Page 2 of 2 Chemical PC Code CAS No.
Allethrin 004001 584

- 79

- 2 Bioallethrin 004003 28057

- 48

- 9 S

- Bioallethrin 004004 28434

- 00

- 6 D

- Allethrin 004005 84030

- 86

- 4 Esbiothrin 004007 84030

- 86

- 4 Bifenthrin 128825 82657

- 04

- 3 Cyclethrin 004052 97

- 11

- 0 Cyfluthrin 128831 68359

- 37

- 5 Cyfluthrin, beta

- 118831 68359

- 37

- 5 Cyhalothrin 128867 68085

- 85

- 8 Cyhalothin, lambda

- 128897 91465

- 08

- 6 Cyhalothrin, gamma

- 128807 76703

- 62

- 3 Cypermethrin 109702 52315

- 07

- 8 Cypermethrin, alpha

- 209600 67375

- 30

- 8 Cypermethrin, beta

- 109902 65731

- 84

- 2 Cypermethrin, zeta

- 129064 52315

- 07

- 8 Cyphenothrin 129013 39515

- 40

- 7 Deltamethrin 097805 52918

- 63

- 5 Esfenvalerate 109303 66230

- 04

- 4 Fenvalerate 109 301 51630

- 58

- 1 Fenfluthrin 109705 75867

- 00

- 4 Fenpropathrin 127901 39515

- 41

- 8 Imiprothrin 004006 72963

- 72

- 5 Metofluthrin 109709 240494

- 70

- 6 Permethrin 109701 52645

- 53

- 1 Prallethrin 128722 23031

- 36

- 9 Pyrethrins (not synthetic) 069001 8003

- 34

- 7 Resmethrin 097801 10453

- 86

- 8 Sumethrin (phenothrin) 069005 26002

- 80

- 2 Tau

- fluvalinate 109302 102851

- 06

- 9 Tefluthrin 128912 79538

- 32

- 2 Tetramethrin 069003 7696

- 12

- 0 Tralomethrin 121501 66841

- 25

- 6Page 1 of 88 

# Pyrethrins /Pyrethroid
Cumulative Risk Assessment

U.S. Environmental Protection Agency Office of Pesticide Programs October 4, 2011Pyrethroid Cumulative Risk Assessment

Page 2 of 88 

### Table of Contents

1.0 Introduction

................................ ................................ ................................ ................................ ..... 5

2.0 Determining the Common Mechanism & Establishing the CMG

................................ .................... 6

2.1 Pyrethroid Structure

................................ ................................ ................................ ........... 7
2.2 Voltage Gated Sodium Channels

................................ ................................ ........................ 8
2.3 In vivo Toxicity

................................ ................................ ................................ ................... 11

2.4 CMG for CRA

................................ ................................ ................................ ..................... 11

3.0 Common Assessment Group

................................ ................................ ................................ ......... 12

4.0 Hazard Assessment/Characterization

................................ ................................ ............................ 14

4.1 Endpoints and Toxicology Studies

................................ ................................ .................... 14

4.1.1 Establishing a Uniform Measure of Toxicity

................................ ........................ 14

4.1.1.1 Common Mechanism Endpoint

................................ .............................. 14 4.1.1.2 Experimental Laboratory Studies with Behavioral Measures

................. 16 4.1.1.3 Scientific Considerations in Evaluating Experimental Animal Studies

.... 17 4.1.1.4 Selection of Critical Study for Estimating Relative Potency

.................... 19
4.2 WIL FOB Study & Determining a Uniform Measure of Potency

................................ ....... 21

4.2.1 Introduction

................................ ................................ ................................ ......... 21

4.2.2 WIL Study Design

................................ ................................ ................................ . 22
4.2.3 Severity Scoring

................................ ................................ ................................ ... 22

4.2.4 Variable Coding

................................ ................................ ................................ .... 24
4.2.5 Dose

- Response Modeling and Derivation of Benchmark Dose (BMD) Estimates
for Dichotomous Data

................................ ................................ .......................... 25
4.2.5.1 Threshold Estimates for Pyrethroids Not Included in BMD Analysis

...... 26
4.3 Routes and Duration of Exposure for Potency Determination

................................ ......... 28
4.3.1 Routes of Exposure

................................ ................................ .............................. 28
4.3.1.1 Oral

................................ ................................ ................................ ....... 29
4.3.1.2 Dermal and Inhalation

................................ ................................ .......... 29

4.4 Index Chemical

................................ ................................ ................................ .................. 30

4.4.1 Candidates for Index Chemical

................................ ................................ ............ 30

4.5 Relative Potency Estimates & Points of Departure for the Index Chemical

..................... 31 4.5.1 Relative Potency Factors

................................ ................................ ......................... 31 4.5.2 Points of Departure

................................ ................................ ................................ . 32
4.6 FQPA Safety Factor for Protection of Infants & Children

................................ ................. 33

4.7 Incorporation of Uncertainty Factors/Extrapolation Factors and the Target M OE

.......... 35 4.8 Dose Additivity

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

5.0 Dietary Cumulative Exposure and Risk Assessment/Characterization

................................ .......... 37

5.1 Food Exposure Pathway

................................ ................................ ................................ .... 37

5.1.1 Dietary Consumption Data

................................ ................................ .................. 37
5.1.2 Pesticide Residue Data

................................ ................................ ......................... 38

5.1. 3 Pyrethroid Pesticides Included in the Dietary Risk Assessment

.......................... 38

5.1.4 Food Commodities Included in the Dietary Risk Assessment

.............................. 4 0Pyrethroid Cumulative Risk Assessment

Page 3 of 88 5.2 Drinking Water Pathway

................................ ................................ ................................ ... 40
5.3 Dietary (Food and Water) Assessment

................................ ................................ ............. 42

6.0 Residential Pyrethroid Cumulative Risk

................................ ................................ ......................... 45
6.1 Introduction

................................ ................................ ................................ ...................... 45
6.2 Residential Scenarios and Exposure Routes

................................ ................................ ..... 46
6.2.1 Lawn/Turf Use

................................ ................................ ................................ ...... 46
6.2.2 Garden, Ornamental, and Tree Use

................................ ................................ ..... 47
6.2.3 Indoor Use

................................ ................................ ................................ ............ 47
6.2.4 Pet Use

................................ ................................ ................................ ................. 48
6.3 Residential Handler Exposure and Risk

................................ ................................ ............. 48
6.3.1 Handler Algorithms

................................ ................................ .............................. 48
6.3.2 Handler Data and Assumptions

................................ ................................ ........... 49
6.3.2.1 Unit Exposure (UE)

................................ ................................ ................ 49
6.3.2.2 Application Rate (AR)

................................ ................................ ............ 53
6.3.2.3 Area Treated/Amount Handled (A)

................................ ...................... 53
6.3.3 Handler Risk Summary

................................ ................................ ......................... 54
6.4 Post

- application Exposure and Risk

................................ ................................ .................. 54
6.4.1 Post

- application Dermal Exposure

................................ ................................ ....... 54
6.4.1.1 Dermal Post

- application Algorithm

................................ ...................... 54
6.4.1.2 Dermal Post

- application Data and Assumptions

................................ .. 55
6.4.1.2.1 Transferable Residue (TR)

................................ .................... 55
6.4.1.2.2 Transfer Coefficient (TC)

................................ ....................... 60
6.4.1.2.3 Exposure Time (ET)

................................ ............................... 61
6.4.2 Post

- application Dermal Risk Summary

................................ ............................... 62
6.4.3 Post

- application Inhalation Exposure

................................ ................................ .. 62
6.4.3.1 Post

- application Inhalation Algorithms

................................ ................ 63
6.4.3.2 Post

- application Inhalation Data and Assumptions

............................. 64

6.4.3.2.1 Inhalation Rate (IR)

................................ ............................... 64
6.4.3.2.2 Mass of active ingredient applied (M label )

............................. 65
6.4.3.2.3 Air Changes per Hour (ACH)

................................ ................. 65
6.4.3.2.4 Volume of a Room (V
room )

................................ ..................... 65
6.4.3.2.5 First Order Decay Rate (k)

................................ .................... 65
6.4.3.2.6 Exposure Time (ET)

................................ ............................... 65
6.4.4 Post

- application Inhalation Risk Summary

................................ .......................... 65
6.4.5 Post

- application Incidental Oral Exposure and Risk

................................ ............ 66
6.4.5.1 Post

- application Incidental Oral Algorithm

................................ .......... 66
6.4.5.2 Post

- application Incidental Oral Data and Assumptions

...................... 67
6.4.5.2.1 Hand Residue (HR)

................................ ................................ 67
6.4. 5.2.2 Fraction of Hand Mouthed per Event (F M )

........................... 67
6.4.5.2.3 Hand Surface Area (SA H )

................................ ....................... 68
6.4.5.2.4 Fraction of Pesticide Extracted by Saliva (SE H )

..................... 68
6.4.5.2.5 Exposure Time (ET)

................................ ............................... 68
6.4.6 Post

- application Incidental Oral Risks

................................ ................................ . 68
6.4.7 Combined Exposure

................................ ................................ ............................. 68

7.0 Combined Screening Level Dietary + Residential Cumulative

................................ ....................... 70Pyrethroid Cumulative Risk Assessment

Page 4 of 88 8.0 Characterizing the Screening

- Level Pyrethroid Cumulative Risk Estimates

................................ .. 71
8.1 Hazard Characterization

................................ ................................ ................................ ... 71
8.2 Dietary Exposure Assumptions and Characterization

................................ ....................... 75
8.2.1 Food Exposure Pathway

................................ ................................ ....................... 75
8.2.2 Drinking Water Exposure Pathway

................................ ................................ ...... 75
8.3 Non

- Dietary Exposure Assumptions and Characterization

................................ .............. 75
8.4 Aggregate Exposure (Dietary + Non

- Dietary) Assumptions and Characterization

........... 77

9.0 Conclusion

................................ ................................ ................................ ................................ ...... 78

References

................................ ................................ ................................ ................................ .................. 80

Appendix 1

- Toxic ity Data for the Screening Level Cumulative Risk Assessment...........

............ . ...............A1

Appendix 2

- Herbeth Study DER

..................... ... ...................................................................................................A2

Appendix 3

- Weiner Study DER..... .......................................................................................................................A3

Appendix 4

- FOB Data for Weiner Study

... ........................................................................................................ . A4

Appendix 5

- BMDs for T and CS from WIL FOB Study......................................................................................A5

Appendix 6

- Deltamethrin Studies......................................................................................................................A6

Appendix 7

- Residential E xposure Tables... ...............................................................................................A7Pyrethroid Cumulative Risk Assessment

Page 5 of 88 

### 1.0 Introduction

With the passage of the Food Quality Protection Act of 1996 (FQPA), EPA i s required to consider available information concerning the cumulative effects on human health resulting from exposure to multiple chemicals that have a common mechanism of toxicity when making
decisions related to pesticide tolerances

. Pyrethroids are a class of synthetic insecticides which are structurally based on the pyrethrins , botanical insecticides ext racted from Chrysanthemum cinerariaefolium ( Soderlund et. al. 2002 )

. Pyrethrins are potent insecticides with relatively low mammalian toxicity but are sensitive to air and light. Hence, the use of pyrethrins for crop protection and to control disease

- carrying insects is limited. With an altered structure, the pyrethroids are more photosta ble, while retaining the insecticidal activity of the pyrethrins

. Thus, pyrethroids are widely used today in agriculture and in medical and veterinary products. The Agency has determined that a growing class of pesticides, the naturally occurring pyrethri ns and synthetic pyrethroids, has a common mechanism of toxicity and are thus subject to cumulative risk assessment under the FQPA

.

The cumulative risk assessment discussed in this document incorporate s multiple high

- end inputs and combine s the highest exposures/risk estimates across all pathways in a deterministic fashion resulting in a screening level assessment which is highly conservative and health protective. This cumulative assessment considered all registered uses of pyrethrins /pyre throids and included exposure from food, drinking water and residential settings from the oral, dermal and inhalation routes of exposure. Having completed this screening level assessment, the Agency concludes that cumulative estimated risks from existing pyrethrins /pyrethroid uses are
not of concern

.

T he Agency also concludes that there is sufficient room in the pyrethroid cumulative risk cup to support consideration of new pyrethroids (i.e., currently unregistered pyreth r oid pesticides)
and new uses of existing pyrethroids having similar toxicity profiles and use patterns to those in
this assessment given the multiple conservative inputs into the assessment. Per Agency policy, all new uses/new pyrethroid registration actions submitted to the Agency wil l undergo a single chemical assessment and also an evaluation of their potential contributions to cumulative risk. But the Agency believes that most of these are unlikely to have a significant impact on this screening

- level cumulative assessment, provided they meet the parameters outlined above.

D etails of the cumulative risk assessment process can be found in the OPP guidance document
entitled Guidance on Cumulative Risk Assessment of Pesticide Chemicals That Have a Common Mechanism of Toxicity ( USEPA 2002 ) . Briefly summarized here, the cumulative risk assessment (CRA ) is developed by a multi

- step process. The first step is the identification of a group of pesticides , called a C ommon M echanism Group (CMG) , which induce a common toxic effect by a common mechanism of toxicity. Pesticides are determined to have a “commo n mechanism of toxicity” if they act the same way in the body

– that is, the same toxic effect occurs in the same organ or tissue by essentially the same sequence of major biochemical events. Once a CMG is established, the next step is to evaluate registe red and proposed uses for each CMG member in order to identify potential exposure pathways (food, drinking water, residential) and routesPyrethroid Cumulative Risk Assessment

Page 6 of 88 (i.e., oral, inhalation, dermal). During the hazard characterization phase, the various endpoints
associated with the common mechanism of toxicity are identified, as well as the test species/sex that might serve as a uniform basis for determining relative potencies among the chemicals of interest. The common effect is also evaluated to determine if it is expressed

acros s all exposure routes and durations of interest for each CMG member. The temporal aspects (e.g., time to onset and peak effects, duration of effects, and time to recovery) of the
common mechanism of toxicity are characterized to determine the exposure dur ations relevant
for the common toxic effect. As part of the process, it is important to determine which chemicals from the CMG should be included in the quantification of cumulative risk. Therefore a subset of the CMG called the cumulative assessment group (CAG) is identified which excludes
those CM G members which have a minimal toxic contribution to the cumulative hazard or are limited to minor exposure pathways, routes, or uses. A dose response analysis is performed for each CAG member to determine its toxic potency for the common toxic effect. When physiologically

- based pharmacokinetic (PBPK) models are not available, EPA uses the relative potency factor (RPF) method to determine the combined estimated risk associated with exposure to the members of the CAG. Briefly, the RPF approach uses an in dex chemical as a point of reference for comparing the toxicity of the other members of the CAG. A point of departure is determined for the index chemical and relative potency factors are calculated (i.e., the ratio of the toxic potency of a given chemica l relative to that of the index chemical). RPFs are used to convert exposures of all chemicals in the CAG to exposure equivalents of the index chemical. A quantitative cumulati ve risk assessment is conducted by comparing the exposure equivalents to the p oint of departure for the index chemical across all pertinent exposure routes and durations. The last step in the CRA process is to characterize risk (i.e., an appraisal of the science supporting the risk assessment including choices made about methods, s trengths and limitations of the available data, and assumptions )

.

The Agency’s common mechanism grouping decision and scre e ning level cumulative risk
assessment for the pyrethrins and pyrethroid pesticides are presented in this document.

T hroughout the remainder of the document, references to the “pyrethroid CRA” include
consideration of both the naturally occurring pyrethrins and the synthetic pyrethroid chemicals.



### 2.0 Determin ing the Common Mechanism & Establishing the CMG

As previously noted, t he first step in conducting a cumulative risk assessment is the identification of a Common Mechanism Group (CMG), chemicals that induce a common toxic effect by a common mechanism of toxicity. Pesticides are determined to have a “common mechanism of toxicity” if they act the same way in the body

– that is, the same toxic effect occurs in the same organ or tissue by essentially the same sequence of major biochemical

events. In 2009, the Agency developed the “ Draft Science Policy Paper: P roposed Common Mechanism Grouping for the Pyrethrins and Synthetic Pyrethroids ” which proposed the common mode of action for pyrethroids

. This common mechanism grouping is based on 1) shared structural characteristics; and 2) shared ability to interact wi th voltage

- gated sodium channels (VGSC), resulting in disruption of membrane excitability in the nervous system, and 3)Pyrethroid Cumulative Risk Assessment

Page 7 of 88 ultimately neurotoxicity characterized by two different toxicity syndromes (Figure 2

. 0)

. The steps involved in this common toxicity pat hway are summarized below. ( USEPA 2011a )

. This proposal was reviewed and supported by the FIFRA Scientific Advisory Panel (SAP) 1

.

Figure 2.0. C ommon T oxic ity P athway of the Pyrethrins & P yrethroids



### 2 .1 Pyrethroid Structure

P yrethroids are composed of two basic structural moieties; an acid and an alcohol. For first generation pyrethroids

, such as allethrin, tetramethrin, and resmethrin , the acid portion is based on chrysanthemic acid, a cyclopropane ring bonded to a carboxylic acid moiety and a variety of halogenated and non

- halogenated substituents. More recently developed pyrethroids, su ch as fenvalerate, do not have a cyclopropane ring. The alcohol portion is either a primary or a secondary alcohol, which is bound to a variety of heterocyclic structures. In addition, several of the pyrethroids have a cyano substituent bound to the α

- me thylene of the alcohol, which results in enhanced toxicity of the compound. Pyrethroids lacking the α

- cyano substituent are generally termed Type I compounds and the pyrethroids with the α

- cyano substituent are generally termed Type II compounds. Figure 2 .1 , below, shows the structures of a Type I pyrethroid, permethrin, and a Type II pyrethroid, cypermethrin.

1 http://www.epa.gov/scipoly/sap/meetings/2007/august/pyrethroidpbpk_sap_2007_finalv1.pdfPyrethroid Cumulative Risk Assessment

Page 8 of 88 C H 3 H 3 C

O

C l C l O O

P e r m e t h r i n

C H 3 H 3 C

C l C l O

O

C N O

C y p e r m e t h r i n

Figure 2.1. The Structures of Permethrin (Type I) and Cypermethrin (Type II)



### 2.2 Voltage Gated Sodium Channels (VGSCs)

The naturally occurring pyrethrins and synthetic pyrethroids share the same mode of action, namely the interaction VGSCs ( Narahashi 1996 ; Soderlund et. al. 2002 ; Shafer et. al. 2005 ; Weiner et. al. 2009 ) . The effect s of pyrethroid exposure on neuronal tissue (both insects and mammals) have been extensively reviewed ( Soderlund and Bloomquist 1989 ; Vijverberg and
Bercken 1990 ; Narahashi 1992 ; Bloomquist 1993 ; Clark 1995 ; Soderlund 1995 ; Bloomquist

1996 ; Narahashi 1996 )

. Pyrethroids delay the inact ivation of a ffected VGSCs, allowing for an increase in sodium ion influx and resulting in delayed repolarization. The delay is more pronounced in cyano

- containing (Type II) pyrethroids ( >> 200 ms) resulting in depolarization

dependent block of the neuron al action potentials and toxicity. The delay is considerably
shorter for non

- cyano (Type I) pyrethroids (20ms) and results in repetitive firing of action potentials and toxicity . Mixed

- Type pyrethroids ( e.g

. esfenvalerate and fenpropathrin) produce delays intermediate between the characteristic Type I and Type II pyrethroids.

Figure 2.2 depicts generalized pyrethroid effects on individual channels, whole

- cell sodium currents, and action potentials (extracte d from Shafer et

. al. 2005)

. Depolarization opens VGSCs (top left) allowing sodium to enter the cell. To limit sodium entry and depolarization length, VGSCs inactivate and must return to a “resting” state before reopening. Pyrethroids
inhibit the function of two different “gates” that control sodium flux through VGSCs (top right), delaying inactivation (indicated by double arrows between states) of the channel and allowing continued sodium flux (Open*). If sodium current through an entire cell is measured, depolarization leads to a rapidly inactivating current under normal circumstances (bottom left, Sodium Current). Pyrethroid

- modified VGSCs remain open when depolarization ends (bottom right, Sodium Current), resulting in a “tail” current (the notch at the end of example currents). IfPyrethroid Cumulative Risk Assessment

Page 9 of 88 membrane voltage is examined, depolarization under normal circumstances generates a single action potential (bottom left). VGSCs modified by type I compounds (bottom right, Action Potential) depolarize the cell membrane above the threshold for action potential generation, resulting in a series of action potentials (repetitive firing). Type II compounds cause greater membrane depolarization, diminishing the sodium electrochemical gradient and subsequent action potential amplitud e. Eventually, membrane potential becomes depolarized above the threshold for action potential generation (depolarization

- dependent block) ( Shafer et. al. 2005 )

.

While interaction with the VGSC has been established as a key event by the Agency, pyrethroids have been reported to inhibit other types of ion channels, including chloride

- permeable ion channels, voltage

- gated calcium channels and ligand

- gated chloride channels ( Vijverberg and
Bercken 1990 ; Narahashi 1996 ; Narahashi et. al. 1998 ; Ray and Forshaw 2000 ; Ray 2001 ; Soderlund et. al. 2002 ; Burr and Ray 2004 ; Sha fer and Meyer 2004 )

. It has been suggested that pyrethroid actions at these separate target sites combine to prolong neuronal membrane depolarization, resulting in massive neurotransmitter release ( Clark and Brooks 1989 ) . While pyrethroid actions on VGSC s and neuronal excitability are well understood, information on the
other channels were conducted using different experimental models and are often contradictory ( Shafer and Meyer 2004 ; Clark and Symington 2008 ; Cao et. al. 2011b ) . Thus, relative to sodium channels, the level of evidence supporting modes of action via other channels is not compelling.Page 10 of 88 Figure 2.2 . Effects of pyrethroids on Na channels, currents, and action potentials (From Shafer et al. ( 2005 ) )Page 11 of 88 

### 2.3 In vivo Toxicity

High doses of pyrethroid s in laboratory animals result in one of two syndromes; the T

syndrome associated with Type I pyrethroids

, and the CS

- syndrome associated with Type II pyrethroids. The neurotoxic behaviors elicited by Type I pyrethroids are aggression, hyperexcitability, fine tremor, prostration with coarse whole body tremor, increased body temperature, coma and death. These neurobehavioral responses are termed the T

- syndrome because of the fine tremors induced by the Type I pyrethroids. For Type II pyrethroids, the neurotoxic behaviors include pawing and burrowing, salivation, hyperexcitability, abnormal hind limb movements, coarse whole body tremor, sin uous writ h ing, coma and death. These neurobehavioral responses are termed the CS

- syndrome for the choreoathetosis ( i.e., whole body writhing) and salivation. Some pyrethroids such as fenpropathrin and esfenvalerate , are considered mixed (Type I/II) becau se they elicit mixed behaviors of both the T

- and CS

syndromes. The T

- and CS

- syndromes are considered to be acute responses to pyrethroid exposure and are dose

- dependent. In mammals, the onset of neurobehavioral effects occur
within a few minutes to over an hour, depending on the route of exposure and chemical, but
can take 2

- 8 hours to peak. Recovery from pyrethroid toxicity is rapid, typically within 24

- 48 hours. Mammals, unlike insects, have extensive enzyme systems capable of metabolizing and
detoxi fying the pyrethroids. This difference in physiology makes pyrethroids an order of magnitude less toxic in mammals compared to insects.



### 2.4 CMG for CRA

At the present time

, EPA has designated the naturally occurring pyrethrins and synthetic pyrethroids as a common mechanism grouping for purposes of conducting a cumulative risk assessment under the FQPA. Consistent with the screening

- level nature of th is cumula tive assessment, the pyrethroid CR A includes a n interim decision to evaluate the Type I and Type II pyrethroids in a single group (i.e., one risk cup) ( USEPA 2011a )

.

