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UNITED STATES ENVIRONMENTAL PROTECTION AGENCY $&,&; t Washington, D.C. 20460 

9 P 4~ f3R0'cG 

PC Code: 077401 

DP Barcode: D255995 

MEMORANDUM July 6, 1999 

Subject: EFED Risk Assessment for the Reregistration Eligibility Decision or1 the ?-aminoethanol salt of 5-chloro-N-(2-chloro-4-nitrophenyl)-2-hydroxybenzamide 

(Niclosamide) 

To: Laura Parsons, CRM 

Susan Lewis, Chief 

Reregistration Branch I 

Special Review and Reregistration Division (7508W) I 

I From: Dana Spatz, Chemist 

Thomas M. 

Environmental Risk Branch IV 

Environmental Fate and Effects Division 

Through: Mah T. Shamim, Ph.D., Ms) 7 -6 -7 7 

Environmental Risk Branch I 

Environmental Fate and Effects Division 

This memo summarizes the EFED environmental risk assessment for niclosamide (Bayer 73@; 

BayluscideB) reregistration for use against sea lampreys (Petromyzon marinus). Although application rates 

are carefully monitored and adjusted to minimize impact to nontarget aquatic organisms, our analysis of the 

environmental fate and ecotoxicity of this lampricide, indicates the current application rates will impact nontarget aquatic organisms. When applied in combination with TFM (Lamprecidm), the toxic effects of 

lampricides are potentiated. The extent of adverse effects in the treatment area depends on streadriver 

discharge rate, pH, hardness and water temperature. Although niclosamide is likely to havean immediate 

effect on the aquatic community, the data suggest that treatment area community structure returns to pretreatment conditions within approximately 6 months. Additionally, a genuine effort is made to document 

where sensitive populations reside and steps are taken to avoid treatments at concentrations known to be 

toxic to these organisms. The long-term effects to more sensitive species, e. g., indigenous lampreys, aquatic 

earthworms and flatworms, and to aquatic communities downstream from the treatment sites where chronic 

effects are more likely, remain uncertain. 

Given the available information, it is reasonable to conclude that the effects of niclosamide on 

nontarget organisms are likely to extend beyond the immediate treatment area. Although the chronic effects 

on nontarget organisms downstream of the application site may be mitigated through dilution of the 

lampricide(s), these effects can not be characterized in this document due to the lack of data. Additionally 

the acute toxicity of newer slow-release formulations to sediment-dwelling nontarget organisms can not be 

characterized. 

1 IllllIUl~ IIIII IIIIIIIIII IIIII lllll1111 

201 2370 

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gY n \ UNITED STATES ENVIRONMENTAL PROTECTION AGENCY w $&&,$ T. Washington, D.C. 20460 

<' %% PRoT~G 

PC Code: 077401 

DP Barcode: D255995 

MEMORANDUM July 6, 1999 

Subject: EFED Risk Assessment for the Reregistration Eligibility Decision on the 2-aminoethanol salt of 5-chloro-N-(2-chloro-4-nitrophenyl)-2-hydroxybenzamide 

(Niclosamide) 

To: Laura Parsons, CRM 

Susan Lewis, Chief 

Reregistration Branch I 

Special Review and Reregistration Division (7508W) 

From: Dana Spatz, Chemist 

Thomas M. Steeger, Fishery Biologist 

Environmental Risk Branch IV 

Environmental Fate and Effects Division 

Through: Mah T. Shamim, Ph.D., Chief 

Environmental Risk Branch IV 

Environmental Fate and Effects Division 

This memo summarizes the EFED environmental risk assessment for niclosamide (Bayer 73@; 

Bayluscidem) reregistration for use against sea lampreys (Petromyzon marinus). Although application rates 

are carefully monitored and adjusted to minimize impact to nontarget aquatic organisms, our analysis of the 

environmental fate and ecotoxicity of this lampricide, indicates the current application rates will impact nontarget aquatic organisms. When applied in combination with TFM (Lamprecidm), the toxic effects of 

lampricides are potentiated. The extent of adverse effects in the treatment area depends on streamlriver 

discharge rate, pH, hardness and water temperature. Although niclosamide is likely to have an immediate 

effect on the aquatic community, the data suggest that treatment area community structure returns to pretreatment conditions within approximately 6 months. Additionally, a genuine effort is made to document 

where sensitive populations reside and steps are taken to avoid treatments at concentrations known to be 

toxic to these organisms. The long-term effects to more sensitive species, e. g., indigenous lampreys, aquatic 

earthworms and flatworms, and to aquatic communities downstream from the treatment sites where chronic 

effects are'more likely, remain uncertain. 

Given the available information, it is reasonable to conclude that the effects of niclosamide on 

nontarget organisms are likely to extend beyond the immediate treatment area. Although the chronic effects 

on nontarget organisms downstream of the application site inay be mitigated through dilution of the 

lampricide(s), these effects can not be characterized in this document due to the lack of data. Additionally 

the acute toxicity of newer slow-release formulations to sediment-dwelling nontarget organisms can not be 

characterized. 
Outstanding Data Requirements 

Environmental Fate: 

There are insufficient data available to adequately assess the environmental fate of 

niclosamide. The environmental fate data requirements that have been fulfilled are Hydrolysis (1 6 1 - 

I), Leaching-AdsorptiodDesorption (163-1) and Accumulation in Fish (165-4). An acceptable 

photodegradation in water study is needed in order to determine the extent to which niclosamide 

degrades by photolysis and to identify photoproducts. Acceptable anaerobic and aerobic aquatic 

metabolism studies are needed in order to assess the metabolic degradative potential of niclosamide 

under aquatic conditions. 

1. photodegradation in water (Guideline 16 1-2) 

2. aerobic aquatic metabolism (Guideline 162-4) 

3. anaerobic aquatic metabolism (Guideline 162-3) 

Ecological Effects: 

Many of the data requirements were addressed through the submission of non-guideline 

studies that were conducted without GLP protocol. While the chronic effects of niclosarnide in the 

immediate treatment area may be mitigated through the flushing action of the streadriver, the 

chronic effects of niclosamide on nontarget organisms downstream and more notably in the mouth 

of tributaries to the Great Lakes are uncertain. Given the possible acute effects on freshwater fish, 

the following chronic studies are requested: 

4. fish early life stage (Guideline 72-4a) 

5. fish full life cycle (Guideline 72-5) 

Additionally, given niclosamide's potential to adsorb to sediments, the use of formulations 

specifically designed to slowly release the chemical at the water-sediment interface, and the acute 

toxicity of niclosamide to aquatic invertebrates, the following acute study is requested: 

6. chironomid sediment toxicity test (Guideline 850.1790) 

Uncertainties 

The environmental fate and ecological effects of niclosamide characterized in this report are 

restricted to the specific treatment site and focuses on the acute toxicity of niclosamide given 

projected treatment levels selected to survey lamprey populations andlor achieve a sea lamprey LC,, , 

and nontarget fish LC,,. While the data suggest that treatment areas recover to pre-treatment 

community structure, certain aquatic species seem particularly sensitive to the effects of niclosamide. 

Given the persistence of niclosamide, mitigation of its effects relies predominately on the flushing 

action of the streadriver tributaries and eventual deposition and dilution in the Great Lakes. Initial 

assessments of the ecological effects assumed that niclosamide would not be persistent in the 
treatment area and that the eventual deposition of niclosamide into the Great Lakes would render 

chronic-effect studies unnecessary. While there are data to suggest that niclosamide concentrations 

within the treatment area quickly diminish to levels below quantitation within 48 hours after 

application, EFED is uncertain to the degree to which niclosamide concentrations in areas 

downstream ofthe application site are rendered ineffective. As such, the potential for chronic effects 

is uncertain particularly in the mixing zones at the confluence of tributaries with the Great Lakes. 

Additionally, newer formulations of niclosamide that result in its slow release along the streamlriver 

bottom pose an unknown risk in terms of both acute and chronic toxicity to nontarget sedimentdwelling organisms. 
Office of Pnzvention, Pesticides, 

and Toxic Substances 

Environmental Fate and Ecological Risk Assessment 

for the Reregistration Eligibility Decision 

Niclosamide (2-amino ethanol salt of 5-chloro-~-(2-chloro-4-nitro~hen~l)-2-h~drox~benzamide) 
TABLE OF CONTENTS 

INTRODUCTION ............................................................. 1 

USE CHARACTERIZATION .................................................... 2 

ENVIRONMENTAL FATE AND TRANSPORT ASSESSMENT ....................... 4 

Summary .............................................................. 4 

Chemical Identity and Physicochemical Properties .............................. 5 

Chemical Degradation .................................................... 5 

Mobility ............................................................... 6 

Bioaccumulation ........................................................ 7 

Fieldstudies ............................................................ 7 

Aquatic Exposure Assessment .............................................. 8 

ECOLOGICAL EFFECTS HAZARD STATEMENT ................................. 8 

Summary .............................................................. 8 

Toxicity to Terrestrial Animals ............................................. 9 

Avian Acute Oral , Subacute Dietary and Chronic ........................ 9 

Mammals, Acute and Chronic .............................................. 9 

Insects ................................................................. 9 

Toxicity to Freshwater Aquatic Organism ..................................... 9 

Freshwater Fish, acute, Chronic ...................................... 9 

Freshwater Invertebrates, Acute , Chronic .................................... 10 

Toxicity to Estuarine and Marine Organisms ................................. 10 

Toxicity to plants ................................................. 10 

ENVIRONMENTAL RISK ASSESSMENT ....................................... 10 

Exposure and Risk to Non-target Terrestrial Organisms ......................... 11 

Exposure and Risk to Insects .............................................. 11 

Exposure and risk to non-target Freshwater Aquatic Organisms ................... 11 

AcuteFish ...................................................... 11 

Chronicfish ..................................................... 11 

AquaticInvertebrates .................................................... 12 

Acute .......................................................... 12 

Plants ................................................................ 12 

EndangeredSpecies ..................................................... 17 

ENVIRONMENTAL RISK CHARACTERIZATION ................................ 18 

Terrestrial .............................................................. 19 

Aquatic .................................................. ; ............ 19 

Application Rate Analysis ................................................ 20 

Uncertainties .......................................................... 21 

APPENDIX 1 ECOLOGICAL TOXICITY DATA .................................. 23 
Ecological Toxicity Data ................................................. 23 

Toxicity to Terrestrial Animals ...................................... 23 

Birds. Acute and Subacute .................................... 23 

Mammals. Acute and Chronic ....................................... 25 

Toxicity to Freshwater Aquatic Animals ..................................... 25 

Freshwater Fish. Acute ............................................ 25 

Effects of Water Quality on Toxicity ............................ 26 

Toxicity of TFM:niclosamide mixture ........................... 27 

Freshwater Fish. Chronic ........................................... 28 

Freshwater Invertebrates. Acute ...................................... 28 

Toxicity of TFM and a mixture of Bayer 73 to Aquatic Invertebrates .............. 31 

Freshwater Invertebrate. Chronic ..................................... 31 

Toxicity to Estuarine and Marine Animals ................................... 32 

Estuarine and Marine Organisms. Acute and Chronic ..................... 32 

Toxicity to Plants ....................................................... 32 

Aquatic Plants ................................................... 32 

APPENDIX 2 . EXPOSURE AND RISK CHARACTERIZATION ..................... 34 

Exposure and Risk to Nontarget Terrestrial Animals ........................... 36 

Acute Risk Quotients for Avian and Mammalian Species ................. 36 

......................................................... 36 

Acute Risk Quotients for Avian and Mammalian Species ........... 36 

Exposure and Risk to Nontarget Freshwater Aquatic Animals .................... 36 

Freshwater Fish .................................................. 36 

Aquatic Invertebrates .............................................. 38 

Exposure and Risk to Nontarget Aquatic Plants ............................... 39 
INTRODUCTION 

Niclosamide (2-amino ethanol salt of 5-chloro-N-[2-chloro-4-nitrophenyl]-2- 

hydroxybenzamide) is a biocide intended to control sea lampreys (Petromyzon marinus) in streams 

and rivers tributary to the Great Lakes where these destructive organisms have impacted both the 

commercial and recreational fishery resources. Niclosamide is a halogenated mononitrobenzamide 

and is sold under the commercial name Bayluscide'. Bayluscide comes in three formulations, a 5% 

granular, a 3.2% granular, and a 70% wettable powder. The mode of action of niclosamide has been 

associated with uncoupling oxidative phosphorylation, respiratory and circulatory collapse and 

inhibition of ion-uptake. 

