UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON D.C., 20460 

OFFICE OF 

PREVENTION, PESTICIDES AND 

TOXIC SUBSTANCES 

PC Code 097805 

DP Barcode D335 136 

MEMORANDUM 

DATE: April 24, 2007 

SUBJECT: Tier I Estimated Drinking Water Concentrations of Deltamethrin for the Use in 

the Human Health Risk Assessment: 1R-4 Tolerance Petition for the Use of 

Deltamethrin on Flax 

TO: Shaja Brothers, Risk Manager Reviewer 

Barbara Madden, Team Leader 

Dan Rosenblatt, Chief 

Risk Integration Minor Use and Emergency Response Branch 

Registration Division (7505P) 

AND: Christina Schwartz, Chief 

Registration Action Branch I1 

Health Effects Division (7509P) 

.-. + ,%& ,YLd& )?&&&& 

FROM: Jose Luis Melendez, Chemist d 

Environmental Risk Branch V 

Environmental Fate and Effects Division (7507P) 

+/ 25/07 

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

Environmental Risk Branch V 

Environmental Fate and Effects Division (7507P) 

This memo presents the Tier 1 Estimated Surface Drinking Water Concentrations and Estimated 

Ground Drinking Water Concentrations (EDWCs) for deltamethrin, calculated using the Tier I 

aquatic models FIRST and SCIGROW, respectively, for use in the human health risk assessment. 

The Estimated Drinking Water Concentrations (EDWCs) for deltarnethrin were calculated based 

on a maximum application rate of 0.45 lb a.i./A/season. The acute drinking water concentration 

in surface water is 200 ppt of deltamethrin, based on applications of the chemical to sweet corn. 

The cancerlchronic drinking water concentration is 77.1 ppt (based on applications to sweet corn, 

with the highest application rate). The SCIGROW generated EDWC is 200 ppt of deltamethrin, 

which is recommended for use, both for acute and chronic exposures. Both, the acute surface 

TEXT SEARCHABLE DOCUMENT
drinking water concentration, and the ground drinking water concentration were limited by the 

solubility of deltamethrin. Should there be a need for additional refinements, the EFED can 

perform a Tier I1 aquatic assessment, for surface waters. 

Data gaps: 

All data requirements for terrestrial food uses are satisfied. However, the registrant submitted a 

supplemental aerobic aquatic metabolism study that yielded two very different half lives. The 

uncertainty lead to a more conservative input in the FIRST model. 

EXECUTIVE SUMMARY 

Deltamethrin, CAS Name: (8-cyano(3-phenoxypheny1)methyl (1 R,3R)-3-(2,2-dibromoetheny1)- 

2,2-dimethylcyclopropanecarboxylate, IUPAC Name: (8-a-cyano-3-phenoxybenzyl (1 R,3R)-3- 

(2,2-dibromovinyl)-2,2-dimethylcyclopropanecarboxylate or (8-a-cyano-3-phenoxybenzyl (1 R)- 

cis-3-(2,2-dibromovinyl)-2,2-dimethylcyclopropanecarboxylate; CAS No. 529 18-63-5, and PC 

Code 097805, is a synthetic pyrethroid insecticide. Its structure has three rings, two phenyl rings 

attached to each other by an oxygen, and a cyclopropyl ring. The chemistry of deltamethrin may 

be dictated by its ester moiety. The molecule has some chiral centers that results in 

stereoisomers. Chemically, it is the [lR, cis; alpha S]-isomer of 8 stereoisomeric esters of the 

dibromo analogue of chrysanthemic acid, 2,2-dimethyl-3-(2,2-dibromovinyl) cyclopropanecarboxylic acid (Br2CA) with alpha-cyano-3-phenoxybenzyl alcohol. 

Deltamethrin is a neural toxic insecticide acting through direct contact and ingestion, having a 

slight repellent effect. The primary biological effects of deltamethrin and other pyrethroids on 

insects and vertebrates reflect an inhibition of the correct firing of neurotransmitter deliver 

signals from one cell to another via nerve membrane inhibition of the voltage-gated ca2' 

channels (calcium ion channels) coupled with a stimulatory effect on the voltage-gated ~a' 

channels (sodium ion channels). All pyrethroids act as axonic poisons, affecting both the 

peripheral and central nervous systems, and share similar modes of action. Pyrethroids, 

including deltamethn, stimulate repetitive action in the nervous system by binding to voltagegated sodium channels, prolonging the sodium ion permeability during the excitatory phase of 

the action potential. This action leads to spontaneous depolarizations, augmented 

neurotransmitter secretion rate and neuromuscular block, which ultimately results in paralysis of 

the insect. 

In 1997 survey, deltamethrin was used essentially only in the South (Texas) and Southeast, in the 

cottonbelt. All the use of the chemical was due to cotton. Today, various crops are registered for 

use of this chemical. Deltamethrin may be used on corn, sweet corn, sorghum, soybean, pome 

fruits, and fruiting vegetables among others. The proposed use under consideration is an IR-4 

tolerance petition for the use of deltamethrin on flax. It should be applied at 0.02 lb a.i./A/ 

application, with a maximum of two applications at the maximum label rate, and a 7-day interval. 

The PHI is 2 1 days. Deltamethrin may be applied by aerial or ground equipment. There are two 

products that contain deltamethrinn involved in this action: DECISB 0.2 EC Insecticide and 

DECISB 1.5EC Insecticide. 

