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Environmental Fate and Ecological Risk Assessment

for the Registration Review of Picaridin

1-piperidinecarboxylic acid 2-(2-hydroxyethyl)-1-methylpropylester

(Picaridin, CAS 119515-38-7)

Prepared by:

Brian Montague, Fishery Biologist

Gabe Rothman., Environmental Scientist

U. S. Environmental Protection Agency

Office of Pesticide Programs

Environmental Fate and Effects Division

Environmental Risk Branch IV

1200 Pennsylvania Ave., NW

Mail Code 7507P

Washington, DC 20460

Reviewed by:

Al Vaughan, RAPL

Justin Housenger, Biologist

Michael Barrett, Senior Chemist

Mah Shamim, Branch Chief
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Table of Contents

1. Executive Summary ................................................................................................................... 4

1.1 Nature of Chemical Stressor................................................................................................ 4

1.2 Potential Risks to Non-target Organisms......................................................................... 4

1.3 Conclusions - Exposure Characterization ........................................................................ 5

1.4 Conclusions - Effects Characterization............................................................................ 6

2. Use Characterization .................................................................................................................. 6

2.1 Nature of the Chemical Stressor....................................................................................... 6

2.2 Overview of Pesticide Usage ........................................................................................... 7

3. Environmental Fate and Transport Characterization.................................................................. 7

3.1 Transport in the Environment .......................................................................................... 8

3.2 Degradation in the Environment ...................................................................................... 9

4. Ecological Toxicity Characterization......................................................................................... 9

4.1 Effects to Aquatic Organisms ........................................................................................ 10

4.2 Effects to Terrestrial Organisms .................................................................................... 11

4.3 Degradate toxicity .......................................................................................................... 11

4.4 ECOTOX Open Literature ............................................................................................. 11

5. Problem Formulation................................................................................................................ 12

5.1 Conclusions from Previous Risk Assessments .............................................................. 12

5.2 Conceptual Model .......................................................................................................... 12

5.3 Analysis Plan.................................................................................................................. 13

5.4 Endangered Species Assessment.................................................................................... 16

5.5 Endocrine Disruptor Screening Program ....................................................................... 16

6. Exposure Analysis.................................................................................................................... 17

6.1 Estimated Surface Water Concentrations....................................................................... 17

6.2 Monitoring Data for Picaridin........................................................................................ 20

6.3 Terrestrial Exposure Analysis........................................................................................ 20

7. Risk Characterization ............................................................................................................... 20

7.1 Risk Estimation .............................................................................................................. 20

7.2 Risk Description............................................................................................................. 22

7.3 Uncertainties, Limitations, and Data Gaps..................................................................... 22

8. Federally Threatened and Endangered (Listed) Species Concerns.......................................... 23

9. References................................................................................................................................ 25
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1. Executive Summary

1.1 Nature of Chemical Stressor

Registration review is being performed for the insect repellent picaridin (2-(2-Hydroxyethyl)-1-

piperidinecarboxylic acid 1-methylpropyl ester). This document contains the problem formulation 

as well as the environmental fate, ecological risk, and endangered species assessments for its 

registered uses. This risk assessment is intended to identify ecological risks associated with the 

registered uses of picaridin. 

Picaridin is a broad spectrum insect and tick repellent used on the human body and clothing (skin, 

hair, clothing, footwear, shoes, and headgear/caps). Picaridin is used to repel biting flies, 

mosquitoes, chiggers, ticks, and fleas. Picaridin was first registered in the United States in 2000. 

Picaridin is not registered for any agricultural, non-agricultural, or greenhouse applications nor has 

it been registered as a pesticide before this time. It is also not registered for any home, residential, 

or indoor applications nor is it a known byproduct of any kind from industrial manufacturing or 

refining processes. Picaridin is applied to human skin and hair, worn clothing, footwear, and 

headgear, or horse skin. 

Currently, picaridin is formulated as a pressurized spray (aerosol), as impregnated materials (e.g. 

towelettes, roll-on), and as a ready-to-use solution (non aerosol pump spray, liquid, cream, lotion, 

or foam). Picaridin concentrations in end-use products range from 5 to 20% a.i. 

1.2 Potential Risks to Non-target Organisms

The results of this assessment on currently registered picaridin uses indicate that there are no acute 

RQs that exceed the LOC to listed or non-listed non-target organisms (Table 1.1). Additionally, 

the Agency has determined that there is no habitat modification of any designated critical habitat 

for listed species from the current registered uses of picaridin.

Conclusions regarding aquatic organisms are based on lack of RQs that exceed the acute LOC in 

the risk estimation. Conclusions regarding terrestrial organisms and plants are based on the lack 

of a complete exposure pathway. Exposure in terrestrial habitats would be limited to human skin, 

clothing, and shoes, as well as horse skin and hair. Products formulated as lotions or impregnated 

wipes would be applied directly to the human skin. Many other product labels specify 

recommended spray distances of less than 10 inches from the intended application sites (human 

skin, clothing, and shoes, as well as horse skin and hair). Exposure to listed species is not expected 

because they would not likely come in close contact with humans or domestic horses (i.e., the 

registered use sites). Even if a non-target organism were to come into contact with picaridin from 

over-spray, exposure levels would be expected to be low. Therefore, given its low toxicity profile, 

effects to non-target organisms would not be anticipated to exceed concern levels even if exposure 

occurred. 
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Table 1.1. Potential Effects to Federally Listed Taxa Associated with Direct or Indirect 

Effects from the Currently Registered Uses of Picaridin

Listed Taxon Direct Effects Indirect Effects

Terrestrial and semi-aquatic plants - monocots

No No

Terrestrial and semi-aquatic plants - dicots

Birds

Terrestrial-phase amphibians and reptiles

Mammals

Terrestrial invertebrates

Aquatic nonvascular plants

Aquatic vascular plants

Freshwater fish

Aquatic-phase amphibians

Freshwater invertebrates

Marine/estuarine fish

Marine/estuarine invertebrates

1.3 Conclusions - Exposure Characterization 

Picaridin possesses soil-water partition coefficient values (estimated Koc = 64 - 389 mL/g) that

are consistent with pesticides which are known to remain in the water column to a certain extent. 

Therefore, picaridin can remain in the water column to a large extent once washed off from treated 

human skin which may be in contact within water bodies. In surface waters, picaridin is expected 

to degrade to some extent as evident from a degradation laboratory study using water monitoring 

samples in a waste water stream (Knepper, 2004). The laboratory study analysis indicates that 

picaridin degrades to the principle degradate picaridin carboxylic acid, which occurs mainly 

through multiple oxidation processes. Picaridin is lipophilic and therefore has the potential to 

partition to fish tissue to some extent. However, substantial bioaccumulation of residues is not 

expected considering the nature of applications with picaridin to mainly human subjects, 

indications of its high depuration based on low BCF values, and low aquatic concentrations 

expected in the environment. Picaridin’s low toxicity and low persistence further suggests that 

any small level of bioaccumulation which occurs would have a low impact on aquatic organisms.

Aquatic exposure estimates for picaridin are based on washoff after application to skin or clothing 

or to horses. Upper-bound aquatic estimated exposure concentrations (EECs) ranged from 0.0017 

to 0.081 mg a.i./L (17 to 81 g a.i./L) depending on the number of individuals entering a 

20,000,000 L water body (standard farm pond). Surface water monitoring data in influent 

wastewater streams varied between 0.6 – 1.4 g/L (Knepper, 2004). The upper-bound EEC of 81 

g/L was between one and two orders of magnitude higher than the highest monitoring 

concentration.

Exposure to terrestrial non-target organisms and plants is expected to be inconsequential based on 

the labeled use patterns.
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1.4 Conclusions - Effects Characterization 

The agency has reviewed a reduced data set for picaridin consisting of one subacute dietary

toxicity study with an avian species and 3 acute toxicity studies with a fish, aquatic invertebrate, 

and freshwater algae.

Aquatic Organisms

Technical grade picaridin is classified as practically non-toxic to fish (which serve as surrogates 

for aquatic-phase amphibians). The 96 hour LC50 for Rainbow trout (Oncorhynchus mykiss) was 

determined to be 173 mg a.i/L (MRID 44408740). Picaridin is practically non-toxic to aquatic 

invertebrates. Toxicity to aquatic invertebrates was observed to be low for the Water flea,

Daphnia magna, with a 48 hour EC50 and NOAEC > 103 mg ai/L (MRID 44408741). Effect

levels to the freshwater green algae, Scenedesmus subspicatus was observed to be a 72 hour EC50

of 87 mg ai/L and a NOAEC of 54.8 mg ai/L (MRID 44408742). 

Toxicity data were not available for evaluation of picaridin chronic exposure to freshwater fish 

and invertebrates. No toxicity data were available for estuarine/marine fish and invertebrates or 

for vascular aquatic plants. 

Terrestrial Organisms

Picaridin is practically non toxic to birds on a subacute dietary exposure basis. In a 5 day dietary 

exposure to Bobwhite quail, Colinus virginianus no mortality or adverse behavioral effects were 

observed at 5000 mg ai/kg –diet treatment group. (MRID 44408739).

Picaridin is slightly toxic (Category III) to mammals on an acute oral exposure basis with LD50’s

of 2236 and 4743 mg ai/Kg for male rat (fasted and non-fasted, respectively, MRID 44408705). 

In a 14 week feeding study the subchronic LOAEL was determined to be 1033 mg/Kg/day for 

laboratory rats based on decreased body weight in males and females and effects to male kidneys 

including increased weight and nephropathy. No developmental toxicity was observed at up to 

400 mg/Kg/day in laboratory rats (MRID 45387902).

No toxicity data were available for non-target insects or terrestrial plants.

2. Use Characterization

2.1 Nature of the Chemical Stressor

Picaridin belongs to the chemical class of piperidines (USEPA, 2005). The specific mechanism of 

action of picaridin has not been determined. However, recent mosquito behavior research suggests 

that repellency is due to direct detection of picaridin by the olfactory receptor neurons (ORNs) in 

the antenna, which appears to prevent the mosquito from recognizing the host (Klun, et al., 2006). 

Other research has suggested that mosquito response to picaridin varies by individual mosquitos 

and mosquito species (Amer and Mehlhorn, 2006). The efficacy of the repellency of picaridin was 

reduced in some individual mosquitos where the maxillary bulbs did not exist. Furthermore, 
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Anopheles stephensi mosquitoes appeared to sense picaridin while also maintaining the ability to 

recognize the host using different organs (Amer and Mehlhorn, 2006). Direct exposure to picaridin 

did not kill or alter the behavior of mosquitoes (Licciardi, 2006).

