.0 —

do. do. do. Azinphos-methyl 4 1.8 2.1 2.5

do. do. do. Carbaryl 2 250.0 2,375.0 4,500.0

do. do. do. Methomyl 6 560.0 1,200.0 1,400.0

do. do. do. Permethrin 1 — 1.5 —

do. Salmo trutta Brown Trout Carbaryl 1 — 700.0 —

do. do. do. Propoxur 1 — 2,110.0 —

do. do. do. Azinphos-methyl 3 3.5 4.0 4.6

do. do. do. Carbaryl 3 1,950.0 6,300.0 6,300.0

do. do. do. Carbofuran 3 280.0 560.0 560.0

do. do. do. Diazinon 1 — 602.0 —

do. do. do. Lindane 4 1.7 1.9 22.0

do. do. do. Malathion 3 101.0 101.0 200.0

do. do. do. Methyl parathion 3 4,700.0 4,700.0 4,740.0

do. do. do. Terbufos 1 — 20.0 —

do. Salmonidae Trout family 2,4,5-T 1 — 9,400.0 —

do. do. do. Diazinon 1 — 8,000.0 —

Endpoint Taxa Species Name Compound N Minimum

(ppb)

Median

(ppb)

Maximum

(ppb)
Pesticide Toxicity Index for Freshwater Aquatic Organisms

LC50 Fish Salmonidae Trout family Diuron 1 — 1,100.0 —

do. do. do. MCPA 1 — 25,000.0 —

do. Salvelinus fontinalis Brook trout Atrazine 3 4,900.0 4,900.0 6,300.0

do. do. do. Azinphos-methyl 1 — 1.2 —

do. do. do. Carbaryl 13 900.0 2,500.0 5,400.0

do. do. do. Diazinon 4 450.0 785.0 1,050.0

do. do. do. Ethyl parathion 2 1,510.0 1,755.0 2,000.0

do. do. do. Lindane 1 — 44.3 —

do. do. do. Malathion 2 120.0 125.0 130.0

do. do. do. Methomyl 5 1,200.0 1,500.0 2,200.0

do. do. do. Permethrin 4 2.3 3.6 5.2

do. do. do. Propoxur 1 — 3,550.0 —

do. Salvelinus namaycush Lake trout 2,4-D 2 44,500.0 44,750.0 45,000.0

do. do. do. Carbaryl 2 690.0 690.0 690.0

do. do. do. Carbofuran 2 164.0 164.0 164.0

do. do. do. Chlorpyrifos 2 73.0 85.5 98.0

do. do. do. Diazinon 2 600.0 601.0 602.0

do. do. do. Dinoseb 11 32.0 79.0 1,400.0

do. do. do. Diuron 3 1,200.0 2,700.0 2,700.0

do. do. do. EPTC 2 11,500.0 13,850.0 16,200.0

do. do. do. Ethyl parathion 2 1,920.0 1,920.0 1,920.0

do. do. do. Lindane 3 24.0 32.0 32.0

do. do. do. Malathion 2 76.0 76.0 76.0

do. do. do. Methyl parathion 2 3,780.0 3,780.0 3,780.0

do. do. do. Picloram 11 1,550.0 2,350.0 4,950.0

do. Sciaenops ocellatus Red drum Azinphos-methyl 2 6.2 6.7 7.1

do. Stizostedion vitreum v. Walleye Malathion 2 64.0 64.0 64.0

do. do. do. Phorate 1 — 57.0 —

do. Tilapia mossambica Mozambique tilapia Carbaryl 1 — 8,500.0 —

do. do. do. Carbofuran 3 460.0 480.0 540.0

do. do. do. Chlorothalonil 1 — 120.0 —

do. do. do. Dieldrin 2 8.4 9.2 10.0

Endpoint Taxa Species Name Compound N Minimum

(ppb)

Median

(ppb)