The models used in this screening level drinking waters assessment were FIRST v. 1.1.0 and 

SCIGROW v.2.3, for surface and ground waters, respectively. It was found that, despite the fact 

that the PCA was only 0.46 for sweet corn (assumed to be the same than for field corn), 

2 
compared to the national default of 0.87, it was the worst case scenario, with 16 applications, at 

0.028 lb a.i.lA1 application at 1 day interval. 

Even though some degradates were observed in the laboratory (3-PBA, 3-PBaldehyde, 

tetramethrinic acid), it was found that they were the result of the rupture of the ester bond of the 

parent molecule. It is believed that the resulting molecules are not as toxic as the parent because 

they presumably have lost their mode of action. These transformation products were not 

modeled. 

The acute drinking water concentration in surface water is 200 ppt of deltamethrin, based on 

applications of the chemical to sweet corn. The cancerlchronic drinking water concentration is 

77.1 ppt (based on applications of sweet corn, with the highest application rate). The SCIGROW 

generated EDWC is 200 ppt of deltamethrin, which is recommended for use, both for acute and 

chronic exposures. 

All data requirements for terrestrial food uses are satisfied. However, the registrant submitted a 

supplemental aerobic aquatic metabolism study that yielded two very different half lives. This 

caused the input in the model FIRST to be very high and uncertain. 

A summary table of Tier I modeled drinking water concentrations is provided in Table 1. 

Additional refinements of the assessment can be developed with higher tier analysis, if requested 

by HED. 

PROBLEM FORMULATION 

Table 1. Maximum Tier I Estimated Drinking Water Concentrations (EDWCs) for 

drinking water assessment based on aerial application of deltamethrin. 

This is a Tier I drinking water assessment that uses modeling and 

monitoring data, if available, to estimate the ground water and 

surface water concentrations of pesticides in drinking water 

source water (pre-trea tment) resulting from pesticide use on 

sites that are highly vulnerable. This initial tier screens out 

chemicals wi th 1 ow potential risk and provides estimated exposure 

concentrations for the human health dietary risk assessment. 

DRINKING WATER SOURCE 

(MODEL USED) 

Groundwater (SCIGROW) 

Surface water (FIRST) 

USE (rate modeled) 

Sweet Corn (0.45 Ib a.i./A) 

Sweet Corn (0.45 Ib a.i./A) 

Sweet Corn (0.45 lb a.i.iA) 

MAXIMUM ESTIMATED DRINKING WATER 

CONCENTRATION (EDWC) (ppt) 

Acute and Chronic 

Acute 

Chronic 

200 

200 

77.1 
ANALYSIS 

Use Characterization 

A summary table of all use patterns, highlighting Tier I modeled uses, is illustrated below (Table 

2). The new uses are bolded. 

Table 2. Summary use information for deltamethrin, based on DECIS@ 0.2EC 

Insecticide (EPA Reg. No. 264-1007) and DECISO 1.5EC Insecticide (EPA Reg. No. 

264-1011) 

USE 

( 'otton 

('om. field and 

POP 

Corn, sweet 

Sorghum 

Soybeans 

Sunflowers 

(except 

Califolnia) 

Bulb vegetables 

crop group 3 

(garlic. leeks. 

onion, shallots) 

Cucurbit crop 

group 9 

cantaloupe, 

chayote, Chinese 

waxgourd. citron 

melon, 

cucumber, 

gherkin, gowds, 

Momordica 

species, 

muskmelon, 

pumpkin, 

squash, 

watermelon 

F~uiting 

vegetables crop 

group X 

(eggplant. 

ground-cheny, 

pepinos, peppers. 

tomatillo. 

tomato) 

APP. XETHOD 

Aerial or Ground 

Spray 

Aerial or Ground 

Spray 

Aerial or Ground 

SP~Y 

Aerial or Ground 

Spray 

Aerial or Ground 

Spray 

Aerial or Ground 

Spray 

Aerial or Ground 

Spray 

Aerial or Ground 

SP~Y 

Aerial or Ground 

Spray 

PreHarvest 

Interval 

(days) 

2 1 

2 1 

1 

14 

2 1 

2 1 

I 

3 

1 

labels. 

SINGLE 

APP . RATE 

(lb 

a. i . /A) 

0.030 

0.022 

0.028 

0.022 

0.022 

0.0 18 

0.028 

0.028 

0.028 

mER 

OF APPS. 

10 

5 

16 

2 

-4.5 

-2.5 

4 

6 

h 

SEASONAL 

APP. RATE 

(lb 

a.i./A) 

0.3 

0.095 

0.45 

0.045 

0.1 

0.045 

0.112 

0.168 

0.168 

INTERVAL 

BETWEEN 

ApPS. 

(days) 

5 

2 1 

I 

Not Specified 

Not specified 

Not specified 

5 

3 

5 
Table 2. Summary use information for deltamethrin, based on DECISQ O.2EC 

Insecticide (EPA Reg. No. 264-1007) and DECISQ 1.5EC Insecticide (EPA Reg. No. 
For these labels, the potential application methods are ground and aerial spray (no ULV). Both 

products have the same of formulation (emulsifiable concentrate, EC). The labels impose 

certain restrictions (buffer zones) to protect adjacent bodies of water, accordingly: 25 ft for 

ground applications, 150 ft for aerial applications. 

Table 2. Summary use information for deltamethrin, based on DECISB 0.2EC 

Insecticide (EPA Reg. No. 264-1007) and DECISO 1.5EC Insecticide (EPA Reg. No. 