2.2 Overview of Pesticide Usage

There are a total of 28 active registrations with picaridin. All products possess the single active 

ingredient (a.i.). Most are registered under the trade name of “Cutter” insect repellents and sold 

by the Spectrum Division of United Industries, Inc. The percent a.i. in the ready-to-use products 

ranges from 5 to 20%. Picaridin is applied on the human body and clothing (skin, hair, clothing, 

footwear, shoes, and headgear/caps). Picaridin is used to repel biting flies, mosquitoes, chiggers, 

ticks, and fleas. Picaridin may also be applied to horse skin. The approved pests associated with 

picaridin uses are: biting flies, mosquitoes, chiggers, ticks, and fleas. The physical forms of the 

registered products include ready-to-use solutions, impregnated substances on towelettes, aerosols 

sprays, and other pumps and sprays. The following list provides a summary of all available 

formulations for picaridin, all of which have identical uses:

 Pumps and sprays: 5% and 7% a.i.

 Aerosol sprays: 10%, 12%, 15%, and 20% a.i.

 Impregnated substance: 5.75%, 10%, 16%, and 20% a.i.

 Ready-to-use solutions: 5%, 10%, 15%, and 20% a.i.

 Technical grade substance: 98.7% a.i.

A more detailed table of picaridin products is provided in Appendix C.

3. Environmental Fate and Transport Characterization

Picaridin is an all-purpose insect repellent in the piperidine chemical class. It is a racemic mixture 

of two diastereoisomers that occur in roughly equal proportions (WHO, 2004). Some piperidine 

compounds are indigenous to extracts from pepper plants. However, picaridin is in itself a 

synthetic compound (Moore and Debboun, 2007). The technical substance of picaridin is a nearly 

colorless and odorless liquid (EPA, 2005). It is relatively stable and highly soluble in water (WHO, 

2004). The physicochemical characteristics associated with picaridin are summarized in Table 

3.1.

Table 3.1. Physicochemical properties of picaridin .

Parameter Value Citation

Structure EpiSuite

Molecular formula C12H23NO3 MRID 46662001
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Table 3.1. Physicochemical properties of picaridin .

Parameter Value Citation

Molecular weight 229.3 g/mol MRID 46662001

CAS Number: 119515-38-7

CAS Name: 2-(2-Hydroxyethyl)-1-piperidinecarboxylic acid 1-methylpropyl ester

Density 0.909 g/mL MRID 46662001

Water solubility 8.2 x 103 mg/L at 20°C, pH 4 - 9

196 mg/L at 25°C, pH7

WHO, 2004

EpiSuite, WSKOW v.1.41

Vapor pressure 4.40 x 10-4torr@ 25°C WHO, 2004

Henry’s law constant 3.0 x 10-11 atm-m3/mol @ 25°C SRC Database1

Soil sorption coefficient (Koc)

64.43 mL/g

389 mL/g

EpiSuite, KOCWIN v.2.00

SRC Database1

Octanol-water partition coefficient 

(log Kow)

4.94 MRID 46662001

Bioconcentration factor (BCF) in 

fish 23.05 L/kg EpiSuite, BCFBAF v.3.01

1 Available on-line: http://www.srcinc.com/what-we-do/environmental/scientific-databases.html.

3.1 Transport in the Environment

Picaridin is expected to remain dissolved in water given its high solubility value of 196 mg/L. 

Furthermore, picaridin’s Henry’s Law Constant value of 3.0 x 10-11 atm-m3/mol indicates that it 

will not volatilize under moist conditions. Under dry conditions, picaridin is moderately volatile 

given its vapor pressure value of 4.40 x 10-4torr. However, volatilization of picaridin is not 

expected to occur to a large extent.

Once picaridin is washed off from treated human or horse skin, picaridin is expected to remain in 

the water column to a ceratin extent (estimated Koc values between 64 -and 389 mL/g). However, 

picaridin’s Kow value of 4.94 also suggests that picaridin is lipophilic and may tend to 

bioconcentrate in fish tissue to some extent. However, the bioconcentration factor of picaridin is 

relatively small suggesting that a notable amount of picaridin may exist in water under steady state 

conditions surrounding aquatic animals considering processes such as depuration. Furthermore, 

upper-bound EECs in water are expected to be very low, as shown in Table 6.2 of Section 6.1. 

Low monitoring concentrations of picaridin, shown in Section 6.2, in stream water confirm this. 

Therefore, bioaccumulation is not expected to be prevalent for picaridin considering the low

expected concentrations indicated by its use pattern and low BCF value.
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3.2 Degradation in the Environment

The only environmental fate study submitted to the Agency is the hydrolysis study (MRID No. 

44408743). The study demonstrated that picaridin is stable to hydrolysis in solutions initially 

buffered to pH 5, 7, and 9 over 30 days. However, there is evidence that picaridin can degrade in 

the environment. Extracts from monitoring data in effluent water from a wastewater treatment 

plant in Germany indicates that picaridin degrades to the principle degradate picaridin carboxylic 

acid in the environment (Knepper, 2004), and its chemical structure shown in Figure 1 below . 

The chemical degradation model Catabol 301c1indicates that this process occurs due to multiple 

oxidation processes which is a known process which may occur naturally in the environment. 

Therefore, the results from Catabol 301c demonstrate that it is plausible for picaridin carboxylic 

acid to form without any influence from wastewater treatment, although its formation as observed 

in the Knepper study may have been enhanced by the wastewater plant. The Catabol 301c analysis

and predicted environmental degradation pathway of picaridin is shown in Appendix D of this 

document.

Figure 1. Chemical structure of picaridin carboxylic acid (molecular weight = 242 g/mol).

4. Ecological Toxicity Characterization

In screening-level ecological risk assessments, effects characterization describes the types of 

effects a pesticide can have on aquatic and terrestrial organisms. . Birds are used as surrogates 

for reptiles and terrestrial-phase amphibians and freshwater fish are used as surrogates for aquaticphase amphibians. This characterization is based on the registrant-submitted toxicity data for 

birds, mammals, freshwater fish, aquatic invertebrates and aquatic plants.

The assessment also evaluates the potential for picaridin to directly or indirectly affect listed 

species or modify designated critical habitat. Assessment endpoints may include direct toxic 

effects on the survival, reproduction, and growth of listed entities, as well as indirect effects, such 

as reduction of the prey base or modification of habitat. In addition, potential modification of 

critical habitat is assessed by evaluating effects to the primary constituent elements (PCEs), which 

are components of the critical habitat areas that provide essential life cycle needs of listed entities. 

The most sensitive endpoint for each taxon is used for risk estimation, which in the case of 

picaridin is from a single study for each taxon. This assessment, evaluated 5 taxa include 

 

1 The Catabol 301c model is publically available on-line at: http://oasis-lmc.org/products/models/environmentalfate-and-ecotoxicity/catabol-301c.aspx
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freshwater fish, a freshwater crustacean, birds, an aquatic non-vascular plant and mammals. Table 

4.1 provides a summary of the taxonomic groups, surrogate species tested, and results of studies

to characterize the potential acute ecological effects of Picaridin (no chronic toxicity studies are 

available). 

Table 4.1. Test Species Evaluated for Assessing Potential Ecological Effects of Picaridin 

and the Associated Acute Toxicity Classification.

Taxonomic 

Group

Tested Species 

and Study Type Toxicity Endpoint

Study MRID and 

Toxicity 

Classification

Birds1

Acute oral No avian oral toxicity data

Bobwhite quail 

(Colinus 

virginianus) Avian 

dietary

LC50 > 5000 mg ai/kg-diet

44408739

Practically non-toxic

acceptable

Avian reproduction

No data

Mammals

Laboratory rat 

(Rattus norvegicus) 

(acute oral)

LD50 = 2236 mg ai/kg-bw Category III3

Laboratory rat 

chronic LOAEL > 400 mg/Kg/Day

Insects Honey bee (Apis 

mellifera)

No data

Freshwater fish2

Rainbow trout 

(Oncorhynchus 

mykiss)

LC50 = 173 mg ai/L

NOAEC = 50 mg ai/L

44408740

practically non-toxic

acceptable

Freshwater 

invertebrates

Waterflea, 

Daphnia magna EC50 > 103 mg a.i./L

44408741

practically non-toxic

acceptable

Estuarine/marine 

fish

No data

Estuarine/marine 

invertebrates

No data

Terrestrial plants No data

Aquatic plants 

and algae

Green algae, 

Scendesmus 

subspicatus

72 hour EC50= 87.3 mg ai/L

NOAEC = 54.8 mg ai/L

44408742

Supplemental-72 hour 

study

1 Birds are considered surrogates for terrestrial-phase amphibians and reptiles.

2 Freshwater fish are considered surrogates for aquatic-phase amphibians.

3 Study classification made by Health Effects Division (HED).

4.1 Effects to Aquatic Organisms

Technical grade picaridin is classified as practically non-toxic to fish (which serve as surrogates 

for aquatic-phase amphibians) and practically non-toxic to aquatic freshwater invertebrates. 

Toxicity to aquatic algae was observed at concentrations 1000 times above any expected exposure 

levels. Toxicity data were not available for evaluation of picaridin chronic exposure to freshwater 

fish and invertebrates. No toxicity data were available for estuarine/marine fish and invertebrates 

or for vascular aquatic plants. 
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4.2 Effects to Terrestrial Organisms

Picaridin is practically non toxic to birds on a subacute dietary exposure basis and is practically 

non-toxic to mammals on an acute oral exposure basis. There was no chronic toxicity data were 

available for birds. The subacute avian dietary LC50 was greater than 5000 mg a.i/kg-diet .

Picaridin is slightly toxic to mammals on an acute oral exposure basis with a fasting LD50 of 2236

mg ai/Kg to 4743 mg ai/Kg for a non-fasting male rat.

In a 14 week feeding study the subchronic LOAEL was determined to be 1033 mg/Kg/day for 

laboratory rats based on decreased body weight in males and females and effects to male kidneys 

including increased weight and nephropathy. No developmental toxicity was observed at up to 

400 mg/Kg/day in laboratory rats.

No toxicity data were available for bees, non-target insects, or terrestrial plants. Given the 

repellency action of picaridin, it is likely that many terrestrial invertebrates would be repelled, and 

thus, not exposed for significant periods of time.