Maximum

(ppb)
Tables 39

LC50 Fish Tilapia mossambica Mozambique tilapia Lindane 4 57.0 1,889.0 4,000.0

do. do. do. Malathion 5 140.0 500.0 2,000.0

do. do. do. Propoxur 2 7,800.0 7,900.0 8,000.0

do. Tinca tinca Tench 2,4,5-T 1 — 8,300.0 —

do. do. do. Diuron 1 — 15,500.0 —

do. do. do. MCPA 1 — 45,000.0 —

do. do. do. Propoxur 4 3,700.0 8,650.0 13,300.0

do. Umbra pygmaea Eastern mudminnow Malathion 1 — 240.0 —

Insecta Acroneuria ruralis Stonefly Diazinon 1 — 16.0 —

do. Acroneuria sp. do. Atrazine 1 — 6,700.0 —

do. Arctopsyche grandis Caddisfly Ethyl parathion 2 7.0 7.0 7.0

do. do. do. Malathion 2 32.0 32.0 32.0

do. Atherix variegata Snipefly do. 2 385.0 385.0 385.0

do. Baetis intermedius Mayfly Diazinon 1 — 24.0 —

do. Brachythemis contaminata Dragonfly Carbaryl 1 — 6,933.0 —

do. do. do. Carbofuran 1 — 0.1 —

do. Chaoborus flavicans Midge Lindane 1 — 4.0 —

do. do. do. Chlorpyrifos 1 — 6.6 —

do. Chaoborus sp. Phantom midge Lindane 1 — 3.3 —

do. Chironomus plumosus Midge Lindane 3 12.7 13.5 51.2

do. do. do. Methomyl 1 — 32.0 —

do. Chironomus riparius do. Lindane 5 1.6 6.9 235.0

do. Chironomus tentans do. Azinphos-methyl 1 — 0.4 —

do. do. do. Chlorpyrifos 1 — 0.5 —

do. do. do. Diazinon 2 0.0 5.4 10.7

do. do. do. Ethyl parathion 1 — 31.0 —

do. Claassenia sabulosa Stonefly Carbaryl 3 5.6 5.6 5.6

do. do. do. Chlorpyrifos 3 0.6 0.6 0.6

do. do. do. Dieldrin 2 0.6 0.6 0.6

do. do. do. Ethyl parathion 3 1.5 1.5 1.5

do. do. do. Malathion 4 2.8 2.8 56.0

do. Cloeon dipterum Mayfly Chlorpyrifos 1 — 0.3 —

Endpoint Taxa Species Name Compound N Minimum

(ppb)

Median

(ppb)

Maximum

(ppb)
Pesticide Toxicity Index for Freshwater Aquatic Organisms

LC50 Insecta Cloeon sp. Mayfly Lindane 1 — 50.0 —

do. Corixa punctata Water boatman Chlorpyrifos 2 1.9 2.0 2.0

do. Drunella grandis Mayfly Azinphos-methyl 1 — 14.0 —

do. do. do. Dieldrin 1 — 8.0 —

do. do. do. Disulfoton 1 — 78.0 —

do. do. do. Ethyl parathion 1 — 3.0 —

do. do. do. Malathion 1 — 100.0 —

do. Hesperoperla pacifica Golden stonefly Azinphos-methyl 2 8.5 8.5 8.5

do. do. do. Dieldrin 2 24.0 24.0 24.0

do. do. do. Disulfoton 3 8.2 8.2 9.4

do. do. do. Ethyl parathion 4 1.0 2.8 3.0

do. do. do. Malathion 4 7.0 7.1 7.7

do. Hexagenia bilineata Mayfly Ethyl parathion 2 15.0 15.0 15.0

do. do. do. Permethrin 1 — 0.1 —

do. Hexagenia sp. do. Phorate 1 — 65.0 —

do. Hydropsyche angustipennis Caddisfly Lindane 1 — 330.0 —

do. do. do. Ethyl parathion 2 0.4 0.4 0.4

do. do. do. Malathion 2 22.5 22.5 22.5

do. Hydropsyche sp. do. do. 2 5.0 5.0 5.0

do. do. do. Methiocarb 1 — 14.0 —

do. Ischnura sp. Damselfly Methyl parathion 1 — 33.0 —

do. Ischnura verticalis do. Dieldrin 1 — 12.0 —

do. do. do. Ethyl parathion 2 0.6 0.6 0.6

do. do. do. Methyl parathion 1 — 33.0 —

do. Isogenus sp. Stonefly Carbaryl 1 — 3.6 —

do. do. do. Methomyl 2 29.0 186.0 343.0

do. Isonychia sp. Mayfly Methiocarb 1 — 7.0 —

do. Isoperla sp. Stonefly Malathion 2 0.7 0.7 0.7

do. Leptoceridae Longhorn caddisfly Chlorpyrifos 1 — 0.8 —

do. Lestes congener Damselfly Diazinon 1 — 50.0 —

do. do. do. Dieldrin 1 — 3.0 —

do. do. do. Ethyl parathion 1 — 3.0 —

Endpoint Taxa Species Name Compound N Minimum

(ppb)

Median

(ppb)

Maximum

(ppb)
Tables 41

LC50 Insecta Lestes congener Damselfly Lindane 1 — 20.0 —

do. do. do. Malathion 2 10.0 10.0 10.0

do. do. do. Propoxur 1 — 300.0 —

do. Limnephilus bipunctatus Caddisfly Ethyl parathion 1 — 37.9 —

do. do. do. do. 1 — 2.4 —

do. do. do. Lindane 1 — 9.6 —

do. Limnephilus sp. do. Malathion 2 1.3 1.3 1.3

do. Neoplea striola Pygmy backswimmer Chlorpyrifos 2 1.2 1.4 1.6

do. Notonecta undulata Backswimmer Carbaryl 1 — 200.0 —

do. do. do. Dieldrin 1 — 1.0 —

do. do. do. Ethyl parathion 1 — 7.0 —

do. do. do. Lindane 1 — 3.0 —

do. do. do. Malathion 1 — 80.0 —

do. do. do. Propoxur 1 — 160.0 —

do. Ophiogomphus sp Dragonfly Carbofuran 1 — 220.0 —

do. Paraleptophlebia pallipes Mayfly Diazinon 1 — 44.0 —

do. Peltodytes sp Beetle Carbaryl 1 — 3,300.0 —

do. do. do. Chlorpyrifos 1 — 0.8 —

do. do. do. Dieldrin 1 — 2.0 —

do. do. do. Ethyl parathion 1 — 7.0 —

do. do. do. Lindane 1 — 20.0 —

do. do. do. Malathion 1 — 1,000.0 —

do. do. do. Propoxur 1 — 8,000.0 —

do. Pteronarcella badia Stonefly Carbaryl 6 1.7 6.4 29.0

do. do. do. Chlorpyrifos 1 — 0.4 —

do. do. do. Dieldrin 2 0.5 0.5 0.5

do. do. do. Ethyl parathion 3 4.2 4.2 4.2

do. do. do. Malathion 3 1.1 1.1 1.1

do. do. do. Methomyl 3 60.0 60.0 69.0

do. Pteronarcys californica do. 2,4-D 2 1,600.0 8,300.0 15,000.0

do. do. do. 2,4-DB 2 15,000.0 15,000.0 15,000.0

do. do. do. 2,6-Dinitro-2-methylphenol 2 320.0 320.0 320.0

Endpoint Taxa Species Name Compound N Minimum

(ppb)