264-1011) labels. 

The use patterns selected for drinking water modeling were sweet corn (highest application rate 

with smallest application interval) and cucurbit (next highest application rate, and highest PCA 

with smallest interval between applications). Even though cotton had a high application rate, its 

PCA of 0.20 would cause the surface waters to be too low compared to the other two crops. It 

was suspected that sweet corn would yield higher EDWCs than cucurbits. The modeling 

confirmed that sweet corn yielded higher EDWCs. 

Fate and Transport Characterization 

A detailed summary of physicallchemical and environmental fate1 transport properties of 

deltamethrin, including measured parameters, values, data sources, and comments, is included in 

Table 3. 

APP. lrlETHOD 

Aerial or Ground 

Spray 

Aerial or Ground 

Spray 

USE 

I'otne fruits crop 

group I I (apple. 

crabapple, 

loquat. mayhaw. 

pcar, oriental 

pear. quince 

Flax 

preHarvest 

Interval 

(days) 

2 1 

I 

21 

mER 

OF APPS. 

-1.9 

2 

SINGLE 

APP . RATE 

(lb 

a.i./A) 

0.022 

0.02 

'~able 3. Summary of physicaVchemica1 and environmental fate and transport 

properties of deltamethrin. 

SEASO= 

APP. RATE 

(lb 

a.i./A) 

0.042 

0.04 

INTERVAL 

BETWEEN 

APPS . (days) 

7 

7 

PARAWETER 

Chemlcal Name 

Molecular We~ght 

Solublllty (20 C) 

Vapor Pressure (25 C) 

SOURCE 

Deltamethrln 

data sheet 

(web) 

LaskOwskl' 

2002 

Laskowskl, 

2002 

Laskowskl 

2002 

VALUE(S) (units) 

(S) -cyan0 (3- 

phenoxypheny1)methyl 

(1R. 3R) -3- (2.2- 

dlbromoetheny1)-2,2- 

dlmethylcyclopropanecarboxylate 

505 2 

0 000200 mg/L or 

2 00x10 * ppm 

9 32 x 10' mmHq 

COMMENT 

I -$ hnwh >A A ~L,OL 

+ prc _ues a+ -U c 

2/20/07 

Laskowskl, 2002 Rev 

Envlron Contam 

Toxlcol 174 49-170 

Laskowskl, 2002 Rev 

Envlron Contam 

Toxlcol 174 49-170 

Laskowsk~, 2002 Rev 

Envlron Contam 

Toxlcol 174 49-170 
Table 3. Summary of 

properties of deltamethrin. 

PARAMETER 

Henry's Law constant 

pKa I20 C) 

Octanol-Water Partition 

Coefficient 

K, at 20 C) 

Hydrolysis Half-life 

(pH 5, 7, 9; (25 'C)) 

Aqueous Photolysis 

Half-life 

(pH 5) 

Soil Photolysis HalfI ife 

Aerobic Soil Metabolism 

Half-life 

Anaerobic Soil 

Metabolism 

Half-life 

Anaerobic Aquatic 

Metabolism 

Half-life 

Aerobic Aquatic 

Metabolism 

Half -life 

Organic Carbon 

Partition, DELTAMETHRIN 

Coefficient (K:.) 

Soil Partition 

Coefficient, DELTAMETHRIN 

(K,, ) 

Organic Carbon 

Partition, m-phenoxybenzoic Acid 

Coefficient (KO,.) 

Soil Partition 

Coefficient, m-phenoxybenzoic Acid (Kd) 

Organic Carbon 

Part it ion, Br?CA 

Coefficient (KC,,) 

Soil Partition 

Coefficient, Br-CA (Kn) 

environmental fate 

SOURCE 

Laskowski, 

2002 

N A 

Laskowski, 

2002 

MRID 41651038 

MRID 42114818 

MRID 42114819 

MRID 

41677404, 

41677407 

MRID 42114821 

N/A 

MRID 44977005 

MRID 

41651039, 

42475908, 

42976501 

MRID 

41651039, 

42475908, 

42976501 

MRID 44977006 

MRID 44977006 

MRID 42475908 

MRID 42475908 

physicaYchernica1 and 

VALUE(S) (units) 

3.1 x 10~' Atm-m3/mol 

N A 

4.53 

Stable at pH 5 and 7. 

Half-life of 2.5 days at 

pH 9. 

64 and 84 days for benzyl 

and gem labels, 

respectively 

The half life was 9 days, 

but, at the end of the 30 

day study, both the 

irradiated and dark 

control samples had 

around the same amount of 

parent material. 

Dubbs fine SL and Memphis 

SiL, half-lives 11-19 

days; alkaline Arizona SL 

half-life 22 and 26 days 

Alkaline SL half-lives 

32-36 days. 

N A 

System I: 25.9 days 

System 11: 120 days 

392000, 577000, 204000, 

460000 mL/gp, 

3000, 4750. 960, 3790 

(Sic11 mL/g 

288, 190, 105, 50.7 

mL / g,~ 

0.668, 1.54, 2.68, 1.34 

mL/g 

38.2, 46.8, 43.7, 23.0, 

10.1 mL/g-,- 

0'09' O.ll' 0'36' 0.59' 

0.27 mLig 

and transport 

COMraENT 

Estimated from vapor 

pressure and water 

solubility. 

- 

Laskowski, 2002 Rev. 