4.3 Degradate toxicity

Although the guideline hydrolysis for picaridin (MRID No. 44408743) indicates that picaridin is 

stable for up to 30 days, there is evidence that picaridin can degrade in the environment. Extracts 

from monitoring data in effluent water from a wastewater treatment plant in Germany indicates 

that picaridin degrades to the principle degradate picaridin carboxylic acid in the environment 

(Knepper, 2004). Most other known pipieridine compounds (e.g., paroxetine, methylphenidate, 

raloxifene, minoxidil, risperidone, and pethidine to name a few) are larger, more complex

compounds than picaridin, and some are not racemic mixtures. Therefore, little information is 

known on the fate and transport characteristics, toxicity, and the amount formed of picaridin 

carboxylic acid or other degradates from the picaridin parent material based on literature 

information related to picaridin or other piperidine compounds (SRC database)2. Given the lack 

of information on degradates, including their toxicity, any degradates will be presumed to have the 

same toxicity as the parent, and total toxic residues will assumed to be stable in the environment 

for exposure estimates.

4.4 ECOTOX Open Literature

Literature identified in the search of the publically available ECOTOX database resulted in one

citation for Picaridin (Appendix B). The cited aquatic toxicity study with an African Tilapia 

species did not provide endpoints that were more sensitive than the data that was submitted to the 

Agency. In addition, none of the aquatic data filled existing data gaps (e.g., chronic toxicity to 

freshwater fish and invertebrates, acute and chronic toxicity to estuarine/marine fish and 

invertebrate). 

 

2 Available on-line: http://www.srcinc.com/what-we-do/environmental/scientific-databases.html
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There were no studies located in ECOTOX for terrestrial wildlife. One efficacy study evaluating 

the toxicity of picaridin to mites was identified but the data are not toxicologically relevant for this 

risk assessment. .

5. Problem Formulation

The purpose of problem formulation is to provide the foundation for the environmental fate and 

ecological risk assessment for the registration review risk assessment for the insect repellant, 

picaridin. The problem formulation sets the objectives for the risk assessment, establishes a risk 

hypothesis and conceptual model depicting potential risk, and provides a plan for analyzing the 

data and characterizing the risk associated with the uses of picaridin (USEPA, 1998). 

5.1 Conclusions from Previous Risk Assessments

EFED has not conducted any ecological risk assessments for picaridin. Since picaridin was 

registered in 2000, it is a relatively new pesticide. Therefore, it was not evaluated under the 

Reregistration program.

5.2 Conceptual Model

Given the use and application of picaridin to human subjects and horse skin, the following 

describes conceivable exposure pathways to non-target organisms in the environment:

 Aquatic Exposure: Washoff of picaridin residues may occur with treated 

individuals entering water bodies as well as due to showering/bathing and laundry

cleaning activities. Therefore, related exposure of non-target aquatic plants and 

animals including federally-listed threatened and endangered species may occur.

 Terrestrial Exposure: Direct applications of picaridin to human skin and clothing, are 

not expected to result in significant exposure to non-target terrestrial plants and animals

including federally-listed threatened and endangered species. Exposure in terrestrial 

habitats would be limited to human skin, clothing, and shoes, as well as horse skin and 

hair. Products formulated as lotions or impregnated wipes would be applied directly to the 

human skin. Many other product labels specify recommended spray distances of less than 

10 inches from the intended application sites (human skin, clothing, and shoes, as well as 

horse skin and hair). However, movement off of treated subjects are not anticipated for 

picaridin in the terrestrial environment. Therefore, the amount of picaridin resulting from 

human or horse application in the terrestrial environment (air, ground, plants, or nontreated animals) is inconsequential. 
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5.3 Analysis Plan

In order to address the risk hypothesis, the potential for adverse effects on the environment is 

estimated. The use, environmental fate, and ecological effects of picaridin are characterized and 

integrated to assess the risks. This is accomplished using a risk quotient (ratio of exposure 

concentration to effects concentration) approach. Although risk is often defined as the likelihood 

and magnitude of adverse ecological effects, the risk quotient (RQ)-based approach does not 

provide a quantitative estimate of likelihood and/or magnitude of an adverse effect. The likelihood 

of effects to individual organisms from particular uses of picaridin has been estimated using the 

actual estimated risk quotient values.

5.3.1 Residues of Concern

The parent compound, picaridin, is the toxicant that will be assessed. Toxicity of picaridin isomers 

and degradates , including picaridin carboxylic acid, will be assumed to be equivalent to parent 

compound in the absence of data to suggest otherwise.

5.3.2 Evaluation of Multiple Active Ingredients, Mixtures and Formulated 

Products

The Agency does not routinely include in its risk assessments an evaluation of mixtures of active 

ingredients, either those mixtures of multiple active ingredients in product formulations or those 

in the applicator’s tank. In the case of the product formulations of active ingredients (that is, a 

registered product containing more than one active ingredient), each active ingredient is subject to 

an individual risk assessment for regulatory decision regarding the active ingredient on a particular 

use site. If effects data are available for a formulated product containing more than one active 

ingredient, they may be used qualitatively or quantitatively. 

5.3.3 Measures of Exposure 

The ecosystems potentially at risk are often extensive in scope; therefore, it may not be possible 

to identify specific ecosystems during the development of a nation-wide ecological risk 

assessment. 

Aquatic ecosystems potentially at risk from picaridin exposure include water bodies adjacent to, 

or downstream from, the water bodies that were entered by treated humans or horses. In order to 

estimate risks of picaridin exposures in aquatic environments, all exposure modeling and resulting 

risk conclusions will be based on maximum application rates and methods. Measures of aquatic 

exposure are typically based on models that predict estimated environmental concentrations 

(EECs) of picaridin such the Pesticide Root Zone Model coupled with the Exposure Analysis 

Modeling System (PRZM/EXAMS). However, because of the limited application methods 

(directly to human skin, clothing, shoes, and horse skin), the typical models used for exposure 

estimation (e.g., PRZM/EXAMS) will not be used in this assessment. 

Environmental exposure concentrations are calculated assuming that picaridin reaches surface 
Page 14 of 45

water directly via treated human subjects entering the water body, and that the entire application 

of picaridin is presumed to wash off and remain in the water column. Water concentrations in the 

standard pond will be calculated under the assumption that picaridin is released directly into the 

pond from 10 treated adults, 100 treated adults, or 10 treated horses. Another scenario where 50 

cans of the product are directly released into the pond will be evaluated. Application of the 

equivalent of 50 cans of product represents a highly unlikely, very conservative aquatic exposure 

scenario, as it is not expected that such a large number of treated individuals would enter a single 

1–hectare water body within a 24 hr period. The scenario is presented as a convenient measure to 

evaluate the plausibility of exposure levels approaching those that may cause concern for aquatic 

organisms. 

Because of the application method and limited scope of use sites for picaridin, terrestrial 

ecosystems potentially at risk could include the area in which treatment (application to human or 

horse) occurred. Exposure to non-target terrestrial organisms and plants is presumed negligible 

(Section 5.2) and will not be estimated.

5.3.4 Measures of Effect 

Measures of effect are obtained from a suite of registrant-submitted guideline studies that were 

conducted with a limited number of surrogate test species (Table 5.1). Toxicity data generated 

using surrogate test species, which are intended to be representative of broad taxonomic groups, 

are used to infer potential effects on a variety of species (receptors) included under these broader 

taxonomic groupings. Birds represent surrogates for terrestrial-phase amphibians and reptiles, and 

freshwater fish represent surrogates for aquatic-phase amphibians. No additional non-target 

ecotoxicity data on picaridin were located, based on a recent query of the open literature in the 

publically available version of the ECOTOX database (http://cfpub.epa.gov/ecotox/).

Table 5.2 lists the measures of environmental exposure and ecological effects used to assess the 

potential risks of picaridin to non-target organisms. Assessment endpoints represent the actual 

environmental value that is to be protected, defined by an ecological entity (species, community, 

or other entity) and its attribute or characteristics (USEPA, 1998). The attributes for each of 

these entities may include growth, survival, and reproduction.

Table 5.1. Measures of Exposure and Effect Used in Assessing Potential Risks 

Associated with the Registered Uses of Picaridin.

Assessment Endpoint

Surrogate Species and 

Measures of Ecological 

Effect1

Measures of Exposure

Aquatic Animals 

(Freshwater fish and 

invertebrates)2

Survival

Lowest tested LC50 or 

EC50

(acute toxicity test)

Estimated aquatic concentrations 

after treated individuals entered 

water body

Reproduction 

and Growth No data

Not calculated as no acute LOC 

exceedances and no chronic 

toxicity data available

Aquatic Animals 

(Estuarine/marine fish and 

invertebrates)2

Survival No data

Presumed concentrations in water 

equal or less than those estimated 

for small freshwater pond
Page 15 of 45

Table 5.1. Measures of Exposure and Effect Used in Assessing Potential Risks 

Associated with the Registered Uses of Picaridin.

Assessment Endpoint

Surrogate Species and 

Measures of Ecological 

Effect1

Measures of Exposure

Reproduction 

and Growth No data

Not calculated as there were no 

acute LOC exceedances and no 

chronic toxicity data available

Aquatic plants Growth

EC50 for Growth 

effects with Freshwater 

Algae

No vascular plant data 

available

Estimated aquatic concentrations 

after treated individuals entered 

water body

Birds3

Survival

Lowest acute LC50 (5 

day dietary exposure)

No LD50 oral data 

available

Not calculated as significant 

exposure is not expected

Reproduction 

and Growth No data

Mammals

Survival Lowest oral acute LD50 

Reproduction 

and Growth

Lowest NOAEC 

reproductive effects

(2-generation 

reproduction test)

Insects Survival No data Not calculated as significant 

exposure is not expected

Terrestrial plants Survival and 

growth No data Not calculated as significant exposure is not expected

1 The most sensitive species tested within taxonomic groups is used for screening-level risk assessments.

2 Freshwater fish are considered surrogates for aquatic-phase amphibians.

3 Birds are considered surrogates for terrestrial-phase amphibians and reptiles.

5.3.5 Integration of Exposure and Effects

Exposure and toxicity data are integrated in order to evaluate the risks of adverse ecological effects 

on non-target species. For the screening-level risk assessment of picaridin, the deterministic risk 

quotient (RQ) method is used to compare estimated exposure concentrations with measured 

toxicity values. The RQ method involves dividing point estimates of environmental concentrations 

by acute and chronic toxicity values. The resulting unitless RQs are then compared to the 

Agency’s Levels of Concern (LOC) (Table 5.2). These criteria are used to indicate when 

applications of picaridin, as directed on the proposed labels, have the potential to cause adverse 

effects to listed and non-listed non-target organisms.