Niclosamide is currently registered for aquatic food and non-food uses. The registrant (U.S. 

Fish and Wildlife Service) is seeking reregistration for the EPA Product Registration 006704-00087 

(70% wettable powder Bayluscidem) and 006704-00091 (3.2% granular Bayluscide). 

According to the U.S. Fish and Wildlife Service (Johnson and Weisser 1996), of the 5,339 

streams tributary to the Great Lakes, only 449 (8.4%) are known to be or have been infested with sea 

lampreys. Currently, 150 streams (<3% of the total number of tributaries) are treated on a 3 - 5 year 

cycle. Between 1991 to 1998, 60 streams out of 426 treated with lampricides were treated with 

niclosamide mixed with a second lampricide, i. e., TFM. In 1998, a total of 178,119 m2 (44 surface 

acres) of strearnslrivers were treated with niclosamide. Of the 30 streamslrivers scheduled for 

treatment in 1999, four will receive the TFM/niclosamide mixture (pers. comm. Dorance Bregge, 

Treatment Supervisor, U.S. Fish and Wildlife Service 1999). 

Lamprey-infested streams are treated if population survey data indicate a sufficiently large 

number of transformers, i.e., larvae about to metamorphose into their parasitic adult form. As a 

lampricide, Niclosamide is used to treat only lamprey-infested tributaries to the Great Lakes and not 

the Great Lakes themselves and it can be applied only by certified applicators of the U.S. Fish and 

Wildlife Service, the Department of Fisheries and Oceans Canada, and provincial and state fish and 

game employees. Applicators are required to be familiar with and adhere to the standard operating 

procedure for lampricide applications (Appendix C). 

The Great Lakes Fishery Commission has mandated that the reliance on lampricides be 

reduced by 50%. Through a combination of physical barriers, sterile male release and fine tuning 

of lampricide applications based on pH, lampricide use has been reduced by 35% compared to levels 

used in the 1980's. Additionally, the Great Lakes Fishery Commission has projected that by the year 

201 0, lamprey populations in the Great Lakes should be reduced by 90% in Lake Superior and Lake 

Huron and that across the Great Lakes the impact of sea lampreys be reduced to better allow for 

sustained commercial and recreational yields from fish populations (Schleen et al. 1997). To 

accomplish this task and further reduce chemical reliance, the commission has recommended that 

additional research be conducted on the use of pheromones to serve as attractants to traps and 

treatment areas. Additionally, research on the use of the TFMIniclosamide mixture and lampricide 

formulations that better direct treatments to habitats favored by ammocoetes may help reduce the 

volume of lampricides required. 
USE CHARACTERIZATION 

Historically, niclosamide (Bayluscide 3.2% and 5% granular formulations) has been used 

alone as a survey method for assessing larval sea lamprey populations and has been used as a 

molluscicide (Bayluscide 5% granular formulation) in Puerto Rico for the control of snails that 

vector blood flukes responsible for the potentially debilitating disease Schistosomaisis. In most sea 

lamprey control applications however, only Trimethylfluoro nitrophenol (TFM) is applied. 

Occasionally a combination of TFM and niclosamide (Bayluscide 70% wettable powder) is applied 

to reduce the amount of TFM required for treatment. The combination is employed where large 

quantities of TFM would normally be required, such as the treatment of streams or rivers with high 

discharge rates. When used in combination, the TFM:niclosamide ratio ranges from 98:2 to 99.5:0.5 

(by weight). In practice today, niclosamide concentrations never exceed 50 ppb and the ratio is 

more commonly 99:l or less (pers. comm. Terry Morse, Treatment Supervisor, U.S. Fish and 

Wildlife Service 1999). Additionally, with the advent of the 3.2% granular formulation, the use of 

niclosamide as a lamprey control measure has been expanded to treat deep waters where the use of 

TFM would not be cost effective (pers. comm. Terry Hubert, U. S. Geological Survey Biological 

Resource Division 1999). 

Application rates for niclosamide are based on the concentration of lampricide required to 

to kill 99% of the lampreys in the treatment area. The stream minimum lethal concentration (SMLC) 

is considered to be the minimum concentration of lampricide(s) needed under specific water 

chemistry conditions for effective control (99% mortality among sea lamprey larvae during a 9-hr 

exposure). The stream maximum allowed concentration (MAC) is defined as the concentration of 

lampricide(s) which may be applied to a stream without causing "undue" nontarget mortality (25% 

mortality among sensitive fish in a 24-hr period). The objective of any treatment is to maintain 

lampricide concentrations slightly above the stream minimum lethal concentration throughout the 

treatment area. Typically concentrations of lampricide are maintained to less than or equal to 1.5 

times the stream minimum lethal concentration (Johnson and Weisser 1996) and in practice, 

lampricide applications are maintained below the LC2, of the most sensitive species (pers. comm. 

Terry Bills, Fishery Biologist, U.S. Geological Survey Biological Resource Division 1999). 

By definition, the MAC is the lethal concentration of lampricide(s) producing 25% mortality 

among a sensitive salmonid species. However, salmonids may not reflect the most sensitive 

nontarget species in a proposed treatment area and may only be intermediate in their sensitivity. In 

these cases, special accommodations are made if nontarget species, known to be more sensitive to 

niclosamide, are present. These accommodations include reducing the concentration multiple, i. e., 

to less than a factor of 1.5 the SMLC, or simply deciding not to treat a particular segment of a stream 

that serves as habitat for the sensitive nontarget species (pers. comm. Terry Bills, Fishery Biologist, 

U. S. Geological Survey Biological Resource Division 1999). Furthermore, the use of 

TFMIniclosamide mixture has been used to selectively reduce the toxicity of certain nontarget 

organisms that might normally be impacted through the use of the lampricide TFM alone. 

Application rates to achieve control of sea lamprey while minimizing impact to nontarget 

organisms are based on stream pH, alltalinit-, temperature, stream discharge, historical treatment 

data and the results of on-site bioassays involving brown trout (Salmo trutta) and ammocoete larvae. 
When used as a survey/control method, the 3.2% granular formulation of niclosamide is applied at 

a rate of 5 lbs a.i. per surface acre of water. Typically, the granules dissolve within 2 to 3 hours and 

produce a concentration of niclosamide lethal to sea lamprey in the bottom 5 cm of the water 

column. The objective is to place the granules directly onto the beds the ammocoetes inhabit and 

thus limit exposure to nontarget organisms; as the granules dissolve, niclosamide moves downstream 

and effectively "blankets" the sediment-water interface (pers. comm. Terry Hubert, U. S. Geological 

Survey Biological Resource Division 1999). When applied in combination with TFM, niclosamide 

(70% wettable powder) is first slurried with stream water and the slurry is then mixed with TFM 

(38% a.i.) in a sump pump; the combined lampricides are then metered via drip feeds or spreader 

bars using calibrated peristaltic pumps. Application rates and real-time water concentrations are 

monitored regularly (approximately 2 times per hour) to assure that water column concentrations are 

being accurately maintained. Application time is normally for 12 hours, but may be adjusted to 

assure nine hours of SMLC at downstream sites. A single application cannot be used if the 

lampricide concentration may decrease to less than the SMLC in areas in need of treatment. In these 

cases "boost" applications may be located at several locations along the treatment area. Lampricide 

concentrations are measured by spectrophotometry and HPLC within approximately 5 minutes of 

collection. Normally, niclosamide is used in larger, more eutrophic streamslrivers having pH range 

8.0 - 8.6 and high alkalinity and typically, the target concentration in these streams is 25 - 35 ppb 

niclosamide; the maximum treatment concentration is 50 ppb (pers. comm. Terry Bills, Fishery 

Biologist, U. S. Geological Survey Biological Resource Division, 1999) 

Combinations of TFMIniclosamide have been used to effectively broaden the differential 

toxicity between sea lamprey larvae and sensitive nontarget species; while the toxicity of the mix 

to nontarget species is similar to that of TFM alone, the sensitivity of ammocoete larvae is enhanced 

by the mix (pers. comm. Terry Bills, Fishery Biologist, U.S. Geological Survey Biological Resources 

Division). The difference in toxicity of the mix to ammocoetes versus sensitive nontargets allows 

for less TFM to be applied thus reducing potential impacts to nontargets 
ENVIRONMENTAL FATE AND TRANSPORT ASSESSMENT 

Summary 

The information in this assessment is based primarily on open literature studies 

submitted by the registrant to fulfill EPA data requirements. Unless otherwise noted, the data cited 

here are not from studies conducted according to Subdivision N guidelines, but nonetheless are 

considered scientifically valid and may be used in assessing the fate and transport of TFM in the 

environment. Because the open literature studies were not conducted according to the rigorous 

standards required under Subdivision N, there is some degree of uncertainty associated with the data, 

particularly if one is comparing the results of these studies to studies for other chemicals conducted 

according to Subdivision N guidance. 

In addition to dilution and dispersion, sorption to sediments and suspended particulates and 

possibly photodegradation (in clear shallow waters), are the major routes of dissipation of 

niclosamide. Neither hydrolysis nor volatilization from soil or water surfaces should be 

major fate processes for this compound. 

In most aquatic environments, niclosamide will adsorb to suspended solids and sediment. 

Though niclosamide does tend to bind to sediments, the binding is by no means irreversible, 

thus non-target species and benthic organisms in particular, will be exposed to niclosamide 

for extended periods of time. 

It is unclear what role, if any, aerobic and anaerobic microbial degradation plays in the 

dissipation of niclosamide in the aquatic environment. 

In the lake environment, degradation of niclosamide must occur in a primarily sediment-free 

system, given the high ratio of water to sediment. As such, niclosamide is expected to 

remain in solution in the lake system and persist for long periods of time. 

Based on the bioconcentration factors and the rapid rate of depuration, accumulation in fish 

is not expected. 
Chemical Identity and Physicochemical Properties 

Chemical Name 

IUPAC 

CAS Registry No. 

Empirical Formula 

Molecular Weight 

Solubility 

Synonyms 

Formulated Products 

Chemical Structure 

5-chloro-N-(2-chloro-4-nitrophenyl)-2-hydroxybenzamide 

1420-04-8 

C13H8C12N204 

327.13 

slightly soluble (230 i 50 mg/L) at 25OC; practically insoluble pH > 7.0 

niclosamide 

Bayer 73; Bayluscid 

There are insufficient data available to adequately assess the environmental fate of 

niclosamide. The environmental fate data requirements that have been fulfilled are Hydrolysis (1 61 - 

I), Leaching-Adsorption/Desorption (1 63-1) and Accumulation in Fish (1 65-4). An acceptable 

photodegradation in water study is needed in order to determine the extent to which niclosamide 

degrades by photolysis and to identi@ photoproducts. Acceptable anaerobic and aerobic aquatic 

metabolism studies are needed in order to assess the metabolic degradative potential of niclosamide 

under aquatic conditions. 