In the 2009 CMG proposal, EPA considered the science that supported separat ing the pyrethroid CMG into two subgroups representing Type I and II pyrethroids. This subgrouping is consistent with historical categorization of pyrethroids and is supported by in vitro and in vivo
studies from both older studies and new research. As descr ibed previously in Section 2.1, t he designation of Type I an d Type II pyrethroids is based upon differences in structure; the α

- cyano moiety is absent in Type I pyrethroids ( e.g. , permethrin) and present in Type II ( e.g. , deltamethrin)

. The absence/presen ce of the α

- cyano group is correlated with length of time the sodium channel is inactivated (

- CN=shorter; +CN=longer) which in turn corresponds with the two distinct toxicity syndromes (

- CN=T syndrome; +CN=CS syndrome). Two pyrethroids,
esfenvalerate and f enpropathrin, though structurally similar to Type II pyrethroids, are considered mixed Type I/II because they demonstrate properties of both groups during i n vitro
and in vivo evaluations. As noted above, this screening level assessment demonstrates that the
cumulative estimated risk to pyrethrins and pyrethroids is not a concern. In the future, if thePyrethroid Cumulative Risk Assessment

Page 12 of 88 Agency determines that a more refined cumulative assessment is appropriate, the Agency may consider evaluating the cumulative risk to the Type I and Type I I pyrethroids separately.



### 3.0 C umulative Assessment Group (CAG)

As part of the cumulative risk assessment process, it is important to determine which chemicals from the CMG should be included in the quantification of cumulative risk. Therefore, a subset
of the CMG called the CAG is identified which excludes those CMG members with minimal toxic contribution to the cumulative hazard or those with limited uses or minor exposure pathways

or routes.

For the pyrethroid CAG , those chemicals which pose very low risk were considered unlikely
contributors to cumulative risk a nd were precluded from the assessment. Criteria for not including CMG chemicals in the CAG include:

**•** Pyrethroids with low hazard potential for the common mechanism endpoint (s) were excluded. Specifically, tetramethrin and sumithrin were excluded due to n o observed
adverse effects at 5 000 mg/kg in a specially designed functional observational batter y for evaluating pyrethroid toxicity syndromes in the rat

.

**•** For the dietary exposure assessment , pyrethroids without any residues in any crop in
the Pesticide Data Program monitoring data were not included in the dietary
assessment;

**•** For the residential exposure assessment , the Agency focused on only those residential uses that have potential for significant exposure (turf, pets, gardens, and indoor uses). Only pyrethroids with these residential uses were included in the CAG and assessed in the residential part of the CAG. In addition, t hose pyrethroids with residential uses that do not have a potential for significant exposure or have an insignificant amount of use ( e.g. , such as metofluthrin which is only registered for use in personal insect repellent systems) were considered minor contributors to the residential part of the CRA and
therefore not included in the CAG.

A total of 15 synthetic pyrethroids and the naturally occurring pyrethrins (including pyrethrins I and pyrethrins II) are included in the CAG and are p resented. Table 3.0 contains a list of pyrethroids registered with the Agency, highlighting those that were included in the CAG and offering bri ef explanations for those that were not.Pyrethroid Cumulative Risk Assessment

Page 13 of 88 Table 3. 0

. Pyrethroid Cumulative Assessment Group (CAG)

Chemical Name 1 Type Registration s PDP Data

Included in Screening Level Pyrethroid CRA/ Comments 3 Food Use Registration Non

- food Use Registration ( e.g. Residential Uses)? PDP

Data PDP

Detects

Allethrin I X X X X Included
Bifenthrin I X X X X Included Cyfluthrin II X X X X Included Cyhalothrin II X X X X Included Cypermethrin II X X X X Included Cyphenothrin I X X X Included
Deltamethrin II X X X X Included

– index chemical Fenpropathrin I/ II X

- X X Included
Fenvalerate 2 /Esfenvalerate I/ II X X X X Included

Flucythrinate II X X No PDP detects; not included

in CAG
Fluvalinate II X X X X Included Imiprothrin I

- X X X Included

Metofluthrin I

- X No food use registrations and does not have major residential use registrations;
not included in CAG
Permethrin I X X X X Included

Prallethrin I X X X X Included

Pyrethrins I X X X X Included
Resmethrin I X X X X Included

Sumithrin I X X X X Did not elicit a toxic response
consistent with the common
mechanism at limit dose of 2000 mg/kg ; not included in

CAG

Tefluthrin II X

- X

- No PDP detects and no residential uses; not included

in CAG

Tetramethrin II X X X X Did not elicit a toxic response consistent with the common
mechanism at limit dose of 2000 mg/kg ; not included in

CAG
Tralomethrin 4 II X X X

- Included

1 Refers to all isomeric variations.

2 The registration for Fenvalerate has recently been cancelled and therefore future uses are not expected.

3 Pyrethroids that do not have registered uses were not included in the CAG ( i.e., acrinathrin, barthrin, bioethanomethrin,

cismethrin, cyclethrin, cycloprothrin, dimefluthrin, dimethrin, empenthrin, fenfluthrin, furethrin, profluthrin,

pyresm ethrin, terallethrin, and transfluthrin)

. 4 Due to recent cancellation of uses ( http://www.federalregister.gov/articles/2010/11/17/2010

- 28823/tralomethrin

notice

- of

- receipt

- of

- request

- to

- voluntarily

- cancel

- pesticide

- registrations) , tralomethrin is included i n the CAG, but will not be assessed as part of the cumulative risk assessment

.Pyrethroid Cumulative Risk Assessment

Page 1 4 of 88 

### 4.0 Hazard Assessment/Characterization

As described above, the Agency has designated a CMG for the pyrethroids ( USEPA 2011a ) based on the shared structural similarities and their shared ability to alter VGSCs

. Further

, the Agency has determined which members of the CMG should be quantitatively included in the cumulative risk assessment by designating the CAG with an interim decision to include both Type I and Type IIs together in a single CAG

. Because at this time PBPK models are only available for a small number of pyrethroids ( Permethrin

- Tornero

- Velez et. al. 2007 ; Deltamethrin

- Godin et. al. 2010 ) , t his screening level cumulative assessment relies on the RPF approach using administered dose as the metric for quantifying chemical potency. In the RPF approach, the toxic potency of each chemical in the CAG is determined. One member of the
CAG is selected as the index chemical which is used as the point of reference for standardizing neurobehavioral potency of the other members of the CAG. In the case of the screening level pyrethroid CRA, deltamethrin is being used as the index chemical.

The following discussion describes the Agency’s approach for:

**•** Determination of the appropriate toxicity data for consideration in the CRA

**•** Determination of relative potency factors for each chemical in the CAG;

**•** Selection of the index chemical used as the point of reference to standardize the potency of each pyrethroid/ pyrethrins ;

**•** Establishment of a point of departure used to estimate potential risk for the oral, dermal, and inhalation route s of exposure ; and

**•** Identification of the intra

- species, inter

- spec ies, and FQPA safety factors



### 4. 1 Endpoints and Toxicology Studies

As stated previously, relative potency for cumulative risk assessments should be based,
whene ver possible, on data from the same species and sex to provide a uniform measure of relative potency among the cumulative assessment group ( USEPA 2002 )

. The following section describes the studies evaluated and scientific factors considered in establishing a uniform measure of potency.



### 4. 1 .1 Establishing a Uniform Measu re of Toxicity

4. 1 .1.1 Common Mechanism Endpoint

In cumulative risk assessment, the focus of the hazard characterization is on the common mechanism effect(s) and relevant duration of exposure. Use of in vivo data from a precursor

event is preferred over apical endpoints . However, in the case of pyrethroids, p ractical
methods for evaluating pyrethroid effects on VGSC in vivo are not currently available ( Shafer et

. al. 2005 )

. A dditionally, in vivo biomarkers of toxicity are not available for use in cumulative risk

assessment. D ata from in vitro microelectro array studies ( Losa et. al. 2009 ; Cao et. al. 2011a ) using intact neuronal systems could potentially be used to consider relat ive potency. However,Pyrethroid Cumulative Risk Assessment

Page 15 of 88 using such in vitro studies in the absence of pharmacokinetic data and/or PBPK models to evaluate internal dosimetry of in vitro measures is problematic and would introduce significant uncertainty into the CRA. As such, the Agency has used these in vitro studies as qualitative characterization (See Hazard Characterization, Section 8.1 ) but not for quantitative relative potency calculations.

As recently reviewed ( Wolansky and Harrill 2008 ) and discussed in OPP’s CMG science policy

paper ( USEPA 2011a ) , m any studies have shown that behavioral responses , particularly measured in the rat, can be used as sensitive ind icators of pyrethroid toxicity. Table 4. 1 .1.1 provides a summary of several early behavioral studies with pyrethroids.

Table 4. 1 .1.1

. Behavioral C haracterization of P yrethroid T oxicity of P yrethroids I ncluded in the Proposed CMG from P eer
- R eviewed L iterature

Pyrethroid Verschoyle and Aldridge ( 1980 ) Lawrence and
Casida ( 1982 ) Gammon et

. al

. ( 1981 )

Allethrin; S

- Bioallethrin T I I
Permethrin T I I
Resmethrin T I I Fenpropathrin CS/ T I/II I/II

Esfenvalerate CS II II Cypermethrin CS II II
Deltamethrin CS II II

M ore contemporary studies were designed to detect behavioral changes at a broad range of doses including both lower doses as well as high

- doses. Some of these studies include evaluation of motor activity, coordination, neuromuscul ar response, tremors, acoustic startle response, learning and memory, s o matosensory response, social/sexual interactions and behavior to handling, and the functional observational battery (FOB) ( McDaniel and Moser

1993 ; Sheets et. al. 1994 ; Soderlund et. al. 2002(review) ; Wolansky et. al. 2006 ; Raffaele et. al.

2008 ; Wolansky and Harrill 2008(review) ; Breckenridge et. al. 2009 )

. Given the lack of an in
vivo biomarker for VGSC interaction, measures of behavior in laboratory animal studies are therefore considered appropriate endpoints for extr apolating risk to humans in the pyret hroid screening cumulative risk assessment.

The primary target organ of pyrethroids is the brain and therefore brain tissue concentration could potentially be a useful indicator of internal exposure . However, few studies have examined the brain concentration of pyrethroids and of these, only a small number of pyrethroids are represented (Deltamethrin ( Anadón et. al. 1991 ; Sheets et. al. 1994 ; Kim et. al.

2008 ) ; r esmethrin ( Wh ite et. al. 1976 ; Brodie 1983 ) ; and p ermethrin ( Khanna et. al. 2002 ) )

. Similar limitations prevent the use of blood plasma con centrations as an indicator of toxicity

. The Agency is aware of efforts by the Council for the Advancement of Pyrethroid Human Risk

Assessment ( CAPHRA), a group of pyrethroid registrants and product formulators which is currently developing PBPK models for additional pyrethroids . As those research efforts progress, the Agency may , if appropriate, consider using such data in future revisions to thePyrethroid Cumulative Risk Assessment

Page 16 of 88 CRA. However, in this absence of measures of internal dose for a suffici ent number of pyrethroids, the Agency will use administered dose as the metric for estimating relative
potency.



### 4. 1 .1.2 Experimental Laboratory Studies with Behavioral Measures

The Agency has evaluated multiple sources of data for potential endpoints, including g uideline
and non

- guideline s tudies submitted for pesticide registration (Table 4.1.1.2 )

, data developed by EPA’s Office of Research and Development (ORD)

, and other literature data

. Under FIFRA, toxicology studies in various species ( e.g., dog , mouse, rat and rabbit) are submitted to EPA. For the pyrethroids, toxicology studies in the rat provided the most extensive behavioral data
for all routes and both sexes. Studies in the dog often provide sensitive endpoints (particularly through the observation of tremors) for use in single chemical, aggregate risk assessment. However, studies in the rat are the focus for cumulative risk assessment as rats are most often evaluated in neurotoxicity studies where a broad array of neurobehaviors are eva luated. Specifically, rat neurotoxicity studies may include measures of behavior or response to stimuli such as motor activity, auditory startle response, grip strength, righting ability, in

- cage and handling observations and physiological parameters such as body temperature or catalepsy

, and

, are therefore more likely to detect adverse responses to pyrethroids compared to other guideline studies. Appendix 1 ( Toxicity Data for Screening Level Cumulative Risk Assessment ) provides a summary of guideline studies considered as sources of data for estimating relative
potency the CRA

. Noteworthy literature sources of behavioral studies with pyrethroids include an acute motor activity study ( Wolansky et

. al

. ( 2006 ) and two special FOB stu dies (Herberth (2010) and Weiner et. al. (2009)), which are discussed in detail below.

Table 4. 1 .1.2

. Guideline Studies Evaluated for Potential Cumulative Endpoints
Guideline # Type of Study

870. 3100 90

- day Toxicity Study in Rodents

870.3150 90

- day Toxicity Study in Non

- Rodents

870.3200 21/28 Dermal Toxicity

870.3465 90

- day Inhalation Toxicity

870.3700 Prenatal Developmental Toxicity Study

870.3800 Reproduction and Fertility Effects

870.4100 Chronic Toxicity

870.4200 Carcinogenicity

870.4300 Combined Toxicity/Carcinogenicity

870.6200 Neurotoxicity Screening Batter

870.6300 Developmental Neurotoxicity StudyPyrethroid Cumulative Risk Assessment

Page 17 of 88 

### 4. 1 .1.3 Scientific Considerations in Evaluating Experimental Animal Studies

As noted above, one of the most important components in cumulative hazard assessment is establishing a uniform measure of potency such that the relative rank of each pesticide can be confidently evaluated. There are properties of pyrethroids that must be taken into account when evaluating existing experimental laboratory studies.

**•** Duration of Exposure: The toxicokinetic and toxicodynamic properties of pyrethroids create a narrow window for capturing peak neurotoxic effects; peak effects may last
from on ly a few minutes to over an hour. Pyrethroids are acutely toxic and do not increase in potency with repeated dosing, as demonstrated in guideline studies. The rapid metabolism of pyrethroids is related to the acute nature of the neurotoxic effects.
Oxid ative and hydrolytic enzymes metabolize pyrethroids quickly rendering these pesticides inactive following in vivo exposure ( Anand et. al. 2006 ) . For example, plas ma half

- lives following neurotoxic doses are generally 9

- 15 hours; that is it takes approximately 9

- 15 hours for the plasma concentration of the pyrethroid to be reduced by 50%. Brain tissue half

- lives may be slightly longer, depending on the pyrethroid ( Anadón et. al. 1991 ; Anadón et. al. 1996 ; Anand et. al . 2006 ; Kim et. al. 2008 )

. Plasma
half

- lives generally decrease in a dose

- dependent manner such that l ower doses generally have significantly shorter half

- lives ( < 6 hours ) ( Kim et. al. 2008 )

. Therefore, human exposures which are expected to be orders of magnitude less than the experimental animal studies would be expected to be considerably shorter s till. Because of the rapid clearance rates, pyrethroid concentrations do not accumulate in tissues following subsequent exposures. Thus, given the short temporal nature of pyrethroids, the CRA focuses on acute (24 hour), single dosing studies and involve s exposure periods of only 24 hours.

**•** Timing of behavioral measures: The determination of the time

- to

- peak for behavioral effects and/or target tissue concentration is a critical component of study design for pyrethroids. As shown in Figure 4. 1.1. 3, levels of deltamethrin, a Type II pyrethroid, in brain tissue peak ing 2

- 3 hours after a single oral bolus dose of 3 mg/kg (i.e., minimally neurotoxic effects) , followed by a rapid decrease in concentration ( Godin et. al. 2010 )

. In general, brain concentratio n time course typifies the progression of neurotoxic signs in mammalian species, which appear within 1 hour of oral exposure, peak within 4

- 8 hours, and recover in 12

– 48 hours ( Wolansky and Harrill 2008 ) . If the animals are not examined near these peak tissue concentrations, the potency of the pyrethroid may be
underestimated. As such, for purposes of determining relative potency, the Agency has focused on studies which measured effects at or near the peak time of effect.Pyrethroid Cumulative Risk Assessment

Page 18 of 88 Figure 4. 1 .1. 3

. Model simulation and time course of brain concentration of deltamethrin after an oral dose. Dashed line represents the best

- fit curve to the data points. Adapted from Godin, DeVito et al. ( 2010 )

.

**•** Gavage dosing vs. Feeding: Longer term repetitive dosing studies are typically conducted using dietary administration whereas acute, single dose studies tend to use gavage dosing. The extended exposure period (i.e., over 12 hours during feeding) of dietary administration compared to the bolus dose in capsule and acute studies, results in much lower peak plasma/brain concentrations. As a result, neurotoxicity consistent with the pyrethroid mode of action (MOA) is more commonly observed in acute, gavage studies in rats; thus, such gavage studies a re being used in the CRA.

**•** Vehicle & Volume in Gavage Dosing: Variations in laboratory protocols such as dosing vehicle and volume, lead to altered toxicokinetics and inconsistent results. For example, the Effective Dose (ED 50 ) for delt amethrin in an acute oral motor activity study was 5.1 mg/kg when administered with corn oil, but > 1000 mg/kg when carboxymethylcellulose
was used as the vehicle ( Crofton et. al. 1995 ) . In another acute oral study, bifenthrin was administered at 1 ml/kg or 5 ml/kg in corn oil to rats. The higher dose volume decreased potency by 50% as determined by motor activity and other observational

assays ( Wolansky et. al. 2007 ) . Many of the guideline studies and those available in the literature contain such variations making cross

- study comparisons of pyrethroid potency
difficult. This is shown in Table 4. 1 .1.3 where the vehicle and volume vary considerably across studies making quantitative comparisons challenging

. In contrast to the guideline studies, two studies

- Wolansky et al. (2006) and the special WIL FOB (Herberth 2010;
Weiner et. al. 200 9)

- used a consistent (within study) vehicle and volume for each chemical evaluated. Specifically, Wolansky used 1 ml/kg corn oil for assessing motor activity in 11 pyrethroids and the WIL FOB study used 5 ml/kg corn oil in the evaluation
of 17 pyrethroi ds; thus making the results across multiple pyrethroids comparable
within each of these studies.Pyrethroid Cumulative Risk Assessment

Page 19 of 88 Table 4. 1 .1.3

. Guideline Acute Oral Gavage Studies in the Rat. Pyrethroid 1 MRID Vehicle; Volume
Allethrin; S

- Bioallethrin 44517801 (1% CMC; 10 ml/kg)

Bifenthrin 44862102 No vehicle Cyfluthrin, beta

cyfluthrin 00157802 2% aqueous cremophor EL

lambda

- cyhalothrin 44861510 Corn oil; 10ml/kg

Cypermethrin; z eta

cypermethrin 43152001 Corn Oil , 5% solution, total volume varied by dose group

44962201 No Vehicle
Deltamethrin 44557901 Corn Oil; 5 ml/kg

Esfenvalerate 45228301 (Corn Oil; 10 ml/kg) Fenpropathrin 473745605 Corn oil, 5 mL/kg Fluvalinate, tau 43433901 Corn oil, 10 ml/kg

Permethrin 43046301 Corn Oil, 1

- 30 ml/kg

Pyrethrins 42925801 Corn oil vehicle 5

- 10% pyrethrins, total volume varied by dose group

1 This table captures all of the Guideline acute neurotoxicity studies available for the pyrethroids included in the CAG. Cyphenothrin, imiprothrin, and prallethrin, although included in the CAG, do not have acute neurotoxicity studies.

**•** Consistent evaluation of behavioral endpoints: There is considerable variability among laboratories in scoring procedures used in behavioral measures thus making across laboratory comparisons of behavioral findings challenging. Moreover, assessing rat
be havior can be challenging and is often subjective . T herefore

, it is important for individuals doing such measurements in the laboratory to be well

- trained. Thus, given
the inter

- laboratory variability inherent in behavioral studies, it is desirable for relative potency to be based, to the ext ent possible, on data collected from a single laboratory.



### 4. 1 .1.4 Selection of Critical Study for Estimating Relative Potency

Section 4. 1 .1.3 described desirable characteristics of experimental laboratory studies for use in establishing a uniform measu re of potency for the pyrethroids. Based on a review of the available rat studies, t he Agency has concluded that g uideline studies submitted for pesticide registration do not provide sufficient data for establishing relative potency. As shown in table

4. 1 .1.3, the vehicle and volume used in gavage dosing vary considerably among pyrethroids thus making quantitative comparisons difficult. Moreover, some of these studies do not measure behavioral endpoints at or near the time of peak effect and the behavioral scoring procedures used in these studies var y considerably among laboratories

. Similarly, the differences in study design among many literature studies limits their usefulness for quantifying relative potency across a large number of p yrethroids.

There are, however, t wo recently conducted large literature studies available which provide
acute oral neurobehavioral data appropriate for establishing a uniform measure of potency

.Pyrethroid Cumulative Risk Assessment

Page 20 of 88 **•** Wolansky et

. al

. ( 2006 ) evaluated 1 1 pyr ethroids after a single oral dose using a common vehicle (corn oil) and volume (1 mL/kg) . The Wolansky study measured motor activity at the time of peak effect after exposure. All 12 chemicals were evaluated on the same instrument by the same scientist. Dose

- r esponse relationships were determined using 6

- 11 doses per pyrethroid and 3

- 1 8 rats per dose group , minimizing variability and increasing the confidence in the benchmark dose ( BMD ) estimates determined from this study. I ncreasing exposure to a pyrethroid generally decreased
the rat’s ability to navigate thr ough the maze and therefore reduced motor activity. Motor activity is considered an apical endpoint because it measures alterations in the activity level of a n intact rat. However, a ltered movement patterns can result from any number of adverse outcome pathways resulting in general malaise or altered energy levels, and does not necessarily measure the targeted mechanism of action (i.e., interaction with the VGSC). A lt hough the Wolansky study provides a potential data source for a uniform measure of potency, because of the lack of specific relevance to the common mechanism of action, this study is less desirable for the CRA.

**•** Two special FOB studies conducted by the WIL laboratory and supported by pesticide registrants evaluated 17 pyrethroids in a comprehensive FOB . Twelve were evaluated in an initial study ( Weiner et. al. 2009 ) and 5 more in a second study 2 Herberth 2010 ( )

. T he special FOB WIL study considered beh avioral changes at the time of peak effect, using a common vehicle (corn oil) and volume (5 mL/kg). Each pyrethroid was evaluated by the same technicians who were s pecially trained to recognize pyrethroid toxicity. Therefore potency values generated in the Weiner et

. al

. (2009) and Herberth (2010) studies are directly comparable between studies since a conservative and uniform measure of toxicity was employed in the two special FOB WIL studies. These special
studies examined many behaviors, including ke y ones for evaluat ing neurotoxicity specific to pyrethroids. Unlike motor activity which measures general behavior
patterns

, such as was measured in the Wolansky study, the FOB measures behaviors that are associated with the central and peripheral nervous system. For this reason, the specially designed FOB is more reflective of toxicity directly related to the pyrethroid mode of action and therefore, more appropriate for defining relative potencies related to pyrethroid cumulative risk. It is notable tha t the key parameters identified in the WIL FOB study are directly relevant to the Type I and Type II syndromes. Specifically, hyperthermia tremors, and clonus are important in Type I pyrethroid s and hypothermia, salivation, a nd mobility are key for Type II pyrethroids (see Section 4. 2 and 4. 3 below)

.

Given the strengths of the study design of the special FOB WIL study and the relevance of behavioral measures to pyrethroid to x i c o l ogy, the Agency has determined that for the CRA, the spe c i al FOB WIL study provides the mos t robust source of data for the cumulative risk

assessment. T he Agency has used this study to derive RPFs and P o D s for the index chemical;
the dose

- response analysi s is discussed in d e t ail below.