Median

(ppb)

Maximum

(ppb)
Pesticide Toxicity Index for Freshwater Aquatic Organisms

LC50 Insecta Pteronarcys californica Stonefly 2-(2,4,5-Trichlorophenoxy) 

propionic acid

1 — 340.0 —

do. do. do. Azinphos-methyl 5 1.5 1.9 22.0

do. do. do. Carbaryl 4 2.0 4.8 4.8

do. do. do. Chlorpyrifos 3 10.0 10.0 10.0

do. do. do. Diazinon 3 25.0 25.0 25.0

do. do. do. Dichlobenil 4 6,600.0 7,000.0 7,000.0

do. do. do. Dieldrin 4 0.5 19.8 39.0

do. do. do. Disulfoton 6 5.0 14.5 28.5

do. do. do. Diuron 2 1,200.0 1,200.0 1,200.0

do. do. do. Ethyl parathion 8 5.1 18.7 100.0

do. do. do. Lindane 5 1.0 4.5 4.5

do. do. do. Malathion 5 10.0 50.0 100.0

do. do. do. Methiocarb 4 5.0 5.4 5.4

do. do. do. Molinate 3 340.0 340.0 370.0

do. do. do. Phorate 1 — 4.0 —

do. do. do. Picloram 2 48.0 24,024.0 48,000.0

do. do. do. Propoxur 3 13.0 18.0 18.0

do. do. do. Simazine 1 — 1,900.0 —

do. do. do. Trifluralin 4 2,800.0 2,900.0 3,000.0

do. Pteronarcys sp. do. 2,4-DB 1 — 15,000.0 —

do. do. do. Diazinon 1 — 25.0 —

do. do. do. Diuron 1 — 1,200.0 —

do. Ranatra elongata Water scorpion Carbaryl 1 — 624.0 —

do. Sigara striata Water bug Lindane 1 — 3.9 —

do. Skwala sp. Stonefly Carbaryl 2 3.6 6.4 9.2

do. do. do. Methomyl 3 29.0 29.0 34.0

Invert Eudiaptomus gracilis Calanoid copepod 2,4-D 1 — 144,100.0 —

do. Eurytemora affinis do. Atrazine 3 500.0 2,600.0 13,200.0

do. do. do. Methomyl 1 — 290.0 —

Mollusca Corbicula fluminea Asiatic clam Methiocarb 1 — 8,800.0 —

do. Corbicula manilensis do. do. 1 — 8,800.0 —

Endpoint Taxa Species Name Compound N Minimum

(ppb)

Median

(ppb)

Maximum

(ppb)
Tables 43

LC50 Mollusca Lamellidens corrianus Bivalve Malathion 4 118.6 184.5 284.1

do. do. Pond snail Aldicarb 1 — 11,500.0 —

do. do. do. Carbaryl 2 4,400.0 4,450.0 4,500.0

do. do. do. Carbofuran 1 — 3,097.0 —

do. do. do. Lindane 1 — 2,685.0 —

do. do. do. Phorate 2 15,000.0 18,500.0 22,000.0

do. Anodonta anatina Fresh-water mussel Malathion 1 — 80.0 —

do. Egeria radiata Freshwater Clam Lindane 1 — 145,000.0 —

do. Lymnaea stagnalis Great pond snail Lindane 1 — 3,300.0 —

Nematoda Monhystera disjuncta Nematode Lindane 1 — 6,700.0 —

Oligochaeta Limnodrilus hoffmeisteri Oligochaeta Carbofuran 1 — 5,294.0 —

do. do. do. Lindane 1 — 6,233.0 —

do. Tubifex tubifex do. Carbaryl 1 — 50.0 —

do. do. do. Lindane 2 3,500.0 3,700.0 3,900.0

do. do. do. Methyl parathion 1 — 500.0 —

Turbellaria Dugesia tigrina Turbellaria Diazinon 1 — 630.0 —

do. do. do. Malathion 1 — 4,400.0 —

do. do. do. Methyl parathion 2 2,600.0 3,350.0 4,100.0

do. Polycelis felina do. p,p'-DDE 1 — 1,050.0 —

Endpoint Taxa Species Name Compound N Minimum

(ppb)

Median

(ppb)