In addition to dilution and dispersion, sorption to sediments and suspended particulates and 

possibly photodegradation (in clear shallow waters), are the major routes of dissipation of 

niclosamide. Though niclosamide does tend to bind to sediments, the binding is by no means 

irreversible, thus non-target species and benthic organisms in particular, will be exposed to 

niclosamide for extended periods of time. It is unclear what role, if any, aerobic and anaerobic 

microbial degradation plays in the dissipation of niclosamide in the aquatic environment. 

Chemical Degradation 

Niclosamide does not appear to undergo hydrolytic degradation, however it does 

photodegrade in water. In a supplemental study that addressed both the hydrolysis and aqueous 

photolysis data requirements (Schultz and Harman 1978) (MRID 425523 13), [14C]niclosamide did 

not degrade either in buffered solutions adjusted to pH 5.0,6.9, or 8.7 or in pond water (pH 7.0-7.8) 

incubated in the dark for up to 56 days. Niclosamide ranged from 93 to 99% of the total 

radioactivity from each TLC plate in the study. Under photolytic conditions, niclosamide degraded 

with a half-life of 3.3 days in a pH 6.9 buffered solution that was irradiated by long-wave UV light 

for up to 14 days. A new photodegradation in water study is needed because, among other 

deficiencies, degradates were not identified, material balances were not reported, and the output of 

the light source may not have been comparable with natural sunlight. Therefore, there is a high 
degree of uncertainty surrounding the photolysis half-life. However, based on this supplemental 

study and the UVIvisible spectrum of niclosamide (max. 330 nm), it does appear that niclosamide 

is susceptible to photodegradation in water and this will be a significant route of dissipation only in 

clear and shallow water bodies. 

Mobility 

In an acceptable batch equilibrium study (Dawson et al., 1986) (MRID 42552315, 

425523 16), it was found that the mobility of niclosamide was'dependent on the pH of the system. 

Mobility appeared to increase at higher pH's. It should be noted that niclosamide reportedly 

precipitates from aqueous solutions below pH 6.5. 

Table 1. Average dissociation constants (Kd) for niclosamide at differing pH and sediment 

- ~-~ 

% organic pH 6.5 pH 7.0 pH 8.0 pH 9.0 

sediment matter average K, 

Tahquamenon River 0.9 17 14 5 1 

sand 

Ford River 

loamy sand 

Arkansas 

loam 

Cedar River sandy 9.0 3 16 

loam 

Under acidic and neutral conditions, niclosamide was not mobile. At pH 8, niclosamide was 

moderately mobile in the sand sediment, but not mobile in the other three sediments. In alkaline (pH 

9) conditions, niclosamide was very mobile in the sand and moderately to slightly mobile in the 

loamy sand, loam, and sandy loam sediments. In most aquatic environments, niclosamide will 

adsorb to suspended solids and sediment. 

K. Ho and S. Gloss (1 987) (MRID 425523 17) conducted a supplemental study to identi@ the 

most probable mechanism for loss of niclosamide from the water column. The results clearly 

showed the major route of dissipation for niclosamide from the water column, excluding dilution or 

dispersion, is adsorption to the sediment. Niclosamide concentrations decreased in the water column 

at a faster rate in beakers with lake water and sediment exposed to sunlight than in beakers without 

sediment exposed to sunlight. There was no difference in disappearance rates of niclosamide 

between light and dark beakers without sediment, indicating that photolysis may not play a major 

role in the dissipation of niclosamide. After 96 hours, 71% of the niclosamide was still present in 

beakers with sediment exposed to sunlight, versus 107% in beakers without sediment and 110% in 

dark beakers without sediment. In a test that eliminated microbial and photolytic processes, 
niclosamide concentrations decreased faster in sterile dark test tubes with sediment than in sterile 

dark test tubes without sediment. Ho and Gloss (1 987) also found no difference in disappearance 

rates of niclosamide among non-sterile light test tubes with sediment, sterile light test tubes with 

sediment and sterile dark test tubes with sediment. In the presence of sediment, the half-life of 

niclosamide in the water column was less than 10 days. 

In the lake environment, degradation of niclosamide must occur in a primarily sediment-free 

system, given the high ratio of water to sediment. As such, niclosamide is expected to remain in 

solution in the lake system and persist for long periods of time. 

Volatilization from dry and moist soil surfaces, or from water surfaces should not be a major 

fate process for this compound. The measured vapor pressure is 9.9 x mm Hg at 25 "C and the 

estimated Henry's Law constant is 6.5 x 1 0-lo atm-m3/mole. 

No data have been provided concerning the mobility of niclosamide degradates. However, 

previous information suggested that aminoniclosamide binds to sediment as well. Since 

aminoniclosamide is said to be 80-fold less toxic than parent niclosamide, confirmatory mobility 

data on this degradate is not critically important. 

Bioaccumulation 

In a supplemental study (Hubert 1996) (MRID 44 12820 I), BCF's were determined to be 49x 

for edible tissue, 21 5x for whole fish, and 91 6x for viscera in rainbow trout. The concentration of 

radioactive residues in the fish increased very rapidly to a plateau during the first three days of 

exposure. Depuration was rapid and fairly complete by day 10 of the elimination period. There is 

some degree of uncertainty surrounding the results of this study since neither the radioactivity in the 

water, nor the accumulated radioactivity in the fish tissues was identified, but was assumed to be 

parent niclosamide. There is reason for concern that photodegradates may have been present in the 

test tank, particularly since it appears that niclosamide may be susceptible to photolysis and that a 

small amount of acetone, a photosensitizer, was used as a co-solvent. However, given the stability 

of niclosamide to hydrolysis at the pH values in the study, and the flow-through design of the 

experiment, significant degradation of niclosamide in the exposure tank would not be expected. 

Field Studies 

K. Ho and S. Gloss (1 987) conducted a monitoring study (MRID 425523 17) in Seneca Lake, 

New York. The purpose of the study was to describe the distribution, dispersion, and dissipation of 

niclosamide in the water column after an application and to assess its bioaccumulation by, and 

toxicity to, two species of caged, non-target fish. 

Granular Bayer 73 was applied at a nominal rate of 110 kglha (2300 ug/L, assuming 

dissolution into the bottom 10 cm of water). Niclosamide concentrations in the lake water samples 

ranged from 40 to 573 ug/L. Concentrations were generally lowest at the surface and highest at the 

bottom (0.1 m). Although there is an expectation that niclosamide is released from granules into the 

bottom 5 cm of the water column, it was found throughout the water column; a result of either 
mixing or premature release. Concentrations greater than 40 ug1L were measured at all depths and 

stations within the treatment area. After 48 hours, all concentrations were below 30 ug/L. 

Concentrations were below the detection limit (10 ug/L) by 96 hours after application. 

Niclosamide residues in fish muscle tissue were consistent with water concentration and 

distribution patterns. Residues ranged from 0 to 858 nglg and were highest in fish from the bottom 

depth at all stations. Residues increased until 14-24 hours after application and then declined. 

The selective toxicity of granular niclosamide is based on the assumption that dissolution 

takes place at the sediment-water interface, implying that non-target fish could escape lethal 

concentrations whereas ammocoetes, which live in the substrate and are relatively weak swimmers, 

would be killed. However, the results of this investigation show that both lampreys and non-target 

fish will be exposed to niclosamide throughout the water column. 

Aquatic Exposure Assessment 

Since niclosamide is added directly to water, the estimated environmental concentrations 

(EECs) used in this evaluation were not derived from the GENeric Expected Environmental 

Concentration Program (GENEEC) but rather were based on projected treatment concentrations 

derived from when niclosamide is applied with TFM. Application rates for the TFMIniclosamide 

mixture are based on pH, alkalinity, temperature, strearnlriver discharge rates and bioassay data. 

Treatment levels of niclosamide have historically ranged between 25 to 35 ppb (pers. comm. Terry 

Bills, Fishery Biologist, U. S. Geological Survey Biological Resource Division 1999); this range of 

treatment levels was used in the aquatic risk assessment. The maximum treatment level of 

niclosarnide is 50 ppb and it was used to assess the toxicity to terrestrial organisms. 

ECOLOGICAL EFFECTS HAZARD STATEMENT 

Summary 

The information in this assessment is based on a combination of both open literature and 

studies specifically conducted to meet EPA data requirements. While all of the data included in this 

assessment (Appendix 1) were considered scientifically sound, open literature studies were not 

subject to the rigorous standards currently required under Good Laboratory Practice (GLP) protocols. 

Given the range of protocols over which the ecotoxicity data were collected, there is some 

uncertainty over how the toxicity results may have been impacted by this lack of GLP standards. 

Based on ecological effects data, the toxicity potential of niclosamide can be characterized as 

follows: 

Avian acute- moderately toxic (LD,, 60 mglkg) 

Avian subacute dietary- practically nontoxic (LC,, > 5,419 mg/kg diet() 

Mammalian acute- practically nontoxic (LD,, >1,000 mglkg) 

Fish (freshwater acute)- highly toxic to very highly toxic (LC,, 0.03 - 0.23 mg/L) • Invertebrates (freshwater) acute- slightly to very highly toxic (EC,, 0.034 - > 50 mg/L) 
Invertebrates (freshwater) chronic- (NOAEC 0.03 mgIL; LOEC 0.05 mgL) 

Aquatic plants- toxic (0.04 to > 1,450 mg1L) 

Environmental factors influenced the toxicity of niclosamide. In general niclosamide was more toxic 

as pH and water hardness decreased. When niclosamide is used in combination with TFM, the 

toxicity potential of the combined lampricides was additive. 

Toxicity to Terrestrial Animals 

Avian Acute Oral, Subacute Dieta y and Chronic 

The acute oral toxicity data suggest that niclosamide ranges in toxicity from being moderately 

toxic to practically nontoxic (LD,, 60 to > 2,000 mglkg) to avian species (MRIDs 436777-01, 

436777-02, and 44 1 803-0 1) and practically non-toxic (LC,, > 5,4 19 ppm) on a subacute dietary basis 

(MRIDs 44 1803-02 and 441 803-03). Avian chronic reproduction studies are not required. The 7 1-1 

and 7 1-2 guideline requirements for acute studies have been fulfilled. 

Mammals, Acute and Chronic 

Niclosamide was practically nontoxic to small mammals on an acute oral basis (LD,, > 1,000 

mglkg) (MRID 4255223-01). No chronic toxicity data were available. 

Insects 

A honey bee acute contact study using the TGAI is not required for niclosamide because its 

use (aquatic sites) will not result in honey bee exposure. 

Toxicity to Freshwater Aquatic Organism 

Fresh water Fish, acute , Chronic 

The data indicate that the acute toxicity of niclosamide ranges from being highly toxic to 

very highly toxic for fieshwater fish species. The most sensitive species tested were the rainbow 

trout, Onchorhynchus mykiss (LC,, = 0.03 mg/L), sea lamprey, Petromyzon marinus, (LC,, = 0.049 

mg/L) and the bluegill sunfish, Lepomis marcrochirus, (LC,, = 0.049 mg/L). The 72-1 freshwater 

fish acute toxicity requirement (Guideline 72- 1) has been fulfilled (MRID# 436793-02,44206 1-0 1). 

Because niclosamide is also used in combination with TFM, toxicity tests for the 

combination of these two chemicals are needed to assess risk. Results of tests specifically 

conducted to address this issue show that the channel catfish was the most sensitive species to TFM 

(LC,, = 0.75 mgIL), niclosamide (LC,, = 0.0125 mg/L) and to the combination of these chemicals 

(LC,, = 0.6 15 mg1L). In general, the data show that the combination of niclosamide and TFM tended 

to enhance toxicity. Based on the results of this study the authors concluded that the mixture of 

TFM:niclosamide was at most additive under various test conditions (Bills and Marking 1976). 
No data were provided on the chronic toxicity of niclosamide to fish. Thus, guideline 72-4a 

(fish early life stage) and guideline 72-5 (fish full life cycle) are not fulfilled and represent data gaps. 