2 Throughout the remainder of this document, the Weiner et al (2009) and Herbe r th (2010) studies conducted at
the WIL laborat ories will be collectively referred to as the “WIL study.”Pyrethroid Cumulative Risk Assessment

Page 21 of 88 

### 4. 2 WIL FOB Study & Determin in g a Uniform Measure of Potency

4. 2 .1 Introduction

As described in the guidance document for cumulative risk assessment ( USEPA 2002 ) , dose

response modeling is preferred over the use of NOAEL/LOAELs (i.e., no

- or lowest

- observed

adverse

- effect

- levels) for determining relative toxicity potency. NOAELs and LOAELs can be greatl y influenced by study dose selection and dose spacing and thus do not necessarily reflect the relationship between dose and response for a given chemical, nor do they reflect a uniform response across different chemicals. In the present analysis, benchmar k dose (BMD) modeling has been used to determine the toxic potency of the pyrethroids, providing a constant threshold of toxicity for each pyrethroid and more uniform comparisons. EPA’s draft BMD guidance ( USEPA 2000 ) suggests that the central estimate on the BMD provides an appropriate
measure for comparing chemical potency (i.e., RPF ) and that the lower limit on the central estimate (i.e., BMDL) provides an appropriate measure for extrapolating risk (i.e., PoD for the index chemical in a cumulative risk assessment)

. The point of comparison for fou r of the least potent pyrethroids (cyphenothrin, d

- allethrin, imiprothrin, and prallethrin) was based on selecting a dose used in the WIL FOB study (see Section 4.2.5.1 below).

The following sections provide a discussion of the WIL study and how the data from this study have been used by OPP to estimate relative potency for the oral route of exposure.

The WIL study is the most appropriate study available for determination of the pyrethroid
potency because it reflects acute toxicity at the level of the common mechanism (i.e. neurotoxicity)

, standardizes testing conditions for a large number of pyrethroids (i.e. strain, vehicle, dosing volume) , and reflects the most relevant route (oral) and duration (acute) of

exposure

. Furthermore, the WIL dosin g levels are appropriate for determination of P o Ds for this cumulative risk assessment. As indicated in the previous section, pyrethroids are rapidly
metabolized in vivo by oxidative and hydrolytic enzymes. Doses that are sufficiently high enough to cause neurotoxicity overwhelm these clearance mechanisms and interfere with the proper functioning of the sodium channels. Human exposures are expected to be much lower, significantly less likely to saturate the metabolic processes, and therefore less likely to result in neurotoxicity.

As previously noted, t he WIL study is a FOB study including numerous assays designed to quantify neurotoxicity caused by pyrethroids. The FOB is a series of evaluations to deter mine gross neurological function in the animal. In general, observations and short

- duration tests are administered to determine effects on the autonomic, motor, and sensory systems. These simple tests take approximately 5

- 10 minutes after which rats are r eturned to their home cage. The FOB is a noninvasive procedure designed to detect gross functional deficits resulting from exposure to chemicals and to quantify neurotoxic effects. In the WIL study, observations included home cage handling, open fie l d, se nsory, neuromuscular, and physiological
parameters

, conducted at the time of peak effect (2 to 8 hours post

- dose)

. In many cases, thePyrethroid Cumulative Risk Assessment

Page 22 of 88 FOB measures behaviors that are closely associated with toxicity related to the central and peripheral nervous system. Studies have demonstrated the ability of a FOB to describe and differentiate the known pyrethroid syndromes ( McDaniel and Moser 1993 ; Weiner et. al. 2009 )

. F or this reason , the FOB is more reflective of a toxicity directly related to the pyrethroid mode of action and therefore, more appropriate for defining relative potencies related to pyrethroid
cumulative risk.



### 4. 2

. 2 WIL S tudy D esign

Pyrethroids were administered as a single bolus dose via oral gavage using corn oil as the vehicle at 5 ml/kg. Ten adult male Crl:CD(SD)IGS BR rats were used per dose group. Numerous
oral Guideline and literature studies conducted in both males and female rat s indicate similar neurotoxic responses between the sexes , therefore the WIL study was restricted to a single sex

. FOB measurements were taken at the pyrethroids respective time to peak effect for adverse neurological behaviors (as determined in previous pilot studies). Table 4.2.2 provides a summary of pyrethroids examined in the WIL study.

Table 4. 2

. 2. Pyrethroids E xamined at the WIL Laboratory

Pyrethroid Doses (mg/kg) Time

- to

- peak

- effect (hours)

D

- Allethrin b 200, 320, 500 2

S

- Bioallethrin a 150, 200, 300 2
Bifenthrin a 40, 55 8

Beta

- cyfluthrin a 12.5, 25, 45 2
Lambda

- cyhalothrin a 10, 20 4 Cyphenothrin b 60, 100, 160 2 Cypermethrin a 65, 100, 150 4
Deltamethrin a 12.5, 25, 35 4
Esfenvalerate a 15, 25, 50 8 Fenpropathrin a 15, 30 2 Imiprothrin b 900, 1200, 1500 2
Permethrin a 200, 250 4
Prallethrin b 150, 250, 400 2 Pyrethrins 400, 800 4
Resmethrin a 350, 500, 750 4
Tefluthrin a 10, 15 8

a ( Weiner et. al. 2009 )

b ( Herberth 2010 )



### 4. 2.3 Results from the WIL & Severity Scoring

The Agency has reviewed both Weiner et. al. (2009 ) and Herberth ( 2010 ) ; data evaluation records (DERs) for these studies can be found as Appendices 2 and 3 , respectively. In brief, a total of 4 6 neurobehavioral parameters were evaluated including home cage, handling, open field, sensory, neuromuscular and physiological obse rvations

. In the original (Weiner et al, 2009) study, t he FOB data for 11 pyrethroids in addition to pyrethrins were analyzed using principle component analysis to determine dissimilarity/similarity across endpoints andPyrethroid Cumulative Risk Assessment

Page 23 of 88 treatments ( Breckenridge et. al. 2009 )

. T he se pyrethroids were segregated into two composite
factors

, T including the Type I pyrethroids, and CS including the Type II pyrethroids

. This analysis revealed that three endpoints sufficiently described each factor: T was comprised of hyperthermia, tremors, and clonic convulsions

, and CS included hypothermia, salivation, and mobility. These results agreed well with the substantial literature describing the differential toxicity of Types I and II pyrethroids ( Verschoyle and Aldridge 1980 ; Lawrence and Casida 1982 ; Gray 1985 ; Vijverberg and Bercken 1990 )

. Thus from the 4 6 endpoints measured , there were a
total of five endpoint s accounting for the majority of the dose

- response relationships and were capable of differentiating Type I and Type II pyrethroids . This was especially true for the pesticides showing clear differential effects whereas mixed type pyrethr oids ( e.g., esfenvalerate) showed characteristics of both syndromes.

For purposes of dose

- respon se analysis for the CRA, t he raw data from the WIL study for the five endpoints and 12 pesticides identified in the principle component analysis were converted using a severity scoring approach. Moser and colleagues have developed a procedure for normalizing individual data for all measures to a single 1

- to

- 4 scale, where ‘1’ reflects what was observed in control rats, and ‘4’ reflects a rare occurrence in cont rol rats. This approach has been used successfully for delineating profiles of effects of different classes of chemicals including pyrethroids ( Moser 1991 ; McDaniel and Moser 1993 ; Moser et. al. 1995 ; Moser et. al.

1997 )

.

Of the endpoints examined, only body temperature was a continuous variable; a continuous
variable is one where any value may be recorded, including fractions, with no clear cut or sharp breaks between possible values. Tremors and convulsio ns are ordinal variables; a n ordinal variable is a variable whose values are not numerical but have an ordering (e.g. low, medium, and high )

. Body temperature was determined at the time

- to

- peak

- effect. Muscle t remors and
clonic convulsions were observed in both the home cage and open field; the observation with
the most severe effect was used for this analysis. For example, if muscle tremors were
observed in both home cage and open field scenarios, but were more severe in the home cage,
the severity scor e for the home cage tremors was used for the calculation of the severity score

. Clonic convulsions w ere scored in a similar fashion

. Essentially, continuous data (b ody
temperature ) w ere converted on the basis of the control group mean ± multiples of standard deviation, and categorical data were converted based on severity of the original scoring criteria (Table 4. 2.3 ). These scores were then summed for each animal to derive the T and CS composite severity scores.

Each animal was assigned a score from 3 to 12 for both T and CS

. For example, i f an animal did
not demonstrate a dose

- response in any of the 5 critical assays, it would have received a score
of 3 for the T domain (1+1+1 = 3 for each T endpoint) and a 3 for the CS domain (1+1+1=3 for each CS endpoint) . However, if it demonstrated a dose

- response for hyperthermia

, tr e mors , and /or clonus, it would have received a score of up to 12 (depending on the severity of the 3 endpoint responses ) for T, and a score of 3 for CS (due to the lack of response in the hypothermia, salivation, and mobility assays). This example would be characteristic of a Type I pyrethroid. Conversely, an animal given a Type II pyrethroid would most likely have received aPyrethroid Cumulative Risk Assessment

Page 24 of 88 score of 3 for T and up to 12 for CS. A mixed

- type pyrethroid ( e.g. fenpropathrin) would have demonstrated a dose response in tests for both the T and CS domains, resulting in T and CS
scores between 4 and 12.

Table 4. 2

. 3. Conversion of Individual Data to Severity Scores to be Summed into the T or CS Domains. Endpoint Severity conversion Score Domain Body temperature; hyperthermia Within X to X+SD Between (X+SD) and (X+1.5SD) Between (X+1.5SD) and (X+2SD) >(X+2SD) 1

2
3

4 T

Tremors None Slight Moderately coarse Markedly to extremely coarse 1

2
3

4 T

Clonic Convulsions Absent Myoclonus 1

4 T

Body temperature; hypothermia Within X to X

- SD Between (X

- SD) and (X

- 1.5SD) Between (X

- 1.5SD) and (X

- 2SD) >(X

- 2SD) 1

2

3

4 CS

Salivation None Slight

Severe
Profuse 1

2

3

4 CS

Mobility Normal Slightly impaired Moderately impaired Totally impaired 1

2

3

4 CS



### 4. 2

. 4 Variable Coding

As described in section 4. 2 .3

, the principal variables were utilized to calculate composite severity scores. These variables, T and CS, were defined as composites of five outputs measured in the WIL FOB study as follows:

**•** body temperature: T (hyperthermia) and CS (hypothermia)

**•** tremors: T

**•** clonic convulsions: T

**•** excessive salivation: CS

**•** impaired mobility: CS

Continuous data (body temperature) w ere converted on the basis of the control group mean ± multiples of standard deviation, and categorical data were converted based on severity of the original scoring criteria. Before the composite indices were constructed, body temperature was

re

- coded to 2 categorical variables, T and CS. Hyperthermia flags an increase, while hypothermia flags a decrease in body temperature. Each variable is based on the differencePyrethroid Cumulative Risk Assessment

Page 25 of 88 between an observation and the concurrent control means. The data were analyzed in terms of pooled variance of all of the control groups, i.e. the overall control standard deviation.

The resulting T and CS variables were dichotomized as 1 or 0; 1 if T > 4 or CS > 4, and 0 for
individuals with scores of 3 or 4 (i.e., had little or no response to any of the 3 endpoints). The incidents of scores that were assigned a value of 1 were then plotted against administered dose
to achieve a dose

- response curve fro m which the BMDs were calculated. For example, if 4 out of 10 animals tested achieved scores > 4, the fraction affected for the given dose

- group would
be 0.4. FOB scores used in the determination of BMD estimates can be found in Appendix 4

.



### 4. 2.5 Dose

- Re sponse Modeling and Derivation of Benchmark Dose (BMD)

Estimates for Dichotomous Data

Before dose

- response modeling of the 1 2 pesticides in Weiner e t

. al. (200 9 ) , each data set was tested for significant trend ( e.g. , Chi

- Squared Test for Trend in Proportions; Tukey’s Trend Test). Only if a trend was statistically significant was a BMD computed. S tatistical trends were limited to T for Type I pyrethroids and CS for Type II pyrethroids , that is

, trends for T were not statistically significant for Type II pyrethroids and trends were for CS were not significant for Type I pyrethroids

. While all pyrethroids could have resulted in significant trends for both the T and CS variables, this only occurred with the mixed type p yrethroid esf envalerate. T he Agency used the trend (T or CS) that resulted in the lowest BMD estimate (i.e. CS) for determining RPFs.

The BMDs were modeled using a model averaging approach described in Wheeler and Bailer ( 2007 )

. Model averaging is a statistical technique that allows for the incorporation of mode l uncertainty in quantitative risk estimation. The technique averages BMD dose estimates from several models using data derived from dichotomous dose

- response experiments. This calculation is accomplished through a weighted average of multiple dose

- resp onse functions considered in the analysis, where the weights reflect the relation of the fitted function to the observed experimental data. The dose

- response models utilized include the following: logistic, log

- logistic, gamma, multi

- stage, probit, log

- p robit, quantal

- linear, quantal

- quadratic and

W eibull. Due to the limited doses and small samples sizes, this technique was considered more appropriate to account for model uncertainty compared to the Agency’s Benchmark Dose Software (BMDS) that is more co mmonly used to determine BMDs for risk assessment. This model averaging approach has been used in other studies ( Benford et. al. 2010 )

.

The BMD lower bound (BMDL) for the index chemical (deltamethrin) was computed through a parametric bootstrap technique. The BMDL and standard deviation of the natural log

transformed BMD were based on 4999 bootstrap samples. The confidence limits for the relative potency ratios were based on 500 random samples from the ap propriate distributions.

A 20% change from controls was selected as the BMD threshold (i.e., BMD 20 )

. Based on data variance and sample size, the BMD 20 was the most conservative estimate able to predict a significant change from control values. Behavioral data

, such as the WIL FOB data

, tends to have a higher level of variability compared to other biomarkers of toxicity. The BMD 20 used inPyrethroid Cumulative Risk Assessment

Page 26 of 88 this analysis is consistent with threshold levels used in other pyrethroid behavior studies ( Wolansky et. al. 2006 ; Raffaele et. al. 2008 )

.

The model algorithms along with detailed results of model outputs and graphs for each pyrethroid are presented in Appendix 5: BMDs for T and CS f r om WIL FOB Study , April 1, 2009

. Although severity scores were determined f or the pyrethrins and the results analyzed by BMDS software, the lack of a dose

- response precluded the model from fitting a curve for either T or
CS variables (Table 4.2.5 ). Because of the flat response across the dose gro ups and effects which are comparable to the toxicity observed in the other pyrethroids at their BMD 20 s, the Agency is using 800 mg/kg (the highest dose tested) as the point of comparison for pyrethrins.



### 4. 2.5.1 Points of Comparisons for Pyrethroids Studied in Herberth (2010)

As mentioned in section 4. 2 .1, t wo FOB studies were conducted at the WIL laboratories ; t he
first described in Weiner et. al., ( 2009 ) included 1 1 pyrethroids in addition to the pyrethrins

, and the second described in Herberth ( 2010 ) included an additional 7 pyrethroids ; cyphenothrin, imiprothrin, metoflu thrin, prallethrin, sumithrin, tetramethrin, and d

- allethrin. An essential part of any CRA is defining an endpoint for the purpose of a uniform measure of toxicity. A lthough 46 behaviors were observed in the FOB study, the Agency is using the five
parameters identified in the principle component analysis ( Breckenridge et. al. 2009 ) : body
temperature

, tremors

, clonic convulsions , salivation, and mobility

, to determine relative potency factors for purposes of the CRA

. Furthermore, Type I and Type II pyrethroids can be separated base d on the observation of hyperthermia, tremors, or clonus (Type I) or hypothermia, salivation, and mobility (Type II). Since the 7 pyrethroids in the Herbert (2010) study are all structurally Type I pyrethroids, alterations in body temperature , tremors and
clonus can be expected at doses capable of inducing toxicity. Two pyrethroids f rom this study

, tetramethrin and sumithrin, did not demonstrate toxicity at doses of 5,000 mg/kg and so were
not included in the CAG

. Due to minimal use and exposure, metofluthrin was also excluded
from the CRA. The remaining four pyrethroids

, cyphenothrin, imip ro thrin, prallethrin, and d

allethrin , were included in the CAG and require d RPFs. These four pyrethroids are among the least potent members of this class. Because of that, and consistent with the screening nature of this assessment, th e Agency has selected to use the defined doses instead of completing a refined BMD analysis

. In the future, if appropriate, the Agency may determine BMD 20 s for
these. The basis for OPP’s points of comparison is described below.

Imiprothrin : Rats were administered 900, 1200 or 1500 mg/kg . M oderate to severe tremors
were observed in all three dose groups

. Severe salivation was noted in one male in the high

dose group that had tremors. No other clinical findings were noted at any dose. In the o pen field

, 1 rat in the 1200 mg/kg group exhibited slightly impaired mobility, ataxia, moderately coarse tremors and considerable gait impairment. Clonic convulsions were noted for 1 rat in the 900 mg/kg group. In a pilot study, there were no adverse effects noted at any of the administered doses of 300, 500, or 800 mg/kg. Based on the observation of moderate tremors in a single rat, the Agency conservatively, selected a lower dose level, 750 mg/kg, for the point of comparison fo r imiprothrin in the CRA.Pyrethroid Cumulative Risk Assessment

Page 27 of 88 Ta ble 4. 2

. 5 .1 a. FOB Effects Observed in Imiprothrin

- Treated Rats in WIL Study ( Herberth 2010 )
Observations 900 mg/kg 1200 mg/kg 1500 mg/kg

Clinical a Tremors (#rats/#incidences) 1/1 3/3 3/3

Salivation 0 0 1/1

Convulsions 1 0 0 Open Field Mobility & Tremor 0 1 0

a C linical observations were made prior to FOB testing. Observations in all other scenarios were made at the time to peak effec t

Prallethrin : Rats were administered 150, 250, or 400 mg/kg . M oderate tremors and body twitches were noted prior t o the 2

- hour FOB assessment for 1 male each in the 250 and 400 mg/kg groups. Tremors were also observed in the low

- and mid

- dose groups and convulsions in the high dose group during home cage observations. Similar results were observed in the pilot study where f ive rats/group were given 120, 240, or 480 mg/kg. Mild t remors were observed in

one animal in the 120 mg / kg group, and one animal in the 240 mg/kg group had an abnormal gait

. Based on the mild tremors in 1 rat out of 10 , the Agency selected 150 mg/kg as the point of comparison for prallethrin.

a C linical observations were made prior to FOB testing. Observations in all other scenarios were made at the time to peak effect *Indicates a significant change from control group at P>0.05.

Cyphenothrin :

a C linical observations were made prior to FOB testing. Observations in all other scenarios were made at the time to peak effect Rats were administered 60, 100, or 160 mg/kg . Two males in the 160 mg/kg group were found dead on study day 1. These deaths were considered to be test substance

related as these males had multiple signs of overt toxicity during the 2

- hour FOB evaluation. All other males in the 160 mg/kg group survived to the scheduled euthanasia. All males in the 60 and 100 mg/kg c yphenothrin groups survived to the scheduled euthanasia . Similar to prallethrin, tremors were also observed in 1 rat in the low

- dose group

. The Agency selected 60 mg/kg from the definitive study for a point of comparison based on mild tremors in 1 rat out of

10.

*Indicates a significant change from control group at P>0.05. Table 4. 2

. 5 .1 b. FOB Effects Observed in Prallethrin

- Treated Rats in WIL Study ( Herberth 2010 )
Observations 150 mg/kg 250 mg/kg 400 mg/kg

Clinical a Tremors (#rats/#incidences) 0 1/1 1/1
Home Cage T remors 1 3 0
Convulsions 0 0 1
Physiological Body Temperature 38.4±0.63 37.8±0.48 37

. 2±0.61 *

Table 4. 2

. 5 .1 c. FOB Effects Observed in Cyphenothrin

- Treated Rats in WIL Study ( Herberth 2010 )
Observations 60 mg/kg 100 mg/kg 160 mg/kg

Clinical a Tremors (#rats/#incidences) 0 1/1 2/2

Deaths 0 0 2 Home Cage T remors 1 1 5 *
Convulsions 0 0 2 Open Mobility 0 1 5 *
Convulsions 0 1 1

Tremor 0 1 8 *Pyrethroid Cumulative Risk Assessment

Page 28 of 88 D

- A llethrin : Rats were administered 200

, 32 0, or 50 0 mg/kg . Four males were found dead between 2 hours and 3 hours following dose administration, or on study day 1 (1 in the mid

and 3 in the high

- dose group s ) . Moderate tremors were noted for 1 male in the 500 mg/kg group at 1 hour 20 minutes following dose administration. Slight or moderately course tremors were noted in 2, 4, and 8 males in the low

- , mid

- , and high

- dose groups, respectively, in the home cage . T he most prevalent finding in the open field included slightly impaired mobility, convulsions, slight to moderate tremors and slight gait impairment.

D

- allethrin and s

- bioallethrin are both enrichments of the pyrethroid allethrin. As noted in section 4.5, a BMD 20 of 135 mg/kg was calculated for s

- bioallethrin. A lthough available as separate commercial products, d

- a llethrin and s

- bioallethrin contain similar amounts of the d

trans isomer of the chrysanthemic acid, 80 and >90%, respectively. The greater concentrat ion
of the d

- trans isomer in the s

- bioallethrin resulted in slightly greater toxicity compared to d

allethrin at a shared dose of 200 mg/kg. For example, in the open field, convulsions and
tremors were observed in 5 and 6 rats out of 10 for s

- bioall e thrin but were limited to 2 and 2
out of 10 for d

- allethrin

. Given the similarity of their compositions and in lieu of selecting a dose from Herbert (2010) for d

- allethrin, the Agency is using 135 mg/kg (the BMD 20 for s

bioallethrin) for determination of the relative potency factor of d

- allethrin.

a C linical observations were made prior to FOB testing. Observations in all other scenarios were made at the time to peak effect *Indicates a significant change from control group at P>0.05.



### 4. 3 R outes and Duration of Exposure for Potency Determination

4. 3

. 1 Routes of Exposure

Humans may be exposed to pyrethroids through their diet (food and drinking water) and in and around residences, schools, commercial buildings, etc

. via the oral, dermal

, and inhalation routes of exposure. Therefore, the potency of pyrethroids needs to be determined for all three routes of exposure 3

3 More detail related to exposure can be found in Sections 5.0 and 6.0 . Dermal and inhalation assessments are required for some pyrethroids; however, they generally do not significantly contribut e to the overall risk picture. Oral exposure is the route of exposure of greatest concern with respect to pyrethroid toxicity for the screening level cumulative assessment

. Table 4. 2

. 5 .1 d. FOB Effects Observed in D

- A llethrin

- Treated Rats in WIL Study ( Herberth 2010 )
Observations 200 mg/kg 320 mg/kg 500 mg/kg

Clinical a Tremors (#rats/#incidences) 0 1/1 1/1

Found Dead 0 1 3 Home Cage T remors 2 4 8*
Convulsions 0 0 2 Open Field Mobility 0 1 4
Convulsion s 2 4 7

Tremor 2 4 8Pyrethroid Cumulative Risk Assessment

Page 29 of 88 

### 4. 3 .1.1 Oral

Oral relative potency values were needed for all pyrethroid pesticid es included in the CAG because of potential dietary exposures from food and drinking water and hand to mouth exposures associated with residential/non

- occupational uses. The Agency has determined that the WIL study is the most appropriate study available for determination of the pyrethroid BMDs
via the oral route because it reflects acute toxicity at the level of the common mechanism (i.e. neurotoxicity due to alterations of the VGSC ), standardizes testing conditions for a large number of pyrethroids (i.e. strain, vehicle, dosing volume), and reflects the most relevant duration (acute)

.



### 4. 3 .1.2 Dermal and Inhalation

Compared to the database for oral toxicity studies, the number of inhalation and dermal studies examining neurotoxic effect s consistent with the pyrethroid common mechanism is
much smaller. Several in vivo dermal studies are available to evaluate pyrethroid toxicity. However, these studies do not evaluate the full range of behavioral endpoints needed to assess pyrethroid toxicity, nor do they establish critical time

- to peak

- effect windows. There are even fewer inhalation studies available for the determination of pyrethroid toxicity compared to the dermal studies, and these too lack critical endpoint evaluation and appropriate time

- to

- peak

ef fect determination. Furthermore, the Agency’s limited ability to predict the impact of route

specific pharmacokinetics precludes the extrapolation of estimating RPFs from oral, dermal, and inhalation exposures. As PBPK models are further developed for th is class of pesticides,
limitations such as route

- to

- route extrapolation may be overcome. However, at the current time limitations in methodology and lack of coverage for all pyrethroids preclude the inclusion
of dermal and inhalation studies in the calcu lation of the RPFs. As such, the Agency is assuming that the relative rank estimated for oral exposure applies to both the dermal and inhalation

routes.