Table 5.2. Agency Acute Risk Quotient (RQ) Metrics and Levels of Concern (LOC) for 

Aquatic Animals (fish and invertebrates)

RISK CLASS RISK DESCRIPTION RQ LOC

Acute Potential for effects to non-listed animals from acute 

exposures

Peak EEC/LC50

1 0.5
Page 16 of 45

Table 5.2. Agency Acute Risk Quotient (RQ) Metrics and Levels of Concern (LOC) for 

Aquatic Animals (fish and invertebrates)

RISK CLASS RISK DESCRIPTION RQ LOC

Acute Restricted Use

Potential for effects to animals from acute exposures

Risks may be mitigated through restricted use 

classification

Peak EEC/LC50

1 0.1

Acute Listed Species Listed species may be potentially affected by acute 

exposures

Peak EEC/LC50

1 0.05

1 LC50 or EC50.

5.4 Endangered Species Assessment

Consistent with the Agency’s responsibility under the Endangered Species Act (ESA), the Agency 

evaluates risks to Federally-listed threatened and/or endangered (listed) species from registered 

uses of picaridin.

The assessment of effects associated with the registration of picaridin is based on an action area. 

The action area is considered to be the area directly or indirectly affected by the federal action, as 

indicated by the exceedance of Agency LOCs used to evaluate direct or indirect effects. The action 

area is defined using the results of the risk assessment to establish boundaries for that action area 

with the understanding that exposures below the Agency’s defined LOCs constitute a no-effect 

threshold. For the purposes of this assessment, attention will be focused on the footprint of the 

action (i.e., the area where picardin application occurs), plus all areas where offsite transport may 

result in potential exposure that exceeds the Agency’s LOCs. Specific measures of ecological 

effect that define the action area for listed species include any direct and indirect effects and/or 

potential modification of its critical habitat, including reduction in survival, growth, and 

reproduction as well as the full suite of sub-lethal effects available in the effects literature. 

Therefore, the action area extends to a point where environmental exposures are below any 

measured lethal or sub-lethal effect threshold for any biological entity at the whole organism, 

organ, tissue, and/or cellular level of organization. In situations where it is not possible to 

determine the threshold for an observed effect, the action area is not spatially limited and is 

assumed to be the entire United States. 

5.5 Endocrine Disruptor Screening Program

As required by FIFRA and FFDCA, EPA reviews numerous studies to assess potential adverse 

outcomes from exposure to chemicals. Collectively, these studies include acute, subchronic and 

chronic toxicity, including assessments of carcinogenicity, neurotoxicity, developmental, 

reproductive, and general or systemic toxicity. These studies include endpoints which may be 

susceptible to endocrine influence, including effects on endocrine target organ histopathology, 

organ weights, estrus cyclicity, sexual maturation, fertility, pregnancy rates, reproductive loss, 

and sex ratios in offspring. For ecological hazard assessments, EPA evaluates acute tests and 

chronic studies that assess growth, developmental and reproductive effects in different 
Page 17 of 45

taxonomic groups. Picaridin is subject to the endocrine screening part of the Endocrine 

Disruptor Screening Program (EDSP). 

EPA has developed the EDSP to determine whether certain substances (including pesticide 

active and other ingredients) may have an effect in humans or wildlife similar to an effect 

produced by a “naturally occurring estrogen, or other such endocrine effects as the Administrator 

may designate.” The EDSP employs a two-tiered approach to making the statutorily required 

determinations. Tier 1 consists of a battery of 11 screening assays to identify the potential of a 

chemical substance to interact with the estrogen, androgen, or thyroid (E, A, or T) hormonal 

systems. Chemicals that go through Tier 1 screening and are found to have the potential to 

interact with E, A, or T hormonal systems will proceed to the next stage of the EDSP where EPA 

will determine which, if any, of the Tier 2 tests are necessary based on the available data. Tier 2 

testing is designed to identify any adverse endocrine-related effects caused by the substance, and 

establish a dose-response relationship between the dose and the E, A, or T effect. 

Under FFDCA section 408(p), the Agency must screen all pesticide chemicals. Between 

October 2009 and February 2010, EPA issued test orders/data call-ins for the first group of 67 

chemicals, which contains 58 pesticide active ingredients and 9 inert ingredients. A second list 

of chemicals identified for EDSP screening was published on June 14, 20133and includes some 

pesticides scheduled for registration review and chemicals found in water. Neither of these lists 

should be construed as a list of known or likely endocrine disruptors. 

Picaridin is not among the group of 58 pesticide active ingredients receiving EDSP test orders. 

For information on the status of the orders issued under the EDSP for each chemical, please visit 

our website at http://www.epa.gov/endo/ and click on the "Status of EDSP Orders/DCIs" in the 

Highlights Box. Additional information on the EDSP, including the policies and procedures, the 

list of 67 chemicals, the test guidelines and the Tier 1 screening battery, can also be found at this 

website.

6. Exposure Analysis

6.1 Estimated Surface Water Concentrations

In order to estimate risks of picaridin exposures in aquatic environments, all exposure modeling 

and resulting risk conclusions will be based on maximum application rates and methods. Measures 

of aquatic exposure are typically based on models that predict estimated environmental 

concentrations (EECs) of picaridin such the Pesticide Root Zone Model coupled with the Exposure 

Analysis Modeling System (PRZM/EXAMS). However, because use is restricted to direct 

application to human skin, clothing, shoes, and horse skin, the typical models (e.g., 

PRZM/EXAMS) used for exposure estimation will not be used in this assessment. 

Aquatic exposure could be expected via two routes: (1) washoff from treated skin and clothing 

when people enter water bodies and (2) washoff from treated skin and clothing when people bathe 

 

3 See http://www.regulations.gov/#!documentDetail;D=EPA-HQ-OPPT-2009-0477-0074 for the final second list of 

chemicals.
Page 18 of 45

or launder clothing. However, only the aquatic exposure scenario resulting from treated humans 

and horses swimming in water bodies (first scenario above) are expected to account for peak and 

high-end EECs and would be protective of any potential “down-the-drain” type of exposure 

scenario associated with laundering or showering. Therefore, only the direct application scenarios 

will be evaluated and presented in this assessment. 

End-use products for humans and horses containing the highest quantity of picaridin in single sale 

containers will be evaluated for potential aquatic exposure. In general, picaridin products such as 

ready-to-use solutions, pumps, and aerosol sprays are sold in cans containing up to 6 fl. oz. of 

product containing up to 20% picaridin, or the equivalent of 1.2 fl. oz. or 32,255 mg of picaridin

per can4. In addition, fifty 6 fl. oz. cans of repellant contains the same amount of picaridin as 5,940 

picaridin towelettes impregnated with picaridin (330 packs of the product containing 18 

towelettes).

The standard scenarios used for ecological pesticide assessments assume application to a 10-

hectare agricultural field that drains into an adjacent 1-hectare water body that is 2 meters deep 

(20,000 m3volume equivalent to 20,000,000 L) with no outlet. Upper-bound picaridin water 

concentrations in the standard pond will be calculated assuming all of picaridin directly washes 

off into the water body given four scenarios. Scenario 1 assumes that 10 treated adults enter the 

pond. Scenario 2 assumes that 100 treated adults enter the pond. Scenario 3 assumes that 10 

treated horses enter the water body on a single day. Scenario 4 assumes that the entire contents 

of 50 cans or 330 towelette packs of the product (both possessing an equivalent of 32,255 mg of 

picaridin) are released to the pond. Application of the equivalent to 50 cans or 330 towelette packs

of product directly to the water body represents a highly unlikely, very conservative aquatic 

exposure scenario, as it is not expected that such a large number of treated individuals would enter 

a single 1–hectare water body within a 24 hr period. Picaridin application to ten horses also 

represents a high exposure scenario for the horse use pattern.

The Standard Operating Procedures for Residential Pesticide Exposure Assessment developed by 

the Health Effects Division (HED) provide methods for assessment for pesticide repellants 

(citation: http://www.epa.gov/pesticides/science/residential-exposure-sop.html#sops). Exposure 

assessment methods in this document include scenarios reflecting individuals who purchase 

pesticides and complete their own applications,such as adult and child application rate calculations

for insect repellants. Of the different available application methods and concentrations of picaridin 

in the individual products, pump sprays and aerosol sprays provide the highest application rates 

per individual. HED’s methodology determines an applied dose (mg a.i./kg-day) as well as an 

absorbed dose (mg a.i./kg-day); however for the purposes of this aquatic exposure estimation, the 

applied dose will be used and converted to a total daily dose per individual using an average adult 

body weight of 80 kg:

D = ARF * FAI * ET * AppF * SA/BW * FBody * BW

where:

D = dose (mg ai/individual-day);

 

4 32,255 mg of picaridin per can = 6 fl oz. of product/can x 20% picaridin (% a.i.) x 29.57 fl oz./mL (conversion 

factor) x 0.909 g/mL (density of picaridin) x 1,000 mg/g (conversion factor)
Page 19 of 45

ARF = formulation-specific application rate (mg product/cm2skin);

FAI = product-specific fraction of active ingredient (mg ai/mg product);

ET = exposure time (hours/day);

AppF = application frequency (applications/hour);

SA/BW = total body surface area to body weight ratio (cm2skin/kg);

FBody = fraction of body exposed (fraction exposed/application);

BW = 80 kilograms/individual.

For adult human applications, ARF, ET, AppF, SA/BW, FBody, and BW were determined using 

default values from HED’s SOP. For horses, the SA/BW and BW values were 100 cm2/kg and 500 

kg, respectively (citation: http://www.dpi.vic.gov.au/agriculture/animals-andlivestock/horses/management/feed-budgets-for-horses).

The contribution to the exposure created from individual treated adult human and horse subjects 

entering the water body in scenarios 1, 2, or 3 described above is shown in Table 6.1. The total 

bulk upper-bound acute estimated exposure concentrations (EECs) in water bodies resulting from 

picaridin treatments and resulting exposure described in scenarios 1, 2, 3, and 4 described above 

are shown in Table 6.2.

Table 6.1. Calculations for determining mg a.i./individual/day for scenarios 1, 2 or 3.

Applied 

Subject

Amount 

of ai in 

product 

(mg ai/mg 

product)

Formulationspecific AR 

(mg 

product/cm2

skin)

Fraction 

Body 

Exposed

Exposure 

Duration

(days)

Application 

Frequency

(#/hour)

SA to BW 

Ratio 

(cm2/kg) 

Exposure 

(mg a.i./kgday)a

Exposure 

(mg a.i./

individual/

day)b

Human

0.20 1.10 0.75 3.7 0.25

280 42.7 3,418.8

Horse 100 15.3 7,631.3

a Exposure calculated by multiplying the values in the preceding six columns (see Standard Operating Procedures 

for Residential Pesticide Exposure Assessment at http://www.epa.gov/pesticides/science/residential-exposuresop.html#sops for details). 

b

Individual exposure calculated by multiplying estimated body weight (80 kg for adult humans and 500 kg for 

horses) by exposure (mg a.i./kg-day) from the preceding column.