Freshwater Invertebrates, Acute , Chronic 

In acute toxicity tests, niclosamide was slightly to very highly toxic to aquatic invertebrates 

(EC,, range: 0.034 to > 50 mg/L). The acute freshwater invertebrate study requirement (Guideline 

72-2) has been fulfilled (MRID# 441 748-04). 

When TFM is used in combination with niclosamide(98:2 by weight), LC,, values for the 

mixture ranged from 1.5 mg/L (moderately toxic) to greater than 100.0 mg/L (practically non-toxic) 

among freshwater invertebrates. The most tolerant species tested were crayfish, dragonflies, 

snipeflies, and dobsonflies. The most sensitive species were turbellarians, snails and aquatic 

earthworms and appeared to affect organisms inhabiting sediments. These data indicate that the 

mixture of TFM and niclosamide enhanced the toxicity of TFM to aquatic invertebrates. 

Given niclosamide's potential to adsorb to sediments, the use of formulations specifically 

designed to slowly release the chemical at the water-sediment interface, and the acute toxicity of 

niclosamide to aquatic invertebrates, data on sediment toxicity testing using chironomids would be 

of interest. 

Toxicity to Estuarine and Marine Organisms 

Because the use of niclosamide is unlikely to directly enter into estuarinelmarine 

environments, toxicity testing for these species is not required. 

Toxicity to plants 

Niclosamide inhibited the growth of aquatic plants; diatoms suffered 50% growth inhibition 

at concentrations less than 130 ppb. Green algae exhibited a considerable range in sensitivity to the 

effects of niclosamide; EC,, values ranged from 0.41 to 1,450 ppm. The studies submitted for 

review did not comply with recommended guidelines and were classified as supplemental. 

ENVIRONMENTAL RISK ASSESSMENT 

In order to evaluate th6 potential risk to aquatic and terrestrial organisms from the use of 

niclosamide, risk quotients (RQs) are calculated from the ratio of estimated envifonmental 

concentrations (EECs) to ecotoxicity values (Appendix 2 ). These RQs are then compared to levels 

of concern (LOC) criteria that is used by OPP in the determination of potential risk to nontarget 

organisms and the resulting need for possible regulatory action Based on application rates and past 

use history it has been determined that typical EECs from the use of niclosamide will range from 25 

to 35 ppm. All risk quotient calculations will be based on these EECs. 
Exposure and Risk to Non-target Terrestrial Organisms 

Niclosamide is only registered for use on aquatic sites. Therefore, the typical terrestrial 

analysis of risk, based on exposures developed by Hoerger and Kenega (1 972) and as modified by 

Fletcher et al. (1 994) is not applicable for establishing the risk of niclosamide to non-target terrestrial 

species. However, because numerous avian, i. e., waterfowl and shorebirds, and mammalian species 

(muskrats, beavers, raccoons and numerous other small mammals) typically utilize aquatic 

environments as nesting and/or feeding habitats and may be exposed to niclosamide via 

contaminated water, it is appropriate to use the aquatic EECs for conducting the risk assessment to 

terrestrial species. 

Calculated acute RQs show that there is virtually no acute risk to birds or mammals from the 

use of niclosamide (RQ < 0.01). RQs for chronic exposure were not calculated. 

Exposure and Risk to Insects 

Currently EFED does not assess risk to non-target insects. Results of acceptable studies are 

used for recommending appropriate label precautions. 

Exposure and risk to non-target Freshwater Aquatic Organisms. 

Acute Fish 

RQ values based on 96-hr LC,, values and predicted treatment levels of 25 ppb and 35 ppb 

(Figure 1) exceeded acute high risk levels of concern. Acute high risk LOCs were exceeded for sea 

lamprey and rainbow trout at a treatment level of 25 ppb; at 35 ppb, acute high risk LOCs were 

exceeded for the majority (60%) of the species tested. 

RQs for the mixture of TFMIniclosamide (98:2 by weight), based on treatment 

concentrations of 25 ppb and 35 ppb (Figure 2) indicate that acute high risk LOCs are exceeded for 

all of the fish tested. 

RQ values were examined over a range of pH (6.5 - 9.5) for rainbow trout and were based 

on treatment concentrations of 25 and 35 ppb (Figure 3). The data indicate that as water becomes 

more acidic, the risk to fish increases by roughly a factor of 10. 

Chronic fish 

No chronic toxicity data were available for fish. 
Aquatic Invertebrates 

Acute 

Aquatic acute high risk, acute restricted use, and endangered species LOCs are exceeded for 

aquatic invertebrates at the typical use rates of niclosamide (Figure 4). Acute high risk LOCs are 

exceeded for aquatic earthworms and flatworms. 

Aquatic invertebrate RQ values for the mixture of TFM and niclosamide at the minimum 

predicted concentration of 0.7 ppm, range from 0.03 to 0.46, while RQs for the maximum predicted 

treatment concentration of 2.2 ppm range from 0.08 to 1.47. Acute restricted use and endangered 

species LOC are exceeded for aquatic invertebrates at minimum predicted treatment concentrations 

for waters of pH 7.2 - 7.6. The data indicate that of the species tested, flatworms are at the greatest 

risk from the use of mixture of TFM and niclosamide to control the sea lamprey. Data suggest that 

aquatic invertebrates feeding on bottom sediments are more likely to be at risk to TFMIniclosamide 

treatments and may be a result of ingestion of TFMIniclosamide bound to detritus. 

The TFMIniclosarnide mixture results in higher toxicity to aquatic invertebrates; however, 

the increase in toxicity is not proportional to that of the lamprey. In other words, lampreys undergo 

a marked increase in toxicity to the TFMIniclosamide compared to the relatively small increase in 

sensitivity exhibited by aquatic invertebrates. This differential toxicity between sea lamprey larvae 

and nontarget aquatic invertebrates as a result of using the TFMIniclosamide mix is exploited to 

enhance mortality of ammocoetes while reducing effects on nontargets (pers. comm. Terry Bills, 

Fishery Biologist, U.S. Geological Survey 1999). 

Plants 

No acute levels of concern were exceeded for the aquatic plant species tested. At the typical 

maximum treatment rate of 35 ppb for niclosamide, green algae were the most sensitive with an RQ 

of 0.85. 
1.4 , 1 Rainbow trout 1 

1 1 A Bluegill sunfish 1 

1.21 / Sea lamprey I 

Green sunfish 

Treatment Level (ppb) 

I cute hlgh rlsk 

vel of concern 

Figure 1. Acute risk quotients (RQ) for freshwater fish based on 96-hr LC,, values and 

niclosamide treatment levels of 25 and 35 ppb. 

0.4 A 
3.5 Yellow perch 

TFM:Niclosamide (98:2 by weight) 

33 ' * Rainbow trout 

41 

0.5 1 @ Acute high risk 

Channel catfish 

0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2 

Predicted TFM Treatment Level (ppm) 

- - 

Figure 2.. Acute freshwater fish risk quotients (RQ) for niclosamide treatment levels of 25 ppb 

and 35 ppb when used in combination with trifluoromethyl nitrophenol (TFM) (98:2 by 

weight). 

level of concern. 
Figure 3. Acute freshwater fish risk quotients for rainbow trout (Oncorhynchus mykiss) for 

niclosamide treatment levels of 25 ppb and 35 ppb at various pH levels. 
Species 

* Water flea 

Scud 

Sail 

Glass shrimp 

Clam 

Crayfish 

M~dge 

Leech 

* Aquatlc earthworm 

Flatworm 

Acute high risk level 

of concern 

25 30 35 

Niclosamide Treatment Level (ppb) 

Figure 4. Acute invertebrate risk quotients (RQ) based on 96-hr LC,, values at niclosamide 

treatment levels of 25 ppb and 35 ppb. 
Endangered Species 

The endangered species LOC is exceeded for fish and aquatic invertebrates. Limitations in 

the use of niclosamide may be required to protect endangered species and threatened species, but 

these limitations have not been defined and may be site specific. The U.S. Fish and Wildlife 

Service's lamprey control program routinely engages in Section 7 consultations when 

endangeredlthreatened species are suspected to be present in treatment areas and the U. S. Fish and 

Wildlife Service is expected to modify their use of niclosamide in accordance with these Section 7 

consultations. Historically, the U. S. Fish and Wildlife Service has modified its application 

procedures to protect nontarget species. If endangered or threatened species were known to inhabit 

projected treatment sites, treatment concentrations of the lampricides would be adjusted to minimize 

impact to these species. Adjustments would include the use of TFMIniclosamide mix to broaden 

the differential toxicity of the lampricides and thus increase toxicity to sea lamprey larvae while 

holding the toxicity to nontarget species relatively constant (pers. comm. Terry Bills, Fishery 

Biologist, U.S. Geological Survey Biological Resource Division 1999; Bills et al. 1985). 

Additionally, the use of the 3.2% granular formulation has better directed the chemical to areas likely 

to harbor the ammocoete larvae. According to the U.S. Fish and Wildlife Service (pers. comm Terry 

Morse, Treatment Supervisor, U.S. Fish and Wildlife Service 1999), if treatment concentrations 

could not be adjusted to minimize impact to sensitive nontarget species, then the identified habitats 

would not be subjected to lampricide use. 
ENVIRONMENTAL RISK CHARACTERIZATION 

Estimated environmental concentrations used in this evaluation were based on typical 

treatment concentrations reported by U.S. Fish and Wildlife Service (pers. comm. Terry Bills, 

Fishery Biologist, U. S. Geological Survey Biological Resource Division 1999) that ranged from 25 - 

35 ppb. At the current treatment levels, acute high risk, acute restricted use and endangered species 

LOCs are exceeded. Use of the TFMIniclosamide mixture results in larger exceedences of the 

LOCs; however, the mixture tends to exhibit a marked increase in toxicity to sea lamprey larvae 

while nontarget organisms exhibit only a moderate increase. Although niclosamide is likely to have 

an immediate effect on the aquatic community, the data suggest that treatment area community 

structure returns to pre-treatment conditions within approximately 6 months. Additionally, a 

genuine effort is made to document where sensitive populations reside and steps are undertaken to 

avoid treatments at concentrations known to be toxic to these organisms. The long-term effects to 

more sensitive species, e. g., indigenous lampreys, and to aquatic communities downstream from the 

treatment sites where chronic effects are more likely, remain uncertain 

Because of the nature of the use of niclosamide, i. e., applied to flowing water, it is difficult 

to characterize the magnitude of the ecological effects associated with use of the chemical. Aquatic 

organisms in the treatment area are expected to be impacted to some extent during the proposed 12- 

hr treatments. Impacts to aquatic communities in terms of food-web structure are unknown. 

In addition to dilution and dispersion, sorption to sediments and suspended particulates and 

possibly photodegradation (in clear shallow waters), are the major routes of dissipation of 

niclosamide. Neither hydrolysis nor volatilization from soil or water surfaces should be major fate 

processes for this compound. In most aquatic environments, niclosamide will adsorb to suspended 

solids and sediment. Though niclosamide does tend to bind to sediments, the binding is by no means 

irreversible, thus non-target species and benthic organisms in particular, will be exposed to 

niclosamide for extended periods of time. It is unclear what role, if any, aerobic and anaerobic 

microbial degradation plays in the dissipation of niclosamide in the aquatic environment. 

In the lake environment, degradation of niclosamide must occur in a primarily sediment-free 

system, given the high ratio of water to sediment and the lack of sediments containing appreciable 

amounts of organic material (Thingvold, 1975). As such, niclosamide is expected to remain in 

solution in the lake system and persist for long periods of time. 