In lieu of determining BMDs for dermal and inhalation routes, the Agency is using the BMDs
determined from oral studies and using a 5% dermal absorption factor and assuming inhalation toxicity is equivalent to oral toxicity . Pyrethroid dermal absorption estimates used in single
chemical risk assessment for the pyrethroids include d in the CMG range from 0.2 to 33%. Dermal absorption e stimates greater than 5% are either based on structural similarity which entails a high level of uncertainty and are therefore very conservative, or measurements of total skin absorption which is also highly conservative since pyrethroids bound to the upper dermis layers are not likely to be absorbed into the body. Furthermore

, approximately half of these estimates are based on systemic toxicity, such as decreased body weights, decreased food consumpt ion, or as a weight of evidence from the database, and therefore are not consistent with the pyrethroid common mechanism being used for the CRA. Those studies
based on neurotoxic effects are not examined in a consistent manner and therefore such in vivo
d ermal studies are not appropriate for the determination of BMDs for the purposes of the CRA.

Estimates ≤ 5% are based on potency comparisons between oral and dermal studies within the same rat strain, direct measures of in vitro skin penetration ( Hughes and Edwards 2010 ) , orPyrethroid Cumulative Risk Assessment

Page 30 of 88 penetration rates based on lower dermis levels of skin that are more likely to be absorbed by the body. Since these lower estimates are more robust and contain significantly less uncertainty, the Agenc y is confident that an estimate of 5% absorption is protective for human

exposures.

The Agency has guideline inhalation studies for 10 pyrethroids which are included in the CAG

. Of these 10, the effects observed in the studies for five of these are e ither based on route of entry effects or other more generalized toxic effects such as decreased body weights

. For the remaining five pyrethroids

, s

- bioallethrin, cyfluthrin, imiprothrin, lambda

- cyhalothrin, and permethrin, the effect seen in the inhalation studies are based on adverse neurotoxic effects including convulsions, tremors, and vocalizations during handling

. Although these effects are consistent with the recognized pyrethroid common mechanism , these studies are lacking in

consistent e valuation and scoring of neurotoxic behaviors, determination of the appropriate

time

- to

- peak

- exposure, and consistent exposure techniques, and thus are not appropriate for estimating relative potency.



### 4. 4 Index Chemical

The cumulative risk assessment guidance document ( USEPA 2002 ) stat es that the index chemical should be selected based on the availability of high quality dose

- response data (preferably in each route of interest) for the common mechanism endpoint and that it acts toxicologically similar to other members of the common mech anism group. High quality dose

response data allow the calculation of points of departures (P o D) with greater confidence

, b ecause the PoDs for the index chemical are used to extrapolate risk to the exposure levels anticipated in the human population and any error or uncertainty in an index chemical’s PoD
value will be carried forward in the cumulative risk estimates.



### 4. 4 .1 Candidates for Index Chemical

In previous cumulative assessments the Agency has typically evaluated those chemicals in the
CAG with high quality data relevant for the CMG endpoint(s) for the oral, dermal, and inhalation routes of exposure. In the case of the pyrethroids, a complete database including dermal, oral, and inhalation studies measuring pyrethroid

- specific neur otoxicity at the time

- to

peak

- effect is not available for any single pyrethroid. Furthermore, although d e rmal and
inhalation assessments are being conducted f or some pyrethroids

, they generally do not significantly contribute to the overall risk picture ; therefo re the focus of this CRA is the oral route of exposure

. O ral exposure is the route of greatest concern with respect to pyrethroid toxicity for th is screening level cumulative assessment and the source of the most robust dose response data for purposes of deriving PODs

. T he WIL study provides the most robust oral FOB data from which to compare the pyrethroid chemicals (See section 4. 2 ) . Therefore, for this screening level CRA the Agency is relying on the chemicals included in the oral WIL study for
determination of candidates for the i ndex c hemical.Pyrethroid Cumulative Risk Assessment

Page 31 of 88 In addition to considering the robustness of the toxicity database, the selection of the index chemical must also consider the pe rtinent duration of exposure . As previ ously discussed, the

CRA assess es exposures over a 24 hour period (i.e. acute exposures) ; therefore it is important that the index chemical have a robust database reflecting this exposure duration

.

P ermethrin and d eltamethrin stand out as having the most robust database of guideline and
literature studies. For example, multiple studies on deltamethrin and/or permethrin have been identified examining in vivo neurotoxicity

, in vitro sodium channel interaction, metabolism, pharmacokinetic s following multiple routes of administration ( oral, dermal, intravenous, intercerebral, etc.) and PBPK modeling. Thus, deltamethrin and permethrin are both strong
candidates for selection as the ind ex chemical.

T he deltamethrin P o D derived from the FOB data is of sufficiently high quality to minimize error or uncertainty in the cumulative risk estimates. In the WIL study, permethrin was only tested with two doses which are narrowly spaced wherea s deltamethrin was tested with three doses well spaced to cover the low to high dose range. As such, t here is greater variability around the BMD central estimate for permethrin compared to deltamethrin based on the distance of the BMDL (lower confidence l imit) from the central estimate. Specifically , the BMD and BMDL estimates for permethrin are 155.5 and 73 mg/kg, compared to the deltamethrin BMD and BMDL estimates of 14.5 and 10.5 mg/kg. Therefore, the Agency has selected deltamethrin as
the index chemical in the CRA

.



### 4. 5 Relative Potency Estimates & Points of Departure for the Index Chemical Several key literature studies supporting the use of deltamethrin
as the index chemical are listed in Appendix 6

. This list of literature is not exhaustive but it does
include the most salient studies cover ing a number of areas of deltamethrin research and it
includes key seminal studies that are cited most often.



### 4. 5 .1 Relative Potency Factors

In this CRA, t he Agency is quantifying cumulative risk to the pyrethroids using BMDs derived from the WIL study to calculat e RPFs . Deltamethrin is being used as the index chemical. The
RPFs for the CAG in this pyrethroid screening level cumulative are shown in Table 4. 5.1

. They are determined by dividing the chemical

- specific BMD 20 by the BMD 20 of th e index chemical,
deltamethrin . Calculations for the BMDs are described in Section 4. 2

. Twelve of the 1 5 pyrethroids result in equal to or lower relative potency estimates comp ared to deltamethrin. Bifenthrin, cyfluthrin, and tau

- f luvalinate result in similar relative potency as deltamethrin while
lambda

- c yhalothrin resulted in slightly greater potency than deltamethrin.Pyrethroid Cumulative Risk Assessment

Page 32 of 88 Table 4. 5

. 1. Relative Potency Estimates for Pyrethroids Included in the Screening Level Cumulative Risk Assessment Pyrethroid Oral BMD 20 Oral RPF b ,d

Allethrin c 135 0.11
Bifenthrin 14.3 1.01 Cyfluthrin 12.6 1.15
Lambda

- Cyhalothrin 8.9 1.63 Cyphenothrin 100 a 0.15 Cypermethrin 76.3 0.19
Deltamethrin 14.5 1.0
Esfenvalerate 40.5 0.36 Fenpropathrin 29 0.50

Tau

- Fluvalinate 14.5 1.0 Imiprothrin 750 a 0.02

Permethrin 156 0.09
Prallethrin 150 a 0.10 Pyrethrins 800 a 0.02
Resmethrin 291 0.05

a Values estimated from studies ; these values were not calculated using BMD

. See Section 4.2

b RPF = BMD 20 of Index Chemical (e.g., deltamethrin) / Pyrethroid BMD 20 ; For example: Allethrin RPF=14.5/135=0.11

c Includes the isomeric enrichments S

- Bioallethrin and D

- Allethrin

d RPFs for Dermal and Inhalation exposures are based on oral BMD; 5% absorption values applied to dermal assessments and inhalation is considered equivale nt to the oral route



### 4. 5 .2 Points of Departure

The deltamethrin BMD 20 is derived from oral data and is being applied to all three routes of

exposure : oral, dermal, and inhalation. As with any risk assessment that relies on BMD analysis,
the PoD is the lower confidence interval used to mark the beginning of extrapolation to determine risk associated with human exposures. The 95% lower confidence interval for the

BMD 20 , the BMDL 20 , of deltamethrin is 11 mg/kg (Figure 4. 5 .2)

.Pyrethroid Cumulative Risk Assessment

Page 33 of 88 Figure 4.5

. 2. BMD 20 and , BMDL 20, for FOB changes of D eltamethrin



### 4. 6 FQPA Safety Factor for Protection of Infants & Children

The FQPA (1996) instructs EPA, in making its “reasonable certainty of no harm” finding, that in “the case of threshold effects, an additional tenfold margin of safety for the pesticide chemical residue and other sources of exposure shall be applied for infants and children, to take into

account potential pre

- and post

- natal toxicity and completeness of data with respect to exposure and toxicity to infants and children .” Section 408 (b)(2)(C) further states that “the Administrator may use a different margin of safety for the pesticide chemical residue only if, on the basis of reliable data, such margin will be safe for infants and children.”

The Agency typically determ ines the appropriate FQPA safety factor on a chemical

- by

- chemical basis. However, there are a number of similarities between the pyrethroids (e.g., relative potency, structure, and pharmacokinetics) w hich support the conclusion that a single FQPA safety f actor is appropriate for the entire class. Based on reliable data, EPA has concluded that a safety factor less than 10X is appropriate for the pyrethroid chemicals. The Agency is reducing the FQPA Safety Factor to 1X for adults, including pregnant female s, and children greater than 6 years of age ( USEPA 2011b ) . However, the Agency is retaining a 3X FQPA Safety Factor for children from birth to 6 years of age. This conclusion is based on a wide range of information on pyrethroids that includes the exposure profile for this class of pesticides, PBPK models, and in vitro and in vivo data. The scientific information that support s the reduction of the FQPA safety factor can be found in Re

- Evaluation of the FQPA Safety Factor for Pyrethroid
Pesticides ( USEPA 2011b ) and is summarized below:

**•** Based on the available data and supporting evidence, the 10X FQPA safety factor will be reduced to 1X for all populations greater than 6 years of age, including women of child BMD L BMDPyrethroid Cumulative Risk Assessment

Page 34 of 88 bearing age. This is due to the absence of pre

- natal sensitivity observed in 76 guideline studies for 24 pyrethroids and supporting scientific literature.

**•** For exposures from birth to < 6 years of age, the Agency will retain a 3X safety factor due to 1) age

- dependent pharmacokinetics, supported by rat PBPK model predictions of

a 3

- fold increase of pyrethroid concentration in juvenile brain compared to adults; 2) in
vitro pharmacodynamic data and in vivo data indicating similar responses between adult and juvenile rats at low dose s ; and 3) data indicating that the rat is a conservative model compared to the human based on species

- specific pharmacodynamics of homologous
sodium channel isofo rms.

**•** Based on pharmacokinetic data, there is evidence that indicates an increase in sensitivity to pyrethroids of the young compared to adults. These differences are largely attributed to the ability of the adults and juveniles to metabolize pyrethroids . The available PK data is primarily based on experiments with deltamethrin, one of the more potent pyrethroids. Data has shown the rate of in vitro metabolism of deltamethrin by plasma carboxyesterases, hepatic carboxyesterases, and hepatic microsomes a re at least 6 times higher for post

- natal day (PND) 90 rats compared to PND 10 rats ( Anand et.
al. 2006 ) . As a consequence, higher internal doses overwhelm the clearance

mec hanisms in juveniles but because adults have greater enzyme activity, they are able to tolerate higher doses prior to the onset of toxicity. PBPK models have predicted, compared to adult rats (i.e., 90

- days old), equivalent brain concentrations of
deltame thrin would be achieved with a 3.8X fold lower oral dose in 10

- day old rats and
2.5X lower dose in 21

- day old rats ( Tornero

- Velez et. al. 2010 ) . The difference between

a 3.8

- and a 2.5

- fold dose is within background variability of the PBPK model and therefore the Agency approximates a 3

- fold difference between adult and juvenile rats. Since there are no similar age

- dependent PBPK models available for humans, the Agency cannot make any direct estimates of h uman infant brain concentrations following an exposure to pyrethroids . Therefore, t he Agency has to rely on extrapolations from rodent studies. Comparisons between lifestages in the rat and human are difficult to make because the ontogeny of the brain de velopment and metabolizing enzymes are not an exact match. However, 11

- day old rats are considered to be equivalent in terms of development to newborn humans and 17

- day old rats are believed to be developmentally equivalent to human toddlers 3 to 6 years of age ( Davision and Dobbing 1966 ; Dobbing and Smart 1974 ; Benjamins and McKhann 1981 )

.

**•** In part, the Agency is reducing the FQPA factor because available data do not indicate

any age

- related differences in the pharmacodynamics through interaction with VGSC s. For example

, in a direct comparison of a homologous rat and human sodium channel isoform, NaV1.3, Tan and Soderlund ( 2009 ) found the rat isoform was 4

- fold m ore sensitive than the equivalent human sodium channel to the pyrethroid tefluthrin, suggesting the rat is a highly sensitive model and extrapolations from the rat would be protective of human health.Pyrethroid Cumulative Risk Assessment

Page 35 of 88 **•** The population of greatest concern to the Agency for pyrethroid exposure is children from birth to <6 years of age. Pyrethroids have a wide variety of uses, including agricultural and residential scenarios. Despite the widespread use on food crops, residue levels in processed or whole foods, as determined by the USDA Pesticide Data Program, are generally low. Furthermore, pyrethroids are practically insoluble in water, minimizing water exposure. With respect to residential and occupational exposure scenarios, pyrethroids have low vapor pressure and are p oorly absorbed dermally ( Hughes and Edwards 2010 ) . As such, the exposure assumptions made in this screening level assessment are conservative and protective of human health.

T he Agency is expecting additional in vitro and in vivo data that will further inform the science behind the decision to reduce the FQPA factor. In 2010, the Agency requested proposals for study protocols which could identify and quanti fy potential juvenile sensitivity ( USEPA 2010 )

. There was a single response from the P yrethrin and Pyrethroids Working Group (P PTWG ), a conglomerate of pyrethroid registrants . The PPTWG protocol was reviewed during a July 2010

FIFRA SAP meeting 4



### 4. 7 Incorporation of Uncertainty Factors/Extrapolation Factors and the Target Margin of Exposure . Based on comments from the SAP, the initial study proposal was refined. At present time, pesticide registrants and product formulators ( Council for the Advancement of Pyrethroid Human Ri sk Assessment (CAPHRA) are i) conducting in vitro studies demonstrating
the interaction of pyrethroids endogenously expressed rat and human VGSCs in Xen op us oocytes; ii) conducting in vitro studies demonstrating interaction of pyrethroids in rat
neurolemma cells; iii) developing rat and human PBPK models, including additional pharmacokinetic data; and iv) conducting in vivo behavioral testing using auditory startle testing in rats. As more data for individual pyrethroids become available

, the Agency will
determine whether re

- evaluation of the age

- related sensitivity of pyrethroids is appropriate.

In general, when performing a cumulative risk assessment using a RPF approach, as is being done with the pyrethroids, uncertainty and extrapolation factors can be incorporated into the risk assessment in two different ways: 1) adjustment of the chemical

- specific RPF; or 2) incorporation into the targe t Margin of Exposure (MOE) . For the pyrethroids, the inter

- species,
intra

- speci es , and FQPA safety factor were all incorporated into the target MOE.

T he magnitude of the uncertainty and extrapolation factors is the same for each member of the
common mech anism group for the pyrethroid CRA . As described in detail earlier, the FQPA
factor has been reduced to 3 X for every pyrethroid for the subgroups of children six years old and younger and to 1X for all other subgroups

. However, d ata are not available to reduce the

10X inter

- species or 10X intra

- species factor. Therefore, the 10 X is retained for both of these
factors. As such, the target MOE s for the pyrethroid CRA are listed in Table 4. 7

.

4 http://www.epa.gov/scipoly/sap/meetings/2010/072310meeting.htmlPyrethroid Cumulative Risk Assessment

Page 36 of 88 As indicated in the previous section, the Agency is expecting additional data and PBPK models

. PBPK models are able to address age

- and species

- specific pharmacokinetics that are key to extrapolating human health risks from rodent models . For example, Go din et. al. ( 2010 ) predi ct ed the concentrations of deltamethrin in the adult human brain based on studies in the

rat and Tornero. et al. ( 2010 ) predict ed deltamethrin concentrations in the brains of rats from

PND 10 up to PND 90

. These Agency models form the basis for newer models currently being developed by CAPHRA for several additional pyrethroids. As the models become available to the Agency, further adjustments to the FQPA and interspecies factors will be considered during
fu ture CRA revisions

.

Table 4. 7 FQPA Safety Factors for Populations Relevant to Human Health Risk Assessments Population FQPA Inter

- species

Factor Intra

- species

Factor Target MOE

Children 0 to 6 years 3 10 10 300 Children > 6 years 1 10 10 100
Females 13+ 1 10 10 100
Adults 1 10 10 100



### 4. 8 Dose Additivity

A key assumption of the RPF method is dose

- additivity. For pyrethroids, dose

- additivity implies multiple pyrethroids can interact with the VGSC simultaneously, and the overall toxic response will be a summation of all the individual pyrethroids. For example, if deltamethrin and permethrin were administered at equipotent doses, the measured response would be double compared to the administration of either pyrethroid by itself

. Dose

- addition has recently been
demonstrated in in vivo and in vitro studies. Wolanksy et. al. ( 2009 ) used a mixture of 11 pyrethroids (both Type I and II) and the same testing paradigm used in single

- compound assays to test the hypothesis that cumulative neurotoxic effects of pyrethroid mixtures can be predicted using the default dose

- addition theory. W hen subthreshold doses of individual
chemicals w ere com bined in mixtures, significant dose

- related decreases in motor activity were observed; there was no departure from the predicted dose

- additive curve. This study presents
the first in vivo evidence on pyrethroid cumulative effects supporting the default as sumption of
dose addition. Using the same mixture of 11 pyrethroids, Cao et. al. ( 2011a ) measured Na+
influx in primary cultures of intact mammalian cerebrocortical neurons. W hen all 11 pyrethroids were present at an equimolar mixing ratio, their actions on Na+ influx were
consistent with a dose

- additive model. While motor activity is an indirect measure of the common mechanism (i.e. interaction with VGSC), the measurement of Na+ influx at the neuronal level provides more definitive evidence of dose

- addition at the level of the common
mechanism.

Furthermore, Scollon et. al. ( 2009 ) compared the rate of metabolism of the cis

- and trans

isomers of permethrin in hepatic microsomal incubations separate ly and in a mixture. The
metabolism of trans

- permethrin was reduced when incubated with its diasteriomer, cis

permethrin in both rat and human hepatic microsomes incubations. Since both isomers are
metaboli zed by the same o xidative P450 enzymes

, (CYP2C6 and CYP2C11)

, substratePyrethroid Cumulative Risk Assessment

Page 37 of 88 competition may have contributed to the difference in metabolic rate. While this potential

interaction in metabolism does not necessarily result in dose

- additivity, it may contribute and
should be con sidered when modeling pyrethroid pharmacokinetics. OPP will continue to
monitor and evaluate in vivo and in vitro studies evaluating dose

- addition of pyrethroids as they
become available.

In summary, given the current state of the science with respect to pyrethroid mixtures, the assumption of dose additivity is both reasonable and appropriate.



### 5.0 Dietary Cumulative Exposure and Risk Assessment/Characterization

This section discusses the cumulative estimated risk associated with the food and drinking water exposure pathways. A n overview of the inputs and methodology for the dietary
assessment is included here. D etailed information on conducting a cumulative dietary risk

assessment is available in the Revised N

- Methyl Carbamate Cumulative Risk Assessm ent , US EPA, September 24, 2007, pp. 58

– 82.

It should be noted that while the methodology developed and implemented in the assessment of the cumulative risks for the organophosphate and N

- methyl carbamates was closely followed for the pyrethroids, in l ight of the screening level nature of this assessment, some conservative assumptions were made . Inclusion of those conservative assumptions did not result in dietary risks of concern; therefore, additional refinements were not required at this time.



### 5

. 1 Food Exposure Pathway

As with previous cumulative assessments released by the Agency, the data for this pathway are developed from two primary sources: dietary consumption data collected by USDA’s Continuing Survey of Food Intakes by Individuals (CSFII) and pesticide residue monitoring data collected by the USDA Pesticide Data Program (PDP).



### 5 .1.1 Dietary Consumption Data

The reliability of the food component of this assessment is supported by the use of the food consumption data from the USDA’s Cont inuing Survey of Food Intakes by Individuals (CSFII

1994

- 1996/1998). The CSFII surveyed more than 20,000 individuals over two non

- consecutive days and provides a detailed representation of the food consumption patterns of the U.S public across all age gro ups, during all times of the year, and across 50 states. Thus, the Agency has confidence that the consumption estimates for food are well established and consequently support reasonable risk estimates for the U.S. population.Pyrethroid Cumulative Risk Assessment

Page 38 of 88 

### 5.1.2 Pesticide Residue Data

As with previous CRAs, the exposure estimates for food are based on residue monitoring data from the USDA’s Pesticide Data Program (PDP). PDP data collected from 2003 through the
most recent data available in 2009 were incorporated in the pyrethro id screening level

assessment. While additional years of data are available, prior to 2003, PDP did not analyze for all registe red pyrethroids. The PDP data provide a reliable estimate of pesticide residues in the majority of foods, with care taken to sa mple foods with high consumption or foods which are likely to have the highest residues, including important children’s foods. The PDP data were either used directly or indirectly through the use of commodity surrogates. That is, for food not
monitored i n PDP, similar commodities that are measured by PDP served as surrogate data sources. This approach is consistent with the approach taken on previous CRAs and is considered to be reasonable given that it is based on the concept that families of commoditie s with similar cultural practices and insect pests are likely to have similar pesticide use patterns and residue levels. Additionally, PDP data provide direct measures of co

- occurrence of the pyrethroid pesticides in the same samples. Consistent with pri or practice for the organophosphate (OP) and N

- methyl carbamate (NMC) pesticide cumulative assessments, PDP samples with non

- detectable residues were treated in this assessment as “zero” values. Sensitivity analysis conducted for the OPs and NMC pesticide s has determined that this approach for acute dietary assessments does not significantly underestimate exposures at the upper percentiles.



### 5 .1.3 Pyrethroid Pesticides Included in the Dietary Risk Assessment

The pyrethroids with registered agricultural uses on human feed items are summarized in Table

5 .1.3, below, along with their relative potency factors (RPFs). It is important to note that not all pyrethroids with registered food

- uses were quantitatively in cluded in this screening level assessment. As was previously noted and is captured in the CRA methodology, a pyrethroid
with a relative potency that significantly lower than that of the index chemical was not included
in the CAG since that specific chemic al is unlikely to have an impact on the estimated cumulative risk. Further, food

- use pesticides for which there are no detectable residues in the PDP monitoring data are not included in the assessment as there is not a likelihood of significant exposure.Pyrethroid Cumulative Risk Assessment

Page 39 of 88 1 Refers to all isomeric variations.

