UNITED STATES ENVIRONMENTAL PROTECTION AGENCY WASHINGTON, D.C. 20460 

### APR 24 2013

OFFICE OF CHEMICAL SAFETY AND POLLUTION PREVENTION


### MEMORANDUM
SUBJECT:
FROM:

THRU: [REVISED] Application Rate Information for Uses ofRO-PEL, a Ready-To-Use Liquid Bittering Agent Containing Denatonium Saccharide (PC Code 129045) Jonathan Becker, Senior Science Advisor 

# l /J 

# jjJ,___ Biological Analysis Branch 

# C '/ Biological and Economic Analysis Division (7503P) Amet Jones, Chief Biological Analysis Branch 

### TO: Andrea Mojica, Chemical Review Manag Risk Management and Implementation Branch 4 Pesticide Reevaluation Division (7508P) 

### ProductReview PanelDate: 10 April 2013


### SUMMARY BEAD recommends that the following application rate estimates be used for the risk assessment ofdenatonium saccharide: as a bulb treatment (6 x 10·6 lbs a.i. perbulb); as a seed treatment (3 x 104 lbs a.i. per 1,000 ft2); and for all residential treatments combined (1 gallon ready-to-use liquid or 5.4 x 

### 10-3 lbs a.i. per residence).


### INTRODUCTION This document provides estimates ofthe application rate for labeled uses ofRO-PEL, a ready-touse formulation ofdenatonium saccharide. Estimates for these use sites (seed and bulb treatments), and as well for all residential uses combined, may be used in the ecological risk assessment for denatonium saccharide.

1Denatonium saccharide (PC code 129045) is an extremelybitter chemical that is used as an animal repellent. This active ingredient has one registration (Reg. No. 81117-1) and several products are marketed, such as "RO-PELTree Squirrel, Vole, Dog and CatRepellent" and "Four Paws Keep Off! Dog and Cat Repellent"
. These products are ready-to-use liquids and contain 0.065% denatonium saccharide. Although not explicitly stated on the product labels, both products appear to be used only in outdoorresidential settings, eitherbythe homeowner orby a commercial contractor. Please note that the brand name "RO-PEL" is used for products that do not contain denatonium saccharide. The FourPaws product label provides specific application rate information and will notbe discussed further. The RO-PEL product label allows application to outdoor structures and surfaces (e.g., tree bark, decks, and planters) and the application rate for this use is adequate (1 gallon covers 1,000 to 4,000 square feet). Each gallon ofReady-To-Use RO-PEL contains 0.0054 pound denatonium saccharide (0.065% a.i. x 8.34lbs per gallon=0.0054lbs a.i.). This product is also labeled as a bulb and seed treatment to reduce consumption and damage by tree squirrels and voles. The directions for these uses only state "Using rubber gloves, place seeds orbulbs in a plastic or metal container and spray thoroughly until soaked." No further application information is provided on the label. Based on extension service and trade organization information, as well as bestprofessionaljudgment, BEAD provides application rate estimates for these uses. BEAD uses water as a surrogate for the 0
.065% RO-PELready-to-use formulation in developing these estimates
. Further, BEAD assumes that the entire amount ofthe ready-to-useformulation is applied to seeds and bulbs with no loss. This would never occur during actual use as there would always be significant loss from residual spray in the containers. This assumption further adds to thehigh-end nature ofthese estimates.

BULBS The application rate per bulb may be calculated using the amount ofliquid applied to eachbulb, then applying unit conversions to determine the lbs a.i
. perbulb. Krug et al. (2005) reported the volume ofliquid applied perbulb for a similar application method (hyacinth bulbs soaked in a dip solutionfor 10 minutes). Krug (2005) found that on average, each bulb utilized 4 to 8 ml ofsolution (or 470 to 950 bulbs per gallon). Significantly smaller amounts would be needed whenusing a sprayer. This is because Krug (2005) completely submerged each bulb for at least 10 minutes, allowing for a much greater penetration and retention ofthe solutionby eachbulb than could be achieved from application by a sprayer.

2A conservative estimate based on Krug (2005) would be that 4 ml perbulb is the greatest amount that could be applied by sprayer to each bulb. The amount ofdenatonium saccharide perbulb may be calculated as: 4ml bulb 1 gallon 3,785.41 ml 8.345 lbs 

### a. i.

----- . 0.065% 1 gallon 6 :X 10-6 lbs a. i. bulb



### SEEDS A similar approach may be used to calculate the application rate for seed treatments; however, the units will be expressed in lbs per ft2 to account for the number oftreated seeds planted. The RO-PEL label does not specify the types ofseeds (i.e., plant species) that canbe treated with this product. BEAD selected bare (i.e., uncoated) turfgrass seed to represent the high-end application rate for this use. Grass is the most commonly planted seed around residences. Grasses planted in residential areas have large number ofseeds per pound and are planted at a high seeding rate (Table 1). The aggregate surface area ofthe grass seeds is greater than any other seed planted 