Although niclosamide is not expected to bioaccumulate in aquatic organisms, two potential 

exposure scenarios exist. Aquatic animals may be directly exposed to lampricide in the water as the 

chemical block moves through during roughly a 24-hr period. Additionally, predatory animals may 

be exposed through the consumption of prey incapacitated by larnpricide treaments. However, in 

a study involving the common tern (Sterna hirundo), a shore bird listed as an endangered species in 

Michigan, the bird would have to consume roughly 16.8 times its body weight in contaminated 

ammocoete larvae to approach toxic levels (Hubert et al. 1999). 

Although the immediate effects of niclosamide will likely impact streadriver community 

structure in the short term, data suggest that treated sites recolonize to pre-event structure within 6 
months of treatment. This recovery is site specific and may take much longer in certain 

environments and certain species may be significantly impacted, most notably the indigenous 

lamprey species that may populate treatment areas. In general however, native lamprey species have 

tended to populate the upper reaches of tributary streams whereas the sea lamprey is more likely to 

inhabit areas immediately adjacent to strearnlriver mouth. In practice, the species distribution of sea 

lamprey and native species is documented prior to each treatment and lampricide applications are 

designed to avoid native populations of lamprey. Thus, nontarget species that may have been 

affected in the treatment area are repopulated through downstream migration from untreated areas. 

It is believed that, given the current application rates, the effects of niclosamide are mitigated 

solely by the flushing action through the treatment site. Effects on the aquatic environment 

downstream from the treatment site are unknown and would depend heavily on the strearnlriver 

discharge rate, water temperature, pH and alkalinity and the proximity of sensitive nontarget 

organisms. While treatment areas have demonstrated a capacity to recover, the downstream acute 

and chronic effects, where niclosamide is most likely to be deposited, remain uncertain. 

Terrestrial 

Niclosamide is only registered for use on aquatic sites. However, because numerous avian 

( i. e., waterfowl and shorebirds) and mammalian species (muskrats, beavers, raccoons and numerous 

other small mammals) typically utilize aquatic environments as nesting and/or feeding habitats, and 

may be exposed to niclosamide via contaminated water, there is some potential for risk to terrestrial 

species. Additionally, the aerial application of the 3.2% granular formulation may serve as a route 

of exposure to nontarget terrestrial organisms. 

Based on the available toxicity data there is very little risk from either acute oral, acute 

dermal or subacute dietary exposure to mammals or birds. Acute RQs for both birds and mammals 

(0.00) show that there is no risk from even the maximum permissible concentration (i.e., 50 ppm) 

from the use of niclosamide. In addition, during the nearly forty years of niclosamide use to control 

or survey for the sea lamprey, there are no actual field reports documenting any acute mortality to 

avian or mammalian species. 

There are no chronic toxicity data available for avian species. However, because of the very 

low levels of exposure and the relatively short time that terrestrial species will be exposed, chronic 

risk to terrestrial species is expected to be very low. 

Aquatic 

Based on the available data, of all of the water quality parameters investigated, pH had the 

greatest influence on the toxicity of niclosamide to most aquatic organisms. At low pH, the free 

phenol state of niclosamide is practically insoluble in water and thus its use is limited to more 

alkaline waters. 
The effects of niclosamide on non-target aquatic invertebrates from sea lamprey control 

operations have been reported (Gilderhus, 1979). Although niclosamide treatment reduced the total 

number of aquatic invertebrates by 56% in the first 7 days after treatment, this effect was transitory. 

Although use history data suggest that the application of TFM to control the sea lamprey causes very 

little impact to most non-target fish, aquatic invertebrates and plant species, some effects to these 

species will undoubtedly occur. 

Although use history data suggest that the application of niclosamide to monitor and control 

the sea lamprey causes little impact to most non-target fish, aquatic invertebrates and plant species, 

some effects to these species will undoubtedly occur. Newer formulations of niclosamide that result 

in its slow release along the streamlriver bottom pose an unknown risk in terms of both acute and 

chronic toxicity to nontarget sediment-dwelling organisms. Additionally, the lack of field incident 

data should not be interpreted to mean that nontarget mortality did not occur but rather that no 

incidents have been reported. Where adverse effects to certain species and/or taxa have been 

observed, the evidence suggests that these effects are only transitory and do not threaten any 

populations of aquatic species. Although there have been some cases where recolonization of 

affected populations have taken up to 6 or 7 months, most streams recovered to pretreatment levels 

in a matter of days or several weeks. Recolonization of the treated areas usually occurs from 

untreated, up-stream portions of the tributary although some recolonization occurs from sediments 

that were too deep to be contaminated by treatment.. 

The ultimate effect that niclosamide will have on both the pest species and non-target species 

is primarily due to the pH and hardness of the treated water. Niclosamide treatments, at any 

concentration, i.e. 25 to 35 ppb and above, would be considerably more toxic under acidic 

conditions. However, niclosamide use is generally confined to more alkaline streams/rivers and 

under acidic conditions the toxicity of niclosamide is limited by the low solubility of its neutral form. 

Finally, it is apparent that niclosamde may adversely affect certain endangered and/or 

threatened species if they are exposed to niclosarnide. As such, special label directions and use 

precautions must be developed and added to the current label to prevent exposure to these species. 

Application Rate Analysis 

Decisions regarding application rates and times are based on both abiotic and biotic factors 

including pH, stream discharge, time of day, temperature, total alkalinity, in-field bioassays and 

population assessment data. Spreadsheet-based models based on the aforementioned factors have 

been developed to assist in determining application rates; the inter-relationship of the model input 

parameters is based on historical data collected from previous applications to specific streams and 

as such these predictive models are stream specific. While not all treatment sites have these 

predictive tools, on those systems undergoing marked diurnal fluctuations in pH or because of 

morphoedaphic reasons represent a complex scenario, the use of these models permits greater 

latitude in examining possible effects of input parameters on treatment concentrations and start 

times. Predicted treatment concentrations based on physico-chemical data are then modified based 

on in-field flow-through bioassays used to establish the site-specific LC,, , for sea lamprey larvae 

and the LC,, for brown trout. In Lake Superior and upper Lake Michigan, streams tend to have soft 
water with pH less than 8.2 and thus require lower application rates and are less likely to be 

candidates for niclosamide treatment. In the lower tier of the Great Lake, tributaries harboring 

lamprey may exhibit hardnesses exceeding 200 ppm with a pH range 8.1 - 8.7. These streams tend 

to have greater diurnal pH fluctuations and require that lampricide applications be adjusted to reflect 

changing pH. Typically however, diurnal pH fluctuations do not dramatically affect initial target 

concentrations and lampricide concentrations remain primarily based on the lower estimate of pH 

because of the increased toxicity potential of the lampricide at lower pH. Niclosamide target 

concentrations in hard water streams have ranged from 25 to 35 ppb; however, treatment 

concentrations are not permitted to exceed 50 ppb (pers. comm. Dorance Brege, U.S. Fish and 

Wildlife Service Treatment Supervisor 1999). 

Uncertainties 

The environmental fate and ecological effects of niclosamde characterized in this report are 

restricted to the specific treatment site and focus on the acute toxicity of niclosamide given projected 

treatment levels selected to achieve a sea lamprey LC,, , and nontarget fish LC2,. Given the 

persistence of niclosamide, mitigation of its effects relies predominately on the flushing action of 

the streadriver tributaries and eventual deposition and dilution in the Great lakes. Initial 

assessments of the ecological effects assumed that niclosamide would not be persistent in the 

treatment area and that the eventual deposition of niclosamde into the Great Lakes would render 

chronic-effect studies unnecessary. However, EFED is uncertain to the degree to which treatment 

site concentrations of niclosamde are rendered ineffective. As such the potential for chronic effects 

is uncertain particularly in the mixing zones at the confluence of tributaries with the Great Lakes. 

While the data suggest that treatment areas recover to pre-treatment community structure, certain 

species seem particularly sensitive to the effects of niclosamide and may not recover. While the 

direct effects of niclosamide treatments have been partially characterized, the secondary effects on 

food chains and the ability of nontarget species to feed during the recovery period is uncertain. 

Although the ecological data gaps identified in this document may address uncertainties over 

potential chronic effects, the environmental fate of niclosamide downstream of application sites, i. e., 

the stredriver deltas is uncertain without monitoring studies to quantify niclosamide concentrations 

in the mixing zones. Additionally, newer formulations of niclosamide that result in its slow release 

along the streadriver bottom pose an unknown risk in terms of both acute and chronic toxicity to 

nontarget sediment-dwelling organisms. 

BIBLIOGRAPHY 

Bills, T. D. and L. L. Marking. 1976. Toxicity of 3-trifluoromethyl-4-nitrophenol (TFM), 2',5- 

Dichloro-4'-nitrosalicylanide (Bayer 73), and 98.2 Mixture to Fingerlings of Seven Fish Species and 

to Eggs and Fry of Coho Salmon. US Fish and Wildlife Service, Investigations in Fish Control 

No.69 .pgs 1-9. 

Dawson, V. 1986. Adsorption-Desorption of [14C]-Bayer 73 by Bottom Sediments. Final Report 

No. BST-83-977.05. Unpublished study performed by the U.S. Fish and Wildlife Service, National 

Fisheries Research Center, La Crosse, WI, and the U.S. Fish and Wildlife Service, Marquette 
Biological Station, Marquette, MI; and submitted by the U.S. Fish and Wildlife Service, National 

Fisheries Research Center, La Crosse, WI. MRID 425523 16. 

Dawson, V., D. Johnson and J. Allen. 1986. Loss of Lampricides by Adsorption on Bottom 

Sediments. Can. J. Fish. Aquat. Sci., 43: 1515-1520. MRID 425523 15. 

Gilderhus, P. A. 1979. Effects of granular 2',5-dichloro-4'-nitrosalicylanilide (Bayer 73) on benthic 

macroinvertebrates in a lake environment. Great Lakes Fishery Commission Technical Report 34 

:ppl-11. 

Ho, K. and S. Gloss. 1987. Distribution and Persistence of the Lampricide Bayer 73 Following a 

Control Application. Can. J. Fish. Aquat. Sci., Vol44, pp. 1 12-1 19. Performed by Cooperative Fish 

and Wildlife Research Unit, Dept. of Natural Resources, Cornell University. 

MRID 425523 17. 

Hubert, T. 1996. Accumulation of the Lampricide Niclosamide by Rainbow Trout: Pilot Study. 

Unpublished study performed by Upper Mississippi Science Center, NBS, La Crosse, Wisconsin. 

Submitted by National Biological Service, United States Department of the Interior. 

MRID 44128201. 

Hubert, T. D., M. A. Boogaard, T. A. Morse, T. D. Bills, D. A. Johnson, and L. P. Scheen. 1999. 

Determination of niclosamide concentrations in sea lamprey ammocoetes following acute exposure 

to tow formulations of Bayluscide. Project completion report submitted to the Executive Secretary, 

Great Lakes Fishery Commission, Ann Arbor, Michigan. 

Johnson, D. A. and J. W. Weisser. 1996. Field toxicity data regarding exposure levels and effects 

of TFM and Niclosamide on fish and aquatic invertebrates. Upper Mississippi Science Center, 

National Biological Service. 

Maki, A.W., L. Geissel. and H. E. Johnson. 1975. Toxicity of the lampricides 3-trifluoromethyl-4- 

nitrophenol (TFM) to 10 species of algae. U.S. Fish and Wildlife Serv., Invest, Fish Control 56:3- 

17. 

Marking, L.L., and L. E. Olson. 1975 Toxicity of the lampricides 3-trifluoromethyl-4-nitrophenol 

to non-target fish in static tests. U.S. Fish Wildl. Serv., Invest. Fish Control 60: 3-27. 