Environ. Contam. 

Toxicol. 174:49-170 

Relatively stable. 

Considered stable to 

photodegradation on 

soil. 

Systems from the 

Netherlands 

Two silt loam soils, 

a sandy loam, and a 

silt clay 

m-PBA 

m-PBA 

Decamethrinic acid, 

RU 23441 

Decamethrinic acid, 

RU 23441 
When applied to the field, deltamethrin is likely to partition to the soil and organic matter in the 

crops; deltarnethrin appears to bind strongly to soil and organic matter, though binding is not 

instantaneous (~c~~lOO,OOO; immobile). It is not expected to leach into subsurfaces. It may reach 

aquatic environments via spray drift or in runoff events accompanied by erosion. Deltamethn 

appears to be moderately to highly persistent in terrestrial environments (aerobic soil metabolism 

1 1-26 days; terrestrial field dissipation 14-23 1 days). It has the potential to persist in aquatic 

environments, where it may partition with the sediment and has the potential to affect benthic and 

epibenthic organisms (aerobic aquatic metabolism 26-1 20 days; anaerobic soil metabolism 32-36 

days). Due to its low Henry's Law Constant (3.1 x atm-m3/mol), deltamethrin is unlikely to 

volatilize substantially. 

- 

Table 3. Summary of physicaYchernica1 and environmental fate and transport 

properties of deltamethrin. 

Deltamethrin is relatively stable at pH 5 and 7. However, it rapidly degraded (half-life of 2.5 days) 

at an alkaline pH of 9 to form (1R-cis)-3(2,2-dibromoethyl)-2,2-dimethylcyclopropanecarboxylic 

acid (Br2CA, <0.15 ug/L) and 3-phenoxybenzaldehyde (3-PBaldehyde, 3.42 uglL). It does not 

appear to photodegrade substantially in aqueous solutions (half-lives 64, 84 days). Although the 

soil photolysis study gave a half-life of 9 days, considerable degradation was occurring in the dark 

controls as well. 

Based on acceptable aerobic soil metabolism data, deltamethrin in Dubbs fine sandy loam and 

Memphis silt loam soil degraded rapidly (half-life 11-19 days) to form DBVA or Br2CA (40%) and 

C02. Over the 128 day incubation period, 62-77% and 52-60% of the 14c-cyano- and the I4cphenoxy-labelled parent evolved as I4c02. The proposed routes of degradation are ester hydrolysis 

and microbial-mediated mineralization to C02. An additional aerobic soil metabolism study was 

submitted for an alkaline Arizona sandy loam (pH 8.1)' which yielded half-lives of 22 and 26 days. 

For the gem label study, Br2CA was formed, which peaked at 23-26% on day 30 and 14, 

respectively. It is noted that despite the fact that the pH of the latter study was higher, the half-lives 

were higher as well, which was contrary to what was expected from the hydrolysis study. 

P-TER 

Terrestrial Field 

Dissipation 

Half-life 

Biaccumulation in Fish 

(BCF) 

In an anaerobic soil metabolism study, deltarnethrin degraded in an Arizona sandy loam (pH 8.1) 

with a half-life of 32-36 days for the benzyl and gem labels, respectively. For the gem label 

experiment, only 1 metabolite, Br2CA or decamethrinic acid, was found at 49% of the applied 

8 

SOURCE 

MRID 

42137505, 

42773903, 

42114822 

MRID 

43072701, 

43072702, 

41651040 

VALUE(S) (units) 

Louisiana cotton 231 

days, long half-life 

observed, both for the 

bareground and the 

cropped plot. 

California cotton 37 d 

for bareground plot, and 

40 d for cropped plot. 

Minnesota corn 69 d for 

bareground plot, and 14 

days for the cropped 

plot. 

698X whole body, 189X 

edible portion, 

depuration was moderately 

slow (50% between 3-7 

days, and 70-758 after 2 

weeks 

COMMENT 

One separate study 

(41651040) provides 

data on depuration. 
radioactivity by day 30 and remained at about this level on days 59 (52%) and 90 (48%). For the 

benzyl label, the only metabolite identified was mPBAcid, which was only detected in a day 30 

sample, accounting for only 3% of the applied radioactivity. 

In aerobic aquatic metabolism study, consisting of a loam or a sandy loam test systems fi-om the 

Netherlands, the half lives for the whole systems were 26 and 120 days, respectively. The major 

transformation product was the a-R-isomer of deltamethrin, at up to 24% in the SL. An anaerobic 

aquatic metabolism study would provide additional information on the test system completely 

anaerobic. 

In batch equilibrium studies, deltamethrin was found to be immobile (Ko(~>lOO,OOO, FA0 

classification) and had Freundlich &'s of 3,790 for a Mississippi SiClL, 3000 for an Arkansas SiL, 

4750 for a Georgia SiL, and 960 for a Texas SL. IC,'s ranged from 204000 to 577000. Although 

deltamethrin is tightly bound, adsorption is not immediate, because equilibrium times were 4-24 

hours. 

In three terrestrial field dissipation studies parent appeared not to be mobile in soil and degraded in 

1-2 months, except the Louisiana study, where the half-life was almost 8 months. The longer halflife could fall within the range of normal field variability and the Louisiana soil was the lowest in 

organic matter, which would result in the lowest amount of soil binding and soil microbial 

degradation. No clear pattern of degradate formation and decline was seen, possibly because the 

low application rate and 6" sampling intervals resulted in soil dilution, so degradates were not 

detected. 