In contrast to prior CRAs, processing factors were not included in this screening level

assessment , that is, the processing factor was set to “1” which indicates there is no concentration or reduction from processing. For processed commodities monitored directly by PDP, the residue values found in the monitored samples were d irectly used in the assessment. For those processed commodities which were not directly sampled, the monitored value from the raw agricultural commodity (RAC) or its commodity surrogate was used and the processing factor was set to “1”. This approach is considered reasonable and unlikely to underestimate risk since a review of tolerances (maximum allowed legal residues) for these commodities indicated that separate, higher tolerances were not required for the associated processed commodity. In other word s, the tolerance for the RAC would also cover the residues found in the processed commodities supporting a lack of concentration of residues in the processed commodity. Further, no use of reduction factors was included in this assessment. Refining this

a ssessment to include reduction factors (i.e., cooking factors, process reduction factors) for processed commodities for which RAC residue values were used, would only reduce the estimated exposure values. Table 5.1.3. Food Use Pyrethroids Considered in the Quantitative Screening Level CRA

Chemical

Name 1 Included Quantitatively in Screening Level Assessment/Comments RPF Index
Chemical

POD UF FQPA

SF CRA Target MOE

Allethrin Included 0.11 100 3

100 adults
300 children Bifenthrin Included 1.01 100 3

Cyfluthrin Included 1.15 100 3

Cyhalothrin Included 1.63 100 3

Cypermethrin Included 0.19 100 3

Cyphenothrin Included 0.15 100 3

Deltamethrin Included 1.0 11 mg/kg/day 100 3

Fenpropathrin Included 0.5 100 3

Fenvaler ate/
Esfenvalerate Included 0.36 100 3

Flucythrinate No detects in PDP; therefore not included quantitatively in the CRA

Fluvalinate Included 1 100 3 100 adults
300 children Imipro thrin Included 0.02 100 3

Permethrin Included 0.09 100 3

Prallethrin Included 0.1 100 3 100 adults
300 children Pyrethrins Included 0.02 100 3

Resmethrin Included 0.05 100 3

Sumi thrin Did not produce any signs of toxicity; therefore not included quantitatively in the CRA

Tefluthrin No detects in PDP; therefore not included quantitatively in the CRA

Tetramethrin Did not produce any signs of toxicity; therefore not included quantitatively in the CRA

Tralomethrin No detects in PDP; therefore not included quantitatively in the CRAPyrethroid Cumulative Risk Assessment

Page 40 of 88 

### 5.1.4 Food Commodities Included in the Dietary Ri sk Assessment

The universe of foods included in the cumulative dietary exposure assessment is defined by the

USDA CSFII 1994

- 96/1998. The CSFII food diary information is expressed in terms of food as consumed ( e.g. , pizza, apple pie, lasagna, etc.). Thes e foods, as reported in CSFII diaries, are
converted to food commodities ( e.g. , tomatoes, milk, wheat flour, beef, apples, etc.) using standard recipes. The recipe information used to break down the foods was developed jointly by EPA and USDA and is one mo dule in the EPA’s Food Commodity Intake (FCID) database.

For this screening level assessment pesticide residue values were translated such that all major commodities contained in the Agency dietary exposure model, Dietary Exposure Evaluation
Model

- Food Commodity Index Database (DEEMFCIDTM) , were assigned residue values. While monitoring data are not available for ever y commodity in DEEM, major foods are sampled by PDP and the residue values for those samples were t ranslated to similar commodities. For example orange data was translated to limes. Translations were made based on the similarity of the commodities under the Agency’s crop grouping scheme codified in the 40CFR.
Translations were made regardless of regi stered use patterns. For example, banana residue values were translated to plantains without verification that there is a pyrethroid registered on plantains. In a more refined CRA, those crops without pyrethroid registered uses would be assigned “zero” v alues; therefore, this approach would only be expected to result in an
overestimate of risk.

Despite the conservative assumptions with regard to processing factors and pyrethroid commodity registrations, by using the PDP monitoring data, the food compone nt of the screening level pyrethroid CRA is considered to be refined and to provide reasonable estimates of the distribution of exposures across the U.S.



### 5 .2 Drinking Water Pathway

As a class of chemicals, the pyrethroids have low solubility in water and a high affinity to bind to soils. Given these physical/chemical properties, it is unlikely that oral exposure from drinking water will be a major pathway of exposure. However, in the absence of a comprehensive set of monitoring data with sufficiently lo w detection limits which could be used to derive exposure values for drinking water, the Agency has incorporated modeled drinking water values into this screening level assessment. E stimated drinking water concentrations (EDWCs) were developed using FIRST , SCI

- GROW and PRZM/EXAMS models. The models, including descriptions

, are available at http://www.epa.gov/oppefed1/models/water/

.

The EDWC screening level assessments modeled the maximum application rate and the minimum interval between applications for each pyrethroid. Both surface water and ground

water EDWCs were developed and are shown in Table 5 .2, however, modeled surface water

EDWCs w ere used as they are significantly higher and provide a conservative estimate for the screening level cumulative assessment. Where a modeled drinking water assessment wouldPyrethroid Cumulative Risk Assessment

Page 41 of 88 predict a value greater than the limit of solubility for a pesticide, the output o f the model will be the chemical’s limit of solubility.

The drinking water component of the screening level pyrethroid CRA is considered to be unrefined and highly conservative , both due to the use of the model and because of the level of refinement used in the modeling scenarios. The assessments are characterized as either Tier 1 or Tier 2, which is an indicator of their level of refinement. For both of these t iers, significa nt refinements are available which are expected to significantly lower the predicted estimated drinking water concentrations. However, these refinements were not conducted as there were
no risks of concern identified based on the unrefined assessments.

Drinking water residues have to be expressed in terms of index chemical equivalents before they can be used in the cumulative risk assessment. Using the individual chemical relative potency factors (RPFs), the EDWCs for each pyrethroid were converted to deltamethrin equivalent exposure values. Since data are not available on the co

- occurrence or relative amounts of individual pyrethroid in a single water sample, the Agency selected the EDWC from the pyrethroid which resulted in the highest residue value expressed as deltamethrin equivalents as surrogate for all drinking water exposure. The highest EDWC in terms of deltamethrin equivalents was derived from the lamda

- cyhalothrin limit of solubility output from the model of 5 pp b . This value is included fo r all water in the assessment as a deltamethrin equivalent concentration of 8.15 pp b

.

In summary, while the physical/chemical characteristics of the pyrethroids suggest that exposure to this class of compound through drinking water is not likely to be a m ajor pathway of exposure; the Agency has incorporated unrefined, modeled estimated drinking water concentrations into this screening level cumulative assessment. Further, the single modeled value which represented the highest deltamethrin equivalent expos ure was used to represent drinking water exposure for all pyrethroids; therefore, the drinking water inputs are considered to be highly conservative. Refinements to the modeled scenarios or availability of acceptable drinking water monitoring data is like ly to significantly reduce the residue values used in a more refined cumulative assessment. The modeled EDWCs, chemical RPFs and corresponding exposures in deltamethrin equivalents are shown in Table 5 .2

.Pyrethroid Cumulative Risk Assessment

Page 42 of 88 Table 5.2. Modeled EDWCs for the Pyrethroids

Chemical Name Ground Water

Acute EDWC (ppb) Surface Water

Acute EDWC (ppb) RPF Surface Water Acute
EDWC in Deltamethrin Equivalents (ppb)
Allethrins Based on the use pattern, residues are not expected in drinking water.
Bifenthrin 0.003 0.014 1 1.01 0.014 Cyfluthrin 0.457 2 1 1.15 4.228 Cyhalothrin 0.00300 5 1 1.63 8.150 2
Cypermethrin 0.0036 3.77 0.19 0.716
Deltamethrin 0.00269 0.2 1 1 0.200
Esfenvalerate 3 0.009 7.54 0.36 2.714 Fenpropathrin 0.00480 10.3 0.5 5.150
Fluvalinate 0.0025 1.31 1.0 1.310
Permethrin 0.012 4.79 0.09 0.431
Prallethrin 0.00104 0.591 0.10 0.059 Pyrethrins 0.003 4.078 0.02 0.082
Resmethrin 0.065 0.20 0.05 0.010

1 The modeled value exceeded the solubility limit; therefore the actual model output is a concentration at the limit of solubility.

2 EDWC used in the pyrethroid cumulative risk assessment.

3 Includes fenvalerate



### 5 .3 Dietary (Food and Water) Assessment

As with previous cumulative risk assessments, the pyrethroid screening level cumulative dietary exposure was e stimated using the Dietary Exposure Evaluation Model

- Food Commodity Index Database (DEEMFCIDTM) software (Exponent, 2007). Estimation of dietary exposure was accomplished by combining distributions of pesticide concentrations on foods
from USDA PDP with di stributions of food consumption from USDA CSFII.

Consistent with OPP dietary exposure assessment guidance, separate assessments were conducted on the various sub

- populations as represented in the CSFII 1994

- 96/1998. This screening level assessment reports on the U.S. general population and the following standard

age groups:

 Infants less than 1 year old  Child ren 1

- 2 years old  Children 3

- 5 years old  Children 6

- 12 years old  Youths 13

- 19 years old  Adults 20

- 49 years old  Adults 50+ years old  Females 13

- 49 years oldPyrethroid Cumulative Risk Assessment

Page 43 of 88 The methodology and tools used for calculating cumulative food residues described in the

revi sed NMC cumulative document are the same methodology and tools used to develop this screening level dietary assessment for the pyrethroids. This includes the generation of tables to hold the data on residue values, processing factors, relative potency fac tors and bridging information (translations between residue data and food forms), along with the use of forms in MS Access to perform the appropriate calculations to express all residues as deltamethrin equivalents and to combine residues on individual sam ples, creating a distribution of residues by commodity. The specific algorithms used to estimate exposure from dietary sources are
detailed in the NMC cumulative document cited above.

The Agency conducted an acute probabilistic dietary risk assessment fo r food residues and food plus water. Cumulative dietary estimated risks for food alone and food plus drinking water, resulting from exposure to pyrethroids, significantly exceed the target MOE of 100 for adults and 300 for children and; therefore, estimat ed risks are not of concern for any population subgroup. The results of the dietary exposure and risk assessment are summarized below for food only (T able 5 .3a ) and food plus water (Table 5 .3b ).

Table 5.3a. Summary of Food Only Dietary Exposure and Es timated Risk for the Pyrethroid C RA

Population Subgroup Acute Dietary

95 th Percentile Acute Dietary

99 th Percentile Acute Dietary

99.9 th Percentile Dietary Exposure (mg/kg/day) MOE Dietary Exposure (mg/kg/day) MOE Dietary Exposure (mg/kg/day) MOE

General U.S. Population 0.000111 99,000 0.000478 23,000 0.001852 5,900

All Infants (< 1 year old) 0.000104 110,000 0.000639 17,000 0.004739 2,300

Children 1

- 2 years old 0.000189 58,000 0.000793 14,000 0.003320 3,300

Children 3

- 5 years old 0.000168 65,000 0.000710 16,000 0.002817 3,900

Children 6

- 12 years old 0.000116 95,000 0.000483 23,000 0.001898 5,800

Youth 13

- 19 years old 0.000073 150,000 0.000361 30,000 0.001530 7,200

Adults 20

- 49 years old 0.000101 110,000 0.000438 25,000 0.001686 6,500

Adults 50+ years old 0.000120 91,000 0.000499 22,000 0.001712 6,400

Females 13

- 49 years old 0.000104 110,000 0.000455 24,000 0.001766 6,200

Most highly exposed subgroup highlighted.Pyrethroid Cumulative Risk Assessment

Page 44 of 88 Table 5.3b. Summary of Food and Water Dietary Exposure and Estimated Risk for the Pyrethroid C RA

Population Subgroup Acute Dietary

95 th Percentile Acute Dietary

99 th Percentile Acute Dietary

99.9 th percentile Dietary Exposure (mg/kg/day) MOE Dietary Exposure (mg/kg/day) MOE Dietary Exposure (mg/kg/day) MOE

General U.S. Population 0.00 0 521 21,000 0.001011 11,000 0.002321 4,700

All Infants (< 1 year old) 0.001722 6,400 0.002563 4,300 0.005544 2,000

Children 1

- 2 years old 0.000819 13,000 0.001434 7,700 0.003646 3,000

Children 3

- 5 years old 0.000731 15,000 0.001212 9,000 0.003157 3,500

Children 6

- 12 years old 0.000512 21,000 0.000864 13,000 0.002124 5,200

Youth 13

- 19 years old 0.000401 27,000 0.000763 14,000 0.002048 5,400

Adults 20

- 49 years old 0.000468 23,000 0.000872 13, 000 0.001980 5,600

Adults 50+ years old 0.000431 26,000 0.000788 14,000 0.001926 5,700

Females 13

- 49 years old 0.000470 23,000 0.000870 13,000 0.002021 5,400

Most highly exposed subgroup highlighted.

For the U.S. population, lettuce , apples, and spinach are the food commodities which contribute the most significantly to dietary exposure from food . For “all infants”, the most highly exposed subgroup, spinach is the commodity which contributes most significantly to the dietary exposure from food

. Based on residues seen in PDP, it appears that residues of permethrin on lettuce and spinach and fenpropathrin on apples are the residues most impacting the dietary exposure from food. However, it should be noted t hat MOEs for all foods
combined are significantly above the target MOEs; t herefore, while these residues are the highest contributors to ex posure, they do not result in an estimated risk of concern.

For the purpose of this screening level assessment, the Agency has included highly conservative modeled drinking water estimates of concentration in this assessment. However, as previously stated given the physical/chemical properties of the pyrethroids, drinking water is not likely to be a major pathway of dietary exposure; therefore actual dietary cumulative estimated risks

are more likely to be closer to those reported for food only.Pyrethroid Cumulative Risk Assessment

Page 45 of 88 

### 6.0 Residential Pyrethroid Cumulative Risk

6.1 Introduction

In the past, the Office of Pesticide Programs (OPP) has employed calendar

- based models to address the temporal aspects of the resident ial use of pesticides when performing a cumulative risk assessment (CRA). Considering the breadth of the pyrethroid residential uses, the use of a
calendar

- based model would involve significant analysis of available exposure and use data.
With this in mind and seeking a less resource and time intensive resolution to the pyrethroid

CRA , OPP performed a health protective, screening

- level assessment to address the cumulative effects and risk of the pyrethroids.

A number of health protective a ssumptions were made in performing this assessment when compared to previous cumulative risk assessments performed by OPP. Further discussion of the implications of these assumptions is provided in Section 7. These assumptions include the following:

1) OPP limited this screening

- level assessment to “users only” (i.e., only users of pyrethroid pesticides were considered in this assessment). Since OPP aggregates both dietary and

non

- dietary exposures from multiple chemicals of the same class, cumulative r isk assessments have typically been based on the entire U.S. population which includes individuals who don’t use pesticides and individuals that use non

- pyrethroid pesticides. 2) OPP assumed no dissipation of chemicals and as such Day 0 (or day of application )
residues were used in all cases. 3) OPP assumed all individuals are exposed (i.e., come in contact with treated surfaces) on the day of application. Typically, cumulative risk assessments have included an activity component that incorporates the potential for “no non

- dietary exposure” days, where a pesticide application occurs but no one is exposed to the treated residues after the application (e.g., no one goes out on a treated lawn after an application). 4) OPP assumed that exposure for each scenario occurre d as a result of use of the pyrethroid with the highest risk estimate registered for that scenario. Typically, cumulative risk assessments have included probabilities of pesticide use within an exposure scenario (i.e., probability of using pesticide A vs. using pesticide B for scenario X). 5) OPP assumed co

- occurrence of certain residential scenarios as worst

- case situations. Typically, cumulative risk assessments have included use data such as the Residential Exposure Joint Venture ( REJV ) survey to identify the likelihood of multiple scenario applications occurring on the same day.

In addition to these assumptions, information regarding residues, exposure, and standard (non

chemical

- specific) exposure factors (such as breathing rates and activity duration) were incorporated in this assessment. In nearly all cases, the residential exposure scenarios in this assessment were developed using the best available residue and exposure data (some of which is proprietary in nature). Exposure factors such as breathin g rates and durations of time spentPyrethroid Cumulative Risk Assessment

Page 46 of 88 performing specific activities were taken from various sources including the U.S. EPA Exposure

Factors Handbook (USEPA, 1997) and the U.S. EPA Child

- Specific Exposure Factors Handbook (USEPA, 2008). Considering the scre ening

- level nature of this assessment, point estimates were used to represent all the exposure inputs. While the dietary and drinking water assessments address only the oral exposure route, the residential assessment considers the dermal and
inhalation ex posure routes, as well as the oral route (i.e., hand

- to

- mouth behavior of young children).



### 6.2 Residential Scenarios and Exposure Routes

There are a variety of pyrethroid pesticides currently registered for residential uses that have been considered as p art of this screening

- level assessment. The residential scenarios addressed in this document represent critical pyrethroid uses that have the potential for significant exposure when considered in a cumulative assessment. For this effort, the Agency focus ed on the four main pyrethroid residential use scenarios

– turf, pets, gardens, and indoors (broadcast, fogger and crack and crevice applications). All other pyrethroid residential uses (e.g., pyrethroid impregnated clothing or personal insect repellent s ystems) are considered minor contributors to the pyrethroid CRA based on amount of use and exposure potential; therefore, those scenarios were not included in this screening

- level assessment. The specific exposure
routes and scenarios assessed in this scr eening level assessment are briefly described below, as well as summarized in Table 6 .2.

Table 6.2. Specific Exposure Routes and Scenarios for the Pyrethroids

Scenario Lifestage Applicator Post

- application
Dermal Inhalation Oral Dermal Inhalation

Lawn/Turf Adult X X X 1 < 2 yr old X X Gardens, Ornamentals, and

Trees Adult X X X 6 < 11 yr old X

Indoors Adult X X X X 1 < 2 yr old X X X

Pets Adult X X X 1 < 2 yr old X X



### 6.2.1 Lawn/Turf Use

Based on an evaluation of risk assessments, reregistration eligibility documents (REDs), use reports, and labels; it was determined that a number of pyrethroids in the CAG currently have products registered for use on turf where residential exposure could occur (e.g., residential
l awns, parks, recreational areas, etc.). These products include, liquid formulations for bifenthrin, cyhalothrin, cyfluthrin, cypermethrin, deltamethrin, permethrin, pyrethrins , and resmethrin; wettable powder formulations for cypermethrin; and granular fo rmulations for cyhalothrin and permethrin.Pyrethroid Cumulative Risk Assessment

Page 47 of 88 Potential d ermal and inhalation exposure was assessed for individuals mixing, loading, and applying pyrethroids to residential lawns. This assessment also considers potential dermal
post

- application exposure for adults and young children (1 <2 year olds) contacting treated lawns. Additionally, oral non

- dietary exposure (hand

- to

- mouth) was considered for young children (1 <2 year olds) potentially transferring treated

- turf residues from their hands to their
mouth s.



### 6 .2.2 Garden, Ornamental, and Tree Use

Based on an evaluation of risk assessments, reregistration eligibility documents (REDs), use reports, and labels; it was determined that a number of pyrethroids in the CAG currently have products registered for us e on residential gardens, ornamentals, and trees. These products include, liquid formulations for bifenthrin, cyhalothrin, cyfluthrin, cypermethrin, deltamethrin, esfenvalerate, fluvalinate, permethrin, pyrethrins , and resmethrin.

Potential d ermal and in halation exposure was assessed for individuals mixing, loading, and applying pyrethroids to gardens, ornamentals, and trees. This assessment also considered potential dermal post

- application exposure for adults and children (6 < 11 years old) contacting treated gardens, ornamentals, and trees.



### 6.2.3 Indoor Use

Based on an evaluation of risk assessments, reregistration eligibility documents (REDs), use reports, and labels; it was determined that a number of pyrethroids in the CAG currently have products registered for use indoors. These products include, liquid formulations for allethrin, bifenthrin, cyhalothrin, cyfluthrin, cypermethrin, deltamethrin, esfenvalerate, permethrin, prallethrin, pyrethrins , and resmethrin; ready

- to

- us e aerosol can formulations for allethrin, cypermethrin, deltamethrin, esfenvalerate, permethrin, phenothrin, pyrethrins

, and

resm ethrin ; and ready

- to

- use fogger formulations for allethrin, cyfluthrin, cypermethrin, esfenvalerate, permethrin, prallethrin, pyrethrins

, and resmethrin.

Potential d ermal and inhalation exposure was assessed for individuals mixing, loading, and applying pyrethroids indoors. This assessment also considers potential dermal post

- application exposure for adults and young children ( 1 <2 year olds) contacting treated indoor surfaces. Additionally, oral non

- dietary exposure (hand

- to

- mouth) was considered for young children (1 <2 year olds) potentially transferring treated

- indoor surface residues from their hands to their
mouths.Pyrethroid Cumulative Risk Assessment

Page 48 of 88 

### 6.2. 4 Pet Use

Based on an evaluation of risk assessments, reregistration eligibility documents (REDs), use reports, and labels; it was determined that a number of pyrethroids in the CAG currently have products registered for use on pets. These products inclu de, ready

- to

- use spot

- on formulations for cyphenothrin and permethrin; ready

- to

- use aerosol can formulations for pyrethrins and prallethrin ; ready

- to

- use shampoo formulations for permethrin; and ready

- to

- use trigger pump spray formulations for allethrin an d resmethrin.

Potential d ermal and inhalation exposure was assessed for individuals mixing, loading, and applying pyrethroids to pets. This assessment also considers potential dermal post

- application exposure for adults and young children (1 < 2 year olds) contacting treated pets. Additionally,
oral non

- dietary exposure (hand

- to

- mouth) was considered for young children (1 <2 year olds) potentially transferring treated

- pet residues from their hands to their mouths.



### 6.3 Residential Handler Exposu re and Risk

Handler exposure refers to an exposure scenario in which an adult individual is exposed during mixing, loading, and applying a pesticide. Residential handler exposure assessments estimate dermal and inhalation exposures for individuals using pesticides in and around their homes. Dermal and inhalation handler exposure may occur from the residential use of pyrethroids. The algorithms used for estimating residential handler exposure and risk were the same for all of
the residential handler sce narios. However, different assumptions and data sources were used depending on the scenario. The algorithms and assumptions are discussed in further detail
below.



### 6.3.1 Handler Algorithms

Handler dermal and/or inhalation exposures are estimated by multi plying the application
method

- specific unit exposure by an estimate of the amount of active ingredient handled in a day, using the following algorithm:

A * AR * UE E **=**

where:

E = exposure (mg/day);

UE = unit exposure (mg/lb ai);

AR = application rate (e.g., lb ai/ft 2 , lb ai/gal); and

A = area treated or amount handled (e.g., ft 2 /day, gal/day).Pyrethroid Cumulative Risk Assessment

Page 49 of 88 Dermal and/or inhalation doses are estimated using the following algorithm:

BW

AF * E D **=**

where:

D = dose rate (mg/kg

- day);

AF = absorption factor (dermal and/or inhalation); and

BW = body weight (kg).

Finally, dermal and/or inhalation margins of exposure are estimated using the following algorithm:

RPF * D POD IC MOE **=**

where:

MOE = margin of exposure;

D = dose rate (mg/kg

- day);

RPF = relative potency factor of any pyrethroid compared to the index chemical, deltamethrin; and

IC POD = point of departure for the index chemical, deltamethrin.



### 6

. 3.2 Handler Data and Assumptions

The following sections describe the data an d assumptions used to estimate dermal and inhalation residential handler risks for pyrethroid use on turf, on gardens, indoors, and on pets.



### 6.3.2.1 Unit Exposure (UE)

Lawn/Turf Use Dermal and inhalation exposure routes were considered in this assessment for all of the turf residential handler scenarios and application equipment. The unit exposures for each piece of application equipment and the studies from which these unit exposures were developed are presented below:

**•** Push

- type spreader (gran ular)

- The recommended dermal and inhalation unit exposures are 0.81 and 0.0026 mg/lb ai, respectively. The dermal unit exposure was developed based on an Outdoor Residential Exposure Task Force (ORETF) study that monitored 30 applications of a granule f ormulation for approximately 20 minutes to approximately 10,000 square feet of turf in North Carolina using a rotary spreader (Klonne, 1999). The inhalation unit exposure was developed based on two separate studies; the same ORETF study used in the dermal unit exposure (Klonne, 1999) and a proprietary studyPyrethroid Cumulative Risk Assessment

Page 50 of 88 (Rosenheck, 1993). The Rosenheck study monitored 15 applications of a granule formulation for approximately 30

- 40 minutes to turf in North Carolina using a push cyclone spreader.

**•** Hose

- end Sprayer (liqu ids)

- The recommended dermal and inhalation unit exposures are 15 and 0.024 mg/lb ai, respectively. Both the dermal and inhalation unit exposures were developed based on an ORETF study that monitored 30 applications of a liquid pesticide formulation for approximately 75 minutes to approximately 5000 ft 2 of residential lawns using a dial

- type hose

- end sprayer (Klonne, 1999).