NRCC. 1985. TFM and Bayer 73 in the Aquatic Environment. Envir. Sec. Publ. NRCC 22488, 

Otawa, Ontario, 203 pp. 

Schultz, D. and P. Harrnan. 1978. Hydrolysis and Photolysis of the Lampricide 2',5-dichloro-4'- 

nitrosalicylanilide (Bayer 73). U.S. Department of the Interior, Fish and Wildlife Service Report No. 

85. MRID 42552313. 

Thingvold, D. and G. Lee. 1988. Persistence of TFM in Aquatic Environments. Environmental 

Science and Technology, vol. 15, no. 11, p. 1335-1340. MRID 425518-07. 
APPENDIX 1 ECOLOGICAL TOXICITY DATA 

Ecological Toxicity Data 

Toxicity to Terrestrial Animals 

Birds, Acute and Subacute 

An acute oral toxicity study using the technical grade of the active ingredient (TGAI) is 

required to establish the toxicity of niclosamide to birds. The preferred test species is either mallard 

duck (a waterfowl) or bobwhite quail (an upland gamebird). The LD,, ranged from 532 mgkg to 

greater than 2,000 mglkg in mallard ducks and based on these data niclosamide is categorized as 

slightly toxic to avian species on an acute oral basis (Table 1). In the Hudson (1979) study, 

niclosamid produced intoxication in all ofthe species tested (mallard ducks, bobwhite quail and ringbilled gulls) at all of the oral-dosage levels administered. Signs of toxicity observed in mallards 

included tenseness of the masseter, regurgitation, excessive drinking and sitting, imperturbability, 

incoordination, imbalance, rapid and labored breathing, tremors, and temporary whole-body rigidity. 

However, current guideline (71-1) requirements were not fulfilled by the Hudson study since 

technical grade active ingredient was not used, exposure concentrations were not reported, and no 

raw data were provided. In the Palmer (1996) study, they failed to establish that the toxicity was 

greater than 2,000 mglkg. While regurgitation was problematic in doses greater than 532 mglkg, 

the study failed to note any signs of toxicity that had been reported in previous studies. Thus, it is 

difficult to reconcile the results from these two studies 

Supplemental data were provided through an acute oral toxicity study of redwing blackbirds 

Agelaius phoeniceus (Schafer 1982; MRID 436777-0 1 ; this study was classified as supplemental 

since neither mallard ducks nor bobwhite quail were tested, the purity of the test substance was not 

specified, appropriate controls were not reported, and specific methodologies were not provided in 

the report. The estimated LD50 was 60 mg and based on this estimate, niclosamide is classified as 

moderately toxic to birds. Although the none of the studies meet all of the current 71-1 guidelines, 

no additional acute oral toxicity studies are required at this time and in general niclosamide is 

classified as being moderately toxic to birds. 
Table 1. Avian acute oral toxicity of niclosamide in northern bobwhite quail (Colinus 

Species % ai LD~o Toxicity Category MRID No. Study 

(mglkg) AuthorIYear Classification' 

Northern bobwhite quail 70% >2,000 practically nontoxic 436777-02 

(Colinus virginianus) Hudson 1979 supplemental 

436777-01 

Redwing blackbird -- 60 mglkg Schafer, Bowles, (Agelaius phoenlceus) moderately toxlc and Hurlbut supplemental 

1983 

436777-02 

70% >2,000 practically nontoxic Hudson 1979 supplemental 

Mallard duck 

(Anas platyrhynchos) 441803-01 

100% 532 slightly toxic supplemental Palmer and 

Beavers 

' Core (study satisfies guideline). Supplemental (study is scientifically sound, but does not satisfy guideline) 

Two subacute dietary studies using the TGAI are required to establish the toxicity of 

niclosamide to birds. The preferred test species are mallard duck and bobwhite quail. Since the LC,, 

falls in the range > 5,000 ppm (Table 2), niclosamide is categorized as practically nontoxic to avian 

species on a subacute dietary basis. The guideline (71 -2) is fulfilled (MRID 441 803-02 and 441 803- 

03). 

Table 2. Subacute avian dietary toxicity of niclosamide to northern bobwhite quail (Colinus - 

virginianus) and mallard ducks (Anas platyrhynchos) 

Species % ai 5-Day LC,, Toxicity Category MRID No. Study 

(PP~)' AuthorIYear Classification 

441803-02 

Northern bobwhite quail 100% >5,419 practically nontoxic Palmer and 

(Colinus virginianus) Beavers Core 

1996 

441803-03 

Mallard duck 100% >5,648 practically nontoxic Palmer and 

(Anas platyrhynchos) Beavers Core 

1996 

In studies involving TFM:niclosamide (98:2) mixtures, the combination resulted in toxicity 

values that were similar to when TFM was the single active ingredient (Table 3). 
Table 3. Acute Oral Toxicity of a mixture of TFM and niclosamide (98:2 by weight) to avian species. 

Species %a.i. LD50 MRID Toxicity category 

(TFM) mglkg lauthorlyear 

Mallard duck 96 472 160000/ moderately-toxic 

(Anas platyrhynchos) Hudson, 1979 

Ring-billed gull 35 154 1600001 moderately-toxic 

(Larus delawarensis) Hudson, 1979 

Mammals, Acute and Chronic 

Wild mammal testing is required on a case-by-case basis, depending on the results of lower 

tier laboratory mammalian studies, intended use pattern and pertinent environmental fate 

characteristics. In most cases, rat or mouse toxicity values obtained from the Agency's Health 

Effects Division (HED) substitute for wild mammal testing. Of the six mammalian acute toxicity 

studies reviewed by HED, two (Guidelines 8 1-5 and 8 1-6) were listed as acceptable (Table 4). 

Guideline 8 1-3 was classified as inadequate and Guidelines 8 1 - 1,8 1-2, and 8 1-4 were classified as 

unacceptable. 

Table 4. Acute mammalian toxicity of Niclosamid to the Norway rat (Ruttiis norvegicus) (NS = not specified). 

Species1 Test Toxicity Affected 

Study Duration % ai Type Value Endpoints MRID No. 

laboratory rat 

(Rattus norvegicus) 

NS Acute oral Rat LD,, > 1,000 mglkg no mortality or 4255223-01 

clinical signs 

rabbit NS Acute dermal LD,, > 2,000 mglkg no mortality or 4255223-01 

clinical signs 

In HED's assessment of the acute and subchronic mammalian toxicity, no definitive 

conclusions were drawn from the data other than to note that the available studies do not satisfy 

either the acute or subchronic toxicity testing requirements for niclosamide. In general, niclosamide 

treatment did not appear to result in any treatment-related deaths or signs of toxicity; however, given 

the classification of the mammalian toxicity studies, there is a large degree of uncertainty in 

ascertaining the mammalian toxicity. 

Toxicity to Freshwater Aquatic Animals 

Freshwater Fish, Acute 

Two freshwater fish toxicity studies using the TGAI are required to establish the toxicity of 

niclosamide to fish. The preferred test species are rainbow trout (a coldwater fish) and bluegill 

sunfish (a warmwater fish). Results (Table 5) indicate that rainbow trout appeared to be an order 

of magnitude more sensitive to the effects of niclosamide than were bluegill sunfish and that rainbow 

trout and sea lamprey were equally sensitive to the effects of niclosamide. Since the LC,, falls in 
the range of < 0.1 ppm, niclosamide is categorized as very highly toxic to fieshwater fish on an acute 

basis. The guideline (72-1) is fulfilled (MRID 436793-02). 

Table 5. Freshwater fish acute toxicity of niclosamide to the rainbow trout (Oncorhynchus mykiss) and bluegill 

sunfish (Lepomis macrochirus) and sea lamprey (Petromyzon marinus). 

Species1 96-hour 

% ai Toxicity LC*,, (PP~) MRID No. Study 

Flow-through or Static (measuredlnominal) Category AuthorNear Classification 

Rainbow trout 

static 

436793-01 

very highly Marking and Hogan supplemental toxic 1967 

Rainbow trout 

static 

very highly 436793-03 

toxic Bills and Marking supplemental 

1976 

Rainbow trout 

static 

436793-04 

very Dawson et al. 1976 supplemental 

toxic 

436793-06 

Rainbow trout 70 % 0.14 highly toxic Rye and King Supplemental 

1976 

Bluegill sunfish very highly 436793-01 

toxic Marking and Hogan supplemental 

1967 

Bluegill sunfish highly toxic 436793-02 

Farringer 1972 core 

Bluegill sunfish 436793-03 

NS 0.152 highly toxic . Bills and Marking supplemental 

1976 

Bluegill sunfish 442061-011441748-01 

highly toxic Drottar and Swigert core 

Sea lamprey 0.049 

(nominal) 

very highly 436793-06 

toxic Rye and King Supplemental 

1976 

Carp 436793-02 

(Cyprinus carpio) 99 % 0.120 ppm highly toxic J. E. Farringer Supplemental 

1972 

Green sunfish 436793-02 

(Lepornis cyanellus) 99 % 0.170 ppm highly toxic J. E. Farringer Supplemental 

1972 

Effects of Water Quality on Toxicity 

Water quality affected the toxicity of niclosamide. Table 6 illustrates the effect of pH on the 

toxicity of niclosamide to rainbow trout. Trout were roughly 7-times more sensitive to niclosamide 

at pH 6.5 than they were at pH 9.5. The data emphasize that with decreasing pH (increasing 

aciditity) the toxicity of niclosamide to fish increases. Additionally, increasing alkalinity decreased 

the toxicity of niclosamide (Table 7). 
Table 6. Comparison of 96-hr LC,, estimates for rainbow trout treated with niclosamide using differing pH at 

120C amd water hardness Of 44 mg/L as CaCO, (NRCC 1985). 

PH 96-hr LC,, 

6.5 0.0261 (0.0197 - 0.0345) 

Table 7. Comparison of LC,, estimates for carp (Cyprinus carpio) and green sunfish (Lepomis cyanellus) treated 

with niclosarnide using diffehng water hardness. 

hardness (mgll as CaCO,) carp green sunfish 

96-hr LC;, 96-hr LC,, 

Toxicity of TFM:niclosamide mixture. 

TFM is used with niclosamide under different situations and environmental conditions to 

obtain control of the sea lamprey. As such, it has been determined that data on the interaction of 

these two pesticides are required to establish the toxicity of TFM to freshwater fish species when 

used in conjunction with niclosamide. Toxicity estimates for the TFMIniclosamide (98:2) mixture 

are presented in Table 8. The toxicity of TFM was 20 to 50% greater with the addition of 

niclosamide. In general, the data show that the mixture of TFM:niclosamide was additive in toxicity 

to fish under various test conditions (Maki, 1975). The increased sensitivity of channel catfish to 

the lampricide TFM relative to the sunfish is reflective of differences in the ability of catfish to 

conjugate and eliminate TFM. Similar to the sea lamprey, channel catfish have a less efficient 

glucuronidation mechanism than the sunfish (Kane et al. 1994). The sea lamprey's ability to 

biotransform TFM is relatively low and channel catfish exhibit an intermediate ability to 

biotransform TFM compared to the centrarchids and perches. 
Table 8. Toxicity of TFM/niclosamide (98:2), based on a.i., to seven species of fish in soft water at 12°C. 

Species 96-hr. LC50 96-hr. LC,, Combination MRIDI Toxicity category 

TFM Bayer73 Toxic~ty AuthorIYr. 