In fish bioconcentration study, deltamethrin had bioconcentration factors of 189x and 3630x in 

edible and visceral fish tissues, respectively. The whole body BCF of 698x was calculated from 

edible and visceral fish tissue results. The majority of the radioactive residue found in fish was 

parent, accounting for 78 and 83% of the total radioactive residue in edible and visceral fish tissues, 

respectively. No depuration study was done; however, the depuration rate (about 50% between 

days 3-7 and 70-75% after 2 weeks' depuration) from a previous study submitted was considered 

(MRID#4165 10-40, similar BCF's). 

Table 4 provides a summary of the various degradation products formed by each process in the 

studies reviewed. 

Table 4. Summary of degradate formation from degradation of deltamethrin. 

STUDY TYPE 

Hydrolysis 

Aqueous Photolysis 

Soil Photolysis 

Aerobic Soil Metabolism 

SOURCE 

MRID 41651038 

MRID 42114818 

MRID 42114819 

MRID 41677404, 

41677407 

DEGRADATE and MAXIMUM CONCENTRATION 

Br,CA (% applied) 

~0.15 ug/L 

cis-Br-CA at day 

2 1 

trans-Br,CA 53.9% 

at 30 days 

23-268 at 14-30 

days 

mPBA (% applied) 

- 

11% at day 21 

- 

- 

mPBaldehyde 

(% applied) 

3.37 ug/L at 30 

days (app. rate 

10.0 ug/L) 

- 

a-R-deltamethrin 

- 
It appears that m-PBA and m-PBaldehyde are not very persistent in the environment. However 

Br2CA appears to persist much more than the former compounds. It was observed in laboratory 

studies and in the field. These degradates are the result of the ester rupture in the parent molecule. 

Another transformation product that was observed in various of the studies (soil photolysis and 

aerobic aquatic metabolism) was the a-R-deltarnethrin, an isomer of deltamethn. 

Table 4. Summary of degradate formation from degradation of deltamethrin. 

Based on batch equilibrium data, a major degradate, Br2CA or decamethrinic acid, appeared to be 

mobile (Freundlich &S 4, and IG~~'s=10.1-46.8, FA0 classification) in 5 soils. In addition, for the 

degradate mPBA, &'s were in the range of 0.7-2.7 while the Koc's were in the range of 5 1-288 

(mobile to moderately mobile, FA0 classification). Of these degradates, Br2CA has the potential to 

leach to subsurfaces, or to reach adjacent bodies of water via runoff events, most likely dissolved in 

the water. 

Drinking Water Exposure Modeling 

SOURCE 

MRID 42114821 

MRID 44977005 

MRID 42137505, 

42773903, 

42114822 

STUDY TYPE 

Anaerobic Soil 

Metabolism 

Aerobic Aquatic 

Metabolism 

Terrestrial Field 

Dissipation 

Models (Ref: 1) 

SCIGROW (v 2.3, 8/5/03) (Screening Concentration in Ground Water) is a regression model 

used as a screening tool to estimate pesticide concentrations found in ground water used as 

drinking water. SCIGROW was developed by fitting a linear model to groundwater 

concentrations with the Relative Index of Leaching Potential (RILP) as the independent 

variable. Groundwater concentrations were taken from 90-day average high concentrations 

from Prospective Ground Water studies; the RILP is a hnction of aerobic soil metabolism 

and the soil-water partition coefficient. The output of SCIGROW represents the 

concentrations that might be expected in shallow unconfined aquifers under sandy soils, 

which is representative of the ground water most vulnerable to pesticide contamination likely 

to serve as a drinking water source. (Ref. 2) 

DEGRADATE and MAXIMUU CONCENTRATION 

FIRST (v 1.1 .O, 1211 8/07) (FQPA Index Reservoir Screening Tool) is a metarnodel of PRZM 

and EXAMS used as a screening tool to estimate pesticide concentrations found in surface 

water used as drinking water. FIRST was developed by making multiple runs of PRZM 

using varying sorption coefficients and determining the concentration in the EXAMS index 

reservoir scenario after a two-inch single storm event. (The Index Reservoir is a standard 

water body used by the Office of Pesticide Programs to assess drinking water exposure 

mPBaldehyde 

(% applied) 

- 

a-R-isomer of 

deltamethrin 24% 

at day 14 

- 

Br2CA (% applied) 

498 by day 30, 

and remained at 

that level 

through day 90 

- 

0.5 ppb at 4 

days 

mPBA (% applied) 

- 

- 

- 
(Office of Pesticide Programs, 2002). It is based on a real reservoir (albeit not currently in 

active use as a drinking water supply), Shipman City Lake in Illinois, that is known to be 

vulnerable to pesticide contamination.) The single runoff event moves a maximum of 8% of 

the applied pesticide into the reservoir. This amount can be reduced by degradation or effects 

of binding to soil in the field. Additionally, FIRST can account for spray drift and adjusts for 

the area within a watershed that is planted with the modeled crop (Percent Cropped Area). 