### ill residential areas and will therefore result inthehighest applicationrate ofRO-PEL per unit area. Table 1. Number ofseeds per pound and recommended seeding rates for common turfgrass species (Voight, no date; Trenholm, 2009; Stahnke, et al. 2010).
Grass Approximate Number of Seedingrate (lb I 1000 ft2) Seeds Per Pound Tall fescue 178,000-234,000 6 to 9 (Festuca arundinacea and Latium arundinaceum) Perennial ryegrass (Loliumperenne) 210,000-270,000 3 to 5 Red fescue (creeping) (Festuca rubra var. rubra) 365,000 3 Chewings fescue (Festuca rubra var. commutata) 449,000 3 Hard fescue (Festuca ovina var. duriuscula) 592,000 3 Kentucky bluegrass (Poa pratensis) I,022,000-1,758,000 I to 3 Colonial bentgrass (Agrostis tenuis) 6,130,000 0.75 to 1.5 Note: Grass seed w1th the greatest number of seeds per pound IS not planted usmg the h1ghest seedmg rate. An optimal density ofseeds per in2 is targeted for each type ofgrass, so seed lots with a smaller number of seeds per pound are planted at a higher seeding rate and vice versa. BEAD has no empirical information related to the amount of solution required to thoroughly soak grass seed and translate this into an application rate. However, an estimate maybe made using the surface area ofgrass seed and the area that can be covered by a given amount of solution (label information). When these values are combined with information from Table 1 and unit conversion factors are applied, an application rate per unit area may be estimated.



### 3The steps necessary to calculate this estimate are as follows.
• Calculate the surface area ofa hypothetical grass seed • Calculate the thickness ofspray on a surface (i.e., film thickness) • Calculate the volume ofliquid to cover one seed • Calculate the amount ofgrass seed to plant 1,000 

### ft2• • Calculate the amounts ofRO-PEL (and lbs a.i.) needed to treat these seeds at the application rate per 1,000 

### ft2• Calculations ofthe surface area ofa hypothetical grass seed Undersander et al. (1996) describes the various grasses and their seeds. Grass seed is elongated with both ends tapering to a point. The surface area ofa hypothetical grass seed may be calculated assuming that the seed roughly parallels the geometric shape oftwo conesjoined together at the base. The surface area ofthis shape (note that the surface areas ofthe bases are not included) maybe calculated as follows. 

### 2nrs Where r = radius and s = length ofthe side ofone cone. The value for s may be determined by the Pythagorean Theorem. Using the dimensions ofa hypothetical grass seed (1 mm in diameter (a= 0.5 mm), 3 mm in length (b=1.5 mm), the value ofs (i.e., c in the above equation) is (0.5 mm)2

### + (1.5 mm)2 

## = 2.5 mm2and c = .J2.s mm2 = 1.58mm The surface area is calculated using 2ms as 2 · 3.1416 · 0.5 mm · 1.58mm 

### = 4.97 mm2 Calculations to determine the thickness ofspray on a surface (i.e
.. film thickness) The RO-PEL label states that one gallon will cover 1,000 to 4,000 

### ft2

. Thethickness ofthe film on the treated surface for these two rates maybe calculated using the following equations.
1 gallon 3785411.78 mm3 1 ft2

. . 1,000 ft2
. 1 gallon (US Liquid)
. 92903.04mm2 

### = 0.0407 mm film thickness 1 gallon 3785411.78 mm3 1 ft2

. 4,000 ft2
. 1 gallon (US Liquid)
. 92903.04mm2 = 0.0102 mm film thickness

4These calculated values are close to the water film thickness values reported inEPA's Exposure Factors Handbook (EPA 2011). Thereported values in this document range from 0.0132 to 0.0499mm. Calculation ofthe volume ofliquid to cover one seed The amount ofliquid that is required to completely cover one seed is determined bymultiplying the surface
.area ofone seed bythe film thickness ofthe spray using the values calculated above. At the high treatment rate (1,000 ft2 per gallon) 

## • 4.97 mm2 0.20 mm3

1 d · 0.0407 mm 

## =

see 1 seed At the low treatment rate ( 4,000 ft2 per gallon) 4.97 mm2 0.051 mm3

1 d · 0.0102 mm = --"""":"'-

see 1 seed Calculation ofthe amount ofgrass seed to plant 1.000 ft2• Using the seeding rates and the number ofseeds in a pound for Red Fescue (a common turfgrass species planted around residences) from Table 1, the number ofseeds needed to plant 1,000 ft2 is 3 lbs seed 365,000 seeds 1,095,000 seeds 1,000ft2 lb seed 