Maximum

(ppb)
44 Pesticide Toxicity Index for Freshwater Aquatic Organisms

Endpoint Taxa Species Common name Bioassays Comp

Cladocerans

EC50 Crustacea Ceriodaphnia dubia Water flea 2 2

do. Chydorus ovalis do. 1 1

do. Daphnia carinata do. 4 4

do. Daphnia laevis do. 6 3

do. Daphnia magna do. 200 58

do. Daphnia pulex do. 37 16

do. Moina australiensis do. 1 1

do. Simocephalus serrulatus do. 33 12

do. Simocephalus sp. do. 2 2

do. Simocephalus vetulus do. 1 1

287 61

Benthic invertebrates

LC50 Crustacea Acartia tonsa Calanoid copepod 3 3

do. Artemia salina Brine shrimp 3 2

do. Asellus aquaticus Aquatic sowbug 1 1

do. Asellus brevicaudus do. 23 10

do. Asellus communis do. 1 1

do. Caridina rajadhari Freshwater prawn 2 2

do. Cyclops strenuus Copepod 1 1

do. Cypridopsis vidua Seed shrimp 1 1

do. Eudiaptomus gracilis Calanoid copepod 1 1

do. Eurytemora affinis do. 4 2

do. Gammarus fasciatus Scud 76 28

do. Gammarus fossarum do. 1 1

do. Gammarus italicus do. 12 12

do. Gammarus lacustris do. 45 18

do. Gammarus pseudolimnaeus do. 21 9

do. Gammarus pulex do. 13 6

do. Hyalella azteca do. 5 4

do. Macrobrachium dayanum Freshwater prawn 1 1

do. Macrobrachium rosenbergii Giant river prawn 2 1

do. Neomysis mercedis Opposum Shrimp 10 3

do. Orconectes immunis Crayfish 2 2

do. Orconectes nais do. 16 7

do. Palaemonetes kadiakensis Glass shrimp 25 15

do. Palaemonetes pugio Daggerblade grass shrimp 12 8

do. Palaemonetes sp. Grass shrimp 12 1

do. Palaemonetes vulgaris Marsh grass shrimp 5 5

do. Procambarus acutus acutus White river crayfish 9 9

do. Procambarus blandingii Crayfish 1 1

do. Procambarus clarkii Red swamp crayfish 13 8

do. Procambarus simulans Crayfish 2 2

do. Procambarus sp. do. 6 4

Table 3. Summary of taxa included in bioassay data set and number of bioassays and compounds

[do., ditto; EC50, concentration at which 50 percent of test organisms exhibited nonlethal responses; LC50, concentration at w

50 percent mortality occurred; sp., species]
 Tables 

Benthic invertebrates—Continued

LC50 Insecta Acroneuria ruralis Stonefly 1 1

do. Acroneuria sp. do. 1 1

do. Arctopsyche grandis Caddisfly 4 2

do. Atherix variegata Snipefly 2 1

do. Baetis intermedius Mayfly 1 1

do. Brachythermis contaminata Dragonfly 2 2

do. Chaoborus flavicans Midge 1 1

do. Chaoborus obscuripes do. 1 1

do. Chaoborus sp. Phantom midge 1 1

do. Chironomus plumosus Midge 4 2

do. Chironomus riparius do. 5 1

do. Chironomus tentans do. 5 4

do. Claassenia sabulosa Stonefly 15 5

do. Cloeon dipterum Mayfly 1 1

do. Cloeon sp. do. 1 1

do. Corixa punctata Water boatman 2 1

do. Drunella grandis Mayfly 5 5

do. Hesperoperla pacifica Golden stonefly 15 5

do. Hexagenia bilineata Mayfly 3 2

do. Hexagenia sp. do. 1 1

do. Hydropsyche angustipennis Caddisfly 1 1

do. Hydropsyche californica do. 4 2

do. Hydropsyche sp. do. 3 2

do. Ischnura sp. Damselfly 1 1

do. Ischnura verticalis do. 4 3

do. Isogenus sp. Stonefly 3 2

do. Isonychia sp. Mayfly 1 1

do. Isoperla sp. Stonefly 2 2

do. Leptoceridae Longhorn caddisfly family 1 1

do. Lestes congener Damselfly 7 6

do. Limnephilus sp. Caddisfly 2 1

do. Limnephilus bipunctatus do. 1 1

do. Limnephilus lunatus do. 2 2

do. Neoplea striola Pygmy backswimmer 2 1

do. Notonecta undulata Backswimmer 6 6

do. Ophiogomphus sp. Dragonfly 1 1

do. Paraleptophlebia pallipes Mayfly 1 1

do. Peltodytes sp. Beetle 7 7

do. Pteronarcella badia Stonefly 18 6

do. Pteronarcys californica do. 74 22

do. Pteronarcys sp. do. 3 3

do. Ranatra elongata Water scorpion 1 1

do. Sigara striata Water bug 1 1

do. Skwala sp. Stonefly 5 2

Mollusca Anodonta anatina Freshwater mussel 1 1

do. Corbicula fluminea Asiatic clam 1 1

do. Corbicula manilensis do. 1 1

do. Egeria radiata Freshwater clam 1 1

Endpoint Taxa Species Common name Bioassays Comp

Table 3. Summary of taxa included in bioassay data set and number of bioassays and compounds—Continued
46 Pesticide Toxicity Index for Freshwater Aquatic Organisms