**•** Hose

- end Sprayer (wettable powders)

- No exposure data are available for this application scenario and, thus, data for applying liqui ds via hose

- end sprayer were used
as a surrogate.

**•** Low

- Pressure Handwand Sprayer (liquids)

- The recommended dermal and inhalation unit exposures are 65 and 0.0054 mg/lb ai, respectively. Both the dermal and inhalation unit exposures were developed based o n two ORETF studies (Merricks, 1997 and Merricks, 1998). The 1997 Merricks study monitored 40 applications of a liquid pesticide formulation for approximately 20 minutes to tomato and cucumber gardens using a low

- pressure handwand. The 1998 Merricks stud y monitored 20 applications of a liquid pesticide formulation for approximately 20 minutes to citrus trees and shrubs using a low

- pressure handwand.

**•** Low

- Pressure Handwand Sprayer (wettable powders)

- The recommended dermal and inhalation unit exposures a re 69 and 1.1 mg/lb ai, respectively. The dermal unit exposure was developed based on two studies (Merricks, 1987 and Dean, 1988). The Merricks study monitored 18 applications of a wettable powder formulation in homes and commercial buildings with two 1

- gallon “B&G stainless steel PCO sprayers”. The Dean study monitored 16 applications of a wettable powder formulation in homes for approximately 1.0

- 2.5 hours using a 1

- gallon hand compression sprayer. The inhalation unit exposure was developed based only on the 1988 Dean study.

**•** Backpack Sprayer (liquids)

- The recommended dermal and inhalation unit exposures are 130 and 0.12 mg/lb ai, respectively. The dermal unit exposure was developed based on three studies (Merricks, 1988; Contardi et. al , 1993; and Beard, 1997). The Merricks study monitored 9 applications of three 2

- gallon liquid pesticide solutions for approximately 47 minutes to poultry litter using a backpack sprayer. The Contardi study monitored 2 applications of a liquid pesticide formulation to greenhouse plants hanging overhead, on the floor, or on benches for approximately 1.5 hours using a backpack sprayer. The Beard study monitored 15 applications of a liquid pesticide formulation to approximately 6000 ft 2 of Christmas tree farms in Michi gan, Pennsylvania, and Connecticut for approximately 4 hours using a backpack sprayer. The inhalation unit exposure was developed based on one study (King and Prince, 1995) that monitored 16 applications of a liquid pesticide formulation for approximately 63

- 94 minutes to greenhouse ornamentals in Florida, Maryland, and California.

**•** Backpack Sprayer (wettable powders)

- No exposure data are available for this application scenario and, thus, data for applying wettable powders via low

- pressure handwand were u sed as a surrogate.Pyrethroid Cumulative Risk Assessment

Page 51 of 88 **•** Sprinkler Can (liquids)

- No exposure data are available for this application scenario and, thus, data for applying liquids via hose

- end sprayer were used as a surrogate.

**•** Sprinkler Can (wettable powders)

- No exposure data are available for this application scenario and, thus, data for applying liquids via hose

- end sprayer were used as a
surrogate.

Garden, Ornamental, and Tree Use Dermal and inhalation exposure routes were considered in this assessment for all the garden, ornamental, an d tree residential handler scenarios and application equipment. The unit exposures for each piece of application equipment and the studies from which these unit exposures were developed are presented below:

**•** Hose

- end Sprayer (liquids)

- The recommended der mal and inhalation unit exposures are 15 and 0.024 mg/lb ai, respectively. Both the dermal and inhalation unit exposures were developed based on an ORETF study that monitored 30 applications of a liquid pesticide formulation for approximately 75 minutes t o approximately 5000 ft 2 of residential lawns using a dial

- type hose

- end sprayer (Klonne, 1999).

**•** Low

- Pressure Handwand Sprayer (liquids)

- The recommended dermal and inhalation unit exposures are 65 and 0.0054 mg/lb ai, respectively. Both the dermal and i nhalation unit exposures were developed based on two ORETF studies (Merricks, 1997 and Merricks, 1998). The 1997 Merricks study monitored 40 applications of a liquid pesticide formulation for approximately 20 minutes to tomato and cucumber gardens using a low

- pressure handwand. The 1998 Merricks study monitored 20 applications of a liquid pesticide formulation for approximately 20 minutes to citrus trees and shrubs using a low

- pressure handwand.

**•** Backpack Sprayer (liquids)

- The recommended dermal and in halation unit exposures are 130 and 0.12 mg/lb ai, respectively. The dermal unit exposure was developed based on three studies (Merricks, 1988; Contardi 1993; and Beard, 1997). The Merricks study monitored 9 applications of three 2

- gallon liquid pestici de solutions for approximately 47 minutes to poultry litter using a backpack sprayer. The Contardi study monitored 2 applications of a liquid pesticide formulation to greenhouse plants hanging overhead, on the floor, or on benches for approximately 1.5 ho urs using a backpack sprayer. The Beard study monitored 15 applications of a liquid pesticide formulation to approximately 6000 ft 2 of Christmas tree farms in Michigan, Pennsylvania, and Connecticut for approximately 4 hours using a backpack sprayer. The inhalation unit exposure was developed based on one study (King and Prince; 1995) that monitored 16 applications of a liquid pesticide formulation for approximately 63

- 94 minutes to greenhouse ornamentals in Florida, Maryland, and California.

**•** Sprinkler Ca n (liquids)

- No exposure data are available for this application scenario and thus data for applying liquids via hose

- end sprayer were used as a surrogate.

Indoor Use Dermal and inhalation exposure routes were considered in this assessment for all of the indoor residential handler scenarios and application equipment. The unit exposures for each piece ofPyrethroid Cumulative Risk Assessment

Page 52 of 88 application equipment and the studies from which these unit exposures were developed are presented below:

**•** Low

- Pressure Handwand Sprayer (liquids)

- No ex posure data are available for this application scenario and thus data for applying wettable powders via low

- pressure handwand sprayer were used as a surrogate.

**•** Low

- Pressure Handwand Sprayer (wettable powders)

- The recommended dermal and
inhalation unit e xposures are 69 and 1.1 mg/lb ai, respectively. The dermal unit exposure was developed based on two studies (Merricks, 1987 and Dean, 1988). The Merricks study monitored 18 applications of a wettable powder formulation in homes and commercial buildings w ith two 1

- gallon “B&G stainless steel PCO sprayers”. The Dean study monitored 16 applications of a wettable powder formulation in homes for approximately 1.0

- 2.5 hours using a 1

- gallon hand compression sprayer. The inhalation unit exposure was developed based only on the 1988 Dean study.

**•** RTU Aerosol can

– The recommended dermal and inhalation unit exposures are 370 and 3 mg/lb ai, respectively. The dermal and inhalation unit exposures were based on a study from Knarr (1991). The Knarr study monitored 15 applications to cracks, crevices, baseboards, under sinks, and behind appliances in 15 separate houses using an entire 16
oz. aerosol can.

**•** R eady

- to

- Use (R TU ) Total Release Fogger

- Total release foggers are assumed to provide negligible exposure to the ap plicator since the label typically requires applicators to exit the treatment area immediately.

Pet Use Dermal and inhalation exposure routes were considered in this assessment for all of the pet residential handler scenarios and application equipment. The unit exposures for each piece of application equipment and the studies from which these unit exposures were developed are presented below:

**•** RTU Spot

- on

- The recommended dermal unit exposure is 220 mg/lb ai. Inhalation exposure data during application of sp ot

- on treatments is unavailable; however

, exposure through this route is considered negligible. The dermal unit exposure was based on a study from Meo (1997). The Meo study monitored 16 applications by commercial pet groomers to 8 dogs for approximately 14

- 32 minutes using a read

- to

use (RTU), disposable, snap

- top, plastic

- backed pipette.

**•** RTU Shampoo

- The recommended dermal and inhalation unit exposures are 2100 and 0.28 mg/lb ai, respectively. The dermal unit exposure for shampoo applicat ions of liquid pesticide formulations to pets, animals, or children is based on two studies (Mester, 1998 and Selim, 2005). The Mester study monitored 16 applications by commercial pet groomers of shampoo to 8 dogs for approximately 149

- 295 minutes. The Selim study monitored 16 shampoo applications to one dog each for approximately 30 minutes. The inhalation unit exposure is based only on the Mester study.

**•** RTU Trigger

- pump Sprayer

- The recommended dermal and inhalation unit exposures are 820 and 3.3 mg/ lb ai, respectively. The dermal and inhalation unit exposures for applications of liquid pesticide formulations using a trigger

- pump sprayer to pets orPyrethroid Cumulative Risk Assessment

Page 53 of 88 animals are based on a study from Meo (1997). This study monitored 16 applications by commercial pet g roomers treating 8 dogs for approximately 38

- 72 minutes using a read

to

- use (RTU) trigger

- spray bottle.

**•** RTU Aerosol Can

- No exposure data are available for this application scenario and, thus, data for using a RTU Trigger

- pump sprayer were used as a surro gate.



### 6.3.2.2 Application Rate (AR)

In all cases, OPP used the maximum labeled application rate to assess dermal and inhalation
handler risk estimates for all of the residential pyrethroid uses.



### 6.3.2.3 Area Treated/Amount Handled (A)

Lawn/Turf Use

OPP assumed two types of treatments could be performed by individuals treating turf: broadcast and spot treatments. For broadcast turf treatments using hose

- end sprayers (liquids) and push

- type spreaders (granular), OPP assumed 1⁄2 acre would be treated by a ho me

- owner. For spot turf treatments using low

- pressure handwand sprayers (liquids and wettable powders), backpack sprayers (liquids and wettable powders), and sprinkler cans (liquids and wettable powders), OPP assumed 1,000 ft 2 would be treated by a home

- o wner. Determination of these values was based mainly on the Outdoor Residential Pesticide Use and Usage Survey and National Gardening Association Survey (Johnson, 1999), which showed that 73% of the people surveyed had lawns smaller than 1⁄2 acre.

Garden, Ornamental, and Tree Use OPP assumed 1,200 ft 2 would be treated by an individual when treating gardens, ornamentals, and trees. Determination of these values was based mainly on the Outdoor Residential Pesticide Use and Usage Survey and National Gardening Association Survey (Johnson, 1999), which showed that the average garden size was 1,200 ft 2

.

Indoor Use OPP assumed broadcast and crack and crevice treatments could be performed by individuals treating indoor surfaces. Both of these types of treatments are surface

- directed and could be applied with a low

- pressure handwand or an aerosol can. The low

- pressur e handwand was
assumed to be used for both broadcast and crack and crevice treatments. OPP assumed 0.5 gallons would be used by a homeowner for both types of treatments. These values are supported by data from the Pesticide Handler Exposure Database (PHE D), which indicate about 0.5 gallons for a commercial applicator crack/crevice and limited surface treatment in residences. Based on the use pattern for the pyrethroids, aerosol cans are only registered for
crack and crevice treatments. OPP assumed 1⁄2 of a 16

- oz can would be used. This value is supported by data from the Pesticide Handler Exposure Database (PHED), in which studies were
conducted with commercial applicators applying one 15

- oz aerosol can to areas of residential homes, including crack s , cre vices, baseboards, under sinks, behind appliances, etc.Pyrethroid Cumulative Risk Assessment

Page 54 of 88 Pet Use OPP assumed that residential handlers of pet treatment products will treat 2 animals per application. This estimate is based upon data from the American Pet Products Manufacturers

Associatio n (APPMA) 2007

- 2008 National Pet Owners Survey, which reports that pet owners have an average of 1.7 dogs and 2.3 cats.



### 6.3.3 Handler Risk Summary

For all scenarios, there are no residential handler risk estimate s of concern associated with the registered uses of pyrethroids. All MOEs are greater than the target MOE of 1 00 for adult
handlers (see Appendix 7 an d Table 6 .4.7a ).



### 6 .4 Post

- application Exposure and Risk

Post

- application exposure refers to an exposure scenario in which an individual is exposed through dermal, inhalation, and/or incidental oral (non

- dietary ingestion) pathways as a result of being in an environment that has been previously treated with a pesticide. Post

- application
dermal exposure is dependent on surface residues after treatment and surface

- to

- skin transfer.

Post

- application inhalation exposure depends on concentrations in the air after treatment and
inhalation rates. Post

- application non

- dietary oral exposures are based on the ingestion of
residues that can result from transfer of residues from hand

- to

- mouth. Dermal, inhalation, and

non

- dietary oral (hand

- to

- mouth) post

- application exposure may occur following the residential use of pyrethroids depending on the use site . The algorithms and assumptions used for estimating residential post

- application dermal, inhalation, and non

- dietary oral are discussed in
further detail below.



### 6.4.1 Post

- application Dermal Exposure

Post

- application dermal exposure may occur following the residential uses of pyrethroids.



### 6.4.1.1 Dermal Post

- application Algorithm

The following general equation is used to calculate dermal exposures resulting from contact
with treated residential surfaces.Pyrethroid Cumulative Risk Assessment

Page 55 of 88 E = TR * TC * ET

where : E = exposure (mg/day);

TR = transferable residue (mg/cm 2 );

TC = transfer coefficient (cm 2 /hr);

ET = exposure time (hr/day).

Dermal doses are estimated using the following algorithm:

BW

AF * E D **=**

where:

D = dose rate (mg/kg

- day);

AF = absorption factor (dermal); and

BW = body weight (kg).

Finally, dermal margins of exposure are estimated using the following algorithm:

RPF * D POD IC MOE **=**

where:

MOE = margin of exposure;

D = dose rate (mg/kg

- day);

RPF = relative potency factor of any pyrethroid comp ared to the index chemical, deltamethrin; and

IC POD = point of departure for the index chemical, deltamethrin.



### 6.4.1.2 Dermal Post

- application Data and Assumptions

6.4.1.2.1 Transferable Residue (TR)

Following an application, pesticide residues, which a re deposited and remain on surfaces, could be contacted and removed by an individual. The pesticide residue is then available for absorption through the skin or potential ingest ion . The residue available for transfer is referred
to as transferable residu e (TR). If pyrethroid

- specific transferable residue data were available for a specific chemical, they were used in the cumulative screen. If pyrethroid

- specific data were not available, the TR was calculated based on a fraction of the pesticide applied.Pyrethroid Cumulative Risk Assessment

Page 56 of 88 Lawn/Turf Use For the lawn/turf use scenario, chemical

- specific turf transferable residue (TTR) data collected with the Modified California Roller Method are available, and directly used, for four pyrethroids: cyfluthrin (liquid formulations)

, cypermethrin (liquid and wettable powder formulations) , deltamethrin (liquid formulations) , and permethrin (liquid formulations)

. Cyfluthrin resulted in the highest normalized turf transferable residues out of the available liquid formulation TTR data. F or the liquid formulation pyrethroids that did not have TTR data available, cyfluthrin TTR data were used as a surrogate. In all cases, the cyfluthrin TTR data were adjusted to reflect the maximum individual pyreth roid application rates. Table 6 .4.1.2.1a summarizes the available pyrethroid TTR data.

Table 6.4.1.2.1a. Pyrethroid TTR Summary

Chemical Study Sites Day 0

TTR (ug/cm 2 ) Average Day 0 TTR (ug/cm 2 ) Average Day 0
TTR Normalized

to 0.1 lb ai/A

(ug/cm 2 )

Cyfluthrin Determination of Transferable Turf Residues on Turf Treated With Cyfluthri n (MRID 45149001) GA (L) 0.023

0.021 0.011 MS (L) 0.032 NY (L) 0.007

Cypermethrin Demon WP and Demon TC Transferable Turf Residue Study (MRID 45111501) CA (WP) 0.081

0.071 0.012 MO (WP) 0.041 PA (WP) 0.090

CA (L) 0.035

0.023 0.0052 MO (L) 0.009 PA (L) 0.026

Deltamethrin Determination of Transferable Turf
Residues on Turf Treated with Deltamethrin (Deltagard GC or T&O) (MRID 45251201) NY (L) 0.008

0.014 0.010 CA (L) 0.020

GA (L) 0.013

Permethrin Transferable Turf Residue Study: Permethrin Residues in Turf Following Application of Dragnet® SFR Insecticide/Miticide (MRID 44955501) PA (L) 0.051

0.061 0.0070 CA (L) 0.073

GA (L) 0.058

Garden, Ornamental, and Tree Use For the garden, ornamental, and tree use scenario, chemical

- specific dislodgeable foliar residue (DFR) data are available for four pyrethroids: cyfluthrin, fluvalinate, esfenvalerate, and permethrin. Most of these DFR data were collected on orchard c rops (i.e., stone fruits, apples, oranges) or in greenhouses. The esfenvalerate DFR data included analysis of foliar residues on corn and broccoli and are considered most representative of potential crops that could be found in a home garden. These data were combined and used as a surrogate for all of the pyrethroids. In all cases, the esfenvalerate DFR data were adjusted to reflect the maximum individual pyreth roid application rates. Table 6 .4.1.2.1b summarizes the available pyrethroid
DFR data.Pyrethroid Cumulative Risk Assessment

Page 57 of 88 Tab le 6.4.1.2.1b. Pyrethroid DFR Summary

Chemical Study Sites Day 0 DFR (ug/cm 2 ) Average Day 0 DFR (ug/cm 2 )

Esfenvalerate Dissipation of Dislodgeable Foliar
Residues of Esfenvalerate from Broccoli

Following Application of Asana® XL
Insecticide in the USA

- Season 1997 ( MRID 44852402) CA1 (L) 0.157

0.132 CA2 (L) 0.122

Dissipation of Dislodgeable Foliar
Residues of Esfenvalerate from Sweet Corn Following Application of Asana® XL

Insecticide in the USA

- Season 1998 ( MRID 44852403) FL (L) 0.072

PA (L) 0.177

Indoor Use For the indoor uses scenarios, no chemical

- specific transferable residue (TR) data are available for the pyrethroids; therefore, the TR was calculated using the following formula:

TR = DepR * F ai

where : TR = indoor surface transferable residue (μg/cm 2 ); DepR = deposited residue (ug/cm 2 ), and

F ai = fraction of ai available for transfer from carpet or hard surface (unitless).

Deposited Residue (DepR) Broadcast applications: For broadcast applications, the deposited residue w as assumed to be equivalent to the application rate (a unit conversion was performed to achieve residue values in units of ug/cm 2 ). A formal evaluation was conducted for each pyrethroid with registered indoor broadcast uses to determine the maximum applic ation rate currently registered. Th ese rate s

w ere used in the screening

- level cumulative assessment.

Fogger applications: For fogger applications, data from the Non

- Dietary Exposure Task Force (NDETF) w ere used to estimate deposited residue for the pyr ethroids with registered indoor fogger uses (Rogers, 2000; Selim, 2002a; Selim, 2003a). The NDETF conducted three studies measuring the deposited residue following application of a 0.2% deltamethrin fogger, a 0.5% permethrin fogger, and a 0.5% pyrethrins fogger. In each study, the fogger was discharged in an experimental room and the resulting deposited residues were measured using deposition coupons. The average residue value (adjusted to 0.5% active ingredient, if necessary) from each study was 5.6 ug/ cm 2 for deltamethrin, 4.8 ug/cm 2 for permethrin, and 5.8 ug/cm 2 for pyrethrins . The average residue value across the three studies was 5.4 ug/cm 2 for a 0.5% fogger.

A formal evaluation of all the registered uses was conducted for each pyrethroid with registered indoor fogger uses to determine the maximum percent active ingredient in registered products. In the cumulative screen, the chemical

- specific residue for deltamethrin,Pyrethroid Cumulative Risk Assessment

Page 58 of 88 permethrin, and pyrethrins was used, making an adj ustment for the maximum percent active ingredient registered. For the pyrethroids without chemical

- specific residue data, the average residue value from the three studies was used, making the same adjustment for maximum percent active ingredient registere d.

Crack and crevice applications: For crack and crevice applications, the Agency used a registrant

submitted study (Selim, 2008) that provided an estimate of deposited residue from a crack and crevice application for esfenvalerate. In this study, a 0 .1% esfenvalerate formulation was applied using an aerosol can with an injection tube. The test container was held 12 to 18 inches above the baseboard to achieve an approximate one inch spray band at the floor/wall interface.
Residues were collected 30 m inutes after application using deposition coupons. The residue value for the entire room was calculated as a weighted average of the “treated area” and the “untreated area” (10% of residue in treated area plus 90% of residue in untreated area). This

resu lted in a weighted residue value of 0.2 ug/cm 2 . This value was used for all of the pyrethroids with registered crack and crevice uses. It was not adjusted for percent active ingredient because data available to the Agency do not seem to indicate a trend with respect to deposited residues and percent active ingredient (i.e., a higher percent active ingredient does not necessarily result in a higher deposited residue value for a room).

Fraction of Residue Available For Transfer (F ai

)
Chemical

- specific d ata provided by the Non

- Dietary Exposure Task Force (NDETF) were used for the fraction of residue available for transfer (Selim, 2004a; Selim, 2003b; Selim, 2003c; Selim, 2000; Selim, 2002b; Selim, 2002c). The NDETF studies examined the transferability of residues
from bare hand

- presses on carpets and hard surfaces for deltamethrin, permethrin, and pyrethrins . For carpets, the fraction transferred was 0.03, 0.02 and 0.01 for pyrethrins

, permethrin and deltamethrin, respectively. For hard surfaces, the fr action transferred was 0.04, 0.03, and 0.05 for pyrethrins , permethrin, and deltamethrin, respectively. Since the values were so similar across the three chemicals, the average fraction transferred was used for all the pyrethroids in the cumulative assess ment: 0.02 for carpets and 0.04 for hard surfaces.

Pet Use For the pet uses scenarios, no chemical

- specific TR data are available; therefore, the TR was calculated using the following formula:

TR = (AR * F AR ) / SA

where:

TR = transferable residue (mg/cm 2 );

AR = application rate or amount applied to animal (mg);

F AR = fraction of the application rate available as transferable residue; and

SA = surface area of the pet (cm 2 ).Pyrethroid Cumulative Risk Assessment

Page 59 of 88 Application Rate (AR)
A formal evaluation was conducted for e ach pyrethroid with registered pet uses to determine the maximum application rate currently registered. Th ese rate s w ere used in the screening

level cumulative assessment.

Fraction Application Rate (F AR

)
A default F AR was selected based on the review of 8 “ petting” studies submitted to the Agency. Measurements of residue availability were derived by taking the ratio of the amount of active ingredient on a bare or gloved hand (on the day of highest observed transfer) to the amount of active ingredient applie d. Studies were performed by means of volunteers “petting” or “stroking” animals treated with a known amount of active ingredient and determining the
amount of residue transferred to the hands. F AR studies varied in the number, location and intensity of petting and stroking actions. Based on the available studies, the mean F AR is
estimated to be 0.0096 (Hughes, 1997; Hughes, 1997b; McKeown, 2001; Brickel, et. al, 1997; Bach, 2002; Wrzesinski, 2009; Wrzesinski, 2010a; Wrzesinski, 2010b). Table 6 .4.1.2.1c
summarizes the available F AR data.