Table 6.2. Upper-bound aquatic exposure EECs for picaridin applications (mg a.i./L).

Release Scenario and Description

Exposure 

(mg a.i./

individual/

day)

Total Picaridin Mass 

Washoff

(mg)

Bulk Acute

Picaridin Pond 

EEC

(mg/L)

a

Scenario 1 - 10 treated adults to water body

3,418.8

34,188 0.0017

Scenario 2 - 100 treated adults to water body 341,880 0.017

Scenario 3 - 10 treated horses to water bodyb 7,631.3b 76,313b 0.0038

Scenario 4 - 50 cans product or 330 packs of 

towelettes impregnated with 

picaridin released to water body,c,d

N/A 1,612,748c,d 0.081

a Pond volume of 20,000,000 L.

b Calculated using same approach as for adult humans except surface area to body weight ratio was 100 cm2

/kg and 

body weight was 500 kg (http://www.dpi.vic.gov.au/agriculture/animals-and-livestock/horses/management/feedbudgets-for-horses).
Page 20 of 45

c Calculated based on 50, 6 fl oz. cans of product filled with end use product composed of 20% picaridin [6 fl oz. 

of product/can x 20% picaridin (% a.i.) x 29.57 fl oz./mL (conversion factor) x 0.909 g/mL (density of picaridin) x 

1,000 mg/g (conversion factor) x 50 cans] are applied directly to water body.

d 6.6 packs of towelettes possess equivalent amount of picaridin contained within one can of product. Therefore, 

330 packs of towelettes possess same amount of picaridin contained amongst 50 cans of product.

e

 Maximum EEC shown in bold face.

6.2 Monitoring Data for Picaridin

Limited information regarding environmental monitoring data are available for picaridin. 

However, in one study, picaridin was detected in influent waters to a wastewater treatment plant 

in Germany at concentrations between 0.6 - 1.4 g/L (Knepper, 2004). The Knepper paper noted 

the consistent decline in DEET concentrations observed in surface waters over a 5 year period 

coinciding when picaridin appeared on the local market as an alternative to DEET.

The sampling interval and duration in the study is not specified. In effluent waters, picaridin was 

not detected. However, the carboxylic acid degradate of picaridin was detected in the effluent 

waters (Knepper, 2004). The levels at which picaridin carboxylic acid was detected at was not 

quantified. The upper-bound EEC of 81 g/L calculated from Table 6.2 of Section 6.1 is higher 

than picaridin concentrations detected in the influent wastewater treatment plant waters by a 

magnitude of approximately 58X.

6.3 Terrestrial Exposure Analysis

Exposure to non-target terrestrial organisms and plants is presumed negligible based on use 

patterns (Section 5.2) and will not be estimated.

7. Risk Characterization

7.1 Risk Estimation

Toxicity data and exposure estimates are used to evaluate the potential for adverse ecological 

effects on non-target species. This assessment for picaridin relies on the deterministic RQ method 

to provide a metric of potential risks. The RQ provides a comparison of exposure estimates to 

toxicity endpoints (i.e., the estimated exposure concentrations are divided by acute toxicity 

values). The resulting unitless RQs are compared to the Agency’s LOCs, as shown in Table 4.1. 

LOCs are used by the Agency to indicate when the use of a pesticide, as directed by the label, has 

the potential to cause adverse effects to non-target organisms.

7.1.1 Aquatic Organisms 

The screening-level aquatic EECs based on the application rates for highest concentration products 

for human use and the only product registered for horse use. The exposure estimates, representing

human or horse wash off concentrations in a 20 million liter pond, and aquatic toxicity data were 
Page 21 of 45

used to calculate acute RQs (Table 7.1). The expected concentrations of picaridin in the aquatic 

environment are several orders of magnitude lower than the observed aquatic LC50 and EC50s 

determined for picaridin, and thus the potential for adverse risks is low.

Table 7.1 Upper-bound Acute aquatic exposure RQs for picaridin applications (mg a.i./L).

Release Scenario and 

Description

Exposure 

(mg a.i./

individual/

day)

Total 

Picaridin 

Mass 

Washoff

(mg)

Bulk 

Acute 

Picaridin 

Pond 

EEC

(mg/L)

a

RQ for 

Freshwater 

Fish2

RQ for 

Freshwater 

Invertebrate

RQ for 

Aquatic 

Plants

Scenario 1 - 10 treated adults

to water body 3,418.8

34,188 0.0017 < 0.001 < 0.001 < 0.001

Scenario 2 - 100 treated 

adults to water body 341,880 0.017 < 0.001 < 0.001 < 0.001

Scenario 3 - 10 treated horses

to water body 7,631.3b 76,313b 0.0038 < 0.001 < 0.001 < 0.001

Scenario 4 –

50 cans product or 330 packs 

of towelettes impregnated 

with picaridin released to 

water body,

N/A 1,612,748c,d 0.081 < 0.001 < 0.001 <0.001

a

 EECs Based on a Pond volume of 20,000,000 L.

b

 LC50 for fish = 173 mg a.i/L. EC50 for FW Invertebrate > 103 mg a.i/L. EC50 for FW Algae = 83 mg a.i/L

c

 Maximum EEC shown in bold. 

7.1.2 Terrestrial Organisms

No significant exposure to terrestrial organisms is predicted based current use patterns for picaridin 

(localized spray) and the active ingredient is determined to be practically non-toxic to birds and 

only slightly toxic to mammals. Therefore, risk to terrestrial organisms is not estimated. 

7.1.2 Incident Database Review

A review of the following databases was completed in March, 2014:

 Ecological Incident Information System (EIIS), 

 ‘Aggregate Incident Reports’ database, 

 Avian Incident Monitoring System (AIMS, 

http://www.abcbirds.org/abcprograms/policy/toxins/aims/aims) 

 Contaminant Exposure and Effects – Terrestrial Vertebrate (CEE-TV, 

http://www.pwrc.usgs.gov/contaminants-online/pages/CEETV/CEETVintro.htm).

No incidents for picaridin were identified in the EIIS, AIMS, the OPP Incident Data System (IDS)

or the CEE-TV databases.
Page 22 of 45

7.2 Risk Description

7.2.1 Exposure and Risk to Aquatic Organisms

The results of risk estimation indicate that registered uses of picaridin will not result in acute RQs 

that exceed the LOC for freshwater fish and invertebrates. Chronic RQs for freshwater organisms

were not calculated; however, given the large margin of safety observed for acute effects based on 

the most conservative exposure scenario, it is unlikely that chronic RQs would approach concern 

levels. Additionally, there are no acute or chronic estuarine/marine data for fish and invertebrates 

with which to estimate RQs, however risk is presumed to be below the level of concern based on 

low toxicity to freshwater taxa and low exposure in the water column.

RQs were calculated for non-vascular aquatic plants using the limited toxicity data that were 

available. RQs were estimated to be lower than the non-listed LOC for non-vascular aquatic

plants. Toxicity data are not available for vascular aquatic plants but risk is presumed to be below 

the level of concern based on low toxicity to aquatic non-vascular plants and low exposure in the 

water column. Also, there are no reported incidents for aquatic organisms or plants. 

7.2.2 Risks to Terrestrial Organisms

Exposure in terrestrial habitats would be limited to human skin, clothing, and shoes, as well as 

horse skin and hair. Products formulated as lotions or impregnated wipes would be applied directly 

to the human skin. Many other product labels specify recommended spray distances of less than 

10 inches from the intended application sites (human skin, clothing, and shoes, as well as horse 

skin and hair). Any movement away from the site of application represents potential exposure 

pathways for a broad range of biological receptors of concern (non-target terrestrial animals and 

plants) and the potential attribute changes, i.e., effects such as reduced survival, growth and 

reproduction, in the receptors due to picaridin exposure. However, the amount of picaridin 

resulting from human or horse application in the terrestrial environment (air, ground, plants, or 

non-treated animals) is inconsequential. As there is no complete exposure pathway to result in

substantive exposure of non-target terrestrial organisms under the currently registered uses, EFED 

has presumed risk is discountable to terrestrial organisms.

7.3 Uncertainties, Limitations, and Data Gaps

With only one acceptable hydrolysis study submitted to the Agency, there are many data gaps for 

fate and transport parameters. However, the available open literature and monitoring data suggest 

picaridin does exist in aquatic environments with low concentrations. Furthermore, it has been 

demonstrated that picaridin can degrade to picaridin carboxylic acid to some extent in the 

environment (Knepper, 2004). The rate at which picaridin degrades to the carboxylic acid and the 

amount of picaridin carboxylic acid is not known. However, the calculated upper-bound exposure 

based on wash off from treated humans and horses into a pond and the monitoring data suggest 

that potential aquatic exposures are very low, several orders of magnitude less than levels of 

concern. As a result, chronic exposure is not expected given the very low exposure occurring from 

a one-time short-term release into water. In addition, picaridin would have to be greater than three 
Page 23 of 45

orders of magnitude more toxic on a chronic basis than acute in order to exceed the chronic LOC 

for all aquatic taxa. This is assuming the acute EEC is equivalent to the chronic EEC. This 

assumption does not consider the decrease of exposure overtime resulting from the degradation of 

total toxic residues or any mixing that would occur to dilute the picaridin concentration overtime. 

Chronic exposure resulting in adverse effects would also be highly unlikely since repetitive

scenarios where picaridin washoff occurs from masses of people and horses in water bodies is not 

expected to occur frequently over a localized area. However, it should be noted that although 

chronic exposure is anticipated to be small, its full extent occurring in water bodies where picaridin 

is released is unknown based on the information currently available on the degradation of picaridin 

in the environment. 

Few ecotoxicity studies have been submitted to the Agency, and there are many data gaps for the 

effects data. However, under the currently registered use patterns, EFED has concluded (1) low 

likelihood of risk to aquatic organisms (2) low likelihood of risk to terrestrial organisms due to the 

lack of an exposure pathway.

Unless the use patterns of picaridin change through proposed registrations of new labels, EFED 

determines that additional data would not have substantial added value to the overall risk 

assessment.. 

8. Federally Threatened and Endangered (Listed) Species 

Concerns

Section 7 of the Endangered Species Act, 16 U.S.C. Section 1536(a)(2), requires all federal 

agencies to consult with the National Marine Fisheries Service (NMFS) for marine and 

anadromous listed species, and/or the United States Fish and Wildlife Service (USFWS) for listed 

wildlife and freshwater organisms, if they are proposing an "action" that may affect listed species 

or their designated critical habitat. The federal action addressed herein is the proposed registration 

renewal of picaridin for human and horse use and it is expected that the use could occur nationwide.