(PP~) (ppm) (PP~) 

Brown trout 0.94 0.02 0.98 Bills&Marking highly toxic 

1976 

Rainbow trout 1.81 0.0237 1.16 Bills&Marking moderately toxic 

1976 

Rainbow trout 1.6 441869-021 moderately toxic 

Drottar&Swigert/ 

1996 

Lake trout 1.78 0.0284 1.39 Bills&Marking moderately toxic 

1976 

Brook trout 

Channel catfish 

0.0237 1.16 Bills&Marking moderately toxic 

1976 

highly toxic 

Bluegill 4.89 0.0636 3.18 Bills&Marking moderately toxic 

1976 

Bluegill 7.3 441869-01 moderately toxic 

Drottar&Swigert 

11996 

Yellow perch 1.71 0.0184 0.9 Bills&Marking highly toxic 

1976 

Freshwater Fish, Chronic 

A freshwater fish early life-stage test using the TGAI is required according to Section 

158.490(5): (i) niclosamid is directly applied to water and (ii) the LC,, is less than 1 ppm (0.19 ppb 

in Daphnia magna and 0.34 ppb in trout. None of the studies submitted to support the reregistration 

ofNiclosamid provided useful data to address the 72-4a guideline requirement and as such represents 

a data gap. 

Fresh water Invertebrates, Acute 

A freshwater aquatic invertebrate toxicity test using the TGAI is required to establish the 

toxicity of niclosamide to aquatic invertebrates. The preferred test species is Daphnia magna. The 

toxicity of niclosamide to freshwater aquatic invertebrates spanned roughly three orders of 

magnitude (0.03 ppm - > 50 ppm); since some LC,,/EC,, fall in the range of < 0.1 ppm, niclosamide 

is categorized as very highly toxic to aquatic invertebrates on an acute basis. The guideline (72-2) 

is fulfilled (MRID 441 748-04 ). 

Additional data were provided through a study of the effects of niclosamide (5% granular 

formulation) on benthic macroinvertebrates in a lake environment. Total numbers of organisms in 

the treated area dropped 56% within 7 days posttreatment and primarily affected oligochaetes and 

midge larvae; however, by 13 days posttreatment, the numbers of these organisms had increased 
(Gilderhus 1979). Other species, e.g., mayfly nymphs and amphipods, were not substantially 

affected by the niclosamide treatment. The study concluded that the niclosamide is expected to have 

only moderate effects of short duration on populations of rnacroinvertebrates. 
Table 9. Freshwater invertebrate acute toxicity of niclosamide. 

SpeciesIStatic or Flow- 96-hour LC,,/ 

% ai Toxicity Category MRID No. Study 

through ECs, (PP~) Authornear Classification (measured/nominal) 

Waterflea 

(Daphnia magna) 0.32 pprn 

441 748-04 

70% highly toxic Drottar and Swigert (mean-measured) Core 

1996 

Waterflea 0.2 pprn 

(nominal) 

436793-05 

highly toxic H. 0. Sanders Supplemental 

1977 

Scud 

(Gammaruspseudolimnaeus) 70% 2.4 pprn 

436793-05 

moderately toxic H. 0. Sanders Supplemental (nominal) 1977 

Scud 2.6 pprn 436793-06 

moderately toxic Rye and King Supplemental (nominal) 1976 

Snails 

(Physa sp.) 0.106 pprn 

(nominal) 

436793-06 

highly toxic Rye and King Supplemental 

1976 

Snails 

(Pleurocera sp.) 0.36 pprn 

(nominal) 

436793-06 

highly toxic Rye and King Supplemental 

1976 

Glass shrimp 

(Palaemonetes kadiakensis) 70% 

436793-05 

10 PP~ moderately toxic H. 0. Sanders Supplemental 

(nominal) 1977 

Clam 

(Eliptio dilatatus) 0.382 pprn 

(nominal) 

436793-06 

highly toxic Rye and King Supplemental 

1976 

Crayfish 

(Orconectes nais) 25 PPm 

(nominal) 

436793-05 

slightly toxic H. 0. Sanders Supplemental 

1977 

Crayfish >50 pprn 

(nomial) 

436793-06 

slightly toxic Rye and King Supplemental 

1976 

Midge 436793-05 

(Chironomus plumosus) 70% 1 5 PP~ moderately toxic H. 0. Sanders Supplemental (nominal) 1977 

Waterflea 0.8 pprn 

(nominal) 

436793-06 

highly toxic Rye and King Supplemental 

1976 

Leeches 

(Erpobdellidae) 0.42 pprn 

(nominal) 

436793-06 

highly toxic Rye and King Supplemental 

1976 

Aquatic earthworms 436793-06 

very highly toxic Rye and King Supplemental 

1976 

Turbellarian 436793-06 

(Dugesia tigrina) 70% 0.048 very highly toxic Rye and King Supplemental 

1976 

'48-hour toxicity endpoint 
Toxicity of TFM and a mixture of Bayer 73 to Aquatic Invertebrates 

Under certain conditions and situations, TFM is used with Bayer 73, another lampricide, to 

control of the sea lamprey. As such, it has been determined that data on the interaction of these two 

pesticides are required to establish the toxicity of TFM to freshwater aquatic invertebrate species. 

Results of these studies are tabulated below: 

Table 9. Toxicity of TFM:Bayer 73 (98:2 based on active ingredient) to aquatic invertebrates. 

Species 

98:2 

mixture Bayer 73 MRIDIautho 24-h Toxicity category 

LC50 LC50 rlyear 

mgll 

Turbellarium 1.5 0.048 Rye and moderately toxic 

King, 1976 

Aquatic earthworms 2.25 0.034 moderately toxic 

Leeches 4 0.42 moderately toxic 

Daphnid 7.35 0.8 moderately toxic 

Isopod 31 23.0 slightly toxic 

Scuds 26 2.6 slightly toxic 

Crayfish > 100 > 50 practically non-toxic 

Stoneflies 15.4 1.07 slightly toxic 

Dragonflies > 100 > 50 practically nontoxic 

Burrowing mayflies 

Blackflies 

Snipeflies 

Dobsonflies 

Clam 

Pleurocera sp. 

Physa sp. 

4 6.9 moderately toxic 

3.45 0.255 moderately toxic 

> 100 > 50 practically non-toxic 

> 100 > 50 practically non-toxic 

4.7 0.382 moderately toxic 

9.4 0.355 moderately toxic 

1.93 0.106 moderately toxic 

These data indicate that LC50 values for a mixture (98:2 by weight) of TFM and Bayer 73 

range from 1.5 (moderately toxic) to more than 100.0 mglliter (practically non-toxic). The most 

tolerant species tested were crayfish, dragonflies, snipeflies, and dobsonflies. The most sensitive 

species were turbellarians, snails and aquatic earthworms. These data suggest that the mixture of 

TFM and Bayer 73 is less toxic to aquatic invertebrates than Bayer 73 alone. 

Fresh water In vertebrate, Chronic 

A freshwater aquatic invertebrate life-cycle test using the TGAI is required for Niclosamde 

since the end-use product is applied directly to water, the aquatic acute LC5,/EC5, is less than 1 mg/L 

and the EEC in water is equal to or greater than 0.01 of the acute LC5,/EC5,. The preferred test 

species is Daphnia magna. Results of this test are tabulated below. Similar to acute toxicity 
estimates, chronic toxicity studies indicated that waterfleas were an order of magnitude more 

sensitive to the effects of niclosamide than were midges. 

Table 10. Freshwater aauatic invertebrate life-cvcle toxicitv using niclosamide. 

Species/Static 21-day 

Renewal or Flow- % ai NOEC/LOEC MATC' Endpoints MRID No. Study 

through mg/L (PP~) Affected AuthorIYear Classification 

Waterflea 0.056 mg/L reproduction 441872-01 (Dapknia magna) 100% 0.108 mg/L 0.078 ppm length Drottar and Swigert Core 

1996 

Waterflea 436793-05 

0'032 mgiL 0.042 pprn reproduction 70% 0.055 mgiL H.O. Sanders Supplemental 

1997 

Midge 436793-05 

(Ckironomusplumosus) 70 % 0'32 mg/L 0.42 ppm emergence H.O. Sanders Supplemental 0.55 mg/L 1997 

I defined as the geometric mean of the NOEC and LOEC. 

Toxicity to Estuarine and Marine Animals 

Estuarine and Marine Organisms, Acute and Chronic 

Neither acute nor chronic toxicity testing with estuarinelmarine organisms using the TGAI 

is required for niclosamide because the end-use product is not intended for direct application to the 

marinelestuarine environment nor is the active ingredient is expected to reach this environment 

because it is not used in coastal counties. 

Toxicity to Plants 

Aquatic Plants 

Normally, aquatic plant testing is not required for pesticides other than herbicides and 

fungicides except on a case-by-case basis (e.g., labeling bears phytotoxicity warnings incident data 

or literature that demonstrate phytotoxicity). However, given that niclosamide is applied directly to 

the water and given its toxicity to aquatic organisms, aquatic plant testing is required. The following 

species should be tested at Tier I: Kirchneria subcapitata and Lemna gibba. Results of Tier I 

toxicity testing on the technical1TEP material using diatoms and green algae (Table 1 1) indicate that 

EC50 values ranged over four orders of magnitude (range 0.04 - 1,450). The species tested did not 

conform to the recommended species and the test conditions were poorly defined, thus, guideline 

122-2 is not fulfilled. 
Table 11. Nontarget aquatic plant toxicity testing using niclosamide. 

Species % ai EC50 MRID No. 

(PP~) AuthoriYear Study Classification 

Diatoms 

Ankistrodesrnus falcatus 

Scenedesrnus quadricauda 

0.103 

70 Ibrahim 1984 Supplemental 

0.130 436793-10 

Skeletonema costaturn 

Amphiprora paludosa 

Ibrahim 1984 

436793-10 Supplemental 

Phaeodactylum tricornutum 0.041 
APPENDIX 2. EXPOSURE AND RISK CHARACTERIZATION 

Risk characterization integrates the results of the exposure and ecotoxicity data to evaluate 

the likelihood of adverse ecological effects. The means of this integration is called the quotient 

method. Risk quotients (RQs) are calculated by dividing exposure estimates by acute and chronic 

ecotoxicity values. 

RQs are then compared to OPP's levels of concern (LOCs). These LOCs are used by OPP 

to analyze potential risk to nontarget organisms and the need to consider regulatory action. The 

criteria indicate that a pesticide used as directed has the potential to cause adverse effects on 

nontarget organisms. LOCs currently address the following risk presumption categories: (1) acute 

high -- potential for acute risk is high; regulatory action may be warranted in addition to restricted 

use classification, (2) acute restricted use -- the potential for acute risk is high, but may be mitigated 

through restricted use classification, (3) acute endangered species - endangered species may be 

adversely affected, and (4) chronic risk - the potential for chronic risk is high regulatory action may 

be warranted. Currently, EKED does not perform assessments for chronic risk to plants, acute or 

chronic risks to nontarget insects, or chronic risk from granularlbait formulations to birds or 

mammals. 

The ecotoxicity test values (, measurement endpoints) used in the acute and chronic risk 

quotients are derived from required studies. Examples of ecotoxicity values derived from short-term 

laboratory studies that assess acute effects are: (1) LC,, (fish and birds), (2) LD,, (birds and 

mammals), (3) EC,, (aquatic plants and aquatic invertebrates) and (4) EC25 (terrestrial plants). 

Examples of toxicity test effect levels derived fi-om the results of long-term laboratory studies that 

assess chronic effects are: (1) LOEC (birds, fish, and aquatic invertebrates), (2) NOEC (birds, fish 

and aquatic invertebrates), and (3) MATC (fish and aquatic invertebrates). For birds and mammals, 

the NOEC generally is used as the ecotoxicity test value in assessing chronic effects, although other 

values may be used when justified. Generally, the MATC (defined as the geometric mean of the 

NOEC and LOEC) is used as the ecotoxicity test value in assessing chronic effects to fish and 

aquatic invertebrates. However, the NOEC is used if the measurement end point is production of 

offspring or survival. 