Benthic invertebrates—Continued

LC50 Mollusca Lamellidens corrianus Bivalve 4 1

do. Lymnaea acuminata Pond snail 7 5

do. Lymnaea stagnalis Great pond snail 1 1

Nematode Monhystera disjuncta Nematode 1 1

Oligochaeta Branchiura sowerbyi Oligochaete 1 1

do. Limnodrilus hoffmeisteri Oligochaeta 2 2

do. Lumbriculus variegatus do. 2 2

do. Tubifex tubifex do. 4 3

do. Tubificidae do. 3 3

Turbellaria Dugesia tigrina Turbellaria 4 3

do. Polycelis felina do. 1 1

585 46

Fish

Fish Ameiurus melas Black bullhead 20 10

do. Ameiurus natalis Yellow bullhead 1 1

do. Ameiurus nebulosus Brown bullhead 1 1

do. Ameiurus sp. Bullhead catfish 7 5

do. Anguilla anguilla European eel 18 4

do. Anguilla rostrata American eel 8 6

do. Carassius auratus Goldfish 50 22

do. Centrarchidae Sunfish family 5 1

do. Clarias batrachus Walking catfish 10 6

do. Coregonus lavaretus Whitefish 2 1

do. Ctenopharyngodon idella Grass carp 2 2

do. Cyprinella lutrensis Red shiner 2 2

do. Cyprinodon variegatus Sheepshead minnow 74 37

do. Cyprinus carpio Carp 79 24

do. Esox lucius Northern pike 4 2

do. Fundulus diaphanus Banded killifish 4 4

do. Fundulus heteroclitus Mummichog 19 6

do. Gambusia affinis Western mosquitofish 28 18

do. Gambusia sp. do. 1 1

do. Gasterosteus aculeatus Threespine stickleback 12 7

do. Gila elegans Bonytail 4 2

do. Ictalurus punctatus Channel catfish 102 34

do. Jordanella floridae Flagfish 5 3

do. Lagodon rhomboides Pinfish 1 1

do. Leiostomus xanthurus Spot 1 1

do. Lepomis cyanellus Green sunfish 19 8

do. Lepomis gibbosus Pumpkinseed 5 5

do. Lepomis macrochirus Bluegill 399 65

do. Lepomis microlophus Red ear sunfish 8 6

do. Leuciscus idus Ide 3 2

do. Menidia beryllina Inland silverside 8 5

do. Micropterus dolomieui Smallmouth bass 1 1

do. Micropterus salmoides Largemouth bass 32 13

do. Morone americana White perch 4 4

Endpoint Taxa Species Common name Bioassays Comp

Table 3. Summary of taxa included in bioassay data set and number of bioassays and compounds—Continued
 Tables 

Fish—Continued

LC50 Fish Morone saxatilis Striped bass 62 15

do. Mugil cephalus Striped mullet 6 6

do. Notropis atherinoides Emerald shiner 2 2

do. Oncorhynchus clarki Cutthroat trout 64 14

do. Oncorhynchus gorbuscha Pink salmon 4 2

do. Oncorhynchus keta Chum salmon 3 2

do. Oncorhynchus kisutch Coho salmon 34 11

do. Oncorhynchus mykiss Rainbow trout 373 73

do. Oncorhynchus nerka Sockeye salmon 5 2

do. Oncorhynchus tshawytscha Chinook salmon 14 10

do. Perca flavescens Yellow perch 24 9

do. Pimephales notatus Bluntnose minnow 1 1

do. Pimephales promelas Fathead minnow 207 37

do. Poecilia reticulata Guppy 52 19

do. Pomoxis nigromaculatus Black crappie 4 2

do. Ptychocheilus lucius Colorado squawfish 3 2

do. Pungitius pungitius Ninespine stickleback 1 1

do. Salmo salar Atlantic salmon 14 5

do. Salmo trutta Brown Trout 22 10

do. Salmonidae Trout family 4 4

do. Salvelinus fontinalis Brook trout 36 10

do. Salvelinus namaycush Lake trout 47 13

do. Sciaenops ocellatus Red drum 2 1

do. Stizostedion vitreum v. Walleye 3 2

do. Tilapia mossambica Mozambique tilapia 18 7

do. Tinca tinca Tench 7 4

do. Umbra pygmaea Eastern mudminnow 1 1

1,952 75

Endpoint Taxa Species Common name Bioassays Comp

Table 3. Summary of taxa included in bioassay data set and number of bioassays and compounds—Continued
48 Pesticide Toxicity Index for Freshwater Aquatic Organisms