For a more detailed general description of the Endangered Species assessment process and the 

various components and assumptions of this process see Appendix E at the end of this document.

For the uses of picaridin, risk from acute exposure is not expected for any listed non-target animals 

or plants (Table 8.1). Additionally, the Agency has determined that there will be no habitat 

modification of any designated critical habitat for listed species from the current registered uses of 

picaridin. Inference regarding aquatic organisms and plants are based on the risk conclusions that 

registered uses of picaridin will not result in LOC exceedances for acute risk to fish and 

invertebrates. Based on expected EECs and limited acute plant data on algal species, EFED 

presumed direct risks were lower than concern levels to aquatic plants. In addition, there have 

been no reported incidents for picaridin use to non-target plants, wildlife or aquatic life. No 

chronic data were available to allow for chronic RQ calculations. However, given the large margin 

of safety observed for acute effects based on the most conservative exposure scenario, chronic 

RQs are unlikely to exceed concern levels. Conclusions regarding terrestrial organisms and plants 

are based on the lack of a complete exposure pathway. Exposure in terrestrial habitats would be 

limited to human skin, clothing, and shoes, as well as horse skin and hair. Products formulated as 
Page 24 of 45

lotions or impregnated wipes would be applied directly to the human skin. Many other product 

labels specify recommended spray distances of less than 10 inches from the intended application 

sites (human skin, clothing, and shoes, as well as horse skin and hair). Exposure to listed species 

is not expected because they would not likely come in close contact with humans or domestic 

horses (i.e., the registered use sites). 

Table 8.1. Potential Effects to Federally Listed Taxa Associated with Direct or Indirect 

Effects from the Currently Registered Uses of Picaridin.

Listed Taxon Direct Effects Indirect Effects

Terrestrial and semi-aquatic plants - monocots

No No

Terrestrial and semi-aquatic plants - dicots

Birds

Terrestrial-phase amphibians and reptiles

Mammals

Terrestrial invertebrates

Aquatic nonvascular plants

Aquatic vascular plants

Freshwater fish

Aquatic-phase amphibians

Freshwater invertebrates

Marine/estuarine fish

Marine/estuarine invertebrates
Page 25 of 45

9. References 

Amer, A.; Mehlhorn, H. 2006. The sensilla of Aedes and Anopheles mosquitoes and their 

importance in repellency. Parasitol. Res. 99, 491-499.

Klun, J. A.; Khrimian, A.; Debboun, M. 2006. Repellent and Deterrent Effects of SS220, 

Picaridin, and DEET Suppress Human Blood Feeding by Aedes aegypti, Anopheles stephensi, and 

Phlebotomus papatasi. J. Med. Entomol. 43(1), 34-39.

Knepper, T.P, 2004. Analysis and mass spectrometric characterization of the insect repellent 

Bayrepel and its main metabolite Bayrepel-acid. J. Chromatogr. A, 1046, 159-166.

Licciardi, S.; Herve, J. P.; Darriet, F.; Hougard, J.-M.; Corbel, V. Lethal and behavioral effects of 

three synthetic repellents (DEET, IR3535 and KBR 3023) on Aedes aegypti mosquitoes in 

laboratory assays. Med. Vet. Entomol. 2006, 20, 288-293.

Moore, S. J.; Debboun, M. Insect Repellents: Principles, Methods, and Uses - History of Insect 

Repellents; Debboun, M.; Frances, S. P.; Strickman, D., 2007. Eds.; CRC Press: Boca Raton, pp 

3-29.

USEPA. 1998. Guidelines for Ecological Risk Assessment. United States Environmental 

Protection Agency (USEPA). Risk Assessment Forum. Office of Research and Development. 

Available at http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=12460 (Accessed June 19, 

2009).

USEPA. 2005. Pesticide Fact Sheet for Picaridin. United States Environmental Protection 

Agency (USEPA). Office of Pesticide Programs. Available on-line at 

http://www.epa.gov/opp00001/chem_search/reg_actions/registration/fs_PC-070705_01-May05.pdf (Accessed February 18, 2014).

USEPA 2012. Standard Operating Procedures for Residential Pesticide Exposure Assessment. 

U.S. Environmental Protection Agency, Office of Pollution Prevention and Toxics, Office of 

Pesticide Programs, Health Effects Division. Washington DC. 

http://www.epa.gov/pesticides/science/residential-exposure-sop.html

USFWS/NMFS/NOAA.2004. 50 CFR Part 402. Joint Counterpart Endangered Species Act 

Section 7 Consultation Regulations; Final Rule. Federal Register Volume 69. Number 20. Pages 

47731-47762. August 5, 2004.

WHO, 2004. WHO specifications and evaluations for public health pesticides. Icaridin. Geneva, 

Switzerland: World Health Organization. 

http://www.who.int/whopes/quality/en/Icaridin_spec_eval_Oct_2004.pdf
Page 26 of 45

Appendix A: Environmental Fate and Ecotoxicity Data 

Requirement Tables

Table A-1. Available environmental fate data for picaridin and remaining data gaps.

158 Guideline

(OPPTS) Description MRID Classification Data Gap?

835.1230

(163-1)

Leaching No data N/A No*

835.1240

(163-1)

Adsorption/desorption No data N/A No*

835.1410

(163-2)

Laboratory volatility No data N/A No*

835.2120

(161-1)

Hydrolysis MRID 44408743 Acceptable No

835.2240

(161-2)

Photodegradation in water No data N/A No*

835.2370

(161-4)

Photodegradation in air No data N/A No*

835.2410 

(161-3)

Photodegradation on soil No data N/A No*

835.4100

(162-1)

Aerobic soil metabolism No data N/A No*

835.4200

(162-2)

Anaerobic soil metabolism No data N/A No*

835.4300

(162-4)

Aerobic aquatic metabolism No data N/A No*

835.4400

(162-3)

Anaerobic aquatic 

metabolism

No data N/A No*

835.6100

(164-1)

Terrestrial field dissipation No data N/A No*

835.6200

(164-2)

Aquatic field dissipation No data N/A No*

835-6300

(164-3)

Forestry field dissipation No data N/A No*

850.1730

(165-4)

Fish bioconcentration factor No data N/A No*

NGS Drinking water treatment No data N/A No*

* Not identified as a data gap under currently registered uses. Proposal of new uses may change the data 

requirements.

N/A means not applicable.
Page 27 of 45

Table A-2. Available ecological effects data for terrestrial animals exposed to technical picaridin and 

remaining data gaps. 

158

Guideline

(OPPTS)

Description MRID/

Accession Classification Data Gap? Comments

850.2100

(71-1) Avian oral toxicity No data N/A No

Avian dietary study 

was conducted as a 

limit test with no 

effects at 5000 ppm 

in diet

.

850.2200

(71-2) Avian dietary toxicity 44408739 Acceptable No*

850.2300

(71-4) Avian reproduction No data N/A No*

850.3020

(141-1)

Honeybee acute 

contact toxicity

No data N/A No*

850.3040

(141-5)

Field testing for 

pollinators

No data

N/A No*

* Not identified as a data gap under currently registered uses. Proposal of new uses may change the data requirements.

N/A means not applicable.

Table A-3. Available ecological effects data for aquatic animals exposed to technical picaridin and remaining 

data gaps.

Guideline Description MRID/ Accession Classification Data Gap?

850.1075

(72-1)

Freshwater fish –

acute toxicity 

44408740 Acceptable No

850.1075

(72-3)

Saltwater fish –

acute toxicity 

No data

N/A No*

850.1010

(72-2)

Freshwater invertebrates –

acute toxicity 44408741 Acceptable No

850.1025

s850.1035

(72-3)

Saltwater invertebrates –

acute toxicity 

No data

N/A No*

850.1300

(72-4)

Freshwater invertebrate –

life cycle test

No data N/A No*

850.1350

(72-4)

Saltwater invertebrates –

life cycle test

No data

N/A No*

850.1400

(72-4) Freshwater fish –

early life stage test

No data

N/A No*

850.1400

(72-4)

Saltwater fish –

early life stage test

No data

N/A No*

850.1500

(72-5)

Fish –

life cycle test

No data N/A No*

* Not identified as a data gap under currently registered uses. Proposal of new uses may change the data requirements.

N/A means not applicable.
Page 28 of 45

Table A-4. Available ecological effects data for plants exposed to picaridin and remaining data gaps. 

Guideline Description MRID Classification Data Gap? Comments

850.4100

(122-1)

Terrestrial plant toxicity: 

tier 1 seedling emergence

No data N/A No*

850.4225

(123-1)

Terrestrial plant toxicity: 

tier 2 seedling emergence

No data N/A No*

850.4150

(122-1)

Terrestrial plant toxicity: 

tier I vegetative vigor

No data N/A No*

850.4150

(123-1)

Terrestrial plant toxicity: 

tier 2 vegetative vigor

No data N/A No*

850.4400

(123-2)

Aquatic plant growth: 

algae

44408742 Supplemental No* This was a 72 hour 

exposure 

850.4400

(123-2)

Aquatic plant growth: 

vascular plants

No data N/A No*

* Not identified as a data gap under currently registered uses. Proposal of new uses may change the data requirements.

N/A means not applicable.

850.2200 Avian Dietary Toxicity

MRID Citation Reference

44408739 Schmuck, R. (1997) Five Day Dietary Toxicity of KBR 3023 on Bobwhite Quail (Colinus 

virginianus): Lab Project Number: 107844: E 295 1154-7: SXR/VB 58. Unpublished study 

prepared by Bayer Ag. 38 p. 

850.1075 Acute Toxicity to Freshwater Fish

MRID Citation Reference

44408740 Dorgerloh, M. (1996) KBR 3023 Technical--Acute Toxicity (96 Hours) to Rainbow Trout 

(Oncorhynchus mykiss) in a Static Test: Lab Project Number: E 2501093-0: 107845: DOM 

96024. Unpublished study prepared by Bayer Ag. 48 p. 

850.1010 Acute Toxicity to Freshwater Invertebrates

MRID Citation Reference

44408741 Heimbach, F. (1996) Acute Toxicity of KBR 3023 Technical to Waterfleas (Daphnia magna): 

Lab Project Number: 107690: E 320 1103-0: HBF/DM 162. Unpublished study prepared by 

Bayer Ag. 40 p. 
Page 29 of 45

850.4400 Acute Toxicity to Non-vascular Aquatic Plant

MRID Citation Reference

44408742 Anderson, J. (1996) Influence of KBR 3023 Technical on the Growth of the Green 

Alga, Scenedesmus subspicatus: Lab Project Number: 107689: E 323 1072-8: 

AJO/146496. Unpublished study prepared by Bayer Ag. 35 p.