Spray drift (modeled as direct deposition of the pesticide into the reservoir) is assumed to be 

16% of the applied active ingredient for aerial application, 6.3% for orchard air blast 

application, and 6.4% for other ground spray application. Despite being a single event model, 

FIRST can account for spray drift from multiple applications. The default agricultural 

Percent Cropped Area (PCA) is 87%. The PRZM scenario used for FIRST development was 

among the most vulnerable, and thus resulting surface water concentrations represent the 

upper bound values on the concentrations that might be found in drinking water from the use 

of a pesticide. (Ref. 3 and 4) 

For volatile and semi-volatile compounds, Tier I modeling will tend to over-estimate surface 

water EDWCs because there are no parameters in FIRST that explicitly take into account 

volatility (i.e., no vapor pressure or Henry's Law Constant inputs). Therefore, in reality, 

more of the compound will be volatilizing than Tier I can account for. If drinking water 

levels of concern are exceeded for over-estimated Tier I surface water EDWCs, Tier I1 

modeling will be able to refine these EDWCs by including volatility, Henry's Law, diffusion 

in air, and enthalpy considerations. Since SCIGROW is a regression model developed from 

actual pesticide data with a range of volatilities, systematic conclusions cannot be drawn 

about over or underestimation of groundwater EDWCs at Tier I. 

Modeling Approach and Input Parameters 

Tables 5 and 6 present modeling parameter input values for SCIGROW and FIRST, respectively, 

based on the current input parameter guidance (Re$ 5). 

For SCIGROW, the median organic carbon partition coefficient (Koc, of four values), and the 

mean (of four values) aerobic soil metabolism half-life were used. In FIRST, the parameters 

selected were as follows: the lowest non-sand organic carbon partition coefficient was utilized (it 

was the lowest of all the values). The Koc model was utilized as per SAP recommendation. For 

the aerobic soil metabolism and the aerobic aquatic metabolism, the 9oth percentile of the upper 

confidence bound on the mean of four and two, respectively, were utilized. The hydrolysis at pH 

7 was stable while for the aqueous photolysis, the maximum value was used. Two PCAs were 

used because modeling of sweet corn and cucurbits were performed. These were the crops 

suspected to be the ones with the highest EDWCs. 

The only transformation product included in the modeling is the a-R-deltamethrin in the aerobic 

aquatic metabolism. The half-lives derived in the study included the transformation product 

because it is only an isomer of deltamethrin. Other degradates were not included. 
 able 6. FIRST (v.1.1.0) input parameter values for deltarnethrin use on sweet corn1. 

Table 5. SCI-GROW (v.2.3) input parameter values for deltamethrin use on sweet corn'. 

PARAMETER (units) 

Maximum Application Rate (lb 

a. i . /A) 

Number of Applications per 

Year 

Organic Carbon Partition 

Coefficient (K. ; mL/g) 

Aerobic Soil Metabolism Halflife (days) 

PARAMETER (units ) 

1 Parameters are selected as per Guidance for Selecting Input Parameters in Modeling the Environmental Fate and 

Transport of Pesticides; Version 11, February 28, 2002. 

SOURCE 

Proposed label 

Proposed label 

MRID 41651039, 

42475908, 

42976501 

MRID 

41677407 

VALve(S) 

0.028 

16 

426000 

19.5 

Application Rate (lb a.i./A) 0.028 

COMMENT 

- 

Represents the worst case scenario 

for sweet corn. 

Represents the median value of four 

values ranging from 204000 to 577000 

mL/g for the parent compound. 

Represents the average value of four 

available for the parent compound, 

ranging from 11 to 26 days. 

I I I 

VALUE ( S ) SOURCE 

Proposed label 

Number of Applications 16, 6 

COMMENT 

I I I 

Proposed label Sweet corn, cucurbit 

Interval between Applications 

(days 

I I I 

Percent Cropped Area 

(decimal ) 

I 

1, 3 

Soil Partition Coefficient 

iK,; irnL/g) or KO, (mL/go,) ) 

Wetted in? I No 1 Proposed label I 

0.46, 

0.87 

Aerobic Soil Metabolism Halflife (days) 

Proposed label 

204000 

Method of Application I Asyriay 1 Proposed label I 

Sweet corn, cucurblt 

Proposed label 

24.7 

Depth of Incorporation 

( inches 

Sweet corn, cucurblt 

MRID 41651039, 

42475908, 

42976501 

Aerobic Aquatlc Metabolism 

Half-life (days) 

Represents the lowest non-sand K-, 

value among four values ranglng from 

204000 to 577000 mL/g. The Kc model 

was utilized as per SAP 

MRID 41677404, 

41677407 

0 

Solubility in Water @ 20 kc, 

unbuffered (mg/L or ppm) 

Hydrolysis Half-life @ pH 7 

(days ) 

Aquatic Photolysis Half-life 

@ pH 7 (days) 

recommendation. 

Represents the 90"' percentile of the 

upper confidence bound on the mean of 

four half-life values, mean = 19.5 

days; standard deviation = 6.35 days 

- 

upper confidence bound on the mean of 

two half-life values, mean = 73.0; 

MRID 41651038 Stable. 

Proposed label 

0.0000200 

mg/L or 

2.00~10-" 

- 

- 

I 

MRID 42114818 

Laskowski, 

2002 

Maximum value. 

Laskowski, 2002 Rev. Environ. Contam. 

Toxicol. 174:49-170 
The PCAs used were 0.46 for sweet corn (corresponds to corn), and 0.87 for cucurbits. Two 

values were used because two crops were suspected to yield the highest EDWCs. Options for 

Tier 1 are national scale cotton, wheat, corn, soybeans, or default; regional PCAs are a Tier I1 tool 

intended for refined assessment. (Ref: 6) 

Table 6. FIRST (v.1.1.0) input parameter values for deltamethrin use on sweet corn'. 