## =**--:--:--:-:--~-** 1,000ftZ Calculation ofthe amounts ofRO-PEL (and lbs a.i.) needed to treat these seeds at the application rate per 1.000 ft2• At the high treatment rate (1 gallon covers 1,000 ft2) 1,095,000 seeds 0.2 mm3 1,000ft 2 1 seed
0.058 gallons RO -PEL 1,000 {t2 1 gallon 0.058 gallons RO -PEL 

## = ---------- 3,785,411.78 mm3 1,000 {t2

8.345 lbs
. 0 

### so _ 3 x 10-4 lbs a. 

### i. 1 gallon O
. 6 Yo - 1,000ft 2 Atthe low treatment rate (1 gallon covers 4,000 ft2) 1,095,000 seeds 0.051 mm3 1,000ft 2 • 1 seed 0.015 gallons RO- PEL 1,000 {t2 1 gallon 0.015 gallons RO -PEL 

## =**--~--~---** 1,000ft 2 3,785,411.78 mm3 8.345 lbs
. 0650 _ 8 x 10-5 lbs a. 

### i. 1 gallon O
. Yo - 1,000ft2 

### 5Alternatively, one gallon ofRO-PEL would treat enough seed to plant 17,000 to 67,000 ft2 of turf.

AMOUNT USED PER RESIDENCE Given that RO-PEL could be applied to several different sites around a residence, a "per residence" application rate may beuseful. An amount ofRO-PEL applied perresidence may be projected based onthe application rates calculated above for bulbs and grass seed and the label information describing the rate when applied to surfaces. Given the following:

• Only a small portion ofoutdoor surfaces (e.g., the edges ofa deck) require treatment to deter chewing by rodents • The application rates for grass seed and bulbs estimated above are high-end values • The median lot size in the United States is 0.25 acres (=10,890 ft2>(Census, 2011). To estimate the potential size ofa lawn the footprint ofthe house, driveway, and sidewalks need to be subtracted from this value • The retail cost ofRO-PEL ranges from $25 for 24 fluid ounces (Sears 2013) to about $50 per gallon (Nixalite 2013). This substantial cost ia a further indication that this product is intended for homeowner use. BEAD recommends that 1 gallon ofRO-PELready-to-use liquid per residence beused as a reasonable high-end estimate.

SUMMARY 

### I RECOMMENDED VALUES BEAD recommends the following reasonable high-end estimates be used for the risk assessment ofdenatonium saccharide:

• As a bulb treatment: 6 X 10-6 lbs a.i. perbulb • As a seed treatment: 

### 3 x 104 lbs a.i. per 1,000 ft2 • For all residential treatments combined: 1 gallon ready-to-use liquid or 5.4 x 10-3 lbs a.i. per residence.
REFERENCES Census. 2011. Table C-02-AH. American Housing Survey for the United States. Series H-150, United States Census Bureau, U.S. Department ofCommerce. Krug, B., B. Whipker and I. McCall. 2005. Bulb soak basics. Greenhouse Product News. Oct. 2005. Available at: http://www.gpnmag.com/sites/defaultlfiles/bulbsoakbasics.pdf 

### 6Nixalite. 2013. Nixalite ofAmerica, Inc. website. Available at: http://www.nixalite.cornlropel.aspx Stahnke, G.K., E.D. Miltner, R.C. Puyallup, R.C. Golembiewski, T.A. Salaiz, and W.J. Johnston. 2010. Ttnfgrass SeedingRecommendation<; for the Pacific Northwest Pacific Northwest Extension Publication 299. Available at:http:!/horticulture.oregonstate.edu/content/turfgrass-seeding-recommendations-pacificnorthwest-0 Sears. 2013. Sears website. Available at: http://www.sears.com/search=four+paws+pet+products+keep+off+indoor+and+outdoor+ dog+and+cat+spray+repellent+24+oz?vName=Pet+Supplies&cName=Dog+Supplies&au toRedirect=true&viewItems=25&redirectType=CA T REC PRED Trenholm, L.E. 2009. Establishing Your Florida Lawn. Publication #ENH-03. Florida Cooperative Extension Service, Institute ofFood and Agricultural Sciences, University of Florida. Available at: http://edis.ifas.ufl.edu/lh013 Undersander, D. , M. Casler, and D. Cosgrove. 1996. Identifying Pasture Grasses. Publication Number A3637. University ofWisconsin Cooperative Extension. USEPA. 2011. Exposure Factors Handbook: 2011 Edition. National Center for Environmental Assessment, U.S. Environmental Protection Agency, Washington,**DC~** EPA/600/R09/052F. Available from the National Technical Information Service, Springfield, VA, and online at http://www.epa.gov/ncea/efh
. · Voigt, T. No date. Turfgrass Establishment. Turfgrass Extension & Outreach, Department of Natural Resources and Environmental Sciences, University ofIllinois at UrbanaChampaign. Available at: http://www.turf.uiuc.edu/extension/ext-estab.html



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