835 Hydrolysis

44408743 2075607

2075608

Hellpointner, E. (1996) Hydrolysis of (carbon 14) KBR 3023 in Sterile aqueous 

Buffers: Lab Project Number: 107961: M 111 0795 4: HPO-138. Unpublished 

study prepared by Bayer Ag. 34 p. 
Page 30 of 45

Appendix B: Publically Available Data Table from EPA’s ECOTOX 

Database

Only a single article regarding toxicity of picaridin was located in ECOTOX database. It shows 

effect levels for a species of African Tilapia to be very low. Articles on terrestrial organism 

effects were not found.

Table B-1. Aquatic Ecotoxicity references provided in the publically available ECOTOX 

CAS 

Number Species tested Endpoint

Conc 1 

Mean 

(ug/L)

Units 

(ug/L)

Reference 

Number Author Title

Source/ 

year

134623

Mozambique 

Tilapia , 

Oreochromis 

mossambicus NR 120000 ug/L 3073

Mathai,A.T., 

K.S. Pillai, and 

P.B. Deshmukh

Acute Toxicity of Picaridin 

to a Freshwater Fish, Tilapia 

mossambica: Effect on 

Tissue Glutathione Levels

J. Environ. 

Biol.10(2): 

87-91, 

1989
Page 31 of 45

Appendix C. Pending and Active Registrations For

Ingredient

070705 / 119515-38-7 / Picaridin

Registration # Registration Name Company # Company Name Current 

Status

% of 

Active 

Ingredient

121-89 CUTTER INSECT 

REPELLENT 7K 121

SPECTRUM, A 

DIV OF UNITED 

INDUSTRIES 

CORP

Active -

Conditionally 

Registered 

(15-Dec2004)

7

121-90 CUTTER INSECT 

REPELLENT 5KT 121

SPECTRUM, A 

DIV OF UNITED 

INDUSTRIES 

CORP

Active -

Conditionally 

Registered 

(16-Dec2004)

5.75

121-91

CUTTER INSECT 

REPELLENT 

15KP

121

SPECTRUM, A 

DIV OF UNITED 

INDUSTRIES 

CORP

Active -

Conditionally 

Registered 

(20-Oct2005)

15

121-92

CUTTER INSECT 

REPELLENT 

15KA

121

SPECTRUM, A 

DIV OF UNITED 

INDUSTRIES 

CORP

Active -

Conditionally 

Registered 

(03-Nov2005)

15

121-93

CUTTER INSECT 

REPELLENT 

12KT

121

SPECTRUM, A 

DIV OF UNITED 

INDUSTRIES 

CORP

Active -

Conditionally 

Registered 

(03-Nov2005)

12

121-94

CUTTER INSECT 

REPELLENT 

10KP

121

SPECTRUM, A 

DIV OF UNITED 

INDUSTRIES 

CORP

Active -

Conditionally 

Registered 

(03-Nov2005)

10

121-95

CUTTER INSECT 

REPELLENT 

10KA

121

SPECTRUM, A 

DIV OF UNITED 

INDUSTRIES 

CORP

Active -

Conditionally 

Registered 

(03-Nov2005)

10

121-97 CUTTER INSECT 

REPELLENT SS 121

SPECTRUM, A 

DIV OF UNITED 

INDUSTRIES 

CORP

Active -

Conditionally 

Registered 

15
Page 32 of 45

(29-Oct2008)

121-99 CUTTER INSECT 

REPELLENT 121

SPECTRUM, A 

DIV OF UNITED 

INDUSTRIES 

CORP

Active -

Conditionally 

Registered 

(27-Aug2008)

20

121-100

CUTTER INSECT 

REPELLENT 

20KA

121

SPECTRUM, A 

DIV OF UNITED 

INDUSTRIES 

CORP

Active -

Conditionally 

Registered 

(29-Oct2008)

20

806-29

AVON SKIN-SOSOFT SSS BUG 

GUARD PLUS 

PICARIDIN 

INSECT 

REPELLENT 

AEROSOL 

SPRAY

806 AVON 

PRODUCTS, INC.

Active -

Conditionally 

Registered 

(29-Aug2005)

10

806-30

AVON SKIN-SOSOFT SSS BUG 

GUARD PLUS 

PICARIDIN 

INSECT 

REPELLENT 

TOWELETTE(S)

806 AVON 

PRODUCTS, INC.

Active -

Conditionally 

Registered 

(28-Sep2006)

10

806-31

AVON SKIN-SOSOFT SSS BUG 

GUARD PLUS 

PICARIDIN 

INSECT 

REPELLENT 

SPRAY

806 AVON 

PRODUCTS, INC.

Active -

Conditionally 

Registered 

(28-Sep2006)

10

4822-535

KBR 3023 ALLFAMILY INSECT 

REPELLENT 

CREAM II

4822 S.C. JOHNSON & 

SON INC.

Active -

Conditionally 

Registered 

(07-Dec2000)

5

4822-536

KBR 3023 ALLFAMILY INSECT 

REPELLENT 

NON-AEROSOL 

SPRAY

4822 S.C. JOHNSON & 

SON INC.

Active -

Conditionally 

Registered 

(07-Dec2000)

5

4822-537

KBR 3023 ALLFAMILY INSECT 

REPELLENT 

AEROSOL 

SPRAY

4822 S.C. JOHNSON & 

SON INC.

Active -

Conditionally 

Registered 

(07-Dec2000)

10
Page 33 of 45

4822-555 GENEVA-T 4822 S.C. JOHNSON & 

SON INC.

Active -

Conditionally 

Registered 

(17-Dec2007)

16

4822-556 GENEVA 4822 S.C. JOHNSON & 

SON INC.

Active -

Conditionally 

Registered 

(17-Dec2007)

20

4822-564 GENEVA-P 4822 S.C. JOHNSON & 

SON INC.

Active -

Conditionally 

Registered 

(09-Mar2009)

20

39967-48 KBR 3023 

TECHNICAL 39967 LANXESS CORPORATION

Active -

Conditionally 

Registered 

(07-Dec2000)

98.7

39967-50

KBR 3023 ALLFAMILY INSECT 

REPELLENT 

CREAM

39967 LANXESS 

CORPORATION

Active -

Conditionally 

Registered 

(30-Nov2006)

20

39967-53

KBR 3023 ALLFAMILY INSECT 

REPELLENT 

SPRAY

39967 LANXESS 

CORPORATION

Active -

Conditionally 

Registered 

(30-Nov2006)

20

54287-22

INSECT GUARD 

3023 INSECT 

REPELLENT

54287 ASSOCIATED 

REGISTRATIONS

Active -

Conditionally 

Registered 

(08-Nov2007)

20

56575-14

NATRAPEL 8 

HOUR INSECT 

REPELLENT 

WIPES

56575 TENDER 

CORPORATION 

Active -

Conditionally 

Registered 

(25-Mar2008)

20

56575-15

NATRAPEL 8 

HOUR INSECT 

REPELLENT 

CONTINUOUS 

SPRAY

56575 TENDER 

CORPORATION 

Active -

Conditionally 

Registered 

(15-Dec2008)

20

85972-1

CENTAURA FLY 

AND MOSQUITO 85972 CONVET GMBH & CO. KG

Active -

Conditionally 

Registered 

20
Page 34 of 45

REPELLENT 

SPRAY

(25-Sep2009)

86374-1

ECOPEL ALLFAMILY 

PROTECTION 

INSECT 

REPELLENT 

SPRAY

86374

ECOPEL 

CORPORATION, 

LTD

Active -

Conditionally 

Registered 

(06-Apr2010)

20

86459-1

FAMILY & 

ACTIVE-USE 

PROTECTION

86459 NEW HAVEN 

BRANDS CORP.

Active -

Registered 

(15-Aug2013)

20

121PA1 121

SPECTRUM, A 

DIV OF UNITED 

INDUSTRIES 

CORP

Pending (02-

Dec-2008) 20

Total Rows: 29

Synonym Information For Ingredient

070705 / 119515-38-7 / Picaridin

Name Type

1-(1-Methyl-propoxycarbonyl)-2-(2-hydroxyethyl)-piperidine Other Systematic

1-Methylpropyl 2-(2-hydroxyethyl)-1-piperidine-carboxylate Other Systematic

1-Piperidinecarboxylic acid, 2-(2-hydroxyethyl)-, 1-methylpropyl ester Other Common