Modeling Results 

PARAlaeTER (unit 8) 

Table 7 is a summary of the modeling results for all model runs. 

I Parameters are selected as per Guidance for Selecting Input Parameters in Modeling the Environmental Fate and 

Transport of Pesticides; Version 11, February 28,2002 

VALUE ( S ) 

SCIGROW concentration (ppb) represents the groundwater concentration that might be 

expected in shallow unconfined aquifers under sandy soils. Output is used,for both acute 

and chronic endpoints. 

SOURCE I COMMENT 

Table 7. Maximum Tier I Estimated Drinking Water Concentrations (EDWCs) for 

drinking water risk assessment based on aerial application of deltamethrin. 

FIRST concentrations (ppb) represent untreated su~face water concentrations. 

The one-in-10-year peak day concentration is used,for acute endpoints and the one-in-10- 

year annual average concentration is used,for chronic endpoints. 

The estimated concentrations provided in this assessment are conservative estimates of' 

concentrations in drinking water. Ifdietary risks require refinement, higher tiered cropspecific and location-specific models and modeling scenarios can be used. 

DRINKING WATER SOURCE 

(MODEL USED) 

Groundwater (SCIGROW) 

Surface water (FIRST) 

Monitoring Data 

USE (rate modeled) 

Sweet Corn (0.45 lb 

a.i. /A) 

Sweet Corn (0.45 lb 

a. i . /A) 

Sweet Corn (0.45 lb a. i . /A) 

MAXIMUM ESTIMATED DRINKING WATER 

CONCENTRATION (EDWC) (ppt) 

Monitoring data provide different kinds of information than 

modeling estimates. For example, monitoring data consist of 

actual information from the field, reflecting current use pattern 

and usually underestimating frequency of occurrence. Moni toring 

data does not always include peak values, and inputs for 

monitoring cannot be adjusted as modeled ones can. In addition, 

monitoring is often conducted for purposes other than 

characterizing exposure from a particular pesticide, and as a 

Acute and 

Chronic 

Acute 

Chronic 

200 

200 

77.1 
consequence is used to complement modeling rather than to refine 

i t . In general, a useful interpretation of moni toring values 

requires in-depth assessment of the data, which is beyond the 

scope of a Tier I assessment. 

The NAWQA database was searched and no data were observed. 

Drinking Water Treatment 

It is likely that primary treatment may reduce the levels of deltamethn due to its tendency to 

bind. However, there is no information available at this time to determine the levels of 

reduction. Furthermore, the softening of drinking water will generally result in an increase in 

pH. Deltamethrin is more susceptible to hydrolysis under alkaline conditions; therefore, 

softening may result in increased dissipation from hydrolysis. (Ref: 8) 

CONCLUSIONS 

The acute drinking water concentration in surface water is 200 ppt of deltamethrin, based on 

applications of the chemical to sweet corn. The cancedchronic drinking water concentration is 

77.1 ppt (based on applications of sweet corn, with the highest application rate). The SCIGROW 

generated EDWC is 200 ppt of deltamethrin, which is recommended for use, both for acute and 

chronic exposure. 

No degradates were assessed (except for the transformation product a-R-deltamethrin). It was 

assumed that deltamethrin was applied to sweet corn at the maximum application rate for 26 

consecutive days (the minimum interval between applications). It appears that this scenario is 

unlikely. The peak surface water drinking water concentration and the ground drinking water 

concentration were limited by the solubility limit of deltamethrin. The environmental fate data 

base for deltamethrin was complete and consisted of a number of studies, making this assessment 

strong. The weakness of the data base is the aerobic aquatic metabolism study, which yielded 

two very different half lives. This study was considered supplemental, with various deficiencies. 

In addition, it was noted that one terrestrial field dissipation study yielded also a very different 

half-life (around 8 months vs. around 12 months for all the other studies). 

Despite the weaknesses in the data, the assessment is conservative. The input parameter for the 

aerobic aquatic metabolism was a high value, and made the assessment more conservative. 

A more definitive assessment can be made if a Tier I1 surface waters assessment is performed. 
APPENDIX 

Nomenclature: 

Deltamethrin = CAS name = (S)-cyano(3-phenoxyphenyl)methy1(1R,3R)-3-(2,2- 

dibromoethenyl)-2,2-dimethylcyclopropanecarboxylate 

IUPAC names = (9-a-cyano-3-phenoxybenzyl (lR,3R)-3-(2,2-dibromoviny1)-2,2- 

dimethylcyclopropanecarboxylate or (5')-a-cyano-3-phenoxybenzyl(1 R)-cis-3-(2,2- 

dibromovinyl)-2,2-dimethylcyclopropanecarboxylate 

a-R-isomer of deltamethrin = [l R-[I -a-(R*),3-a-]]-3-(2,2-Dibromovinyl)-2,2-dimethylcyclopropanecarboxylic acid, cyano (3-phenoxypheny1)methyl ester 

3-PBA = 3-phenoxybenzoic acid 

RU 53605 = [ 1 R-[ 1 -a-(S*),3-a-]I-3-(2,2-Dibromoviny1)-2 dimethyl-cyclopropanecarboxylic 

acid, cyano[3-(4-hydroxyphenoxy) phenyll-methyl ester 

Transformation Product of hydrolysis, (1R-cis)-3(2,2-dibromoethy1)-2,2-dimethylcyclopropanecarboxylic acid (one form of BrzCA) 