Table 6.4.1.2.1c. Fraction Application Rate (F AR ) Transferred

Study MRID N Average
Fraction of Application Rate
Transferred Dislodgeable Residues of Fipronil Following Application of Frontline® Spray Treatment to Dogs 44433306 30 0.0069

Dislodgeable Residues of Fipronil Following Application of
Frontline® S pray Treatment to Cats 44433307 15 0.0039

Determination of the Dislodgeability of Tetrachlorvinphos (TCVP) from the Fur of Dogs Following the Application of an Insecticide Powder, Pump Spray or Aerosol 45485501 10 0.0030

Dislodgeable Residues of Fipronil Following Topical Application of Frontline® Spot

- on Treatment to Dogs 44531203 18 0.0076

Stroking Test in Dogs After Topical Application of I midacloprid 10% (w/v) + Permethrin 50% (w/v) Spot

- On 46594103 18 0.0027

Dislodgeable Residue Study of SCH 783460 (Indoxacarb) from Spot

On Treated Beagle Dogs 47834502 20 0.0208

One

- Month Dislodgeable Residue Study of SCH 783460 (Indoxacarb) from Spot

- On Treated Cats 48010801 20 0.0100

One

- Month Dislodgeable Residue Study of Indoxacarb from Spot

- On Treated Beagle Dogs 48135326 20 0.0094

One

- Month Dislodgeable Residue Study of Permethrin from Spot

On Treated Beagle Dogs 48135326 20 0.0176

Surface Area (SA) Animal surface area (SA) is determined by inputting animal weight (lbs) into an algorithm (12.3*((animal body weight (lbs)*454)^0.65)) as referenced from U.S. EPA (1993) Wildlife Exposure Factors Handbook. For the purposes of the pyrethroid screen, t he surface area of a medium dog was used in the calculations of exposure (7000 cm 2 ).Pyrethroid Cumulative Risk Assessment

Page 60 of 88 

### 6 .4.1.2.2 Transfer Coefficient (TC)

The transfer coefficient (TC) provides a measure of surface

- to

- skin residue transfer and is
derived from concurrent measurements of exposure and surface residue. Specifically, the TC is the ratio of exposure rate, measured in mass of chemical per time (i.e., ug/hr), to residue, measured in mass of chemical per surface area (i.e., ug/cm 2 ). Table 6 .4.1.2.2 summarizes the
transfer coefficients for the different residential scenarios.

Lawn/Turf Use The transfer coefficients used for assessing the lawn/turf dermal scenarios were derived from data gathered while adult human volunteers performed an approximate 2

- hour composite

routine consisting of 12 sequential activities which children and adults routinely engage on residential turf (Klonne and Johnson, MRID 47292001). These activities represent behaviors that are reported in the National Human Activity Pattern Survey (NHAPS) for chi ldren aged 1 to 12 years ( Klepeis, et. al., 2001 ). The two hour duration of the routine was chosen because NHAPS indicated that the upper

- bound estimate of time children spend playing on turf is two hours per day. The potential dermal exposure to each st udy participant was measured by using
whole

- body dosimetry (inner and outer dosimeters), foot washes, hand washes, and face/neck wipes.

Garden, Ornamental, and Tree Use The transfer coefficients used for assessing the garden, ornamental, and tree dermal s cenarios were derived from data gathered while adult human volunteers performed various tasks such as weeding and picking flowers and vegetables. The data used to derive the transfer coefficients are from occupational reentry exposure studies conducted by the Agricultural Reentry Task Force (ARTF) because data to adequately characterize exposure for individuals who contact previously treated residential gardens, ornamentals, and trees are unavailable. Four separate exposure studies were used to develop th e transfer coefficient: a study each for cabbage weeding (Klonne, 2000; MRID 45191701), tomato tying (Klonne, 2001; MRID 45530103), squash harvesting (Klonne, 2001; MRID 45491902), and chrysanthemum pinching (Klonne, 2000; MRID 45344501). Therefore, tran sfer coefficients from occupational reentry exposure studies conducted by the Agricultural Reentry Task Force (ARTF), were used to establish composite transfer coefficients representing activities likely to occur in residential settings.

Indoor Use
The tr ansfer coefficients used for indoor scenarios are derived from information provided in three different studies: (1) two studies which measured exposure and surface residues while subjects performed a JazzerciseTM routine (Krieger, 2000 and Selim, 2004) and (2) a study which measured biomonitoring doses while adults performed scripted activities for 4 hours on carpet (Vaccaro, 1991). In the Krieger and Selim studies, a JazzerciseTM routine was performed to achieve maximum contact of the entire body with a sur face using low impact aerobic movements. The potential dermal exposure was measured by using whole

- body dosimetry. The assumption is that the dosimeter represents the skin and that the dose retained by thePyrethroid Cumulative Risk Assessment

Page 61 of 88 dosimeter is equivalent to dermal exposure. In the Vaccaro study, adult males, dressed in bathing suits only, performed different activities over a 4

- hour activity period. These activities included: sitting

- playing with blocks, on hands and knees crawling, walking on carpet, laying on back, and layin g on abdomen. Using information from these studies on residue transfer, exposure and dose provides an estimated transfer coefficient for indoor activities. It is assumed that the shorter duration of high contact activity (i.e., JazzerciseTM) can be used t o estimate exposure during longer durations of low contact activity.

Pet Use The transfer coefficients used for pet exposure were derived from a study representing application and grooming activities with dogs using a carbaryl shampoo product (Mester, 199 8). Data were gathered while human volunteers applied pet pesticide products to various dogs of differing sizes and fur lengths.

Table 6.4.1.2.2. Transfer Coefficient Summary

Scenario Adults (cm 2 /hr) 6

- 11 year olds (cm 2 /hr) 1

- 2 year olds (cm 2 /hr) Turf/Lawn Use 130,000 NA 37,000 Garden/Ornamental/Tree Use 8,400 5,000 NA
Indoor Use 6,800 NA 2,000

Pet Use 5,200 NA 1,500



### 6.4.1.2.3 Exposure Time (ET)

Table 5.4.1.2.3 summarizes the selected exposure times for the different residential scenarios.

Lawn/Turf Use The exposure times used for assessing the lawn/turf dermal scenarios were selected from data presented in the Agency’s Exposure Factors Handbook Table 15

- 80 (USEPA, 1997). Th e s e data represent the amount of time spent outdoors rather than ju st on lawns. This adjustment allows for additional time that children may spend outdoors (such as parks and schools) where there is potential for additional contact with treated turf.

Garden, Ornamental, and Tree Use The exposure times used for assessing the garden, ornamental, and tree dermal scenarios were derived using a residential survey (Johnson, 1999) and information from the U.S. EPA Exposure Factors Handbook (USEPA, 1997). The exposure time for gardening represents vegetable gardening and flower gardening in equal proportion (i.e., 50% each).

Indoor Use A study which provides information specific to time spent on different types of surfaces indoors is not available. The Exposure Factors Handbook (U.S. EPA, 1997) and the Child Specific Exposure Factors Handbook (U.S. EPA, 2008) provide information on total time spent in a residence and time spent in various rooms within a residence. In order to develop inputs for exposure time on carpets and hard surfaces, two assumptions were made: (1) kitchens andPyrethroid Cumulative Risk Assessment

Page 62 of 88 bathrooms would represent time spent on hard surfaces and (2) time spent in a residence, less time spent sleeping and napping, would represent time spent on carpets.

Pet Use The exposure time for adults and children were derived from the US EPA’s N ational Center for Environmental Assessment (NCEA) Exposure Factors Handbook (USEPA, 1997). The
recommended data are included in Table 15

- 77, Statistics for 24

- Hour Cumulative Number of Minutes Spent in Animal Care . Animal care is defined by NCEA as “car e of household pets including activities with pets, playing with the dog, walking the dog and caring for pets of relatives, and friends.” The data identified the time spent with an animal while performing
household activities as recorded in 24 hour diarie s by study volunteers. While the activities defined do not necessarily represent the time volunteers were actively engaged in constant contact with the animal, as is implicit in the post

- application dermal and incidental oral algorithms, they were used to derive the best data source available.

Table 6.4.1.2.3. Exposure Time Summary

Scenario Adults (hrs) 6

- 11 year olds (hrs) 1

- 2 year olds (hrs) Turf/Lawn Use 1.1 NA 1 0.9 Garden/Ornamental/Tree Use 1.4 0.7 NA 2

Indoor Use Carpets 8 NA 1 5
Hard Surfaces 2 NA 1 1

Pet Use 0.77 NA 1 0.99

NA 1

- not assessed because 1

- 2 yr olds are expected to be protective for 6

- 11 yr olds

NA 2

- not assessed because 1

- 2 yr olds are not expected to be performing gardening activities



### 6.4.2 Post

- application Dermal Risk Summary

For all scenarios, there are no residential post

- application dermal risk estimate s of concern associated with the registered uses of pyrethroids. All MOEs were greater than the Agency’s target MOE of 300 for children and 100 for adults (see Appe ndix 7 and Table 6 .4.7a).



### 6.4.3 Post

- application Inhalation Exposure

For turf and gardens, p ost

- application inhalation exposure is generally not assessed. The combination of the generally low vapor pressure for pyrethroids and the substantial dilution of airborne concentrations outdoors is likely to result in minimal inhalation exposure

.

For pet uses, post

- application inhalation exposure is generally not assessed. The combination of the generally low vapor pressure for pyr ethroids and t he small amounts of pesticide applied to pets is likely to result in minimal inhalation exposure.

For indoor uses, post

- application inhalation exposure is dependent on the type of application
made:Pyrethroid Cumulative Risk Assessment

Page 63 of 88 Fogger applications: Post

- application inhalation exposure due to the use of indoor foggers is expected to be negligible since most fogger product labels typically state a period of no

- entry following application (usually up to 4 hours), as well as a ventilation period before occupants

can return.

Crack and crevice applications: For crack and crevice applications, there is the potential for
post

- application inhalation exposure to pesticide vapors emitting from the treated surfaces following application. For pyrethroids, t his exposure is not expected to be significant primarily because of their low vapor pressure . HED has recently received an Office of Research and Development (ORD) exposure study that was performed in the U.S. EPA’s IAQ Research House. This study is curr ently unpublished but HED has reviewed the data (Smith, D390098, 2011). This study simulated crack and crevice applications of four pesticides; two emulsifiable concentrates products applied via a handheld sprayer (permethrin and cypermethrin), one

aeroso l can product (propoxur), and one gel bait product (fipronil). Permethrin and cypermethrin air concentrations were not found in any measurable quantities in any room in the research house. Although this study provides data for only two pyrethroids, the N on

dietary Exposure Task Force (NDETF) has performed an analysis of all the pyrethroid exposure data that they produced ( Osimitz and Holden, 2005; MRID 46493701 ). This analysis shows the exposure data for one pyrethroid can generally be used to represent the entire chemical class. Based on this NDETF analysis, the air concentration data from the ORD study can be considered representative of all pyrethroids. Given the negligible air concentration values that were reported from the ORD study, HED does not have concerns for post

- application inhalation exposure from pyrethroid crack and crevice applications.

Broadcast applications: Similar to crack and crevice applications, there is the potential for post

- application exposure to pesticide vapors emitting f rom treated indoor surfaces following indoor broadcast applications. For pyrethroids, this exposure is not expected to be significant primarily because of their low

vapor pressure . Pyrethroid

- specific air monitoring data following a broadcast application are not available; therefore, the approach discussed below was used to estimate potential post

application exposure for the pyrethroids with broadcast uses (allethrin, esfenvalerate, permethrin, pyrethrins , and tetramethrin).



### 6.4.3.1 Post

- application In halation Algorithms

Post

- application inhalation exposure for adults/children resulting from surface

- directed spray applications made indoors can be estimated using the following algorithm:Pyrethroid Cumulative Risk Assessment

Page 64 of 88 

# ( **) (**  **) **  ** **  ** **  ** **  ** **  ** **  ** **  ****

**− −** 

**− =**  **− −** 



### k

ACH e k e ACH

V ACH M IR E ET ACH ET k

room label * * 

### * * 1 *

* *

Where : E = exposure (mg/day);

IR = inhalation rate (m 3 /hr);

M label = mass of active ingredient applied, determined from product label (mg);

V room = volume of room (m 3 );

ACH = air exchanges per hour ( hour - 1 );
k = first order decay rate; and

ET = exposure time (hr). Once the post

- application inhalation exposure is calculated, the inhalation dose normalized to body weight is calculated as:

BW

AF E D *

**=**

where : D = dose (mg/kg

- day);

E = exposure (mg/day);

AF = absorption factor (inhalation); and

BW = body weight (kg).

Finally, inhalation margins of exposure are estimated using the following algorithm:

RPF * D POD IC MOE **=**

where:

MOE = margin of exposure;

D = dose rate (mg/kg

- day);

RPF = relative potency factor of any pyrethroid compared to the index chemical, deltamethrin; and

IC POD = point of departure for the index chemical, deltamethrin.



### 6.4.3.2 Post

- application Inhalation Data and Assumptions

6.4.3.2.1 Inhalation Rate (IR)

For in door post

- application exposure, it is recommended that the inhalation rate for sedentary and passive activities be used in the exposure calculation. The values used in this assessment

are 0.32 m 3 /hr for adults and 0.28 m 3 /hr for 1 to <2 year olds (U.S. EP A, 2009).Pyrethroid Cumulative Risk Assessment

Page 65 of 88 

### 6.4.3.2.2 Mass of active ingredient applied (M label 

### )

The mass of active ingredient applied was calculated based on maximum application rates determined by a formal evaluation of all the registered pyrethroid indoor uses . The application

rates were in units of lb ai/square feet and it was assumed for broadcast applications that the product was sprayed over an area of 144 square feet (12 ft by 12 ft room).



### 6.4.3.2.3 Air Changes per Hour (ACH)

Air changes per hour is the rate that air within an indoor environment is replaced by outdoor air. The value used in this assessment is 0.18 ACH, which represents the 10th percentile of the estimated national distribution for residential air exchange rates and is a conservative estimation of air exchange in residential settings (U.S. EPA, 1997).



### 6 .4.3.2.4 Volume of a Room (V
room 

### )

The volume of a room is based on typical dimensions of residential rooms from Exposure Factors Handbook (U.S. EPA, 1997). For a 12 foot by 12 foot room, with an 8 foot high ceiling, the typical volume is 33 m 3

.



### 6 .4.3.2.5 First Order Decay Rate (k)

The decay rate, k, defines the change in the emission rate from the treated surface. As proposed by Evans (1994), the decay rate constant is based on the 90% drying time. The 90% drying time, in turn, is calculated based on the evaporation time and volatility of the chemical using equations from Chinn (1981).



### 6 .4.3.2.6 Exposure Time (ET)

For vapor emissions from surface

- directed sprays, it is assumed that the vapors can continue to emit over time; therefore, exposure time is related to time spent in a residence. The value used in this assessment is 16 hours for both adults and 1 to <2 year olds (U.S. EPA, 1997 and U.S. EPA, 2008 ).



### 6 .4.4 Post

- application Inhalation Risk Summary

For all scenarios, there are no residential post

- application inhalation risk estimate s of concern associated with the registered uses of pyrethroids. All MOEs were greater than the Agency’s target MOE o f 300 for children and 100 for adults (see Appendix 7 and Table 6 .4.7a)

.Pyrethroid Cumulative Risk Assessment

Page 66 of 88 

### 6 .4.5 Post

- application Incidental Oral Exposure and Risk

Post

- application incidental oral exposure may occur following the lawn/turf, indoor, and pet uses of pyrethroids. For gardens, p ost

- application incidental oral exposure is not assessed as younger children are not expected to spend extended periods of time in contact with gardens, ornamentals, and trees.



### 6.4.5.1 Pos t

- application Incidental Oral Algorithm

Post

- application incidental oral exposure for children resulting can be estimated using the following algorithm:

E = [HR * (F M * SA H ) * (ET * N_Replen) * (1

- (1

- SE ) (Freq_Replen/N

- Replen) )]

Where:

E = exposure (mg/day);

HR = hand residue loading (mg/cm 2 );

F M = fraction hand surface area mouthed / event (fraction/event);

ET = exposure time (hr/day);

SA H = surface area of one hand (cm 2 ); N_Replen = number of replenishment intervals per hour (intervals/hour);

SE H = saliva extraction factor ( i.e. , mouthing removal efficiency); and Freq_Replen = number of hand

- to

- mouth contacts events per hour (events/hour).

Hand residues are estimated using the following algorithm.

HR = (Fai hands * DE) / (SA H * 2)

Where : HR = hand residue loading (mg/cm 2 );

Fai hands = fraction ai on hands compared to total surface residue from dermal exposure study (unitless);

DE = dermal exposure (mg); and

SA H = typical surface area of one hand (cm 2 ).

Non

- dietary incidental oral doses ar e estimated using the following algorithm:

BW

E D **=**

where:

D = dose rate (mg/kg

- day); and

BW = body weight (kg).Pyrethroid Cumulative Risk Assessment

Page 67 of 88 Finally, non

- dietary incidental oral margins of exposure are estimated using the following algorithm:

RPF * D POD IC MOE **=**

where:

MOE = margin of exposure;

D = dose rate (mg/kg

- day);

RPF = relative potency factor of any pyrethroid compared to the index chemical, deltamethrin; and

IC POD = point of departure for the index chemical, deltamethrin.



### 6.4.5.2 Post

- application In cidental Oral Data and Assumptions

6.4.5.2.1 Hand Residue (HR)

The available residue on hands for non

- dietary ingestion is linked to dermal exposure and is calculated as a fraction of the dermal exposure. The fraction of active ingredient available on

t he hands was based on data from the dermal transfer coefficient studies for turf, indoors, and pets. This value was estimated by taking the average fraction of active ingredient on the hands in each dermal study and comparing that value to the average fra ction of active ingredient on the entire body assuming an individual is wearing a t

- shirt and shorts. The fraction of active ingredient available on the hands (Fai hands ) for each scenario is provided in Table 6 .4.5.2.1
below.

Table 6.4.5.2.1. Fraction of active ingredient available on hands

Scenario Fai hands Turf/Lawn Use 0.06

Indoor Use 0.15

Pet Use 0.039



### 6 .4.5.2.2 Fraction of Hand Mouthed per Event (F M 

### )

The fraction hand surface area mouthed value was taken from the Zartarian et al. (2005) analysis of data originally presented in Leckie et al. (2000). The Leckie et al. (2000) study
consisted of a data set of 20 suburban children videotaped outdoors. Par t of the videotape analysis performed by Leckie was to determine the amount of the hand that was mouthed by each child every time a mouthing event occurred. The analysis in Zartarian et al. (2005) consisted of assigning numerical values to each of five scenarios ( outside mouth contact, partial finger, full finger, partial palm with fingers, and partial palm without fingers). It was assumed that each finger is 10% of the hand, and that the surface area of palm that can be mouthed isPyrethroid Cumulative Risk Assessment

Page 68 of 88 25% of the hand. For 1 “partial finger” inserted into the mouth a value of 5% of the hand was selected, 2 partial fingers 10%, et cetera . The fraction of hand mouthed used for all non

- dietary incidental oral ingestion scenarios in this assessment is 0.13.



### 6 .4.5.2.3 Hand Surface Area (SA H 

### )

The hand surface area for 1 to <2 year olds is 150 cm 2 for one hand which is based on data from
the Child

- Specific Exposure Factors Handbook (U.S. EPA, 2008). This value was used for all non

dietary incidental oral ingestion scenarios in this assessment.


### 6.4.5.2.4 Fraction of Pesticide Extracted by Saliva (SE H 

### )

The value for fraction of pesticide extracted by saliva is based on analysis of data collected in a study by Camann et al. (1995). This study focused specifically on fraction o f pesticide extracted by saliva from hands, not objects. The fraction of pesticide extracted by saliva value used for all

non

- dietary incidental oral ingestion scenarios in this assessment is 0.48.



### 6 .4.5.2.5 Exposure Time (ET)

The exposure times used in the assessment of the non

- dietary incidental oral ingestion scenarios is the same as described for 1 < 2 year olds above in Section 3.2.1.2.3 and Table X.



### 6.4.6 Post

- application Incidental Oral Risks

For all scenarios, there are no residential post

- appli cation incidental oral risk estimate s of

concern associated with the registered uses of pyrethroids. All MOEs were greater than the Agency’s target MOE of 300 for children (see Appendix 7 and Table 6 .4.7a ).



### 6.4.7 Combined Exposure

The sections above describe the separate dermal (handler and post

- application), inhalation (handler and post

- application), and non

- dietary oral ingestion (post

- application) assessments that have been performed for the pyrethroids. I n reality, exposures resulting from differ ent routes do not occur as single, isolated events, but rather as a series of sequential or concurrent events that may overlap or be linked in time and space. Based on this, r isk estimates resulting from different exposure routes are combined when it is l ikely that they can occur simultaneously based on the use pattern and when the toxicological effects across different routes of exposure are the same.

Table 6 .4.7a presents the highest estimated risk (i.e., the lowest MOE) for each of the individual

route s of exposure that could occur for a use scenario. It also presents the estimated risks for combining all of the individual routes of exposure within a use scenario. For children (1 to <2 years), all MOEs were above the target MOE of 300 when all routes of exposure were combinedPyrethroid Cumulative Risk Assessment

Page 69 of 88 within a particular exposure scenario. For adults, all MOEs were above the target MOE of 100 when all routes of exposure were combined within a particular exposure scenario.

Table 6.4.7a. Pyrethroid Screening Level Combined R esidential Assessment Within Scenario Results

Lifestage Scenario Handler Post

- application Exposure Route Combined
Within
Scenario Dermal Inhalation Dermal Inhalation HtM

1 < 2 year
olds Turf NA NA 3,000 NA 21,000 2,600 (cyfluthrin)

Pet NA NA 4,200 NA 22000 3,500 (cyphenothrin)

Indoor
Broadcast NA NA 15,000 110,000,000 3800 3,000 (esfenvalerate)

Indoor Fogger NA NA 3,500 NA 900 720 (cypermethrin)

Indoor C&C NA NA 36,000 NA 9,700 7,600 (cyhalothrin)

Adults Turf 9,200 280,000 4,500 NA NA 3,000 (cyfluthrin

- hose

- end

sprayer (cyfluthrin)

Garden 15,000 780,000 1,400 NA NA 1,300 (fluvalinate

- backpack) (fluvalinate)

Pet 27,000 10,000,000 9,800 NA NA 7,200 (permethrin

- shampoo) (cyphenothrin)

Indoor
Broadcast 240,000 760,000 17,000 610,000,000 NA 16,000 (allethrin

- LPHW) (esfenvalerate)

Indoor Fogger NA NA 3,900 NA NA 3,900 (cypermethrin)

Indoor C&C 43,000 140,000 43,000 NA NA 19,000 (cyfluthrin

- LPHW) (cyhalothrin)

Once the screening level values for residential exposure were combined within a use scenario, the next step was to combine scenarios that could potentially co

- occur. For example, a child could be exposed in the same day by contacting a treated pet and a t reated indoor surface. In all cases, the MOE representing the highest residential risk estimate (i.e., the lowest MOE) was chosen to represent each scenario for adults and children (1 to <2 years). For example, there

are a number of pyrethroids registere d for use on turf, but the combined turf cyfluthrin MOEs were used to represent all pyrethroid turf use because cyfluthrin resulted in the lowest combined turf MOEs for adults and 1 < 2 year olds. Although combining scenarios that use high

- end, health pro tective inputs or assumptions is not typically appropriate due to compounding conservatisms, HED performed such a health protective, screening level combined residential exposure assessment for the pyrethroids.

Table 6 .4.7b presents an analysis of a number of scenario combinations. For children (1 to <2 years), all MOEs were above the target MOE of 300 for all of the scenario combinationsPyrethroid Cumulative Risk Assessment

Page 70 of 88 considered. For adults, all MOEs were above the target MOE of 100 for all of the scenario
combinations considered.

Table 6.4.7b. Pyrethroid Screening Level Combined Residential Assessment Across Scenario Results

Lifestage Scenario Combined
Within
Scenario MOE Routes of Exposure Combined Across
Scenarios

1 < 2 year olds Turf 2,600 PD, PHtM
1,000 Pet 3,500 PD, PHtM
Indoor Broadcast 3,000 PD, PI, PHtM
Turf 2,600 PD, PHtM

490 Pet 3,500 PD, PHtM Indoor Fogger 720 PD, PHtM
Turf 2,600 PD, PHtM
1,200 Pet 3,500 PD, PHtM

Indoor Crack & Crevice 7,600 PD, PHtM

Adults Garden 1,300 HD, HI, PD 910 Turf 3,000 HD, HI, PD

Pet 7,200 HD, HI, PD 5,200 Indoor Crack & Crevice 19,000 HD, HI, PD

PD = post

- application dermal exposure, PHtM = post

- application hand

- to

- mouth exposure, PI = post

- application inhalation exposure, HD = handler dermal exposure, HI = handler inhalation exposure. PD = post

- application dermal exposure, PHtM = post

- application hand

- to

- mouth exposure, PI = post

- application inhalation exposure, HD = handler dermal exposure, HI = handler inhalation exposure



### 7.0 Combined Screening Level Dietary + Residential Cumulative

Once the screening level risk estimate s for exposure by the d ietary and residential pathways were calculated, the next step was to combine them into a screening level pyrethroid cumulative assessment. In light of the complexity of the residential use patterns, the Agency elected to take a screening approach to the c umulative assessment, by combining the risk

estimates from the dietary pathway with the highest risk estimates from the appropriate residential pathways. This approach is considered highly conservative and health protective f or reasons outlined in Section 8 .0. The calculations for the screening level cumulative risk
assessment combine the 99.9 th percentile MOE from the diet ary exposure values (see Table

5 .3b) for adults and children (1 to <2 years) with the combined re sidential scenarios (see Table

6 .4.7b).