KBR 3023 Trade

Picaridin Other Common

Total Rows: 5

Site/Pest Information For

Ingredient

070705 / 119515-38-7 / Picaridin

Site Information

Go to Pest Info

Site Code Site Name Status Status Date Registration #
Page 35 of 45

860110001 HUMAN ANIMAL ATTACK 

PREVENTATIVE Pending 20-Mar2013 86459-1

860030001 CLOTHES Approved 27-Aug2008 121-99

560052606 HORSES (ANIMAL TREATMENT) Approved 17-Mar2010 85972-1

860020005 HUMAN CLOTHING Approved 21-Mar2005 4822-537

860030000 HUMAN CLOTHING Approved 04-Apr2005 4822-536

860030004 HUMAN CLOTHING Approved 20-Oct2005 121-91

860020005 HUMAN CLOTHING Approved 03-Nov2005 121-92

860030004 HUMAN CLOTHING Approved 03-Nov2005 121-94

860030004 HUMAN CLOTHING Approved 28-Sep2006 806-31

860020011 HUMAN CLOTHING (FOOTWEAR) Approved 03-Nov2005 121-92

860020011 HUMAN CLOTHING (FOOTWEAR) Approved 03-Nov2005 121-94

860020006 HUMAN FACE AREA Approved 29-Aug2005 806-29

860020006 HUMAN FACE AREA Approved 20-Oct2005 121-91

860020006 HUMAN FACE AREA Approved 03-Nov2005 121-92
Page 36 of 45

860020006 HUMAN FACE AREA Approved 03-Nov2005 121-93

860020006 HUMAN FACE AREA Approved 03-Nov2005 121-94

860020006 HUMAN FACE AREA Approved 03-Nov2005 121-95

860020006 HUMAN FACE AREA Approved 25-Jan2006 4822-536

860020006 HUMAN FACE AREA Approved 28-Sep2006 806-31

860020006 HUMAN FACE AREA Approved 30-Nov2006 39967-53

860020006 HUMAN FACE AREA Approved 17-Dec2007 4822-556

860020006 HUMAN FACE AREA Approved 29-Oct2008 121-97

860020006 HUMAN FACE AREA Approved 29-Oct2008 121-100

860020006 HUMAN FACE AREA Approved 02-Dec2008 54287-22

860020006 HUMAN FACE AREA Approved 15-Dec2008 56575-15

860020006 HUMAN FACE AREA Approved 09-Mar2009 4822-564

860020006 HUMAN FACE AREA Approved 23-Jun2009 121-89

860020006 HUMAN FACE AREA Approved 23-Jun2009 121-90
Page 37 of 45

860020006 HUMAN FACE AREA Approved 09-Jun2010 86374-1

860020008 HUMAN NECK AREA Approved 20-Oct2005 121-91

860020008 HUMAN NECK AREA Approved 03-Nov2005 121-92

860020008 HUMAN NECK AREA Approved 03-Nov2005 121-94

860020008 HUMAN NECK AREA Approved 03-Nov2005 121-95

860020008 HUMAN NECK AREA Approved 30-Nov2006 39967-53

860020008 HUMAN NECK AREA Approved 29-Oct2008 121-97

860020008 HUMAN NECK AREA Approved 02-Dec2008 54287-22

860020008 HUMAN NECK AREA Approved 23-Jun2009 121-89

860020008 HUMAN NECK AREA Approved 23-Jun2009 121-90

860020008 HUMAN NECK AREA Approved 23-Jun2009 121-93

860020009 HUMAN SKIN Approved 07-Dec2000 4822-536

860020009 HUMAN SKIN Approved 07-Dec2000 4822-537

860020009 HUMAN SKIN Approved 07-Dec2000 4822-535
Page 38 of 45

860020009 HUMAN SKIN Approved 15-Dec2004 121-89

860020009 HUMAN SKIN Approved 15-Dec2004 121-90

860020009 HUMAN SKIN Approved 29-Aug2005 806-29

860020009 HUMAN SKIN Approved 20-Oct2005 121-91

860020009 HUMAN SKIN Approved 03-Nov2005 121-92

860020009 HUMAN SKIN Approved 03-Nov2005 121-93

860020009 HUMAN SKIN Approved 03-Nov2005 121-94

860020009 HUMAN SKIN Approved 03-Nov2005 121-95

860020009 HUMAN SKIN Approved 28-Sep2006 806-30

860020009 HUMAN SKIN Approved 28-Sep2006 806-31

860020009 HUMAN SKIN Approved 30-Nov2006 39967-50

860020009 HUMAN SKIN Approved 08-Nov2007 54287-22

860020009 HUMAN SKIN Approved 17-Dec2007 4822-555

860020009 HUMAN SKIN Approved 17-Dec2007 4822-556
Page 39 of 45

860020009 HUMAN SKIN Approved 25-Mar2008 56575-14

860020009 HUMAN SKIN Approved 27-Aug2008 121-99

860020009 HUMAN SKIN Approved 29-Oct2008 121-97

860020009 HUMAN SKIN Approved 29-Oct2008 121-100

860020009 HUMAN SKIN Approved 15-Dec2008 56575-15

860020009 HUMAN SKIN Approved 09-Mar2009 4822-564

860020009 HUMAN SKIN Approved 09-Jun2010 86374-1

860020004 HUMANS Approved 30-Nov2006 39967-53

860020004 HUMANS Approved 17-Mar2010 85972-1

990000002 MANUFACTURING USE ONLY NO 

SITE Approved 07-Dec2000 39967-48

Total Rows: 66
Page 40 of 45

Appendix D: Picaridin Degradation Pathway

In the absence of abiotic and biodegradation studies, the Catabol 301c model was used to 

simulate the environmental degradation for picaridin. The depiction of the degradation

pathway is shown in Figure D.1 below. The degradation pathway from Catabol 301c 

suggests that picaridin eventually degrades to the degradate picaridin carboxylic acid 

through a multi-step process including multiple oxidation and processes. Picaridin 

carboxylic acid forms after the second intermediate step in the predicted degradation 

pathway. This is consistent with wastewater stream monitoring data where picaridin was 

detected in the influent region and the degradate picaridin carboxylic acid was detected in 

the effluent region (Knepper, 2004). Although the wastewater treatment process may 

have impacted the formation of picaridin carboxylic acid within the stream in the 

monitoring study, the oxidation processes shown in Figure D.1 demonstrate that the 

formation of picaridin carboxylic acid in the environment is plausible as these processes 

are known to occur naturally in the environment without any wastewater treatment. The 

first six individual processes for the breakdown aromatic ring structures originating from

parent picaridin are shown in Table D.1. The processes described in Table D.1

correspond to the numbered sections in Figure D.1. The numbered steps and individual 

processes are shown until the point that there are no aromatic rings which remain intact.

Table D.1. Process steps for the environmental degradation pathway of 

picaridin predicted by the Catabol 301c model. 

Step Degradation Process

1 Primary hydroxyl group oxidation

2 Aldehyde oxidation

3 Ester hydrolysis

4 Decarboxylation

5 Decarobxylation

6 Oxidative deamination and N-dealkylation

* The numbered steps correspond to the breakdown pathway shown in Figure E.1 below.
Page 41 of 45

Figure D.1. Catabol 301c predicted environmental degradation pathway for 

picaridin.

Picaridin 

Picaridin carboxylic acid

1

2

3

4

5
Page 42 of 45

Figure D.1. Catabol 301c predicted environmental degradation pathway for 

picaridin (continued).

6
Page 43 of 45

Appendix E

Endangered Species Assessment Information

Based on this screening-level assessment, there are no potential risks of direct effects to 

listed species predicted from the use of Picaridin for its registered use. Listed species 

may also be affected through indirect effects because of the potential direct effects on 

listed and non-listed species. Potential direct effects on listed species from the use of 

Picaridin associated with modification of primary constituent elements of designated 

critical habitats is not expected. However, at this current stage of the Registration 

Review process, it is premature to make effects determinations for listed species until 

further refinements are conducted. To make effects determinations for individual 

species, useful refinements may include analyses of 1) more detailed, species-specific 

ecological and biological data; 2) more detailed and accurate information on Picaridin use 

patterns; and 3) sub-county level spatial proximity data for the co-occurrence of potential 

effects areas and listed species and any designated critical habitat. Examples of such 

refinements are described below.

EFED is currently developing tools that are expected to further refine the assessment and 

are designed to support effects determinations for individual federally listed species and 

their designated critical habitats (where applicable). Scientific information obtained from 

the U.S. Fish & Wildlife Service (USFWS), the National Marine Fisheries Service 

(NMFS), and other reliable sources is being collated by EFED to address all currently 

listed species. The information will be stored in an Office of Pesticide Programs 

Pesticide Registration Information SysteM (PRISM) knowledgebase. The listed species 

knowledgebase will consist of an information repository that houses biological and 

behavioral information relevant to individual species (e.g., habitat, diet, and life history, 

including specific temporal and spatial associations) and a document repository that 

contains supporting documents (e.g., USFWS recovery plans) and electronic information 

(e.g., GIS data files). For terrestrial taxa, the biological information relevant to risk 

quotient (RQ) calculations (e.g., diet and body weight) will be used to parameterize 

exposure estimates to derive species-specific RQs using a method consistent with 

currently used methods in the T-REX and T-HERPS models. 

Refinements may also include more detailed analyses of the registered uses and their use 

patterns that result in LOC exceedances for federally listed species in the screening-level 

assessment. The analyses may include more information on where, when, and how 

Picaridin is used. Actual usage data (when available) and national land-cover datasets 

that indicate potential use sites [e.g., national land cover dataset (NLCD), crop data layer 

(CDL)] may be used to support a more refined analysis of where Picaridin is reasonably 

expected to be used. Similarly, refinements for the timing of applications and how 

Picaridin is used may be based on the analysis of additional usage data, beyond what 

were available at the time of the screening-level assessment, and a more in-depth 

exploration of agronomic practices. 

The U.S. Environmental Protection Agency, along with the U.S. Department of 
Page 44 of 45

Agriculture (USDA), the U.S. Fish and Wildlife Service (FWS), and the National Marine 

Fisheries Service (NMFS), have announced the availability of a report developed by the 

National Academy of Sciences’ National Research Council outlining recommendations 

on specific scientific and technical issues related to the development of endangered and 

threatened species risk assessments for pesticides that are compliant with the Endangered 

Species Act (ESA) and the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA). 

The EPA, USDA, FWS and NMFS asked the NRC to consider a range of scientific and 

technical issues including:

• identifying best available scientific data and information; 

• considering sub-lethal, indirect and cumulative effects; 

• assessing the effects of chemical mixtures and inert ingredients; 

• analyzing the effects of pesticide use through the use of models; 

• incorporating uncertainties into the evaluations; and 

• using geospatial information and datasets that can be employed by the agencies in 

the course of these assessments. 

After reviewing the NRC’s recommendations on these scientific and technical issues, the 

EPA and its federal partners will determine how these recommendations can be 

implemented and incorporated into the scientific approaches for developing listed species 

risk assessments. It is anticipated that any draft guidance and/or science policies 

developed by EPA and its federal partners as a result of the NAS recommendations 

would be released for public comment prior to implementation. 

The refinements based on individual species data; additional, detailed usage information, 

when available; and further recommendations from the NRC report are expected to help 

to more accurately identify potential areas of effect and to better inform effects and 

habitat determinations for listed species and any designated critical habitats. 

For example, if quizalofop-p-ethyl is used when a particular species of concern is not 

present (e.g., it is migratory) or is not co-located in space, then risk of potential direct 

effects to the species may often be precluded. If LOCs are still exceeded for monocots, 

mammals, freshwater invertebrates, estuarine/marine invertebrates, and freshwater fish

after conducting the refined analyses, further analyses of the potential spatial and 

temporal co-occurrence of listed species of concern (and any designated critical habitat) 

may be conducted. The extent of possible refinement in the analyses of spatial/temporal 

co-occurrence will largely depend on the scale and quality of the available sub-county 

level use site (e.g., NLCD, CDL) and species location data.

The Agency has made several refinements to the list of endangered and threatened 

species that may be affected by quizalofop-p-ethyl uses. To date, there are 1442 listed 

species identified in the LOCATES database (v. 2.2.4, derived from USFWS and 

NMFS). For 1295 of these, a “no effect” determination for direct and indirect effects can 

be made based on a lack of geographical overlap, based on a county level of resolution, 

between the species and quizalofop-p-ethyl uses (Appendix J, Table J-1). A further 26 

species can be eliminated from consideration of direct effects (i.e., “no effects”) based on 

species specific ecological and biological information from listed species trustee agencies 
Page 45 of 45

(Appendix J, Table J-2). The remaining 121 species will need to be considered in more 

depth before effects calls are made (Appendix J, Table J-3). The biological, 

geographical, and use pattern information outlined above will be necessary to refine the 

assessment.