Transformation Product of aerobic soil metabolism, DBVA = (3-(2,2-dibromoviny1)-2,2- 

dimethylcyclopropanecarboxylic acid (one form of Br2CA) 
Deltamethrin, CAS No. 52918-63-5 

Br (S)-alcohol (1~) -cs-ac i d !,' 

Br-C 0 

m-PBA, m-phenoxybenzoic acid, CAS No. 3739-38-6 

0 

m-PBaldehyde, m-phenoxybenzaldehyde, CAS No. 39515-51-0 

0 

H 

Decamethrinic acid, Br2CA, CAS No. 53179-78-5 
FIRST and SCIGROW model output files: 

RUN No. 1 FOR Deltamethrin ON Sweet Corn * INPUT VALUES * .................................................................... 

RATE (#/AC) No.APPS & SOIL SOLUBIL APPL TYPE %CROPPED INCORP 

ONE (MULT ) INTERVAL Koc (PPTr) (%DRIFT) AREA (IN) .................................................................... 

.028( .366) 16 1 204000.0 200.0 AERIAL(16.0) 46.0 .O 

FIELD AND RESERVOIR HALFLIFE VALUES (DAYS) .................................................................... 

METABOLIC DAYS UNTIL HYDROLYSIS PHOTOLYSIS METABOLIC COMBINED 

(FIELD) RAIN/RUNOFF (RESERVOIR) (RES.-EFF) (RESER.) (RESER.) .................................................................... 

24.70 2 N/ A 84.00-10416.00 217.70 213.24 

UNTREATED WATER CONC (NANOGRAMS/LITER (PPTr)) Ver 1.1.0 DEC 12, 2005 .................................................................... 

PEAK DAY (ACUTE ) ANNUAL AVERAGE (CHRONIC) 

CONCENTRATION CONCENTRATION .................................................................... 

200.000 77.120 

RUN No. 2 FOR Deltamethrin ON Cucurbit * INPUT VALUES * .................................................................... 

RATE (#/AC) No.APPS & SOIL SOLUBIL APPL TYPE %CROPPED INCORP 

ONE (MULT) INTERVAL Koc (PPTr) (%DRIFT) AREA (IN) .................................................................... 

.028( .138) 6 3 204000.0 200.0 AERIAL(16.0) 87.0 .O 

FIELD AND RESERVOIR HALFLIFE VALUES (DAYS) .................................................................... 

METABOLIC DAYS UNTIL HYDROLYSIS PHOTOLYSIS METABOLIC COMBINED 

(FIELD) RAIN/RUNOFF (RESERVOIR) (RES.-EFF) (RESER.) (RESER.) .................................................................... 

24.70 2 N/ A 84.00-10416.00 217.70 213.24 

UNTREATED WATER CONC (NANOGRAMS/LITER (PPTr)) Ver 1.1.0 DEC 12, 2005 .................................................................... 

PEAK DAY (ACUTE) ANNUAL AVERAGE (CHRONIC) 

CONCENTRATION CONCENTRATION .................................................................... 

200.000 54.779 
SCIGROW 

VERSION 2.3 

ENVIRONMENTAL FATE AND EFFECTS DIVISION 

OFFICE OF PESTICIDE PROGRAMS 

U.S. ENVIRONMENTAL PROTECTION AGENCY 

SCREENING MODEL 

FOR AQUATIC PESTICIDE EXPOSURE 

SciGrow version 2.3 

chemica1:Deltamethrin 

time is 2/21/2007 12: 9:17 

Application Number of Total Use Koc Soil Aerobic 

rate (lb/acre) applications (lb/acre/yr) (ml/g) metabolism (days) 

groundwater screening cond (ppb) = 2.69E-03* 

"Estimated concentrations of chemicals with Koc values greater than 9995 ml/g 

are beyond the scope of the regression data used in SCI-GROW development. 

If there are concerns for such chemicals, a higher tier groundwater exposure 

assessment should be considered, regardless of the concentration returned 

by SCI-GROW. ........................................................................ 

References: 

1. Policy Establishing Current Versions of Exposure Models and 

~esponsibility for Model Maintenance (11/06/2002) 

2. SCIGROW: Users Manual (11/01/2001, revised 08/23/2002) 

3. FIRST Users Manual (08/01/2001) 

4. FIRST: A Screening Model to Estimate Pesticide Concentrations in 

Drinking Water (05/01/2001) 

5. Guidance for Selecting Input Parameters in Modeling the ~nvironmental 

Fate and Transport of Pesticides, Version I1 (02/28/2002) 

6. Use of the Index Reservoir and Percent Crop Area in EFED Drinking Water 

Assessments (12/01/1999) 

7. Golf Course Adjustment Factors for Simulated Aquatic Exposure 

Concentrations (06/01/2005) 

8. The Incorporation of Water Treatment Effects on Pesticide Removal and 

Transformations in Food Quality Protection Act (FQPA) Drinking Water 

Assessments (10/25/2001) 

9. Food and Agriculture Organization of the United Nations. FA0 PESTICIDE 

DISPOSAL SERIES 8. Assessing Soil Contamination: A Reference Manual. 

Appendix 2. Parameters of pesticides that influence processes in the 

soil. Editorial Group, FA0 Information Division: Rome, 2000. 

~ttp: www. tac).org DOCPEP 00, ir5 /LIE A25 7OEI)L .nrn ........................................................................