Compound N Minimum (ppb) Median (ppb) Maximum (ppb

2,4-D 3 3,200.00 4,900.00 25,000.00

2,4-DB 1 — 25,000.00 —

2,6-Dinitro-2-methylphenol 2 145.00 1,422.50 2,700.00

Acetochlor 3 7,200.00 8,200.00 14,000.00

Alachlor 8 7,700.00 15,700.00 35,000.00

Aldicarb 3 51.00 65.00 410.70

Aldicarb sulfone 3 280.00 369.00 556.00

Aldicarb sulfoxide 2 43.00 50.00 57.00

Atrazine 4 6,900.00 41,500.00 115,000.00

Azinphos-methyl 4 1.10 1.55 4.40

Benfluralin 1 — 2,186.00 —

Bromacil 1 — 121,000.00 —

Bromoxynil 24 41.00 126.50 74,000.00

Butylate 2 11,900.00 85,250.00 158,600.00

Carbaryl 16 2.77 6.93 7,100.00

Carbofuran 8 2.00 39.80 86.10

Chlorothalonil 4 70.00 97.00 172.00

Chlorpyrifos 3 0.10 0.40 1.70

Cyanazine 9 35,500.00 84,000.00 106,000.00

DCPA (Dacthal) 2 27,000.00 82,500.00 138,000.00

Diazinon 17 0.50 1.22 1.80

Dicamba 2 110,700.00 430,350.00 750,000.00

Dichlobenil 6 3,700.00 5,800.00 6,200.00

Dichlorprop(2,4-DP) 2 5,400.00 5,825.00 6,250.00

Dieldrin 7 130.00 240.00 251.00

Disulfoton 1 — 13.00 —

Diuron 7 1,400.00 2,000.00 8,400.00

EPTC 3 6,400.00 7,500.00 14,150.00

Ethalfluralin 1 — 60.00 —

Ethoprop 3 43.90 93.00 690,000.00

Ethyl parathion 14 0.37 0.65 7.20

Fonofos 3 2.00 8.37 15.50

Lindane 17 100.00 656.00 8,000.00

Linuron 4 120.00 240.00 1,100.00

Malathion 15 0.59 1.80 100.00

Methiocarb 1 — 19.00 —

Methomyl 6 7.60 8.80 3,200.00

Methyl parathion 10 0.14 7.90 28.20

Metolachlor 3 23,500.00 25,100.00 26,000.00

Metribuzin 3 4,180.00 4,200.00 98,500.00

Molinate 4 2,400.00 12,050.00 24,000.00

Napropamide 2 14,300.00 19,500.00 24,700.00

Oryzalin 1 — 1,500.00 —

Oxamyl 5 420.00 1,950.00 5,700.00

Pebulate 1 — 6,830.00 —

Pendimethalin 2 280.00 2,690.00 5,100.00

Table 4. Summary of EC50 median toxicity concentrations for cladocerans 

[EC50, concentration at which 50 percent of test organisms exhihbited nonlethal responses; N, number of bioassays; —, no da

ppb, part per billion] 
 Tables 

Phorate 4 18.23 21.75 37.00

Prometon 3 25,700.00 38,000.00 59,800.00

Propachlor 3 6,900.00 7,800.00 13,000.00

Propanil 3 1,200.00 6,700.00 11,400.00

Propargite 2 74.00 82.50 91.00

Propham 4 8,000.00 10,000.00 10,000.00

Propoxur 2 11.00 19.10 27.20

Simazine 2 1,100.00 1,100.00 1,100.00

Tebuthiuron 1 — 297,000.00 —

Terbacil 1 65,000.00 65,000.00 65,000.00

Terbufos 4 0.31 3.35 13.00

Thiobencarb 4 101.00 335.00 1,200.00

Triallate 2 91.00 260.50 430.00

Trifluralin 7 240.00 625.00 900.00

α-HCH 2 800.00 900.00 1,000.00

Compound N Minimum (ppb) Median (ppb) Maximum (ppb

Table 4. Summary of EC50 median toxicity concentrations for cladocerans —Continued
50 Pesticide Toxicity Index for Freshwater Aquatic Organisms

Compound N Minimum (ppb) Median (ppb) Maximum (ppb

2,4-D 4 1,600.00 8,700.00 144,100.00

2,4-DB 3 15,000.00 15,000.00 15,000.00

2,6-Dinitro-2-methylphenol 3 320.00 320.00 1,100.00

2-(2,4,5-Trichlorophenoxy) propionic acid 1 — 340.00 —

Alachlor 2 19,500.00 19,600.00 19,700.00

Aldicarb 2 420.00 5,960.00 11,500.00

Atrazine 9 94.00 9,000.00 14,900.00

Azinphos-methyl 31 0.10 1.20 56.00

Benfluralin 2 1,100.00 1,100.00 1,100.00

Butylate 4 10,000.00 11,000.00 15,000.00

Carbaryl 51 1.70 16.00 6,933.00

Carbofuran 12 0.12 16.50 5,294.00

Chlorpyrifos 31 0.04 0.57 83.00

Cyanazine 2 2,000.00 2,000.00 2,000.00

DCPA (Dacthal) 1 — 6,200.00 —

Diazinon 19 0.03 25.00 6,160.00

Dicamba 2 3,900.00 3,900.00 3,900.00

Dichlobenil 10 6,600.00 10,500.00 35,000.00

Dieldrin 30 0.50 24.00 6,710.00

Dinoseb 1 — 1,800.00 —

Disulfoton 21 3.90 27.00 27,000.00

Diuron 8 160.00 950.00 15,500.00

EPTC 6 23,000.00 23,000.00 66,000.00

Ethyl parathion 62 0.04 3.50 5,230.00

Lindane 55 1.00 12.90 145,000.00

Malathion 69 0.50 12.00 50,000.00

Methiocarb 12 5.00 62.00 8,800.00

Methomyl 22 29.00 240.00 1,050.00

Methyl parathion 14 0.20 9.40 4,100.00

Molinate 11 300.00 4,500.00 21,800.00

Oryzalin 2 190.00 295.00 400.00

Oxamyl 1 — 220.00 —

Pebulate 2 10,000.00 10,000.00 10,000.00

Permethrin 3 0.10 0.17 210.00

Phorate 14 0.60 6.50 22,000.00

Picloram 3 27.00 48.00 48,000.00

Propanil 1 — 16,000.00 —

Propargite 1 — 101.00 —

Propham 2 10,000.00 14,500.00 19,000.00

Propoxur 13 13.00 50.00 146,000.00

Simazine 3 1,900.00 13,000.00 13,000.00

Terbufos 17 0.17 5.60 12.00

Thiobencarb 8 200.00 1,000.00 9,240.00

Trifluralin 13 37.00 2,800.00 26,000.00

α-HCH 1 — 500.00 —

p,p′-DDE 1 — 1,050.00 —

Table 5. Summary of LC50 median toxicity concentrations for benthic invertebrates 

[LC50, concentration at which 50 percent mortality occurred in test organisms; N, number of bioassays; —, no data] 
 Tables 