Table 7 .0 provides a summary of the combined estimated MOEs for adults and children (1 to <2 years). For adults, all of the estimated MOEs are above the target MOE of 100. For children (1 to <2 years), all of the estimated MOEs are above the tar get MOE of 3 00.Pyrethroid Cumulative Risk Assessment

Page 71 of 88 Table 7.0 Pyrethroid Screening Level Combined Dietary/Residential Assessment

Age Group Exposure Route Screening
Combined

MOE (Dietary + Residential) Dietary Residential (non

- dietary)

Scenario MOE (at 99.9 th
percentile) Combined Scenarios (Routes of Exposure) MOE

1 < 2 year
olds
Food+

Water 3,000 Indoor C&C (PD and PHtM) + Pet (PD and PHtM) + Turf (PD and PHtM) 1,200 860

Indoor Fogger (PD and PHtM) + Pet (PD and PHtM) + Turf ((PD and

PHtM) 490 420

Indoor
Broadcast (PD, PI and

PHtM) + Pet PD and PHtM) + Turf PD and PHtM) 1,000 750

Adult 5,400 Turf (HD, HI, and PD) + Garden (HD, HI, and PD) 950 810

Indoor C&C (HD, HI, and PD) + Pet (HD, HI, and PD) 5,100 2,600



### 8.0 Characterizing the Screening

- Level Pyrethroid Cumulative Risk Estimates

This screening

- level pyrethroid cum ulative risk assessment is considered to be a conservative and health protective assessment which likely greatly overestimates exposure and risk. The extent to which the characteristics and assumptions in this cumulative assessment are
considered to be conservative is detailed below. The Agency believes that refinements to address the assumptions discussed below would further support this conclusion.



### 8 .1 Hazard Ch aract erization

The Agency has determined that the pyrethroids and pyrethrins share a comm on mechanism of toxicity through interaction with VGSCs a nd leading to neurotoxicity are generally characterized by two toxicity syndromes (i.e., T syndrome or Type I and CS syndrome or Type II). As discussed throughout this CRA, the current assessment is considered a screening level analysis. In the case of the cumulative hazard assessment, as discussed in Section 2.4, the Agency has elected to combine the Type I and Type II pyrethroids together. Type I and Type II pyrethroids differ in
the duration and nature of VGSC interaction, with Type II pyrethroids causing an elongated open state of the sodium channel compared to the Type I pyrethroids. Behaviorally, the Type I pyrethroids produce hyperreactivity, fine to whole body tremors, and hyperthermia (T

s yndrome) whereas Type II pyrethroids cause salivation, and coarse tremors leading to sinuous writhing termed choreoathetosis (CS syndrome) ( Verschoyle and Aldridge 1980 )

. As such, there is scientific support for considering these pyrethroids in separate sub

- groups if appropriate in
the future

.Pyrethroid Cumulative Risk Assessment

Page 72 of 88 It would be preferred to use an in vivo endpoint related to VGSC interaction

, but at this time
current metho ds do not exist to practically measure such an in vivo biomarker. As such, the Agency must rely on apical endpoints related to neurobehaviors such as tremors, salivation, and changes in body temperature. A n FOB study by the WIL laboratory provides the most complete and most relevant dataset from which to assess and compare pyrethroid toxicities for the purpose of developing the cumulative risk assessment. By incorporating several pyrethroids into a single s tudy, using the same protocol and experimental design, interlaboratory differences (i.e., scoring criteria, vehicle, and vehicle volume) that complicate interpretation of behavioral responses and increase uncertainty when comparing relative potency were el iminated. This FOB study evaluated 46 measures using a standard protocol, with a few modifications to specifically describe behaviors relevant to the pyrethroid toxicity syndromes. Although the pyrethroids produced changes in numerous endpoints
multidime nsional analyses revealed that differential effects were arrayed across four principal components. Of these, differential syndromes could be defined by five FOB endpoints (T: hyperthermia, tremors, clonic convulsions , and CS: hypothermia, salivation, mobi lity); these findings agree well with earlier descriptions of the pyrethroid syndromes.

The Agency has used a refined and novel approach to deriving BMDs for the 11 of the 15 pyrethroids, including the eight most potent, for these neurobehavioral effect s identified in the WIL FOB study. The approach used in the CRA to normalize the data based on relative severity of the effect (i.e., severity scores) is consistent with methods reported in the scientific literature used to differentiate profiles of effec ts for various neurotoxicants ( M oser 1991 ; McDaniel and

Moser 1993 ; Moser et. al. 1995 ) . While the severity scoring approach combines individual effects on specific endpoints, and may thereby lose some resolution in individual differences, it provides more integrated data that may be compared across studies. In addition, the BMD analysis involved a model averaging procedure which was used to derive a 20% BMD estimate

. Due to the limited doses and small samples sizes, this technique was considered more appropriate to account for model uncertainty com pared to the Agency’s Benchmark Dose Software (BMDS) that is more commonly used to determine BMDs for risk assessment. The severity score and modeling average approaches used in this dose

- response result in maximal use of the data from multiple endpoints collected in the WIL FOB study and thus strengthens the relative potency estimates and PoD used in this CRA. The Agency used a less refined approach for four pyrethroids (cyphenothrin, d

- allethrin, imiprothrin, and prallethrin), selecting doses as a point of comparison. However, performing a BMD analysi s is likely to increase the
dose associated with the point of comparison, thereby reducing the RPFs and increasing MOEs.

Because neurobehavior is an apical endpoint, it is important to consider the extent to which these behavioral measures compare to in vitro endpoints measured using neurological tissue cultures and thus are early events in the adverse outcome pathway and biologically closer to VGSC interaction. For example, Losa et. al. (2009) measured sp ontaneous electrophysiological activity of glutamate networks in primary cultures of cortical neurons using microelectro array techniques; and Cao et. al. (2011a) determined sodium flux in primary cultures of cerebrocortical neurons using the Na+ sensitive dye SBFI. The results of these in vitro techniques are similar to the Agen c y’s RPF estimates from the WIL study; T ype II pyrethroidsPyrethroid Cumulative Risk Assessment

Page 73 of 88 are generally more potent th an the Type I pyrethroids. There is a remarkable similarity in the
relative rank of the in vitro measures to the RPFs based on FOB measures. These comparisons, thus, support the use of the behavioral measures for purposes of estimating cumulative risk.

a Included in study but effective concentration estimates could were not determined due
to minimal increase in Na+ influx

The Agency is using a single set of RPFs estimated for oral exposure for all relevant routes of exposure (oral, dermal, inhalation) and thus the Agency is assuming that the relative ranking o f these oral RPFs applies to the other routes of exposure . The Agency has dermal and inhalation studies available for only a limited number of pyrethroids, and of those studies, neurological endpoints are not measured in a consistent manner nor are critical procedures, such as the
determination of time

- to

- peak effect determined. Therefore, these dermal and inhalation studies are not appropriate for use in the determination of relative potency factors for the pyrethroids. However, the lack of these studies does not introduce significant uncertainty because pyre throids are generally poorly absorbed through the skin and inhalation exposure is
believed to be low. As described in Section 6.0 of this assessment, dermal and inhalation MOEs for the pyrethroids are large, ranging from 3,000 to 240,000 for dermal exposu res and 130,000 to 10, 000,000 for inhalation. Based on these values, the RPFs would have to be at least an order of magnitude greater than the index chemical to result in significant risk estimates

.

The selection of the index chemical is a key decisio n point in the cumulative risk assessment as any uncertainty in the index chemical’s dose

- response data will be propagated through the
entire risk assessment

. For the CRA, deltamethrin was chosen as the index chemical because it provides robust dose

- respo nse data from which to estimate the PoD. Specifically deltamethrin was tested in the WIL FOB study with three well

- spaced doses which include a dose near the

BMD 20 such that high confidence BMD 20 and BMDL 20 estimates can be estimated , as indicated Table 4.5.1. Relative Potency Estimates for Pyrethroids Included in the Screening Level Cumulative Risk Assessment Pyrethroid WIL FOB Losa et. al. ( 2009 ) Cao et. al. ( 2011a )

Allethrin c 0.11 0.11 0.68
Bifenthrin 1.01 0.40

- a Cyfluthrin 1.15 0.57 0.61
Lambda

- Cyhalothrin 1.63 7 0.58 Cyphenothrin 0.15 Not Included Not Included Cypermethrin 0.19 0.97

- Deltamethrin 1.0 1.0 1.0
Esfenvalerate 0.36 0.22 0.49 Fenpropathrin 0.50 0.12 0.31

Tau

- Fluvalinate 1.0 Not Included Not Included Imiprothrin 0.02 Not Included Not Included

Permethrin 0.09 0.24

- Prallethrin 0.10 Not Included Not Included Pyrethrins 0.02 Not Included Not Included
Resmethrin 0.05 0.10

-Pyrethroid Cumulative Risk Assessment

Page 74 of 88 by clos ely spaced BMD and BMDL estimates . Furthermore, deltamethrin was used as a laboratory method control in the second phase of the WIL study ( Herberth 2010 ) and the findings were similar between studies. For example, at a given dose of 25 mg/kg

, salivation was noted in six animals for each study, altered gait was observed in nine animals in the first and six
in the second study, and finally low arousal or response was observed in four animals in the first study and in two animals in the second. In addition, deltamethrin is a commonly studied pyrethroid in research laboratories such that a large collection of literature studies is available, including a well

- developed PBPK model.

Dose

- additivity is the foundation assumption when using a RPF ap proach. At this time, there is

an 11

- chemical mixture in vivo study evaluating motor activity and one in vitro stud y measuring
sodium influx in cerebrocortical neurons for the same 11

- pyrethroid mixture. Each study is consistent in finding no deviation from the dose

- additive model and thus supports the use of the RPF approach.

It is preferred to use a PBPK model to derive RPFs based on internal dosimetry instead of the

a dministered dose metrics used in this CRA. The Agency has already developed PBPK models for permethrin and deltamethrin capable of extrapolating across species (Godin et. al. 2010) and age groups in rats (Tornero

- Velez et. al. (2010). There is currently a large effort by CAPHRA to develop PBPK models relevant for assessing estimated risk to children 4

- 6 additional pyrethroids. These models have the potential to improve the CRA by refining the metric used to estimate RPFs and by better informing route to route extrapolation, high to low extrapolation, animal to human extrapolation, and potential for PK

- driven age

- dependant sensitivity.

The Agency has high confidence in t his cumulative hazard assessment for the pyrethroids

. The
cumulative assessment is co nsidered protective given that both Type I and Type II pyrethroids
were included. Furthermore, there is a high level of confidence in the selection of the WIL FOB study for BMD determinations due to the high quality of the study, because it is supported b y in
vitro studies that measure effects at the level of the common mechanism, and the robust dose

response analysis. Finally

, the retention of the 3X FQPA safety factor for children < 6 years of age based on pharmacokinetic data, PBPK models, and establis hed data (e.g., g uideline and literature studies) is protective of the most susceptible population. As new data become
available , particularly PBPK models , the Agency may, if appropriate, refine approaches or assumptions used in this assessment.Pyrethroid Cumulative Risk Assessment

Page 75 of 88 

### 8 .2 D ietary Exposure Assumptions and Characterization

8 .2.1 Food Exposure Pathway

To provide risk estimates for the dietary portion of this cumulative risk assessment, the Agency conducted a refined, probabilistic dietary assessment and the food component of t hat assessment relied on PDP monitoring data. The food component of the assessment is considered a refined picture of potential acute food exposures for the U.S population and regulated subpopulations. However, two conservative assumptions were made in t his assessment. The first assumption was that available residue data were translated to all food commodities in DEEM regardless of registered use pattern. The second assumption was that processing factors, which reflect potential reduction of pesticide r esidues, were not incorporated into the assessment. Incorporation of reduction factors and eliminating foods for
wh ich there are no registered use are expected to reduce dietary risk estimates.



### 8 .2.2 Drinking Water Exposure Pathway

The pyrethroids as a class have low water solubility and tend to bind to soil. As a result of these properties, exposure from the drinking water pathway is expected to be negligible. However, in the absence of a robust set of monitoring data or refined m odeling to support this contention, the Agency has taken a highly conservative approach to address drinking water exposure in this screening level cumulative assessment. The single highest modeled drinking water exposure
estimate in terms of index chemica l equivalents was used in the assessment for all water consumption for an individual. The Agency believes that this a health protective approach to the screening level assessment and likely to overestimate dietary risks. It is more likely that if adequat e monitoring data were available, actual concentrations of pyrethroids in water would be significantly lower than the modeled values and that risk estimates from water consumption would more closely follow the food only risk estimates reported in this docu ment.



### 8 .3 Non

- Dietary Exposure Assumptions and Characterization

Limiting the Assessment to Insecticide

- and Pyrethroid

- Users

In standard cumulative assessments, dietary plus non

- dietary aggregate exposures reflect those
individuals who use pesticide products and those who do n o t. That is, those with exposures via the dietary route may or may not have exposures from the non

- dietary route, depending on whether they are users of pesticides (in this case pyrethroid insecticides, specifically). The

curre nt screening

- level approach represent s risk estimates for individuals (adults and children) exposed via dietary consumption of pyrethroid residues as well as contacting, and potentially ingesting, surface residues (i.e., non

- dietary exposure) . However, ba sed on EPA’s recently
released 2006

- 2007 market estimates for pesticide sales and usage (http://www.epa.gov/opp00001/pestsales/07pestsales/producers_users2007.htm#4_1), approximately 50% of U.S. households do not use insecticides. Furthermore, though like ly a large portion of the residential use market, it is reasonable to assume that market share ofPyrethroid Cumulative Risk Assessment

Page 76 of 88 pyrethroids is less than 100%. Since the screening

- level assessment aggregates dietary and

non

- dietary exposure, it does not reflect the substantial portion of the U.S. population with pyrethroid

- related dietary exposure, but without pyrethroid

- related non

- dietary exposure. Thus, the current approach implicitly represents a population in which 100% experiences both dietary and non

- dietary pyrethroid exposure. In a true population

- based probabilistic assessment, approximately 50% of the modeled population would have only dietary exposure to pyrethroids, while the other 50% would experience both dietary and non

- dietary pyrethroid exposure (per the estimate abov e). And, since those without non

- dietary exposure would have correspondingly lower exposures and risk estimates , the overall distribution of exposure and
risk estimates would be lower. Incorporating the likelihood of insecticide use, and

, more specifical ly

, pyrethroid use

, would result in a lower estimate of risk than the current approach.

Limiting Non

- Dietary Exposure to the “Day

- of

- application”

The screening

- level approach estimates non

- dietary exposure using surface residues immediately following pyr ethroid applications. While it is certainly the case that individuals may be exposed in this fashion, this approach does not consider the likelihood of exposures resulting from surface residues that have dissipated over time. If applications are made eve ry day or if there is no dissipation of pyrethroid residues in and around homes, estimates based on the “day

- of

- application” would be representative of non

- dietary exposures. However, given available pesticide use data (e.g., REJV) and known pyrethroid di ssipation rates, utilizing “day

of

- application” exposures is a conservative approach. A refined assessment would utilize a
calendar

- based approach that specifies dates of application (based on use probabilities) and incorporates residue dissipation. EPA’ s Stochastic Human Exposure and Dose Simulation (SHEDS) model, for example, utilizes diaries from the Consolidated Human Activities Database (CHAD) to more accurately reflect the coincidence of applications and individuals’ locations and
activities. Utili zing this methodology would reflect exposure to residues that have dissipated 5, 10 or 20 days after pyrethroid applications and result in a lower risk estimate than the current approach.

Consideration of Pyrethroid

- Specific Use Probabilities

The scree ning

- level approach presents non

- dietary risk estimates for only one pyrethroid for each of the major residential use scenarios. This should not be construed to imply that only one pyrethroid has uses for that scenario, or that this does not represent a c umulative methodology. Rather, the pyrethroid presented is the “highest potential risk” pyrethroid for each scenario, thus serves as a conservative benchmark to address each non

- dietary scenario. For example, risk estimates for the pyrethroid cyfluthrin are presented for non

- dietary exposures resulting from applications to home lawns since cyfluthrin results in the highest risk

estimate of the pyrethroids registered for use on turf. Similarly, cyphenothrin is used as the benchmark pyrethroid for those wi th registrations for household pets. In reality, however, there are many different pyrethroids registered for each residential use scenario, with each pyrethroid having a particular share of the consumer market for each use. It may be the case that thoug h cyfluthrin presents the highest risk estimate for a pyrethroid with lawn uses, it isPyrethroid Cumulative Risk Assessment

Page 77 of 88 the lawn

- use pyrethroid used most infrequently. Thus, utilizing cyfluthrin as the benchmark pyrethroid for the lawn

- use scenario is a conservative approach. A refined assessment that accurately assigns pyrethroid

- specific residential scenario market

- share probabilities would
result in lower risk estimate s than the current approach.

Assuming Co

- Occurrence of Non

- Dietary Exposure Scenarios

The screening

- level appro ach presents risk estimates separately for each individual residential

use scenario, then presents an aggregate risk estimate that assumes an individual is exposed from all of the scenarios on the same day. For example, risk estimate s are presented for
ch ildren 1 < 2 years old exposed via contact with surfaces previously treated indoors (broadcast sprays, total release fogger, and “crack and crevice”) as well as contact with previously

- treated lawns and pets. These separate risk estimates are then aggrega ted, which assumes a) each of those areas are treated on the same day, b) each is treated with the use

- specific “ highest potential risk ” pyrethroid, and c) children contact those areas on the “day

- of

- application”. A refined approach would more accurately reflect the likelihood of experiencing pyrethroid exposure in this

– likely improbable

– co

- occurrent fashion by incorporating its probability based on pesticide use surveys. The current approach conservatively assumes that these scenarios always co

- occur (i.e., 100% co

- occurrence probability). Any refinement which
reduces co

- occurrence would result in a lower risk estimate.



### 8. 4 Aggregate Exposure (Dietary + Non

- Dietary) Assumptions and
Characterization

The Agency considers this screening

- level cumulati ve risk assessment to be highly conservative. The screening

- level approach utilizes a simple point

- estimate aggregate methodology that adds a high

- end dietary (food and water) exposure to a high

- end residential exposure, assuming co

occurrence of dietary and non

- dietary exposure. In other words, the non

- dietary exposure patterns discussed in Section 6.0 would coincide with consumption of food and water (discussed in Section 5.0 ) with pyrethroid residues. While this is a possible exposure pattern, it
is h ighly unlikely given the temporal aspects of residential insecticide use. Not only does this
assessment assume and model co

- occurrence, it utilizes high

- end exposures from both the dietary and non

- dietary pathways, making this outcome even less likely. A refined cumulative assessment would incorporate the appropriate temporal matching of exposures through these
different pathways and reflect more realistic probabilities that pyrethroid exposure results from both dietary and non

- dietary routes on the same day . Additionally, the use of distributions of both dietary and non

- dietary exposures would mitigate the compounding effect of aggregating high

- end point estimates.Pyrethroid Cumulative Risk Assessment

Page 7 8 of 88 

### 9.0 Conclusion

The assessment combines a high

- end dietary risk estimate from a probab ilistically

- derived realistic food exposure estimate and a high

- end modeled drinking water exposure estimate with a high

- end deterministic non

- dietary residential risk estimate

. The refinement of each pathway varies and has been described previously in ea ch respective section. However, given the various assumptions outlined in Section 8.0, the overall methodology provides a reasonabl y conservative s creening

- level approach for determining cumulative and aggregate estimated risk for pyrethroids

. The current use of high

- end exposure estimates, the general assumption of co

exposure, and compounding conservative assumptions for each exposure route would likely represent an upper percentile exposure of a fully refined cumulative assessment (i.e., likely

g reater than the 99.9 th percentile). That is, further refinements would result in MOEs significantly above those reported here. However, since risk estimates exceed the Agency’s target MOEs for adults and children , additional refinement is not required at this time.

This screening level CRA for pyrethroids uses deterministic residential and probabilistic dietary exposure models. There are alternative approaches that would be more refined, particularly the use of probabilistic estimates for all routes of exposure. OPP and ORD are working collaboratively to improve the Stochastic Human Exposure and Dose Simulator (SHEDS) model,

spec ifically for use in such a refined risk assessment. Moreover, this collaborative effort involves linking PBPK models with the SHEDS model to estimate probabilistic population level
risk. The linking of a PBPK model with a probabilistic exposure model may provide opportunities to calculate distributions of exposure to pesticides with effect levels across the U.S. population. In addition, this approach may allow estimation of data

- derived uncertainty factors that consider use of toxicokinetic and toxicodyn amic data to inform quantitative extrapolations for interspecies differences and human variability in dose response assessment. This research effort was reviewed by a FIFRA SAP in July , 2010 5

. In addition, the SAP also
reviewed in February, 2011 Chlorpyri fos Physiologically Based Pharmacokinetic and Pharmacodynamic (PBPK/PD) Modeling Linked to Cumulative and Aggregate Risk Evaluation System (CARE S) in which the CARES model was similarly linked to a PBPK/PD model in an effort made by Dow AgroScience 6

Not only does the Agency believe that this screening level estimate indicate s that there are no
cumulative estimated risks of concern for the cu rrently registered uses, the Agency also concludes that there is sufficient room in the pyrethroid cumulative risk cup to support consideration of new pyrethroids (i.e., currently unregistered pyreth r oid pesticides) and new uses of existing pyrethroids hav ing similar toxicity profiles and use patterns to those in this . OPP supports such research efforts as they advance the science of
risk assessment. However, consistent with the screening approach of this cumulative assessment, such a highly refined and sophisticated approach is not needed at this time for pyrethroids. In the future, OPP may consider, if appropriate, similar research for pyrethroids or other classes of pesticides.

5 http://www.epa.gov/scipoly/sap/meetings/2010/072010meeting.html

6 http://www.epa.gov/scipoly/sap/meetings/2011/021511meeting.htmlPyrethroid Cumulative Risk Assessment

Page 79 of 88 assessment. This is a screening level assessment which incorporated multiple high

- end inputs and combined the highest exposures/risk estimate s across all pathways in a deterministic
fashion r esulting in an assessment which is highly conservative and health protective. It is important to note that the pyrethroids are already registered on virtually all food crops and for all major residential use scenarios. The dietary component of the cumula tive risk assessment
included residues for all foods consumed

– either based on monitored values or translation from monitoring data from crops in the same food group. The water exposure input was assumed to be the highest exposure value from conservative model outputs which was the limit of solubility for that specific chemical . Additionally, the residential scenarios used conservative inputs and combined in a deterministic fashion exposure from multiple residential pathways of exposure, assuming use of the most potent pyrethroid, to produce a highly conservative
estimate of risk.

For any new uses or new pyrethroids, the toxicity, proposed use sites, and potential exposure factors (e.g., application rate) would be compared with the inputs and assumpti ons utilized in this screening level assessment. However, if the pyrethroid is not significantly more toxic than those included in this assessment and has a similar use pattern to those registered uses considered in this assessment, its registration would likely be supported from a cumulative human health risk perspective because its inclusion within this assessment would not result in a higher estimate of risk than has been currently estimated. Per Agency policy, all new uses/new pyrethroid registration actions submitted to the Agency will undergo a single chemical assessment and also an evaluation of their potential contributions to cumulative risk estimates

. But the Agency believes that most of these are unlikely to have a significant impact on this screening

- level cumulative assessment, provided they meet the parameters outlined above.Pyrethroid Cumulative Risk Assessment

Page 80 of 88 

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