Risk presumptions and the corresponding RQs and LOCs, are tabulated below. 
Table 1 Risk Presumptions for Terrestrial Animals 

Risk Presumption RQ LOC 

Birds 

Acute High Risk EEC1ILCjO or LD,,/sqft2 or LDjo/day3 0.5 

Acute Restricted Use EECILC,, or LDjdsqft or LD,,/day (or LD,, < 50 mglkg) 0.2 

Acute Endangered Species EECLC,, or LD,,/sqft or LD,,/day 0.1 

Chronic Risk EEC/NOEC 1 

Wild Mammals 

Acute High Risk EECILC,, or LD,,/sqft or LD,,/day 0.5 

Acute Restricted Use EECILC,, or LD,,/sqft or LD,,lday (or LD,, < 50 mglkg) 0.2 

Acute Endangered Species EECILC,, or LD,,/sqft or LDjO/day 0.1 

Chronic Risk EEC.1'OEC I 

' abbrwiation for Estimated Environmcntal Concmtration (ppm) on a\.ianimammalian food itcms 

mg/ft2 ' mg of toxicant consumedlday 

LDjo * wt. of bird LD,, * wt. of bird 

Table 2 Risk presumptions for aquatic animals 

Risk Presumption RQ LOC 

Acute High Risk 

Acute Restricted Use 

Acute Endangered Species 

EEC1/LCSo or EC,, 

EEC/LC,, or EC,, 

EECILC,, or EC,, 

Chronic Risk EECIMATC or NOEC 1 

EEC = (ppm or ppb) in water 

Table 3 Risk presumptions for plants 

Risk Presumption RQ LOC 

Terrestrial and Semi-Aquatic Plants 

Acute High Risk 

Acute Endangered Species 

Acute High Risk 

EEC1/EC25 

EECIECO5 or NOEC 

Aquatic Plants 

EEC2IEC5, 

Acute Endangered Species EECIECOS or NOEC 1 

EEC = Ibs ai/A 

EEC = (ppblppm) in water 
Exposure and Risk to Nontarget Terrestrial Animals 

Acute Risk Quotients for Avian and Mammalian Species 

Acute Risk Quotients for Avian and Mammalian Species 

Niclosamide is only registered for use on aquatic sites. Therefore, the typical terrestrial 

analysis of risk, based on exposures developed by Hoerger and Kenega (1 972) and as modified by 

Fletcher et al., (1994), is not applicable for establishing the risk of niclosamide to on-target 

terrestrial species. However, because numerous avian, i.e., waterfowl and shorebirds, and 

mammalian species (muskrats, beavers, raccoons and numerous other small mammals) typically 

utilize aquatic environments as nesting and/or feeding habitats and may be exposed to niclosamide 

via contaminated water, it is appropriate to use the aquatic EECs for conducting the risk assessment 

to terrestrial species. Tables 4 and 5 show the RQ values for birds and mammals, respectively, based 

on a target stream concentration of 9 ppm. 

Table 4. Acute risk quotients for avian species. 

Species LC,, EEC (pprnl* Risk Quotient 

PP'" 

Bobwhite quail 

(Colinus virginianus) 

Mallard duck > 5,648 0.050 0 

(Anas platyrhynchos) 

* The typical concentration expected to occur in streams treated with Niclosamidewas used to predict exposure and calculated the RQ. 

Table 5. Acute risk quotients for mammalian species. 

Species Body % body EEC LC,, Risk Quotient* 

weight wt. (PP~)* PPm 

Consumed 

small mammal 15 10 0.050 > 1,000 0 

1000 10 0.050 0 

* RQ= EEC (ppm) 

LDso(mg/kg)/O/~ Body wt. Consumed 

The analysis of the data shows that no terrestrial species LOC are exceeded from the 

proposed use of niclosamide. In addition, there are no reported incidents involving niclosamide and 

any terrestrial species. 

Exposure and Risk to Nontarget Freshwater Aquatic Animals 

Fresh water Fish 

RQ values calculated for the minimum EEC of 25 ppb (Table 6), range from 0.15 to 0.83. 

Acute restricted use LOCs were exceeded in 40% of the fish represented. At a treatment 

concentration of 35 ppb, RQ values ranged from 0.29 to 1.3 1 ; acute high risk LOCs were exceeded 

in 50% of the fish represented. 
Table 6. Summary of risk quotients to fresh water fish species based on predicted treatment levels of 

niclosamide at 25 and 35 ppb. 

Species/ EEC 96-hour 

Flow-through or Static (PP~) LC,, (PP~) 

EEC 

(PP~) 

Rainbow trout 

Bluegill sunfish 

Sea lamprey 0.025 0.049 0.5' 0.035 0.71" 

Carp 

(Qprinus calpio) 

Green sunfish 

(Lepomis cyanellus) 0.025 0.170 0.15** 0.035 0.50' 

* Acute hlgh risk, acute restricted use and endangered species LOCs exceeded. ** Acute restricted use and endangered species LOCs exceeded. *** Endangered species LOCs exceeded 

Acute risk quotients for a mixture of TFM and niclosamide were calculated (Table 7). The RQ for 

the minimum predicted treatment concentration range from 0.60 to 1.13 while the RQ for the 

maximum predicted treatment concentration range from 1.9 to 3.57. An analysis of the results 

indicate that aquatic acute high risk, restricted use, and endangered species levels of concern are 

exceeded for freshwater fish at typical use rates of TFM and niclosamide which result in 

environmental concentrations of 0.7 to 2.2 ppm. A comparison between the RQ for TFM and the 

mixture of TFM and niclosamide indicate that the mixture results in an additive affect that poses 

more risk to fish from the mixture than TFM alone. 

Table 7. Acute risk quotients for a mixture (98:2 by weight) of TFM and niclosamide for fish. 

Species LC,, (PP~) EEC(PP~) RQ EEC (PP~) RQ 

Channel catfish 0.615 

Brown Trout 0.98 0.7 0.71' 2.2 2.2" 

Yellow perch 0.9 0.7 0.78" 2.2 2.4' 

Rainbow trout 1.16 0.7 0.60' 2.2 1.90' 

Acute high risk, acute restricted use and endangered species LOCs exceeded. 

The rainbow trout RQ, based on the 96-hour LC,, values derived at various pH, range from 

0.135 to 0.958 for the minimum EEC of 25 ppb, while the RQ for the maximum EEC of 35 ppb 

range from 0.189 to 1.40 (Table 8). At both the minimum and maximum EEC, the acute high risk 

LOC will be exceeded for rainbow trout in streams with pH up to 7.5. 
Table 8. Summary of risk quotients to the rainbow trout, Oncorhynchus mykiss, based on pH 

(Bills and Marking, 1976). 

PH 96-hr LC,, EEC RQ EEC RQ 

6 5 0 0261 0 025 0 958' 0.035 1.40' 

9.5 0.185 0.025 0.135'" 0.035 0.189** 

"Acute high risk, acute restricted use and endangered species LOCs exceeded. 

"Acute restricted use and endangered species LOCs exceeded. 

Aquatic Invertebrates 

The RQ for aquatic invertebrates at the minimum EEC of 25 ppb range from 0.001 to 0.74, 

while the RQ for the maximum EEC of 35 ppm range from 0.001 to 1.02 (Table 9). Acute high risk 

LOCs are exceeded for aquatic earthworms and flatworms (Turbellaria). Endangered species LOCs 

are exceeded for 64%of the species tested at both estimated treatment levels of 25 and 35 ppm 

Table 9. Acute risk quotients of niclosamide for aquatic invertebrates. 

96-hour 

Species EEC 

EC50 (PP~) RQ EEC (PP~) RQ 

Waterflea 0.2 pprn 0.025 0.125" 0.035 0.175'' 

Scud 

(Gammarus pseudolimnaeus) 

Snails 

(Physa sp.) 

Snails 

(Pleurocera sp.) 

Glass shrimp 

(Palaemonetes kadiakensis) 

Clam 

(Eliptio dilatatus) 

Crayfish 

(Orconectes nais) 

Midge 

(Chironomus plumosus) 

Leeches 

(Erpobdellidae) 

Aquatic earthworms 

(Tubifex tubifex) 

2.4 ppm 

0.106 ppm 

0.36 ppm 

10 PPm 

0.382 ppm 

25 PPm 

1.5 ppm 

0.42 ppm 

0.034 

Turbellarian 

(Dugesia tigrina) 0.048 0.025 0.52' 0.035 0.73' 

' Acute high risk, acute restricted use and endangered species LOCs exceeded. 

*' Acute restricted use and endangered species LOCs exceeded 

""Endangered species LOCs exceeded 
The RQ for aquatic invertebrates, for the mixture of TFM and niclosamide, at the minimum 

predicted concentration of 0.7 ppm, range from 0.03 to 0.46, while the RQs for the maximum 

predicted treatment concentration of 2.2 ppm range from 0.08 to 1.47 (Table 10). Acute restricted 

use and endangered species LOC are exceeded for aquatic invertebrates at minimum predicted 

treatment concentrations for waters of pH 7.2 - 7.6. A comparison between the RQs for TFM and 

the mixture of TFM and Niclosamide indicate that the mixture results in an additive affect that is 

more toxic to aquatic invertebrates than TFM alone. The data suggest that Tubellariums (aquatic 

worms) are at the greatest risk from the use of mixture of TFM and niclosamide to control the sea 

lamprey. Data also suggest however, that while the TFMIniclosamide mixture results in higher 

toxicity to aquatic invertebrates, the increase in toxicity is not proportional to that of the lamprey. 

In other words, lampreys undergo a marked increase in toxicity to the TFMIniclosamide compared 

to the relatively small increase in sensitivity exhibited by aquatic invertebrates. This differential 

toxicity between sea lamprey larvae and nontarget aquatic invertebrates as a result of using the 

TFMIniclosamide mix is exploited to enhance mortality of ammocoetes while reducing effects on 

nontargets (pers. comm. Terry Bills, Fishery Biologist, U.S. Geological Survey 1999). 

Table 10. Acute riskquotients of a mixture (98:2 by weight) of TFM and niclosamide for aquatic invertebrates. 

Species LC5, (PP~) EEC RQ EEC (PP~) RQ 

Tubellarium 1.5 0.7 0.46'* 2.2 1.47' 

Amphipoda 

(G. psuedolinneaus) 

Diptera 

(Simulium sp.) 

Gastropoda 1.93 0.7 0.36*' 2.2 1.13' 

(Physa SP) 

'Acute high risk, acute restricted use and endangered species LOCs exceeded. *, Acute restricted use and endangered species LOCs exceeded. 

Exposure and Risk to Nontarget Aquatic Plants 

The RQ for aquatic plants, at the minimum EEC of 25 ppb, range from less than 0.01 to 

0.61, while the RQ for the maximum EEC of 35 ppb range from liess than 0.01 to 0.85 (Table 11). 

No acute levels of concern were exceeded. 
Table 11. Risk Quotients (RQ) for nontarget aquatic plants exposed to niclosamide. 

Species EC50 EEC RQ EEC 

(PP~) (PP~) (PP~) RQ 

Diatoms 

Ankistrodesmus falcatus 0.103 0.025 0.243 0.035 0.34 

Scenedesmus quadricauda 0.130 0.025 0.192 0.035 0.27 

--- Phaeoda3lurn ---- tricornuturn - - 0,043 - 0.E- - - 2.58 - -- -0.035- -- - 0.81 - 

Green Algae 

Skeletonema costaturn 71 0.025 < 0.01 0.035 ~0.01 

Arnphiprora paludosa 1,450 0.025 <0.01 0.035 <0.01 

Phaeodactylurn tricornuturn 0.041 0.025 0.61 0.035 0.85