Compound N Minimum (ppb) Median (ppb) Maximum (ppb

2,4,5-T 12 150.00 15,500.00 43,700.00

2,4-D 43 1,400.00 44,500.00 358,000.00

2,4-DB 9 2,000.00 7,500.00 18,000.00

2,6-Dinitro-2-methylphenol 8 66.00 1,720.00 2,720.00

2-(2,4,5-Trichlorophenoxy) propionic acid 11 350.00 14,000.00 86,000.00

Acetochlor 8 380.00 1,400.00 3,900.00

Alachlor 25 240.00 4,200.00 12,400.00

Aldicarb 14 41.00 560.00 7,400.00

Aldicarb sulfone 2 42,000.00 47,500.00 53,000.00

Atrazine 33 2,000.00 15,000.00 69,000.00

Azinphos-methyl 107 0.36 22.80 4,270.00

Benfluralin 7 65.00 420.00 810.00

Bentazon 2 978,000.00 2,426,000.00 3,874,000.00

Bromacil 5 36,000.00 127,000.00 186,000.00

Bromoxynil 7 2,090.00 13,800.00 23,000.00

Butylate 14 210.00 6,200.00 202,500.00

Carbaryl 165 140.00 4,330.00 290,000.00

Carbofuran 48 80.00 380.00 10,250.00

Chlorothalonil 25 7.60 51.00 430.00

Chlorpyrifos 53 0.58 38.00 806.00

Cyanazine 16 9,000.00 16,850.00 22,500.00

DCPA (Dacthal) 2 6,600.00 18,300.00 30,000.00

Diazinon 79 22.00 602.00 10,300.00

Dicamba 8 28,000.00 135,350.00 465,000.00

Dichlobenil 20 4,930.00 8,850.00 6,200,000.00

Dichlorprop (2,4-DP) 18 500.00 1,450.00 6,100.00

Dieldrin 83 0.62 10.00 10,000.00

Dinoseb 42 28.00 96.50 1,400.00

Disulfoton 35 8.20 1,850.00 13,900.00

Diuron 30 500.00 5,400.00 84,000.00

EPTC 13 11,500.00 20,720.00 26,700.00

Ethalfluralin 6 32.00 119.00 260.00

Ethoprop 13 180.00 2,070.00 13,800.00

Ethyl parathion 60 17.80 1,400.00 10,000.00

Fenuron 1 — 204,000.00 —

Fluometuron 26 600.00 36,500.00 96,000.00

Fonofos 16 5.10 20.00 2,800.00

Lindane 116 1.10 68.00 16,000.00

Linuron 8 890.00 6,100.00 16,400.00

MCPA 6 25,000.00 75,000.00 97,000.00

MCPB 2 3,300.00 7,900.00 12,500.00

Malathion 146 0.19 200.00 52,200.00

Methiocarb 12 0.75 538.00 4,700.00

Methomyl 75 300.00 1,250.00 32,000.00

Methyl parathion 81 5.00 5,360.00 161,000.00

Metolachlor 8 3,900.00 8,200.00 10,000.00

Table 6. Summary of LC50 median toxicity concentrations for freshwater fish 

[LC50, concentration at which 50 percent mortality occurred; N, number of bioassays; ppb, part per billion; —, no data] 
52 Pesticide Toxicity Index for Freshwater Aquatic Organisms

Metribuzin 10 3,400.00 80,885.00 147,000.00

Molinate 31 200.00 14,000.00 42,800.00

Napropamide 6 9,400.00 12,650.00 14,000.00

Norflurazon 3 8,100.00 9,580.00 16,300.00

Oryzalin 3 2,880.00 3,260.00 3,450.00

Oxamyl 14 2,600.00 6,415.00 27,500.00

Pebulate 3 7,400.00 7,900.00 10,000.00

Pendimethalin 12 138.00 960.00 90,400.00

Permethrin 34 0.79 6.80 88.00

Phorate 24 1.00 10.10 280.00

Picloram 55 1,400.00 8,600.00 310,000.00

Prometon 13 12,000.00 19,600.00 47,300.00

Pronamide 3 72,000.00 150,000.00 350,000.00

Propachlor 4 170.00 255.00 420.00

Propanil 6 2,300.00 6,450.00 14,000.00

Propargite 6 31.00 130.50 455.00

Propham 4 29,000.00 33,500.00 86,500.00

Propoxur 34 1,300.00 6,970.00 180,000.00

Simazine 32 90.00 56,000.00 822,000.00

Tebuthiuron 2 106,000.00 124,500.00 143,000.00

Terbacil 6 46,200.00 90,950.00 112,000.00

Terbufos 30 0.77 6.15 1,800.00

Thiobencarb 41 110.00 910.00 2,500.00

Triallate 5 1,200.00 1,330.00 2,400.00

Triclopyr 19 260.00 1,300.00 9,700.00

Trifluralin 28 8.40 95.50 12,000.00

α-HCH 1 — 1,490.00 —

p,p′-DDE 3 32.00 96.00 240.00

Compound N Minimum (ppb) Median (ppb) Maximum (ppb

Table 6. Summary of LC50 median toxicity concentrations for freshwater fish—Continued 
Tables 53

Cladocerans Benthic invertebrates Fish

Compound

Rrelative

toxicity 

(EC50)

Compound

Relative

toxicity

 (LC50)

Compound

Relative 

toxicity

(LC50)

Chlorpyrifos 1.000000 Permethrin 1.000000 Terbufos 1.000000

Ethyl parathion 0.615385 Chlorpyrifos 0.298246 Permethrin 0.904412

Diazinon 0.327869 Azinphos-methyl 0.141667 Dieldrin 0.615000

Azinphos-methyl 0.258065 Ethyl parathion 0.048571 Phorate 0.608911

Malathion 0.222222 Terbufos 0.030357 Fonofos 0.307500

Terbufos 0.119403 Phorate 0.026154 Azinphos-methyl 0.269737

Carbaryl 0.057720 Methyl parathion 0.018085 Chlorpyrifos 0.161842

Methyl parathion 0.050633 Malathion 0.014167 Chlorothalonil 0.120588

Fonofos 0.047790 Lindane 0.013178 Lindane 0.090441

Methomyl 0.045455 Carbaryl 0.010625 Trifluralin 0.064398

Disulfoton 0.030769 Carbofuran 0.010303 p,p′-DDE 0.064063

Methiocarb 0.021053 Dieldrin 0.007083 Dinoseb 0.063731

Propoxur 0.020942 Diazinon 0.006800 Ethalfluralin 0.051681

Phorate 0.018391 Disulfoton 0.006296 Propargite 0.047126

Carbofuran 0.010050 Picloram 0.003542 Malathion 0.030750

Aldicarb sulfoxide 0.008000 Propoxur 0.003400 Propachlor 0.024118

Ethalfluralin 0.006667 Methiocarb 0.002742 Carbofuran 0.016184

Aldicarb 0.006154 Propargite 0.001683 Benfluralin 0.014643

Propargite 0.004848 Oxamyl 0.000773 Methiocarb 0.011431

Ethoprop 0.004301 Methomyl 0.000708 Aldicarb 0.010982

Chlorothalonil 0.004124 Oryzalin 0.000576 Diazinon 0.010216

Bromoxynil 0.003162 2,6-Dinitro-2-methylphenol 0.000531 Thiobencarb 0.006758

Dieldrin 0.001667 2-(2,4,5-Trichlorophenoxy) propionic acid 0.000500 Pendimethalin 0.006406

Linuron 0.001667 α-HCH 0.000340 Dichlorprop (2,4-DP) 0.005591

Triallate 0.001536 Diuron 0.000179 Methomyl 0.004920

Thiobencarb 0.001194 Thiobencarb 0.000170 Triclopyr 0.004731

Aldicarb sulfone 0.001084 p,p′-DDE 0.000162 Triallate 0.004624

Trifluralin 0.000640 Benfluralin 0.000155 Acetochlor 0.004393

Lindane 0.000610 Dinoseb 0.000094 Ethyl parathion 0.004393

α-HCH 0.000444 Cyanazine 0.000085 α-HCH 0.004128

[EC50, concentration at which 50 percent of test organisms exhibited nonlethal responses; LC50, concentration at which 50 percent mortality occurred in test organisms]
Pesticide Toxicity Index for Freshwater Aquatic Organisms

Simazine 0.000364 Trifluralin 0.000061 2,6-Dinitro-2-methylphenol 0.003576

2,6-Dinitro-2-methylphenol 0.000281 Dicamba 0.000044 Disulfoton 0.003324

Oryzalin 0.000267 Molinate 0.000038 Ethoprop 0.002971

Oxamyl 0.000205 Aldicarb 0.000029 Dichlorprop(2,4-DP) 0.002563

Diuron 0.000200 DCPA (Dacthal) 0.000027 Oryzalin 0.001887

Benfluralin 0.000183 2,4-D 0.000020 Alachlor 0.001464

Pendimethalin 0.000149 Atrazine 0.000019 Carbaryl 0.001420

Metribuzin 0.000095 Pebulate 0.000017 Methyl parathion 0.001147

2,4-D 0.000082 Dichlobenil 0.000016 Diuron 0.001139

Dichlobenil 0.000069 Butylate 0.000015 Linuron 0.001008

Dichlorprop(2,4-DP) 0.000069 Simazine 0.000013 Butylate 0.000992

Propanil 0.000060 Propham 0.000012 Oxamyl 0.000959

Pebulate 0.000059 2,4-DB 0.000011 Propanil 0.000953

EPTC 0.000053 Propanil 0.000011 Propoxur 0.000882

Propachlor 0.000051 Alachlor 0.000009 2,4-DB 0.000820

Acetochlor 0.000049 EPTC 0.000007 MCPB 0.000778

Propham 0.000040 Pebulate 0.000778

Molinate 0.000033 Metolachlor 0.000750

Alachlor 0.000025 Picloram 0.000715

Napropamide 0.000021 Dichlobenil 0.000695

2,4-DB 0.000016 Norflurazon 0.000642

Metolachlor 0.000016 Napropamide 0.000486

Prometon 0.000011 Bromoxynil 0.000446

Atrazine 0.000010 2-(2,4,5-Trichlorophenoxy) propionic acid 0.000439

Terbacil 0.000006 Molinate 0.000439

DCPA (Dacthal) 0.000005 Atrazine 0.000410

Cyanazine 0.000005 2,4,5-T 0.000397

Butylate 0.000005 Cyanazine 0.000365

Bromacil 0.000003 DCPA (Dacthal) 0.000336

Tebuthiuron 0.000001 Prometon 0.000314

Dicamba 0.000001 EPTC 0.000297

Propham 0.000184

Fluometuron 0.000168

Cladocerans Benthic invertebrates Fish

Compound

Rrelative

toxicity 

(EC50)

Compound

Relative

toxicity

 (LC50)

Compound

Relative 

toxicity

(LC50)
Tables 55

2,4-D 0.000138

Aldicarb sulfone 0.000129

Simazine 0.000110

MCPA 0.000082

Metribuzin 0.000076

Terbacil 0.000068

Tebuthiuron 0.000049

Bromacil 0.000048

Dicamba 0.000045

Pronamide 0.000041

Fenuron 0.000030

Bentazon 0.000003

Cladocerans Benthic invertebrates Fish

Compound

Rrelative

toxicity 

(EC50)

Compound

Relative

toxicity

 (LC50)

Compound

Relative 

toxicity

(LC50)